Patent ID: 7102760
Filing Date: 2006-09-05
Classification: G01D,H03M

Abstract:
1. An optical displacement sensor comprising; a surface emitting laser light source which emits a light beam; a scale which is moveable with respect to the surface emitting laser light source along a relative movement direction, and which includes a first track pattern and a second track pattern formed thereon to extend in parallel along the relative movement direction, at least the first track pattern comprising a grating pattern which has a predetermined period along the relative movement direction; a beam-splitting optical element which splits the light beam emitted by the surface emitting laser light source into a first light beam and a second light beam which are respectively radiated to the first track pattern and the second track pattern and which form respective angles with a principal axis of the light beam emitted from the surface emitting light source, said respective angles being symmetric with respect to the principal axis when viewed from the relative movement direction; a beam-bending optical element, which bends the first light beam and the second light beam respectively reflected and diffracted by the first track pattern and the second track pattern, such that the first light beam and the second light beam are bent to travel in a direction substantially the same as the principal axis of the light beam just emitted from the surface emitting laser light source when viewed from the relative movement direction; a first photodetector having a light receiving surface which detects movement of a diffraction image of the first light beam reflected and diffracted by the first track pattern, said light receiving surface including a plurality of sets of light receiving areas, wherein the light receiving areas in the sets are arranged at intervals of p a second photodetector including a light receiving surface which detects movement of a diffraction image of the second light beam reflected and diffracted by the second track pattern; wherein wherein the surface emitting laser light source, the first photodetector and the second photodetector are provided on a same side of the scale, and the light receiving surfaces of the first and second photodetectors are substantially parallel to the patternformed surface of the scale; and wherein the movement of the scale with respect to the surface emitting laser light source is detected based on outputs of the first photosensor and the second photosensor.