Patent ID: 8373734

Claim:
An image forming apparatus, comprising; at least one image carrying body having a surface extending in a main scanning direction; a light exposing unit that emits a light toward the image carrying body in a light axis direction that is perpendicular to the main scanning direction according to a light exposing signal; a light sensor that is disposed to a side of the image carrying body to receive a part of the emitted light traveling in the light axis direction; a mask that is formed with a plurality of slits; and a control unit that detects a biased amount in a sub scanning direction of the emitted light of the light exposing unit based on a sensing result of the light sensor, the sub scanning direction being perpendicular to each of the main scanning direction and the light axis direction, wherein the light sensor comprises a plurality of light receiving elements arranged one next to the other along the main scanning direction, each of the light receiving elements receiving a respective light passing through a respective slit, and the plurality of light receiving elements comprise a plurality of photo sensors that respectively detect existence of the respective light.