| 摘要 |
An optical scanning device is comprised of a light source unit, a rotating polygon mirror, an f theta lens, a photosensitive drum, a synchronization signal generating circuit 10, etc. Synchronization signal generating circuit 10 has a photodiode 6, and a resonance circuit 31, comprised of a parallel circuit of coil 32, capacitor 33, and resistor 34, is connected to photodiode 6 as its load circuit. An amplifier 35 is connected to the junction of photodiode 6 and resonance circuit 31, a capacitor 36 is connected to the output side of amplifier 35, and the other end of capacitor 36 is connected to the positive input terminal of comparator 38. A reference voltage generator 39 of variable reference voltage is connected to the negative input terminal of comparator 38 and a reference voltage is applied from this reference voltage generator 39.
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