Light intensity controlling apparatus and image forming apparatus

Abstract

In an image forming apparatus in which scanning of a laser beam modulated by an image signal is performed, and a laser is forced to be turned on in a non-image period in line scanning of the laser beam, an interrupt request is issued to a microcomputer in response to a forced turn-on signal. In a routine that is called in response to the interrupt request, the level of the forced turn-on signal is checked. If no forced turn-on signal is generated, then acquisition of a detected laser beam intensity signal is inhibited. This ensures that the acquisition of the laser beam intensity signal is performed only when the laser is in a normal turn-on state. If a forced turn-on signal is generated, the laser beam intensity signal is acquired, and the laser beam intensity is adjusted according to the acquired value of the laser beam intensity signal. The acquisition of the detected laser beam intensity signal is performed a plurality of times (four times, for example), and the average of the acquired values is calculated thereby producing a normalized detected laser beam intensity for use in the laser beam intensity control. Furthermore, in the above-described routine, after the completion of measuring elapse of a predetermined time, the acquisition of the laser beam intensity signal is performed.