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Proceedings Paper

Accuracy of geometric point spread function estimation using the ray-counting method
Author(s): Javier Portilla; Sergio Barbero
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Paper Abstract

The geometric point spread function (PSF) is an appropriate tool for modeling image degradation of an optical system, whenever the effect of diffraction is small compared to that of aberrations. The PSF is conventionally estimated by computing the density of ray intersections with the image plane (ray-counting method). We studied the effect of two factors on the estimation: the number of rays, using an error model, and the influence of the ray sampling pattern. We measured the accuracy of the PSFs estimation in three ideal cases, where we could derive an analytical expression for the irradiance. Additionally we estimated the PSFs generated by a single rear landscape lens. We have observed a consistent improvement of 4.5 dB (Signal-to-Noise Ratio) when doubling the number of rays. This ensures that an arbitrarily high accuracy on the estimation of geometric PSFs is theoretically attainable. However, the method is not very effcient because of the slow convergence rate. As an alternative, to avoid tracing a large number of rays, we investigated the benefits of interpolating rays intersections (using cubic splines) of the ray mapping. For instance, by interpolating only 100 traced rays we may obtain a similar quality in the estimation as when using 100 million of real traced rays. Among different uniform ray pupil sampling patterns (square, jittered square, hexapolar and hexagonal) we found that the hexagonal outperformed the other ones.

Paper Details

Date Published: 18 December 2012
PDF: 12 pages
Proc. SPIE 8550, Optical Systems Design 2012, 855003 (18 December 2012); doi: 10.1117/12.981183
Show Author Affiliations
Javier Portilla, Consejo Superior de Investigaciones Científicas (Spain)
Sergio Barbero, Consejo Superior de Investigaciones Científicas (Spain)

Published in SPIE Proceedings Vol. 8550:
Optical Systems Design 2012
Laurent Mazuray; Daniel G. Smith; Jean-Luc M. Tissot; Tina E. Kidger; Frank Wyrowski; Stuart David; Rolf Wartmann; Jeffrey M. Raynor; Andrew P. Wood; Pablo Benítez; Andreas Erdmann; Marta C. de la Fuente, Editor(s)

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