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Issue 8 ， 2007
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Characteristic test of SiC for space camera's mirror
Abstract：The performance data of SiC materials were obtained by processing and polishing SiC and testing its reflectivity,and the advantages and disadvantages of some fabrication methods of SiC mirror roughcast were analyzed. The reflectivity of SiC specimen was tested under different conditions of surface processing including Si-coated or Ag-coated surfaces and Ag-recoated on Si-coated surface with Lanmda-9 Spetrophotometer. The highest reflectivity is 98% under the condition of recoated Ag on coated-Si surface. Domestic long strip SiC mirror was polished and tested. The result shows that the surface roughness is 6.27 nm with Wyko interferometer. As a reflection mirror of off-axis three reflect optics system,the material performance was validated in a mirror surface figure with PV value of 0.068 λ, and RMS of 0.01 λ (λ=632.8 nm),the results indicate that performance of SiC can meet the requiremerits of the space camera's mirror.Keywords：space camera;mirror;reflectivity;silicon carbide (SiC);surface roughness- 46
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Published：2020-08-12 -
Topologic optimization design for main supporting structure of space camera
Abstract：In order to obtain a lightweight and high-stiffness main supporting structure of space camera, a topologic optimization design method of space camera was presented. Based on the method, two kinds of main supporting structures of space camera with Cassegrain and TMA optical systems were optimized using Finite Element Method(FEM). Compared with before optimization, the first -order natural frequency of the main supporting structure of Cassegrain optical system raises from 41 Hz to 72 Hz with 15 percent weight lost,and the main supporting structure of TMA optical system loses 35 percent weight without changing the first-order natural frequency. The numerical results indicate that after adopting the topologic optimization design method, not only the design period is shortened, but also the supporting structure weight is effectively reduced and the capability of the main supporting structure is enhanced also,Which shows that optimized support structures can meet the system design requirements.Keywords：space camera;topology;optimal design;FEA- 42
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Published：2020-08-12 -
Modal calculation and test of truss in space remote sensor
Abstract：In order to launch the space remote sensor sucessfully, the modal characteristic of a truss for enduring the dynamic load was calculated by Finite Element Method(FEM), and the modal test was done by the hammer beat method. The calculated and tested frequency result was compared, and the visual comparing method and the Modal Assurance Criterion( MAC ) were employed in the relativity analysis of the modal shape. Experimental result shows that the first-order order frequency of the truss is 154 Hz, which satisfies the design requirement above 140 Hz,and the calculated error of the FEM is less than 10%. There are some shape relativity less than 0.5 in partly,so the FEM model needs to be modified for the following engineering use.Keywords：space remote sensor;truss;modal analysis;experiment;correlation analysis- 34
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Published：2020-08-12 -
High volume fraction SiC/Al composites for space-based optomechanical structures
Abstract：Using the special self-manufactured processing equipment, we fabricated the aluminium matrix composites with high volume fraction (55%~57%) SiC particles based on a novel pressureless infiltration fabrication technology. The microstructures, mechanical and physical properties, fracture mechanism of the composites were characterized. Additionally, several kinds of typical optomechanical components for space-based optical systems were produced successfully by means of electromachining (such as wire electrical discharge), grinding , abrading, etc. The investigation reveals that the composites have good mechanical properties, such as ultra-high modulus (the Young’s modulus is 213 GPa, the specific modulus is approximately as three times as Al, Ti, and steel), as well as prominent thermal management function(low thermal expansion coefficient (8×10-6 K-1), and very high thermal conductivity (235 W/m·K)). Experimental results show that the new multi-function and lightweight SiC/Al composites can be used in the optomechanical systems in the space field to improve greatly the thermal management effect and to sharply decrease the whole weight of the space-based optomechanic structure.Keywords：SiC/Al composite;high volume fraction;pressureless infiltration;space-based optomechanical structure- 65
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Published：2020-08-12 -
Application of carbon fibre reinforced composite to space optical structure
Abstract：The mechanical properties of carbon/epoxy composites and their Coefficient of Thermal Expansion(CTE) were tested and the material property after radiation in space was tested. Finally, a processing method of carbon/epoxy composites in the application of space optical structure was studied. The research results show that the weight of optical structure made from carbon/epoxy composite with high specific strength and stiffness can be reduced more 30% than that of aluminum alloy. The CTE of carbon/epoxy composites can be designed as "zero" or "negative" in a certain direction according to requirement. Carbon/epoxy composites have excellent performances under the condition of radiation in space,so that they have a wide application in space optical structure. The experiments give several conclutions, which is Total Mass Loss(TML) of 0.15%,Collected Volatile Condensable Materials(CVCM) of 7.66×10-5 g/g, and Water Vapor Regained(WVR) of 0.12%.Keywords：carbon/epoxy;Composite;space structure- 52
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Published：2020-08-12 -
Radiation transfer characteristic and calibrating method for space optical remote sensor
Abstract：Being influenced by background radiation and opto-electrical response characteristics, the original digital image acquired by space optical remote sensor is very different from radiance image of real target. Therefore, the response function between input radiance and image grey level is established by calibrating the optical remote sensor to perform radiance image retrieval and radiation calibration. According to radiation transfer and conversion process of remote sensing signal, the physical concept of radiation response function is described using the model of Taylor progression and metric function, and a multiple regression analysis method for solving metric function is put forward. By applying a integrating sphere expanded radiation source, a civil camera is calibrated in Lab, and the response function is obtained. The result shows that the proposed method is feasible and practical. At last, the problem about physical meaning of radiation response function and radiometric precision are discussed.Keywords：optical remote sensor;space camera;radiometric calibration;radiance retrieval- 42
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Published：2020-08-12 -
Design of analog front end of CCD imaging system
Abstract：The analog front end of a CCD imaging system is critical to the signal noise ratio of the camera. In order to increase the signal noise ratio of the imaging system,the layout and the PCB routing of the analog front end must be properly designed. Thus,based on analysis of the function of every part of the analog front end and design scheme of a specified CCD video signal processor, the power supply and grounding model of the specified CCD video signal processor with the analog and digital mixed signal device was established. And according to this model, the layout and PCB routing for the analog front end were analyzed and designed. The result shows that the signal noise ratio of the system could be up to 54 dB when the pixel clock is 6 MHz.Keywords：CCD;imaging system;analog front end;high-speed camera;low noisy- 39
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Published：2020-08-12 -
Noise analyzing and processing of TDI-CCD image sensor
Abstract：In order to improve TDI-CCD performance, the noise in TDI-CCD image was analyzed and categorized according to the operating principle of TDI-CCD. TDI-CCD noise mainly comes from two ways, one is TDI-CCD proper noise, such as photo shot noise、non-uniformity noise、dark current noise、fix pattern noise、transfer noise and so on, the other is TDI-CCD noise interference in work process, such as reset noise and 1/f noise.Several noise processing methods were presented based on noise charateristics and the signal processing schemes of double-correlated sampling were given to eliminate KTC noise. As a result, the output SNR of TDI-CCD has reached up 53.8 dB.Keywords：TDI-CCD;Image Sensor;dark current noise;KTC noise;correlated double sampling (CDS)- 41
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Published：2020-08-12 -
Focusing properties of Gaussian beams through a telescope-lens compound system
Abstract：The beam conversional properties of Gaussian beams through a telescope-lens system were deduced based on parameter q and ABCD law. The properties of the system were simulated and calculated, and the results were testified by the focusing experiment through a He-Ne laser with plate-cocave cavity. The focusing beam radius' ratio between the telescope-lens compound system and the single lens increases via length (70~400 mm) increasing, and the maximum ratio is 30, meanwhile the ratio between the telescope-lens compound system and the single lens decreases via length (70~400 mm) shorting, but the maximum difference of the focusing beam radius’ is 0.043 μm. Experiment results suggest that choosing the telescope-lens compound system as focusing optical elements and setting the length in the shortest or zero will get a upstanding focusing purpose.Keywords：Gaussian beam;telescope-lens compound system;focusing property- 30
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Published：2020-08-12 -
Highly efficient photonic crystal-based multichannel drop filters with reflection feedback
Abstract：Photonic crystal filters have great potential of application in optical communication but a common 2D photonic crystal-based multichannel drop filter is hard to be put into application because the drop efficiency is not high enough. In this paper,we propose two kinds of novel drop filters by putting new structure into common model. One of the novel improved configurations has reflection micro-cavities in the end of waveguide,the other has reflection micro-cavities in two sides of bus waveguide. By analyzing the propagation of light-waves in these structures with finite difference time domain(FDTD) method and giving the schematic diagram of wave propagation,it can be proved that the two novel configurations have capability to decrease the light loss and increase the drop efficiency,obviously. The drop efficiency of the novel filters can achieve 60%~90% theoretically,which is much higher than the level of common filters in drop efficiency of 30%~40%. It is also shows that reflection micro-cavities have great effect on the improvement of the photonic crystal-based filters.Keywords：photonic crystal;multichannel drop filter;reflection micro-cavitiy;finite difference time domain (FDTD) method- 32
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Published：2020-08-12 -
Calibration of 200~300 nm spectral irradiance using 150 W deuterium lamp
Abstract：A calibrating method for the irradiance responsivity of 200~300 nm spectral instruments using 150 W deuterium was introduced in detail. This method overcame the troubles caused by the weak ultraviolet response of most spectral radiometer and poor signal-to-noise ratio. A spectral irradiance calibration unit based on parallel light was established to meet the calibration conditions of some remote sensing spectral radiometers. The calibration unit got the standard value of spectral irradiance by irradiance transfer, which avoided the difficulty of spectral reflectance measurement of the concave mirror. Using the unit and a FEL lamp from NIST to calibrate the same ultraviolet radiometer, the results show that the bias between them is 3%, and the error of spectral irradiance calibration is 4.7% in range 200~300 nm.Keywords：deuterium lamp;spectral radiometer;irradiance transfer;irradiance calibration- 24
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Published：2020-08-12 -
Optical implementation of (3,3,2) rectangular CC-Banyan network
Abstract：A (3,3,2) rectangular CC-Banyan network was studied. According to the construction principle of the CC-Banyan network, the topological graph of (3,3,2) rectangular CC-Banyan network was obtained,and then the routing rule of (3,3,2) rectangular CC-Banyan network was presented. Finally, a optical experimental setup of (3,3,2) rectangular CC-Banyan network was designed. Each stage of node switches consisted of a phase spatial light modulator and a polarizing beam-splitter, and the connection of neighboring stage was performed by a fiber. The theoretical analysis and experimental result show that the experimental setup can realize these functions including optical signal sorting and permuting etc., which also can be used in the fields of optical communication and optical information processing.Keywords：optical communication;optical network;Banyan network;phase spatial light modulator;polarizing beam-splitter- 21
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Published：2020-08-12 -
Separation and optimization of posture errors in optical aspheric coordinate measurement
Abstract：Based on the development of a new special-purpose optical aspheric coordinate measurement machine, the effect of the relative posture errors between the measurement system and the workpiece in 6 degrees was researched, and its mathematical model was established. With a model parameter estimation method, the least square (LS) optimal model was established based on the measuring data and the nominal surface, and then the LS estimations of the posture errors were obtained to correct the measurement result. The experimental results indicate that the method can eliminate the effect of posture errors and increase the reliability and accuracy of the measuring data, which ensures the measurement system in a repeatability of 0.3 μm and an accuracy of 0.5 μm.Keywords：optical aspherics;coordinate measurement;posture error;model parameter estimation- 42
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Published：2020-08-12 -
Design and test of reference mirror in 300 mm interferometer
Abstract：In order to find an optimal supporting scheme for the reference mirror in a 300 mm interferometer, horizontal supports were modeled and analyzed in adhered spot edge support and band-back support using finite element method. For the sake of simplicity and economy, the ringy-band support with 10 mm wrap bandwidth was accepted to optimize the design, the ideal surface deformation of the reference mirror due to self-weight was obtained in the optimal support scheme. According to this result, a certain allowance was given for deformation when the mirror blanks were polishing. Then the surface of this mirror under practical condition was measured through building absolute liquid reference. By comparison, the differences of PV magnitudes and RMS values are only 0.008 λ and 0.005 λ, respectively. It is clear that the structural design of the interferometer reference mirror meets technical requirements very well. At last, several suggestions were given to eliminate the effects of thermal turbulence.Keywords：applied optics;large-aperture interferometer;reference mirror;mirror support;finite element method- 39
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Published：2020-08-12 -
Precision tracking and experimental optimization of GMA by Preisach inverse compensation
Abstract：In order to realize high precision tracking control of the Giant Magnetostrictive Administer(GMA), a numerical compensation approach was presented based on inverse Preisach model and a series of optimized experimental methods were discussed. The numerical expressions of the classical Preisach model were presented in detail for different input variations and the inverse classical Preisach model was established. The First Order Descending(FOD) datasets were obtained from the identification experiments and smoothed by a FFT filter. A good agreement between measured hysteresis loops and predicted curves shows that the FFT filter is an effective tool to cancel the errors and noises of the FOD datasets. In the tracking experiments, the Preisach inverse model was used to compensate the hysteresis of GMA to obtain a good tracking performance. On a moving range of 0~34 μm, the tracking error of the GMA with compensation is less than -2.9%~+2.7%, compared with the error of -14.7%~+11.2% without compensation. The experimental results indicate that the compensation approach based on numerical inverse Preisach model can greatly improve tracking performance of GMA, and the optimized experimental methods are effective.Keywords：GMA;inverse Preisach model;open loop feedforward compensation;tracking and controlling- 44
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Published：2020-08-12 -
Electro-magnetic tracking system for capsule-typed telemetric device
Abstract：An electro-magnetic tracking method was proposed. Putting several circular current loops on body surface, a well-designed receiving coil in the capsule can always keep its orientation. Through detecting the magnetic field strength by a receiving coil, and deducing the functional relationship between the position parameters of the coil and the magnetic field strength, the position of the capsule can be determined. This design not only simplifies the structure of the whole system compared with a common one, but also makes the arithmetic easy for ensuring its feasibility in application of capsule positioning. The transmitting and receiving system and a three-coordinate experimental device were constructed. A test including 38 points was carried out to verify the method and the system. The result shows that the maxim positioning errors of x, y, z coordinates are less than 4 cm, while the mean errors are less than 2 cm, which is better than current precision of other positioning methods for the capsule-typed device.Keywords：capsule-typed telemetric device;tracking and positioning;electro-magnetic tracking;positioning error- 55
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Published：2020-08-12 -
Optimum reliability distribution of precise conveying robot system based on precision and cost controls
Abstract：A optimum reliability distribution method of precise conveying robot system based on precision and cost controls was proposed. The method sets up a reasonable and effective system reliability optimum distribution mathematic model using network system optimum principle to adjust the relation among system precision, reliability, and cost, and to meet the requirements of reliability and precision. The method also deploys the mixed successive coordinating method to solve proposed mathematical model. The research results achieve the optimum reliability distribution of the robot system and show that the method can be used in reference on setting up optimum reliability distribution of 6 or more dimensions for a precise conveying robot system or more-complicated large systems.Keywords：precise conveying robot;precision and cost controls;reliability;successive coordinating;optimum distribution- 36
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Published：2020-08-12 -
A novel background modeling method based on color grade of different frames
Abstract：Based on the analysis of some feature videos of traffic scene, the values of background pixels are obtained according to variety of pixel colors in video flows. A modeling method of estimating background pixels using color grade of different frames is proposed. The image is divided into some sub-regions in computing, and every sub-region background is gotten according to variety of color grade, then the background image is rebuilt according to the computing results of every sub-region. Experimental results show that the process of background modeling can be completed after computing average initial 100 frames, which is less than that of other methods,and the average computing time of every frame is 15.566 ms. The speed of modeling and the number of initial frames can meet the requirements of the video surveillance system in traffic scene using this method.Keywords：traffic monitoring and controlling;background modeling;image processing- 39
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Published：2020-08-12 -
Evaluation of efficiency for silicon wafer cleaning by image processing
Abstract：Based on Image Processing Toolbox of Matlab technique, a new evaluation method of cleaning efficiency is presented in dry laser cleaning particles of silicon wafer surface. Image Processing Toolbox of Matlab is used to recognize optical information of silicon wafer surface before and after laser cleaning and the evaluating programs are developed to count the number of pollution particles on the silicon wafer and to evaluate the cleaning efficiency. The results show that the statistical accuracy of the method is 97.6%,and the laser cleaning accurate reaches 99.2%. The research achievement offers a effective,rapid and accurate new evaluation method.Keywords：laser cleaning;silicon wafer;cleaning efficiency;image processing- 37
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Published：2020-08-12 -
Exterior parameter estimation for aerial camera based on Hough transform
Abstract：A new approach for exterior camera parameters estimation based on Hough transform is presented.By using the collinear equations to model the camera and combining the feature points on the image plane and in the object space to set votes for a certain point in the discrete parameter space, the point with the maximum number of hit is defined the right parameter. An iterative estimation procedure is adopted to process the nonlinearity in the collinearity equations and the correlation of the exterior parameters. Unlike the conventional methods, the new technique can estimate the exterior parameters without making a correspondence between the feature points on the image plane and in the object space. Two experiments are carried out to examine the validity of the proposed algorithm. Experimental results show that the errors of the camera coordinates and the pose angles are less than 15 m and 1° respectively. The estimated parameter results can meet the requirements of the combat using ship borne guns.Keywords：aerial camera;exterior parameter;collinearity equations;Hough transform- 45
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Published：2020-08-12 -
Image simulation system of dynamic infrared point targets sweeping on sea surface
Abstract：An image simulation system of dynamic infrared point targets sweeping on sea surface is established.Because of a great deal of image data and targets of Infrared Rearch and Trcking(IRST) system, a method combining software with hardware is presented to solve the problems of real-time simulation. Aiming at long-distance dynamic infrared point targets, the infrared point targets and small targets are mainly simulated. The simple and practical models of background grey degree based on Gaussian distribution, dynamic infrared point target grey degree and running track are established. By adjusting average value and mean square difference, simulating background grey degree signal approaches to actually observing infrared image signal. The resuts show that the system can be used to test the ability of signal processing and target extraction for IRST in condition of limit background noise, also can ensure the effectivity of performance parameter of IRST system and reduce test cost and shorten development period.Keywords：infrared point targets;image simulation;simulation system;IRST system- 46
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Published：2020-08-12 -
Electronic image stabilization for aerial E-O imaging system
Abstract：An approach of electronic image stabilization is presented for the E-O imaging system of airborne platform to restore the video image degraded by both intraframe motion-blurred and interframe vibration. The 2D motion-blurred point spread function (PSF)is set up by a motion-blurred mathematical model,then Wiener filter is used to restore the intraframe motion-blurred video images. A gray projection algorithm is presented to estimate the motion vector between the current frame and the reference frame in video image sequence, which is used to compensate video image sequence to make the video image sequence output stable. The experiment results show that the proposed approach has feasible, quick and accurate characteristics,which can improve the peak signal noise ratio(PSNR) effectively and reach the accuracy of 1 pixel, also can improve imaging quality and ensure video image sequence output clearly and stably.Keywords：airborne platform;E-O imaging system;electronic image stabilization;motion-blurred;interframe stabilization- 70
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Published：2020-08-12 -
Real-time restoration for motion blurred in aerial E-O imaging system
Abstract：Based on the conjugate symmetric frequency spectrum of Complex Discrete Fourier Transformation (CDFT) and the conventional Real Discrete Fourier Transformation(RDFT),a modified RDFT is implemented in Wiener filter to restore aerial images degraded by motion or vibration. A horizontal rectilinear motion blurred image of 512×512 size and 8 bits as the test image in experiment can be restored by one dimensional Wiener filter and improved RDFT in 19 ms by an Intel Pentium 43.0 GHz CPU to meet real time requirement. Experiment results show that the modified RDFT efficiently reduce the data in the frequency spectrum of CDFT,which halves the storage space and nearly doubles the computational speed of the image restoration by Wiener filter. Meanwhile,compared with CDFT,the improved RDFT does not lose the data of frequency spectrum in the same restoration precision.Keywords：aerial imaging;real discrete Fourier transformation;Wiener filter;image restoration- 52
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Published：2020-08-12 -
Stabilization properties of airborne imaging platform based on position gyro and rate gyro
Abstract：Generally,a photoelectric imaging platform is used to isolate the carrier movement and set the platform stability relative to the inertial space. The high frequency jitter phenomenon of the target in the image center occurred in the rate gyro based platform is researched during tracking. The theoretical derivation and numerical analysis indicate that the reason is the torque rigidity of 0 and isolation degree of 71.4 dB for the rate gyro based platform, while the position gyro based platform has greater torque rigidity and isolation ability,which can greatly suppress this jitter.Keywords：airborne platform;stabilization platform;gyro;torque rigidity;isolation degree- 54
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Published：2020-08-12 -
Digital controller for aerial camera with despun control
Abstract：The principle of the despun digital control of a CCD camera is introduced,and a maximum rotational speed for assuring an ideal image in despun control system is obtained by analyzing the system. According to the speed of the despun control, a digital controller of camera for despun control system is design by taking a DSP as its core, a velocimeter as speed sensitive element to offer feedback for velocity loop in the system,and perturbation frequency measured by rate gyroscope as a feedforward function. The experiment results show that the velocity meets the demand of despun controll for its good image quality and the precision standard of 14.3(°)/s. Theoretical and lab researches both prove the feasibility of the despun control system.Keywords：photoelectric imaging;despun control;CCD camera;rate gyro- 41
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Published：2020-08-12 -
Target self-determination orientation based on aerial photoelectric imaging platform
Abstract：In order to enhance the ground object orientaton accuracy of a aerial photoelectric imaging system,a self-determination orientation method is proposed,in which the GPS system and aviotion posture measurement system are directly fixed on aerial photoelectric imaging platform to realize the target orientation combing with the platform. The analysis of the effect factors on the orientation accuracy shows that self-deternunation orientation method can eliminate the error of the traditional method brought by a absorber. Generally,the accuracy of self-determination orientation system is at least 25% higher than that of the aircraft system.Keywords：aerial photoelectric platform;self-determination orientation;coordinate transformation;orientation accuracy- 42
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Published：2020-08-12
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