Research On Optical Co-phasing Detection Technology Of Segmented Telescope

Astronomical telescope is an essential tool for astronomical observation.With the development of science and technology,the astronomy community has put forward higher requirements for the resolution ability of astronomical telescope.According to Rayleigh criterion,higher the aperture of the telescope contributes to higher the spatial resolution of the system.However,due to the limitations of manufacturing,processing,testing,it is the limit for a single primary mirror to reach 8m.The design of the segmented primary mirror makes the idea of an extremely large aperture telescope a reality,but including the primary mirror configuration design,especially the co-phasing error caused by the stitching misalignment have become a problem that must be solved.In order to make the resolution of the segmented telescope close to its equivalent aperture,each sub-mirror needs to achieve the co-phase.The research work on the optical co-phasing detection technology of the segmented telescope are summarized as follows:Firstly,the primary mirror configuration and optical design of ground-based and space-based segmented telescopes were investigated.The mechanism of JWST wavefront detection and control was studied.The definition of co-phasing error was defined,and the flow of co-phasing detection was planned.The advantages and disadvantages of various optical co-phasing detection techniques and their application fields were summarized and analyzed.Secondly,the segmented primary mirror model of concentric circular structure was designed.And the pupil models of segmented primary mirror were established based on homogeneous coordinate transformation.According to the scalar diffraction theory,the imaging principle of segmented optical system was studied,and the influence of segmented mirror configuration,piston error,tilt error on the diffraction effect was simulated and analyzed.Then,the basic principle of the phase diversity method was studied,the detection flow of this method was summarized,and the performance of different nonlinear optimization algorithms was compared and analyzed.To solve the problem that the traditional phase diversity method requires extra optical elements to introduce phase diversity,an improved co-phasing detection technology based on the sub-aperture phase diversity method was proposed,and its feasibility was verified by numerical simulation.Finally,base on the study of the wavefront detection principle of Fizeau interferometer,an experimental platform for the segmented primary mirror Cassegrain system was built.And the detection experiment was completed.The final result of the system's wavefront detection is 58.811 nm RMS,which meet the requirements of the design index and verify the feasibility of the co-phasing detection technology based on Fizeau interferometer.