The space camera is one of the most advanced optical equipments in obtaining earth surface information from space. With the development of the optical design, manufacture and alignment technology, the performance of the optical camera is moving forward quickly. In spaceto- ground remote sensing field, the resolution of ground remote sensing images have become higher and higher. Off-axis three-mirror system becomes an advanced optical system structure of space camera at present , because of its merits of large field, long focal length, no obstruction, high modulated transfer function, wide spectrum, good image quality, small cubage and light weight, etc. As it is difficult to align and test, the alignment of off-axis three mirror system is timeconsuming, so it is important and necessary of studying the computer-aided alignment of the complex optical system. Aiming at cutting the time of alignment, Computer-aided alignment technology is applied to this system. According to relation between fringe Zernike coefficient and Seidel aberration, wavefront aberration in the exit pupil of optical system is instead with fringe Zernike coefficient. A series of Zernike coefficient expressing the incorrect parameters of system are obtained by using multi-fields ZYGO interferometer auto-collimating interference test, which are transformed into geometric aberrations as the corrected object. Incorrect parameters of the system are determined by sensitivity matrix resulted from optical design software. These incorrect parameters are defined to be variables; the Zernike coefficient are defined to be the optimized target in merit function. The system is optimized by applying optical design software to receive the incorrect parameters result. Consequently, the adjusted result is brought into the optical design software to verify the right selection of incorrect parameters. The practical experiments are also given, result with RMS value lower than 0.04λ is acquired by using this alignment technology which has proved the effectiveness of above methodology of guiding-alignment.
There is a vast range of prospects on remote sensing, land mapping, resources survey, natural disaster monitoring by using multispectral camera. It is useful for improving national economic development and realizing numerical earth. Optical tolerance is a critical step in the optical design process. Sensitivity analysis and inverse sensitivity analysis are used to compute the effect, which reduce the optical system performance by the each tolerance parameter. Suitable tolerating requirements and compensators may be defined to model allowable adjustments after fabrication. The optical system with high image quality and low distortion is produced according to the tolerance requirements. The tested result shows the MTF of multi-spectral can reach to 0.243 at Nyquist frequency; the tolerance analysis methods are correct and feasible.
Based on spread spectrum signals detecting technology, a kind ofsoftware capture method ofspread spectrum signals is presented. in this paper. A kind of 2-D signal capturing method is advanced which combines parallel pseudorandom-code (PN-code) phase and capturing of carrier frequency, as a result, the capturing time is shortened greatly. The method is used in this system by which the energy is accumulated to improve the signal-to-noise ratio (SNR) ofinput-signals, consequently improve the detection performance. The working principle and overall structure of the capturing system is introduced. The capturing structure model and mathematical one, the acquisition algorithm and realization, the design of parameters are discussed in detail. The possibility of the system has been verified by experiments and performance analysis.