Design of a visible and infrared common optical system with the same effective focal length

In this paper, the results of designing a visible and infrared optical system with the same effective focal length are presented. The basic form is the three-mirror anastigmat (TMA) structure that can minimize major aberrations such as spherical, comma, and astigmatism and is an optical system that can secure a relatively wide field of view. The ray incident onto the optical system passes through three mirrors, is divided into infrared and visible bands by a beam splitter, and is incident on the focal plane array (FPA). Typically, in the case of a visible optics system, the stop of the optical system is placed near the primary mirror to be designed to have a minimum size. However, the stop is placed in front of the FPA to minimize thermal stray light owing to the internal temperature in the infrared channel.