| 摘要 |
PURPOSE:To simplify the constitution of an image forming device by detecting the quantities of plural scanning light beams of an optical system individually on a time-division basis by sensor parts which are less than the scanning light beams, and performing light emission control over light sources individually. CONSTITUTION:A semiconductor laser oscillator 302 is provided with one photodiode 56 which detects the quantity of laser beams, and the detection result is used to hold the quantities of light emitted by laser diodes 50 and 51 constant. The laser diodes 50 and 51 output 1st and 2nd laser beams 309 and 310 for the recording and exposure of data and 3rd and 4th laser light beam 55a and 55b for monitoring to left. Then a beam light detector detects only one of the two laser beams 309 and 310 scanned by a rotary motor scanning unit 212. Thus, the quantities of the two laser beams are detected by one beam detecting circuit individually on a time-division basis to perform the light emission control over the respective laser diodes, so the constitution is simplified.
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