| 摘要 |
PURPOSE: To reduce noise of a photodetecting circuit by connecting a capacitor, related to a photodiode of low band width, to a charge amplifier with a transfer switch in between, so that the noise caused by the transfer switch is separated. CONSTITUTION: An incident light 108 is converted into an electronic measurement value which can be read with a microprocessor 100. Each pixel of a photodiode array(PDA) 80 is connected to a charge amplifier 80 of low band width with the use of a series of transfer switches 116. A restriction is applied to kTC noise which is related to the closed transfer switch 116 while an image charge in a photodiode capacitor 114 is measured, and kTC noise which is related to the opened transfer switch 116 is made to respond while a noise charge is measured. Two times of reading and subtraction technique for each photodiode are used for each cycle time of the PDA 80, so that noise of a photodetecting circuit is reduced. |
