Patent ID: 6067370
Filing Date: 2000-05-23
Classification: G06K

Abstract:
A method of checking static field uniformity of an optical system illuminated by an illumination system comprising the steps of:(a) acquiring an image of a calibration and test target with the optical system wherein the image further comprises a plurality of image pixels;(b) determining the static field uniformity of the optical system from the image of the calibration and test target, wherein the static field uniformity is a function of spatial response of sensors in the optical system;(c) storing a plurality of mean intensity values, where a mean intensity value is stored for each one of the plurality of image pixels;(d) tabulating the plurality of mean intensity values in a histogram format to form a mean value distribution;(e) determining a maximum value, a minimum value and a distribution mean value for the mean value distribution;(f) determining a coefficient of variation for the mean value distribution; and(g) comparing the maximum value, minimum value, and distribution coefficient of variation against a set of predetermined specifications.