| 其他摘要 | In satellite laser ranging, adjusting the divergence angle of laser beam is helpful to improve the ranging ability of the ranging system when ranging targets with different orbital heights. At present, the fixed magnification Galileo beam expander is usually used in ranging system. The divergence angle is adjusted by changing the distance between two lenses, which will produce defocusing aberration. From the qualitative point of view, the defocusing aberration will affect the laser beam quality and the ranging ability of the system. In order to reveal and solve this problem, this paper first studies the influence of defocusing aberration on the ranging ability of ranging system, quantitatively describes the relationship between the two through theoretical analysis, and grasps its law. Secondly, a divergence angle adjustment device is proposed and designed to solve the defocusing aberration problem in the process of divergence angle adjustment.Firstly, the propagation algorithm of Gaussian beam in free space, the transformation of laser beam by optical system and wave aberration theory are the important theoretical basis for studying the spatial distribution of laser beam energy density, these contents are summarized in this article.Secondly, the transformation effect of laser beam expanding system on Gaussian beam is analyzed, and the relationship between angular magnification and defocus is obtained. Using the propagation theory of Gaussian beam, the influence of defocusing aberration on the spatial distribution of beam energy density is obtained. For different distance satellites, the number of echo photons received by laser ranging system under two kinds of beam expanding systems is calculated. The simulation results show that: the angular magnification and defocusing amount obey approximately linear relationship, the defocusing amount changes 1mm, the divergence angle changes 1µrad; the defocusing aberration affects the energy density distribution of the beam, so that the light spot is diffused; for satellites with different distances, the number of echo photons received by the focusing beam expander system at different angular magnification is the same as that of the defocusing beam expander system 2 times, which can effectively improve the success probability of target detection.Finally, a method of switching the concave lens of Galileo telescope to adjust the beam divergence angle is proposed, which is called focusing beam expanding system. In the focusing beam expander system, the divergence angle is adjusted by switching concave lens, and three kinds of beam expansion rates are designed, which are 2 times, 2.5 times and 3.3 times. In order to meet the requirements of lens processing, a template was set for the focusing beam expander system, and the tolerance of the focusing beam expander system after the template was set was analyzed, and the tolerance distribution range was determined: surface radius tolerance ±0.2mm, surface thickness tolerance ±0.2mm, eccentricity tolerance ±0.2mm, surface inclination tolerance ±0.2mm, component inclination tolerance ±0.5°. The optical part drawing is designed and the lens is processed. The electric displacement table meeting the requirements is determined through product research. |
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