12 January 2018 Brightness checkerboard lattice method for the calibration of the coaxial reverse Hartmann test
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The coaxial reverse Hartmann test (RHT) is widely used in the measurement of large aspheric surfaces as an auxiliary method for interference measurement, because of its large dynamic range, highly flexible test with low frequency of surface errors, and low cost. And the accuracy of the coaxial RHT depends on the calibration. However, the calibration process remains inefficient, and the signal-to-noise ratio limits the accuracy of the calibration. In this paper, brightness checkerboard lattices were used to replace the traditional dot matrix. The brightness checkerboard method can reduce the number of dot matrix projections in the calibration process, thus improving efficiency. An LCD screen displayed a brightness checkerboard lattice, in which the brighter checkerboard and the darker checkerboard alternately arranged. Based on the image on the detector, the relationship between the rays at certain angles and the photosensitive positions of the detector coordinates can be obtained. And a differential de-noising method can effectively reduce the impact of noise on the measurement results. Simulation and experimentation proved the feasibility of the method. Theoretical analysis and experimental results show that the efficiency of the brightness checkerboard lattices is about four times that of the traditional dot matrix, and the signal-to-noise ratio of the calibration is significantly improved.
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Xinji Li, Xinji Li, Mei Hui, Mei Hui, Ning Li, Ning Li, Shinan Hu, Shinan Hu, Ming Liu, Ming Liu, Lingqin Kong, Lingqin Kong, Liquan Dong, Liquan Dong, Yuejin Zhao, Yuejin Zhao, } "Brightness checkerboard lattice method for the calibration of the coaxial reverse Hartmann test", Proc. SPIE 10621, 2017 International Conference on Optical Instruments and Technology: Optoelectronic Measurement Technology and Systems, 1062104 (12 January 2018); doi: 10.1117/12.2288068; https://doi.org/10.1117/12.2288068

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