Patent ID: 6567572
Filing Date: 2003-05-20
Classification: G01D,G02B

Abstract:
An optical displacement sensor for measuring vertical displacement of a reflector, comprising:(a) an optically transparent substrate; (b) a reflective grating deposited on said substrate; (c) a light source to provide optical illumination on said reflector through said substrate and said reflective grating; (d) said reflector positioned at a vertical distance that is substantially less than half the coherence length of said light source over and with respect to said substrate and said reflective grating, and said reflector positioned substantially parallel to said substrate and said reflective grating; (e) one or more photo-detectors to monitor reflected and diffracted light from said reflector and said reflective grating; and (f) a wafer with at least one aperture for light transmission from said light source and said wafer comprises said one or more photo-detectors.