The design of 3-mirror off-axis optical system with stray light analysis based on vector aberration theory

Abstract

The stray light analysis is always carried out after the optical system design is completed. However, for the off-axis system with 3 mirrors, if the space between the mirrors is not enough to place baffles, the optical system must be redesigned. To avoid this, a new design method for 3-mirror off-axis optical system with the consideration of stray light analysis based on vector aberration theory is presented. At the initial stage of the optical design, the correction of varied aberrations, such as spherical aberration, coma, astigmatism, etc., and the reservation of enough space for different baffles by decentering and tilting mirrors are carried out at the same time. Considering that in order to get enough reserved space, the decenters and tilts of some mirrors may be not a small amount, and the third-order aberration theory must have large deviations in guiding the design of off-axis optical system with 3 mirrors. For the convenience and efficiency of aberration correction, the vector aberration theory is also applied to the design to make sure the decenters and the tilts of mirrors will introduce minimum interference to image quality. Based on the vector aberration theory, we can obtain the initial results by solving the aberration equations with proper constrains. The initial structure can be served as the starting point for optimization design. At the end of the paper, a design example is illustrated and its stray light analysis is also finished in the software Fred, which a professional stray light analysis software. And the design and analysis results show that the optical system has a very high imaging quality and a good ability of suppression of stray light.