| 摘要 |
PROBLEM TO BE SOLVED: To provide a laser light quantity controlling apparatus which can increase the APC precision, and can shorten the response time of the APC. SOLUTION: In a laser driving circuit which is installed in an optical scanning unit, a forcible light emitting signal generating circuit 59 makes a semiconductor laser emit light by a constant current at a preset LD driving current value right after an execution indication of a light amount control. A shift registor 51 makes an AD output signal delayed by one cycle from a SYSCLK 16, and outputs the AD output signal which has been delayed by one cycle to a differential value calculating circuit 50 as a shift register output 52. The differential value calculating circuit 50 calculates a differential value 653 between the AD output signal 23 and the shift register output 52 by a time series. When the differential value 53 is not more than a stable judgement value 55, a current latch is placed under a bypass state, and the light amount control is started. COPYRIGHT: (C)2008,JPO&INPIT
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