| 摘要 |
PROBLEM TO BE SOLVED: To form an image which is not changed from the image obtained before fault, even when several laser beams become faulty by selecting a laser light source to be used according to the faulty laser light source and increasing the scanning speed of the laser beam and the frequency of an image signal for turning on the laser light source according to the number of selected lasers. SOLUTION: For a detection circuit, the drive currents of the respective lasers are always compared with a specified value. When the drive current of the laser is more increased than the specified value, it is recognized that the laser becomes faulty. When several lasers from among multi-beam lasers 26 become faulty, the logical value of a fault detection signal 103 corresponding to the faulty laser is set to 'true' with respect to a control part 34. Since the control part 34 is constituted so as to always execute communication with an image signal generation part 38, detailed information related on the fault is transmitted to an image development circuit. Then, the laser to be used is decided according to the arrangement of the faulty lasers and the number of faulty lasers. According to the number of laser light sources to be used, the scanning speed of the laser beam in a main scanning direction is increased, and the turning-on cycle of the image signal for turning on the laser is lowered. |
