| 摘要 |
PURPOSE:To detect the change of a color without using a logarithmic conversion circuit by connecting resistors converting the output current of plural photodetecting elements having different wavelength sensitivities into an equivalent voltage under a certain reference state of color change of an object to be detected to these photodetecting elements. CONSTITUTION:Respective resistors R1, R2 are connected to anodes of two photodiodes PD1, PD2 having different wavelength sensitivities and voltages generated in respective resistors R1, R2 are inputted to a comparator CM. Voltage V1 for expanding a dynamic range is applied to a common cathode of the photodiodes PD1, PD2. In this case, the values of the resistors R1, R2 are selected so that the output current ISC1, ISC2 of the diode PD1, PD2 are converted into an equivalent voltage under a certain reference state of color change of the object to be detected. e.g. color change of flame or chemical reaction. Thus, the color change of the object to be detected can be detected without using a logarithmic conversion circuit ordinally used. |
