Design of stray light suppression for large field off-axis three-reflection space camera

In order to achieve high signal-to-noise ratio for optical imaging, it is necessary to suppress stray light in space cameras. Sunlight is the main source of stray light, the smaller the solar suppression angle, the stronger the system's ability to suppress solar stray light, the more favorable it is to obtain images with better signal-to-noise ratio under strong backlight backgrounds. A off-axis three-reflection optical system was designed to meet the requirements of a large field of view and small solar suppression angle for space cameras. The camera’s field of view is rectangular, with the long side direction determining the width of the field of view. Based on the radiation characteristics of the target, a calculation method for the stray light suppression threshold is derived. Base on the optical form characteristics of off-axis three-reflection cameras, optical mechanical modeling is carried out, and optical simulation software is used to simulate stray light at real size. Through optical simulation and optimized structural design iteration, the stray light suppression scheme of the camera is finally determined. According to the requirement of minimum solar suppression angle, an asymmetric camera baffle is used to suppress stray light outside the view field, and some blocking boards are used to block stray light interference between the optical paths. In order to verify the effectiveness of stray light suppression measures, the optical path was simulated and analyzed using stray light simulation software, and the PST index met the design requirements. PST testing was conducted in the laboratory, and the test results combined with collimation data showed the the space camera meets the solar suppression angle of no more than 35 degree.