7 September 2013 New design of null screens to simplify the correspondence during the quantitative evaluation of optical surfaces
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Abstract
We have been working in a method for testing fast aspheric convex surfaces with flat null screens in an array of LCD’s, based on the null screen principles accordingly; i.e. we have demonstrated qualitatively that using three LCD’s forming a triangular prism, we can evaluate aspheric fast surfaces instead of using the traditional test with a cylindrical null screen. This setup of LCD’s has the advantage of display a series of 3 null screens for sampling an optical surface simultaneously, where in the ideal case, the position of the drop-shaped spots should be forming a regular square array of points in the image plane. However, due to typical problems of illumination and directionality with the transmitted light through the LCD's, some spots on the image are missing which complicates the correspondence between centroids and coordinates of the null screens; this is important for the numerical integration procedure used for the quantitative evaluation . In this paper we propose the design of null screens with reference marks, which provide unambiguous correspondence. Specific designs include some strategic color and position coding to ease the image spots identification. We show the method as used during the quantitative evaluation of a spherical steel ball.
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M. I. Rodríguez Rodríguez, A. Jaramillo-Núñez, R. Díaz-Uribe, "New design of null screens to simplify the correspondence during the quantitative evaluation of optical surfaces", Proc. SPIE 8838, Optical Manufacturing and Testing X, 883810 (7 September 2013); doi: 10.1117/12.2023528; https://doi.org/10.1117/12.2023528
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