| 摘要 |
PURPOSE:To detect the wavelength of a certain incident beam of light based on a resistance value of a variable resistance, by limiting the resistance value so that the voltage across terminals of one of two photovoltaic cells will be zero with the incident light. CONSTITUTION:Photodiodes PD111 and 112 as photovoltaic cell are connected in series in the same polarity and resistances 121 and 122 show internal resistance of PDs 111 and 112. Fixed resistances 131 and 132 are connected to both ends of the PD111 and 112 and a variable resistance 14 is connected therebetween. When light is made incident into such a PD group, photocurrents DELTAi1 and DELTAi2 are generated in the PD111 and 112. Then, voltages DELTAV1 and DELTAV2 are generated between both the ends of the PD111 and PF112 according to the incident light wavelength, the resistance values R1 and R2 of fixed resistances 131 and 132 and the resistance value R3 of the variable resistance 14. Then, the resistance value R3 to zero the voltage DELTAV1 and the resistance value R3 to zero the voltage DELTAV2 according to the wavelength of the incident light are primarily determined by varying the resistance value R3 of the variable resistance. Thus, the wavelength of the incident light is detected by determining the resistance R3. |
