Optical scanning apparatus and image forming apparatus

An optical scanning apparatus comprising:

• a light source that emits a beam light including a first polarization component;
• a deflection mirror that is rotationally driven so as to reflect the beam light toward a scanned object while scanning in a main scanning direction;
• a first polarizing member that reflects the first polarization component included in the beam light toward the deflection mirror and passes a second polarization component having a phase difference of a half-wavelength with respect to the first polarization component;
• and
• a second polarizing member that causes a phase difference of a quarter wavelength to the passing beam light, wherein
• the first polarizing member is provided such that the beam light reflected by the first polarizing member squarely enters the deflection mirror from substantially a center of a deflection angle of the deflection mirror,
• the second polarizing member is provided between the first polarizing member and the deflection mirror to pass the first polarization component of the beam light reflected by the first polarizing member therethrough twice before and after being reflected by the deflection mirror so as to change the first polarization component into the second polarization component, and
• a rotation axis of the deflection mirror is parallel to an optical axis of the beam light immediately before being reflected by the first polarizing member.