| 摘要 |
PURPOSE:To obtain highly accurate linearity free from temperature dependency by constituting the titled instrument of a photoelectric converter, a means for accumulating a signal generated in the converter at the time of photometry as charge and a means for detecting illumination based on time required until voltage generated by accumulated charge exceeds a reference voltage. CONSTITUTION:When photometry is started at a time t1, the level of a control signal VP is turned to 'L' by a comparing means 14, a switch element 13 is turned off and current IPD corresponding to the photodetecting variable of a photodiode 10 is accumulated in a capacitor 12 as charge in the elapse of time. Since the quantity of charge is proportional to the product of the current IPD and the time passed, the output voltage V0 of an operational amplifier 11 is dropped from a voltage Valpha with a fixed inclination. When the voltage V0 exceeds the reference voltage VR at a time t2, a detecting signal SC is generated and a voltage VT at a point of time t3 after the passage of a prescribed time T0A can be measured. Consequently, illumination corresponding to the current IPD is calculated and an output signal S0 is outputted.
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