Patent ID: 6952256
Filing Date: 2005-10-04
Classification: G01N

Abstract:
1. An objective lens system suitable for achieving a high numerical aperture and a long working distance and reconfigurable such that, in different configurations the system enables the inspection of an object through pellicles of different thicknesses as well as in the absence of a pellicle, the system comprising: a first group of optical elements suitable for achieving a high numerical aperture and achieving beam contraction for light passing through the first group of optical elements; a second group of optical elements that, when switched to a first mode, enables the lens system to inspect an object through a thin pellicle and to inspect the object in the absence of a pellicle, and when switched to a second mode enables the lens system to inspect an object through a thick pellicle wherein the second group of optical elements, when switched to the second mode, induces an optical aberration that compensates for optical aberrations caused by the thick pellicle, thereby enabling the objective lens system to image the object through the thick pellicle.