Research On Wide Field Corrector Lens Support Design And Evaluation Method For Large Survey Telescope

In order to explore the origin and evolution of the universe,the large wide-field survey telescope will break through the existing detection depth and observation area,conduct wide-fast-deep exploration of the sky,obtain more high-quality astronomical samples,and help humans solve more scientific frontiers Unresolved issues.The meter-level corrector lens of large aperture wide-field survey telescope is different from ordinary transmission optical systems.The size and weight of the lens are large,and the working conditions are complicated.Therefore,to ensure the imaging quality of the lens under the change of gravity,the paper establishes an evaluation method for 850 mm fused silica lens,designs the supporting structure,and studies related techniques for alignment.We comprehensively considered the quality of the transmitted wavefront of the lens,the influence of gravity,and the need for subsequent detection of wavefront alignment and adjustment.We used theoretical calculations and finite element simulation design optimization methods to study the following points:(1)We propose a variable-frequency imaging quality evaluation method for the transmission wavefront in the full frequency domain,combine the structure function,roughness scattering theory and standardized point source sensitivity theory(PSSn),establish a PSSn-based low,middle and high frequency wavefront error evaluation system and simulated and verified by experiments.The analysis and experimental results show that compared with the traditional evaluation method,the full-frequency domain variable-scale evaluation method has high reliability and strong characterization ability,and more comprehensively evaluates the performance index of the optical transmission system from the frequency domain perspective.(2)In order to make the performance of the corrector lens meet the design requirements,we summarize and analyze the basic principles and general methods of lens support design,optimize the number of support points,the position of the support surface and the radial,axial support force,establish finite element models of elastomers and flexible structures,optimize and analyze the key parts of the support structure,and focus on the displacement and deformation,stress changes and imaging quality requirements of the lens and the mirror chamber under different gravity loads.The results show that within the range of 0 ° ~ 90 ° elevation angle,the PSSn value of the lens supported by the elastomer is at least 0.9826.In the flexible support structure,the transmitting wavefront quality PSSn is 0.9366;(3)Based on the previous,we establish a wavefront alignment detection technology that combines differential optical transfer function(dOTF),machine learning,and computer-aided tuning.The neural network model is trained by the wavefront information calculated by dOTF to guide optics.The amount of component misalignment,while analyzing the phase solution,the CCD detection noise and atmospheric disturbances affect the error caused by the detection calculation.The results show that the detection error is small and meets the requirements of alignment and adjustment.The methods of evaluating the imaging quality of large-aperture lenses,support technology,and installation errors have greatly improved the quality of transmitted wavefronts supported by the lens under working conditions and achieved the establishment of the imaging quality of the correction lens group.The support structure design finally reached the preliminary exploration of the alignment and adjustment technology.For the research on the related technology of large-aperture meter lenses,the paper has extensive reference significance and reference value.