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Issue 10s ， 2016
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Multiple-slit streak tube imaging lidar
Abstract：In order to effectively improve the imaging property of multiple-slit streak tube, an experimental platform for Multiple-Slit Streak Tube Laser Imaging Lidar(MS-STIL) was established with a domestically-made optical taper and streak tube. The fiber arrangements of the optical taper were converted from 128×32 at fore-end to 8×512 at back-end, thus changing the planar image to 8 stripes image and enabling the detector to achieve effective detection of field of view. The laser wavelength of this system is 532 nm, with an imaging pixel element of 128×32 and a spatial resolution lower than 0.3 mrad, and all-weather operations can be achieved. On the platform, imaging experiments for out-field building targets were performed, from which the non-scanning image of 1.7 km target and the scanning image of 720 m target were obtained respectively. The imaging results indicated that the proposed MS-STIL can capture the laser images of long-distance targets, as the intensity image can well display the areas where the building target is located, with clear outline; the distance image can effectively divide the areas with different distances, with relatively high distance resolution.Keywords：laser radar;laser maging lidar;multiple-slit streak tube;flash focal-plane- 54
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Published：2020-08-13 -
Infrared single photon detection system based on parallel avalanche photodiode array
Abstract：To overcome the after-pulse effect of InGaAs/InP APD single-photon detector, reduce the dead time of APD devices, and improve the operating frequency and detection efficiency of infrared single-photon detector, a parallel APD array was adopted to convert the single-photon signal into the avalanche signal. Through a DC bias voltage circuit, the parallel APD array can operate in the Geiger Mode. By virtue of the high-speed pulse gating sequence signal circuit and multi-channel optical switch, the parallel APD array was able to achieve the sequential switching function. The avalanche signal output from the parallel APD array, after being processed by low-pass filtering and broadband of signal detection circuit, was converted into digital signal through the signal-simulation digital conversion circuit; and then through discrimination detection and counting by the signal processing circuit, digital signals of different types can be output. The results show that when the pulse gating signal frequency is 1.6 GHz, the repetition frequency of the infrared single-photon detection system with parallel APD array of 8 channels is 1000 MHz, with a dark count rate of 5.92×10-5 and a detection efficiency of 10.0%. The infrared single-photon detection system with parallel APD array can dramatically reduce the dead time, and effectively improve the operating frequency and repetition count rate of single-photon detection.Keywords：avalanche photodiode;infrared single-photon detector;after-pulse effect;parallel array- 82
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Published：2020-08-13 -
Preparation and properties of titanium clad steel plate with interlayer in laser cladding
Abstract：In consideration of the weak bonding property between the cladding and base course during preparation of the titanium/steel sandwich plate through laser cladding, the method of adding a certain proportion of Ti-Fe mixed powder was adopted to improve the preparation quality of the sandwich plate. The optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were employed to analyze the structure and composition of the test pieces with Ti content of 0%, 5% and 11.5%. Then tension-shear performance tests were performed and the morphologies of the shear fracture were observed. The test result indicates that both of the interlayer materials and substrate can achieve the metallurgical bonding. When the interlayer titanium content less than 11.2wt%, the titanium cladding layer can be securely bonded with the interlayer, at the top of which was pure titanium equiaxed crystal and the bottom part was cellular (β-Ti+TiFe) eutectic structure. The hardness of the titanium cladding layer is 2-3 times greater than that of commercial pure titanium. When the interlayer titanium content is 5.5wt%, the bonding intensity between the titanium cladding layer and the interlayer is 14 MPa as a maximum. The difference of shear strength in the sandwich plate mainly relies on crystal dimensions and the shear fracture is intergranular brittle fracture. The research results provide significant theoretical and experimental basis for laser cladding preparation of titanium/steel sandwich plate.Keywords：Laser cladding;titanium/steel sandwich plate;interlayer;microstructure;mechanical property- 45
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Published：2020-08-13 -
High accuracy detection algorithm for eccentric signal of grinding wheel
Abstract：To improve the measurement precision of eccentricity signal during installation of diamond grinding wheel under high-precision machining, a kind of model based on single-point measurement of grinding wheel eccentricity signal by laser displacement sensor was set up based on the non-contact measurement. Then a high-precision approach algorithm for grinding wheel eccentricity put forward based on minimization of the rotary contour roundness error. The algorithm can fast restore eccentric distance and direction of the grinding wheel through coordinate transformation, normalization processing and weight correction. Finally, based on position relationship between the sensor and principal axis of the grinder during signal acquisition, an analytic formula for ideal grinding wheel eccentricity signal is given, and a simulation experiment for eccentricity detection of grinding wheel was also carried out. The simulation results indicate that this method can achieve high-precision detection of grinding wheel eccentricity, with high convergence rate and a relative detection error within 6%. The analysis on the experimental measurement data shows that stabilization precision of measurement repeatability by using the algorithm to restore eccentricity and eccentric angle of the grinding wheel remains within 0.005 mm and 0.02 rad respectively, which meets the detection precision requirement for grinding wheel eccentricity during its high-precision grinding operation.Keywords：non-contact measurement;eccentricity detection;normalization;fast approach;grinding wheel installation- 55
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Published：2020-08-13 -
Holographic measurement of atomization characteristics of fan-shaped air-blast atomization SNCR nozzle
Abstract：An off-axis pulsed particle holographic system was established based on micro particle holography, for measuring the spray characteristics such as particle size and distribution of the fan-shaped air-blast atomization nozzle. The principle and composition of the optical holographic system was introduced firstly, by which the atomization field hologram for the Φ70 mm circular area was recorded. After collection of the hologram reproduction and image processing, the Sauter Mean Diameter (SMD) and the occupation ratio of droplets with different diameters were acquired. The experimental results show that droplet size D32 of the atomization field is between 50 μm and 170 μm, with larger droplet size in middle part and gradually diminishing towards the edge. It is an ideal atomization mode for the SNCR nozzle; where there is a fixed liquid flow, the atomization droplet size D32 will decrease as the gas loss rate goes up. It indicates that the main evaluation data for atomization property of the SNCR nozzle is of great guiding significance to the theoretical research on control technology and atomization mechanism of the nozzle in practical operation.Keywords：holographic measurement;fan-shaped air-blast atomization nozzle;atomization property;pulse holography;SNCR;flue gas denitrification- 64
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Published：2020-08-13 -
High-power narrow linewidth microsecond pulse 1064 nm ring laser
Abstract：In order to realize high-power quasi-continuous wave sodium beacon laser with high-efficiency sum frequency, 1064 nm ring-cavity laser of high-power narrow-linewidth microsecond pulse which restrains relaxation oscillation was studied. A thermally near unstable cavity was adoped to optimize curvature of three-scope ring endoscope, inserting an etalon in cavity to narrow laser linewidth. Using a 1064 nm thin-film polaroid as output mirror of ring cavity and a half wave plate, a continuous adjustable output coupling ratio was realized. Under the condition of 808 nm semiconductor laser with pumping power of 175 W, 1 064 nm laser output with output power of 42 W, beam quality factor M2=1.26, linewidth of 0.2 GHz was acquired. Its repetition frequency is 800 Hz and pulse width is 100 μs. The relaxation oscillation of laser pulse was effectively suppressed by inserting 1 064 nm frequency-doubling crystal KTiOPO4 in cavity and using second harmonic effect to rapid weaken high-strength spike pulse sequence.The whole system is pretty simple, which provides the practical and effective technical method for obtaining 1064 nm laser of quasi-continuous wave without relaxation oscillation.Keywords：pulse laser;ring-cavity laser;sodium beacon laser;relaxation oscillation;thermally near unstable cavity;KTiOPO4(KTP)- 82
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Published：2020-08-13 -
Influence of Gaussian jitter on thermal damage in aluminum and titanium alloys incluced by high-power CW fiber laser
Abstract：In order to analysis the interaction between the metal plate and high-power CW fiber-laser beam through a long distance transmission, the laser beam jitter induced by the interaction on a high-power array detector with a high power CW fiber laser at different distances was researched experimentally, where the effect of the laser jitter on the damage of the metal plate was analyzed. The jitter and jitter-free models of the far-field damage of metal plates were built in simulation, and the temperature distribution between the jitter and jitter-free mode is compared by the finite element method. It shows that the jitter amplitude grows gradually with the increase of the transmission distance. At the same transmission path, the deviation along horizontal direction X is lower than that in the vertical direction Y. Due to laser spot jitter, the far-field spot presents elliptical distribution, which leads to elliptical damage morphology on the plate and a beam deflection about 20 °. When the spot centroid offset is greater than the spot radius, the maximum temperature drop rate of the metal plate reaches more than 10% by the original position. The experiments and simulations demonstrate that the high-power CW laser beam quality declined after a long distance transmission which may reduce the energy coupling efficiency and affect the laser material interaction efficiency.- 51
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Published：2020-08-13 -
Abnormal behaviors of photovoltaic HgCdTe detectors under intense pulse laser
Abstract：The response behavior of photovoltaic detector under the laser irradiation with high-fluence pulse was researched experimentally, by using a short-wave infrared photovoltaic HgCdTe single-element detector with zero bias voltage under room temperature. Taking a 2.0 μm fiber laser with modulation frequency of 1000 Hz as the signal light in normal working state, the detector was interacted with 2 μm wave-band pulsed laser of different energies. Experimental results indicate that when the pulsed laser energy density on the photosensitive surface of detector reaches 0.1 J/cm2, detector has two abnormal response behaviors named after signal suppression and negative baseline respectively. In the short time after pulsed laser irradiation ends, response amplitude to signal light decreases temporarily and the decrease degree with the maximum value of 100% is positively related to laser intensity. At the same time, the base line of detector response waveform decreases from zero to negative value and the decrease amplitude is positively related to laser intensity. Then, the response amplitude of detector to signal light and baseline of response waveform gradually recover to the level before irradiation within 10 ms to 100 ms. The signal suppression effect is caused by the temperature increase in photosensitive area, and the negtive baseline is correlated with thermal effect and structure of the detector.Keywords：laser irradiation effect;pulsed laser;HgCdTe;photovoltaic detector;abnormal behavior;signal supression effect;negative baseline- 53
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Published：2020-08-13 -
Spot modification in laser triangulation displacement measurement
Abstract：The mechanism of the dissymmetric light spot shape in the laser triangulation was analyzed, and the mass center of the spot was corrected effectively by optical system modeling. Firstly, Zemax software was used for analog simulation of the optical system to acquire the minimum aberration imaging point of diffuse reflection spot. Secondly, a virtual optical imaging system model was established according to the coordinate data of imaging points in the built three dimensional space coordinate system, thus the transformation formulas of pixel intensities between actual optical imaging system and virtual optical imaging model were deduced through ray tracing for calculation of the corresponding correction coefficient. Finally, the light spot center was obtained by centroid method after the sampling data of light spot was corrected by the calculated coefficients. Experiment result indicates that this method can decrease the repeatability error of light spot center positioning caused by the external environment to 50% of the original one, with the overall non-linear error of ranging system reaches ±0.125%. The proposed method can effectively decreased the error caused by external environment change and improved stability and anti-disturbance capacity without basic change of the measuring speed of ranging system.Keywords：laser triangulation ranging;centroid method;focus point modeling;ray tracing- 55
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Published：2020-08-13 -
Effects of water-heat treatment sensitivity and temperature-independent of plastic optical fiber sensor
Abstract：In order to acquire U-shaped plastic optical fiber sensor with high sensitivity and independent temperature, the grinding method was used to prepare D-shaped optical fiber, then heating-cooling circulating treatment in water bath was implemented to D-shape area. Afterwards the optical fiber was made into U-shape sensor. The influence of U-shape area with different diameters and curvatures on sensor sensitivity was analyzed, as well as the dependence of plastic optical fiber on temperature in glucose solutions with and without the heating-cooling circulating treatment. The results show that the sensor sensitivity is controlled by the diameter and curvature of U-shaped region. The maximum sensitivity of the sensor in glucose solution (25℃) reaches 0.017/g·(100 mL)-1 when U-area diameter and curvature are 1 500 μm and 0.025 mm-1. In addition, the Maximum Relative Error(MRE) of the Relative Change of Transmitted Light Intensity(RCTLI) of the sensor in glucose solution decreases from 140.1% at 25℃ to 9.7% at 65℃, which indicates that water heating-cooling circulating treatment can relieve the temperature sensitivity of the plastic optical fiber.Keywords：plastic optical fiber;U-shape sensor;water-heat treatment;aging treatment of distilled water;sensitivity;temperature independence;optical transmission- 55
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Published：2020-08-13 -
Fast recognition of camouflage target by spectrum detection technology
Abstract：In order to realize fast recognition of camouflage targets in the modern battlefield, a fast target recognition system was designed based on spectrum detection. The principle of target recognition base on spectrum detection technology derived for analyzing the generation mechanism of substance spectrum and the difference of spectral lines among various targets. Then a fast target recognition system was established with an improved spectrum detection module and optical filters in different wavebands to identify spectral lines of camouflage target, thus decreasing the amount of generated data for calculation and enhancing the real-time performance of target recognition. The experiment results indicate that the proposed detection technology can recognize the camouflage targets with accuracy above 90%. After adding the optical filters, the processing time is 1/3 of that of the conventional system, which realizes the improvement of real-time performance of the system. The target recognition method based on spectrum detection technology can effectively recognize camouflage target under certain real-time requirement, thus having a great potential in certain military fields.Keywords：spectrum detection;camouflage target;target recognition;optical filter;real-time performance- 78
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Published：2020-08-13 -
Design of non-polarization long-wave-pass edge filter
Abstract：An oblique incidence on the conventional film interference cut-off filter will result in an obvious phenomenon of wavelength separation due to its P and S polarized lights, thus leading to serious polarization dependent loss in the cut-off band. Based on two ordinary film materials TiO2 and SiO2, this paper designs a depolarized stack structure for the long wave-pass interference cut-off filter through adding low refractive material with different thicknesses as matching layers above and under the high refractive layer. The algorithm for stack calculation was proposed and operated on a computer, thereby obtaining an optimal stack structure of ((H/2)4L2H4L(H/2))15. The stack enables the cut-off filter to achieve a polarization wavelength separation less than 2 nm in the cut-off sideband and a bandpass transmittance over 92% when the filter is in the position of 3 dB with an oblique incidence angel of 45°. Using the algorithm and the stack, the depolarized long-wave-pass interference edge filter can be easily designed and fabricated.Keywords：thin film;edge filter;long-wave-pass;non-polarization- 69
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Published：2020-08-13 -
Chopper stable speed control system based on PID in NIR spectrometer
Abstract：In order to reduce the frequency fluctuation of modulating signals of the raster scanning spectrometer modulator and improve the spectrum detection precision, a high-performance stable speed control system based on proportional-integral-derivative (PID) algorithm was proposed. The control system of the modulator mainly comprised the H-bridge drive circuit, optocoupler, voltage comparator and single-chip-machine microcontroller. The modulating frequency of the modulator was monitored in real time through single-chip-machine, optocoupler and voltage comparator. By using the difference between average value of the measuring frequencies corresponding to all teeth in the modulating disk and the target frequency as the frequency error, the control output was calculated via the PID algorithm, regulating the timing counter of the single-chip machine to output the pulse width modulation (PWM) signals. The H-bridge circuit drove the DC motor, ensuring the stability of the modulating frequency. It is verified that the modulating frequency fluctuation decreasing from 5.67 Hz to 3.01 Hz compared with the phase-locked loop control system of spectrometer modulator, and the spectral Signal-to-Noise Ratio(SNR) is effectively improved from 1 885 to 4 156. The proposed PID control system can enhanced the SNR of the spectrometer with considerable stability.Keywords：near infrared spectrometer;modulator;modulation frequency;steady speed;PID algorithm;DC motor- 58
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Published：2020-08-13 -
Response of laser shock on high speed steel W9Cr3Mo4V
Abstract：The response properties of laser shock on high-speed steel W9Mo3Cr4V were studied experimentally by adopting different laser energies and shock frequencies. The experiment result indicates that the area under laser shock produces round pits, depth of which will increase as the laser energy and shock frequency increase. The surface residual stress exists in the surface of the impacted area under laser shock, and such residual stress increases as the laser energy and shock frequency increase; but the maximum residual stress will approach saturation after three times of shock, without obvious stress amplification. The nano-hardness and elasticity modulus in the pimple center increase as the laser energy and shock frequency increase, and compared with the matrix, the maximum increases for the nano-hardness and elasticity modulus are respectively 15.04% and 14.35%. Impacted by the force effect of shock wave along the depth direction, the grain size in laser shock impacted area is approximately 10 μm as a minimum, which increases with the increase of distance. According to the variation of grain sizes, the impacted area can be divided into 5 layers:severe plastic deformation layer, plastic deformation layer, slight plastic deformation layer, transition layer and the matrix. Laser chock can effectively refine surface layer grain of the high-speed steel W9Cr3Mo4V and improve the mechanical property in surface layer of the impacted area, thus providing guidance for the fabrication of laser shock strengthening high-speed steel tools.Keywords：laser shock;W9Cr3Mo4V steel;nano-hardness;elasticity modulus;residual stress;microstructure- 50
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Published：2020-08-13 -
Outage probability analysis in optical communication with pointing errors in strong turbulence channel
Abstract：Light intensity scintillation and pointing error in atmosphere turbulence are the key factors influencing the optical communication performance. According to the K-distribution model and pointing errors distribution model, the analytical expression for outage probability of the communication system was derived by using the MeijerG function under the intensity modulation/direct detection(IM/DD) with on-off keying(OOK) modes. Through numerical calculation, the impact of atmosphere turbulence, beam width and jitter deviation on the system outage probability was analyzed. It indicates that in the strong atmosphere turbulence channel, decrease of beam width can lower the system outage probability, while the jitter deviation of the communication terminal equipment will increase the outage probability. When the beam width is normalized to be 1, the system outage probability declined to 0.12. Hence, it is necessary to further optimize the beam width in order to maintain reliable communication link in the actual communication channel.Keywords：laser communication;scintillation;on-off keying(OOK);outage probability;beam width;jitter deviation- 36
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Published：2020-08-13 -
Design of high resolution and output stability autocollimation system
Abstract：To achieve precise and stable measurement of micro angles, a photoelectric auto-collimation system comprising telephoto objective lens, optical amplifier and shift compensator was established. Firstly, the short structure and long-focus features of the telephoto objective were researched, involving the restrictions and the sensitivity to the variation of structure parameters. The optical amplifier can improved the resolution of image displacement in the auto-collimation system. Then, the drift compensation was introduced based on high resolution. The drift reference beam extracted by the cooperative target, combined with beam steering mechanism was used in the closed-loop control of the drift. Finally, the resolution and stability of the auto-collimation system were tested. The results show that the valid resolution is higher than 0.000 5" and the output stability in two hours reaches 0.006" within the ±30" measurement range, which can meet the requirements of high resolution and high output stability in the field of micro angle measurement.Keywords：angle measurement;auto-collimation;drift compensation;cooperative target- 38
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Published：2020-08-13 -
Mechanical properties enhancement of laser remelting for jet electro-deposited coating
Abstract：In order to improve mechanical properties of the jet flow electro-deposition coating, the impact of laser remelting on performance of the jet flow electro-deposition coating was studied for process parameter optimization. The laser remelting process were realized after preparing the nano-structure copper deposition layer in the 304 stainless steel surface by the jet flow electro-deposition method. Thereafter the coating surface morphology and grain size were observed with Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD), and the mechanical properties of the coating was tested. The results show that under the optimized process parameters where the operating current density is 200 A/dm2 and the scanning speed is 10 mm/s, the surface of the copper deposition layer prepared by the jet flow electro-deposition method is relatively smooth and composed of 60 nm grains, with relatively compact microstructure. The mechanical properties including the micro-hardness and tensile strength are obviously improved after laser remelting, where the micro-hardness can reach 816 HV and the tensile strength can reach 590 MPa. Otherwise the plasticity decreases according to the tensile fracture morphology, which means the process parameters should be further optimized.Keywords：nano-coating;laser remelting;jet electro-deposition;mechanical property- 42
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Published：2020-08-13 -
Microtopography experiment of laser ablation on surface of special-shaped solid wood
Abstract：To overcome the sanding difficulties in costly furniture and wood carving with special-shaped surface, a method in which the pulse laser processing system replaces the traditional manual sanding was put forward. Firstly, the maximum ablation depth per second was obtained by taking the specific energy of materials and incident energy of fundamental-mode Gaussian beam into account. Then, two representative solid wood materials ashtree and Korean pine were sanded respectively by using the Nd:YAG laser with the single pulse energies of 300, 600 and the pulse repetition frequencies of 5, 10 Hz. The experiments indicate that the Korean pine has a smaller ablation depth and a faster ablation rate due to its lower density. Compared with the increase of the pulse energy, the higher pulse repetition frequency can improve the ablation rate more significantly. The maximum ablation rate of ashtree and Korean pine is respectively 0.20 mm/s and 0.33 mm/s, which basically meets the sanding requirement for solid wood furniture with special-shaped surface.Keywords：laser processing;laser ablation;special-shaped surface;sanding;solid wood- 67
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Published：2020-08-13 -
Research on preparation and reflection properties of (Sm0.875La0.125)2Zr2O7
Abstract：Sm2Zr2O7 is a promising material in the field of thermal barrier coating due to its extremely low thermal conductivity, large thermal expansion coefficient, low sintering rate and good thermal stability. In order to improve the reflective properties of the Sm2Zr2O7, La element was dopted in Sm2Zr2O7. The (Sm0.875La0.125)2Zr2O7 with pyrochlore structure was prepared by solid-phase reaction sintering, and the impact of sintering temperature, microstructure and energy band structure on its reflection property were analyzed through X-ray Diffraction (XRD), scanning electron microscope (SEM) and near infrared reflectance spectroscopy (NIRS). The XRD images show that the element La has been successfully adulterated into Sm2Zr2O7 with the pyrochlore structure remaining unchanged, as the particle sizes grow even with the increase of the sintering temperature. The particle distribution was in best uniformity and the band gap is the narrowest, resulting in the highest reflectivity greater than 80% within the 780-2 500 nm wave band. Especially it is over 90% for partial wave bands. To some extent, such good reflectivity has a positive effect in the development of Sm2Zr2O7 surface protection.Keywords：laser protection;rare-earth zirconate;(Sm0.875La0.125)2Zr2O7;reflectivity;sintering temperature;microstructure- 38
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Published：2020-08-13 -
Roughness evaluation of 3D surface profile
Abstract：To directly capture the roughness of the three-dimensional surface profile for surface quality evaluation of the tested parts, thus weighing its processing technology and whether relevant design requirements are satisfied, an evaluation method for the three-dimensional surface profile was put forward. Relevant data on three-dimensional surface profile of the standard sample piece was measured by using the white-light phase-shifting interference system. Then the Gaussian reference plane was set up and the roughness data was extracted. The most important parameters such as amplitude and integrated parameters were calculated after data processing, for analyzing structural feature of the three-dimensional surface reflected by each parameter. Finally the surface profile of the standard block was analyzed comprehensively. The results show that the ratio of the root-mean-square deviation to roughness is 1.04, and ten-point height of the surface is 0.059 μm; the degree of skewness is greater than 0 and gradient less than 3; the root-mean-square(RMS) slope is 2.993 μm, and average curvature of roughness peaks is 0.181 μm. The experimental results conform to distribution characteristics of the surface profile of the grinding template, and in consistence with the measuring values by contourgraph.Keywords：three dimensional measurement;white-light phase-shifting interference;roughness;roughness evaluation- 74
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Published：2020-08-13 -
Waveguide array generated by discrete spatial soliton in Ce: SBN75 photorefractive crystal
Abstract：In order to verify the the feasibility of controlling intense light beam by weak light beam through the spatial soliton waveguide array, the anisotropy of soliton-induced waveguide and its effect on the interaction of discrete soliton waveguide were investigated. By controlling the incident light intensity of the 532 nm laser and the applied voltage, the photorefractive self-focusing effect and diffusion effect of the laser beam in the Ce:SBN75 photorefractive crystal were balanced to form the stable (2+1) dimensional spatial screening soliton, which could induce soliton waveguides. Then a waveguide array for discrete spatial solitons was generated by adjusting the crystal position vertically and horizontally. The optical waveguide and the two-dimensional spatial soliton waveguide array were detected through the coaxial transmittance of spatial solitons and the a 633 nm expanded-beam laser with weak sensitivity to crystal refraction index. It indicates that the spatial soliton is generated in 10 s and the induced optical waveguides have clear profile for the incident light intensity of 0.058 μm and the applied voltage of 200 V. The soliton-induced waveguides have anisotropy, which enables a certain impact on the interaction between discrete soliton waveguides. This result is of great significance to achieving processing and transmission of two-dimensional information by using the spatial solution waveguides.Keywords：optical waveguide;photorefractive crystal;spatial solitons;discrete solitons;anisotropies- 63
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Published：2020-08-13 -
High absolute distance measurement system of laser tracker
Abstract：A combined laser absolute ranging system was designed to achieve the high-precision absolute ranging performance of laser tracker. Firstly, the operating principle and performance characteristics of laser tracker were introduced. Then an absolute range scheme combing the femtosecond laser distance measuring with the phase-shift laser ranging was developed. Based on the principle of the phase-shift laser ranging, the optical path and signal processing system were designed. Finally, the precisions of femtosecond laser distance measuring system and phase laser ranging were tested experimentally. The result indicates that the femtosecond laser distance measuring and the phase laser ranging can achieve a precision of 1 μm+0.5 μm/m and a dynamic ranging precision of ±10 mm respectively within the measurement range of 60 m, which can satisfy the precision requirement of combined ranging system in long-distance measurement. The designed combined-type laser absolute ranging system can meet the performance requirement of high precision, fast measuring speed and dynamic measurement.Keywords：laser tracker;femtosecond laser distance measurement;phase-shift laser ranging;data processing- 87
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Published：2020-08-13 -
Multifocal Fresnel lens based on liquid crystal spatial light modulator
Abstract：Subject to the restrictive relation between resolution and focal depth of traditional imaging lens, a multi-focal Fresnel lens based on phase-spatial light modulator (PLUTO) was developed for the extension of the depth of focus. Based on the analysis of the restrictions imposed by Spatial Light Modulator (SLM) on principle, minimum focal length and diffraction efficiency of Fresnel lens, the Fresnel lens of different focal lengths combined with the blazed grating were programmed in the pixel region of Liquid Crystal Spatial Light Modulator (LC-SLM) by Matlab. The pixel control characteristics of PLUTO enabled the phases of multiple lenses equiprobably distributed in each pixel of PLUTO. In accordance with the overlapping principle for axial focuses of each lens, the multiplex lens with a focal depth of 16 mm was obtained. Compared with a single lens with the same numerical aperture, the focal depth achieved by the multiplex lens is increased by 5 times. In addition, the focal spot remains in the same size, with approximate imaging resolution to single lens within the whole range of depth of focus.Keywords：spatial light modulator;multiplexing multifocal lens;Fresnel lens;extended focal depth;diffraction efficiency- 108
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Published：2020-08-13 -
Electrical conductivity of graphene film electrodes on PET and SiO2 substrate under blue light irradiation
Abstract：Light irradiation could result in the decline of electric property of transparent graphene electrodes, which was dominated by blue light for LED backlight. In order to study the stability of the electric properties under blue light irradiation, graphene electrodes with different substrates were taken as the samples, including the flexible PET-based and inflexible SiO2-based graphenes. Then the conductivity of the graphenes under blue light irradiation of different powers and different environmental atmospheres were investigated, and the impact of doping on the conductivity stability was analyzed. The results indicate that the conductivity of graphene with different substrates, changes in blue light, with the amplitude and speed of the variation subjected to the irradiation time, environmental atmosphere, doping and irradiation power. Under the 10 h long-term irradiation, the relative resistances of the PET-based and SiO2-based graphenes without dopants in vacuum decrease by 29.5% and 10.1% respectively. After doping, those values drop to 13.0% and 4.6% respectively in the same environment while decline to 7.1% and 2.7% respectively in the ambient environment. The absorption of gas molecules and AuCl3 dopant can reduce such conductivity change and improve the resistance stability of graphene. The research provides significance reference for the stability enhancement of the long-term application of transparent graphene electrodes.Keywords：graphene transparent electrode;PET substrate;SiO2 substrate;electrical conductivity;resistance stability;blue light irradiation- 39
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Published：2020-08-13 -
Application of pseudo-random code in miniature absolute encoder chip
Abstract：To solve the problem of large volume and low precision for traditional absolute encoder, an absolute encoder chip based on the M-code pseudo-random binary sequence was designed. With overall consideration of advantages and disadvantages of absolute encoding mode, the sing M-code track was designed for avoiding the multi-track and large size of the traditional multi-loop absolute encoder track, thus realizing the miniaturization of absolute encoders. Subjected to the interpolation of the internal ACD, the combination of the M-code channel with the incremental precise-code channel can highly improve the resolution of the absolute encoder to 19 bit with a rather low external noise. Finally, an error compensation algorithm based on the neural-network were adopted to reduce the subdivision error by twice or three times, thus the system precision of the encoder was greatly improved. After compensation, the standard deviation of the encoder system is 8.4''. The absolute encoder can basically meet the requirements for small volume, high precision and high reliability, with certain engineering application values.Keywords：photoelectric encoder;absolute encoder;chip;Subdivided error;pseudo-random coding;error compensation- 63
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Published：2020-08-13 -
High repetition rate laser ranging to space debris from Changchun Observatory
Abstract：Based on the high running speed and poor forecast accuracy of space debris, the key technology for space debris laser ranging with high repetition rate was discussed, and the laser with high repetition rate and high beam quality was employed to improve the laser output power density. The concept of echo index was proposed and the observation target database of space debris was established. Then reference values f the forecast distance were corrected by fitting the data originated from the optical position deviation information, thus improving the success rate. The feasibility and effectiveness of such method were verified on the 60 cm laser ranging system in Changchun Railway Station. During the experimental observation period of 26 days, 466 circles of data for 233 different space debris targets have been obtained. The data statistic shows that the radar cross section (RCS) is 0.9 m2~26.1 m2 when the observation distance from the target is 400 km~1 800 km, with a ranging precision of approximately 1 m. Such space debris laser ranging system with high repetition rate can not only help obtain effective observation data, but can also improve the observation success rate. In addition, the observation data can be used for orbit measurement and orbit determination of non-cooperative space target, precise cataloging and other scientific application researches.Keywords：space debris;laser ranging;high repetition rate;data identification;forecast improvement- 48
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Published：2020-08-13 -
Scintillation in turbulent atmosphere laser communication
Abstract：The laser atmosphere communication system was employed to carry out near-surface laser atmosphere transmission experiments for observation of scintillation indexes of different seasons and different wavelengths. The measurements were performed every 10 minutes in a period from 8 am to 21 pm. Each time collected 15000 gray level images for processing and analysis, where the daily samples in good regularity were selected for comparison. Experimental result shows that scintillation index increases with the increases of temperature and turbulence effect, but decreases with the decreases of temperature and turbulence effect. In addition, the index decreases with the increases of wavelength. The longer the wavelength is, the better stability will be. The measured scintillation index is basically equal to theoretical Rytov variance, which verifies the feasibility of Rytov variance under weak fluctuation condition. It can be concluded that the scintillation probability density function of light intensity conforms to normal distribution according to the statistical data distribution. The exponents of light intensity fluctuation power spectrum vary in the range of -7/3 to -12/3, being lower than experimental results given in other documents. The results can be a reference for the further research of satellite-ground laser communication.Keywords：laser communication;Atmosphere turbulence;scintillation;scintillation index- 74
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Published：2020-08-13 -
Effect of PBSs on nonlinearity in a homodyne interferometer
Abstract：The non-linear errors caused by performance deficiency of 3 polarized beam splitters (PBS) located on the interferometer part and detection part of homodyne laser interferometer were calculated respectively on the basis of Jones matrix. Firstly, the composition and working principle of the homodyne interferometer were introduced. Then the ideal Jones matrix was modified for establishing the error analysis models of the PBSs with different purpose. The simulation of the non-linear errors induced by PBS separately and integrally was performed in Maple software. In combination of the simulated curve and error analysis model, it shows that the PBS1 at interference part mainly causes non-orthogonal error and PBS2 and PBS3 at detection part mainly cause DC drift error and unequal amplitude error. Therefore, the non-linear error reduces from 2.32 nm to 0.23 nm by adopting PBS with better performance. The DC drift and unequal amplitude error caused by PBS2 and PBS3 was eliminated by adjusting the gains of detectors. The research results provide theoretical foundation for further compensation to non-linear error caused by PBS.Keywords：homodyne interferometer;Polarized Beam Splitter(PBS);non-linear error;DC drift;unequal amplitude;non-orthogonality- 55
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Published：2020-08-13 -
Fringe counting scheme with two directions and dual threshhold for Mach-Zehnder interferometer
Abstract：To realize accurate measurement of phase shift of interference signals, an optical path structure based on Mach-Zehnder Interferometer was established. A fringe counting demodulation scheme with high accuracy was put forward. Firstly the structure of Mach-Zehnder Interferometer was introduced, and a data processing scheme for resisting light source interference was proposed base on the relationship between the input light intensity signal and output interference signal, which was from Mach-Zehnder Interferometer with 3×3 fiber coupler. Then due to the deficiency of conventional fringe counting demodulation, an improved demodulation with high accuracy was proposed by combining zero-cross detection with threshold method. This method changes the unidirectional counting single into bidirectional counting single. Finally, an interference system based on Mach-Zehnder Interferometer was established for the verification of the improved demodulation scheme through optical tensile experiment. The experiment result shows the direction judgment times of the improved demodulation scheme is 4 times as many as that of conventional scheme, and π/4 phase change quantity can be realized. The demodulation accuracy of the improved demodulation scheme increases dramatically, for the total phase demodulation accuracy is improved to 4 times of the traditional count scheme.Keywords：coherence optics;Mach-Zehnder interference;phase demodulation scheme;stripe count;3×3 coupler- 75
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Published：2020-08-13 -
A portable laser Raman detector used for detecting illegal additives in condiment
Abstract：Aiming at on-line fast detection of illegal additives, a portable Raman detector, consisting of 785 nm wavelength laser, spectroscope, focusing lens, glass filter, spectrometer, spectral analysis software and portable computer etc., was developed based on laser Raman principle. The focus light path and gathering light path were designed. Then the spectral analysis software was designed for accurate analysis on overlapping peaks of Raman spectrum by using the immune genetic algorithm and the particle swarm optimization algorithm. Subjected to silver ion Raman fortifier and matching agent, the mixed solution of 1×10-6 Rhodamine B and Basic Orange II was detected by the portable Raman detector experimentally. From the Raman spectrum signals, the illegal additives with overlapping peaks were identified. The instrument can effectively separate overlapping peaks of Raman spectrum with the measurement resolution ratio of 2.3×10-9 and detection time including simple preparation and preheating of instrument lower than half an hour, which can provide assistance for food quality supervision departments.- 56
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Published：2020-08-13 -
All-solid-state 210 nm quasi-continuous deep ultraviolet laser
Abstract：By using a domestic fiber output semiconductor laser with 808 nm wavelength, an all-solid-state deep ultraviolet laser was developed. The Laser Diode (LD) end pump Nd:YLF crystal and acoustic-optical Q-switch were adoped to realize quasi-continuous fundamental frequency radiation at 1 053 nm, which was subjected to second harmonic generation, fourth harmonic generation and fifth harmonic by using one LBO crystal and two BBO crystals outside the cavity. Thus the output of quasi-continuous 210 nm deep ultraviolet laser was achieved. The relationship between the output power of the laser and the pump power were researched experimentally. When the pump power of LD is 13 W, the modulation frequency of acoustic-optical Q-switch laser is 1 kHz and the average output power of fundamental wave is 1.33 W, the average output power and the pulse width of the deep ultraviolet laser was 17 mW and 6.1 ns respectively. Furthermore the deep ultraviolet laser is characterized by good beam quality, simple configuration and easy operation, thus prone to minimization.Keywords：all-solid-state laser;deep ultraviolet laser;fifth harmonic generation;quasi-continuous- 71
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Published：2020-08-13 -
Shearer precision positioning system based on laser scanning technology
Abstract：Aiming at the inaccuracy of existing positioning technology underground coal mine, a precision positioning system by using coal cutter with combination of front triangle intersection and sector laser scanning was proposed. The basic positioning principle of the receiver installed on the body of coal cutter was derived based on two-station-system by using the difference of time signal of system. Then the position information receiver in the coordinate of system, involving pitch angles and horizontal angles, was transformed into coordinated of the coal cutter in local geographic coordinate system in mining area. Finally, positioning experiments were performed in the area(15.341 m×4.125 m) of fully mechanized face by simulation. The results show that the maximal errors on X-axis, Y-axis and Z-axis are 0.116, 0.093 and 0.132 m respectively, while the three-dimensional positioning accuracy of the system and the unit distance is 0.139 97 m and 0.018 763 m/m respectively. The proposed system can meet the requirements of positional accuracy for coal cutter of fully mechanized face on headpiece or tail.Keywords：coal cutter;precision positioning;laser scanning;triangle intersection- 41
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Published：2020-08-13 -
Optimization of processing micro-channels with CO2-laser on polyethylene terephthalate(PET) sheet
Abstract：In order to improve the processing quality of micro-channels, the fabrication technology of micro-channels on polyethylene terephthalate(PET) substrate using CO2 laser was researched. The effects of the processing parameters, including laser power, processing speed, channel length and processing times, on the width of micro-channel were analyzed and optimized through orthogonal tests. Furthermore, the processing results under the optimal parameters were tested by using metallographic microscope and roughness tester. The results show that the arithmetic average value of roughness (Ra) on the surface of channel can reach 170 nm, when the laser power is 10 W, scanning speed is 6 mm/s; channel length is 80 mm and processing times is 3. Therefore, the method of processing micron-size channel on PET substrate by using CO2 laser is completely feasible.Keywords：CO2 laser;polyethylene terephthalate;orthogonal test;arithmetic average roughness- 40
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Published：2020-08-13 -
Visual detection system design for profile of special-shaped stamping parts
Abstract：In order to realize the profile defect detection for the special-shaped stamping parts, a visual detection system was designed. The hardware components and working principle of the system were introduced. In this system, the profile of parts was extracted by using the level set method combined with Chan-Vese model based on its irregular shapes. In the Chan-Vese Model, energy function was set up and optimized in order to enable the profile curve approaching the profile boundary of the stamping parts in the collected image, thus effectively controlling the noise interference improving the extraction accuracy. Finally, the defect of the stamping parts was indentified according to the multi-sample hu moment parameter and areal sampling threshold which generated from the hu invariant-moment profile matching and area matching methods respectively. The defect identification method was characterized by rotation, translation invariance and good robustness. The results indicate that the system can detect defects over 0.5% of the overall part with high detection precision, and is suitable for profile defect detection demand for high stability and security as well as high precision.Keywords：visual detection;special-shaped stamping parts;level set;profile extraction;profile matching- 58
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Published：2020-08-13 -
Automatic measurement of triangle orientation discrimination threshold
Abstract：In order to reduce the impact of subjective factors on the triangle target orientation discrimination rate in Triangle Orientation Discrimination Threshold (TOD) measurement for the opto-electronic imaging system, and to effectively improve the measurement efficiency, an automatic machine vision method for replacement of artificial discrimination was proposed, and a TOD automatic discrimination modal was established based on correlation matching. In this mode, the MTF in human visual system was taken as the base for the treatment of target image transmission attenuation. The automatic triangle orientation was discriminated by calculating the relevancy between target image and template with the correlation calculation-based template matching method. In addition, a triangle target template was established based on the standard TOD model measurement for comparison of the accuracy between the artificial discrimination and the automatic mechanical discrimination. Finally, a systematic TOD curve was plotted in accordance with the fitting results of the Weibull visual and psychological measurement function. It indicates that compared with artificial discrimination, the average accuracy deviation for mechanical triangle target orientation discrimination is 0.9%, which means the curves for discrimination threshold through artificial discrimination and mechanical discrimination are in good agreement and can be applied to the TOD curve measurement for opto-electronic imaging system.Keywords：opto-electronic imaging system;triangle orientation threshold discrimination;automatic measurement;Human Visual System(HVS)- 51
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Published：2020-08-13 -
Reening mechanism of laser shock wave in Al-Cu alloy at liquid nitrogen temperature
Abstract：The propagation and strengthening mechanism of cryogenic laser shock in Al-Cu alloy were studied through numerical simulations and experiments. Firstly, the molecular dynamic model of Al-Cu alloy was established by Lammps software. Based on the modal, the variations of shock velocity and shock pressure respectively with particle velocity were obtained at room-temperature (293 K) and Liquid Nitrogen Temperature (LNT) (77 K). Then the evolution of dislocations induced by laser shock wave was analyzed. Finally, the simulation was proved by experiments. The results indicate that the shock velocity and pressure induced by laser shock wave at LNT are 7.31 km/s and 25.93 GPa respectively, which are greater than those at room-temperature. Moreover, the dislocations generated by cryogenic laser peening are more stable and uniform. The maximum atom number of dislocations is 104 381, which is approximately 30.5% more than that at room-temperature. The reason is that at NLT, Al-Cu alloy has better FCC lattices with short atomic spacing and uniform atoms arrangement, which not only accelerates the energy transfer between two adjacent lattices leading to the increases of the shock velocity and pressure induced by cryogenic laser peening, but also promotes the nucleation and growth of dislocations resulting in a better strengthening performance compared with cryogenic laser shock peening at room temperature.Keywords：cryogenic laser peenig;liquid nitrogen temperature;molecular dynamics;dislocations;Al-Cu alloy- 49
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Published：2020-08-13 -
Real-time prediction correction of telescope in day-time satellite laser ranging
Abstract：To increases the working quantities of observer without high observation efficiency,the measured data was used to calculate the predicted time bias, which can correct the time bias of prediction of the targets in the next pass. The telescope pointing corrections were performed at first, involving the atmospheric refraction modification and the tri-axial error correction. The predicted time bias was calculated with distance information of measured data, which means to calculate the predicted time bias with the measured data of the first few segmental arcs, including data of night. Finally the time bias in the prediction of track at next round was corrected and evaluated. Experimental result shows that the traditional M-M atmospheric refraction correction model and theodolite tri-axial correction model can increase the (RMS) of telescope pointing to 5~10", which can meet requirement of satellite laser ranging in the daytime (10"). The bias quantity of target can be decreased by 1~3" by correcting the prediction pointing of time bias. Partial correction quantity can be as much as 8".Keywords：satellite laser ranging;pointing deviation;axial system error;error correction- 48
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Published：2020-08-13 -
Structrual design of detector for optical elements with large aperture
Abstract：In order to meet the requirements for surface defect detection of optical elements with large caliber in optical detection systems, a defect detector with four degrees of freedom was designed. The detector was controlled by four independent drive devices. The matrix transformation of coordinate system was employed to calculate the kinematics of the defect detector, involving the relationship between the trajectory coordinates of objective lens and displacement of actuators and the relationship between each follow-up servos and the active servo. The kinematics results were verified by ADAMS, a virtual prototype simulation software, obtaining the displacement-time curves. Furthermore, the static position deviation of objective lens and cantilever structure of the lens cone were analyzed by ANSYS Workbench. The results indicate that the maximum of static position deviation of lens is 19.82 μm. The deviation can be decreased to less than 1 μm by adjusting 1/36 round of precise pitch of precise angle adjustment, which can satisfy the design indices of ±10 μm. Moreover, the working frequency is far less than the first-order natural frequency of 882.58 Hz, which can avoid the destruction to the whole structure caused by syntony, thus verifying the reliability and safety of the equipment.Keywords：optical inspection;defect detector;inverse kinematics;Finite Element Analysis(FEA);Modal analysis;ADAMS- 42
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Published：2020-08-13 -
Fresnel zone plate and its application in optical acceleration sensor
Abstract：A method to design and prepare a Fresnel zone plate for all-optical type acceleration sensor was proposed, and the design principles and parameters of the Fresnel zone plate was introduced. The maximum and minimum theoretical radii of the wave band plate were 494.19 μm and 78.11 μm respectively with the size precision in micron level. The micro-nanofabrication process technology of the zone plate was developed. Then a high-quality zone plate was successfully fabricated. The boundary of the zone plate was smooth and complete, thus proving good focusing and imaging properties. Finally, an all-optical type acceleration sensor based on the zone plate diffractive properties was developed and tested. In terms of the output curves from the test, it shows that the output of the sensor proves a good linearity with the acceleration and the sensitivity is 0.033 V/g. The sensor guides light with optical fibers instead of electronic components, which provides good resistance to electromagnetic interference and promising applications in harsh environments.Keywords：diffractive optical element;zone plate;diffraction;microfabrication;acceleration sensor- 77
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Published：2020-08-13 -
Overall signal transition of linear HgCdTe focal plane array device induced by pulsed laser
Abstract：In order to investigate the response characteristics of linear HgCdTe focal plane device with Capacitive Feedback Transimpedance Amplifier (CTIA) readout circuit under intense laser irradiation, single shot irradiating experiments were performed by using a 2 μm waveband pulsed infrared laser with a pulse duration of about 100 ns. The pulsed laser induces a new phenomenon of overall signal transition, in which the output signals of all pixels of the linear device have an approximately same increment after irradiated by a relatively intense laser pulse. The rules of the overall signal transition were summarized and it demonstrates that the overall transition occurs at a laser intensity of approximately 1 μJ/cm2 and get saturated at about 100 μJ/cm2, during this period, the transition increases with the increase of the irradiation intensity. Influence factors such as optical crosstalk, electric crosstalk, and thermal accumulation were analyzed and excluded. Further investigation indicates that the overall signal transition is primarily attribute to the voltage drop of the couple capacitor caused by rapid discharge during intense laser irradiating in the power supply circuit, thus resulting in a transformation of operational state of all the photosensitive diodes from zero-bias to reverse-bias, which are connected by a common P-region electrode on surface of the chip.Keywords：laser irradiation effect;pulsed laser;HgCdTe;focal planed array;response charateristics;overall signal transition- 59
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Published：2020-08-13 -
Root welding process in laser-TIG hybrid welding of titanium alloy thick plate
Abstract：Aiming at the restrictions of lower degree of automation, difficult weld reform control and inefficiency in root welding of titanium alloy, a laser-arc hybrid welding technique was realized to fabricate a titanium alloy plate with thickness of 10 mm. The welding process and weld seam forming mechanism were investigated experimentally. During the interaction between pulsed laser with low power and TIG arc plasma, the plasma behaviors and molten pool state were monitored using a visual system. The result indicates that pulsed laser can not only improve the arc discharge, but also regulate the flow of the molten pool and heat distribution of TIG arc during the hybrid welding process. The arc was gathered nearby the acting point of laser with a distance between the two heat sources is 3 mm, where the molten pool was forced to flows backwards by the coupled arc bonding force and heat transfers backwards. Meanwhile the heat distributed in the front and back of the molten pool keeps the stress balanced and stable, resulting in a well surface appearance welding seam with yield strength of 96.3% and tensile strength of 95.8%.Keywords：laser-arc hybrid welding;titanium alloy thick plate;hybrid heat source;root welding;energy distribution- 79
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Published：2020-08-13 -
On-line automatic measuring system for total sugar content in chlortetracycline fermentation tank based on refraction method
Abstract：It is hard to automatically determine total sugar content due to high viscosity, complex composition and impurities of chlortetracycline fermentation solution, therefore an online automatic measuring system for total sugar content based on refraction method was developed by using an STM32F103R microcomputer as the main controller and a CCD as the imaging sensor. The principles of refraction and reflection occur in the light propagation in different medium were analyzed and applied to measure the total sugar content in chlortetracycline fermentation tank. In the measurement, fermented liquid automatically taken out from the chlortetracycline fermentation tank was filter at first. Then the refractivity of the solution was calculated with the data of CCD, thus the total sugar content of fermented liquid was evaluated. The experimental result demonstrates that the system developed in this paper with the measuring precision of 0.1 °Brix runs stably in the process of experiment, and can meet the requirements of production in real field.Keywords：Chlortetracycline fermentation tank;Total sugar content;Refractive method;Charge-coupled device sensor;Automatic measuring system- 61
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Published：2020-08-13 -
Solar-pumped Cr/Nd: YAG ceramic laser focused by Fresnel lens
Abstract：In solar-pumped laser with Fresnel lens and Cr/Nd:YAG ceramic, the laser output power depend highly on coupling factor of pumping light and laser rod in the axial direction. In this paper, the method of tracking angle error attributed to the incident solar ray unparallel with surface normal of Fresnel lens result, was used to calculate the dependence of laser output power on angles experimentally. By using ceramics cavity, the effect of secondary or more reflection beam condenser on the output power was reduced. The experiment result shows that the laser output powers are reduced by 1/6 of the original ones from 0°to 0.5° for refractivity of 97% and 99%, respectively. The physical model was set up to analyze the effect in different tracking angle errors, where the calculation value is in agreement with the experiment result. Results indicate that the beam and laser rod coupled in axial direction perfectly, thereby the removal of the end mask and the adoption of the second condenser will obtain highly axially coupling end pumping beam by which the laser output power is improved greatly.Keywords：solar pumped laser;Fresnel lens;Cr/Nd:YAG ceramic;output laser power;axial coupling factor- 63
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Published：2020-08-13 -
Development of wide field of view technology of synthetic aperture lidar
Abstract：The development of Synthetic Aperture Ladar (SAL) both at domestic and abroad was reviewed, where the technical difficulties in its application and practice were introduced. Among these problems, the solutions to that of narrow field of view (FOV) were analyzed, demonstrating theoretical restriction in FOV of heterodyne detection in SAL. The endeavor and exploration of wide FOV SAL were summarized at home and abroad. Finally, the future development prospect of SAL was described and analyzed.Keywords：laser ladar;synthetic aperture;wide field of view;heterodyne detection;receiving field of view;imaging demonstration- 56
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Published：2020-08-13 -
Performance of ARQ scheme over FSO system
Abstract：In order to fairly analyze the performance with Automatic Repeat Request (ARQ) mechanism in Free Space Optical communications (FSO), the effective ARP is proposed. The performance of the system was studied, involving bit error probability and throughput. By evaluating the energy consumption attribute to frame retransmissions in FSO, good performance gain was achieved only for reasonably high average received power. The experimental results indicate that the ARQ scheme serves effectively only when ARP is higher than -29.2 dBm in weak turbulence channel and -31.7 dBm in strong turbulence channel. Furthermore when the conventional ARPs were higher than -24.2 dBm and -17.2 dBm respectively in weak turbulence channel and strong turbulence channel, the performance of the FSO system is improved significantly, whereas it is poor at low ARP due to the massive retransmissions and the huge energy consumption.Keywords：Free Space Optical communication (FSO);Automatic Repeat reQuest (ARQ);Average Received Power (ARP);Bit Error Probability (BEP);throughput;goodput- 54
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Published：2020-08-13 -
Development of laser cell technology
Abstract：The development of pace and ground laser wireless energy transmission was overviewed from different aspects, including the selection of laser cell materials and laser devices, the cell structure, the surface electrode distribution, the impact of the uneven illumination and illumination position on the conversion efficiency of cells, the impact of Gaussian beam on cells and working parameters of cells etc. Laser cells can realize a large power output by using a small equipment area, which have important applications and a promising further in the fields of high-efficiency electric power supply, quick charge, laser wireless energy transmission and so on. In addition, the review of the laser cell can provide technique support technology in the aerospace fields involving spatial sciences, remote sensing and environment monitoring etc.Keywords：laser wireless power transmission;laser cell;development trend- 53
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Published：2020-08-13 -
Blocking improvement of hybrid optical switching networks by dynamic interlaced assembly
Abstract：In hybrid optical switching networks, a waveband switching method named dynamic interlaced assembly (DIA) for the reductions of high blocking rate and edge-to-edge delay of the virtual wave group scheduling (VWGS) was proposed, in order to avoid the contention of waveband and wavelength channels. At edge nodes, the DIA gathered the wavelengths into a waveband with odd/even and positive/negative sequence to increase the separation among services. Furthermore, the number of wavelength channels was dynamically optimized and the contending probability of traffic was decreased at core nodes based on Ferry formula. The numerical results show that, DIA improves the blocking and delay with high flexibility of waveband assignment. Compared with VWGS, the blocking rate is lowered about 0.5-3 levels and the average edge-to-edge delay is reduced by 25%-40% in light and middle traffic states. Without the supports of wavelength tunable converters and optical buffers, DIA could guarantee the requirements of services with respects to loss and delay with high efficiency of energy consumption and cost, thus proving to be a promising technology to enhance the practicality of hybrid optical switching networks.Keywords：optical switching network;hybrid optical switching;waveband assembly;blocking rate;edge to edge delay;Dynamic Interlace Assembly(DIA)- 47
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Published：2020-08-13 -
Research on scintillation and pulse distortion measurement of atmospheric optical transmission channel
Abstract：To analyze the influence of atmosphere on optical signal transmission, the methods of measuring scintillation in the optical power received by a finite aperture and temporal pulse-waveform distortion have been researched, and the mathematical model for analyzing the measurement data has been established. Between two tall buildings standing 6.2 km apart, the measurement experiment on laser transmission has been carried out; a CCD sensor is used to detect the received optical pattern images, which are defocused; a high bandwidth digital oscilloscope is used to record the temporal waveform of received pulses. Based on the recorded pattern images and pulse waveforms, the probability density distribution of the optical-power scintillationreceived by a virtual circular aperture and the temporal waveform distortion of received optical pulses have been analyzed, respectively. It is shown that:the Nakagami distribution is more accurate than the lognormal distribution for characterizing relatively weak fluctuations in the received optical power; the negative exponential distribution can be appropriately used to describe very strong fluctuations in the received optical power; for a rectangular pulse train transmitted at a repetition rate of 100 MHz, the side lobes in the frequency spectrum of the transmitted temporal pulse waveform with a frequency related to their peaks equal to or larger than 0.48 GHz almost completely disappear when the pulses arrive at the receiver end, and meanwhile obvious spreading of the temporal intensity distribution of a single pulse can be observed with the peak intensity occurring at the moment when the trailing edge of the transmitted pulse reaches the receiver end.Keywords：laser transmission;pulse;atmosphere;scintillation;distortion- 53
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Published：2020-08-13 -
Design of light extinction liquid-borne particle counter with dual optical path
Abstract：Light-blockage liquid particle counter has been widely applied in the field of hydraulic pressure, electric power, medicine and environment etc. In practical application, however, an impact will be exerted on the accuracy and repeatability of measurement due to the phenomenon that particles with irregular shapes, under light irradiation in different directions, will produce different projected area. In this paper, a dual optical-path liquid particle counter based on light blockage is designed. Vertical and interlaced dual optical path detection structure can help to obtain the size information for particles in different directions and improve the result of inconsistent projected area. At the same time, considering the impact of sample concentration on coincidence error, sensing area of the sensor is defined in accordance with the maximum particle concentration and detection range. While in consideration of the problem that different color of the samples will affect output reference voltage of the photoelectric detector, a feedback mechanism is introduced to adjust the light intensity for stabilizing the reference voltage; and an analysis on the impact of flow rate on pulse signal through a simulation and actual measurement in the 70 μm spherical particle.Keywords：Light blockage;dual optical path;particle counter;sensor;impulse waveform- 52
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Published：2020-08-13 -
Monitoring method and experiment for stratum stress based on fiber Bragg grating sensing
Abstract：To achieve effective monitoring of underground rock formation stress and its changing rules, a monitoring method combining rectangular strain rosette with FBG (Fiber Bragg Grating) based on FBG sensing technology is put forward. Method:adhere fiber grating to the groove of fiber carbon laminated composite materials to form the fiber strain sensor unit, and three fiber strain sensor units were attached to the cylindrical structure in the form of rectangular strain rosette to form the drilling three-component sensor for monitoring of plane stress state; deduce the relationship between the maximum principal strain and wavelength change based on bi-direction strain characteristic equation and FBG strain sensing theory, and then work out the relationship between principal strain and wavelength change in accordance with Hooke's Law and elasticity modulus of the formation where the sensor is located; carry out the temperature calibration and strain calibration in the fiber strain sensor unit, and then conduct a simulation experiment in the sensing devices indoors. The results indicate that strain monitoring range of the fiber strain sensor unit is -1500~1500με; the stress measuring span is 0~4 MPa; average monitoring error of the principal stress is 1.50%; the stress resolution is 0.02816 MPa. Monitoring results of the sensor is consistent with changing rules of the actually-loaded stress, which can meet the requirements for continuous monitoring of the underground vertical and plane stress.Keywords：FBG;carbon fiber laminated composite material;rectangular strain rosette;fiber strain sensor unit- 67
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Published：2020-08-13 -
Far field diffraction performance and testing for metal-coated and uncoated cube corner prism
Abstract：Far-field diffraction performance of cube-corner prism will directly affect the ground laser echo detection. In order to study the reflection polarization change performance and far-field diffraction performance of metal-coated and uncoated cube-corner prism, and apply them to different cube-corner prism design and satellite laser ranging technology, a far-field diffraction model for cube-corner prism is established and the far-field diffraction simulation patters in different polarization azimuth angles are obtained based on the light reflected field and far-field diffraction intensity distribution worked out by using the polarization vector analysis method and light diffraction theory. Then a contrastive analysis is conducted in actual measurement and simulation results of the far-field diffraction patterns by establishing a testing system for far-field diffraction patterns of the cube-corner prism, thus obtaining the reflection polarization state change and far-field diffraction performance of metal-coated and uncoated cube-corner prism. It indicates that the far-field diffraction energy of metal-coated cube-corner prism is more concentrated, and intensity of the two reflected light polarization components can reach 2 orders of magnitude; far-field diffraction energy of the uncoated cube-corner prism is relatively scattered, and intensity of the two reflected light polarization components is close to each other; the simulation results are consistent with the test results. The simulation model established for far-field diffraction of cube-corner prism can be applied to the design of satellite laser reflector for different purposes, as well as to the performance evaluation for laser echo.Keywords：laser reflector;metal-coated cube-corner prism;reflected light polarization state;far-field diffraction pattern;test comparison and analysis- 56
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Published：2020-08-13 -
Technology of optical detection of lightning from space
Abstract：The lightning imager detects the lightning signals from space by taking advantage of the optical imaging technology. The geostationary lightning imager can realize real-time monitoring and early warning for severe convection weather by detecting lighting signals continuously, which is considered to be the most effective lightning detection method. First, the theory of satellite-based lightning detection and the technical characteristics of Chinese FY-4 Lightning Mapping Imager (LMI) have been analyzed. It is further proposed that the effectiveness of satellite-based lightning detection can be verified through "satellite-ground" contrast experiment. The lightning imaging products from TRMM Lightning Imaging Sensor (LIS) are compared to the lightning stroke data from the ground-based lightning detection network. Contrast results show that both types of data have relatively strong correlation. It concludes that the technology of optical detection of lightning from space is feasible and reliable. In future, the key technologies of FY-4 LMI will to be further improved, and LMI will be applied to weather forecasting, convection event monitoring, and typhoon tracking.Keywords：lightning detection;lightning imaging;geostationary satellite;severe convection- 66
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Published：2020-08-13 -
Summary on optical diagnostic technology of piston type internal combustion engine
Abstract：In the research and development of piston type internal combustion engine, the design of optical engine and the application of optical diagnostic technology are important means for revealing working process of internal combustion engine. As the non-contact measurement method, the optical diagnostic technology may make measurement more accurate and profound under the precondition where the interference with test scene is reduced as much as possible; simultaneously, for measurement and analysis of resultants including spray pattern in cylinder, velocity field and soot, etc, it may provide reliable experimental basis for three-dimensional computational fluid dynamics. This paper has firstly introduced the design classification of optical engine for optical diagnostic technology, including early design of optical channel, the optical engine with bottom fenestration of the existing engines and three-direction optical engine, etc. Then, according to different stages of working process of engine, it has discussed application of all kinds of optical diagnostic technologies; finally, it summarizes the development trend of optical diagnostic technology, and indicates combined application of several kinds of diagnostic technologies and that the transformation from one-dimensional measurement to multi-dimensional measurement is the development trend of optical diagnostic technology of piston type internal combustion engine.Keywords：piston type internal combustion engine;optical engine;optical diagnostics;fuel spray;discharge- 53
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Published：2020-08-13 -
Automatic measurement system for wave height and length of sawing wire
Abstract：To realize the automatic measurement of waveform and parameters of sawing wire, this paper has researched and developed a kind of automatic measurement system of sawing wire based on image processing. The system collects, identifies and handles single image of steel wire by adopting image measurement method, and parameters of wave height and length in single image are obtained. Then, rotate steel wire, and collect several images in the process of rotation of steel wire for a period. Restore 3D structural model of steel wire; separate big and small waves of steel wire, and obtain actual parameters of steel wire. Finally, adopt sub pixel subdivision to improve resolution ratio and repeated accuracy of image measurement. Experimental results show that:the resolution ratio of this system may reach 0.1 μm; the measurement accuracy of big wave height is less than ±1 μm, while that of small wave height is less than ±3 μm, which not only meets demands for full automation and high repeated accuracy but also has very high accuracy ratio in the aspect of identification and separation of big and small waves.Keywords：sawing wire;automatic measurement;sub pixel;wave height and length- 37
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Published：2020-08-13 -
Accurate measurement method for density of diamagnetic material
Abstract：Aiming at disadvantages of low accuracy or complicated operation calculation process of the existing density detection method, and combined with technology of magnetism-Archimedes suspension, a kind of accurate measurement method for density of diamagnetic material has been proposed. Measuring equipment for magnetic suspension used by this method may guarantee that sample tested could reach stable suspension, and the suspension height of sample has correlation with density of sample itself under the condition where other experimental conditions are certain. The relation function between suspension height of sample and density of sample has been established, and the density of sample may be calculated through suspension height of sample in the equipment. By fitting a set of suspension height of standard density sphere under experimental conditions given, the calculation formula has been obtained, in which density could be calculated under arbitrary conditions according to suspension height of sample, and the accuracy of formula has been verified through many experiments. In addition, experiments with several kinds of high polymer materials are contrasted with traditional buoyancy methods. Experiment and analysis results show that:this measuring equipment has easy and simple operation, relatively high measurement accuracy (reaching 0.0025g/cm3) and great application and development space. Compared with traditional method, this method has higher measurement accuracy for density measurement of sample with small size.Keywords：diamagnetic material;density measurement;accurate measurement;magnetism-Archimedes suspension;fitting formula- 35
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Published：2020-08-13 -
Recognition of removal performance of BK7 glass by taking advantages of status signal features
Abstract：The experiment table for scratching of grinding material of diamond has been established, and the BK7 glass is scratched aslope and cut in deeply for scratching. Collect acoustic emission signal and force signal in the process, and then obtain its typical features. Experimental results show that the process signal features may represent the removal process of hard brittle material with real time and accuracy. Great cutting-tool angle has inhibiting effect on production and extension of crack, and the amplitude fluctuation of force and acoustic emission signals in the scratching process is relatively slow; while small cutting-tool angle and the increase of cutting edge may give rise to more obvious brittle fracture, and it represents that the amplitude fluctuation of force and acoustic emission signals is heightened. Experiments of BK7 optical glass for scratching of three diamond indenters have show that:in the phase of brittle removal, the obvious cutting-in turning point exists for BK7 optical glass; when exceeding such cutting-in point, materials will generate greater brittle failure, and corresponding growth rate of acoustic emission energy may also be increased. Specific value has connection with type of indenter. Research results are beneficial to balance of contradiction between processing efficiency and processing quality of hard brittle materials in the process by taking advantages of optimization processing parameters of process signals in the actual processing.Keywords：BK7 optical glass;scratching experiment;status signal;feature extraction- 47
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Published：2020-08-13 -
MEMS micro-mirror of folded double S-shaped bimorph electro-thermal actuator
Abstract：Purpose:to design a MEMS micromirror with wide angle, large displacement and low voltage. Method:design a new-type MEMS micromirror capable of overcoming electrostatic drive by adopting the folded dual-S double-layer beam driving structure, and achieve the electrothermal differential drive of bi-materials by adopting the MEMS micromachining process combining surface silicon with SOI, which not only solved the problem of instability caused by ambient temperature, but also achieved the record-breaking wide-angle and large-displacement scanning; micromirror designed by adopting this method is smaller than 2.5 mm×2.5 mm, the mechanical angle is greater than 5°, the vertical linear displacement can reach 425 μm, and the system response time is shorter than 10 ms; finally, test and analyze the electrothermal and electromechanical performance, frequency response and resonant frequency of the micromirror. It indicates that the MEMS micromirror, with stable and reliable performance, has a broad prospect in wider promotion and application.Keywords：electrothermal drive;MEMS micromirror;SOI micromachining;folded dual-S double-layer beam structure;vertical linear large displacement- 94
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Published：2020-08-13 -
Numerical analysis and control method for wrinkling of curved surface parts in flexible rolling forming
Abstract：Set forth the flexible rolling forming mechanism:the flexible rolling forming surface relies on the roll gap of special shape between the flexible rollers to achieve bi-directional bending of the plates during formation. Purpose:to study the wrinkling law during the flexible rolling forming process, and effectively control the wrinkling of surfaces. Take spherical parts for an example, and carry out numerical analysis on the rolling process of spherical parts with different curvature radius. The analysis results indicate that the maximum wrinkle height increases from 0.24 mm to 2.85 mm when the radius of the formed parts decreases from 1 000 mm to 300 mm. As radius of the formed parts decreases, changes to metal in the width direction of the plates will be larger; and as the plastic deformation becomes more uneven, the surface is more likely to wrinkle. The paper has also discussed the multi-step rolling forming laws, which can help effectively predict and control the wrinkles. Method:carry out the experimental verification in the tester, conduct a 3D molded surface measurement in the test pieces with optical instrument to obtain the point cloud data, and then complete the molded surface analysis in the test piece by combining the reverse surface modeling technology. The test results are basically consistent with the simulation results.Keywords：flexible rolling;3D surface;numerical simulation;wrinkling;multi-step forming;optical measurement- 53
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Published：2020-08-13 -
Automatic sun tracking system based on STM32
Abstract：To improve photoelectric conversion efficiency of solar panel, a research is conducted on the solar tracking technology and a solar auto-tracking system based on STM32 controller is designed. Considering the difference in solar movement range in the azimuth angle and altitude angle, design a sensor module in the six photosensitive areas as the photoelectric detector to ensure solar position detection in a wide range; put forward the ratio control algorithm for variable scale factors to fast detect the solar position, and combine coarse tuning mode with fine tuning mode to achieve large-angle solar position tracking; combine the photoelectric detection tracking algorithm with the solar movement tracking algorithm to achieve real-time tracking of solar position in fine weather and cloudy weather, control the solar panel in the optimal lighting position, and improve the output power. It indicates that the system designed can achieve accurate solar tracking, with an error lower than 1°. The system, with high sensitivity and stable tracking performance, helps improve the photoelectric conversion efficiency of solar panel.Keywords：photoelectric conversion efficiency;solar tracking;six photosensitive areas;photoelectric detection and tracking;sun movement tracking- 79
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Published：2020-08-13 -
Experimental research of ELID grinding on SiC ceramics based on grinding wheel wear
Abstract：Purpose:to improve the grinding wheel wear condition of SiC ceramic during the grinding process, improve the machining quality and machining efficiency of optical elements of large-caliber SiC ceramic, the ELID grinding technology is adopted in the SiC ceramic grinding experiment. Method:based on a contrastive analysis on the common grinding process, a research is conducted on the wheel grinding surface condition, workpiece grinding surface roughness, grinding force and grinding ratio during the SiC ceramic grinding process by adopting the ELID grinding technology. Results:the ELID grinding technology can keep the grinding particles in adequate sharpness after a long-time and wide-removal SiC ceramic grinding process, and compared with common grinding mode, the grinding force and grinding ratio has also been lowered to a much greater extent; but roughness of the SiC ceramic grinding surface increased slightly. Conclusion:it indicates that the ELID grinding technology can effectively alleviate the problems of grinding force increase, grinding quality decrease and short service life caused by severe grinding wheel wear; reflects the advantages of ELID grinding technology in the long-time and wide-removal SiC ceramic grinding process, and such advantages provide technical support for high-efficiency and high-quality machining of large-caliber SiC ceramic optical elements.Keywords：SiC ceramic;grinding wheel wear;ELID grinding;surface roughness;grinding force;grinding ratio- 59
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Published：2020-08-13 -
Mechanism and experiment of flexible polishing for freeform surface of plexiglass
Abstract：To improve surface accuracy of organic glass, a material removal model for the grinding and polishing process is set up based on the method for robot automation and polishing. Method:firstly, analyze and study the pressure distribution within the region where the flexible polishing disk contacts with the workpiece by adopting the Finite Element Method, and establish the material removal model when the polishing disk feeds materials along the planned area based on the Princeton's material removal theory; secondly, analyze the impact of polishing pressure, rotation speed of the polishing disk and feed speed on the material removal rate, and then study the impact of track pitch under the scanning path on the material removal evenness to obtain the optimal track pitch; finally, carry out a grinding and polishing experiment in the organic glass to verify correctness of the material removal model. Results:reasonable processing parameter and optimal track pitch can help to obtain the high-accuracy clear parts with surface roughness (Ra) of 0.01? m and without any optical defects. Conclusion:the material removal theory is of guiding significance to practical surface grinding and polishing process.Keywords：organic glass;surface polishing;flexible polishing disk;surface material removal;track pitch- 84
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Published：2020-08-13 -
A linear motor with solid horn and actuation
Abstract：To achieve miniaturization and integration of drive units for small-size equipment, a linear screw motor with exponential type ultrasonic horn is designed and made. The motor works in first-order bending vibration mode of the girder, and middle part of the stator is a quadrangular elastomer; use the SMD piezoelectric ceramic stimulation to produce space rocking motion, with the single end as exponential type ultrasonic horn, then amplify the vibration displacement and coordinate/match the rotor/stator size. The rotor screw is driven by internal thread of the ultrasonic horn to output linear displacement. A special drive circuit is designed and combined with the model machine to carry out an actual measurement in the main performances. The results indicate that when the voltage effective value is 220 V and the frequency is 15.6 KHz, maximum no-load speed of the motor is 3.3mm/s and the maximum axial force is 11 N. The motor is simple in structure, convenient for control and good in mechanical property, with a relatively higher axial force compared with motors of the same kind.Keywords：exponential type ultrasonic horn;piezoelectric drive;linear motor;electronic control unit- 52
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Published：2020-08-13 -
Simulation and experimental study on the molding process for microgrooveson optical glass
Abstract：In order to manufacture high precision optical glass microgrooves, the finite element simulation and experiment on glass molding processare carried out to reveal the glass deformation behaviorat high temperature during microgroove molding. Firstly, a modified glass-mold interface friction model is established by combining the general adhesive friction model with the Wanheim/Bay friction model, and the modified model is applied to the finite element calculation. Secondly, the high temperature viscoelastic constitutive model of glass is established, the glass microgroove molding process is simulated, and the influence of the improved glass-mold interface friction model on the forming stress is analyzed. Finally, the microgrooves are fabricated by using Ni-P plating mold. The results present that a distinct interface slip phenomenon appeared when the modified glass-mold interface friction model is applied in simulation.The element stress curve shows jitter rising trend after reaching the shear threshold value.Compared with the Coulomb friction model, the modified model can describe the interface friction characteristics of high temperature glass more accurately. The height direction replication error of glass microgrooves formed by molding process is 0.275 μm.Keywords：Microgrooves;Glass molding process;Interfacial friction;Viscoelasticity;optical glass;Plating mold- 54
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Published：2020-08-13 -
Micro-scanning control system design for piezoelectric high-precision displacement
Abstract：To realize super-resolution imaging to micro-scanning system, a high-precision displacement control system is designed on the basis of piezoelectric stack actuator and existing micrometric displacement drive platform. Hysteresis characteristic of piezoelectric stack actuator material affects accuracy and stability of system, and research is performed to modeling and compensation method of its hysteretic nonlinearity. Adopt advanced inverse model of Prandtl-Ishlinskii hysteresis nonlinearity model as feedforward controller to compensate for its hysteretic nonlinearity. Confirm parameter of inverse compensation model by testing output characteristics of micrometric displacement drive platform. Structure of inverse model is simple, and response speed of system is quick, which is beneficial to real-time control. Experimental result shows that the hysteretic inverse compensation control system can obviously decrease hysteretic nonlinearity of system and the maximum nonlinear error is 0.4 μm. System realizes accurate two-dimension positioning on the basis of micrometric displacement amplification of micro-scanning drive platform.Keywords：piezoelectric actuator;displacement micro-scanning;hysteretic nonlinearity;inverse compensation- 54
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Published：2020-08-13 -
Automatic measurement equipment for micrometric displacement of piezoelectric ceramic piece of displacement compensator
Abstract：Aimed at automatic measurement task of micrometric displacement of piezoelectric ceramic piece for laser gyroscope displacement compensator, automatic measurement equipment is developed. Three-dimensional robot is adopted in the equipment as motion frame, and photoelectric sensor is used as sensor for displacement detection and feedback control, which solves the problem of automatic motion detection, and realizes automatic operation of equipment. The vaccum technology is applied in parts pickup and fixation, which effectively avoids the occurance of accidental damage of slice parts. The high-precision inductance micrometers are used with working mode of relative measurement. As a result, the influence of part transport and placement error on measuring result is eliminated effectively. The equipment can finish the work of automatic part loading, measurement, selection and matching in batches. The experiment results show that the developed equipment improves measuring speed in more than 60 percent compared with existing measuring method, the measurement accuracy is 0.5 μm in full measuring range, the repeated accuracy is no more than 0.06 μm. Thus, the requirements of the measurement is satisfied based on the high reliability and consistency of the developed equipment.Keywords：precision measurement;piezoelectric ceramic piece;micrometric displacement measurement;automation equipment- 55
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Published：2020-08-13 -
Computational method for external heat flux of trajectory space on optical system of star sensor
Abstract：A computational method which is on the basis of Reverse Monte Carlo method (RMC method) is put forward to calculate the external heat flux on the optical system of star sensor. Firstly, the environment mapping surface is designed to coat optical system of star sensor, and the direction of external heat flux where the environment mapping surface receives is confirmed according to the given orbital parameters in different time. Secondly, radiation transfer factor between the surface of optical system and the environment mapping surface is gained by tracking the heat rays which are transmitted from the optical system of star sensor with RMC method. Finally, the external heat flux on the optical system surface of star sensor is calculated and gained. The radiation coefficients do not need to be calculated in this method. And the density of external heat flux can be gained directly. It is more convenient to handle the reflection and transmission process of these heat rays. And especially, it is available to calculate the external heat flux on the shaded component. In the simulation, two kinds of on-orbit operation schemes are designed to simulate the solar radiation heat flux, the earth infrared radiation heat flux and the earth albedo radiation heat flux accepted by the optical system of star sensor, the maximum external heat flux accepted by feature point 1,2 and 3 in scheme one respectively are 1 008.55 W/m2、956.95 W/m2、477.88 W/m2. While in scheme two, the corresponding values are 1 177.69 W/m2、1 055.55 W/m2、678.40 W/m2. The simulation results conform to the theoretical analysis, and it verifies that the proposed method is correct and effective.Keywords：Reverse Monte Carlo (RMC) method;Mapping surface;Environment heat flux;Star sensor optical system- 68
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Published：2020-08-13 -
High-pressure abrasive water jet dressing of metal bonded diamond grinding wheel
Abstract：To solve the problem that dressing of metal bonded diamond grinding wheels during the grinding process for a large aperture aspherical RB-SiC mirror, high pressure abrasive water jet dressing was investigated. The unused, worn and dressed grinding wheel topographies were observed and compared to analyze the wear and dressing mechanism. 3D surface roughness amplitude parameters of these topographies, which include Sp, Sq, Ssk, and Sku, were analyzed and comprehensive evaluated. The experiment results show that abrasive grains of the unused or the worn grinding wheel are increased and well protruded from binder after dressing, which will lead to a decrease of normal and tangential grinding force. The feed rate of nozzle have no significant effect on the 3D surface roughness of grinding wheel as the feed rate is between 0.5 to 16 m/min. The results verified the feasibility of high pressure abrasive water-jet in-process dressing of metal bond diamond grinding wheel.Keywords：high-pressure abrasive water jet;metal bond diamond grinding wheel;dressing;RB-SiC mirror;three-dimensional surface roughness- 45
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Published：2020-08-13 -
High relative density tin bronze parts directly manufactured by selective laser melting
Abstract：In order to obtain high density tin bronze parts and functional components with typical curved, thin-walled, round features manufactured by Selective Laser Melting, the influence of three key factors of laser power, scanning speed and scanning distance on the density of tin bronze parts manufactured by selective was researched. Design a three factors and four levels orthogonal experiment. And according to the results of experiment, the process parameters of parts are optimized by the method of BP neural network and genetic algorithm. The density of optimized parts has been researched by MicroCT and Archimedes drainage, and the surface topography of optimized parts has been studied by the technology of digital stereo imaging. Then a wind turbine model with typical structure characteristics has been manufactured by the optimized process parameters. The experimental results show that the laser power, scanning distance and scanning speed have important influence on the density of the laser, and the degree of the influence is weakened in turn. Optimum parameter is laser power of 177W, scanning speed of 327mm/s and scanning pitch of 0.082mm. under the process, the density that measured by experiment is 99.7%, which is nearly the same as the theoretical optimization results of 99.12%. So the error of the two results is very small. The MicroCT image shows that there is no obvious inclusions, gap and other defects inside the parts. The wind turbines model with the typical characteristics of curved surface, thin wall and round hole can be directly manufactured, and the surface of the part have no ball, crack, and other defects. Therefore, the method for optimizing molding process parameters, which is based on the orthogonal experiment and combined with BP neural network and genetic algorithm, is feasible. The relative density of parts meets the requirement.Keywords：selective laser fusion;tin bronze;Orthogonal experiment;neural network;genetic algorithm- 39
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Published：2020-08-13 -
Material removal mechanism study of ultrasonic elliptical vibration assisted chemical mechanical polishing for fiber end-face
Abstract：To describe material removal mechanism in the process of auxiliary chemico-mechanical polishing fiber end face of ultrasonic vibration, Fiber material removal model in the auxiliary chemico-mechanical polishing process of ultrasonic vibration is established; Reasonably establish mathematical model of surface appearance of polishing pad according to surface appearance of polishing pad of experimental observation; Analyze polishing particle number of two-body and three-body contact in the process of polishing and analyze fiber material removal mechanism of ultrasonic vibration of different directions in the chemico-mechanical polishing process; Respectively establish material removal model under different process after overall consideration of polishing particle, workpiece material characteristic and ultrasonic vibration characteristic; Compare experimental result of auxiliary chemico-mechanical polishing of ultrasonic vibration on fiber end face and theoretical calculation result to verify reliability of model. Result:experimental result shows that compared with ordinary CMP, fiber material removal rate of UHV-CMP, UVV-CMP and UEV-CMP respectively increases by 60%, 85.6% and 145%. Conclusion:ultrasonic vibration helps to improve material removal rate of chemico-mechanical polishing on fiber end face, and theoretical and experimental comparison results are relatively identical, which verifies reliability of material removal model.Keywords：ultrasonic ellipse vibration;chemico-mechanical polishing;material removal mechanism;fiber end face- 49
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Published：2020-08-13 -
Coupling characteristics and test on dual-excitation for large wind turbine blade fatigue test
Abstract：To improve shock excitation capacity of fatigue test of large-scale wind power blade, shock excitation system of two-point fatigue test is designed. Firstly, deduct kinetic equation of two-point shock excitation of wind power blade on the basis of Lagrange equation, and jointly construct mathematical model of two-point shock excitation of wind power blade by combining with state equation of three-phase asynchronous motor under two-phase static coordinate. Then establish simulation model by adopting Matlab/Simulink software, and numerical simulation result shows electromechanical coupling property of two shock excitation sources in the fatigue vibration process of wind power blade. Finally, a set of full-scale structural testing platform of large-scale wind power blade is constructed. Test result shows that when rotate speed of shock excitation source is set as 40rpm (being equivalent to first-order frequency in the direction of blade surface), its rotate speed and phase can be kept relatively stable; when rotate speed of shock excitation source is set as 75rpm (being equivalent to first-order frequency in the choral direction of blade, fluctuation range of rotate speed of shock excitation source is ±2rpm, and there is irregular fluctuation at phase angle, which shows that the faster the rotate speed of shock excitation source is, the severer the coupling degree between rotate speed and phase will be. Test result basically conforms to simulation result, and that is to say that when fatigue loading test of blade is performed, coupling degree of shock excitation source in the choral direction is greater than that of shock excitation source in the direction of surface. If better synchronous shock excitation effect of blade needs to be gained, intelligent decoupling control algorithm shall be adopted.Keywords：wind power blade;two-point shock excitation;Electromechanical coupling;numerical simulation;fatigue test- 51
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Published：2020-08-13 -
QCM fruit gas sensor based on PANI/SnO2 composite materials
Abstract：A fundamental frequency of 6 MHz quartz crystal microbalance (QCM) gas sensor is researched in order to monitor the fruit freshness in the process of storage, transportation and so on. SnO2 nano-materials were prepared by hydrothermal method, under the condition of p-toluene sulfonic acid (TSA) acidic, the different atomic proportions of PANI/SnO2 composite gas sensing films were synthesized by one-step in situ polymerization method and were coated on the Quartz Crystal. The gas-sensing performance test platform was built, which consisting of start-up, difference frequency, F/V and data acquisition circuits. Different compound ratio of PANI/SnO2 thin films were studied with different maturity of banana and apple released gas sensitive properties. The results show that 10% of the proportion of PANI/SnO2 gas sensor has the best performance for apple releasing gas, when the frequency change of about 1100Hz, can judge apples rot. And the 20% proportion of PANI/SnO2 gas sensor has the best performance for banana releasing gas, when the frequency change amount to around 1300Hz, can be judged bananas into maturity period. Both sensors have the advantages of high sensitivity, good linearity, fast response and good repeatability. The sensitive mechanism is analyzed preliminarily.Keywords：gas sensor;quartz crystal microbalance;ployaniline;fruit releasing gas- 68
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Published：2020-08-13 -
Contrastive analysis of modeling and compensation method of thermal error of precision machining experiment table
Abstract：To improve operation accuracy of precision machining experiment table, instrument of laser interferometer and PT100 instrument etc. is adopted to measure position error of X and Z axis of four-axis numerical control platform and temperature. Varying pattern between position error of X and Z axis and temperature is analyzed and gained. Respectively employ support vector regression (SVR), RBF and BP neural network method to establish thermal error model of X and Z axis and contrastive analysis is performed. Result shows that matching performance and generalization ability of SVR model are obviously greater than those of RBF and BP model. Error compensation experiment is performed according to thermal error model of SVR, RBF and BP and experimental result shows that position error of X axis of numerical control platform decreases by 92.3% to the largest degree, position error of Z axis decreases by 90.3% to the largest degree, and predictive capacity, compensation precision and robustness of SVR are obviously greater than those of RBF and BP neural network method.Keywords：SVR;BP neural network;RBF neural network;error compensation- 54
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Published：2020-08-13 -
Design of piezoelectric micro displacement actuator
Abstract：To realize bi-directional symmetry drive when piezoelectric actuator journey is improved simultaneously, rhombus piezoelectric micrometric displacement actuator on the basis of triangular displacement amplification theory is put forward. Analyze movement and amplification theory of actuator, and establish theoretical static force model of actuator on the basis of piezoelectric equation. Key parameter of magnifying mechanism is introduced in detail. When journey is 105 μm, error between magnification times of actuator and theoretical value is 5.69%. Experiment rigidity of model machine is greater than theoretical value. Experiment model machine is manufactured. Output characteristic experiment under open loop condition shows that under static force condition, average rigidity of actuator in actuation direction is about 0.62 N/μm and the maximum unidirectional free elongation displacement can be 42.2 μm(under 160 V voltage), and the maximum load is 27.4 N(under 160 V voltage), and all of them are smaller than theory resolution (error does not exceed 24.2%). But its displacement-force-voltage relationship conforms to deduction of theoretical model:output displacement is in direct proportion to control voltage and load. Under non-static condition, hysteresis effect of output displacement is obvious and bi-directional actuation performance is symmetrical. The maximum displacement can be 99.1 μm (under 180 V voltage), and displacement decreases slowly with increasing of frequency. Starting characteristic of actuator is good, being able to realize millisecond-level quick response (about 5.4 ms), and it is quick and stable. When control signal of actuator is step wave signal and when step increment voltage is 0.2 V, the minimum step-by-step quantity is 0.1 μm. Actuator has symmetrical bi-directional actuation characteristic and good starting characteristic, being applicable to precision positioning or condition where repeated drive characteristic symmetry is required.Keywords：overlaid piezoelectric ceramics;static force model;bi-directional drive;starting characteristic- 59
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Published：2020-08-13 -
Forward displacement analysis for 5TSP-PPS parallel mechanism of large aperture grating tiling
Abstract：To meet requirement of heavy load, high precision and high stability of heavy caliber grating tiling device, 5TSP-PPS parallel mechanism is put forward, and screw theory is adopted to analyze mechanism theory of the mechanism to realize two-dimension movement and three-dimension movement (2T3R) of space. Take TS rod length as constraint condition and establish constraint equation on the basis of vector method and deduct nonlinear equation system of forward position and inverse position. To improve computational efficiency of forward position, apply simplified Newton method to forward position analysis. Numerical example shows that:compared with Newton, simplified Newton method can improve computational efficiency of forward position. Attitude error between computational result of forward position and given pose is lower than 8.5×10-9 μrad and location error is lower than 8×10-10 μm, which verifies correctness of forward position analysis of 5TPS-PPS parallel mechanism. The research lays a foundation for further study of calibration of new heavy caliber grating tiling device, error analysis and real-time control of closed position loop.Keywords：grating tiling;parallel mechanism;screw theory;forward position analysis;simplified Newton method- 60
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Published：2020-08-13 -
Prediction and control of surface roughness for high speed machining of titanium alloy TC4
Abstract：Surface roughness of part is an important parameter to measure surface quality of workpiece. In actual processing, impact factor of surface roughness is complex and uncertain, but in many factors, cutting parameter has obvious effect on surface roughness, and it can be controlled manually in processing. Therefore, selecting proper cutting parameter and improving surface quality of workpiece are a very important tasks. Uniform design method is adopted in this paper to perform cutting experiment of titanium alloy TC4. Measure surface roughness of workpiece with Marl MarSurf M 300C precise surface roughness tester of Germany, and then employ nonlinear regression solution technology to establish prediction model of surface roughness. Inspect fitting degree of prediction model and significance of each independent input parameter by adopting analysis of variance. Perform contrastive analysis of prediction error. Experimental result shows that prediction error of regression prediction model established is as low as 0.019% with feature of high precision and strong reliability etc. Finally it puts forward to take the minimum surface roughness as target, use genetic algorithm to optimize solution technology and establish optimization model of cutting parameter. The research result provides theoretical basis for prediction of surface roughness processing and provides reasonable choice of cutting parameter to improve surface quality of processing.Keywords：surface roughness;TC4;prediction;nonlinear regression;genetic algorithm- 38
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Published：2020-08-13 -
Fast scan method of digital speckle and three-dimensional human body
Abstract：To make up for disadvantage of traditional human body scan way that it is difficult to realize the fast and whole body scan, fast scan method of digital speckle and three-dimensional human body is put forward. Concerned matching algorithm of digital image on the basis of seed point is put forward to solve initial value of nonlinear optimization of concerned matching. Adopt large visual field and multiple camera calibration strategy based on photogrammetry, and reestablish three-dimensional point cloud of human body according to binocular stereoscopic vision theory. Make use of VS2010 development environment, and develop XTBodyscan three-dimensional human body fast scan system. 4 human body scans and 10 groups of system calibration experiments are implemented to verify feasibility and calibration accuracy of the scan method. Experimental result shows that method in this paper can finish the whole body scan of human body within 0.1s and calibration error is lower than 0.1pixels. Three-dimensional human body scan of the whole body with fast speed and detail feature kept can be realized, having advantage of non-contact, no damage and high experience, which provides an effective method for fast 3D reverse engineering of human body.Keywords：human body scan;seed point;speckle matching;camera calibration;three-dimensional point cloud- 59
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Published：2020-08-13 -
Accelerated 3D reconstruction method from image sequence based on inertial measurement unit
Abstract：Against the high complexity of posture calculation in Structure from Motion (SfM) algorithm, this paper proposed a method of accelerated 3D reconstruction of sequence image based on inertial measurement unit (IMU). Firstly, the captured moments of sequence image were caculated by accelerometer. Then,the initial orientation matrix and position information of mobile terminal at the captured moments were resolved according to moments and IMU's output data. Finally, sensor noise was removed by bundle adjustment, combined with global consistency rotation, the camera's pose information corresponding to sequence image were generated. Since we obtain the camera's position and orientation by the IMU's information, and the process of computing camera pose by traversing matching feature points in SfM algorithm was replaced, and the time consumption of 3D structure recovery was reduced. Experimental results show that the speed of 3D structure recovery in SfM algorithm is improved by 3 times, and the error between the model calculated length and the actual length is within 4.9%. The proposed approach effectively solves the time-consume problem with the structure from motion algorithm, it can be used for the rapid reconstruction of large scale scene.Keywords：Inertial measurement unit;Accelerated 3D reconstruction;Posture calculation;sequence image;Structure from motion- 45
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Published：2020-08-13 -
Fundamental matrix estimation for 3D reconstruction towards multi-perspective views
Abstract：In consideration of the relatively low precision and stability in the existing methods for Fundamental Matrix Estimation(FME), a FME method for 3D reconstruction of multi-perspective views is put forward. Firstly, sampling strategy based on Simulated Aneal Sampling (SAS) is proposed. Specifically, the candidate feature points are divided into different categories, and the sampling is fulfilled by extracting the feature point pair from each category in different probability; Furthermore, an interior points filtering algorithm is proposed based on re-projection error of matched points pair; Finally, a FME algorithm based on SAS is designed. It indicates that the precision and stability achieved by this solution is approximately about 10 times higher than that of state-of-art algorithms, and such solution can effectively improve the precision rate of three-dimensional reconstruction.Keywords：basis matrix;Simulated Aneal;sampling method;three-dimensional reconstruction- 44
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Published：2020-08-13 -
Sub-pixel subdivided model for retro-reflection spot positioning algorithm
Abstract：With regard to the measurement for vibration and flatness of large-scale space truss structure, the demand in large-scale and long-distance space positioning measurement is very common, and in consideration of the measurement characteristics of long distance, large scale and high precision, spot positioning is regarded as one of the optimal methods. In this paper, a kind of round spot based on retro-reflection target, with a relatively large target-background contrast, is introduced; and related algorithm such as computer vision is adopted to realize the long-distance positioning with precision subdivision. By virtue of the Canny edge detector, edge extraction is conducted in the retro-reflected spot and coordinate of the spot center is worked out through least-square fitting in the edge, thus achieving the positioning purpose. Through subdivided modeling for the Canny edge detection error and least-square fitting precision, an analysis is conducted on the repeatability error bounds of the spot positioning, and a reliable estimation for repeatability precision of spot positioning in this algorithm is provided. In the experiment where LED and 532 nm laser is taken as the light source, the repeatability error bounds of the center positioning 3-sigma are respectively ±0.30 mm and ±0.57 mm, which are consistent with the √n estimate obtained in the subdivided model. Precision subdivision of the extracted edge by Canny edge detector through the least-square circle fitting can satisfy the requirement for high precision in long-distance space positioning.Keywords：spot positioning;retro-reflection;Canny edge detector;least-square circle fitting- 35
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Published：2020-08-13 -
Automatic extraction of characteristic light stripe in vision measurement of smooth metal surface
Abstract：In order to achieve the measurement of smooth metal surface with the structure-light vision measurement method, it is required to extract image of the characteristic light stripe. In this paper, measurement for diameter of a motor car axle is taken as an example for analysis and research on Region-of-Interest(RoI) of the characteristic light stripe and the method for its automatic extraction. first, the corrosion template is designed in accordance with imaging features of the axle light stripe; second, the RoI of the characteristic light stripe image is obtained by means of the morphological image processing technique, namely the corrosion technique and morphological reconstruction technique, etc., and then the reference line of the light stripe is preliminarily extracted in the RoI; finally, the normal vector of each point is calculated based on the referenced line, and then the center of the characteristic light stripe is confirmed by working out the ball center in each normal vector. Experimental results indicate that RoI of the characteristic light stripe can be quickly and accurately confirmed, thus the characteristic light stripe can be extracted automatically. The standard deviation of the axle diameter calculated based on center coordinate of the characteristic light stripe shall be less than 0.015 mm. The method completely satisfies the requirements for extraction of characteristic light stripe in the vision measurement of motor car axle, and such requirements include fast speed, high precision, good stability and strong anti-jamming capacity.Keywords：metal surface;machine vision;structure light;characteristic light stripe;area-of-interest- 50
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Published：2020-08-13 -
New detection method for coronal mass ejection capable of dark cavity processing
Abstract：A k-mean-value based identification method capable of effectively processing the dark cavity was put forward to effectively identify the Coronal Mass Ejections (CMEs) in wide-angle spectrometric coronagraph images. Firstly, median filter was adopted as preprocess algorithm to eliminate the noise, and then difference images was preliminarily classified through the k-mean-value clustering algorithm, distribution characters of each category were classified; The first classification was identified according to the distribution characters, thus the highlighted CME image and dark cavity CME image were successfully identified. Secondly, partitioning strategy and polar coordinate transformation were carried out in the coronagraph image identified with no CME through twice clustering method, and the k-mean-value clustering algorithm was applied in above image, statistics of the twice clustering results was made, and the secondary classification by virtue of the distribution characters was completed. The results show that the method can effectively detect CME image in the coronagraph image, and can directly indicate and display the CME regional point, especially for thoes with dark cavity. The given measurement threshold based on highlighted CME is 200~250 for the center of third classification, while that based on dark cavity CME is lower than 120 for the center of the first classification, and the pixel point within the classification is between 1 000 and 30 000.Keywords：CME;k-mean-value;dark cavity;partitioning;polar coordinate- 57
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Published：2020-08-13 -
Comparative study on camellia oil & olive oil quality and quantitative analysis of adulteration
Abstract：A comparative study on the quality of camellia oil and olive oil is carried out by using the Raman spectra technique, and then, through the chemometrics method, the modeling and predictive analysis on the adulterated camellia oil and olive oil are implemented. In this paper, the study is conducted on rapid nondestructive testing of the adulterated camellia oil and olive oil by virtue of the Bruker laser confocal Raman microscopy of Germany. Experiment process:the rapeseed oil, peanut oil, soybean oil, cottonseed oil, corn oil and sunflower seed oil are respectively added into the camellia oil and olive oil as 6 different doping proportions, 36 spectra for each classification are collected, then the 900~2 900 cm-1 wave band data with higher signal-to-noise ratio and stronger characteristic peak are selected for preprocessing with the two methods including 1st derivatives and Savitzky Golay Smoothing, and the partial least-square (PLS) model is created. Through a comparison of the model effect, Savitzky Golay Smoothing is confirmed to be the optimal preprocessing method; correlation coefficient (Rp) and root-mean-square error (RMSEP) for camellia oil adulteration are respectively 0.994 and 1.79%, while Rp and RMSEP for olive oil adulteration are restively 0.989 and 3.05%. Finally, the optimally-processed data is taken as the basis for a principal component regression (PCR) quantitative analysis, but it's predictive effect is not as good as the PLS quantitative analysis. The experiment indicates that the prediction for camellia oil adulteration is more accurate than that for the olive oil, and in the same conditions, changes in the adulteration content of camellia oil are more regular, with more practical preventive measures than oil adulteration. Hence, in similar nutritional conditions, camellia oil serves as a better choice than olive oil for production and processing, as well as sales and food.Keywords：camellia oil;olive oil;adulteration;Raman spectrum;partial least squares (PLS)- 38
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Published：2020-08-13 -
Application of the nonlinear mapping method in the foot scanner's automatic camera calibration
Abstract：To solve the problem of cumbersome steps of camera calibration in the three-dimensional(3D) foot type in measurement system, this artical proposes a calibration method based on Double-camera system. On the basis of the structure and working principle of 3-dimensional foot type measuring system, it designs the camera calibration method based on the calibration target, and improves the traditional calibration target in the process. The automatic corner detection technology and Harris corner detection algorithm and template matching algorithm are adopted for testing, without manual intervention. The image geometric correction technique is used to realize more accurate extraction in the process. At the beginning of the calibration, the calibration block are put on the light plane and a picture is captured by each camera. It is convenient and quick. Finally, two nonlinear equations are got through coordinate mapping from the image plane to light plane, then the mapping relationship between images can be solved by using above equations. The experimental results show that calibration error basically maintained in 0~1.2 mm, and the average error is 0.44 mm. Through the foot 3 D reconstruction graphics, it can be seen that foot shape gets good reconstruction.Keywords：corner detection;calibration target;corner detection;geometric correction;image maps- 58
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Published：2020-08-13 -
High-precision spring 3D visual inspection and comprehensive error comparison
Abstract：In order to achieve precision measurement of the spring parameters and error comparison, three-dimensional spring multi-parameter measurement system was designed. A three-dimensional spring error comparison theory was established. Algorithm such as pinstripe exponential growth stereo matching technology, pattern recognition method for rotational inertia based on image normalization, linear least square method were applied in this paper. First, high-precision cyclic coded targets were applied in binocular camera calibration, Next, take advantage of structured light stripe technology, it was implemented to stereo matching. Then, Normalized moment of inertia was introduced for feature extraction to obtain a three-dimensional point cloud of the spring. The chord method was used to reduct noise, and the STL model was obtained by filtering. And then the three-dimension length and cylindricity of the spring wre evaluated through Cylindrical fitting and plane fitting of 3D point choud. Finally, a comprehensive spring three-dimensional error comparison theory was set up to comply a rapid identification of unqualified spring. The results show that three-dimensional point cloud detected uniquely associated with the object and the depth of field can reach 300 mm, thus avoiding errors due to the changes in the relative position of the camera and the spring, and the combination of two-dimensional image and three-dimensional detection, so that the accuracy can reach 0.05 mm. The spring measurement system has a faster detection speed due to the comprehensive spring three-dimensional error comparison theory. The proposed three-dimensional visual spring detection method is high-precision, non-contact and non-destructive measurement. The method also has advantage of stable and fast detect speed which meets the requirements of online testing.Keywords：computer vision;normalized rotational inertia;cylinder and plane fitting;spring precision measurement;3D-error comprehensive comparison theory- 62
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Published：2020-08-13 -
Fast single image dehazing method based on illumination veil elimination
Abstract：An unified approach based on atmospheric scattering model is proposed to handle such degraded images with the strategy that gracefully bridges the gap between un-uniform illumination and hazy images. According to dark channel principle, the atmospheric veil function is caculated, and the residual image removing atmospheric veil is obtained. Then, based on illumination-reflection model and bright channel theory, with joint bilateral filter, illumination component of residual image is obtained and removed. So the reflection components which has nothing to do with illumination is obtained. Meanwhile, influence of hazy and illumination is removed. The proposed approach simultaneously dehazes images and enhances contrast, and the global atmospheric light is not necessary to be calculated to avoid the risk of errors. Experiment results on a variety of outdoor degraded images demonstrate that the proposed method achieves short computation time and good restoration for visibility and color fidelity.Keywords：defogging for single image;prior shadow channel;luminance curtain function;uniting bilateral filter;image quality evaluation- 57
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Published：2020-08-13 -
Satellite image restoration based on measured vibration information and requirements
Abstract：Aiming at the practical application problem of restoration for degraded image owing to satellite vibrations, a restoration method based on measured vibration information and the specification requirements were proposed. Firstly, effects of vibrations on image quality were analyzed based on imaging physical-process of TDICCD push-broom system. Then the methods of image restoration and corresponding parameter calculation were presented. Secondly, influence law of vibration measurement error on restored image quality were discussed in the cases of different vibration frequencies, amplitudes and TDIs. Finally, the quantitative relation between the measurement error and restoration performance was established by experiments. Experimental results indicate that the restored images can satisfy the practical requirement that SSIM is higher than 0.9 and geometric distortion is less than 0.1, when the measurement error should be less than 0.05 pixel, and vibrations with frequencies over 150 Hz should be isolated.Keywords：Satellite vibration degradation;image restoration;vibration measurement;specification requirements- 28
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Published：2020-08-13 -
An authentication method based on perceptual hashing and watermarking for remote sensing image
Abstract：Aiming at the requirements of complete authentication of remote sensing image in application,an authentication method based on perceptual hashing and watermarking for remote sensing image is proposed. The key of the method is to overcome the mutual influence between perceptual hashing and watermarking. Firstly, the remote sensing image is partitioned into girds which are then preprocessed; secondly, horizontal and vertical middle frequency coefficients are extracted by DWT(Discrete Wavelet Transtorm) and treated by PCA(Principal Component Analysis) to generate perceptual hash value, which is embedded into the diagonal middle frequency coefficient based on interleaving strategy. The authentication process is implemented via the comparison between the extracted perceptual hash value and the reconstructed one. As the method organically combined perceptual hashing and watermarking, it overcomes the defect that the perceptual hashing based authentication needs extra channel to transmit hash values. The experiments demonstrate that the Hamming distance of the tampering tests is between 0.218 7 and 0.398 4, thus the detailed tampering of the image can be effectively detected, and the average PSNR of the grids with perceptual hash value embedded is about 38 to 39, which means the availability of the image is not affected.Keywords：remote sensing image;authentication;perceptual Hash;digital watermarking;interleaving strategy- 41
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Published：2020-08-13 -
Machine visual measurement of ship draft
Abstract：A measurement method of ship draft based on image capture and analysis is put forward to overcome adverse effect of storm and subjective factors in manual observation method. Water gauge image capture system by taking wall-climbing robot as carrier with internet protocol camera. The system can complete water gauge photographing by going across side plate with complex surface under the control of panel personal computer. High-definition image with several wave periods can be collected successively(1600 pixel×1200 pixel). Pre-treatment and distinction to water-gauge character is implemented in image based on morphology and neural network algorithm, which effectively improves distinction degree of several similar characters:"6", "8" and "9". At the same time, it can distinguish waterline in image by color image segmentation algorithm. Ship draft can be confirmed by comparing relative location of waterline on quantization water gauge and thus successfully eliminate interference of false waterline caused by wave infiltration and realize self-motion determination of location of waterline. Experiment shows that final distinguishing accuracy of this method can reach 1 mm, which is obviously higher than 5 mm that can be reached by artificial visual observation method. Besides, the necessity to reduce storm interference through applying comprehensively multiple image data is proved by making use of data comparison of field measurement.Keywords：ship draught;Wall-climbing robot;machine vision;neural network;color image segmentation- 70
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Published：2020-08-13 -
Phase unwrapping algorithm based on three-wavelength phase shift profilometry
Abstract：Aiming at problems of low measurement speed and limited measurement range for method of multi-wavelength phase shift profilometry, a three-wavelength phase shift profilometry was presented to realize the measurement of color three-dimensional object with step change on surface. Direct problem of equivalent wavelength and wrapped phase of three-wavelength phase shift profilometry was introduced. Then, starting with the phase solution of the equivalent wavelength, and therefore phase unwrapping equations of three independent light waves were deduced. By analyzing phase noise gener ation reasons, phase denoising method based on unwrapping phase was presented. Experimental results show that average measurement accuracy of the method is 0.018 mm; processing time of ordinary desktop computer is 0.308 s. By comparing measurement precision, measurement speed, algorithm stability, range of adaptive light source and other performances, it is proved that the proposed method is more superior to the commonly used gray code methods and multi-wavelength phase shift profilometry at present.Keywords：phase shift profilometry;multi-wavelength;phase unwrapping- 61
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Published：2020-08-13 -
DC position close-loop system of spectrometer by feed-forward correction
Abstract：In this paper, driving mechanism of spectrometer mechanical system was taken as research object, and DC torque motor and magnetic spin encoding were adopted. On the basis of above, DSP F2812 was used to designan position closed-loop control system to take the place of the original open-loop stepper motor system. It can realize the function of stepper system that the wavelength of light splitted by optical-splitting system increase 1 nm, while motor runs angle displacement 3.6°. The accuracy of angle displacement is 0.15°. First, operating principle and installation of magnetic spin encoder were presented, and driving circuit and limited position mechanism were also designed. Then according to system design index, all kinds of control algorithms for DC motor were investigated. Thus, the feed-forward correction PID control strategy suitable for the system was proposed. Finally, the reliability of DC system was confirmed via experiment. Taking the experiment results as reference, an compensation algorithm for piecewise control was used to solve the problem of period interference cused by the low coaxiality between motor axis and screw axis. Experimental results indicate that the accuracy of angle displacement can reach to 0.15°. The position closed-loop system runs reliably, critically and has strong anti-interference ability so that losing step phenomenon of open-loop stepper motor system is avoided efficiently.Keywords：Spectrometer;DC torque motor;magnetic spin encoder;DSP;feed-forward correction;limited position function- 47
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Published：2020-08-13 -
Calibration of inner orientation elements and distort correction for large diameter space mapping camera
Abstract：In the applications of large diameter space mapping camera system, the calculation of inner orientation elements and the distortion correction are the important factors, and can affect the positioning accuracy. In order to improve the accuracy of the system, distortion feature was explored and analyzed in this paper. According to the characteristic of noncentral symmetry distortion image of large diameter space mapping camera, a method which uses improved two-dimension Lagrange interpolation was provided to correct the distortion of the system. First, a number of samples dots were taken on the two-dimensional image, Then the corresponding positions of the dots before and after correction were obtained through experiments, and these samples dots were used to determine the position of image dots with assistance of two dimensional Lagrange interpolation. In terms of two channels in the system, the accuracy of distortion correction is within 0.37 pixel by utilizing this method. This method overcomes the deficiencies of the traditional methods of distortion correction in terms of the complex calculating process of correcting distorted image and inaccurate corner of image, which brings universal significance and widespread practicability towards its counterparts.Keywords：large diameter mapping camera;inner orientation element;distortion correction;two-dimensional Lagrange's interpolation- 72
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Published：2020-08-13 -
Surface detection method with line structured light in complex environment
Abstract：Specific to the requirements of high precision 3D measurement in complex environment, starting from improving the calibration accuracy of vision sensor system, a kind of surface detection method with line structured light was put forward. Firstly, round target with high accuracy and flexible 3D target mode were used for calibrating the camera; after obtaining all intersection points coordinates of optical plane and target, mapping matrix from the light plane to the image plane was catculated through nonlinear optimization; then the calibration of line structured light sensor system was completed; light stripe was taken with the aid of proportion of red component in true color image and gray centroid method; lastly, according to local minimization criterion, fairing connection for detected light stripe was carried out. In each iteration, change the current point as spatial point set and the final position for center point of light stripe was obtained. Experimental results show that this method has relatively high calibration accuracy; mean error of camera reprojection is 0.102 pixel; mean longitudinal error of measurement result is 0.0132 mm; precise light stripe can be obtained so as to provide an effective method for surface detection in complex environment.Keywords：Line structured light;calibration;fairing;surface detection- 50
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Published：2020-08-13 -
Design and realization of laser detection signal traceability system with shearing trace
Abstract：Specific to disadvantage of current image and 3D scanning method difficult to make effective and rapid traceability shearing tool through trace, a set of laser detection signal traceability system with shearing trace was designed and realized; The system consists of three parts including motion control subsystem, laser detection subsystem and microscopic imaging subsystem. Through clamping cable breakage, firstly, single point laser displacement sensor was controlled to pickup surface characteristic signal of linear trace of shearing; secondly, wavelet decomposition was used to carry out noise reduction for pickup signal and obtain the signal after noise reduction. Variance diversity factor among signals was adopted to perform similarity coincidence degree matching of trace characteristic; and gradient descent method was used to implement parameter machine learning, and construct the corresponding cost function; by constant iteration, make cost function value minimum and finally realize the rapid traceability of shearing tool. System efficiency was verified through the actual shearing traces and multiple sample matching test. Batch traceability test for 25 groups of test data based on 1 000 groups of samples was put forward. Experiment results show that total time consuming is about 1.5 s; correct traceability rate is 98%; the experiment proves that this system has accuracy and validity for laser detection signal traceability system with shearing trace.Keywords：shearing tool;laser detection;gradient feature;machine learning;wavelet denoising- 51
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Published：2020-08-13 -
Adaptive dual qubit state median filtering method
Abstract：In order to improve the adaptive ability of the quantum median filtering method to the illumination variations, a novel median filtering method based on the dual qubit state is proposed. The distribution probability of the pixels in the image is determined according to the grayscale distribution information. And the normalized distribution probability is determined as the probability function of the quantum bit states. In this way, the filtering method has good adaptive ability to the illumination variations, and the filtering performance can be improved. The method is used to filter noise in the images under the normal, low and high illumination. Simulation results show that the method can get better filtering result to the salt and pepper noise than the other median filtering methods, and the method is also superior to others on some objective evaluation criteria, such as the peak signal to noise ratio, the normalized mean square error, and the structural similarity. For the images with 50% noise, the peak signal to noise ratio of the method can be enhanced by 2.13%, 2.71% and 3.22%, the structural similarity can be enhanced by 1.52%, 1.82%, 2.08%, and the normalized mean square error can be reduced by 11.85%, 15.70%, and 15.65%.Keywords：quantum;double-quantum bit state;median filtering;salt and pepper noise- 53
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Published：2020-08-13 -
Digital image correlation method based on hybrid genetic algorithm
Abstract：In consideration of features presented of relatively weak local search ability, relatively low algorithm accuracy, etc with Genetic Algorithm(GA) applied to digital image correlation method, Conjugate Gradient(CG) method with strong local search capability was introduced; with the principle of complementarity, hybrid genetic algorithm was designed to improve the accuracy and stability of digital image correlation method. Firstly, according to different binding modes of CG and GA, three kinds of effective CG-GA hybrid algorithm were presented:embedded CG hybrid algorithm, elite CG hybrid genetic algorithm and parallel CG hybrid genetic algorithm. Then, principle analysis for these three algorithms was carried out. Next, based on simulated speckle pattern of preset displacement, contrast experiment between the above three algorithms with same parameter and standard RGA(Real-code Genetic Algorithm) for subarea matching search was designed. Lastly, Experimental results taking u direction as an example show that:mean error of embedded CG hybrid genetic algorithm is reduced by 69.52% compared with standard RGA algorithm with error fluctuation also reduced and relatively big calculation consumption; solution accuracy and stability of elite CG hybrid genetic algorithm and CG hybrid genetic algorithm are greatly improved; mean error between the two is reduced by 98.43% compared with RGA with high accuracy. In the digital image correlation method, the latter two hybrid algorithms are recommended for subarea matching search.Keywords：Image measurement;digital image correlation method;genetic algorithm;conjugate gradient method;subarea matching- 64
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Published：2020-08-13 -
Maker detection and pose measurement using a cooperative target
Abstract：When mechanical arm arrests target, relative pose between target and hand-eye camera of arm is required to be obtained with real-time. By using image coordinate of mark points of cooperative target, P3P algorithm was adopted to realize high precision calculation of relative pose. Firstly, circles and straight lines of cooperative target were rapidly identified and the area of target circles was determined. Secondly, target area was divided into many square windows with mutually overlapping; with the highlight of each window as candidate point, circular feature of mark point was applied to eliminate illegal points by combining with various conditions, while three legal mark points were kept so as to determine center coordinates of the mark point finally. Lastly, combine with dimension information of participated target in camera and obtain relative pose with P3P algorithm. Simulation results show that the accuracy rate of the mark point identification is higher than 99%; rotation error of pose calculation is less than 0.1°; translation error is less than 0.5mm. In actual experiment, the above parameters respectively are 97%, 0.2° and 1mm. Operation of the algorithm is simple with high speed, high accuracy and high precision, applicable to high accuracy real-time monocular pose measurement of industry, agriculture, aerospace and other fields.Keywords：computer vision;monocular vision;hand-eye camera;P3P;circle detection- 93
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Published：2020-08-13 -
Finger vein image deblurring method based on skin scattering models
Abstract：Aiming at the image blur in the near-infrared finger vein recognition, an algorithm for restoration of the finger vein image based on elimination of the skin scattering was put forward. A scattering model against near-infrared light during the collection of finger vein image was established through experimental analysis on the skin optics. Based on the model, the point spread function of the finger vein image was adaptively estimated and then employed to restore the finger vein image by using Wiener filter. Three vein images were restored quantitatively by the proposed algorithm. The result shows that the average gradients of edge of the three images increase to 7.636, 6.877 and 6.750 respectively. Compared with POSHE algorithm, CLAHE algorithm and high-frequency emphasize filter algorithm, the width and structure of the restored vein image is more consistent with those of the original image with the minimum shadow and distortion and the highest signal to noise ratio.Keywords：image processing;finger vein recognition;vein image restoration;image enhancement;deblurring;Point Spread Function(PSF)- 37
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Published：2020-08-13
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