Chinese Version Light学术出版中心
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Issue 2 ， 2014
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Improvement of exposure performance of linear array CIS camera by twotrigger method
Abstract：As the frequency changing of external trigger signal from an external trigger Contact Image Sensor( CIS) camera will cause the nonuniform of a scanned image gray value, a new exposure method——two-trigger method was proposed. First, the reason that the frequency changing of external trigger signal affects the image gray value was analyzed. Then, the two-trigger method was introduced. With the method, an external trigger signal was converted to two trigger signals, the first one was used to control the exposure and the second one was used to control the CIS to output data. Finally, it explained that the method can improve the image quality theoretically. A 1.6 meter non-distortion long-term array CIS camera was fabricated based on this method. The experimental results show that the fluctuation range of scanned image gray value is reduced by 75%, and the horizontal stripes on the image is eliminated at different trigger frequencies. When it is applied to an intelligent vision stitch digital printing machine, the image of 1 mm×1 mm hole in the embroidered cloth is clear. It concludes that the proposed method reduces the effect of the frequency changing of external trigger signal on images effectively and improves the image quality successfully.Keywords：Contact Image Sensor(CIS);CIS linear array camera;external line trigger frequency;exposure control- 49
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Published：2020-08-13 -
High-precision pulsed laser measuring distance by time delay method
Abstract：Since the accuracy of laser ranging depends on the accuracy of time measurement, this paper introduces a method to improve the accuracy of time measurement. Under the control of a Field Programming Gate Array(FPGA), the electric signal is transported into the CLK port of a D flip-flop through a delay circuit, the laser sends a laser beam to the target and the target reflects the laser beam back to the photoelectric converter. Then, the laser beam is changed to an electric signal and transported to the D port of D flip-flop. By adjusting the delay time of electric signal produced by a delay chip and mechanical displacement, the laser makes the signal of input ports of D flip-flop arrive at the target at the same time. Therefore, the delay time can be utilized to determine the time of laser arriving the target. Furthermore, the FPGA is used to count the pulse of a constant temperature crystal oscillator with 100 MHz, the MC100EP195 is used to delay and then the accuracy of time measurement is improved to 0.3 ps by the mechanical location method. The experimental results show that the measurement accuracy of the target in 1 km has reached to 0.1 mm, which means that the method can satisfy the requirements of high-precision ranging.Keywords：laser measuring distance;time delay method;delay chip;time measurement- 50
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Published：2020-08-13 -
Sub-regional camera calibration based on moving light target
Abstract：A reliable sub-regional calibration method for CCD cameras was proposed to improve the accuracy and efficiency of industrial vision measurement. With the proposed method, a round light target was moved with the Coordinate Measuring Machine (CMM) according to a trapezoidal shape. The images of light target were processed with least square ellipse fitting algorithm to obtain the center positions. By 3D coordinates of CMM, a set of accurate calibration data were obtained. Furthermore, the image plane was separated into several sections according to the circle symmetrical structure and camera parameters in different regions were calculated with the sub-regional theory and improved Tsai method. Comparing with the sub-regional calibration method to single calibration one, the actual calibration experiments show that the total error is decreased by 17% when the image is separated 8 regions and the average error of single point is decreased about 20% . Experiments demonstrate that the data collection process is automatic and simple, and the camera calibration accuracy meets the medium precision of industrial measurement.It indicates that the method proposed is suitable for the industrial vision measurement, especially for the larger work piece measurement.Keywords：vision measurement;CCD camera;camera calibration;sub-regional theory;improved Tsai method;light target- 48
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Published：2020-08-13 -
Design of long-wave infrared imaging spectrometer with eliminating spectral curvature
Abstract：To achieve the long-wave infrared hyperspectral imaging for remote sensing targets and to eliminate the spectral curvature of a plane grating effectively, a long-wave infrared imaging spectrometer with an off-axis lens was designed. The spectral curvatures from the plane grating and a single off-axis lens were calculated, respectively, and the relationships between spectral curvatures and relative parameters were analyzed, then aninitial structure for eliminating spectral curvature was designed. The optical system optimized shows an aperture of 100 mm, F number of 2, spectral resolution of 20 nm, spatial resolution of 150 μrad, and a cold aperture efficiency of 100% . Moreover, its image quality is close to the diffraction limit and the spectral curvature of system changes from more than 180 μm to less than 14.3 μm. The design obtains a universal eliminating spectral curvature formula, and proves that the off-axis lens has the function to eliminate spectral curvature. It concludes that the imaging spectrometer of plane grating using off-axis lens can offer a spectral curvature less than half the pixel size of the detector without increasing the system complexity, which meets the use request on the premise of satisfying imaging quality.Keywords：optical design;imaging spectrometer;infrared spectrometer;spectral curvature;plane grating;off-axis lens- 53
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Published：2020-08-13 -
Measurement of two-dimensional angle using dynamic modulation and interference fringe shape
Abstract：When a four-quadrant detector is used to receive interference fringes to measure the displacement, the shapes of the interference fringes will affect the phase difference between the detectors. Based on the relationship model between the interference fringe shape and the interference angle, a method to recognize the shape of an interference fringe by the four-quadrant detector was presented. The theoretical formula about the shape parameters of interference fringes with the phase difference of signals obtained by the detector was deduced using the area integration of interference fringe intensity, and the relationship between phase difference and interference angle was given. The interference fringes were dynamically modulated by using a PZT to drive the reference mirror uniformly, and the recognition accuracy of phase difference of the signal was improved. As the phase difference from 0 to π was recognized in high precision through the ellipse fitting technology, and the phase difference in the range (-π, π) was recognized by combining a specific sinusoid and a cosine integral calculation, the deflection angles were measured successfully. Compared with the traditional recognition method that uses the shape of CCD stripe, this method expands the measurement range of the angle, so it is more suitable for dynamic measurement. Experiment results demonstrate that the precision of the proposed method is 3″ for the range from -300″ to 300″, and the method owns higher precision as comparing with a high-precision autocollimator.Keywords：angle measurement;two-dimensional angle;interference fringe;four-quadrant detector;dynamic modulation- 56
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Published：2020-08-13 -
Determination of soluble solid contents and vitamin C of fresh peppers based on NIR spectrometry and least square support vector machines
Abstract：Fourier transform Near-infrared(NIR) spectroscopy was applied to the fast and nondestructive determination of Soluble Solid Contents (SSC) and Vitamin C (Vc) contents in fresh peppers. Seven kinds of pretreatment methods were used to the original spectral processing and the predicted Partial Least Square (PLS) models of SSC and Vc were established. The Principal Components (PC) selected by PLS and effective wavelengths selected by Monte Carlo Uninformative Variable Elimination (MC-UVE) method were used as the inputs of Least Square Support Vector Machine (LS-SVM) , the PC-LS-SVM and MC-UVE-LS-SVM models were developed, and they were compared with the MC-UVE-PLS models. Twenty-seven unknown samples were predicted using the optimized models. The results show that MC-UVE-PLS model obtains the best result for SSC prediction with a correlation coefficient of prediction (rp) of 0.971 and Root Mean Square Error of Prediction (RMSEP) of 0.382 °Brix. The MC-UVE-LS-SVM model obtains the best result for Vc content prediction with rp of 0.899 and RMSEP of 21.022 mg/100 g. The research results indicate that SSC and Vc contents in fresh peppers have a significant correlation with the NIR spectroscopy.Keywords：near infrared spectrum;Least Square Support Vector Machine(LS-SVM);fresh pepper;Soluble Solid Content(SSC);Vitamin C(Vc)- 86
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Published：2020-08-13 -
Radiation forces exerted on redundant particles on optical surface by oblique incident and off-axis Gaussian laser beams
Abstract：On the basis of spherical vector wave functions and their coordinate rotation theory, the scattering properties of dielectric particles by oblique incident and off-axis Gaussian laser beams were discussed to clean the redundant particles on the optical surface. By utilizing the results of electromagnetic scattering of the sphere, the analytical expressions of the radiation forces exerted on a sphere was derived by an incident Gaussian beam with arbitrary directions of propagation and polarization. The influence of the off-axial position x0 and incident angle of Gaussian beam on the axial and traverse radiation forces were discussed in detail. The results show that the maximum radiation force appears on the -2 μm and the second maximum radiation force appears on the 5 μm by an off-axis Gaussian beam. The maximum radiation force appears two round the girdling center position. The larger the incident angle, the smaller the radiation force. The position of maximum radiation force is fixed to the on-axis position Z0. According to the conclusions above, it suggests that adjusting the position of Gaussian beam waist can clear and control the redundant particles more efficiently in the nondestructive examination project.Keywords：optical surface;redundant particle;Light scattering;radiation force;Gaussian beam- 66
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Published：2020-08-13 -
Detection of diesel quality parameters by near infrared spectroscopy with sparse component analysis
Abstract：Independent Component Analysis(ICA) in a blind source separation method can not obtain ideal prediction results and excellent measuring stability in detecting diesel quality parameters by near-infrared spectroscopy. Therefore, a blind source separation method based on sparse characteristics of near-infrared spectroscopy is proposed. The method is named Near Infrared Spectroscopy with Sparse Component Analysis(NIFS SCA) and is used for the prediction of boiling points, density and total aromatics for the diesel. This method firstly trains the redundant dictionary by spectral samples and finishes the sparse transformation for the calibration sample. Then, it estimates the mixing matrix, and establishes the regression model between mixing matrix and diesel quality parameters. As the clustering progress is hard to determine the number of clusters when the sparsity of spectral is not equal to one and the clustering feature is fuzzy, the AP clustering algorithm is applied to the clustering process. The experiments show that the Relative coefficient(R) and the Root Mean Square Error of Prediction (RMSEP) of the NIFS SCA for diesel boiling point, density, total aromatic prediction respectively are 98.91%, 99.68%, 99.43% and 2.84,0.88×10-3, 0.59, which is better than those of ICA and the full spectrum PLS methods. The proposed method can be an effective blind source separation quantitative analysis method for detecting diesel quality parameters and also can be promoted to other spectral detection applications.Keywords：Near-infrared spectroscopy;diesel quality detection;Independent Component Analysis(ICA);Sparse Component Analysis(SCA);Blind Source Separation(BSS)- 97
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Published：2020-08-13 -
Design of fluorescence simulator with large dynamic range for scintillation crystal
Abstract：A scintillation crystal fluorescence simulator with a large dynamic range was developed based on a Light-emitting Diode (LED) for calibrating the Bismuth Germanium Oxide(BGO) calorimeter detectors of the Dark Matter Particle Explore Satellite(DMPES). Firstly, a Photo Multiplier Tube(PMT) was used to measure the fluorescent pulse of a BGO crystal, create an exponential model for the shape of fluorescence pulse and to store the exponential waveform into a programmable signal generator. To match the feature of BGO, the LED with a similar peak wavelength to the BGO crystal and a good linearity between current and light intensity was chosen, and the LED driver with a output current in proportion to the input voltage signal was designed. Finally, the signal generator output the simulated fluorescence pulse of BGO crystal to the driver and allowed the LED to lighting, then ,it transmitted the pulse to PMTs via an integrating sphere with optical fibers. Experiment results show that the pulse shape from the real BGO is coincident with that from the simulator and the dynamic range of output light intensity covers all three dynodes, which is up to 4.11×103. The simulator satisfies the need of ground-based testing for DMPES BGO detectors and can also be used for other similar scintillation crystal detectors.Keywords：Dark Matter Particle Explore Satellite(DMPES);Bismuch Germanium Oxide(BGO);simulator;large dynamic range- 43
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Published：2020-08-13 -
Large range FBG sensor for ship structure health monitoring
Abstract：Fiber Bragg Grating(FBG) sensor with a stickup plane structure can not test the strain precisely in ship structure health monitoring due to its small measuring range. For overcoming this problem, this paper designs a composite structure stickup FBG sensor composed of an annular plane spring and a slab on the basis of stainless steel. This kind of stickup FBG sensor can convert the large strain of composite structure into a small strain of FBG by the annular plane spring. By decreasing the strain coupling coefficient between FBG and tested structure, large-scale strain test is implemented. The sensing principle of the composite structure is analyzed and the stress and strain distribution of the stickup FBG sensor are simulated through finite element method. The simulation result demonstrates the feasibility of this structure in a large strain test. Finally, a loading experiment are performed on a special steel sample. The experiment result shows that this structure has a measuring range more than 20 000 με and good linearity. In addition, the correlation coefficient is up to 0.99. As a conclusion, the sensor is convenient for setting up because of the small volume, and can resolve the problem of large strain test in ship structure health monitoring with good performance.Keywords：fiber sensor;Fiber Bragg Grating(FBG);strain sensor;health monitoring;ship structure;composite structure;finite element method- 55
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Published：2020-08-13 -
Design of frequency-shift interference fringe locking system in holographic grating exposure
Abstract：A frequency-shift interference fringe locking system was established to enhance the contrast of holographic grating profile and to decrease the phase shift of exposure interference fringe caused by the external environment. According to the composition and the working principle of the system, the moiré pattern occurrence condition in the measuring system and its dependence on the phase change of interference fringe were analyzed and the selection method for photodetectors was given. On the basis of the system accuracy, the digital control system was self-designed including A/D conversion digit. A optical frequency shifting method was used to regulate the fringe phase, and an acousto-optic modulator was taken to correct the frequency shifter of the interference fringe movement in real time . The experimental results illustrate that the system can offer a sampling frequency of 5 kHz and can restrain the interference fringe drift and low-frequency moving below 10 Hz. The 3σ value of the phase shift is below 0.12 rad, which means its phase is within ±0.02 interference fringe period. The system can lock the phase of the exposure interference fringe effectively in real time, and can satisfy the requirements of the holographic grating lithography better.Keywords：holographic grating;exposure;Moiré pattern;phase lock;Acoustic Optical Modulator- 88
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Published：2020-08-13 -
Strain detection of concrete structures based on Brillouin backscattering
Abstract：One Glass Fiber Reinforced Plastic (GFRP) single core strain sensing cable is buried in a concrete specimen to measure the strain distribution. As the Brillouin backscattering center frequency will shift on the basis of effects of temperature and strain, the reflection signals are analyzed by an Optical Time Domain Reflectometer (OTDR). The strain variation in the solidification process of concrete is investigated. The strain monitoring results indicate that the strain variation is very obvious at the day when concrete pouring is completed. The trend of strain variation is similar as the temperature variation, which indicates that the strain variation of the concrete specimen during the concrete solidification process is mainly caused by the heat of concrete hydration. After the concrete solidification, a crack with an average width of 6 mm is appeared on the longitudinal center line of the concrete specimen by the external force. The strain variation is measured before and after the cracks appear, the results demonstrate that the strain variation is visibly improved after the crack , and there are three strain peaks in the specimen. By analysis of the strain peak position, the position and direction of the crack can be obtained. Thus, based on the Brillouin backscattering strain detecting technology, the distributed measurement of the concrete strain has been realized.Keywords：Brillouin backscattering;concrete structure;strain detection;Glass Fiber Reinforced Plastic(GFRP);strain sensing cable- 71
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Published：2020-08-13
Modern Applied Optics
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Micro/Nano Technology and Fine Mechanics Design of reaction flywheel systems for small satellites
Abstract：According to the requirement of reaction flywheels in small satellites for small sizes, the design method for an armature size was proposed when the electrical motor was at a minimal volume , and a stator coreless reaction flywheel system was designed based on the method. To avoid the magnetic saturation, the multidisciplinary design optimization method was applied to the design of flywheel rotor and magnetic field of the motor. A optimization strategy combined with Exterior Penalty(EP) function and Sequential Quadratic Programming(SQP) was proposed to optimize the system as well. With optimization, the minimum mass and maximum air-gap magnetic flux density of the rotor were chosen as the objects, respectively, and the maximum equivalent stress, resonance frequency, the polar moment of inertia and the magnetic saturation were taken as constrains. Then, the software iSIGHT with finite element analysis (ANSYS) were integrated to achieve the optimization. Finally, a flywheel prototype was designed based on the optimal results. The results indicate that the total mass of the flywheel rotor has been decreased from 0.73 kg to 0.67 kg (reduced by 8.22%) and the flux density has been increased from 0.376 T to 0.401 T (increased by 6.65%). The optimal design method can improve the rationality of flywheel design, and will promote the progress of the miniaturization investigation of flywheel systems.Keywords：Small satellite;reaction flywheel;motor;multidisciplinary design;combinatorial optimization strategy;Finite Element Analysis (FEA)- 85
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Published：2020-08-13 -
Design of micro-positioning stage with flexure hinge
Abstract：A micro-positioning stage driven by a piezoelectric ceramic is developed, which adopts a bridge-type flexure hinge mechanism to realize displacement amplification and uses a parallel board hinge mechanism to guide. Based on elastic mechanics and material mechanics, the theoretical models of bridge-type flexure hinge and parallel board hinge mechanisms are established and the driving force, output displacement, stiffness and natural frequency of the stage are analyzed. The Matlab software is used to optimize the geometric parameters, including the length and thickness of the bridge-type flexure hinge, and those of the parallel board hinge, By which the optimized parameters are obtained. The micro-positioning stage after optimization is simulated by Finite Element Analysis(FEA) and a test system is constructed to measure the micro-positioning stage . The experimental results show that the largest error between theoretical analysis and experimental result is 9.8%, and the largest error between FEA and experimental result is 4.2%, which verifies the accuracy of theoretical analysis and FEA, and achieves the stage design objective in smaller volumes, higher amplification and large displacement outputs.Keywords：micro-positioning stage;bridge-type mechanism;parallel board mechanism;flexure hinge;Finite Element Analysis( FEA);optimal design- 55
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Published：2020-08-13 -
Flexible ZnO thin film SAW device on polyimide substrate
Abstract：Surface Acoustic Wave (SAW) devices on flexible polyimide substrates were developed. The ZnO piezoelectric layers were deposited on a flexible polyimide substrate by low temperature reactive magnetron sputtering, then the layers were characterized by the X-ray Diffraction (XRD), Sanning Electron Microscope(SEM), and the Atomic Force Microscope. The results show that ZnO layers with columnar structures have (002) crystal orientation and lower layer roughness(less than 9 nm), and they are suitable for fabrication of piezoelectric devices. The SAW device based on the ZnO piezoelectric layers were fabricated on a flexible polyimide substrate, and it could offer excellent resonance characteristics. A vector network analyzer was used detect the transmission curve, and results show that the resonance frequency and phase velocity increase with decreasing wavelength, and the experimental results are in good agreement with the simulated results. When the thickness and wavelength of the ZnO layer are 4 micron, and 8 micron, respectively, the device has its resonant frequency of 268 MHz, acoustic phase velocity of 2 144 m/s and the electromechanical coupling coefficent of 1.1 %. Moreover, the acoustic velocity in the ZnO layer also increases with the increase of the ZnO thickness.Keywords：flexible substrate;ZnO thin film;piezoelectric film;Surface Acoustic Wave(SAW) device- 53
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Published：2020-08-13 -
Image motion compensation of scroll imaging for space camera based on earth ellipsoid
Abstract：The scroll imaging of a space camera can improve its temporal resolution. However, the space camera shows different image motion speeds and drift angles at different positions of field of view in the scroll imaging because of the earth ellipsoid and varied scroll angles. To overcome the problem, the formulas of image motion speeds and drift angles at different positions of field of view were deduced for the scroll imaging based on earth ellipsoid. By taking a high resolution space camera carried on a stereoscopic mapping satellite for an example, the influence of row transfer periods and drift angles adjusting uniformly and individually on Modulation Transfer Function(MTF) was analyzed. Analysis results and on-orbit testing experiments under a constraint of 5% drop for the MTF indicate that the row transfer periods should be adjusted individually if the integral stages are more than 22 in scroll imaging with scroll angle of 10°。In comparison to adjusting row transfer periods uniformly, the drop of MTF along the track direction would be cut down from 10.28% to 0.11% by adjusting row transfer periods individually. If integral stages are fixed to 16, the scroll angle by adjusting row transfer periods uniformly should not be over 13.2°.Keywords：space camera;scroll imaging;Image motion;earth ellipsoid;modulation transfer function- 75
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Published：2020-08-13 -
Fabrication of polymer micro-lens array by micro-fluid digitalization
Abstract：On the basis of the digitalization of microfluids technology, an experimental system for the drop-on-demand (DOD) jetting fabrication of micro-lens array was constructed. The UV-curable adhesive was taken as the jetting material and it was jetted on the glass substrate coated with the hydrophobic film. Then, liquid plano convex micro-droplet could be formed on the glass substrate by surface tension and hydrophobic effect, and the micro-lens array was obtained after the UV light polymerization at a room temperature. The influences of the system parameters on the stable micro-jetting and the diameter of micro-lens were researched. Results show that the UV-curable adhesive with a viscosity of 50×10-3 Pa·s can be obtained in stable micro-jetting and the micro-lens with a diameter of 25 μm is prepared. Furthermore, a 15 × 15 micro-lens array is obtained by experiments with the coefficient of variation diameter of 0.64% and non-uniformity of the focal length of 1.7%. The micro-lens shows a good surface morphology in a Scanning Electron Microscopy(SEM) and its surface roughness is 247.69 nm (scanning area: 29.4 μm×39.3 μm) by the white light interferometer (VSI mode) and the profile curves of the scanning area are smooth. Through the projection image experiment of the micro-lens, the clear real image of the micro-lens array is obtained. Experimental results indicate that the DOD jetting fabrication of the micro-lens array based on the digitalization of microfluids technology has advantages of simple process, low costs, stable process parameters and the micro-lens has good geometry and optical performance.Keywords：micro-optical device;microfluid digitalization;drop-on-demand;UV-curable adhesive;polymer micro-lens array- 58
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Published：2020-08-13 -
Design and assembly of transmitter-telescope
Abstract：On the structure characteristics of emission telescopes, this paper designs and assembles a 270 mm Mersenne reflecting afocal Cassegrain transmitter-telescope to achieve the laser emission and laser collimation. Firstly, the design method for an on-axis reflected system was determined and its system parameters were given. Based on the finite element method, the deformations of cylinder and truss primary mirror supporting structures and that of the three-beam and four-beam secondary mirror support structures were analyzed in the different working conditions, and the three-beam secondary mirror support structure and the truss structure were chosen to be used in the telescope. Furthermore, systematic optical aberration caused by the secondary mirror decentration was analyzed by adjusting primary and secondary mirror structures with the help of an interferometer and an autocollimation plane mirror and a sensitivity matrix was obtained to assembly, adjust and test the system. Finally, obtained results show that the systematic wavefront aberration RMS and PV are 0.146 7λ, and 0.739 41λ respectively. It is proved that the design of the transmitter-telescope has a better imaging quality and satisfies the requirements of the optical design and laser emission.Keywords：transmitter-telescope;truss structure;adjustment structure;misalignment error;sensitivity matrix;autocollimation test- 65
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Published：2020-08-13 -
Adaptive-orientation measurement and micro-machining accuracy of micro-ground pyramid-structured smooth surface
Abstract：When a White Light Interferometry (WLI) is used to measure the micro-structured surface topography, the measured points on smooth micro-structured surfaces and edges are easy to lose. Therefore, an adaptive-orientation WLI was proposed. The method measured each steep surface along its near normal-orientation for the evaluation of its surface shape, feature profile and micro-machining accuracy. First, a #3000 diamond wheel V-tip was employed to fabricate a micro-pyramid-structure Si surface with a depth of 50 μm and a width of 56 μm. Then, four adaptive-orientation measured point clouds were used to splice and reconstruct whole micro-ground surface. Finally, the micro-ground form error, feature profile error and the feature point error were investigated. Experiments show that the adaptive-orientation measurement can reconstruct integrated micro-pyramid-structured surface and the form error is 5.3 μm, which means that the micro-grinding may assure the machining accuracy of micro-pyramid-structured Si surface. In contrast, the evaluation for the feature profiles and feature points of a micro-pyramid-structure indicates that the feature profile error reaches 7.7 μm, and the feature point error is about 15 μm, which is about 3 times of its form error. It suggests that these errors come from the passivations of diamond wheel V-tip and micro grains.Keywords：White Light Interferometry(WLI);adaptive-orientation measurement;Micro-structured surface;micro-machining accuracy- 52
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Published：2020-08-13 -
Fractional control of stabilized platform for photoelectric gyro
Abstract：To improve the isolation of a photoelectric gyro stabilized platform and to improve its accuracy of stability and tracking within velocity disturbance, the fractional PIλ controller was applied to the rate loop control of the photoelectric gyro stabilized platform. First, the shortcomings to improve system accuracy by the conventional PI control were mentioned. Then, the fractional calculus and fractional order PIλDμ control were introduced and the fractional PIλ controller was proposed to improve the control accuracy of the control system. According to the equivalent first-order integral model with a current loop, the design method of fractional PIλ controller parameters also suitable for the integer-order PI controller was proposed based on phase margin and crossover frequency. Finally, a fractional PIλ controller and an integer order PI controller were respectively used to perform the experiments on step response, the residues of velocity disturbance and stable accuracy for an airborne photoelectric gyro stabilized platform. Experimental results show that the system with fractional PIλ controller has smaller overshoot than that with PI controller. The isolation of velocity disturbance is improved about 38% and the stability is improved about 40% at a frequency of 0.5 Hz and an amplitude of 3.14 (°)/s. The experiments demonstrate that control accuracy of system can be improved by using fractional PIλ controller under ensuring the stability margin.The method proposed can be easily realized on engineering.Keywords：photoelectric gyro;stabilized platform;fractional PIλ controller;PI controller;stabilized margin- 63
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Published：2020-08-13 -
Influence factors on static characteristics of flotation force transducers
Abstract：The effects of gas film thicknesses, gas pressures and pressure holes on the static characteristics of a floating force transducer were explored by combing theory, simulation and an experiment. The working principles of nozzle floating plate mechanism were introduced and a static characteristic quation was established. With a pressure hole or not, the Fluent software was used to simulate the gas blanket level speed and a pressure distribution curve under different gas film thicknesses and different air supply pressures. According to the curve, their influences on the static characteristics of gas membrane flow field were analyzed. Finally, an experiment was performed on a air nozzle experimental platform to verify the obtained results. It shows when the gas film thicknesses range 50 μm to 100 μm and gas supply pressures are 303, 505,707 kPa, the linearity curve and sensitivity curve obtained by software simulation are in agreement with that of experimental results . It has no much impact on the capacity and speeds of the gas film whether there is the pressure hole or not. It concludes that the gaps of gas film thickness and inlet pressures will effect on the flow field characteristics of nozzle floating plate mechanism seriouly, while setting the pressure hole has not affect on it.Keywords：force sensor;spray nozzle floating plate mechanism;static characteristics;gas film thickness;inlet pressure;pressure hole- 54
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Published：2020-08-13 -
Design of scanning control system for space optical remote sensor
Abstract：A scanning control system for space optical remote sensors based on the sinusoidal Permanent Magnet Synchronous Motor (PMSM) was explored in this paper. By a control strategy combining composite control with differential negative feedback, the reciprocating motion of a scanning mirror with low velocity and high precision was achieved. The mathematical model of scanning mirror motion was analyzed, and a mathematical model of PMSM under the d-q coordinate system was established. By using the id=0 vector control strategy, the simulation model of the control system based on space vector pulse width modulation was built using the MATLAB/SIMULINK, and the current, speed and the position loop were designed. A simulation and an experiment were performed, the results show that the velocity average error in the simulation has optimized from 1.27% to 0.92% and the steady-state mean angular velocity error has arrived 2.06% when the scanning mirror is at a constant speed steady state after combing control. Theoretical analysis and simulation experiments show that the dynamic characteristics of control system can be improved by the proposed control method, and it shows the advantages of short regulation time, small overshooting and quickly accurate dynamic response.Keywords：optical remote sensor;space scanning mirror;permanent magnet synchronous motor;vector control strategy;compound control;differential negative feedback- 60
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Published：2020-08-13 -
Optimization of structure parameters of channel-type electromagnetic microvalves
Abstract：The structure parameters of a channel-type electromagnetic normally-closed microvalve were optimized to improve its performance. Firstly, the structure parameters were analyzed theoretically based on an approximate structure model. The impacts of main structure parameters on the leakage rate, such as the width and height of a microchannel, the thicknesses of bottom and top films, and the pressure generated by a electromagnetic mechanism were analyzed based on the Finite Element Simulation(FES), and then a empirical formula was established. On the orthogonal experiment method, the influences of the structure parameters on the leakage rate and the open rate were also researched. Finally, the structure parameters of the microvalve were optimized according to the theoretical analysis, FES and the experiment results. The experimental results show that the width and height of the microchannel have the effect on the leakage rate greatly, and the channel height effects on the open rate most.Furthermore,the optimal structure parameters of the microvalve are the width and height to be 1 mm and 0.1 mm, the bottom and top film thicknesses both to be 0.2 mm, and the pressure to be 3×104 Pa, respectively. On the parameters mentioned above, the microvalve has no detectable leakage flow when the backpressure is up to 10 kPa. The microvalve shows its advantages on the low-voltage driving, zero dead volume, simple process and easy to integrate with microfluidic devices.Keywords：electromagnetic microvalve;structure parameter;leakage rate;simulation;Orthogonal experiment- 62
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Published：2020-08-13 -
Open-closed loop iterative learning control of piezoelectric actuators
Abstract：As open-closed loop iterative learning control scheme can up the convergence and reduce the tracking error, this paper uses the scheme to improve high frequency trajectory tracking accuracy of a piezoelectric actuator(PZT). First, a discrete-time open-loop P-type with closed-loop PI-type iterative learning law was proposed and its convergence condition was given. Then, a discrete-time open-closed loop iterative learning controller was designed for the PZT system. Finally, as to 50 Hz and 25Hz+50Hz triangular desired trajectories with single and compound frequencies, the tracking control experiment was performed. Experimental results indicate that the proposed iterative learning controller can achieve 10.6 nm and 12.5 nm maximum tracking errors for the 2 kinds of trajectories, which are 96.25% and 95.62% less than that of the PID controller. It concludes that the proposed control scheme can be easily implemented and can obtain the high accuracy of trajectory tracking without precise hysteresis and PZT system models. It meets both the requirements of single and compound frequency trajectory tracking for high tracking accuracy.Keywords：piezoelectric actuator;PZT;open-closed loop;iterative learning control;hysteresis- 45
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Published：2020-08-13 -
Effect of solvent evaporation on diameter and deposition of nanofibrous scaffold in electrospinning
Abstract：To achieve the controllable manufacturing of electrospun nanofibrous scaffolds, the effects of evaporation rates of different solvents on the fiber diameters and deposition configurations of electrospun nanofibers were investigated experimentally. Firstly, polycaprolactone (PCL) was respectively dissolved in various solvents with different evaporation rates and the electrospun was performed under applied voltage of 15 kV and a receiving distance of 12 cm. Then, the diameters and deposited areas of nanofibers were measured by a scanning electron microscopy. Furthermore, relational expressions between the average diameter and the solvent evaporation rate, the deposited area and the solvent evaporation rate were established by using least square method. The results show that the average diameter of nanofibers increases from 98 nm( with the standard deviation 21.14 nm) to 205 nm (with the standard deviation 38.83 nm) and the deposited areas of electrospun nanofiber webs decrease from 143 cm2 to 35 cm2 with increasing solvent evaporation rates. The mean diameter of nanofiners has a proportion relation with solvent evaporation rate of d∝N0.25i and the relation of evaporation rate and deposition area is S∝N-0.18i. The experimental results and relational expressions can offer the valuable information for guiding the controllable manufacturing of electrospun nanofibrous scaffolds.Keywords：electrospinning;solvent evaporation;scaffold;nanofiber diameter;deposited area- 48
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Published：2020-08-13
Micro/Nano Technology and Fine Mechanics
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Information Sciences Auto-exposure for CCD camera based on FPGA
Abstract：As CCD camera may image in different scenes and changed scenes in some special applications, an effective automatic exposure algorithm is proposed based on image histogram statistics and image mean blocking. Firstly, it analyzes the luminance distribution of image one and calculates the optimal mean of the next image. Then, it adjusts the exposure value of the next image based on the optimal mean to gain the image with rational exposure. The experimental results show that the method can obtain an image with appropriate brightness. After accounting the histogram, the algorithm has less calculation, which is dependent on the histogram and some means and nothing on the image sizes. When the pixel clock is 60 MHz, the calculating time just needs 6 μs.Moreover, it not only has a good capability to different scenes, but also can meet the requirements of the CCD camera for automatic exposure in real time at changed scenes.Keywords：CCD camera;automatic exposure;histogram;exposure value;Field Programming Gate Array(FPGA)- 54
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Published：2020-08-13 -
Hyperspectral remote sensing image classification based on SSDE
Abstract：To improve the classification accuracy of hyperspectral remote sensing images by utilizing labeled and unlabeled samples, a new semi-supervised manifold learning method called Semi-supervised Sparse Discriminant Embedding (SSDE) is proposed. By combining the advantages of manifold structure among classes and sparsity, the algorithm not only preserves the sparse reconstruction relationship between the samples, but also gets the intrinsic attribute of high dimensional data and the manifold structure of low dimensional data by introducing a few labeled training samples and a large number of unlabeled training samples .So,it extracts the discriminant feature of data and improves the classification accuracy . The classification experiments in Washington DC Mall and Indian Pine data set show that the method is a more effective way to find the internal structure of data in a high dimensional space. Compared to other methods, the SSDE obviously improves the classification performance. By taking randomly selected 8 training samples with classification labels and 60 ones without classification labels as examples, the highest classification precision of SSDE respectively reach 77.36% in Indian Pine and 97.85% in Washington DC Mall data set.Keywords：Hyperspectral remote sensing image;image classification;dimensionality reduction;Sparsity representation;manifold learning;semi-supervised sparsity discriminant embedding- 55
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Published：2020-08-13 -
Automatic blood vessel extraction for CTA images
Abstract：When vascular structure information is segmented from three-dimensional data of Computed Tomography Angiography(CTA), it usually involves considerable amount of human intervention. To improve the vessel extraction efficiency, a fully automatic extraction method was proposed to segment blood vessels from three-dimensional data sets. Firstly, a multi-scale enhancement filter was developed to enhance the tubular-like structures, by which the non-tubular structures and noise were effectively removed. Then, a gradient image was combined with Sigmoid function to produce the speed image, and the Geodesic Active Contour(GAC) level set was utilized to approximate the real three dimensional vascular outline. Thereafter, the obtained vasculatures were processed by Laplacian smoothing function and a smoothed vascular surface was obtained. The proposed method was validated on both chest and neck CTA data. Experimental results show that blood vessels can be segmented accurately and automatically without human intervention. According to the phantom experiments, the average errors estimated for centerline and diameter of extracted vessels are 0.26 mm and 0.16 mm respectively. As there is no human interaction involved in the segmentation, the developed method can be utilized for the computer-assisted diagnosis of vascular related diseases in clinical practices.Keywords：Computed Tomography Angiography(CTA);blood vessel structure;3-D data set;automatic segmentation;multi-scale enhancement;data simulation- 73
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Published：2020-08-13 -
Rate control algorithm for stereoscopic video coding based on binocular visual characteristics
Abstract：To allocate bitrates more satisfactory with human visual characteristics, a new rate control algorithm was proposed for an asymmetric quality stereoscopic video coding. Firstly, an exponent model(Rate-ratio Quantization,RRQ) between the rate ratio and the difference between quantization parameters of left and right frames was established. Then, the algorithm was performed on three levels, namely Stereoscopic Group of Pictures (SGOP) level, stereoscopic image pair level and frame level. The target bits for each SGOP and the quantization parameter of each key frame were calculated in the SGOP level, the total target bits for each stereoscopic image pair were calculated according to the remaining bits in the SGOP and the current buffer occupancy in the stereoscopic image pair level, and by utilizing the binocular masking, a stereoscopic rate distortion model was used to allocate bitrates for the left and right frames more rationally in the frame level. Experimental results show that the proposed algorithm can control the bitrates error within 0.21% on average. Meanwhile, it has improved the stereoscopic video objective quality by 0.23 dB and 0.06 dB as compared with the symmetric quality algorithm and Wang's algorithm, respectively, so that it can provide more stable video quality fluctuation. In conclusion, the proposed algorithm has effective network transmission bandwidth, and can satisfy the requirements of human for stereoscopic video by utilizing the human binocular visual characteristics.Keywords：stereoscopic video;coding rate control;binocular visual redundancy;asymmetric quality- 55
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Published：2020-08-13 -
Image restoration based on visual contrast sensitivity and just noticeable distortion perception
Abstract：As traditional restoration algorithms have weaker perceptual opinion in a low Peak Signal Noise Ratio(PSNR), a novel image restoration approach based on visual contrast sensitivity and Just Noticeable Distortion(JND) perception was proposed. Firstly, the image was coded as a sets of bands in different scales with Discrete Cosine Transform(DCT), the JND threshold of each band was calculated with probability summation and DCT perception model, and distortion measure was calculated with a Minkowski metric. Then, an iterative bisection procedure was used to adjust the channel weight for each band in each scale until the perceptual distortion of band was just equal to the anticipant distortion threshold. Finally, the coefficient of each band was weighted with visual contrast sensitivity function, and the coefficient after visual perceptual weighting was reconstructed through an inverse DCT to gain the restoration image. Experimental results based on LIVE image database show that this algorithm can effectively enhance PSNR and improve perceptual quality of the recovery images.Keywords：image restoration;visual contrast sensitivity;just noticeable distortion;Discrete Cosine Transform(DCT)- 38
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Published：2020-08-13 -
Image defect of full-frame CCD in TDI mode
Abstract：When a long focal area-array CCD camera takes photos in a TDI mode for dynamic lateral multi-frame imaging, it will output images with large size defect on the edge of image because of the high line transfer frequency or long exposure time and will influence image interpretation. To overcome the problems, the operating principle of area-array CCD in the TDI mode was analyzed, and the analysis indicates that the large size defect in the image comes from the invalid TDI transfer stages of the CCD during shutter exposure process. The obtained results were verified by a experiment and a method that the TDI transfer was finished simultaneously with shutter exposure was proposed to remove the invalid TDI transfer. On the basis of the analysis, a photo-electricity positioning synchronized was proposed and a photo-electricity synchronizer was developed to settle the headache. The results show that the image defect area is less than 15 column-pixels, which successfully solves the image defect from the area-array CCD camera in the TDI mode and improves its image interpretation accuracy.Keywords：CCD camera;full-framer transfer CCD;area-array CCD TDI stage;line transfer frequency;image defect- 61
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Published：2020-08-13 -
Energy efficient distributed link scheduling protocol
Abstract：To decrease the scheduling length and energy cost of a wireless sensor network, a Distributed Link Scheduling (DLS) protocol was proposed based on graph coloring. With proposed scheme mentioned in the protocol, every node was required to construct its two-hop conflict graph, and the scheduling order of every link was decided by its priority and interference degree in the conflict graph. The proposed DLS algorithm relaxes the problem of longer scheduling caused by randomly scheduling and frequent state transition in traditional algorithms. Since the DLS can assign the adjacent slot for every node, the times of node's state transition and the energy cost can be decreased. The efficiency on decreasing the scheduling length and network energy cost of DLS was analyzed. The simulation results show that the scheduling length of the proposed DLS protocol is less about 1-2 slots than those of the Distributed Scheduling-fixed Power Protocol Interference Model (DS-fPrIM) and Distributed RANDomized time slot scheduling (DRAND ) and its scheduling energy cost is the same as that of the DS-fPrIM, but less than that of the DRAND. Moreover, the state transition of the DLS is once less than those of the DS-fPrIM and DRAND. The results also indicate that the proposed DLS protocol has good performance on energy efficiency.Keywords：wireless sensor network;link scheduling;scheduling priority;interference degree;state transition- 55
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Published：2020-08-13 -
Electronic image stabilization for Bayer color video sequence image
Abstract：A novel method for Electronic Image Stabilization (EIS) of Bayer color video image sequence was proposed. On the basis of the characteristics of Bayer color image, it converted firstly the Bayer color image into a gray image by using demosaicing and converting RGB into YCbCr. Then, the motion estimation algorithm based on gray scale projection was used to estimate the translation parameter between current frame and reference frame, in which the gray scale projection curves of horizontal and vertical directions of the gray image well reflected the feature of gray distribution in the corresponding direction, and the translation parameters could be obtained via cross correlation function of the gray scale projection curves. In order to resolve the problems of mismatch-color when translation was odd, the motion compensation algorithm based on the bilinear interpolation was applied to compensation of the translation of current frame. Finally, the demosaicing and image stabilization for the Bayer image sequence were performed. The experimental results for video sequences show that the proposed method can implement image detection in a pixel level, and can achieve higher stabilization accuracy with a peek signal to noise ratio of 40 db. It is efficient and suited for the motion estimation and compensation for Bayer color video image sequences.Keywords：Bayer color video squence image;Electronic Image Stabilization (EIS);demosaicing;motion estimation;motion compensation- 47
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Published：2020-08-13 -
Fusion of infrared and visible images based on multi-features
Abstract：In allusion to the lower overall contrast and smaller detail contrast of a fused image from the conventional fusion methods, an effective multi-feature weighted multi-resolution image fusion algorithm was proposed. Firstly, the edge features and average gradient features were extracted from a low frequency coefficient after multi scalar decompose, while the correlated signal intensity ratio feature was extracted from a high frequency coefficient. Then, the high frequency coefficient of the fused image was obtained from the pixel-level weighted average image fusion conducted by the edge feature fusion. Furthermore, a novel combination map was proposed to process the frequency coefficient from the same place with two patterns to solve the problem that the simple weighted method is not effective for retaining the edge and texture information. Finally, the low frequency coefficient of the fused image was obtained by adaptive weighted method based on regional average gradient and the target image was obtained by inversing multi-scale transformation for low frequency and high frequency coefficients. The experiments on fusing infrared and visible images show that the proposed algorithm is better than the classical methods. And the fusion quality indexes, such as standard deviation, spatial frequency, information entropy and average gradient have increased by 15.12%, 4.30%, 6.15% and 3.44%,respectively.Keywords：image fusion;infrared image;visible image;edge feature;correlated signal intensity ratio;average gradient;feature level fusion- 56
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Published：2020-08-13 -
Finite mixture model of stochastic cerebrovascular segmentation based on TOF MRA
Abstract：As the brain vessel of human has complex topological structure and smaller space proportion,it is hard to be segmented and reconstructed in three dimensions. Therefore, this paper proposes an automatic statistical intensity based approach for extracting the 3D cerebrovascular system from time-of-flight (TOF) Magnetic Resonance Angiography (MRA) data. First, the Finite Mixture Model (FMM) is analyzed, and it is used to fit the intensity histogram of the brain image sequence preprocessed by the Maximum Intensity Projection(MIP). Then, the Gaussian distribution is used to fit the vessel, and the Gaussian distribution and Rayleigh distribution are used to fit other low intensity tissues. Since the model is easy to realize and has a short parameter vector, it decreases the parameter drift problem and can fit the intensity histogram well, especially in the cross region between the cerebrovascular and other tissues. Moreover, the stochastic disturbance is added in the traditional Expectation Maximization(EM) to construct Stochastic Estimation Maximization (SEM) algorithm to estimate the parameter vector, by which the method shows low initial value dependence and a high robust. As compared with the experiments, this model can segment more 27% cerebrovascular voxels than two Gaussian models do and it can segment in three level for the small cerebrovascular branches with a better connectivity. The model can fit a gray distribition curve of the data accurately , segment the main branch of brain vessel and slight vessel branch and can be used in other similar systems.Keywords：Time-of-flight Magnetic Resonance Angiography(TOF MRA);cerebrovascular segmentation;finite mixture model;stochastic estimation maximization (SEM) algorithm;intensity histogram;Rayleigh distribution.- 77
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Published：2020-08-13 -
Real-time image processing in TDICCD space mosaic camera
Abstract：A real-time image processing method based on a Field Programming Gate Array(FPGA) was proposed for Time Delay Integral( TDI)CCD space mosaic camera to improve its imaging quality and visual effect. Firstly, the TDICCD imaging system was corrected in a non-uniformity mode by a pixel level,by which the fixed-pattern noise and dark current noise were eliminated. Then, an adaptive median filter based on the inline max-min values was proposed to eliminate the random noise and pulse noise. Furthermore, an image after denoising was enhanced in the TDICCD image. By extracting the low-frequency part and the high frequency part of the image, the detail adjustment and contrast enhancement of the image were implemented. Finally, a linear stretching method based on image line data divided was proposed to improve the dynamic range of the real-time imaging system. Moreover, a real-time image processing method for the TDICCD space mosaic camera based on FPGA was designed, and the synthesized resources, algorithm errors and reliability in the FPGA were analyzed. The experimental results indicate that the average SNR of the imaging system has been improved from 48 db to 52 db,and the non-uniformity decreased from 3.41% to 1.73% within a TDICCD. The image contrast is enhanced greatly and the dynamic range is prompted by 6% in the self define criterion.Keywords：Time Delay Integration(TDI) CCD;CCD camera;real-time processing;image enhancement;self-adaptive median filter- 71
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Published：2020-08-13 -
Fast image segmentation with multilevel threshold of two-dimensional entropy based on firefly algorithm
Abstract：A fast image segmentation method with multilevel threshold of two-dimensional entropy was proposed based on the firefly algorithm to overcome the large amount of calculation and long computing time. Firstly, the principle of two-dimensional entropy threshold segmentation was analyzed, and the single threshold segmentation of two-dimensional entropy was extended to multilevel threshold segmentation. Then, the bionic mechanism and searching optimization process of the firefly algorithm were analyzed, and the multilevel threshold segmentation method of two-dimensional entropy combined with firefly algorithm was proposed. Finally, typical image segmentation experiments by using the proposed method were performed and the results were compared with those of two-dimensional entropy exhaustive segmentation method and the multilevel threshold segmentation method of two-dimensional entropy based on Particle Swarm Optimization(PSO). Experimental results show that the speeds of the proposed method in single threshold segmentation, dual-threshold segmentation and the three threshold segmentation are 3.91, 1 040.32 and 8 128.85 times faster than those of the two-dimensional entropy exhaustive segmentation method respectively. Moreover, the threshold selection accuracy and running speed of the proposed method are both better than those of the multilevel threshold segmentation method of two-dimensional entropy based on PSO. Therefore, the fast image segmentation method with multilevel threshold of two-dimensional entropy based on firefly algorithm can quickly and efficiently resolve complex and multi-target image segmentation problems.Keywords：image segmentation;multilevel threshold segmentation;two-dimensional entropy;firefly algorithm- 63
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Published：2020-08-13
Information Sciences
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