Patent ID: 6259531
Filing Date: 2001-07-10
Classification: G01D,G01P,G01S

Abstract:
An apparatus for detecting displacement information of an object including:a light source unit;deflecting means for deflecting a light beam from said light source unit so that the light beam deflected by said deflecting means is incident on said object; anda photodetector for detecting the light from said object caused upon the incidence of the light beam thereon by said deflecting means, information regarding the relative displacement to said object along a predetermined direction being detected on the basis of a light detection signal from said photodetector;wherein said deflecting means includes a diffraction grating for diffracting the light beam to be incident on said object, said diffraction grating being formed so that substantially only one predetermined order diffraction light beam applied to said object may be condensed on said object in a direction in which the relative displacement to said object cannot be detected by the signal from said photodetector.