Analysis of cryocooler Jitter on three-mirror-anastigmat camera Imaging

摘要

With the development of remote sensing satelite, the infrared and visible light parts have been integrated gradually. As the internal vibration source, the jitter of cryocooler has more and more influence on the imaging quality.At present the study of cryocooler jiiter mostly focus on the inside of the camera.We usually ignore the platform ,regard camera as a separate part, then analysis the displacement between the optical lens. But the platform and the load has the coupling relationship.The flexible platform changes the boundary of the camera.At this time,the rigid motion of the camera becomes dominant, separate research will bring bigger deviation .So two models were created which called the separated camera model and the coupled platform-camera model, then the micro-vibration transmission from the cryocooler to the optical mirrors in both cases was analysised and the relationship between coupling frequency and response size was obtained, by the way, the optical axis jitter and the deviation of the optical alignment caused by cryocooler jitter in the time domain was analysised . through optical sensitivity matrix, the change of line of sight was obtained and then the decline of MTF and the image distortion was obtained. The result shows that when the cryocooler worked, the image motion of the camera in the integration time is 0.25pixels, and the MTF is reduced by 2.5%, but the image distortion can reach 0.52pixels.