| 摘要 |
PROBLEM TO BE SOLVED: To obtain a high quality high gradation image by setting the time constant of the resistance and capacitor in a snubber circuit connected between first and second current output terminals such that the light quantity characteristics of an optical beam is projected downward by an image data. SOLUTION: A snubber circuit comprising a series connection of a resistor Rd 29 and a capacitor Cd 28 is connected between a first current output terminal 50 outputting the drive current of a laser diode 1 and a second current output terminal 60 outputting a current having a differential relationship with the drive current of the laser diode 1. The snubber circuit is a primary time constant circuit and the step response thereof is varied to 0.63 after a timeτ, to 0.86 after a time 2τ, to 0.95 after a time 3τ, to 0.98 after a time 4τand to 0.99 after a time 5τwhen a time constantτ=Rd.Cd. Consequently, the snubber circuit time constant Td(=Rd.Cd) is set at Td=T1/5.
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