| 摘要 |
PROBLEM TO BE SOLVED: To provide a scanning optical device capable of preventing the positional deviation in a main scanning direction of a light beam caused by the fluctuation of the wavelength of the light beam from the light source of each scanning optical system. SOLUTION: A 1st fθlens 400 constitutes an fθlens group with 2nd and 3rdθlenses 500 and 600, and the fθlens group converges the light beam B made to scan in the main scanning direction by a polygon mirror 320 on a photoreceptor drum 20A. The incident surface 410 of the lens 400 is a diffraction lens surface, and Fresnel lens state diffraction lens structure 412 having action to compensate transverse chromatic aberration at a refraction lens part is constituted on a rotationally symmetric aspherical surface being a base curve. The structure 412 has the action to compensate the transverse chromatic aberration in the main scanning direction by the fθlens group.
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