Patent ID: 8373736

Claim:
An optical scanning device that scans a target surface with a light beam, the scanning device comprising: a light source unit that outputs a light beam; a deflector that receives the light beam from the light source unit and deflects the light beam; and a scanning optical system that focuses the light beam deflected by the deflector on the target surface, wherein the scanning optical system includes a polarization splitting element, a reflective optical element, and a conversion optical system, the polarization splitting element receives the light beam from the deflector and, when the light beam is polarized in a first-polarized state, transmits the light beam, the conversion optical system is arranged in an optical path of the light beam that is in the first-polarized state and passes through the polarization splitting element, receives the light beam from the polarization splitting element, and converts the light beam in the first-polarized state to a second-polarized state, the reflective optical element receives the light beam in the second-polarized state from the conversion optical system, converts the light beam in the second-polarized state to a third-polarized state, and reflects the light beam in the third-polarized state toward the conversion optical system, the conversion optical system converts the light beam in the third-polarized state that is reflected by the reflective optical element to a fourth-polarized state and outputs the light beam toward the polarization splitting element, the polarization splitting element receives the light beam in the fourth-polarized state from the conversion optical system and deflects the optical path of the light beam in the fourth-polarized state into a direction toward the target surface, and wherein the scanning optical system includes a transmissive-type image-forming optical element, the transmissive-type image-forming optical element being arranged between the polarization splitting element and the reflective optical element, and both the light beam moving from the polarization splitting element toward the reflective optical element and the light beam moving from the reflective optical element toward the polarization splitting element pass through the transmissive-type image-forming optical element.