High-precision Optical Lens Assembly And Calibration Methods - Optical Lens Gravitational Deformation Analysis

The assembling and calibration methods for optical lens are systematically introduced in the paper. Generally, the gravity introduced deformation of an optical lens with smaller aperture (<(100mm) within visible band is about (/20 even less than this value. For general optical lens, this error level can be entirely neglected. But for the high-accuracy optical system within extreme ultraviolet band, the error caused by gravity deformation will lead to imaging quality degradation. For this reason, the gravity deformation appeared in assembling and calibration of high-accuracy optical lens in large-aperture optical system is emphatically analyzed in detail. The gravity analysis is carried out especially for the synthetic fused silica and calcium fluoride used in 193nm lithographic objective as well as the optical elements with structural sizes of (200mm⁽300mm. Large numbers of analysis data for surface shape error are obtained by using Algor finite element analysis software. Then these data are plotted into curves and comparison analysis will be carried out, finally the measures and schemes for reducing gravity deformation are proposed. The experiments for the above measures and schemes are carried out. The experimental results demonstrate that the analysis results are correct and the methods for reducing gravity deformation are effective.