| 摘要 |
PURPOSE:To enable the execution of measurement of light with high precision and in a short time, by using a photodiode for monitoring commonly as a photodetector for measuring a light spot. CONSTITUTION:Monitor photodiodes 2A and 2B for controlling a charge accumulation time in a photodiode array 3 for detecting the focus are used commonly as photodetectors for measuring a light spot. The diodes 2A and 2B used being equal in size and characteristics, the diode 2B is shielded from a light completely by an aluminum coating or the like, and a dark current component is removed by taking a difference between the respective outputs of the diodes 2A and 2B. When a light spot measuring switch 20B is turned ON, a CCD driver 11 and an amplification rate control circuit 10 are initialized, a monitor output signal is counted in CPU 13, the operation of the circuit 10 is switched over, and the light spot measurement is executed. |
