Patent ID: 7554568

Claim:
An optical beam scanning device, comprising: a light source; a deflection reflecting surface for deflecting to scan light from the light source on a recording medium; and a diaphragm device provided between the light source and the deflection reflecting surface, the diaphragm device having a nonplanar light shielding section, and an aperture formed by the nonplanar light shielding section, the light shielding section making a light shielding quantity of the light from the light source in a vertical scanning direction different in positions of a horizontal scanning direction and a light advancing direction, wherein the light shielding section is composed of at least two or more nonplanar light shielding plates which have a predetermined angle to the horizontal scanning direction wherein the nonplanar light shielding plates are inclined at the predetermined angle to the horizontal scanning direction to adjust the light quantity emitted from the light source passing through the aperture.