Optical scanning device and image forming device

An optical scanning device steering, in a main scanning direction, a light beam emitted from a light emitting element using a deflector, the optical scanning device comprising:

• a collimator lens disposed between the light emitting element and the deflector, and converting the light beam emitted from the light emitting element into parallel light;
• an aperture cutting part of the light beam, and forming the light beam into a rectangular beam;
• a condensing lens disposed on a downstream side of the light beam with respect to the deflector, and condensing the light beam, deflected by the deflector, toward an object to be scanned;
• and
• a light condensing and diffusing member disposed between the aperture and the deflector, and having a first function to condense the light beam in a sub-scanning direction and a second function to diffuse the light beam in the main scanning direction, wherein:
• divergent angles of the light beam emitted from the light emitting element in two intersecting directions are different from each other,
• a direction of the two intersecting directions, for which a light beam divergent angle is large, is aligned with the sub-scanning direction,
• a direction of the two intersecting directions, for which a light beam divergent angle is small, is aligned with the main scanning direction, and
• a linewidth of the light beam in the sub-scanning direction is wider than a linewidth of the light beam in the main scanning direction at a point of time when the light beam passes through the collimator lens.