| 摘要 |
PROBLEM TO BE SOLVED: To provide an imaging apparatus in which the quantity of light of a laser light source for forming an image by forming an electrostatic latent image on a photosensitive body can be regulated easily and automatically with high accuracy. SOLUTION: In an APC circuit 20, a control circuit 25 turns a switch SW1 or SW2 selectively in sampling mode to charge one of capacitors C1 and C1 from a constant current source 26 for charging through a switch circuit 28. In holding mode, the control circuit 25 turns the switches SW1 and SW2 off and an error amplifier 29 amplifies the error between an input voltage V3 from the capacitor C1, C2 and a reference voltage Vref3 to increase/decrease the collector current of a transistor Tr1 thus keeping the quantity of light of an LD3 at a constant level. When a quantity of light switching signal IN2 is varied in the sampling mode, an edge detection pulse generating circuit 30 delivers a switching signal IN2a becoming high for a short predetermined time to a switch circuit 24. The switch circuit 24 outputs a reference voltage Vref2 of '0' volt as the reference voltage Vrefb of a comparator 23 thus preventing over emission of the LD3 appropriately. |
