Design of aspherical metal mirrors used in infrared thermal imaging systems

Abstract

An important factor influencing the image quality of space or military optical systems is that the broad environmental temperature ranges. It would bring some problems on design, fabrication and mounting of the optical system. The ways of getting rid of the problems and improving the image quality of optical systems by using aspherical metal mirrors to the infrared thermal imaging system are presented in this paper. The choice of mirrors materials, the design of mirrors structure, the analysis of factors of influencing mirrors surface figure are discussed. The actual optical system designed in this paper is a Cassegrain objective, and the reflective surfaces of the primary mirror and secondary mirror are conicoid surfaces. The diameter of the primary mirror is φ240mm, the materials of mirrors is aluminum alloys, and the mounting structure is flexible. The aspherical surface of the metal mirror are fabricated by precision diamond turning machine, and the error of the surface figure is less than 0.5μm. The results of the battlefield test show that the infrared system with metal mirrors discussed in this paper has met the optical design specifications.