Patent ID: 7821626
Filing Date: 2010-10-26
Classification: G01B

Abstract:
1. An angle measuring device comprising: a light source; a photodetector; a collimator lens to collimate light emitted from the light source along its optical axis; a transmission diffraction grating which is placed in the optical axis, to make the parallel light passed through and make several lights of different orders; an optical system to form diffracted light reflected on a flat surface of an object at the position facing the transmission diffraction grating into an image on the photodetector after making the light passed through the transmission diffraction grating; a calculating device to calculate an angle of the object with respect to the optical axis using an image location on the photodetector and the order of the light formed as the image; a rotator to rotate the object so that an angle of the flat surface with respect to the optical axis is changed; and a controller which has order specifying information to relate a rotation position of the object by the rotator with each order of the diffracted light formed as an image on the photodetector, for specifying the order of the light formed as the image by rotation position information of the object and the order specifying information.