Patent ID: 8265501

Claim:
An image forming apparatus, comprising: a photosensitive body; an exposing unit which exposes a surface of the photosensitive body to form an electrostatic latent image on the surface of the photosensitive body; a developing unit which attaches a developer to the electrostatic latent image to form a developer image corresponding to the electrostatic latent image formed on the surface of the photosensitive body; a carrier body, which is moved through a portion opposite to the photosensitive body and onto which the developer image formed on the photosensitive body is to be transferred; a mark forming unit which controls the exposing unit to form a mark made from the developer image on a surface of the carrier body; a light sensor which senses light reflected by the carrier body; an edge detector which senses edges of the mark formed on the surface of the carrier body based on an output of the light sensor; and a deciding unit which decides a positional relation between a focal point of the exposing unit and the surface of the photosensitive body based on the detected edge detected by the edge detector.