Abstract

Testing the surface texture of a machined object, thin films, soft materials requires a noncontact, high precision surface measuring system. The use of the optical signal for surface profile generation gives advantage over a mechanical stylus system because of its nondestructive nature.¹ In this method, a laser beam of predetermined Gaussian profile² is focused via a lens into the measuring surface. The reflected beam is separated by a polarizing prism from the incoming beam and taken to a quadrant detector. When the beam is focused all detector segments receive equal amounts of light, but when the surface moves in or out of focus it creates an imbalance of light falling on the quad detectors. The difference of the detector signals acts as an error signal that provides a direct measure of the profile of the surface.

© 1991 Optical Society of America