Research On Testing Large Convex Aspheric Surfaces By Sub-Aperture Stiching And CGH Mixed Compensation Technology

With the rapid development of astronomical optics and applied optics,in order to make the resolution of the optical system higher,the aperture of the optical system is becoming larger and larger,and higher requirements are also put forward for optical processing and manufacturing technology and optical testing technology.Traditional convex aspheric testing methods include contour measurement,aberration measurement,compensation measurement,and sub-aperture splicing testing.The profile testing method has a limited testing aperture,long testing time,and limited testing accuracy;The aberration no-aberration method is only suitable for the testing of special quadrics,and a larger aperture Hindle spheric mirror is often required when testing large-aperture aspheric surfaces,and there will be a central occlusion problem during the measurement process;When we only use compensation elements for fullaperture surface shape testing,it requires the production of a large-aperture aspheric compensation lens or CGH.As for aspheric compensation lens,their aperture needs to be larger than the mirrors to be measured and a matching aspheric compensation lens is also needed.A large steepness deviation requires a CGH with high characterization density.Whether it is compensation lens or CGH,it has difficult production,high expense and complicated assembly and testing;The sub-aperture splicing method is simple and convenient and has high accuracy when detecting small and mediumaperture convex aspheric surfaces,but for the testing of large aperture convex aspheric surfaces,the use of splicing testing will make the number of sub-apertures numerous,increase the difficulty of data processing and testing time,and more importantly,aggravate the transmission of errors which limit the accuracy of splicing testing.Based on the above traditional methods,this paper proposes a method of testing large-aperture convex aspheric mirrors combined with CGH compensation testing method and sub-aperture splicing testing method.This method improves the testing accuracy of large-aperture convex aspheric surface and effectively solves the shortcomings of traditional testing methods.The content of the paper is mainly divided into the following three parts:1.Principle analysis of hybrid compensation testing methodsThe existing convex aspheric testing methods are introduced.The advantages and disadvantages of each method are summarized.The testing method of large-aperture convex aspheric surface testing based on CGH-based splicing compensation method is proposed The principle of this testing method is theoretically analyzed.The design principle and production process of CGH.The sub-aperture splicing algorithm and model and aspheric distortion correction model are introduced,and the production error of CGH is analyzed.All of them provide a theoretical basis for subsequent splicing experiments.2.CGH hybrid compensation testing simulation analysisCombined with engineering examples,a simulation experiment has been designed for a large aperture convex aspherical surface with a diameter of 540 mm.According to the principle of sub-aperture planning,the central sub-aperture and the outer subaperture have been divided.According to their different magnitude aspheric degrees,the appropriate testing methods have been determined,and the feasibility of the testing methods has been verified by simulation experiments.3.CGH hybrid compensation testing of large-diameter convex aspheric surface experiment and error analysisThe testing experiment of 540 mm large-diameter convex aspherical mirror has been carried out.The central sub-aperture and the outer sub-aperture have been tested separately.The testing results have been stitched using the globally optimized subaperture stitching algorithm to obtain full-diameter surface shape information.The test results of full-aperture splicing : PV =1.342λ,rms = 0.075λ.The systematic error and random error in the experimental process have been analyzed.The feasibility and applicability of the CGH compensation testing method and the sub-aperture splicing testing method for detecting large-aperture convex aspherical mirror have been verified.In this paper,the testing method for detecting large-aperture convex aspheric surfaces based on CGH splicing compensation method has been discussed and studied,and the design simulation and experimental verification of the experiment have been completed.The final testing accuracy reaches λ/50,and it shows that the method can achieve high-precision testing of large-aperture convex aspheric surfaces.