Scanning optical apparatus with a diffractive lens for compensating temperature dependent focus changes

摘要

A scanning optical apparatus includes a light source (1), deflector (5) for deflecting a light beam emitted from the light source, and optical device for directing the light beam emitted from the light source onto a surface to be scanned. The optical device includes a diffracting optical element (48). An aberration fluctuation in a sub-scanning direction resulting from environmental fluctuation of the scanning optical apparatus is corrected by the characteristic of the optical device.