US Patent 7623280 Optical scanning device and image forming apparatus

An optical scanning device includes a light source configured to emit light beams, a deflector to deflect the light beams emitted from the light source, a first optical assembly which is positioned upon a light path of the light beams traveling from the light source to the deflector and which forms an image with the light beams emitted from the light source in a sub scanning direction in a vicinity of the deflector, and a second optical assembly to form the image upon a surface to be scanned with the light beams deflected by the deflector. A principal ray of two of the light beams incident to the first optical assembly, which are located at each respective terminus in the sub scanning direction, are set so as to advance so as either to remain mutually parallel to or converge with one another after passing through the first optical assembly.