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Issue 11 ， 2007
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Design of head-mounted projective optical systern using double-layer diffractive optical element
Abstract：A head-mounted projective optical system with double-layer Diffractive Optical Element (DOE) was designed and the detailed design procedure was given. The diffraction efficiency of the system at each wavelength in designed band is larger than 90%, which improves the image contrast and color reliability significantly. The Field of View (FOV) is 50° while the eye relief and exit pupil size are 25 mm and 10 mm. The features of 19.2 mm system size and 7.8 g overall weight guarantee the lightness and compactness of the optical system. The Modulation Transfer Function (MTF) value at 0° FOV is 0.6 for 38 lp/mm spatial frequency,and more than 0.3 for all FOV, which satisfies the requirement of the color micro-display sized 2.8 cm(1.1 in) diagonal with a SXGA resolution. The lateral color of 8.2 μm, field curvature of 0.4 m-1 and the distortion less than 5% are obtained, which means the designed optical system has good performance in the field of virtual reality and collaborative environments. The phase and line frequency versus aperture of the two binary surfaces are given. When the number of etching levels is eight, the minimum feature sizes of both the diffractive surfaces are 6.3 μm, which is not a very high demand for technique.Keywords：optical design;double-layer diffraction element;Head-Mounted Projective Displays(HMPDs)- 31
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Published：2020-08-12 -
Evaluation method of angular resolution for extreme ultraviolet telescope
Abstract：The Extreme Ultraviolet Telescope(EUT)’s operational wavelength band is smaller nearly two levels than that of the visible light and its in-band diffraction limit is very low,so it is very difficulty to measure a angular resolution in extreme ultraviolet band. In this paper a new evaluation method using ZYGO interferometer to test the figure error and alignment error of the EUT in visible light is introduced. Then, the Zernike coefficients independent of the operational wavelength are brought into the optical design software, so that the point spread function and diffraction encircled energy in operational wavelengths can be obtained by the optical software. Finally, the angular resolution of the EUT in extreme ultraviolet band is calculated by the relative parameters.Experimental results show that the evaluation method has the advantage of high speed and efficiency for an imaging apparatus in extreme ultraviolet band.Keywords：Extreme Ultraviolet Telescope(EUT);angular resolution;point spread function;encircled energy- 56
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Published：2020-08-12 -
11D integrated optic waveguide chip packaging system based on center-integration algorithm
Abstract：A 11D integrated optic waveguide chip packaging system based on center-integration algorithm was designed and fabricated for adjusting the 11D positions of a waveguide in the space. The chip alignment can be realized quickly and precisely by the precision alignment and the improved center-integration algorithm. The packaging test among single-core fiber, channel waveguide and single-core fiber shows that the average of end-coupling loss is 0.113 6 dB, the maximum of single coupling loss is less than 0.13 dB, the standard deviation less than 0.02 dB, single coupling time less than 2 min and the whole packaging process time less than 5 min. The packaging produce among single-core fiber array, 1×8 splitter coupler and 8-core fiber array shows that insert loss of every channel is less than 10.5 dB,the homogeneity index less than 0.4 dB, the single coupling time less than 5 min and the whole packaging process time less than 7 min. It is validated that the system can reach the commercial standard by the test data, which means that the system has good effect and practicability.Keywords：center-integration algorithm;device packaging;waveguide chip;coupling loss- 69
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Published：2020-08-12 -
Optical and mechanical design of SWIR hyperspectral field spectroradiometer
Abstract：Based on flat field diffraction gratings and array detectors, the optics and structures of a Shortwave Infrared(SWIR) field spectroradiometer were designed.The spectroradiometer comprises of two cells and guides light by fiber optic to simplify the optical designs of system and structure. In order to make two cells have the same Field of View(FOV),a pre-optical system was designed to ensure the radiance of any point in the FOV for illuminating all fibers uniformly. The FOV can be changed with different pre-optical systems also. Based on the relation of the luminous flux and the spectral resolution with incidence slit, the size of slit was educed. The spectral range of radiometer is 900~2 400 nm with the resolution better than 12 nm. Experimental results show that the instrument can meet the requirements in field measurements.Keywords：hyperspectra;spectroradiometer;Shortwave Infrared(SWIR);remote sensing;optical design- 35
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Published：2020-08-12 -
Dual cavity inter-compensating absolute radiometer
Abstract：A new type absolute radiometer, named Dual Cavity Inter-Compensating Absolute Radiometer(DCICAR)was constructed. A conical cavity of DCICAR is fabricated as a whole body by combined the conical part with the cap brim for heat conduct and a Pt resistance is used as temperature sensor. The DCICAR works in a mode of inter-compensated when the two cavities are put side by side and faced the same field of view(FOV), also kept the same states of heat conducting,convection,dissipation and heat sink in the same temperature environment. The two cavities are always heated in the same temperature through the whole measurement process. Experimental results show that the repetition of DCICAR is better than 0.05%. By taking the SIAR-2c (Solar Irradiance Absolute Radiometer) as transfer standard demonstrated in the Tenth International Pyrheliometer Comparisons (IPC-X) organized by World Radiation Center (WRC) at Switzerland in 2005, the correct factor of channel A of DCICAR relatively to World Radiation Reference(WRR) is 0.999 73, and the channel B of 0.999 17. So DCICAR can be well coincident with WRR in 0.1%.It concludes that the compensation effect of DCICAR is improved with a short time constant and high sensitivity. The measurement results from two cavities could be compared and validated with each other.Keywords：radiation measurement;Dual Cavity Inter-Compensation(DCIC);absolute radiometer;comparison- 31
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Published：2020-08-12 -
Correcting errors in definite area: a new method for controlling mid-spatial-frequency errors in optical surface
Abstract：A new method for controlling the mid-spatial-frequency errors located in definite area in a large optical surface, correcting errors in definite area, was brought forward. The basic idea and workflow were presented. Then,the processing parameters were optimized based on the maximum entropy principle.The optimized rotate speed ratio is -1 or 0, and the eccentricity ratio approaches 0 but not 0. Finally, a comparative experiment was done on a Φ100 mm K9 glass flat mirror. The experimental results indicate that the PSD value of 0.28 mm-1 frequency errors decreases from 14.76 nm2·mm to 3.70 nm2·mm within 1.5 min. The mid-spatial-frequency errors in optical surfaces can be controlled effectively by means of correcting errors in definite area. Compared with other methods, the correcting errors method in definite area has the advantages of determinacy and high-efficiency in optical machining.Keywords：optical surface;mid-spatial-frequency error;definite area;maximum entropy principle- 51
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Published：2020-08-12 -
Third-order optical nonlinearities of squaraine derivatives
Abstract：In order to find and study the nonlinear optical materials with large third-order optical nonlinearities to fabricate optical devices, the third-order optical nonlinearities and dynamic responses of two kinds of squaraine derivatives were measured using femtosecond Degenerate Four-wave Mixing (DFWM) technique at 800 nm. The second-order hyperpolarizabilities of squaraine derivatives are as large as 10-31 esu, and the response time is shorter than the experimental time resolution of laser. It is clarified that the squaraine derivatives both have large third-order optical nonlinearities and fast optical response under off-resonant conditions, which indicates that the squaraine derivatives have potential applications in nonlinear optics.Keywords：third-order nonlinear optics;Degenerate Four-wave Mixing(DFWM);squaraine derivative;molecular hyperpolarizability- 34
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Published：2020-08-12 -
Comparison and analysis of several methods for measuring waveplate retardation
Abstract：In order to optimize the measuring methods of waveplate retardation and determine the discrepancy in experimental results from different measuring methods and instruments, a high-precision multifunctional experimental system was established to measure the waveplate retardation in different measuring methods and to make a comparison with these methods.A comparative experiment of scanning spectrum method, Soleil compensator method and two light intensity measuring methods was carried out. Combined with the experimental results, the errors of these methods were analyzed. The results show that the scanning spectrum method is appropriate for measuring λ/2 waveplate with error less than 0.032%, whose measurement accuracy is mainly determined by the accuracy of monochromator; The error of Soleil compensator method is less than 0.18%, which primarily comes from the accuracy of Soleil compensator, and for the measurement of λ/2 waveplate, scanning spectrum method and Soleil compensator method can verify each other within the error limits; The error of the light intensity measuring methods is related to the sample waveplate retardation, defects of optical path arrangement, polarizers and the defects from measuring methods.Keywords：applied optics;waveplate;retardation;error analysis- 79
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Published：2020-08-12 -
Colour properties of plasma plume produced by pulsed laser ablating metal Cu
Abstract：In order to study plasma plume radiation properties,a radiation model of plasma plume was established.Based on time and spatial-resolved measurements the plasma plume emission spectrum in oxygen by pulsed laser ablating copper was analyzed,and the photographs of plasma plume were given. The experimental results show that plasma emission spectra are primarily composed of atomic spectrum and univalent ion spectrum. The plasma plume has different colours in different regions,the region colour is changed with ambient gas pressure. The core region spectra are primarily composed of bremsstrahlung radiations, and the middle region spectra are primarily composed of atomic spectrum and univalent ion spectrum, while the outskirt region spectra are primarily composed of atomic spectra. The continuous background radiation comes from the bremsstrahlung radiation ejected from the electron moving near target and recombination of the electron and univalent ion near target, and the primary mechanism of atomic radiation is electron collision energy transfer and recombination of electron and univalent ion near target, while the primary mechanism of univalent ions radiation is electron collision energy transfer.Keywords：laser ablation;plasma plume;colour;copper- 43
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Published：2020-08-12 -
Generation of short pulse and high power non-diffracting beam by active and passive schemes based on axicon
Abstract：Based on an axicon-based Bessel-Gauss resonator, a nanosecond high power non-diffracting pulsed Bessel-Gauss beam was generated directly from a flashlamp pumped Q switched Nd:YAG laser for the first time.The experimental results were analyzed using the Bessel-Gauss model deduced from the diffraction integral theory and they were consistent with the numerical simulation. On the other hand, by a high stability nanosecond Gaussian pulse generated from a Q switched Nd:YAG laser with an anti-resonant ring and pulse shaping passing through an axicon, a nanosecond non-diffracting zero order Bessel beam was obtained using the passive method.A film-scanning was used to record the fine structure of the intensity profile,and a beam analyzer to measure the pulse characteristics. The measured results show that the central spot size is about 90 μm and the peak power density of the central spot reaches to 2.3×109 W/cm2.Finally, the active and passive schemes for generating the nanosecond non-diffracting beam were compared and analyzed.Keywords：non-diffracting beam;nanosecond light pulse;Bessel beam;Bessel-Gauss beam;axicon- 31
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Published：2020-08-12 -
Design of a mini star simulator based on digital optical processing
Abstract：The technical scheme of a star simulator based on Digital Light Processing (DLP) technology is proposed in order to meet the demands of a star sensor in spacecraft engineering. The general optical structure is confirmed according to the technical indexes of a star sensor. Then, the optical system parameters of the simulator are calculated by the specification of a Digital Micro-mirror Device (DMD). Finally, a dynamic display algorithm for the star map is introduced. The simulating results indicate that field of view of 10.5°×7.5°, star magnitude simulated of 2.0~8.0 and the single-star field angle of less than 40″ are obtained, and the sampling period is controlled within several milliseconds. The experimental result can satisfy the system requirements of big field of view, wide magnitude range and short sampling period.Keywords：star simulator;Digital Light Processing(DLP);Digital Micro-mirror Device(DMD);optical design;display algorithm- 28
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Published：2020-08-12 -
Finite element analysis and application of beryllium tip-tilt mirror in space solar telescope
Abstract：In order to improve dynamic range and effective bandwidth of the correlation tracker in a space solar telescope, the beryllium was optimally chosen as a space mirror material to fabricate a tip-tilt mirror of correlation tracker. The finite element model of the beryllium mirror was established and the mechanical properties of the tip-tilt mirror under inertia and temperature loads was analyzed. Then,the surface figure and inner stress of the tip-tilt mirror under different working conditions were investigated. Finally, the mechanical properties between same structure mirror of beryllium and silicon carbide were compared. The analysis results show that the final RMS surface figure error of 2.18×10-6 mm and PV of 1.69×10-5 mm are obtained, the resonant frequency is 1 609 Hz. The beryllium mirror substrate has already obtained, and its optics process is proceeding. The results indicate that analysis results satisfy the technology requirements of the tip-tilt mirror of the correlation tracker. The inner stress of the mirror is less than yield strength of beryllium material when the tip-tilt is under inertia and temperature loads, the analysis results of beryllium tip-tilt mirror are better than that of silicon carbide tip-tilt mirror.Keywords：space solar telescope;correlation tracker;tip-tilt mirror;beryllium;finite element analysis- 47
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Published：2020-08-12 -
Coaxiality measurement method based on revising aberration
Abstract：In order to realize synthetic coaxiality measurement for position deviations and angle deviations simultaneously, a laser beam-spot receiver system consisting of a receiver lens, beam splitter prisms, and CCD based on laser collimation was established. The triangular relationship among the lens optical axis, laser beam axis, and CCD was used to calculate those two deviations. In addition, a calculation method for obviously reducing the effect of lens’ error on optical aberration was presented. The theoretical and experimental data indicate that, for a system with position measurement range of ±10 mm, angle measurement range of ±2°, the receiver lens’ focal length of 50 mm, and the CCD’s size is 1.6 cm, the position measurement accuracy is 0.02 mm and the angle measurement accuracy is 9.5″. As a result, this system can meet the requirement of coaxiality measurement in lots of mechanical devices.Keywords：laser collimation;receiver lens;ray trace;position deviation;angle deviation- 29
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Published：2020-08-12 -
Damage detection and analysis of machined KDP crystal subsurface
Abstract：The subsurface damage of Potassium Dihydrogen Phosphate (KDP) crystal machined from line-incision to grinding and polishing was detected using section experiment and step etching experiment. The OLYMPUS MX40 optic microscope was used to observe the surface etching phenomena and the sub-surface micro-crack configurations, and to measure the micro-crack depth. The results show that the subsurface micro-crack configurations induced by line-incision is mainly of "bias-figure", and the max micro-crack depth is 85.59 μm. While by the #600 grinding wheel the max depth reduces to 8.55 μm. The square dislocations etching pits with high density are on (001) crystal surface and the low density etching pits with the figure resembled trapezium are on the tripler surface. This study affords a excellent detection and analysis method for the subsurface damage of KDP crystal machining.Keywords：KDP crystal;damage detection;micro-crack configuration;micro-crack depth- 35
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Published：2020-08-12 -
Calibration of mapping camera and cubic prism coordinate system
Abstract：A method for calibrating mapping camera and cubic prism coordinate system was introduced. The transformation matrix, calibration method and precision of the coordinate system were investigated. The relation of coordinate system was calculated, and the transformation matrix for coordinate system was established.Then, the angles between the mapping camera and the cubic prism coordinate system were tested by combining of high-accuracy 2D turntable, 0.5″ theodolite and autocollimation telescope. Finally, the calibration precision was analyzed. The error analysis indicates that the precision is smaller than 2″(1σ),which shows that the method can meet the requirements of calibrating mapping camera and cubic prism coordinate system and is valuable for practical application.Keywords：mapping camera;cubic prism;transformation matrix;calibration- 33
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Published：2020-08-12 -
Damage diagnosis for optical fiber grating smart structure based on wavelet packet analysis
Abstract：To realize the damage diagnosis of a optical fiber grating smart structure, the structual dynamic response signal was decomposed with the wavelet analysis method based on the vibration monitor of optical fiber grating smart structure.The wavelet packet decomposition was introduced, and the wavelet packet energy spectrum describing the damage character was used to identify the structual damage status. Then, six different damage circs were studied by experimental laminates, inculding the different degrees and the same location of structure damage, and different locations and the same degree of structure damage. The results show that the structure damage will lead to the increase of wavelet energy spectrum of some specifically frequency bands of the structure dynamic response signal, and the damage characters are sensitive to the damage degree, damage location and the degree from the damage to the sensor. In the experiment, this method can recognize the damage of 12 g weights and 30 cm from the optical fiber grating sensor, it is feasible to realize the structure on-line damage diagnosis.Keywords：optical fiber grating smart structure;damage diagnosis;wavelet packet energy spectrum- 50
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Published：2020-08-12 -
Effect of injection molding processing parameters on light guide plate with microsturcture array
Abstract：The influence of different processing parameters on the warpage and deformation of a 11 mm×3 mm×0.8 mm light guide plate with microstructure array was simulated by the MoldFlow MPI5. The optimized parameter of each factor’s contribution to the light guide plate with microstructure array was studied with orthogonal experimental method, and then the single factor experimental method was utilized to study the effect of different processing parameters on the warpage and deformation of the light guide plate with microstructure array. The results show that holding pressure contributes the most to the warpage and deformation (60.19%), and the injection time is the second one (13.13%). The single factor experimental simulation shows that the influence degree of process parameters on warpage can be ordered in pressure> injection time >holding time>melt temperature>cooling time. Therefore, the influence of different processing parameters on the injection molding of the light guide plate should be considered in priority, especially the holding pressure’s setting.Keywords：light guide plate;warpage;microstructure array;Injection Molding;simulation- 41
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Published：2020-08-12 -
Phase correction of quartering deviation of photoelectric rotary encoder
Abstract：The error of photoelectric rotary encoder mainly comes from interpolation. The quartering deviation of Moiré fringe of a rotary encoder is the most important part in interpolation error. The two methods of precise phase correcting are designed. Those correcting circuits are simple and efficient. The sine signal of encoder is regarded as phase reference(0°) ,the cosine signal can be separated into 0°and 90° vectors .The quartering deviation is created by 0° vector mainly. In this paper,the cosine signal is quartered to sine signal through compensating the 0° vector of cosine to reduce the quartering deviation. If the lower error is needed, the two signals, sine signal and inverting signal of sine, and cosine signal can be created, then the two signals can become quartering seriously though adjusting the value of cosine equal to sine signal. The experimental results show that the interpolation error is reduced from 1″ to 0.1″ after the precise phase correction.Keywords：rotary encoder;interpolation error;quartering deviation- 40
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Published：2020-08-12 -
Application of atmospheric pressure plasma polishing method in machining of silicon ultra-smooth surface
Abstract：Based on low temperature plasma chemical process, a novel non-contacting precision machining method, the Atmospheric Pressure Plasma Polishing (APPP) method, is developed. The APPP method utilizes the chemical reaction between the reactive plasma and the surface atoms to perform the atom scale removal process to avoid surface/subsurface defects. A self-fabricated system is built to implement this technology in the machining of ultra-smooth surfaces. As the key component, a capacitance coupling atmospheric pressure radio-frequency plasma torch is firstly introduced. By an atomic emission spectroscopic analysis, the atom component and relative densities of the plasma zone can be obtained. The subsequent theoretical analysis reveals that specific radical atom corresponds to certain electron transition state, which can indicate the different roles of various radical atoms in the reaction process. In initial operations, silicon wafers are machined as samples. Before applying operations, both the temperature distribution on the workpiece surface and the spatial flow field distribution in the machining process are studied qualitatively by finite element analysis. Then the subsequent temperature measuring experiments demonstrate the formation of the temperature gradient on the wafer surface predicted by the theoretical analysis and indicate a peak temperature about 90 ℃ in the center. Using a commercialized form talysurf, the machined surface is detected and the results show regular removal profiles coincide well with the flow field model. Moreover, the removal profile also indicates a 32 mm3/min removal rate. Using the atomic force microscopy (AFM), the surface roughness of 0.6 nm for the machined surface is also obtained. Then the element composition and proportion are detected and analyzed by an X-ray photoelectron spectroscopy (XPS). The results also demonstrate the occurrence of the anticipated main reactions. All the experiments have proved that this APPP method has a potential for fabrications of high quality optical components.Keywords：atmospheric pressure plasma polishing method;ultra-smooth surface;single crystal silicon;capacitance coupling- 31
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Published：2020-08-12 -
Design of heavy calibre and high precision cam-varifocal mechanism
Abstract：After analyzing the structure and finding the influence factors on the system precision,a slidable ball set of axis is added on the varifocal mechanism to solve the problem of bigger variation of optic axis in heavy calibre cam-varifocal system. By adjusting and measuring the structure, this method can control the variation of optic axis into 0.01 mm to meet the precision requirement in measurement system. The results show that the design of a heavy calibre and high precision cam-varifocal mechanism has been improved by the method of adding the sliable ball set of axis.Keywords：varifocal system;varifocusing;cam;variation of optic axis- 40
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Published：2020-08-12 -
Random vibration analysis of mechanically dithered ring laser gyroscope
Abstract：In order to research the performance of mechanically dithered Ring Laser Gyroscope(RLG) against the dynamic environment, the random vibration analysis is presented. The analysis method of structural random vibration response by the base excitationis described. The finite element model of mechanically dithered RLG is established and its modal analysis is performed by the finite element software ANSYS. It has been proved by the experiments that the model is reasonable and accurate,and the calculate error is less than 7%. The responses on axial and transversal random vibrations of mechanically dithered RLG are analyzed with the finite element model and the experiments and analysis results are compared. By analyzing the Power Spectrum Density (PSD) of acceleration response, the random vibration characteristic of mechanically dithered RLG is assessed. By analyzing the weakness of the present structure,an anti-vibration suggestion is put forward, which is useful to improve the structure design and reform for the further development of RLG.Keywords：ring laser gyroscope;random vibration;finite element analysis;Modal analysis- 45
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Published：2020-08-12 -
High-order resonance of three axis suspension wire actuator in optical pickup
Abstract：In order to improve the servo control bandwidth of the three axis actuator in a optical pickup, the high-order resonances in the focusing/tracking directions are studied. The induced mechanism, physical model, modal distribution and the test approach on the high-order resonance are studied. The low angle yawing model is established according to the actual stress on the three axis actuator. Then the modal distribution and modes are analyzed and calculated with the finite element method. Finally, the test method of the high-order resonance is introduced and the actuators with assemble errors are measured. The test results show that the pitching resonance usually appears on the focusing performance curve under the frequency of 1 700 Hz and the yawing resonance usually appears on the tracking performance curve under the frequency of 4 800 Hz. The experiment results are consistent with the finite element analysis. The results also show that the high-order resonance is the inherent attribute of the three axis actuator,which can be restrained by reducing the assemble error of the three axis actuator.Keywords：optical pickup;three axis suspension wire actuator;high-order resonance;finite element method;modal distribution- 28
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Published：2020-08-12 -
Design for negative pressure flatten system in aerial frame film camera
Abstract：Flatten precision is one of the important factors effecting on camera's resolution. It is required that the film in a aerial camera with long focus, wide frame and high resolution should be flattened on film board quickly and precisely during exposure time. Aiming at the film size of 114 mm × 114 mm, flatten precision of 0.034 mm and absorption time of 420 ms,this paper introduces a perfect film flatten system, and provides a method for flattening the film on the film board using negative pressure. The constitution and operating principle of this system are introduced, the structural style of film board is clarified and the choice basis of key devices are obtained by analyzing and computing.The results show that the proposed method is a excellent optical method used to analyze flatten precision,which can meet the demand for aerial frame film camera.- 20
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Published：2020-08-12 -
Calculation and compensation for image motion of aerial remote sensor in oblique situation
Abstract：The forward motion and attitude variation of the aircraft can cause a deviation between the optical axis and the light emitted from the object on the ground, which produces conjugate point movement and image motion on imaging medium. By using the method combining light vector with optical axis revolution,aiming at the translation between object and optical axis and the deviation of the optical axis direction caused by the attitude variation of the aircraft, the relationship between light vector and optical unit vector is obtained,and the mathmatical model for image motion compensation is established. The image motion of remote sensor is analyzed and calculated with measured parameter and the method of image motion compensation is given. The results show that the method integrates forward image motion with attitude image motion, which is easy to calculate and can be applied in the research of aerial remote sensor.Keywords：image motion compensation;aerial camera;coordinate system rotation;forward motion compensation- 49
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Published：2020-08-12 -
Estimation of TDI direction of CCD sensor in aerial camera by graphing method
Abstract：Time Delay and Integration CCD(TDI CCD) is a kind of CCD with frame structure and linear output, its charge transfer has certain directivity. Therefore, CCD integral direction and TDI CCD imagery heading must maintain certain relation for imaging. This article takes a push-broom and a whiskbroom scanning camera as examples,and introduces a graphing method based on Guassian imaging system to determine the relation between TDI CCD integral direction and sensor imagery heading. The conclusion is that integral direction must be in accordance with image motion direction. The result shows that this method is intuitional, practical and easy to determin TDI CCD integral direction,which is suitable for the practical engineering design.Keywords：Time Delay and Integration CCD(TDI CCD);TDI direction;image motion direction;graphing method- 58
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Published：2020-08-12 -
Attitude compensation of frame aerial camera based on spot mode
Abstract：The spot mode is one of the operation methods used in frame aerial cameras. The mode can point at interest objects via rotating scan mirror in position angle and depression angle directions and can view objects from different directions. In this paper,the geometrical model of a camera is presented and the relative coordinate axes are chosen. Then, a mathematical model for computing the image velocity from track coordinate system to image plane coordinate system is established. To compute the compensation velocity,the object velocities under aircraft coordinate axes and the velocities under compensation coordinate axes are computed and the visual axis length is also calculated,then the compensation angle velocity is obtained. Finally, the image plane revolution mechanism's function is explained in detail. The scan mirror and image plane revolution mechanism are incorporated in frame attitude compensation method based on spot mode. The numerical values calculated by coordinate conversion will provide the references for IMC engineering application.- 60
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Published：2020-08-12 -
Balanced multiwavelet aviation image compression coding based on EBCOT
Abstract：Since pre-filter is more likely to cause the orthogonality and symmetry "losses" of multi wavelet, and to cause the increase of the compact support of the base function, a multiwavelet "balanced" algorithm is proposed to make multiwavelets have the same properties with single wavelets.Taking full advantages of the structures of balanced multiwavelet decomposition coefficients, the Embedded Block Coding with Optimal Truncation(EBCOT) image coding algorithm is used to compress the coefficients of balanced multiwavelet. When the compressed ratio reaches 32, the PSNR is 31.342 7. The experimental results show that the balanced multiwavelet algorithm based on EBCOT has many good characteristics, such as orthogonality, short support, high vanishing moments, etc., which is a more effective method for aviation image compression.Keywords：banlanced multiwavelet;EBCOT;aviation image;image compression- 49
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Published：2020-08-12 -
Analysis on resonance of air-borne opto-electronic tracking turntable and design of adaptive filter
Abstract：According to the characteristics of an air-borne opto-electronic tracking turntable and mathematics model of tracking turntable, a new adaptive filter based on angle changes of tracking turntable is presented to restrain the mechanical resonance of the opto-electronic trackng turntable under the conditions of mechanical structure and damp unchanged. The experiment results indicate that the maximum automatic traking error improves 3'. The proposed algorithm is a fast and stable algorithm, which can satisfy a real-time adaptive filter and restrain mechanical resonance perfectly. At present, this method has been applied to certain type of air-borne tracking turntable successfully.Keywords：air-borne opto-electronic tracking turntable;mechanical resonance;servo system;adaptive filtering- 32
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Published：2020-08-12
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