Optical scanning apparatus and image forming apparatus

摘要

An optical scanning apparatus includes a light source for radiating a light beam, an optical scanning system for deflecting the light beam from the light source and condensing the light beam on a surface to be scanned, a detecting device for detecting an image forming state of the light beam scanned by the optical scanning system, and an adjusting mechanism for adjusting the focal position of the light beam on the surface to be scanned. The detecting device includes a very low cost detecting element that can accurately detect an image forming state of the light beam scanned by the optical scanning system independently in a main scanning direction and in a sub scanning direction. While the focal position of the light beam is changed continuously or at a predetermined pitch by the adjusting mechanism, the detecting device monitors the image forming state of the light beam and detects the location and vicinity of a light beam waist position relative to a desired position on the surface to be scanned.