Patent ID: 7145126
Filing Date: 2006-12-05
Classification: G01D

Abstract:
1. An optical device comprising a primary grating; an incoherent light source disposed opposing a predetermined side of the primary grating; a first reference grating disposed between the light source and the primary grating; a photodetector disposed opposing the predetermined side of the primary grating; and a second reference grating disposed between the photodetector and the primary grating; wherein the primary grating, the first reference grating and the light source are configured for movement relative to one another; wherein a period Tr of the first reference grating and a period T of the second reference grating are related to a period T such that incoherent light from said incoherent light source remains incoherent as it impinges on said first reference grating, said primary grating and said second reference grating.