Aiming to address the low efficiency of the traditional calibration method for star sensors, we propose a calibration method using two-dimensional (2-D) Dammann grating, which can generate a dot array with uniform intensity and a certain interval. This method is based on theoretical analysis of the diffraction angles of 2-D Dammann grating relative to the tilt angles of incident light. We calculate the angles using a fitting method and further calculate the geometric parameters, such as principal point and principal distance of the star sensor. Finally, we establish a calibration system using 2-D Dammann grating and a nanostar sensor with a 25-mm focal length and 15-deg full field of view has been calibrated. The results show that the calibration accuracy for single-star measurement is better than 6 arc sec, which satisfies the requirement for high-efficiency star sensor calibration and validates the proposed method.
According to the sequence of license plate image has low resolution, in order to improve the image resolution, this paper proposes a multiframe super-resolution image reconstruction algorithm based on overcome registration error and Gauss weight interpolation. First, multiframe image sub-pixel image registration, through extracting the SIFT keypoints of the image, rough matching with BBF algorithm, accurate matching with RANSAC algorithm, establishing the homography matrix between matching points. In order to overcome the registration error, this paper proposes a method based on threshold to overcome the registration error. Finally, the multiframe low resolution image is projected into the high resolution image grid by image registration. The value of the high resolution grid is reconstructed with a non-uniform interpolation algorithm based on Gauss weight. The experiments show that both on the subjective evaluation and objective evaluation can obtain satisfactory reconstruction results, and the registration error is robust.
For the improvement of space photovoltaic cell efficiency, an astromesh deployable concentrator for space concentrating
photovoltaic (CPV) system is proposed. A deployable solar parabolic concentrator with an aperture radius of 3 m and a
concentration power of 35 kW has been designed. The astromesh deployable concentrator has a high degree of solar
concentration, lightweight, and easy deployment, which has an advantage over inflatable deployable concentrator and
rigid concentrator. We analyse the performance of the CPV system simulated by software Lighttools, and the results
indicate the CPV system can generate 270W electrical energy per kilogram, so the utilization of solar energy have been
enhanced effectively. This system can be used for the support of various spacecrafts power and space solar power
Electrostatic membrane mirror is ultra-lightweight and easy to acquire a large diameter comparing with traditional
optical elements, so its development and usage is the trend of future large mirrors. In order to research the control
method of the static stretching membrane mirror, the surface configuration must be tested. However, membrane mirror's
shape is always changed by variable voltages on the electrodes, and the optical properties of membrane materials using
in our experiment are poor, so it is difficult to test membrane mirror by interferometer and null compensator method. To
solve this problem, an automatic optical test procedure for membrane mirror is designed based on Hartmann screen
method. The optical path includes point light source, CCD camera, splitter and diffuse transmittance screen. The spots'
positions on the diffuse transmittance screen are pictured by CCD camera connected with computer, and image
segmentation and centroid solving is auto processed. The CCD camera's lens distortion is measured, and fixing
coefficients are given to eliminate the spots' positions recording error caused by lens distortion. To process the low
sampling Hartmann test results, Zernike polynomial fitting method is applied to smooth the wave front. So low
frequency error of the membrane mirror can be measured then. Errors affecting the test accuracy are also analyzed in this
paper. The method proposed in this paper provides a reference for surface shape detection in membrane mirror research.
With the development of optical information processing, high-resolution Fourier transform lens has often been used in holographic data storage system, spatial filtering and observation of particles. This paper studies the optical design method of high-resolution Fourier transform optical lenses system, which could be used in particles observation and holographic data storage system. According to Fourier transform relation between object and its frequency plane and the theory of geometrical optics, the system with working wavelength 532nm and resolution 3μm was designed based on ZEMAX. A multi-configuration method was adopted to optimize the system's lenses. In the optical system, a diaphragm was placed at the system's spectrum plane and the system demanded a low vacuum to cut down the influences of atmosphere and other particles. The result of finite element analysis indicated that the influences of vacuum pumping to optics spacing and mirror surface shape very minor, and the imaging quality not being affected. This system has many advantages, such as simple structure, good image quality and a high resolution of 3μm. So it has a wide application prospect and can be used both in holographic data storage system and particles observation.
TMA (Three Mirror Anastigmatic) is popular to the design of space-based optical system. This paper describes the characteristics of the on-axis TMA optical system. An on-axis TMA system with 13m focal length is designed and analyzed. To solve the initial configuration parameters, Cassagrain structure is confirmed firstly, and then the tertiary mirror. Based on initial configuration parameters, automatic optimization is executed in ZEMAX program, and design result with excellent image quality is acquired, which shows the procedure we choosed with good advantage of computer processing. As the distortion of the design reaches 1%, its influences on TDICCD brushing camera are discussed. The source of distortion is analyzed and correcting methods are considered. Zero focal power corrector is chosen to correct the distortion, and the corrected distortion is less than 0.02%. The research on on-axis TMA system in this paper makes a foundation for farther high-resolution remote sensing applications.