| US 7,609,430 B2 | ||
| Optical beam scanning device restraining beam position error due to temperature change with diffraction grating and image forming apparatus using the same | ||
| Takashi Shiraishi, Kanagawa-ken (Japan) | ||
| Assigned to Kabushiki Kaisha Toshiba, Tokyo (Japan); and Toshiba Tec Kabushiki Kaisha, Tokyo (Japan) | ||
| Filed on Jul. 05, 2007, as Appl. No. 11/773,494. | ||
| Prior Publication US 2009/0009843 A1, Jan. 08, 2009 | ||
| Int. Cl. G02B 26/08 (2006.01) | ||
| U.S. Cl. 359—204.5 [359/206.1] | 5 Claims |
| 1. An optical beam scanning device that shapes a diverging ray from a light source to be a light beam having a predetermined
sectional shape in a pre-deflection optical system including plural optical elements and deflects the light beam shaped by
the pre-deflection optical system with a rotating deflector to cause the light beam to scan in a main scanning direction,
wherein
the pre-deflection optical system has optical elements arranged between the light source and reflecting surfaces of the rotating
deflector in a light beam traveling direction and having negative power,
among the plural optical elements forming the pre-deflection optical system, in at least one optical element in which a principal
ray of the light beam from the light source is made incident on a position of incidence different from an optical path of
an optical axis of the pre-deflection optical system in a sub-scanning direction orthogonal to the main scanning direction,
a diffraction grating is formed on at least one of a plane of beam incidence and a plane of beam exit in the optical element,
and
the optical element having the diffraction grating formed therein has a plane of incidence formed as a convex surface and
a plane of exit formed as a concave surface.
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