Optical scanning device that directs heat away from a deflector and image forming device including same

An optical scanning device that scans a target surface with light, comprising:

• a light source;
• a deflector that deflects light of the light source;
• and
• an optical system that forms, on the target surface, an image of light deflected by the deflector,
• wherein the deflector includes:
• a polygon mirror that reflects and deflects light of the light source while being rotated;
• a motor that rotates the polygon mirror;
• and
• a case body that airtightly houses the polygon mirror and the motor,
• the case body includes a cylindrical inner wall surrounding an outer periphery of the polygon mirror, and
• the inner wall includes, on an inner surface, a rectifier that guides, from one to the other of a first space and a second space, an air flow generated by rotation of the polygon mirror in a space surrounded by the inner wall so that overheating of the polygon mirror is prevented and a risk of turbulence around the polygon mirror is minimized, and the first space is located on the motor side with respect to the polygon mirror and the second space is located on an opposite side of the first space.