Patent attributes
An even number of reflection mirrors reflecting a light beam in the sub-scanning direction are disposed on an optical path from a deflecting reflection surface of an optical deflector to a corresponding surface to be scanned, for a light beam that is incident on the deflecting reflection surface from one side of a line normal to the deflecting reflection surface in the sub-scanning direction. An odd number of reflection mirrors reflecting the light beam in the sub-scanning direction is disposed on the optical path, for a light beam that is incident on the deflecting reflection surface from the other side of the line normal to the deflecting reflection surface in the sub-scanning direction.