4 September 2009 High-precision profile measurement of a small radius lens by surface gradient integrated profiler
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Abstract
A new concept profiler has been developed to measure items such as asymmetric and aspheric profiles with a small radius curvature lens and mirrors. In this study, the normal vectors at each point on the surface are determined by a reflected light beam that returns along exactly the same path as the incident beam. In order to measure a small radius curvature, a compact measuring instrument was redesigned according to the above principle of the measuring method employed. The instrument is 1200 mm (W) × 1000 mm (H) × 1500 mm (V). The measurement of normal vectors of a spherical lens, which has a small f number such as a 25 mm radius curvature, has been demonstrated with a measuring accuracy for the normal vector of 0.1 μrad. The surface gradient at each point is calculated from the normal vector, and the surface profile is obtained by integrating the gradient. When integrating the gradient, measured position accuracy should be in the order of 10 nm. They were obtained by self-calibration techniques that have already developed by the authors. In this paper, we discuss methods of calculating absolute radius curvature and deviation from the ideal surface profile.
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Y. Ueno, Y. Higashi, S. Tachibanada, J. Uchikoshi, T. Kume, K. Enami, H. Uchimura, K. Tanaka, K. Endo, "High-precision profile measurement of a small radius lens by surface gradient integrated profiler", Proc. SPIE 7448, Advances in X-Ray/EUV Optics and Components IV, 744804 (4 September 2009); doi: 10.1117/12.826833; https://doi.org/10.1117/12.826833
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