Patent ID: 7940418
Filing Date: 2011-05-10
Classification: G03G

Abstract:
1. An image forming apparatus, comprising: an intermediate transfer medium movable in a sub-scanning direction and on which a toner image is transferred; a first photosensor including a first light emitting portion for projecting light upon a first side region of the intermediate transfer medium, and a first light receiving portion for receiving light reflected thereby; a second photosensor including a second light emitting portion for projecting light upon a second side region of the intermediate transfer medium, and a second light receiving portion for receiving light reflected thereby; and a control unit configured to perform calibration of the first photosensor by (i) using the first light emitting portion of the first photosensor to emit light directly upon an unmarked surface of the intermediate transfer medium, (ii) using the first light receiving portion of the first photosensor to detect an amount of light reflected directly from the unmarked surface of the intermediate transfer medium, and (iii) controlling an amount of light emitted from the first light emitting portion of the first photosensor such that the amount of reflected light detected by the first light receiving portion of the first photosensor is substantially equal to a pre-set reference light amount so as to calibrate the first photosensor, wherein the control unit is further configured to perform calibration of the second photosensor by (i) using the second light emitting portion of the second photosensor to emit light directly upon an unmarked surface of the intermediate transfer medium, (ii) using the second light receiving portion of the second photosensor to detect an amount of light reflected directly from the unmarked surface of the intermediate transfer medium, and (iii) controlling an amount of light emitted from the second light emitting portion of the second photosensor such that the amount of reflected light detected by the second light receiving portion of the second photosensor is substantially equal to a pre-set reference light amount so as to calibrate the second photosensor, wherein, after calibration of the first photosensor and the second photosensor, the control unit is configured to control forming toner images representing a first set of image concentration marks comprising a plurality of gray patterns having different concentrations and a second set of image concentration marks comprising a plurality of gray patterns having different concentrations on the image intermediate transfer medium as the intermediate transfer medium is moved in the sub-scanning direction, wherein the first set of image concentration marks and the second set of image concentration marks are separated from each other in a main-scanning direction, wherein, the control unit is configured to control forming toner images representing a first set of registration marks comprising four different colors and a second set of registration marks comprising four different colors on the intermediate transfer medium as the intermediate transfer medium is moved in the sub-scanning direction, wherein the first set of registration marks and the second set of registration marks are separated from each other in a main-scanning direction, wherein the first set of registration marks and the first set of image concentration marks are arranged at the first side region of the intermediate transfer medium so as to be detected by the first photosensor, and wherein the second set of registration marks and the second set of image concentration marks are arranged at the second side region of the intermediate transfer medium so as to be detected by the second photosensor, and wherein a color registration error and an image concentration error are compensated based on information obtained via detection of the toner images representing (i) the first set of registration marks, (ii) the first set of image concentration marks, (iii) the second set of registration marks, and (iv) the second set of image concentration marks formed on the intermediate transfer medium.