Patent ID: 7193730
Filing Date: 2007-03-20
Classification: G01B

Abstract:
1. An eccentricity measuring instrument of a polygon-mirror motor fixed a polygon mirror to an output shaft of the motor, the instrument comprising: (a) a first light source; (b) an optical position detecting element for detecting a position of a first reflection light beam, which is a first measuring light beam emitted from the first light source and reflected on the polygon mirror; (c) a second light source; (d) a photo detecting element for detecting a position of a second reflection light beam, which is a second measuring light beam emitted from the second light source and reflected on the polygon mirror; and (e) an eccentricity calculator for calculating an output from the optical position detecting element, where the output is taken when the photo detecting element detects the second reflection light beam, wherein the second measuring light beam forms a given angle with the second reflection light beam, and a plane formed by the first measuring light beam and the first reflection light beam intersects with a plane formed by the second measuring light beam and the second reflection light beam at right angles.