Analysis and experimental investigation for collimator reflective mirror surface deformation adjustment

Abstract

Collimator design is essential for meeting the requirements of high-precision telescopes. The collimator diameter should be larger than that of the target for alignment. Special supporting structures are required to reduce the gravitational deformation and control the surface deformation induced by the mounting force when inspecting large-aperture primary mirrors (M1). A ZERODUR ® mirror 620 mm in diameter for a collimator was analyzed using the finite element method to obtain the deformation induced by the supporting structures and adjustment mechanism. Zernike polynomials were also adopted to fit the optical surface and separate corresponding aberrations. The computed and measured wavefront aberration configurations for the collimator M1 were obtained complementally. The wavefront aberrations were adjusted using fine adjustment screws using 3D optical path differences map of the mirror surface. Through studies using different boundary conditions and inner ring support positions, it is concluded that the optical performance was excellent under a strong enough supporter. The best adjustment position was attained and applied to the actual collimator M1 to prove the correctness of the simulation results.

Method for determining the wavefront aberration of deformed optical components under external forces

“…analyzed the influence of mounting forces in different arrangements on mirrors used in interferometers. Chia-Yen Chan et al 5 . investigated and then tried to correct the distortion of the 620 mm orthogonal mirror surface.…”

“…Xu et al 4 analyzed the influence of mounting forces in different arrangements on mirrors used in interferometers. Chia-Yen Chan et al 5 investigated and then tried to correct the distortion of the 620 mm orthogonal mirror surface. However, all the above work shows only obtained results without giving specific calculation methods and no support from experimental results.…”

Introduction to the Special Issue on “Earth Observation FORMOSAT-5”

“…28, No. 2, I-II, April 2017 and low thermal expansion coefficient requirements (Kuo et al 2017), and mirror wave front aberrations and structural surface deformation enhancement (Chan et al 2017b).…”