| 摘要 |
PURPOSE:To measure the illuminance of incident light as well as color temperature by providing a circuit which outputs a signal proportional to the illuminance of the incident light to a color temperature detecting device which uses a color sensor. CONSTITUTION:The base-emitter voltage VBE1 of a transistor TrQ1 is proportional to the short-circuit current ISC1 of a photodiode PD1 and the current is proportional to the illuminance of incident on the PD1, so the illuminance of incidence on the PD1 is known from the voltage VBE1. Further, a voltage Vo' outputted through operational amplifiers 4 and 5 which amplifies the VBE1 is proportional to the logarithmic value of the illuminance of incidence on the PD1. The circuit including the PDs 1 and 2, operational amplifiers 1, 2 and 3, and Trs Q1 and Q2, on the other hand, forms a color temperature detecting circuit. Therefore, the illuminance of the incident light is measured as well as the color temperature. |
