Patent ID: 8422033

Claim:
An image forming apparatus comprising: an image carrier; an optical scanning device that scans the image carrier with a beam of light in a main-scanning direction, thereby forming a latent image, wherein the beam of light is modulated in accordance with image data; a developing device that forms a toner image by attaching toner to the latent image; a transferring device that transfers the toner image onto a medium; a reflective optical sensor that detects at least one of a position of or a toner density of a toner pattern on the image carrier or the medium, wherein the reflective optical sensor includes a light-emitting system that includes at least three light-emitting elements arranged at equal intervals in a certain direction; a lighting optical system that guides light emitted from the light-emitting system to the toner pattern; a light-receiving system that includes at least three light-receiving elements arranged at equal intervals in the certain direction, wherein the light-receiving system receives light reflected from the toner pattern, wherein the lighting optical system is arranged so that L/L 0 <P/S is satisfied, where L 0 is distance between the light-emitting system and the lighting optical system, L is distance between the lighting optical system and the image carrier when the toner pattern on the image carrier is detected; or L is distance between the lighting optical system and the medium when the toner pattern on the medium is detected, S is size of the light-emitting elements, and P is arrangement pitch of the light-emitting elements.