| 摘要 |
PURPOSE:To eliminate the use of measurement of an oscillator output and to prevent print position shift in advance due to output reduction by using a detection signal of a beam detector so as to detect the reduction in a laser oscillator output. CONSTITUTION:When a power of a laser oscillator 1 is given as P1 and an output SiG IN of a beam detector 8 is larger than a reference voltage REF VOLT2, a timing signal SiG OUT and a power reduction detecting signal PWR ALM reach the state '1' being the presence of signal every time a laser beam scans a photosensitive body 6. On the other hand, the power of the oscillator 1 is decreased into P2 and the output SiG IN of the detector 8 is smaller than the reference voltage REF VOLT2, the power reduction detection signal PWR ALM continues the state '0' being the absence of signal. Thus, the power reduction of the oscillator 1 is detected without measuring the power of the oscillator 1 to prevent print position shift in advance. |
