Efficient automatic computation of veiling glare from scatter and ghosts by a simple modification to Monte-Carlo ray tracing

摘要

Veiling glare is a somewhat obsolete term referring to stray light from an in-field extended source bleeding into adjacent dark regions of the image. In most systems ghost reflections and scatter from the contaminated or imperfectly polished optical surfaces are the main culprits. Standard stochastic or deterministic methods for calculating scattered light from out-of-field sources are cumbersome in this domain. On the other hand, basic Monte Carlo ray tracing is straightforward. Its implementation in the GelOE optical engineering software is based on a fast hybrid physical-optics/geometrical-optics technique for surface scatter. However, a prohibitive number of rays are still required to get accurate results. Instead of the standard ray-splitting and importance-area modifications to make it more efficient, a much simpler one is proposed and then applied to a representative lens system, resulting in a 100 to 1000 fold reduction in the number of rays required for the same accuracy.