Signal processing circuit and signal processing method

Abstract

This invention provides a signal processing circuit that can improve the accuracy of light intensity measurement. [Solution] The signal processing circuit 3 includes an A / D converter 31 and a noise reduction circuit 32. The A / D converter 31 converts the electrical signal Va output from the photodetector 2 in response to the input of a photon into time-series data Da including a plurality of digital signal values. The noise reduction circuit 32 determines whether the difference between each of the plurality of digital signal values ​​and the previous digital signal value satisfies a threshold condition indicating the presence of a component based on the input of a photon. In a first period that does not contain a component based on the input of a photon, the noise reduction circuit 32 replaces each of the plurality of digital signal values ​​with a predetermined value. The noise reduction circuit 32 determines the first period based on the result of the determination.

Claims

1. An input terminal that receives an electrical signal output from a photodetector in response to a photon input, An analog-to-digital converter that converts the aforementioned electrical signal into time-series data including a plurality of digital signal values ​​having time intervals, A noise reduction unit that reduces noise components in the time-series data that are different from the components based on the photon input, Equipped with, The noise reduction unit is A determination unit determines whether the difference between each of the plurality of digital signal values ​​and the digital signal value preceding the digital signal value satisfies a threshold condition indicating the presence of a component based on the photon input. In a first period that does not include components based on the input of the photons, a substitution unit replaces each of the plurality of digital signal values ​​with a predetermined value, It has, The substitution unit is a signal processing circuit that determines the first period based on the determination result in the determination unit.

2. The signal processing circuit according to claim 1, wherein the threshold condition is that the difference value exceeds a predetermined threshold.

3. The signal processing circuit according to claim 1 or 2, wherein the difference value is the difference between the digital signal value and the digital signal value immediately preceding the digital signal value.

4. The signal processing circuit according to claim 1 or 2, wherein the predetermined value is a constant value.

5. An input step that inputs an electrical signal output from a photodetector in response to a photon input, The analog-to-digital conversion step converts the electrical signal into time-series data including a plurality of digital signal values ​​having time intervals, A noise reduction step that reduces noise components in the time-series data that are different from the components based on the photon input, Equipped with, The noise reduction step is, A determination step in which, for each of the plurality of digital signal values, a determination is made to determine whether the difference between the digital signal value and the digital signal value preceding the digital signal value satisfies a threshold condition indicating the presence of a component based on the photon input. A substitution step in which each of the plurality of digital signal values ​​is replaced with a predetermined value during a first period that does not include a component based on the input of the photon, It has, The substitution step is a signal processing method that determines the first period based on the determination result in the determination step.

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