Abstract: A measuring instrument of polygon mirror motors includes a first light source, a first photo detecting element for detecting a first reflected light beam, i.e. first measuring light beam emitted from the first light source and reflected from the polygon mirror, a second light source, a second photo detecting element for detecting a second reflected light beam, i.e. second measuring light beam emitted from the second light source and reflected from the polygon mirror; and a calculator for performing a calculation based on a time difference between an output from the first photo detecting element and an output from the second photo detecting element. The calculator outputs at least one of an eccentricity and a level difference between facets of the polygon mirror.

Abstract: An eccentricity measuring instrument of polygon mirror motors includes a first light source, an optical position detecting element for detecting a position of first reflection light, i.e. first measuring light emitted from the first light source and reflected on the polygon mirror, a second light source, a photo detecting element for detecting a position of second reflection light, i.e. second measuring light emitted from the second light source and reflected on the polygon mirror; and an eccentricity calculator for calculating an output, at a detection of the second reflection light by the photo detecting element, from the optical position detecting element. The second measuring light forms a given angle with the second reflection light, and a plane formed by the first measuring light and the first reflection light intersects with a plane formed by the second measuring light and the second reflection light at right angles.

Abstract: A measuring instrument of polygon mirror motors includes a first light source, a first photo detecting element for detecting first reflecting light beam, i.e. first measuring light beam emitted from the first light source and reflected on the polygon mirror, a second light source, a second photo detecting element for detecting second reflecting light beam, i.e. second measuring light beam emitted from the second light source and reflected on the polygon mirror; and a calculator for carrying out a calculation based on a time difference between an output from the first photo detecting element and an output from the second photo detecting element. The calculator outputs at least one of an eccentricity and a level difference between facets of the polygon mirror.

Abstract: An eccentricity measuring instrument of polygon mirror motors includes a first light source, an optical position detecting element for detecting a position of first reflection light, i.e. first measuring light emitted from the first light source and reflected on the polygon mirror, a second light source, a photo detecting element for detecting a position of second reflection light, i.e. second measuring light emitted from the second light source and reflected on the polygon mirror; and an eccentricity calculator for calculating an output, at a detection of the second reflection light by the photo detecting element, from the optical position detecting element. The second measuring light forms a given angle with the second reflection light, and a plane formed by the first measuring light and the first reflection light intersects with a plane formed by the second measuring light and the second reflection light at right angles.