Deformation analysis of a lightweight metal mirror

Abstract

The weight of the optical elements of a system used in the aviation and aerospace industry must be as light as possible, on condition that the imaging performance of the system satisfies user’s demand. However, optical elements will deform easily under internal or external pressure if it becomes thinner, and then influences the imaging performance of the whole optical system. In this paper, the main mirror of the Cassegrain system is studied with finite-element analysis (FEA) to predict its surface deformation through simulating its working conditions. The surface deformation is also tested and analyzed after machining and mounting. The obtained interferometric data, Zernike coefficients, is written into CODE V, an excellent software for designing optical systems, to analyze the imaging performance of the designed optical system. Through analyzing the deformation of the metal mirror it can be found that the maxima RMS change of the whole optical system is 0.0059λ, which is only 1.52 percent of the designed value. In the full field of view, the RMS error is less than 0.07λ, that means the imaging performance of the whole optical system is close to the diffraction limit.