| 摘要 |
PROBLEM TO BE SOLVED: To realize the high speed processing of an APC without employing a CPU, which performs high speed processing by a method wherein a controlling means being constituted by combining summing and subtracting circuits, which follow the voltage obtained with an photo-electric converting means with a normal voltage, which a sample holding circuit is equipped. SOLUTION: A voltage holding synchronizing circuit 10, to which an LD driving start signal sent from a CPU 12 and a light quantity setting start signal sent from a LD light emitting signal generating circuit 9 are inputted, outputs a reset signal to a first summing circuit 3 and a holding signal to a voltage folding outputting circuit 4. Further, a subtracting circuit 2 subtracts a PD normal voltage from a PD voltage, which is obtained by converting the LD light sent from a PD(photodiode) circuit 7 to an analog voltage so as to output the resultant difference voltage to the first summing circuit 3. Furthermore, the first summing circuit 3 sums the holding voltage sent from the voltage holding outputting circuit 4 with the difference voltage sent from the subtracting circuit 2 so as to output resultant added voltage to the voltage holding outputting circuit 4. |
