| 摘要 |
PURPOSE:To eliminate the need for gain adjustment to the output level of photodiodes, to easily and automatically set the target values corresponding to the individual characteristics of the photodiodes, to cancel the fluctuation in the characteristics of light emitting diodes and the influence of the temp. characteristics thereof, and to easily and automatically set limit values at optimum levels. CONSTITUTION:The output signal of the photodiode 1 corresponding to the light emission output of the light emitting diode 20 at the time of an optimum writing level is detected and is stored into a memory 4. An offset OFS is added to data DT 11 formed in accordance with the output signal of the photodiode 1 obtd. at every execution of writing, by which the limit value of the driving current (i) of the light emitting diode 20 is set. |
