| 摘要 |
PROBLEM TO BE SOLVED: To control a quantity of light of an LD(laser diode) as an emission source by means of proper feedback by avoiding wrong detection by a PD(photodiode) having a rise time before showing a correct light quantity value. SOLUTION: A resistance R is set so as to obtain by a voltage Vm, an output current Im of the PD 2 which detects an emission quantity from the LD 1 controlled to be turned on in accordance with image signals for writing by scanning light beams. The voltage Vm is fed back to an LD control part 11. The resistance R is variable. The quantity of light can be adjusted by changing the R, and the R can meet LDs of different characteristics. The rise time before an output of the PD 2 is stabilized can be determined by adjusting a target voltage value set to the R and the LD control part 11. The rise time is determined so that the quantity of light can be properly controlled while the LD 1 for generating synchronous signals of the scanning light is turned on. |
