Optical Testing Method and Apparatus

Abstract

Estimating one or more optical characteristics of a Device-Under-Test (DUT). The method, includes directing an optical wavefront, generated by a source, towards a test location and generating at least one ray from the wavefront at the test location. Then for each ray at two or more measurement planes, each measurement plane transverse to the direction of travel of the wavefront and beyond the test location relative to the source at different optical path distances, measuring respective points of intersection of the ray with the measurement planes with and without the DUT at the test location. Followed by determining the transverse aberration due to the DUT for the ray at each measurement plane; and the estimating for each measurement plane from the determined transverse aberrations the coefficients of a general transverse aberration equation, the coefficients of which are the product of a combination of optical characteristics and the optical distance between the measurement plane and the appropriate principal plane of the DUT. The optical characteristics are calculated from the estimates of the coefficients for each measurement plane and the optical distances between respective measurement planes.