Patent ID: 8017901
Filing Date: 2011-09-13
Classification: G01J,H01L,H04N

Abstract:
1. A photodetecting device comprising: a photodiode for generating electric charge of an amount according to an intensity of incident light; a switch for the photodiode, one end of the switch being connected to the photodiode; an integrating circuit connected with the other end of the switch for the photodiode, for accumulating an electric charge generated by the photodiode and input through the switch for the photodiode and outputting a voltage value according to an amount of the accumulated electric charge; and a noise removing circuit including an amplifier having first and second input terminals and first and second output terminals, first, second, third, and fourth switches, and first, second, third, and fourth capacitors, wherein one end of each of the first and second switches is connected to an output terminal of the integrating circuit, the other end of the first switch is connected to one end of the first capacitor, the other end of the second switch is connected to one end of the second capacitor, the other end of the first capacitor is connected to the first input terminal of the amplifier, the other end of the second capacitor is connected to the second input terminal of the amplifier, the third switch and the third capacitor are provided in parallel between the first input terminal of the amplifier and the first output terminal of the amplifier, and the fourth switch and the fourth capacitor are provided in parallel between the second input terminal of the amplifier and the second output terminal of the amplifier, said noise removing circuit for outputting a signal value according a difference between a voltage value that is output from the integrating circuit at a predetermined time and a voltage value that is output from the integrating circuit after the predetermined time by switching open and closed states of the first to fourth switches.