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Issue 5 ， 2014
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LED-based projection light source for solid-state volumetric true-3D display
Abstract：According to the needs of solid-state volumetric true-3D display for high brightness and adjustable color temperatures, a projection light source with high power and single chip Light Emitting Diodes(LEDs) was designed. The brightness of the projection light source was computed theoretically. The results were then corrected according to the spectrum curve of a Liquid Crystal(LC) shutter. With the considerations of life and heat dissipation, the projection light source with high-power RGB LEDs and a white LED was put forward. Based on the optical characteristics of the chosen LEDs, the refraction-and-reflection mixed method was applied to the design of collimating lens. Both simulation and practical test were performed on the projection light source. The experimental results show that the divergence angle of the LED has been reduced from ±75°to ±20° after applying the collimating lens. A 3D display prototype was developed. The practical luminance on the LC shutter close to observers reaches 149 cd/m2. The prototype presents the merits of no perceived flickers and strong 3D feeling, as well as the shortcoming of a smaller viewing angle. The proposed light source satisfies the requirements of solid-state volumetric true-3D display.Keywords：true-3D display;solid-state volumetric display;Light Emitting Diode(LED);projection light source- 47
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Published：2020-08-13 -
Retrieving O/N2 technique from ionospheric FUV dayglow emissions
Abstract：How to obverse the far ultraviolet(FUV) dayglow emission from space in remote sensing was explored to provide a method for monitoring of the upper atmosphere.On the basis of data processing for observation signals of payloads on the meteorological satellite FY-3, an O/N2 retrieval method by use of the Lyman-Birge-Hopfield(LBH) band in the range of 140-180 nm and the OI 135.6 nm dayglow emissions was researched.By analysis of the characteristics of 140-180 nm and the OI 135.6 nm dayglow emissions, it proves that the 135.6/LBH is correlated with solar activity.Then, the effects of the solar activity on the O/N2 retrieval curves were investigated, and the results show that there are large deviations between the retrieval curves with different solar activities, so the solar activity effect must be removed in the O/N2 retrieval method.This work provides a solid basis for the development of the O/N2 retrieval method prepared for data processing of instruments on FY-3.Keywords：atmospheric optics;Far Ultraviolet(FUV) emission;135.6/LBH dayglow emission;O/N2 retrieving- 57
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Published：2020-08-13 -
Calculation and optimization of light extraction efficiency for integrated LED
Abstract：On the basis of Monte Carlo simulation, the influence of chip types, sizes, spacing, numbers and layouts on the energy efficiency of a GaN-based Light Emission Diode(LED) integrated packaging COB(Chip On Board) device was analyzed. The calculation results show when the chip spacing is less than 200 μm while the other parameters are fixed, the face-up chip COB LED has the lowest energy efficiency, and that of the flip chip COB LED comes second and the vertical chip COB LED provides the highest energy efficiency. Moreover, each energy efficiency of these three kinds of COB LED devices tends to saturation when the chip spacing is larger than 200 μm. The increase of the chip size or the decrease of the chip amount can improve the energy efficiencies of the face-up COB LED and flip chip COB LED, while the energy efficiency of the vertical chip COB LED keeps almost a constant. The substrate patterning can improve the energy efficiency of face-up chip COB device with the same size or layout, however it deteriorates that of the flip chip COB device. It is concluded that the percentage of the light emitted from the side surface of the chip and the material-absorption among adjacent chips have a decisive influence on the energy efficiency of the three types of COB packaging devices. As for face-up chip COB LED, a diamond-shaped layout of the chips was presented, and the simulation result shows that the energy efficiency can be increased by 6.2% as compared with that of conventional square chip layout.Keywords：Light Emitting Diode (LED);integrated package;Chip on Board(COB);light extraction efficiency;Monte Carlo method- 55
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Published：2020-08-13 -
Generation of supercontinuum spectra from acousto-optic Q-switched nanosecond fiber lasers
Abstract：For the shortcomings of current schemes to generate laser supercontinuum spectra, an acousto-optic Q-switched nanosecond all fiber laser is established.The laser shows its central wavelength at 1 064.3 nm, repetition rate of 20 kHz and a pulse duration of 250 ns. After primary amplification, the output power is 13.02 W.When the amplified pulse is launched into a self-made high power Mode Field Adaptor(MFA), the signal light output can be 10.7 W and the coupling efficiency is up to 82.2%.After the MFA is spliced with a piece of Photonic Crystal Fiber(PCF), the output supercontinuum spectrum with an average output power of 5.43 W can be obtained at a wavelength range from 900 nm to 1 700 nm.As the Acoustic Optical Modulator(AOM) in the experiment has a wider pulse duration, which leads to a lower peak value of pump light and a lower nonlinear effect, so that the supercontinuum spectra do not include the visual part.It suggests that the AOM with narrower pulse duration should be used to generate high peak power to widen the spectral bandwidth and flatten the supercontinuum spectra.Keywords：acousto-optic Q-switch;photonic crystal fiber;supercontinuum spectrum;fiber laser- 60
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Published：2020-08-13 -
Properties of germanium films and their applications to photon counting imaging detectors
Abstract：To improve the performance of the charge induce layer in a photon counting imaging detector and to enhance the imaging quality of the photon counting imaging system, different thickness Ge films were deposited by Radio Frequency(RF) magnetron sputtering and Direct Current(DC) magnetron sputtering,respectively. The X-ray Diffraction(XRD),Scanning Electron Microscopy(SEM), surface profiler, and the four-point probe surface resistance tester were used to analyze and characterize properties of the films deposited by two methods mentioned above. Research shows that both the Ge films are amorphous structures,and the Ge film prepared by DC is sparser than that prepared by RF, and the resistivities of Ge films with different thicknesses prepared by DC are greater than that of the films deposited by RF. The experiment indicates that the thicker the film, the more stable the electrical properties. Imaging performance of the detector with the Ge film on different sheet resistances is compared experimentally, and it shows that the imaging performance is not only excellent,but also stable within hundreds of MΩ/□, but when the sheet resistance is higher than 2 GΩ/□, the resolution of the system will be reduced.Keywords：photon counting imaging;magnetron sputtering;amorphous Ge film;charge induce layer- 70
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Published：2020-08-13 -
Laser assisted cutting of silicon steel on cold rolling production line
Abstract：Laser assisted trimmer side cutting technology was studied to overcome the problems such as micro cracks, stress, burrs and edge waves existing in a cold rolling production line of silicon steel side cutting. A finite element analysis model for the laser hearting temperature field was established, the loading form of a heating source was determined and influences of various processing parameters like laser powers, spot sizes, and laser incident angles on laser assisted heating sheet materials were discussed according to the actual process of a cold rolling production line.These processing parameters were optimized in experiments.It is proved that the temperature is about 100℃ when the laser heated spot is moved to the blade position of trimmer.At this time, the hardness of the material drops to 70% to 80% and the cutting forces is declined. As a result, the wear of cutting trimmer is reduced and the life of the cutting trimmer is improved effectively.Keywords：laser assisted cutting;silicon steel;high speed cutting;finite element analysis- 86
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Published：2020-08-13 -
Effect of polarization, phase and amplitude on depletion focus spot in STED
Abstract：As Stimulated Emission Depletion (STED) super-resolution microscopy has a lower resolution, this paper explores the effects of multiphysical variables including light polarization, phases and amplitudes on the focal spots, in order to form a ring-shape depletion focus spot with sharper Full Width at Half Maximum(FWHM) and to increase the resolution of the microscopy.According to Richards-Wolf vector theory, the models of depletion focus spots were established under the actions of polarization, phase and amplitude, the focus spot distribution was calculated in different polarization, phase and amplitude conditions and the distribution of effective fluorescent excitation was obtained by optimizing the parameters.The results show that: by using azimuthal polarization light as depletion, the FWHM is better than those of radial or circular ones; modulations of phase and amplitude are able to reduce the FWHM, and the theoretical value of effective fluorescent excitation FWHM is only 13.2 nm after optimization.By using polarization state, phase and amplitude to modulate the depletion focus spot, the FWHM can be reduced and a higher resolution can be obtained, which is more effective than that using only single physical variable.Moreover, the high quality depletion focus spot and super-resolution ability can be obtained with azimuthal polarization light in STED and the resolution can further be optimized by phase or amplitude modulations based on different realities.Keywords：super-resolution microscopy;Stimulated Emission Depletion(STED);Polarization;phase;amplitude- 96
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Published：2020-08-13 -
Three-dimensional measurement and registration for large scale plates
Abstract：A 3D registration method based on the projection was proposed to align different 3D point clouds for measuring large-scale bending steel plates.First, the 3D measurement of a large-scale bending plate was performed by using a 3D optical scanner and a background projector, in which the 3D optical scanner was used to acquire the dense data of different partial views for the large bending plate and the background projector was used for projecting the background texture on the bending plate to align the point clouds measured at different time.Then,the point clouds were aligned by using the RANdom SAmple Consensus(RANSAC) based registration method and the 3D data measured from different time were registered.Finally, an evaluation method was proposed to verify the registration precision.The experimental results show that the precision of one registration is about 0.5 mm, and the accumulated registration error for measuring a plate with a length of 7.5 mm is about 2 mm.The effectiveness and performance evaluated by the experiments prove that the proposed method can satisfy the requirement of stability and accuracy for the industrial applications.Keywords：3D measurement;3D registration;computer vision;structured light;large-scale plate- 55
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Published：2020-08-13 -
Evaluation of mirror surface figures for TMT based on SlopeRms
Abstract：As the traditional method based on Root Mean Square(RMS) is hard to accurately express middle spatial frequency errors of an optical surface in evaluation of a large aperture telescope, this paper proposes a new method based on SlopeRms to evaluate the optical surface. The method solves the SlopeRms in different space intervals after fitting the optical surface figure by Zernike polynomial. It can better quantify the small scale irregularities and the surface figure error from a smaller size grinding tool or from an aperture mirror surface figure error in multi-point support. The mathematical model of SlopeRms is established, how to calculate the SlopeRms is deduced and then the surface figure for TMT(Thirty Meter Telescope) tertiary mirror is evaluated by the proposed method. The obtained results show that the mirror surface figure error is 0.9 μrad,which is better than that of traditional method (RMS=115 nm) and meets the design requirement.It means that the method based on SlopeRms can objectively evaluate the mirror surface figure error for a large aperture telescope.Keywords：optical test;Thirty Meter Microscope(TMT);surface figure;figure error;SlopeRms;Root Mean Square(RMS)- 56
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Published：2020-08-13 -
Radial shearing Jamin interferometer with variable carrier frequency
Abstract：A new type of radial shearing interferometer with variable carrier frequencies (fringe frequency adjustable) was proposed based on Jamin interferometric plates. The interferometer mainly consists of two Jamin plates, two pairs of rotational optical wedges and two beam expanding/reducing systems with adjustable ratios. The rotational optical wedges were used to adjust fringe periods to obtain an optimum interferogram. The two beam expanding/reducing systems with adjustable ratios could achieve an optimum shear. Moreover, the two optical plates could be machined by cutting half to achieve the same machining error. All the optical wedges and beam expanding/reducing systems were the same in optical parameters and two optical paths were also symmetric and identical.The new interferometer could perform the measurement of aspheric lens mould at one time. The testing experiments of spherical and aspheric moulds show that the interferometer can achieve the best-quality fringe patterns and satisfactory shearing displacement at one time, which provides a solid foundation for the further measurement of various kinds of aspheric moulds.Keywords：Jamin interferometer;radial shearing interferometer;fringe pattern;aspheric lens mould- 62
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Published：2020-08-13 -
Verification of setting function for imaging parameters of space camera
Abstract：The basic composition and functions of imaging parameters of a space camera were introduced. The impact of defective imaging parameter values on the imaging quality was analyzed and the risk of sampling test method for imaging parameter setting was analyzed by applying the mathematical method. On an automatic testing system, a method and a system to achieve a comprehensive verification for setting imaging parameters were proposed to solve the contradiction between test coverage and test efficiency. The method and the system were used to verify the functions of imaging parameter setting of the space camera. Experiment result shows that the proposed method can realize a comprehensive verification for setting imaging parameters of the camera, the test time is shortened to 40 ms for each test case and that is about 50 min for all systems.The method is able to effectively verify the function of setting imaging parameters and can meet the test requirements of zero quality defects.Keywords：space camera;imaging parameter setting;function verification;sampling test- 58
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Published：2020-08-13 -
Analysis of position estimation precision by cooperative target with three feature points
Abstract：On the theoretical analysis, the six factors relating to the measuring precision of a monocular vision pose measurement system with three corresponding feature points were investigated.These factors are the distance between marker and camera, size of the marker, quantitative errors of camera, calibration errors of intrinsic parameters of camera, position errors of feature points, and the error introduced by pose estimation algorithm. The simulations and imaging experiments were performed to verify the validity of the theoretical analysis. It shows that the most effective factor is the measuring distance. The longer focal length and smaller size of a pixel on CCD can reduce the quantitative error, and the bigger error size of target can improve the precision of feature extraction and can minimize the impaction of extraction error caused by image processing algorithm. The noise introduced by electronic hardware is also an important factor that can not be ignored during the system designing phase. The focal length, position of intersection of optical axis and the image plane on CCD, aberrations of lenses of the camera should be calibrated after the camera is manufactured during the calibration phase, and the error of calibration is the second significant factor for the whole measurement system. The error introduced by pose estimation algorithm can be ignored because it is much smaller than the whole errors. The position errors of feature points extracted from the image is the main impaction of precision loss of system.Keywords：monocular vision;three point measurement;pose estimation;error analysis;precision analysis;cooperative target- 100
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Published：2020-08-13 -
Effects of Mg contents on photoelectric properties and N doped behaviors in N doped MgZnO fims
Abstract：N doped MgZnO films with different Mg contents were prepared on quartz substrates using mixed gases of 99.99% pure nitrogen and argon at the same flow by radio frequency magnetron sputtering technique, respectively. The effects of Mg content on the doping behavior of N and photoelectric properties of these films were studied. The experimental results indicate that the resistivity increases and the carrier concentration decreases for the films as the Mg content increases. In the X-ray Photoelectron Spectroscopy(XPS), the N1s peak located near 395 eV is gradually weakened and even disappeared. In the Raman spectra, the peaks of the N for O site (NO) at 272 and 642 cm-1 are also weakened and disappeared with the Mg content increasing. It can be concluded that the doping behavior of N is dominated by the Mg content when N and O are at the same chemical potential in the experiment. With the Mg content increasing, the doping concentration of N for O site (NO) decreases and the chemical state of N is changed. In the film with a low Mg content,N for O site (NO) and N2 for O site (N2)O are coexist, but in the film with a high Mg content, only (N2)O exists.Keywords：thin MgZnO film;N doping;doping concentration;photoelectric property- 53
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Published：2020-08-13 -
Boundary parameters of adaptive optical system in satellite to ground coherent laser communication system
Abstract：The relationship between the residual wavefront error of an adaptive optical system and the coherence efficiency in a satellite to ground coherent Binary Phase Shift Keying(BPSK) laser communication system was explored.The dynamic characteristics of coherence efficiency and the Bit Error Probability(BEP) under adaptive optical correction were discussed,then the influence of atmospherical scintillation on the Bit Error Ratio(BER) of coherent laser communication was analyzed.The theoretical relationship between the Root Mean Square(RMS) of residual wavefront error and the coherence efficiency was derived under an assumption of the uniform intensity distribution.Through the histogram frequency method, the cumulative distribution function of coherence efficiency and BEP were simulated, and the mean BER of communication system was calculated.The results show that the coherence efficiency is mainly affected by the residual wavefront error when the RMS of residual wavefront error is above 1 rad.Moreover, the BER can reach 10-8 level when the adaptive correction achieves diffraction limit.In this case, the BER from atmospherical scintillation may increase 100 times.Keywords：coherent laser communication;atmospheric turbulence;adaptive optical system;wavefront error;atmospherical scintillation;Bit Error Rate(BER)- 85
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Published：2020-08-13 -
Co-simulation of solar tracker based on ADAMS and Simulink
Abstract：To understand the performance of a solar tracker and to improve its design efficiency, the virtual simulation towards the working process of a solar tracker was accomplished by using software ADAMS and Simulink. First, the dynamics model of the solar tracker was constructed by using ADAMS.Then,the control system suitable for the double axis of solar tracker was established based on a speed closed loop by using Simulink.Thereafter,the co-simulation model was set up and the corresponding simulation was completed to determine the basic performance of control system. Finally, the target curve was input into the model, and the co-simulation was accomplished. The simulation results demonstrate that the system has excellent path tracking ability according to the sun elevation angle input curve. After 1.5 s tracking, the system becomes stable as well as the tracking error is less than 0.1% of the target value, which shows that the dynamics model and control system model are accurate and can provide a reliable basis for the development of actual physical prototypes.Keywords：solar tracker;virtual prototype;co-simulation;ADAMS;Simulink- 78
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Published：2020-08-13 -
Replication of polymer microstructure using thermal-assisted ultrasonic embossing
Abstract：A thermal-assisted ultrasonic embossing method was proposed based on silicon molds to replicate thermoplastic substrates in a low cost and high efficiency. The ultrasonic vibration was applied to the mold-polymer interface to heat the polymer rapidly to the embossing temperature. To reduce the risk of damaging the mold, the die was preheated to a temperature which is 35-50℃ below the glass transition temperature (Tg) of the polymer. Then, the influences of the ultrasonic amplitude, ultrasonic force, ultrasonic time, and the thermal-assisted temperature were studied by orthogonal array experiments to reveal the mechanism of ultrasonic embossing. The influence of the substrate thickness was also investigated. The experimental results show that the most important parameter for replication is the thermal-assisted temperature, follows by the ultrasonic amplitude. Moreover,the ultrasonic force is the most important parameter for replication uniformity, while the thinner polymer sheets are more conducive to be replicated under the same circumstances. With the optimized parameters, the replication accuracy has reached 99% on a Polymethyl Methacrylate(PMMA) substrate, and the cycle time is less than 50 s. All theses studied show that thermal assisted ultrasonic embossing has high replication efficiency and is a potential way to mass formation of polymer microstructures.Keywords：thermal-assisted ultrasonic embossing;polymeric microstructure;embossing parameter;orthogonal array experiment- 41
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Published：2020-08-13 -
Calibration and uncertainty evaluation of double parallel-joint coordinate measuring machine
Abstract：On the basis of advantages of ScanMax measuring machines at abroad, a double parallel-joint Coordinate Measuring Machine (CMM) with a RRP structure(two rotation movements and a line movement)was developed, and its error model, calibration method and uncertainty evaluation was investigated. Firstly, the mathematical model and error model was established according to the mechanical structure of the double parallel-joint CMM.Then,the calibration scheme was designed based on the total error analysis, and calibration methods of the parameters such as gravity, torque deformation, parallelism, arm length, null were introduced. Finally, based on the national Calibration Specification for CMM, a evaluation method by measurement repeatability and the precision of length measurement to evaluate measurement uncertainty was proposed. The experiments by proposed method show that the measurement uncertainty of double parallel-joints CMM can reach 12 μm (k=2) in a measurement range of 1 000 mm×250 mm (diameter×height).It is proved that both double parallel-joint coordinate measuring technique and total error analysis technology are feasible. It explores a new way to calibrate non-orthogonal CMM.Keywords：double parallel-joints;coordinate measurement machine;total error analysis;uncertainty;calibration- 67
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Published：2020-08-13 -
Fabrication and wafer-level vacuum packaging of MEMS resonant pressure sensor
Abstract：To improve the quality factor of sensors and to protect resonators, the fabrication and wafer-level vacuum packaging methods for a Micro-electro-mechanic System(MEMS) resonant pressure sensor was proposed based on Silicon On Insulator (SOI)-glass anodic bonding technology. Through Deep Reactive Ion Etching (DRIE) process and buffered oxide etched releasing process, H-type resonant beams and pressure diaphragm of the sensor were fabricated on the low resistivity device layer and the substrate layer of SOI wafer,respectively,and a moveable mechanism was release by a SiO2 layer of the SOI wafer corroded by hydrofluoric acid flow. Finally, electrical connection and a cavity for the vibration of beams was implemented on the Pyrex glass piece by fine mechanical machining and the wafer-level vacuum packaging and electric connection of the resonators were achieved with SOI-glass anodic bonding. Experimental results demonstrate that the packaging scheme is effective and easy to achieve with an excellent hermetic sealing, and the sensor has a differential sensitivity of 10.66 Hz/hPa and linear correlation coefficient of 0.999 995 in the range of 10 kPa to 110 kPa.Keywords：Micro-electromechanical System (MEMS);resonant pressure sensor;Silicon On Isolation(SOI);anodic bonding;vacuum packaging- 80
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Published：2020-08-13 -
Real time description of flexible deformation for leaf spring landing gear by state space method
Abstract：According to the requirements of Unmanned Aerial Vehicle(UAV)ground dynamic analysis,a leaf spring landing gear dynamics model was proposed to accurately reflect the dynamic characteristics of leaf spring deformations.On the basis of modal analysis,the leaf spring landing data were obtained by using the finite element method through modifying stiffness matrix and the model was simplified by modal reduction.After dissolving decoupling vibration differential equations by modal coordinate transformation, a state space model was constructed to describe the dynamics of the leaf spring landing gear. Finally, statics, dynamics simulation tests as well as the leaf spring drop experiments were designed to validate the flexible model.These results demonstrate that the results from state-space model and from finite element software static analysis have only 0.07% error under static conditions.The deviation of drop simulation with this model from real drop experiment results is about 5% when its real-time simulation step is 1 ms,which satisfies the flight simulation requirements.Keywords：leaf spring landing gear;Modal analysis;constraint boundary condition;state space method;real-time describition- 54
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Published：2020-08-13 -
Fabrication of 3D microstructure with layer-by-layer micro-electric resistance slip welding
Abstract：A 3D microstructure with a high depth-to-width ratio was fabricated by combining femtosecond laser cutting and micro-electric resistance slip welding. To improve laminated precision and connection strength of every layer 2D microstructure, the layer-by-layer micro-electric resistance slip welding was used for every layer 2D microstructure to obtain a better technological parameters. Under above process parameters, the anti-shear ability of 3D microstructure was tested. The test results indicate that with the number of the slip welding discharges increasing, the yield shear stress of microstructure increases from 8.04 N to 65.97 N.Then, the deposition effect of the tungsten bar electrode produced during layer-by-layer micro-electric resistance slip welding was also studied through the Energy Dispersive Spectrometer(EDS)analysis.Finally, micro array square holes with a size of 50 μm×50 μm and a micro-gear cavity were processed after 160 time's slip welding discharge under a femtosecond laser power of 110 mW, a cutting speed of 50 μm/s, a welding voltage of 0.21 V,welding time of 10 ms,and a welding pressure of 0.2 MPa.The fabrication results show that the 3D microstructures processed by the layer-by-layer micro-electric resistance slip welding have good surface quality and the superposition between the layers of microstructure.Therefore, layer-by-layer micro-electric resistance slip welding can guarantee the connection strength and laminated precision of every layer 2D microstructure.Keywords：3D micro-structure;femtosecond laser cutting;layer-by-layer micro-electric resistance slip welding;deposition effect- 60
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Published：2020-08-13 -
Interface diffusion mechanism and binding strength of TiAlCN coatings
Abstract：A TiAlCN coating was prepared on the surface of Cr12MoV steel with cathodic arc ion plating. The surface-interface morphologies, chemical element distributions, and phases of the TiAlCN coating were analyzed with a Scanning Electron Microscope (SEM),an Energy Dispersive Spectrometer (EDS) and an X-ray Diffractermetry (XRD), respectively. The mechanism of interfacial combination of the coating was discussed. The results show that the first ionization energy of Al atom is lower than that of Ti atom and is more likely to ionize from the target and deposit on a substrate, which allows the content of Al element to be higher in the coating. The hard phases of the coating are TiN, AlN and AlTiN. The higher Al content in the coating surface is beneficial to improving abrasion resistance and the amorphous C is favour of reducing the coefficient of friction. Ti, Al, C and N elements accumulate in the coating layer and diffuse in the interface, which is the main mechanism of metallurgical bonding. The bonding strength of the coating-substrate is 76.9 N, showing a higher anti-stripping ability. Obtained results provide an experiment basis for application of TiAlCN coatings to surface modified process of cold working moulds.Keywords：TiAlCN coating;cathodic arc ion plating;line scanning;plane scanning;bonding strength- 63
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Published：2020-08-13 -
Highly exfoliated graphite prepared by two-step intercalation and its microstructure
Abstract：To achieve exfoliated graphite with low density and good suspensibility, the mixture of nitric acid and phosphoric acid, and the mixture of nitric acid and acetic acid were employed as intercalating agents; potassium permanganate was used as oxidant, and highly exfoliated graphite was prepared by two-step intercalation. The optimum preparation conditions affecting expanding volume of the exfoliated graphite were determined by orthogonal and parallel experiments, then the exfoliated graphite with an expansion volume of 450 ml/g was prepared with above special procedure. The effect factors on exfoliated graphite prepared by two-step intercalation was analyzed, and results point out that it is related to the amounts of potassium permanganate in the first intercalation and those of acetic acid, potassium permanganate and nitric acid in the second intercalation. Moreover, the microstructures of exfoliated graphite with different expanding volumes were also analyzed by Scanning Electron Microscopy(SEM). The results show that as the volume expends, the layers of the exfoliated graphite are fully opened and its geological section area is increased to form a larger deflection entity.Therefore,it accelerates the decay of infrared and micro wave radiations.Keywords：exfoliated graphite;expanding volume;microstructure;two-step intercalation- 79
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Published：2020-08-13 -
Oblique distance defocus compensation for oblique photographic airborne camera
Abstract：For defocus generated during imaging from an oblique photographic airborne camera, a corresponding focusing mechanism was designed to compensate oblique distance defocus for high imaging quality. The principle of oblique distance defocus was analyzed, the formula of defocus compensation was obtained and a cam mechanism was proposed to compensate the defocus. A focusing mechanism based on a cylindrical cam was designed to replace the traditional focusing mechanism based on eccentric cam, in which the theoretically mode is exact instead of proximal. As the oblique distance defocus system was designed based on a typical height, the residual defocus would be emerged at other heights. The cause of residual defocus was analyzed. The process method and process flow were developed to eliminate the residual defocus. All amount of oblique distance defocus were compensated in all heights and scan angels. Camera imaging simulation with different objects in laboratory approves the validity and accuracy of the proposed focusing mechanism.Keywords：airborne camera;oblique distance defocus;Cam mechanism;residual defocus;compensation- 38
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Published：2020-08-13 -
Determination of satallite autonomous orbit based on star light and geomagnetic field
Abstract：An autonomous navigation method suitable for low orbit satellites is proposed. Different from traditional method that takes a start light angle as the observed variable, the method determines the real time orbital parameters by a start sensor and a geomagnetism sensor, and converses the unit vector observation equation of satellite position into linear equations by converting the observation data from the start sensor appropriately. With fitting the relationship of magnetic field strength and orbit height, it obtains the geocentric distance by using a magnetometer. Moreover, it determines the satellite initial orbit by Lagrange difference algorithm to provide initial value for the filter. As the performance of the filter is effected by the system model error caused from the first-order linear approximation of two body dynamic orbit model, and the high order derivative function values can be replaced by a linear combination of one order derivative function values, this paper processes the state equation by a higher order linearity in design of the KALMAN filter to reduce the calculation. By proposed method, the discretized accuracy of state equation for the filter is improved greatly. Finally, a simulation experiment is performed, which verifies that the method is effective and feasible.Keywords：Low Earth Oribit(LEO) satellite;autonomous orbit determination;spaceborne sensor;least square method;Kalman filter- 63
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Published：2020-08-13 -
Preparation of nano SiO2/CeO2 composite particles and their applications to CMP on sapphire substrates
Abstract：SiO2/CeO2 composite abrasives were synthesized by homogenous precipitation method. The phase composition and morphology of the as-prepared composite nano-spheres were characterized by a X-ray Diffractomer(XRD), a Transmission Electron Microscopy(TEM), and a Fourier Transfer Infrared(FT-IR) spectrometer. The as-prepared composite nano-spheres were used as polishing abrasives for Chemical Mechanical Polishing (CMP) of a sapphire substrate, then the surface roughness of sapphire substrate after polishing with the composite abrasive slurry was measured by a Atomic Force Microscopy(AFM). The results show that the average roughness of the polished sapphire substrate is 0.32 nm and the material removal rate is 16.4 nm/min for composite abrasives,however, those are 0.92 nm and 20.1 nm/min for SiO2 abrasive. It demonstrates that the material removal rate of composite abrasives is less than that of the SiO2, but it has a good surface quality. These results mean that the SiO2/CeO2 composite satisfies the technical requirements for sapphire Light Emission Diode(LED) substrates.Keywords：sapphire substrate;chemical mechanical polish;surface roughness;SiO2/CeO2;composite abrasive- 54
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Published：2020-08-13 -
Effect of different clamping lengths of cantilever bimorph on its dynamic characteristics
Abstract：This work focuses on the effect of clamping length on the dynamic characteristics of a cantilever piezoelectric bimorph vibrator. First, the static parameter equation and the dynamic model of the cantilever bimorph vibrator was established. Then, the effects of the changed clamping lengths on the tip displacement amplitude and the inertia acceleration magnitude of the cantilever bimorph vibrator were analyzed with MATLAB software. Finally, the tip displacement amplitude and the inertia acceleration amplitude of the cantilever bimorph vibrator were measured separately. Results show that the maximal amplitude of tip displacement is 66.2 μm and the generated maximal inertial acceleration is 10.2 ms-2 at a driving voltage of 10 V,a frequency of 11 Hz,and the clamping length of cantilever bimorph vibrator between 9 and 20 mm. Simulation and experimental results indicate that with the same excitation field, the longer the clamping length, the smaller the amplitude of displacement and the larger the inertial acceleration produced by the piezoelectric bimorph vibrator.Keywords：piezoelectric bimorph vibrator;cantilever bimorph vibrator;clamping length;dynamic characteristics- 45
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Published：2020-08-13 -
Application of neural network aided Kalman filtering to SINS/GPS
Abstract：To allow Micro-electro-mechanical System(MEMS)-based SINS/GPS integrated navigation systems to meet the accuracy requirements during GPS outages, a Radial Basis Function Neural Network (RBFNN) aided Adaptive Kalman Filtering (AKF) information fusion method was proposed.Firstly,the system structure consisting of dual modes of RBFNN training and prediction was designed.The RBFNN was trained while GPS signals were available and the inputs for AKF measurement updates were predicted during the GPS outages.Then,the mathematic models for RBFNN and AKF were built and the training strategy for RBFNN and the adaptive algorithm for AKF were designed.Finally, the performance of the proposed information fusion method was validated using real field test data.Test and experiment results show that the position precisions are better than 15 m and 90 m during GPS outages at 40 s and 100 s,respectively.The proposed information fusion method can effectively damp the divergence of the navigation error during GPS outages and can provide a low-cost, high-robustness, and medium-accuracy navigation scheme for small Unmanned Aerial Vehicles(UAVs),guided bombs and land vehicles.Keywords：Radial Basis Function(RBF)neural network;adaptive Kalman filtering;information fusion;Micro-electro-mechanical System(MEMS);integrated navigation- 53
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Published：2020-08-13 -
Speckle reduction of ultrasound images with anisotropic diffusion based on homogeneous region automatic selection
Abstract：An adaptive selection method of diffusion threshold was proposed to improve the effectiveness and stability of a filter in speckle reduction of ultrasound images.An optimal threshold of the ultrasound image was determined by the Otsu binarization algorithm.Then,the ultrasound image was divided into blocks by Quad tree decomposition using the optimal threshold as the criterion of homogeneity.In descending order of the size, the present maximal blocks were picked up from the Quad tree decomposition result, and an optimal homogeneous region of the ultrasound image was selected by the proposed selection criteria.Finally, the diffusion threshold was obtained by analyzing statistical features of the optimal homogeneous region, and the ultrasound image was filtered using this diffusion threshold.The results demonstrate that the proposed method has better performance comparing with the Speckle Reducing Anisotropic Diffusion (SRAD)method and the Detail Preserving Anisotropic Diffusion (DPAD) method.It reduces the operation time effectively, and the average figure-of-merit by using the proposed method is 0.029,0.129 higher than those by using other two mentioned methods.The proposed method avoids the manual selection of homogeneous area and can estimate the diffusion threshold accurately, which can reduce the speckles effectively while preserving the edges.Keywords：ultrasound image;speckle noise;image filtering;homogeneous region;anisotropic diffusion- 59
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Published：2020-08-13 -
Fast CU depth range selection and early CU pruning for HEVC
Abstract：To reduce the computational complexity of the emerging High Efficiency Video Coding (HEVC), a novel fast coding algorithm based on quad-tree type analysis and Coding Unit (CU) pruning was proposed.First,the CU Depth Range (DR) of an encoded Largest CU (LCU) was determined by analyzing its quad-tree type.Then, the DR of the current LCU was predicted based on those of neighboring LCUs and the co-located LCUs in the previously coded reference frame which was before or after current frame.The CU depth range of the current LCU could be determined based on the predicted DR.The proposed method also took advantage of Bayesian decision to obtain thresholds, by which early CU pruning could be determined.Experimental results show that the proposed method reduces encoding time by 41.55% on average in a random access case.Compared with the original HEVC encoding scheme, Bjontegaard delta bitrate (BDBR) increment is 1.94% and BD-PSNR loss is 0.06 dB.Compared with Shen's algorithm, it saves 12% encoding time with a BDBR increment of 1.09% and a BD-PSNR lossof 0.03 dB.Keywords：High Efficiency Video Coding (HEVC);Coding Unit(CU);CU Depth Range Selection (CUDR);CU pruning;quad-tree type analysis- 41
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Published：2020-08-13 -
Acoustic-to-seismic coupling based discrimination for non-metallic mine detection
Abstract：An acoustic-to-seismic coupling based discrimination method was investigated for experimental research of buried non-metallic mine detection.The fundamental theory of acoustic resonance technique for mine detection based on acoustic-to-seismic coupling was introduced.The acoustic parameters that characterize the mechanical features of buried mines were studied and the application of combination effect of acoustic resonance and anti-resonance was discussed. A vehicular experimental system for acoustic mine detection was designed to measure the surface vibration velocities with/without mines in soil.Finally,the acoustic vibration characters of buried mines were analyzed according to the results of scanning detection. The results show that the location with mines buried will exhibit an obvious boost in vibration. Under the given circumstance, the intensity of vibration in the center of mine is 15 times that of off-mine location. The intensity will rise to 20 times if the signal-to-noise ratio is increased. The proposed method can be used to study the acoustic vibration characters of mines buried location. The designed experimental system is cost efficient and easy to operate.Keywords：Acoustic-to-seismic (A/S) coupling;acoustic resonance;mine detection;non-metallic mine- 52
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Published：2020-08-13 -
Image matching of variable circular domain compass features
Abstract：As existing image matching algorithms show the problems of high computational complexity and uncertainty in point-pair selection, a Variable Circular Domain Compass Matching (VCDCM) algorithm was proposed. After key-points being detected by four compasses, the variable circular receiving domain was used to choose the ideal point-pairs. Then, the point-pair set was divided into two subsets according to the distance of point-pairs.The subset of long-distance pairs was used to describe the direction of a key-point and that of short-distance pairs was used to build the descriptor of key-point. Finally, key-points were matched by Hamming distance instead of traditional Euclidean distance, while the match points were filtered with Random Sample Consensus (RANSAC) algorithm to avoid mismatches caused by the noise and moving objects. Comparative experiments between Scale Invariant Feature Transform (SIFT) and Binary Robust Independent Elementary Features (BRIEF) algorithms were performed on the robustness and efficiency. The experimental results show that the proposed algorithm is faster with high accuracy and stability.Keywords：image matching;variable circular domain;key point descriptor;Features from Accelerated Segment Test(FAST)- 42
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Published：2020-08-13 -
On-line three-dimensional inspection using randomly phase-shifting fringe based on least-square iteration
Abstract：An on-line Phase Measuring Profilometry (PMP) based on least-square iteration was proposed to simplify the complexities of system installment and to avoid the influence of additional phase-shifting caused by the non-parallelism between grating lines and object's displacement in the PMP based on synchronous detection. In measurement processing, the sinusoidal grating with arbitrary grid line direction was projected onto an object, and a CCD was used to capture the deformed fringe patterns. After pixel matching, fringe patterns were used to evaluate the phase distribution. The phase-shifting was determined as arbitrary values by both projection system and object's displacement. Finally, the least-square iteration was used to calculate the phases. The experiment result shows when the grating line directions on the reference plane are changed, the measurement results are stable, and the root-mean-square error is less than 0.169 9 mm.It concludes that the proposed method relaxes the restriction of the spatial location of measurement equipment, increases the measurement flexibility and makes the PMP more applicable.Keywords：on-line inspection;phase measuring profilometry;synchronous detection;pixel matching;least-square iteration- 50
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Published：2020-08-13 -
Target threat assessment using improved SVM
Abstract：On the basis of the characteristics of target threat assessment in information fusion, the weaknesses of traditional methods for target threat assessment and Support Vector Machine (SVM) were analyzed. By using the Particle Swarm Optimization (PSO) to optimize the penalty parameter c and core function g in the SVM, a new target threat assessment model (PSO_SVM) was established and the PSO_SVM algorithm was achieved based on the model. To satisfy the requirements of PSO_SVM algorithm, data was preprocessed, including quantification and normalization. When cross-validation method was used to find the best parameters, the POD was used for network training. 75 group data were used in simulation experiments, among them 60 group data were train sets and the others were test sets. Experimental results show that the error of the PSO_SVM method is 0, reaching the desired goal, which proves the accuracy and efficiency of the proposed method.Keywords：information fusion;target threat assessment;particle swarm optimization;Support Vector Machine (SVM)- 70
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Published：2020-08-13 -
Compression for UAV reconnaissance images
Abstract：To reduce the storage space of image data and to recover the high quality image of an interested region, a method of segmented compression reconfiguration based on the interested region was proposed. Firstly, the Region of Interest(ROI)was extracted from the whole image according to some regularity of surveillance targets. The original image was then divided into ROI and Region of Background (BG) by using the segmentation algorithm. Finally, with the compression method based on wavelet transform, the ROI and BG region were compressed with different compression ratios by using the embedded coding of Set Partitioning in Hierarchical Trees (SPIHT). Simulation experiment shows that the method gives higher compression efficiency and the recovered image is more suitable for human eye under the same condition. Compared to other methods, this method increases the Peak Signal to Noise Ratio(PSNR)of image and solves the contradiction of the high compression ratio to high quality.Keywords：Region of Interest(ROI);wavelet transform;image compression;Unmanned Aerial Vehicle(UAV)- 97
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Published：2020-08-13 -
Pseudophoto synthesis based on face sketch and its amendment
Abstract：A method was proposed to transform a face sketch into a pseudophoto and to amend the synthesized pseudophoto. It consists of three procedures for the face pseudophoto: synthesizing, enhancement and local amendment. Firstly, the initial face pseudophoto was synthesized by Local Eigentransformation Technique (LET). Then, the edge features and textures of the face sketch were enhanced to improve the visual effect of synthesized pseudophoto. Finally, the local synthesis error of the face pseudophoto was amended by moving least squares algorithm. The experiment was performed on the CUHK face sketch database and the transformation was compared with real photos. Result shows that the method can effectively synthesize and amend the pseudophoto and can guarantee the similarity with sufficient amendment. As the proposed method only involves the deformation of a local region, it is independent on the neural network to predict the target location in control points.So,it has lowered the computing complexity.Keywords：face sketch;face pseudophoto;pseudophoto processing;local eigentransformation;moving least square method- 72
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Published：2020-08-13 -
Design of binocular vision 3D reconstruction system based on motion recovery
Abstract：An 3D reconstruction system based on binocular stereo vision was improved to obtain higher accuracy and larger scale of 3D reconstruction.A disparity refinement procedure was introduced to the system, so that the matching cost between the original parallax and the adjacent disparity was fitted into a quadratic curve and to re-find a more accurate parallax for the curve. Then, the motion recovery calculation was further applies to estimation of the camera motion matrices and the tracking points and camera motion matrices were taken as the parameters to construct the energy function. Furthermore, the energy function was optimized to reduce errors effectively and reconstruct the motion matrix accurately. Experimental results indicate that the proposed refinement procedure effectively improves the accuracy of reconstruction of point clouds and reduces the error by 16.3 percent in average with avoiding the scale point cloud phenomenon. As the motion recovery calculation steps recover the camera motion matrix accurately,the optimized method reduces the mean re-projection error by 95.5 percent. The point clouds achieved from different angle images are no longer isolated and the reconstructed models are integrated naturally.Keywords：stereo vision;binocular vision;3D reconstruction;disparity refinement;motion recovery- 62
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Published：2020-08-13 -
Automatic feature point extraction for three-dimensional skull
Abstract：A fully automatic skull feature point extraction method was proposed, which extracts the skull feature points by a partitioned statistical deformable model and a model similarity matching method.First, the statistic models of skull partition were constructed, and a benchmark model and a series of generated models were built by statistical model deformation.Then the mapping relationship between models was established and the model similarity was defined.Finally, the feature points of the model to be measured were indirectly obtained with the model similarity and the projection relationship.Experimental results indicate that the location average error of the feature points for an eye socket model is about 3.232 5 pixels.When the distance threshold is 10 pixels (3% of the size of the model), the location accuracy for 90% of the feature points achieves 100%.The method proposed has higher accuracy and exaction for skull feature point extraction as compared with traditional methods, and can extract the feature points of smooth regions for skull models.Keywords：medical image;feature point extraction;statistical deformable model;similarity matching- 74
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Published：2020-08-13 -
Stagewise regularized orthogonal matching pursuit algorithm
Abstract：A novel reconstruction algorithm (stagewise regularized orthogonal matching pursuit) was proposed to reconstruct signals without prior sparsity information. The method constructed the candidate set by designing threshold based on the residual from signal reconstruction. The extracted signal atoms from the candidate set were merged with the previous support set. When the candidate set was a null set, the atom with the greatest correlation was directly added to the support set. Finally, the refinement of signal approximation and residual updating were achieved by solving a least-square algorithm on the support set. The experimental results for Gaussian signal and binary signal with a length of 256 show that the probability of exact reconstruction can be reached above 90% on the conditions of signal sparsity of 50 and 40, and the reconstructing effects and reconstructing speeds are better than those of similar algorithms under the same condition of signal sparsity. This algorithm is proved to be higher processing speeds and more stabile.Keywords：Compressed sensing;reconstruction algorithm;stagewise regularization;matching pursuiting- 53
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Published：2020-08-13
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