| 摘要 |
PROBLEM TO BE SOLVED: To provide a scanning optical device capable of preventing the positional deviation of respective light beams emitted from plural light sources in a main scanning direction caused by the fluctuation of the wavelength of the light beam. SOLUTION: A 1st lens 400 constitutes an fθlens with 2nd and 3rd lenses 500 and 600, and the fθlens converges the light beams LA to LD made to scan in the main scanning direction by a polygon mirror 320 on photoreceptor drums 20A to 20D. The incident surface 410 of the lens 400 is a diffraction lens surface and constitutes Fresnel lens type diffraction lens structure having action to compensate transverse chromatic aberration at a diffraction lens part on a rotationally symmetric aspherical surface being a base curve. The diffraction lens structure has the action to compensate the transverse chromatic aberration in the main scanning direction by the fθlens. |
