Patent ID: 8218989

Claim:
An image forming apparatus that transfers a toner image carried by an image carrier onto a sheet, comprising: a photo detector unit disposed in facing relation to the image carrier, for detecting reflected light from the image carrier; a circumferential location identification unit adapted to perform pattern matching between amounts of reflected light detected by said photo detector unit during one rotation of the image carrier and an amount of reflected light detected by said photo detector unit from a specific portion of the image carrier in a circumferential direction of the image carrier, to thereby identify a first circumferential location of the specific portion of the image carrier in the circumferential direction of the image carrier and then identify a second circumferential location of a detection toner image formed on the image carrier based on the identified first circumferential location; a density calculation unit adapted to calculate density of the detection toner image based on an amount of reflected light from the detection toner image, which is detected by said photo detector unit, and an amount of reflected light from a portion of the image carrier in the second circumferential location identified by said circumferential location identification unit, out of amounts of reflected light from the image carrier corresponding to one rotation of the image carrier, which are detected by said photo detector unit; and a density control unit adapted to control density of a toner image to be formed on the image carrier, according to the density of the detection toner image calculated by said density calculation unit; wherein the specific portion of the image carrier is a portion of the image carrier exposed between toner images sequentially formed on the image carrier.