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    Low-light Image Enhancement Method Using Retinex Method Based on YCbCr Color Space
    TIAN Hui-juan, CAI Min-peng, GUAN Tao, HU Yang
    Acta Photonica Sinica    2020, 49 (2): 210002-0210002.   DOI: 10.3788/gzxb20204902.0210002
    Abstract632)      PDF (11452KB)(144)       Save
    Aiming at the problem of illumination image estimation in low-light image enhancement algorithm of the Retinex model, a low-light image enhancement method based on YCbCr color space is proposed. The original low-light image is transformed from RGB (Red Green Blue) color space to YCbCr color space. The Y component in YCbCr color space is extracted and the initial illumination map L1(x,y) is constructed. The enhanced illumination image L2(x,y) is obtained by the gamma transformation of L1(x,y), the enhanced image R(x,y) is obtained according to the Retinex model, and we use a multi-scale approach to boost the details of the image R(x,y) and obtain the final enhanced image Re(x,y).The experimental results show that, the method can not only effectively improve the brightness of the low-light images, enhance the details of the image, obtain a better visual effect with fewer color and lightness distortions, but also has a faster running speed.
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    Study on Stability of Thermally Activated Delayed Fluorescent OLED
    ZHANG Wen-wen, CHEN Zhuo, LI Ge, YAN Xue-wen, JIAO Bo, WU Zhao-xin
    Acta Photonica Sinica    2020, 49 (1): 123001-0123001.   DOI: 10.3788/gzxb20204901.0123001
    Abstract466)      PDF (4052KB)(214)       Save
    The Thermally Activated Delayed Fluorescence Organic Light-Emitting Diodes (TADF-OLEDs) was fabricated, using bipolarmaterial 4,4'-bis (carbazol-9-yl) biphenyl (CBP) as host, green fluorescent material (4 s,6 s)-2,4,5,6-tetra (9H-carbazol-9-yl) isophthalonitrile (4CzIPN) as dopant. The device structure was optimized by adjusting concentration of 4CzIPN doped into CBP, then the photoelectric properties and lifetimes of device were studied. The performance of 12% 4CzIPN-doped device is the best. To study the influence of driving mode on device lifetime of the TADF-OLEDs, the AC driving circuit of positive constant current reverse constant voltage was designed, and the parameters of the AC driving circuit were optimized and adjusted. Research shows that the TADF-OLED achieved a longer device lifetime under AC driven of frequency of 50 Hz, reverse bias of 0 mV and duty cycle of 50%. By comparing the lifetime curves of the same device driven by DC and AC, it is found that the TADF-OLED lifetime under the AC driving scheme is about 1.5 times longer than that of under the DC driving scheme.
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    Underwater Optical Image Enhancement Based on Dominant Feature Image Fusion
    LIN Sen, CHI Kai-chen, LI Wen-tao, TANG Yan-dong
    Acta Photonica Sinica    2020, 49 (3): 310003-0310003.   DOI: 10.3788/gzxb20204903.0310003
    Abstract455)      PDF (30067KB)(149)       Save
    Aiming at the problems of color distortion, uneven illumination and low contrast of underwater optical image, an underwater optical image enhancement algorithm based on the fusion of dominant feature image was proposed. Firstly, an improved dark channel prior algorithm was proposed to remove the uneven turbidity and balance the color in the degraded image. Secondly, the adaptive gamma correction algorithm based on weighted distribution and the contrast limited adaptive histogram equalization-homomorphic filtering algorithm were used to enhance the contrast of color correction image and make its brightness distribution uniform. Finally, the associated weight maps of the three fused images namely the color-corrected image, the brightness-balanced image and the contrast-enhanced image were defined, and the fused images were obtained by the multi-scale fusion algorithm. Compared with single preprocessing algorithm which can only solve the corresponding degradation phenomenon, the algorithm processes single degraded image with multiple algorithms and obtains three dominant feature images, the combination of different weights can combine the dominant features to the greatest extent, and the comprehensive effect is far beyond the optimization effect of each single algorithm, and is no longer limited to solving single problems such as color distortion. The algorithm in this paper is compared with existing algorithms in subjective evaluation and objective evaluation. The results show that the algorithm can effectively balance the chroma, saturation and sharpness of underwater images, and the visual effect is close to the images in natural scenes.
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    Feature Enhancement SSD Algorithm and Its Application in Remote Sensing Images Target Detection
    SHI Wen-xu, TAN Dai-lun, BAO Sheng-li
    Acta Photonica Sinica    2020, 49 (1): 128002-0128002.   DOI: 10.3788/gzxb20204901.0128002
    Abstract438)      PDF (5516KB)(189)       Save
    In order to improve the detection accuracy of multi-scale remote sensing ship targets in complex scenes, a feature enhancement single shot multi-scale detector is proposed. Firstly, the shallow feature enhancement module is designed to improve the feature extraction ability of the shallow network in the pyramid structure of Single Shot MultiBox Detector(SSD). Then the deep feature fusion module is designed to replace the deep network in the pyramid structure of SSD to improve the feature extraction ability of deep network. Finally, the image features are matched with candidate frames of different aspect ratios to adapt to remote sensing image targets of different scales. The experiments tested on the optical remote sensing image dataset demonstrate that the proposed method can adapt to target detection under different background and effectively improve the detection performance of multi-scale remote sensing targets in complex scenes. On the extended experiment, the proposed method performance over SSD in blurry target detection.
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    Influence of Cylindrical Photoacoustic Cell Structure and Environmental Factors on Acoustic Eigenfrequency
    CHENG Gang, CHEN Jia-jin, CAO Ya-nan, TIAN Xing, LIU Kun, CAO Yuan
    Acta Photonica Sinica    2020, 49 (2): 230001-0230001.   DOI: 10.3788/gzxb20204902.0230001
    Abstract424)      PDF (2756KB)(105)       Save
    Taking the typical cylindrical photoacoustic cell as the research object, the accurate finite element model of photoacoustic cell acoustic simulation is established. On this basis, the structure parameters of resonant cavity, buffer cavity, intake and outlet holes, as well as temperature and humidity in the photoacoustic cell are studied. The influence of factors on its acoustic eigenfrequency is discussed. The results show that the inlet and outlet holes of a cylindrical photoacoustic cell are insensitive to its acoustic eigenfrequency, and can be neglected in design calculation. The length of the resonator is the most sensitive, followed by the diameter of the resonator. The simulation results also show that the length and diameter of the buffer chamber have a certain influence on it, so it needs to be taken into account when calculating accurately. The influence of temperature and humidity on the acoustic eigenfrequency of photoacoustic cells shows a positive linear growth law. The sensitivity of temperature effect decreases with the increase of resonator length, and the sensitivity of humidity effect decreases with the increase of temperature. When calculating the acoustic eigenfrequencies of photoacoustic units, the effect of humidity can be neglected under room temperature and low humidity.
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    Thermo-optic Effect of Optical Microsphere Cavity for Temperature Sensor Research
    LIN Xiao-jun, LIN De-quan, LIAO Ting-di, DUAN Ya-fan, HUANG Yan-tang
    Acta Photonica Sinica    2020, 49 (3): 314004-0314004.   DOI: 10.3788/gzxb20204903.0314004
    Abstract415)      PDF (5458KB)(102)       Save
    In order to study the thermo-optic effect of the optical microsphere cavity, two kinds of pump sources, 1 550 nm band tunable laser and broadband light source, were used to measure the change of the resonance peak wavelength of silica, tellurite glass microsphere and rare earth ion doped microsphere when the excitation light power and environment temperature change. The excitation power sensitivity of the silica microspheres was 32.4 pm/mW and the temperature sensitivity was 13.4 pm/℃. For the thulium ions doped silica microsphere, the sensitivity of excitation power was 48.7 pm/mw and the sensitivity of the environment temperature was 15.2 pm/℃. The excitation power sensitivity of the tellurite microsphere was 71.1 pm/mw, and the temperature sensitivity was 0.019 1 nm/℃, which was nearly one times higher than that of the FBG temperature sensor (10 pm/℃). If the rare earth ions were doped, the sensitivity was 1.1 times higher. The results have reference significance for the microcavity applications of the temperature sensor.
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    Research on Star Tracker On-orbit Low Spatial Frequency Error Compensation
    JIN He, MAO Xiao-nan, LI Xin-peng, YU Lu-wei, REN Ping-chuan
    Acta Photonica Sinica    2020, 49 (1): 112005-0112005.   DOI: 10.3788/gzxb20204901.0112005
    Abstract407)      PDF (6958KB)(72)       Save
    An on-orbit low spatial frequency error compensation method has been proposed to restrain low spatial frequency error brought by the difference between on ground calibration and on-orbit environment. Firstly, principle points, initial value of focal length and distortion coefficients are calculated during on-ground calibration. Then, focal length is updated by extended Kalman filter based on angle distance error minimization criterion using selected star pairs during on-orbit calibration. Faster convergence rate and better robustness has been validated by simulation. Sky tests data and on-board data proved that the mean value of angle distance error can be decreased by more than 90% and the low spatial frequency error decreased by more than 40%.
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    Polarization-controlled Optical Switch Based on Surface Plasmon
    LI Gang, GUAN Wen-jun, ZHANG Yan-jun, LIU Yan-li, HOU Yu-long, SHAN Yan-hu, ZHANG Zhi-dong, ZHANG Bin-zhen, XUE Chen-yang
    Acta Photonica Sinica    2020, 49 (3): 326001-0326001.   DOI: 10.3788/gzxb20204903.0326001
    Abstract398)      PDF (18250KB)(134)       Save
    An optical switch based on polarization state control is designed by using a rectangular-like nanorods tetramer composed of four Au nanorods. The finite element method is used to study the response characteristics of the structure to incident light polarization. It is found that the transmission spectrum of the structure dependent strongly on the polarization direction of the incident light. When the polarization angle of the incident light changes by π/2, the switching ratio of the characteristic peaks can reach 27.81 dB and 21.65 dB, respectively. The analysis shows that the switching effect is mainly caused by the different near-field coupling strength between the horizontal double rod and the vertical double rod at the different polarization states. The relationship between the transmittance and the polarization angle of the structure obeys the Malus law. In addition, the influence of structural parameters on the response characteristics of optical switches is studied by changing the structural parameters of the rectangular-like nanorod array. On this basis, the influence of the periodic parameters on the transmission spectrum of the unit structure under the horizontal and vertical polarization of the incidence light is studied by changing the period parameters of the array. These results can provide a theoretical basis for the design of tunable dual-wavelength polarization-controlled optical switch.
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    Object Detection of Millimeter-wave Image Based on Spatial-transformer RCNN with Deblurring
    LIANG Guang-yu, CHENG Liang-lun, HUANG Guo-heng, XU Li-min
    Acta Photonica Sinica    2020, 49 (2): 210004-0210004.   DOI: 10.3788/gzxb20204902.0210004
    Abstract388)      PDF (5115KB)(92)       Save
    An object detection algorithm of spatial-transformer regional convolutional neural network with deblurring was proposed. Firstly, based on the principle of active millimeter-wave cylindrical scanning imaging, the human body is three-dimensionally imaged (frequency range from 24 GHz to 30 GHz), and a millimeter wave image data set is established. Then the blur kernel of the millimeter-wave image is estimated. The image prior knowledge is obtained by the convolutional denoiser network and is integrated into an optimization method of half quadratic splitting to achieve non-blind deblurring. Finally, the spatial transform network, composed of a localization net, a grid generator, and a sampling network, is inserted into the feature extraction network to achieve object detection after deblurring. With the proposed non-blind deblurring algorithm, peak signal to noise ratio of the image can reach 27.49 dB. Mean average precision of object detection algorithm can reach 80.9%. The experimental results show that the image quality and detection accuracy can effectively be improved through the proposed method compared with some state-of-the-art methods. New technical support is provided for object detection of hidden dangerous goods in millimeter-wave images.
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    Deep Sea Image Enhancement Method Based on the Active Illumination
    DENG Xiang-yu, WANG Hui-gang, ZHANG Yong-qing
    Acta Photonica Sinica    2020, 49 (3): 310001-0310001.   DOI: 10.3788/gzxb20204903.0310001
    Abstract378)      PDF (6265KB)(113)       Save
    To solve the low contrast and color distortion problem of deep sea image caused by active light scattering and absorption effects in the underwater environment, an underwater image enhancement method is proposed. Different from the previous methods, which estimate the background light with the brightest pixels, background light is estimated based on the non-correlation of the object and the background light, to alleviate the disturbance of the pixels in the white objects or the illuminated foreground region, while keeping its accuracy in removing scattering, and improve the underwater image contrast. Aiming at the color distortion caused by the color gain of artificial light source color and the optical attenuation, the grey pixels, which are close to the light source, are picked in the dehazed image. Then the light intensity can be derived with the detected pixels according to the sensitivity to the source. With the estimated light intensity, the light source color is achievable. At last, color distortion can be corrected by removing the source color while compensating for the optical attenuation. Experimental results demonstrate the proposed method can effectively remove haze, recover the relatively genuine color, and further obtain the enhanced image. The information entropy and the underwater image quality evaluation values of the proposed method are higher than that of the existing methods, which indicates that the proposed method can improve the underwater image quality significantly while preserving the efficient information.
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    Fabrication of CsPbBrI2 Quantum Dots and Its Photodetector Performance
    ZHANG Xi-sheng, YAN Chun-yu, WU Ti-hui, LI Lin-feng, GUO Jun-hua, YAO Chen-zhong
    Acta Photonica Sinica    2020, 49 (1): 123002-0123002.   DOI: 10.3788/gzxb20204901.0123002
    Abstract378)      PDF (4678KB)(152)       Save
    CsPbBrI2 Quantum Dots (QDs) with good air stability were prepared by hot injection method. The photoluminescence performance of QDs was studied using 375 nm pulsed laser as excitation source. Photodetectors (PD) based on air-stable CsPbBrI2 QDs were designed and fabricated using a facial spin-coating method. The optoelectronic properties and stability of the devices were also studied in detail.The results show that the quantum dots have strong fluorescence effect near 635 nm, the spectral luminescence peak is relatively narrow, and the half-peak width is about 35 nm. The band gap of CsPbBrI2 quantum dots is 1.90 eV. As a result, the PDs are capable of broad bandwidth photodetection from deep UV 260 nm to visible 650 nm region with good photoresponsivity of 0.26 A/W, high on/off ratio up to 104 and very short rise/decay time of 3.5 ms/3.5 ms. Furthermore, the device performance shows very little degradation at 25%~35% humidity and 25℃ over the course of 60 days of storages in ambient condition. The combination of high performance broad bandwidth photodetection, remarkable stability and easy fabrication categorizes the CsPbBrI2 QDs as a kind of very promising semiconducting materials for optoelectronic applications.
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    Post Processing for Adaptive Optics Imaging Based on Multi-channel Blind Recognition
    LI Xin, WU Yang, FANG Zhou, XU Qi, YANG Hai-bo, YANG Hui-zhen
    Acta Photonica Sinica    2020, 49 (2): 201003-0201003.   DOI: 10.3788/gzxb20204902.0201003
    Abstract374)      PDF (4345KB)(252)       Save
    In order to restore turbulence-degraded imaging of astronomical or space targets in real time, this paper proposes the multi-channel blind recognition method, which can be applied to the dynamic changes of atmospheric turbulence. Target imaging at different time after adaptive optical correction are regarded as multiple channels to establish the point spread function of system. The super-Laplace algorithm is used to solve the target after obtaining estimations of point spread function. Results show that there exists a mutual relationship between point spread functions at different moments, which satisfies the theory of multi-channel blind recognition. The Mean Square Error(MSE) between the solved point spread function and the original point spread function is in the order of 10-30~10-27 and the MSE between the recovered target image and the original target is in the order of 10-5~10-4. Research results provide a theoretical basis for real-time restoration of turbulence-degraded images.
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    Design and Experiments of Annular Beam Shaping Device with Low Speckle Noise
    LIU Wen-jing, PANG Hui, CAO A-xiu, SHI Li-fang, FU Yong-qi, DENG Qi-ling
    Acta Photonica Sinica    2020, 49 (2): 222001-0222001.   DOI: 10.3788/gzxb20204902.0222001
    Abstract356)      PDF (6312KB)(119)       Save
    A design method of diffractive element that can effectively suppress speckle noise is proposed. Based on the traditional Gerchberg-Saxton algorithm, the uniformity of the light spot is effectively improved without reducing the diffraction efficiency by selecting a special initial phase. Taking the Gaussian beam shaped into an annular flat-top beam as an example, numerical simulation and optical experiments are carried out. The results show that the speckle contrasts of the annular flat-top beams obtained by using the proposed method and the traditional Gerchberg-Saxton algorithm are 11% and 34%, respectively, which verifies the proposed method can obtain a annular flat-top beam with low speckle noise.
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    Simulation and Fabrication of Polymeric Slot Waveguide for Refractive Index Sensing
    Lü Huan-lin, LIANG Yu-xin, HAN Xiu-you, WU Zhen-lin, GU Yi-ying, ZHAO Ming-shan
    Acta Photonica Sinica    2020, 49 (2): 213001-0213001.   DOI: 10.3788/gzxb20204902.0213001
    Abstract356)      PDF (4531KB)(158)       Save
    A polymer-based microring refractive index sensor based on slot waveguide was studied at very-near-infrared region (around 890 nm). The relationships between the sensitivity and the waveguide height, width and gap width were analyzed to find optimum design criteria for refractive index sensing. A silicon master mold was fabricated using electron-beam lithography. A unique class of fluorinated polymer, perfluoropolyether, was used to fabricate the flexible soft mold, which was replicated from the silicon mold successfully. The slot waveguide was fabricated on the polymer platform by using UV-based soft nanoimprint technique. The width and the height of the waveguide, and the width of the slot in the slot waveguide, are approximately 510 nm, 830 nm, and 234 nm, respectively. The thickness of the residual layer of polymeric slot waveguide is approximately 350 nm. The fabricated slot walls with a high aspect ratio are shown compatible with low cost mass production processes.
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    Passive Q-switched Cylindrical Vector Beam Fiber Laser Based on Few Mode Fiber
    WANG Cheng-xin, LU Bao-le, LUO Min, CHEN Hao-wei, BAI Jin-tao
    Acta Photonica Sinica    2020, 49 (3): 314003-0314003.   DOI: 10.3788/gzxb20204903.0314003
    Abstract355)      PDF (3778KB)(132)       Save
    A mode converter is prepared through fusion taper coupling a single mode fiber and a few mode fiber, and then a multi-walled carbon nanotube film is used as a saturable absorber to cover the cone of the converter to form a saturable absorber cylindrical vector optical device. Combined the advantages of Q-switched fiber laser and mode conversion device, the pulse cylindrical vector beam can be generated simply and efficiently, and a pulsed high-order mode laser output with high peak power and high mode purity can be obtained. The experiment successfully achieves a stable Q-switched pulse output with a center wavelength of 1 560 nm, a maximum single pulse energy and a maximum peak power of 116 nJ and 57 mW, respectively. The output of the Q-switched laser with radially and azimuthally polarized beams can be achieved by adjusting the polarization controller in the optical path.
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    Infrared Small Target Detection Based on Double-layer Local Contrast Measure
    PAN Sheng-da, ZHANG Su, ZHAO Ming, AN Bo-wen
    Acta Photonica Sinica    2020, 49 (1): 110003-0110003.   DOI: 10.3788/gzxb20204901.0110003
    Abstract349)      PDF (10160KB)(79)       Save
    Traditional infrared small target detection methods based on the human visual system can easily cause false alarm detection in complex backgrounds. Therefore, to address this issue, an accurate and robust infrared small target detection method called Double-layer Local Contrast Measure (DLCM) was proposed. First, a double-layer-diagonal gray difference contrast was proposed to enhance the visual saliency of the target and alleviate the impact on background clutter and noise. After that, an adaptive threshold segmentation was used to obtain the real target. The experimental results show that, compared with the mainstream detection methods based on human vision system, the background suppression factor of the proposed method is increased by an average of 9.3 times and the signal to clutter ratio gain is increased by an average of 7.8 times, which have better detection performance in different complex scenarios.
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    Research on Line-of-sight Channel Model of Short-range LED Optical Communication
    ZHAO Tai-fei, MA Zhuang, LI Xing-shan, LIANG Hao
    Acta Photonica Sinica    2020, 49 (1): 106001-0106001.   DOI: 10.3788/gzxb20204901.0106001
    Abstract343)      PDF (4757KB)(255)       Save
    Gauss fitting function is used to determine the Gauss-like radiation pattern of LED with small divergence angle, and the line-of-sight channel model of LED is established according to the optical radiation characteristics and radiation pattern. The relationship between the received optical power and the channel parameters of various multi-band LEDs obeying the Lambertian and Gauss-like modes is actually measured. The experimental results show that the average relative error between the measured value of received optical power and the theoretical value of channel DC gain calculation is less than ±6%,which verifies the versatility and correctness of the line-of-sight channel model proposed in this paper.
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    Avian Influenza Virus Immunosensor Based on Etched Long Period Fiber Grating Coated with Graphene Oxide
    SHI Sheng-hui, WANG Xin, LUO Bin-bin, WANG Ya-jie, LIU Zhi-jiang, NIE Qing-lin, MA Pei-jie, Lü Qing-ming, LU You-ming, WU Sheng-xi, ZHAO Ming-fu, WU Tao-jiang
    Acta Photonica Sinica    2020, 49 (1): 106002-0106002.   DOI: 10.3788/gzxb20204901.0106002
    Abstract336)      PDF (3487KB)(154)       Save
    An immunosensor based on graphene oxide modified cladding etched long-period fiber grating sensor for detection of avian influenza virus is presented in this paper. Graphene oxide is coated on the surface of long-period fiber grating by hydrogen bonding using sodium hydroxide and the avian influenza virus monoclonal antibodies are combined with graphene oxide surface by a covalent bond. The resonant wavelength change of long-period fiber grating caused by the specific binding of avian influenza virus monoclonal antibody aolsorbed on graphene oxide to avian influenza virus antigen was used for detection. The experimental results show that the limit of detection of the graphene oxide modified cladding etched long-period fiber grating immunesensor can reach 40 ng/mL, the dissociation constant ~1.6×10-7 M and the detection range 40 ng/mL~200μg/mL. The detection results of avian influenza virus in avian influenza virus blank allantoic fluid, Avian influenza virus allantoic fluid and Newcastle disease virus allantoic fluid show that the immunosensor has good specificity and clinical characteristics. Therefore, the immunosensor could be potentially applied in the fast detection and early diagnosis of avian influenza virus.
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    Parameter Compensation Algorithm of Flywheel Micro-vibration and Whole-satellite Coupling Characteristic
    HU Zi-qiang, WANG Dong, GONG Xiao-xue, TAN Lu-yang
    Acta Photonica Sinica    2020, 49 (1): 112001-0112001.   DOI: 10.3788/gzxb20204901.0112001
    Abstract333)      PDF (8168KB)(183)       Save
    In order to improve the theoretical prediction accuracy of the image motion which is affected by coupling characteristics of the flywheel and the satellite, a numerical compensation algorithm for the stiffness and damping parameters of the on-board flywheel installation is proposed. Firstly, the mathematical model of the compensation algorithm is established. Based on the radial swaying mode of the flywheel and the linear whole-wave micro-vibration transfer function model, and by combining the measured data of disturbances of flywheel on the dedicated measuring platform with jitter-affected image motion data of flywheel installed on the satellite to construct an optimization function to compensate for the installation stiffness and damping parameters of the flywheel on the satellite. Secondly, the algorithm is used to compensate and estimate the stiffness and damping of the flywheel installation in a certain type of satellite. Finally, the theoretical prediction and comparison of the jitter-affected image motion before and after the parameter compensation are carried out. The comparison results show that the estimated image motion data after parameter compensation is closer to the measured image motion data than estimated image motion data after parameter compensation and the radial rocking mode natural frequency curve is more obvious, which proves that this parameter compensation algorithm is feasible. This study significantly reduces the analysis error caused by the inconsistent installation stiffness of the flywheel on the satellite and the installation stiffness of the test platform during the whole-wave micro-vibration analysis, and provides a new idea for solving the equivalent parameters of the coupling characteristics of the flywheel and the satellite.
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    High Precision Attitude Determination Method for Star Camera Based on UKF
    WANG Yu, JIANG Wei-jiao
    Acta Photonica Sinica    2020, 49 (1): 128001-0128001.   DOI: 10.3788/gzxb20204901.0128001
    Abstract333)      PDF (6014KB)(63)       Save
    In order to enhance the accuracy and the stability of attitude data, the basic attitude determination principle of star camera and gyroscope sensor was analyzed, and the attitude determination algorithm of star camera and gyroscope based on Unscented Kalman Filter (UKF) was derived with the error quaternion as the state variables. Because of the high-precision characteristics of star camera and gyroscope sensor, the UKF attitude determination experiments were carried out with the simulative star camera and gyroscope data of various precision, and were compared with the Extended Kalman Filter (EKF) attitude determination experiments. The results show that the UKF algorithm is effective and reliable, the attitude determination accuracy of star camera is effectively improved and the tri-axis accuracy is increased by about 10% to 20%.
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