Optical testing of the primary mirror of the telescope of multispectral high-resolution imaging system

Abstract

The multispectral high-resolution imaging system is composed of four wide-spectrum cameras, which can detect targets in the visible, short-wave infrared, medium-wave infrared and long-wave infrared spectrum simultaneously. In order to reduce the size of the system, the four wide-spectrum cameras use the same telescope. To achieve operating wavelengths covering four wavebands, the telescope uses a fully reflective design with a coaxial aspherical surface with a hole in the center of the primary mirror. If aberration-free testing is used, the central aperture will occur, resulting in incomplete aperture of surface shape detection. Thus, in this paper, a compensator is designed which can achieve the whole aperture of surface testing without centralized obscuration. At the same time, the impact of the misalignment of compensator in the optical path during the test is analyzed. The optical testing path adopts infinite conjugate working distance to reduce one adjustment amount of compensator. And the first surface of compensator is coordinated with the interferometer to adjust the angle of compensator quickly and accurately, which further reduces the measurement error introduced by the optical testing path. The design of the compensator can realize the control of sensitive misalignment, reduce the surface measuring error caused by the compensator misalignments, and eventually reduce the precise processing error.