Large numbers of rays must be traced to obtain an accurate assessment of the sensitivity of a lens to certain manufacturing perturbations, such as optical surface irregularity and aspheric departures. To properly assess image quality changes, the perturbed lens must be re-focussed. This paper deals with the development and testing of an algorithm to automatically determine the focus of aberrated images with a computer.
Clarence P. Bray, Clarence P. Bray,
"The Development Of A Focus Determination For A Lens Tolerancing Computer Program", Proc. SPIE 0147, Computer-Aided Optical Design, (1 December 1978); doi: 10.1117/12.956627; https://doi.org/10.1117/12.956627