Feasibility study of corrector lens as window for LAMOST vacuum camera

To improve optical performance of vacuum camera as the goal, feasibility of existing corrector lens as a vacuum camera window is studied. Through existing geometric model of corrector lens, mechanics field is mapped into the finite element model, and deformation of corrector lens under atmospheric pressure difference is calculated. The least squares method is used to solve 6-order coefficients of Zernike polynomial and the fitting solution are used to solve corrector lens shape equation. Effect of modified corrector lens on vacuum camera image quality is analyzed. Results show that deformation radius of the latent image of vacuum camera is 41.9% higher than that of original image, but CCD focal length changes from 249.554 mm to 249.574mm, so that CCD diffuse radius of bitmap is between 0.301% and 1.09% of the original, and the original image quality of LAMOST low-resolution spectrometer camera is maintained. Therefore, existing corrector lens can be used directly in vacuum camera design.