Patent ID: RE40551

Claim:
A device utilizing light diffraction for measuring translation, rotation or velocity, the device comprising: a light source emitting an incident light beam; at least one light detector for detecting a resultant portion of the incident light beam emitted from the light source interference beam ; a diffraction grating assembly located on a light path of the incident light beam between the light source and the at least one light detector, the diffraction grating assembly comprising a fixed first reflective grating assembly and a mobile second reflective grating assembly , ; wherein the mobile first grating assembly is mobile along a given displacement relative to the fixed second grating assembly ; , wherein the fixed reflective grating assembly and the mobile reflective grating assembly diffract first and second grating assemblies are arranged to diffract at least a portion of the incident light beam , the incident light beam reaching the first grating assembly where the incident light beam is partially diffracted along two different directions thereby producing interference and the resultant portion of the incident light beam detected by the at least one light detector forming two partial light beams which reach the second grating assembly, and, thereafter, the first grating assembly, thereby forming, after diffraction by the first grating assembly, the resultant interference beam resulting from interference of the two partial light beams along an output direction, and wherein the resultant interference beam is directed at a resultant angle in a plane perpendicular to lines along which the first grating assembly and the second grating assembly are formed, the resultant angle having a value substantially equal to an angle of incidence in this perpendicular plane of the incident light beam multiplied by <<− 1 >> relative to an axis perpendicular to the first grating assembly and the second grating assembly, said at least one detector being arranged such that light beams interfering along the resultant- angle are measured by the at least one detector for determining a relative displacement .