11 October 2010 Polarization point-diffraction interferometer for high-precision testing of spherical surface
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As a promising measurement tool for ultra-highly accurate testing of optical elements, the point diffraction interferometer has got good application in the high-precision spherical surface testing. It employs a nearly ideal spherical wavefront diffracted by a pinhole, enabling the measurement precision in the order of sub-nanometer. However, the poor fringe contrast due to low reflectivity of spherical surface under test, limits the measurement precision in process of fringe pattern analysis. In order to realize high-precision testing of spherical surface with adjustable contrast of fringe pattern, a polarization point diffraction interferometer (PPDI) is introduced, and the adjustable fringe contrast is realized by controlling the polarization states of reference and test beams. The interferometer has many advantages, such as simple in structure, easy to align and with adjustable fringe contrast. In order to achieve high accuracy, the main sources of systematic error and the corresponding calibration method have been studied in detail, including the spherical quality of diffracted wavefront, the wavefront distortion by polarizing elements, aberrations by geometric structure of the measurement system and optical properties of adopted elements and so on. The theory of the interferometer is presented, along with results of computer simulation. The analysis shows the proposed method can realize an accuracy of subnanometer level, and it is of great practicality for high-precision testing of spherical surfaces with low reflectivity.
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Daodang Wang, Daodang Wang, Yongying Yang, Yongying Yang, Chen Chen, Chen Chen, Yongmo Zhuo, Yongmo Zhuo, } "Polarization point-diffraction interferometer for high-precision testing of spherical surface", Proc. SPIE 7656, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 76560F (11 October 2010); doi: 10.1117/12.866682; https://doi.org/10.1117/12.866682

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