Study Of The Adaptive Optic System In Transmission Type, High-resolution Reconnaissance Camera

With an adaptive optics system, a telescope can achieve the diffraction limitation image, and the laser is able to transfer further with high energy, so the adaptive optics has drawn even more attention, and has become the standard feature in large-scale telescope.The adaptive optic system based on MEMS technology initiated in 1980s, has some unique features, such as low power consumption and little volume. And it has been used in many civil and military projects, for example, spaceborne camera/telescope, inertial confinement fusion, spatial light modulator and retinal imaging. It has promising market prospect, and what is more important is that it is also an inevitable approach to modernization of national defence. The research is on its early stage, and domestically there is few this kind of research in spaceborne environment. It is our institute that first makes the proposal for such research field and carry out the research work in China, so as to keep up with the international trends.A thorough search on the theory, structure, simulation and experiment of adaptive optics is carried out in this paper. First, the origin, state-of-the-art and development trends of adaptive optics technology is investigated and summarized.The Zernike polynomials is used in adaptive optics frequently, however there are many different definitions on it, so the dissertation addresses the definition and properties of the Zernike polynomials used in our project at the beginning. Then the method to denote wavefront in Zernike polynomials is discussed. The relationship between wavefront aberration and light quality is established as well.The moment theory, derived from digital graphic discipline, is introduced into our adaptive optic system to enhance the robustness. The Zernike moment is utilized as pre-processing filter, because it is insensitive to noise and rotationally invariant. Hence, the adaptive optic system becomes less sensitive to noise, and high assembly precision is unnecessary.The three main parts of an adaptive optic system, including wavefront sensor, wavefront corrector and wavefront reconstruction algorithm, are introduced. For each part, the traditional and state-of-the-art implementations and theories are discussed and compared in the thesis. Especially, the modal wavefront reconstruction algorithm used Zernike polynomials and the principle on determining the order of Zernike polynomials are presented in detail. The simulation on Hartmann-Shack wavefront sensor and wavefront reconstruction proves the validity of the algorithm and code. Testing is done on the MEMS-DMs used in project, which has 37 poles in the diameter of 25mm. Further the influence function matrix is deduced, from which we can tell the relationship between voltages on poles and the shape of the MEMS-DMs.Finally, an adaptive optic experimental layout is established. The ability to compensate the wavefront aberration, and to improve the image quality is studied in open loop and closed-loop environment. The results indicate that the parameters of this equipment are feasible, and the system closed-loop control algorithm achieves the goal of our project. This layout can compensate the wavefront aberration to the pre-set planar wavefront, improve the image quality and increase the Strehl ratio.