Patent ID: 8581950

Claim:
An image forming apparatus comprising: a plurality of image carriers; a laser exposure unit which includes a plurality of laser units, each of which emits a laser beam, the laser exposure unit forming a latent image on each of the image carriers by performing main scanning and sub-scanning on each of the image carriers with the laser beams emitted from the laser units; and a processing unit which transfers the latent image formed on each of the image carriers to a medium, wherein the laser exposure unit further includes: a plurality of laser beam detection sensors, each of which detects, as a reference position of the main scanning, one of the laser beams emitted from the laser units; a measurement section which measures a difference in detection timings of the laser beam detection sensors; a detection section configured to detect an abnormality in one or more of the laser beam detection sensors; a generation section which generates, when an abnormality is detected in one of the laser beam detection sensors, a signal corresponding to an output signal of the laser beam detection sensors in which the abnormality is detected, based on the output signal of the laser beam detection sensors in which an abnormality is not detected and the measured difference; and a laser controller which controls the laser unit corresponding to the laser beam detection sensor in which an abnormality is not detected by the detection section, based on the output signal of the laser beam detection sensor in which an abnormality is not detected, and which controls the laser unit corresponding to the laser beam detection sensor in which an abnormality is detected by the detection section, based on the signal generated by the generation section.