Research On Common-phase Detection Technology Of Spliced Mirrors Based On Dual-wavelength Phase-shifting Interferometer

The larger the aperture of the primary mirror of the telescope,the higher the resolution and the stronger the light-collecting ability.Compared with the single mirror,segmented mirror are easier to form a large aperture or super large aperture telescope.Therefore,sub-mirror stitching has become an important trend in the development of telescope technology.Co-phase of segmented mirror is the key to achieve the expected resolution of the telescope,and its core is the detection and adjustment of the piston error of the sub-mirrors from the coarse co-phase to the fine co-phase.However,in the process of the co-phasing adjustment of segmented mirror,the dynamic range of the piston error is relatively large,and a combination of multiple detection methods is required.In order to reduce the complexity of segmented mirror co-phasing detection,this thesis proposes a technical solution by using dual-wavelength phase-shifting interferometer to realize segmented mirror co-phasing detection,aiming to give full play to the advantages of interferometric measurement high precision and dual-wavelength interference high dynamic detection range.The dual-wavelength phase-shifting interferometer guides the detection and adjustment of the co-phase error of the sub-mirror from the coarse co-phase to the fine co-phase.First,based on the basic theory of co-phasing detection,this thesis analyzes the influence of the co-phase error of the spherical segmented mirror on the overall wavefront and establish the segmented mirror imaging optical model for calculating the error tolerance of the piston error and tip/tilt error that have the most impact Secondly,the theoretical research and simulation analysis of the defocus of the combined sub-mirror are carried out and the monochromatic laser detection in the dual-wavelength interferometer is used to obtain the nearzero fringe interferogram when the sub-mirror is defocused.Combined with the method of white light micro-interferometer for coarse common phase detection of segmented mirror,these two methods can adjust the step height at the gap of segmented mirror to within a quarter equivalent wavelength range that can be detected by dual-wavelength interference.Finally,dual-wavelength phase shifting interference surface shape detection principle is adopted to perform fine co-phasing detection on the piston error and tip/tilt error between the sub-mirrors,which broadens the detection range while retaining the measurement accuracy of singlewavelength interference detection.Basing on the operating wavelengths of 632.8 nm red light and 532 nm green light Fizeau dual-wavelength phase-shifting interferometer and two hexagonal spherical sub-mirrors with side length of 17.5 mm cut out from a round len with a diameter of 76.2 mm as the testing objects,this thesis verifies the technical scheme of using dual-wavelength phase-shifting interferometer to realize segmented mirror common phase detection experimentally.The piston error between sub-mirrors can be compensated to 16.0 nm with the help of segmented mirror co-phasing calibration system designed and constructed by the author.