Light beam scanner unit and image forming apparatus with adjustment for contamination

摘要

A light beam scanner unit includes a light beam generating unit for generating light beams at a fixed power, a polygon mirror for reflecting light beams generated from the light beam generating means toward a surface to be scanned, thereby scanning it, and a light beam power sensing unit for sensing light beam power for scanning a surface to be scanned with the polygon mirror. This light beam scanner unit further has a mirror contamination sensing unit for sensing contamination of the polygon mirror by comparing a sensing result obtained from the light beam power sensing unit when light beams are emitted by the light beam generating unit with a preset reference value.