Patent ID: 7336367
Filing Date: 2008-02-26
Classification: G01D

Abstract:
1. A displacement detection device for detecting displacement of an inspection target having a diffraction grating in the direction of a lattice vector, on the basis of an interference signal, the device comprising: a light source for emitting light; a beam splitter for splitting the light emitted from the light source into two light beams and radiating the two light beams; a first lens provided between the light source and the beam splitter; reflection means for reflecting two first diffracted light beams obtained as the two light beams radiated from the beam splitter are diffracted by the diffraction grating; light splitting means for combining two second diffracted light beams obtained as the first diffracted light beams reflected by the reflection means are diffracted by the diffraction grating, to generate combined light, and then splitting the combined light into plural light beams; polarization means for transmitting only a predetermined polarized component of the split combined light; light-receiving means for photoelectrically converting coherent light transmitted through the polarization means and thus generating the interference signal; and a second lens provided between the polarization means and the light-receiving means.