| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optical scanning optical device capable of substantially preventing image degradation even when reflected light from the boundary part of a polygon mirror reaches a surface to be scanned as flare light, and to provide an image forming device using the same. SOLUTION: In the optical scanning optical device including a light source means 2 having a first optical system 42 which makes incident light flux emitted from the light source means on a polygon mirror 10 having a plurality of deflection surfaces, and a second optical system 43 which image-forms light flux reflected to deflection by the polygon mirror in an effective scanning area on the surface to be scanned 12, the light source means is always turned on even when the outside of the effective scanning area is scanned by the light flux scans, and the boundary part of a deflection surface and a deflection surface adjacent to the deflection surface of the polygon mirror is formed in a ridgeline-like edge shape, then the width of the boundary part is set to 1% or less with respect to the light flux width in the main scanning direction of the light flux reflected to deflection by the polygon mirror. |
