Research on optical alignment technology for Cassegrain system

The centering alignment scheme for the aspherical primary mirror of Cassegrain system in the use of three-coordinate measuring machine was presented, which could achieve rapid centering and meet the accuracy requirement in the process of computer-aided alignment. In order to reduce the mirror deformation because of adhesive stress and thermal stress to a minimal range, the microstress adhesive manner was used to position the mirrors, especially for the primary mirror of 300mm aperture. The wavefront information of the Cassegrain system proposed in this paper was obtained with Zygo interferometer. With the primary aberration converted by the wavefront aberration measured above, the computer-aided alignment of the Cassegrain system could be completed according to the corresponding relationship between the misalignment and aberration of optical system. After alignment，the system root-mean-square(RMS) value reached 0.1，the solution was less than 1.The testing results show that the imaging quality of the system is close to the theoretical diffraction value，the centering alignment can achieve rapid centering and meet the accuracy requirement in the process of computeraided alignment.