Optical scanning device and image forming apparatus using the same

An optical scanning device comprising:

• a light source unit including a light source for emitting a first light beam and a second light beam that are to be irradiated on a scanned surface, and an incidence optical system for the first light beam and the second light beam, the light source unit configured to emit the first light beam and the second light beam with angles respectively with respect to a reference line perpendicular to a sub scanning direction such that the first light beam and the second light beam are aligned in the sub scanning direction and an interval between the first light beam and the second light beam in the sub scanning direction expands toward the scanned surface;
• a deflector configured to reflect the first light beam and the second light beam emitted from the light source unit such that the first light beam and the second light beam scan the scanned surface in a main scanning direction;
• and
• a scanning lens disposed between the deflector and the scanned surface, including an incident surface and an emission surface, and configured to focus the first light beam and the second light beam on the scanned surface, wherein
• at least one of the incident surface and the emission surface is an optical refractive surface in which a first refractive surface and a second refractive surface are arranged in alighnment in the sub scanning direction, wherein the first light beam passes through the first refractive surface and the second light beam passes through the second refractive surface, and
• an interval between a first generatrix of the first refractive surface and a second generatrix of the second refractive surface in the sub scanning direction increases from a center portion toward end portions of the scanning lens in the main scanning direction.