| 摘要 |
PROBLEM TO BE SOLVED: To provide a synchronous signal generator for enhancing a highly fine accuracy in an image-forming apparatus in which a plurality of semiconductor lasers are used. SOLUTION: A laser-selecting circuit 3 selects the first semiconductor laser 12. A laser emission control circuit 5 generates a laser control signal 6 for letting the first semiconductor laser 12 emit light on the basis of a laser selection signal 4. The first semiconductor laser 12 is driven to emit light by a first laser driver 11, and its optical output is received by a beam-detecting circuit 17 which in turn outputs a beam detection signal 18. A horizontal synchronous signal-accepting circuit 19 generates a timing for prohibiting and permitting accepting the beam detection signal 18, and a horizontal synchronous signal- generating circuit 8 outputs a horizontal synchronous signal 9. Similarly, the second semiconductor laser 14 is selected and the horizontal synchronous signal 9 is generated. The timing for permitting detecting a next beam is determined by a ratio based on an output cycle of two beam detection signals detected immediately before.
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