Research On The Technology Of Testing Large Convex Aspherical Mirror By Single Wedge Compensation Stitching Method

With the development of astronomical optics and space,the requirements for the resolution and energy collection of the optical system are getting higher and higher,and the aperture of the optical system is getting larger and larger.However,the high-precision test technology of large-aperture optical aspheric surfaces,especially the high-precision test of large convex aspheric optical elements,has always been a problem in the field of optical measurement.Traditional test methods of large convex aspheric mirrors need to make a compensator with a larger diameter than the component under test,such as Hindle-Sphere test method,Null Lens test method,CGH(computer generation hologram)test method,etc.However,the large-diameter compensator is difficult to manufacture,the production cost is high,and the production cycle is long,which restricts the manufacturing precision and efficiency of the large-diameter convex aspheric mirror.The sub-aperture stitching method is an effective measure method for testing large-aperture optical elements.However,in order to testing large convex aspheric mirrors,it is often necessary to plan a large number of sub-apertures.This reduces the transmission and accumulation of errors,and reduces the accuracy and reliability of sub-aperture stitching measure.Surface shape test method based on single optical wedge compensation stitching measure large convex aspheric mirror,combining single optical wedge compensator and sub-aperture stitching measurement,which effectively solves the shortcomings of traditional test methods and improves interferometer test dynamic range,reduces the number of sub-apertures and the transmission and accumulation of errors,improves the accuracy of stitching measurement.This paper conducts a theoretical study on the large convex aspheric surface stitching method based on single optical wedge compensation.At the same time,the method is verified experimentally based on engineering examples.The research content of the thesis mainly includes the following four parts:1.Establishment of optical wedge aberration modelThis article first analyzes the aberration principle of a single optical wedge,and theoretically verifies the feasibility of a single optical wedge as a compensator.Based on the Seidel aberration of the inclined parallel plate,the optical wedge aberration model is analyzed,and the wedge aberration numerical calculation model is established by the method of ray tracing and aberration superposition.Compared with the wedge aberration model obtained by simulation,the theoretical model of wedge aberration under the commonly used F~#is obtained.This model has practical engineering significance.At the same time,the theoretical compensation measure range of the single optical wedge is analyzed.According to the difference of the F~#and the center thickness of the optical wedge,the compensation range of the optical wedge can be better than 1000?RMS(?=632.8 nm).2.Simulation experiment and analysis of single optical wedge compensation testThe sub-aperture planning principle after adding the single optical compensator is analyzed,and the sub-aperture planning standard is given.A detailed analysis of the role of the single wedge compensator in test optical path and the principle of compensation test.Combined with engineering examples,a single optical wedge compensation simulation experiment was designed for a large convex aspheric surface with a diameter of 360 mm,and compared with the subaperture stitching measure scheme without a compensator,it was verified that the single optical wedge compensator can expand the dynamics range of the interferometer,reduces the number of sub-apertures and improves the test accuracy of large convex aspheric surfaces.The sensitivity analysis of test optical path shows that the single optical wedge compensation test system has good robustness.The test accuracy of single subaperture can reach 6.76 nm RMS.Simultaneously,a multi-turn single wedge compensation simulation experiment was designed for a large-diameter square convex aspheric surface with a diameter of 425 mm,which showed that the single wedge compensation test has flexibility,applicability and robustness.3.CGH calibration optical wedge compensatorVarious errors in the test results of single optical wedge compensation are coupled with each other,and decoupling is difficult,and due to the limitation of the space of the measure equipment,it is difficult to use traditional methods to calibrate the system errors of the standard mirror and the single optical wedge compensator.Aiming at this problem,a method for calibrating the pose of the wedge compensator and testing the system error of the optical path using computer generation hologram(CGH)is proposed.The production principle of CGH is introduced,and the design scheme of CGH used to calibrate the single optical wedge compensator is given.Design CGH calibration simulation experiment for single optical wedge compensator used to test425mm aperture.Analyzing the CGH error,it is found that the CGH calibration accuracy is better than 1.98 nm RMS.Analyze the test accuracy of the full-aperture surface shape under the CGH calibration,the full-aperture surface accuracy of single optical wedge compensation stitching measure can reach 3.43 nm RMS.The result shows that the CGH calibration single optical wedge compensation test optical path system error is feasible and applicable,and the single optical wedge compensation test method has good applicability.4.Single optical wedge compensation test experimentBuilding a single optical wedge compensation test optical path,and a single optical wedge compensation stitching measure experiment was performed on a 425mm large convex aspheric mirror.Use the designed CGH to calibrate the system error of the single optical wedge test optical path.The system error points of the second and third circles of the optical wedge test optical path are obtained as 0.023?RMS and0.011?RMS.The calibrated single wedge compensation test optical path is used to test of large convex aspheric mirrors.Analyze and process the data,decouple the error,and get the full-aperture stitching measure result 0.077?RMS,0.668?PV,compared with the full-aperture surface shape test results,the residual errors are 0.023?RMS and 0.391?PV.The feasibility of the single optical wedge compensation test method is verified through experiments.This paper has carried out research work on the test method of single wedge compensation and stitching large convex aspheric mirror.Completed the modeling of the wedge aberration theoretical model.Aiming at the optical wedge,a non-null compensator,a method for calibrating the optical wedge compensator by CGH is proposed,which improves the accuracy and reliability of single optical wedge compensation test.Finally,it is verified through experiments that the single wedge compensation test large convex aspheric mirror has good applicability,flexibility,and robustness,which provides an effective method for the high-precision surface test of large convex aspheric surfaces.