| 摘要 |
PROBLEM TO BE SOLVED: To reduce mutual difference in emission time relative to a light volume instruction value even under a required light volume that is different from a designed specification with a required light volume specified.SOLUTION: At an emission instruction value comparison part 275, a MOSFET 272B with low output impedance is selected in the case of an average value A>a threshold X, or a MOSFET 272A with high output impedance is selected in the case of an average value≤a threshold X. That is, emission time of which the average value is larger than the threshold X is set at a designed specification under a condition where the required light volume is relatively large. Therefore, the MOSFET 272B with low output impedance is selected. In contrast, in order to apply emission time of which the average value A is less than the threshold X to an image forming part of a category with the required light volume relatively small, the light volume is reduced by reducing a drive current, and the emission time is proportionately increased. Therefore, the MOSFET 272A with high output impedance is selected. |
