Optical Free-Form Surface Subaperture Stitching Interferometry

With great degrees of freedom, optical free form surfaces would provide the axial aberrations and off axis ones. Meanwhile, they meet requirements of modern optical systems in high-performance, weight reduction and micromation. Therefore, they gradually becomes the favor of modern optical engineering. However, their application have been limited by the strict requirement of image systems, especially the testing has been the most important limitation.As one of the most precise testing methods, interferometry has made a great achievement in testing of optical planes, spherical surfaces as well as aspherical surfaces. Null interferometry possess a high measurement accuracy with special compensators, but has obstacle in designing, testing and alignment of these compensators. For a free form surface of irregular and asymmetric rotational shape, the specialized computer generated hologram (CGH) is necessary. However, the high cost and difficulty of CGH fabrication restrict its application. Researchers then turned to subaperture stitching interferometry (SSI). But SSI still made no progress in free form surface testing although it has contribute to test of large aperture spherical surfaces and mild aspherical ones.This dissertation mainly research on the free form surface subaperture stitching interferometry (FSSI).The content of the dissertation include:The system design and simulation of FSSI is researched. The irregular subaperture partition is proposed based on the irregular shape of test surface.The irregular subaperture partition method is researched with the simulation example. Also, the characterized polynomials of irregular subaperture wavefront is deduced. These researches provide the principle basis for FSSI.A large difficulty is matching localization of free form surface in interferometry. We proposed a set of matching localization methods to match the location of test surface in experiment and simulation, including rotation matching, axial position matching and location matching. These researches complete the accurate model of test surface.After the subaperture partition and system modeling, the stitching method is researched. We proposed the multi-aperture simultaneous reverse optimizing reconstruction (MSROR) algorithm. The accuracy of MROR algorithm is simulated. As the most important component of FSSI, the MROR algorithm also is employed for aspheric vertex radius of curvature (VROC) determination.The FSSI model machine is introduced and its error calibration is discussed.The reverse optimization calibration technique is developed for FSSI system error calibration. The calibration experiment is carried out to provide the accuracy guarantee for FSSI.Final research is experimental validation of FSSI. Three validation experiments are carried out. The aspheric VROC determination accuracy is 0.016% comparing with result of ZYGO GPI. The aspheric annular subaperture stitching accuracy is more than 1/50λ (rms) comparing with result of ZYGO verifire interferometer. The bi-conic surface sector subaperture stitching accuracy is about 1/50λ (rms) comparing with result of Taylor Hobson contourgraph in longitudinal section contour. All these verify the accuracy of FSSI, evolving the FSSI theory into reality.