| 摘要 |
PURPOSE:To improve the reliability of the titled printer and to reduce the number of maintenance attended with the service life of a laser beam oscillator by providing plural laser beam oscillators, an optical system unifying each optical axis into one optical axis and a switching means in case of a fault. CONSTITUTION:The optical axis of each light beam from the 1st semiconductor laser 8 and a spare semiconductor laser 9 is unified into one optical axis by an afocal optical system 14. When a fault takes place in the laser 8 in operation and a monitor current is decreased abnormally attended therewith, the fault is detected by a monitor current fault detection circuit 15 and the drive is switched to the laser 9 via a drive changeover circuit 17. In this case, the optical beam of the laser 9 changed over is changed into the optical axis the same direction as the optical axis of the optical beam of the faulty laser beam oscillator. Thus, the printer is not stopped in case of the fault to improve the reliability of the printer and the number of maintenance attended with the service life of the laser beam oscillator is decreased. |
