The Measurement Of Large Convex Ashpheric Mirrors With Subaperture Stitching Method

Large mirrors are the indispensable part of the large modern optics systems. With theconstant development of optical fabrication and measurement technique, the large-apertureoptical systems with large aspheric mirror are widely used in astronomy, space opticsapplications. The measurement of large aspheric mirror with high precision comes to be achallenge in the advanced optical manufacture field. Testing convex aspheric mirrors are moredifficult. The important study of this thesis is to measure the convex aspheric mirrors with nullaberration testing and subaperture stitching methods. The large convex aspheric mirror ismeasured by subaperture stitching method with a small auxiliary mirror at low cost. The resultsthat obtained this method are compared with other method testing results to ensure the precision.This thesis is dedicated to solve the key theoretical and technical problems for convex asphericmirror measurement with null aberration testing and subaperture stitching methods, and developa method to testing large aperture convex aspheric mirrors. The major research efforts aresummarized in the following points.1. The domestic and overseas development status about the convex aspheric measurement isinvestigated, the testing methods are classified. At the same time the subaperture stitchingmethod is also investigated. The theory of the convex aspheric mirror testing based on nullaberration testing and subaperture stitching method is discussed. Because the large telescope’ssecondary mirror are always hyperbolic mirror, the scheme of experimental system and workingprocess for hyperbolic mirrors are extendedly discussed. The testing implementation proposedand key issues involved and the difficulty technical issues are analyzed.2. The subaperture stitching algorithm is the final implement means of this testing method.The two representative methods, Zernike Polynomial and Discrete Phase Method, are studied.The Zernike Polynomial method’s basic problem is studied with statistics and error treatmenttheory. The sparse subaperture methods are introduced to the mirror polishing. The matrixstitching technology is developed with the Discrete Phase Method. The comparative stitchingprecision is proposed grounded on the stitching method itself. Numerical simulations andsensitivity analysis for the proposed two algorithms are provided3. The relationship between the subaperture lattice and auxiliary mirror parameter arediscussed through the geometrical optics and subaperture stitching precision. The subaperturelattice is established and the equation for optimization of auxiliary mirror parameter is deducted.4. A150-mm convex hyperbolic mirror was tested by sparse subaperture method, oneannular subaperture method, and two annular subaperture methods, respectively. The sparsesubaperture method testing results are compared with the traditional optical compensationmethod; it is shown that results are in good agreement with the fraction of coverage increasing.The one annular subaperture and two annular subaperture method results are compared with thetraditional optical compensation method and the QED testing method; the testing results are ingood agreement.5. The source of the main errors in experiment is analyzed and classified. The wavefrontaberration error, image distortion error, overlapped area point to point correspondence error andthe theory testing error are mainly discussed. And the calibration method for these errors is proposed.6. Based on the relationship between the convex hyperbolic mirror parameter and front andback focal length, the convex hyperbolic mirror parameter calculated by the space pointscoordinate value which was obtained by the laser tracker. A150-mm convex hyperbolic mirrorparameters were tested by this method. The results show that this testing method is at highprecision and stabilization.7. The absolute subaperture testing is proposed with odd and even theory and ZernikePolynomial method. The aperture of278mm and80mm convex sphere are tested by this method.The results are compared with the QED testing method and two sphere methods. It was shownthat the surface shapes are in good agreement with different testing method.