INTERFEROMETRIC ABSOLUTE AND REAL-TIME SURFACE CURVATURE SENSOR INSENSITIVE TO TILT, TRANSLATION AND VIBRATION

摘要

An apparatus and a method are disclosed to characterize curvature of a surface (16) of a sample. The apparatus (10) includes a reflector (14), a lens (12) characterized by having two focal planes and an optical source, such as a laser (20), that outputs measurement light that is directed to pass through the lens and to be reflected by the reflector. The reflector and lens are arranged so that when a sample surface of interest is positioned relative to the reflector such that the reflector and the sample surface are each located at one of the two focal planes of the lens, the sample surface becomes the image plane of itself for the lens, and beams bl and b2 of the measurement light are reflected at least twice from the sample surface and accumulate a path length difference, Delta, that is proportional to the curvature, kappa, of the sample surface. The apparatus further includes a detector (30) for detecting the path length difference.