IMAGE FORMING APPARATUS AND OPERATION METHOD OF IMAGE FORMING APPARATUS

An image forming apparatus includes a lens, first and second light sensors, a change amount detector, and a controller. The lens is in one of laser scanning systems. The first light sensor is in the one of the laser scanning systems at a position such that the scanning beam is incident on a detection surface thereof. The second light sensor is adjacent to the first light sensor and angled with respect to the first light sensor. The second light sensor is arranged such that the scanning beam is also incident on a detection surface thereof. The change amount detector is configured to detect a time interval of scanning of the first and second light sensors by the scanning beam. The controller is configured to perform an operation to calibrate the laser scanning systems when the time interval is equal to or greater than a first threshold value.