Patent ID: 8144180

Claim:
An optical scanning apparatus comprising: a light source configured to emit a light beam; a polygonal mirror configured to deflect the light beam emitted from the light source; a drive unit configured to drive the polygonal mirror to rotate for scanning; an optical member on which the deflected light beam is incident; a storage member configured to house the polygonal mirror, the drive unit and the optical member therewithin; and a wall configured to partition a space inside the storage member into a first space that houses the polygonal mirror driven by the drive unit and a second space that houses the optical member, the wall having an opening to pass the deflected light beam toward the optical member and having a vent located between the polygonal mirror and the optical member when the vent is viewed from a direction parallel to a rotational axis of the polygonal mirror, the wall laterally extending on both lateral sides of the vent so that the first space is laterally enclosed and both lateral sides of the vent are bounded by the wall, wherein the vent is configured to allow at least a part of air that has passed through the opening from the first space toward the optical member in the second space to flow back into the first space while the polygonal mirror is rotating.