26 June 2017 New technique for generating light source array in tilted wave interferometer
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Smaller and lighter optical systems with better performance can be built by the use of freeform optics. However, most optical systems were constrained to traditional surfaces for the accurate metrology of freeform surface is a challenge so far unsolved. One high-precision approach to measure freeform surface with less time and expense is using tilted wave interferometer. A lens array is placed in the test path of the interferometer, which can generate light source array that locally compensate the gradient of test surface. But each source generated by lens array is not ideal spherical wave which contains aberrations. In addition, the sources cannot be activated individually during the measurement, so that it is impossible to perform an irregular source array according to the gradient variation of each test surface. Thus, a novel technique based on fiber array is proposed for generating irregular source array. Whereas, the position deviation of each fiber and phase difference produced by the length of each fiber affect the measurement result. In this paper, the consequences of above errors are analyzed. A calibration method can obtain the exact spatial coordinates of each fiber is suggested to calculate the position deviation of each fiber. Meanwhile, a method based on Mach-Zehnder interference system is presented, which can get phase difference produced by the length of each fiber accurately. Afterwards, the data obtained by the two calibration methods are introduced into the mathematical model of system error for eliminating the measurement error introduced by the use of fiber array. An elliptical mirror is measured by our tilted wave interferometer based on fiber array showing the feasibility of the proposed methods.
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Jia Li, Jia Li, Hua Shen, Hua Shen, Rihong Zhu, Rihong Zhu, Qing Lu, Qing Lu, } "New technique for generating light source array in tilted wave interferometer", Proc. SPIE 10329, Optical Measurement Systems for Industrial Inspection X, 1032928 (26 June 2017); doi: 10.1117/12.2271603; https://doi.org/10.1117/12.2271603

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