| 摘要 |
To provide a technique that can appropriately correct an optical characteristic according to fluctuation in an environmental temperature. 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 7 including plural optical elements and deflects the light beam shaped by the pre-deflection optical system 7 with a polygon mirror 80 to cause the light beam to scan in a main scanning direction, wherein the pre-deflection optical system 7 has optical elements 79 arranged between the light source and reflecting surfaces of the polygon mirror 80 in a light beam traveling direction and having negative power and, among the plural optical elements forming the pre-deflection optical system 7, in at least one optical element in which a principal ray of the light beam from the light source is made incident on an position of incidence different from an optical path of an optical axis of the pre-deflection optical system 7 in a sub-scanning direction orthogonal to the main scanning direction, a diffraction grating is formed on at least one of a plane of incidence and a plane of exit of the light beam in the optical element.
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