Four-mirror optical system with ultra-low distortion

Abstract

Optical systems with long effective focal length and large-aperture will play more important roles in space remote sensor in the future. Coaxis optical systems have been widely adopted due to its advantages including good symmetrical characteristics, compact structure, satisfying volume and rotary inertia. But the distortion of the coaxis three-mirror-anastigmat system is often larger than one percent of the image height and past correction is hard, which is unfavourable especially for surveying and mapping camera. Based on the design ideas and aberration theoretical analysis of Coaxis reflective optics, four-mirror systems with long focal length is presented in this paper, which can achieve high image quality and ultra-low distortion .The forth reflective mirror is set near the exit pupil to correct the aberration related to the pupil, and the processing difficulty of the primary mirror is also lowered. Example of the optical design and image quality forecasting is also given at the end of the paper.