| 摘要 |
PURPOSE:To perform photo modulation of the quantity of detected infrared rays by a simple circuit by eliminating the need for a chopper by applying an infrared- ray detecting element with a modulated voltage. CONSTITUTION:Modulated-signal generator 3 generates a modulated voltage by a fixed frequency signal to charge an infrared-ray detecting element via capacitor 2 in each constant period. This charge is equivalent to Fig. A, so that it will be discharged through resistance Rs and the input impedance of FET 4. Since the amount of charge Q and capacity Cs of element 1 have relation of Vs=Q/Cs with across voltage Vs, a voltage in proportion to this discharged charge is developed. When infrared rays strike, the amount of generated charge DELTAQ can be obtained corresponding to the incident light energy. Therefore, voltage variation DELTAV of Vs(=Vs+DELTAV)=(Q+DELTAQ)/Cs can be obtained. The amount of incident infrared rays can be measured by knowing this voltage variation DELTAV. The modulated electric signal is voltage divided by the resistance or capacitor and then applied, so that the voltage across element 1 can be developed in proportion to the charge of element. |
