Light quantity detection device and light quantity detection method

Abstract

Light quantity detection device with a light detector (3) for detecting light and for outputting a detection signal; an amplifier (5) for amplifying the detection signal of the light detector (3), wherein the detection signal contains noise signals; an A / D converter (6) for A / D conversion of the detection signal amplified by the amplifier (5); a threshold processing circuit unit (7) for performing threshold processing on the detection signal converted by the A / D converter (6) using a threshold (V th ); and with a photon count calculation circuit unit (8) for calculating the intensity of the light or the number of photons incident on the light detector (3) from the detection signal which has been subjected to threshold processing by the threshold processing circuit unit (7), wherein the photon count calculation circuit unit (8) calculates the intensity of the light or the number of photons incident on the light detector (3) on the basis of an area of ​​the signal waveform of the detection signal which has been subjected to threshold processing by the threshold processing circuit unit (7), characterized by the fact that the threshold processing circuit unit (7) a signal with a level that is equal to or less than the threshold (V) in the A / D converted detection signals th ), by a given reference value (V base ) replaced and the reference value (V base ) outputs to the photon count calculation circuit unit (8), where the reference value (V base ) smaller than the threshold (V th ) the threshold processing is and from the mean of the noise signals is determined.

Description

Technical field

[0001] The present invention relates to a method and a device for detecting the amount of light in a device for detecting the light emitted by a sample, a device for detecting the light transmitted or scattered when a sample is irradiated with light, or a device for detecting the fluorescence of a sample when the sample is irradiated with light. State of the art

[0002] In the fields of industrial materials, environmental science, pharmaceuticals, and biology, light is often shone onto a sample, and the transmitted light, scattered light, or fluorescence produced on the sample during irradiation is detected and measured using a light meter to analyze the sample's components. In semiconductor testing devices, light is shone onto a semiconductor wafer, and the transmitted or reflected light is measured to examine the circuits formed on the wafer or to detect foreign matter. To identify airborne aerosols, the air is irradiated with a laser, and the scattered light is measured. For accurate analysis of small light levels, the light meter's detection range (dynamic range) must be extended.

[0003] In the state of the art, the light quantity detection method comprises an analog measurement method with a recording of the intensity of the output signal of a light detector when light falls on the detector and a photon counting method with a counting of the output pulses that are generated when photons fall on the light detector.

[0004] Based on the Fig. Section 2 describes the light quantity detection device for the analog measurement method. The light quantity detection device for the analog measurement method is designed such that it integrates the output signal 32 of an analog light detector 31 within a predetermined time in an integrator 51, converts the output signal 52 of the integrator into a digital signal in an A / D converter 6, and processes the digital signal arithmetically in a CPU 90.

[0005] In the Fig. Figure 2 shows the waveforms of the detector output signal 32 and the integrator output signal 52. When the amount of light incident on the light detector 31 is large (case a for a large amount of light), the output signal 32 of the light detector is a strong detector output signal during the light incident. The output signal 52 of the integrator increases during the light incident, and the integration result is recorded by the A / D converter 6.

[0006] Patent document 1 (Japanese patent application publication JP H05-264352A) describes a method for changing the integration time according to the amount of light, whereby the integration time is increased when the amount of light is low. The output value of the integrator is therefore significantly higher when light is present than when no light is present, thus improving the measurement accuracy.

[0007] As a further method for solving the problem of deteriorating measurement accuracy in low light, patent document 2(JP 2008 - 249 694 A) describes a method for preventing the accumulation of noise signals below a threshold by replacing the signals below the threshold with a reference value and lowering the lower limit for the measurable amount of light in a time-of-flight mass spectrometer.

[0008] Based on the Fig. Section 3 describes the light quantity detection device for the photon counting method. The light quantity detection device for the photon counting method is designed such that it compares the output signal 32 of the photon-counting light detector 3 with a threshold value using a comparator 61 and outputs a 1 if the threshold value is reached or exceeded, or a 0 if the threshold value is not reached. The number of pulses of the comparator's output signal 62 for signal 1 is counted by a counter 63, and the counted number of pulses is processed arithmetically in the CPU 90.

[0009] In the Fig. Figure 3 shows the waveforms of the detector output signal 32 and the comparator output signal 62. If the amount of light incident on the light detector 3 is small (case a for a small amount of light), the output signal pulses generated when photons strike the light detector can be detected with high accuracy.

[0010] Patent document 3 (Japanese patent application publication JP H09-178852A) describes a method for measuring the amount of light using the photon counting method at low light levels and the analog measurement method at high light levels by simultaneously applying the analog measurement method and the photon counting method. The amount of light can be measured over a wide dynamic range by switching between the measurement methods according to the light level. List of cited publications Patent publications Patent Publication 1: Japanese Patent Application Publication No. JP H05 - 26 4352 A Patent Publication 2: JP 2008 - 249 694 A Patent Publication 3: JP H09 - 178 852 A

[0011] Document JP 2006 - 300 728 A discloses a light quantity detection device according to the preamble of claim 1. Further prior art is disclosed in documents US 6 960 771 B1 and JP H11 - 37 850 A. Summary of the invention: Technical problem

[0012] In the known light quantity detection device for the analog measurement method, the signal-to-noise ratio of the light detector's output signal deteriorates as the amount of light incident on the detector decreases (in case b, a small amount of light). Since the noise component is also integrated, the difference in the integrator's output signal between the case where no light is incident during the integration time and the case where only weak light is incident becomes small, and the measurement accuracy decreases.

[0013] In both the method for changing the integration time according to the amount of light according to patent document 1 (Japanese patent application publication JP H05 - 26 4352 A) and the method for preventing an accumulation of noise signals below a threshold and lowering the lower limit for the measurable amount of light according to patent document 2 (Japanese patent application publication JP 2008 – 249 694 A), the improvement in measurement accuracy at low light levels is limited by the characteristic of the analog measurement method that the signal-to-noise ratio of the detector's output signal worsens at low light levels in both methods.

[0014] When the amount of light is measured using the photon counting method, photons continuously strike the light detector at intervals smaller than the pulse width of the light detector's output signal for a single photon (in the Fig. 3 in case b, a large amount of light). As a result, the output signal of the light detector becomes a superposition signal of pulses for the photons. In the Fig. Figure 3 in b shows an example of the waveform in the case of strong incident light, where three photons arrive shortly before and shortly after time t1. The output signal of the light detector becomes a single large pulse in which the three photons overlap, and the output signal of the comparator is also a single pulse. As a result, photons are lost during counting, and the exact number of photons cannot be determined.

[0015] The method described in patent document 3 requires two light detection systems: one for the analog measurement method and one for the photon counting method, resulting in a rather large apparatus. Furthermore, the analog measurement method and the photon counting method differ in the linearity of the output signal to the incident light quantity.

[0016] One requirement for the light quantity detection device is that the amount of light can be detected over a wide dynamic range, from a low amount of light to a high amount of light.

[0017] The present invention therefore comprises a photon counting light quantity detection method with a large dynamic range to solve the problem that, in the photon counting method for detecting small quantities of light, photons are lost and the measurement accuracy decreases as the quantity of light increases. Solution to the problem

[0018] To solve the problem, the invention proposes a light quantity detection device with the features of claim 1 and a light quantity detection method with the features of claim 7. Advantageous effects of the invention

[0019] With the present invention it is possible to create a light quantity detection device that can detect light in a wide dynamic range from small light quantities to large light quantities. Brief description of the drawings Fig. Figure 1 is a schematic block diagram of the structure of a light quantity detection device in a first embodiment of the present invention. Fig. Figure 2 is a schematic representation of the structure and features of a light quantity detection circuit for the analog measurement method in the state of the art. Fig. Figure 3 is a schematic representation of the structure and features of a light quantity detection circuit for the photon counting method in the state of the art. Fig. Figure 4 is a representation of the waveform of the output signal of a photon counting detector when a photon is incident. Fig. Figure 5 is a representation of the waveform of the output signal of the photon counting detector when two photons are incident. Fig. Figure 6A is a waveform representation to illustrate the deterioration of accuracy due to a noise signal. Fig. Figure 6B is a waveform representation to illustrate the threshold processing in the present invention. Fig. Figure 7 is a view of the screen of a graphical user interface for entering a setting value for threshold processing in the first embodiment of the present invention. Fig. Figure 8 is a representation of the temporary change in the intensity of the detection signal in a method for determining a threshold and a reference value and a graphical representation of the intensity distribution of the detection signal in the first embodiment of the present invention. Fig. Figure 9 shows the temporary change in the intensity of the noise signal in a method for determining the threshold from the maximum value of the noise in the first embodiment of the present invention. Fig. Figure 10 is a representation of the temporary change in the intensity of the noise signal in a method for determining the reference value by removing a signal with strong noise in the first embodiment of the present invention. Fig. Figure 11 is a flowchart for the steps in determining the threshold and reference value in the first embodiment of the present invention. Fig. Figure 12 is a schematic block diagram of the structure of the light quantity detection device in a second embodiment of the present invention. Fig. Figure 13 is a flowchart for the steps involved in adjusting the gain of an amplifier in the second embodiment of the present invention. Fig. Figure 14 shows (a) a signal waveform and (b) a representation of the temporary change in gain in a method for changing the gain of the amplifier according to the intensity of the signal in the second embodiment of the present invention. Fig. Figure 15 is a schematic block diagram of the structure of the light quantity detection device in a third embodiment of the present invention. Fig. Figure 16 is a schematic block diagram of the structure of the light quantity detection device in a fourth embodiment of the present invention. Fig. Figure 17 is a representation of the temporary change in the intensity of the detection signal in a method for determining a reference value from a stored detection signal in the fourth embodiment of the present invention. Description of embodiments

[0020] The following section explains embodiments of the present invention in more detail with reference to the accompanying drawings. In all drawings describing the embodiments, the same reference numerals essentially always refer to the same components, and repetition of these descriptions is avoided. First embodiment

[0021] The Fig. Figure 1 shows the construction of a light quantity detection device in a first embodiment of the present invention.

[0022] The light quantity detection device of the present invention comprises a light source 1 for irradiating a sample 2, a photon-counting type light detector 3 for detecting the light transmitted or reflected by the sample or the fluorescence produced on the sample during irradiation, an A / D conversion signal acquisition circuit 4 for converting the output signal of the photon-counting light detector 3 into a digital signal and processing the digital signal, a CPU 90 for controlling the light quantity detection device, such as the A / D conversion signal acquisition circuit 4 and the like, and an input / output device 91 such as a keyboard or a mouse or a display device.

[0023] The A / D conversion signal acquisition circuit 4 includes an amplifier 5 for amplifying the acquisition signal, an A / D converter 6 for converting the amplified acquisition signal into a digital signal, a threshold processing circuit 7 for replacing the acquisition signal undergoing A / D conversion with a reference value when the acquisition signal undergoing A / D conversion is equal to or less than a threshold value, and a photon count calculation circuit 8 for calculating the number of photons or the amount of light falling on the light detector from the area of ​​the signal waveform of the acquisition signal undergoing threshold processing.

[0024] The photon counting light detector 3 amplifies the electrons generated by the photons falling on the light detector and outputs the detection signal as a current pulse. Fig. Figure 4 shows a simulated detector output waveform with a pulse width t PW, which is generated by the photon counting light detector 3 as a detection signal when a photon falls on the photon counting light detector 3 at time t1. If several photons fall, the detection signal takes on a waveform in which the output pulses of the individual photons are superimposed.

[0025] Based on the Fig. Section 5 describes an example of the superimposed waveform resulting from the incident of multiple photons. The pulse width of the output signal pulse of a photon is denoted by t. PW The waveform 501 represents the detector output waveform when the interval from t1 to t2 is smaller than the pulse width t. PW , two photons are incident, with the pulse width increasing compared to pulse waveforms 501a and 501b when one photon is incident at a time. The peak value depends on the time interval in which the two photons are incident. In the case of the Fig. In the example shown, waveform 501 has a rising peak value. Waveform 502 represents the detector output waveform when two photons arrive simultaneously at time t3, with a pulse width t. PW The waveform is the same as waveform 502a for the incidence of a photon, but the height value of the waveform is twice that of waveform 502a for the incidence of a photon.

[0026] Regarding the area of ​​the output waveform when multiple photons are superimposed, the area of ​​the waveform increases proportionally to the number of incident photons. Therefore, by determining the area of ​​the waveform of the detection signal, the number of photons can be accurately determined even when multiple pulses superimpose due to an increase in the amount of light. In the case described in the Fig. In the example shown, the two waveforms 501 and 502 have the same area, since two photons are incident in each case and the detection signal consists of two pulses in both waveform 501 and waveform 502.

[0027] As in the Fig. As shown in Figure 6A, however, the accuracy decreases due to the noise signals contained in the acquisition signal if only the area of ​​the acquisition signal waveform is evaluated. As shown in the Fig. As shown in Figure 6B, the influence of noise can therefore be eliminated by replacing the noise signals that are equal to or less than a threshold value with a reference value. As a result, the area of ​​the detection signal can be accurately determined at low light levels and with a small number of pulses, thus improving accuracy.

[0028] The threshold for threshold processing in threshold processing circuit 7 and the reference value are set on a GUI screen 92 (GUI: Graphical User Interface) for setting the threshold processing, which is located in the Fig. Figure 7 is shown. On the GUI screen 92, a threshold input field 93 for entering the threshold value and a reference value input field 84 are displayed.

[0029] Alternatively, the threshold and reference values ​​can also be derived from the measurement result. Since the noise signal removed by threshold processing is a signal output by the detector when no light falls on it, the threshold and reference values ​​can be determined in advance from the noise signal output by the detector when no light falls on it. Fig. Figure 8 shows an example. First, the noise signal is recorded when no light is incident, and the mean value m and the spread σ are calculated. The threshold V th For threshold processing, V is calculated from the mean m and the spread σ. th = m + 30 determined. The reference value V base becomes V base = m is determined from the mean value m of the noise signal. However, the threshold and the reference value can also be determined by another method based on the mean value and the spread. Alternatively, as in the Fig. Figure 9 shows that the threshold and the reference value can also be determined from the maximum value of the noise during the acquisition period of the noise signal without incident light. Furthermore, the reference value can be determined as the mean value, etc., of a signal from which a strong noise signal exceeding a noise threshold has been removed. This is to suppress errors in calculating the reference value due to high-intensity noise that unexpectedly occurs during the acquisition period for the noise signal without incident light, as described in the Fig. Figure 10 shows the noise threshold. The noise threshold can be the threshold V determined as above. th its value or an additional specified value.

[0030] In a light quantity detection device that measures the amount of light with a change in the measurement conditions, the threshold and the reference value can be determined using the sequence of steps shown in the flowchart of the Fig. Figure 11 is shown. First, the measurement conditions are changed (S101), and then the noise is recorded while no light is incident (S102), and the threshold V is determined. th and the reference value V base The amount of light at the sample is calculated (S103). Then, the amount of light at the sample is measured (S104) and, with reference to the measurement signal, the threshold value V calculated in step S103 is used. th and reference value V base The threshold processing is performed. Steps S101 to S104 are repeated until the measurement has been carried out under all measurement conditions (S105).

[0031] The photon counting circuit 8 calculates the number of photons or the amount of light incident on the light detector from the area of ​​the detection signal, which has undergone threshold processing in the threshold processing circuit 7. First, the waveform of the detection signal from the photon counting light detector 3 is pre-stored when a photon is incident, which the Fig. 4 corresponds to this. Then, the threshold set at the threshold processing circuit 7 is applied to determine and store the area of ​​the waveform for a photon that is equal to or greater than a threshold level. When the number of photons or the amount of light incident on the light detector is calculated from the area of ​​the detection signal, the detected number of photons is determined based on the stored area of ​​the waveform for a photon.

[0032] In the present embodiment, the area of ​​the waveform does not necessarily need to be converted into a number of photons or an amount of light; instead, the correlated area of ​​the waveform can also be used as the detection result for the amount of light.

[0033] The light shining on sample 2 or the light incident on the light detector can be visible light, infrared light, ultraviolet light, or radioactive radiation; the type of light is irrelevant. Sample 2 can be in a gaseous state, a liquid state, a solid state, and so on.

[0034] When the light-quantity detection method of the present invention is applied to a photometer, the transmitted light, the reflected light, or the fluorescence caused by the incident light on the sample is detected over a wide dynamic range. As a result, a component contained in the sample can be precisely analyzed by detecting the amount of light with a change in wavelength. The sample can be a semiconductor wafer or the like, in which case the present invention is applied to a semiconductor inspection device for detecting defects in the circuits formed on the wafer or for checking for foreign matter on the wafer, in order to detect smaller circuits or small foreign matter and the like.The present invention can also be applied to a light quantity detection device that does not contain a light source and that detects the light emitted by the sample, whereby a light quantity detection device with a large dynamic range is also obtained.

[0035] The light quantity detection method of the present invention provides a light quantity detection device for detecting the light quantity over a large dynamic range. This not only increases the dynamic range but also reduces the measurement time for small light quantities, since it is not necessary to perform long-term integration to improve the signal-to-noise ratio. Second embodiment

[0036] Based on the Fig. Section 12 now describes the construction of the light quantity detection device in a second embodiment of the present invention. The construction of the light quantity detection device of the second embodiment is essentially the same as that described in Section 12. Fig. 1 shown in the first embodiment and differs from the structure of the first embodiment in that the amplifier 5 of the Fig. 1 is replaced by a variable-gain amplifier 53. A feature of the present embodiment is that the detection signal of the photon-counting light detector 3 is amplified by the variable-gain amplifier 53. As a result, the output signal of the light detector is effectively A / D converted, independent of the intensity of the output signal, by adjusting the detection signal level supplied to the A / D converter 6. This allows the light quantity detection device to be obtained with a large dynamic range by using the variable-gain amplifier 53 together with the threshold processing circuit and the photon count calculation circuit.

[0037] In general, the detection sensitivity of a light detector depends strongly on the wavelength of the incident light. For example, if a photomultiplier tube is used as a light detector, the change within the visible light wavelength range is three orders of magnitude.

[0038] As a result, when using such a light detector, the amplifier's gain must be adjusted to the wavelength in order to detect the amount of light across a wide dynamic range. The amplifier's gain must also be adjusted when measuring samples with significantly different concentrations.

[0039] The gain of the variable amplifier 53 can be adjusted as described below. First, light is detected by the light detector at a predetermined gain, and it is determined whether the intensity of the A / D-converted detection signal is within the desired range. If the intensity of the A / D-converted detection signal is within the desired range, the measurement continues. If the intensity of the A / D-converted detection signal is outside the desired range, the gain is adjusted so that the signal intensity is within the desired range.

[0040] When the gain of the variable amplifier 53 is changed, the threshold and reference value for threshold processing are also changed accordingly. For example, if the gain is doubled, the threshold and reference value are also set to twice their original value. Alternatively, the threshold and reference value can also be measured again using the method described in the first embodiment when the gain is changed.

[0041] When the gain of the variable amplifier 53 is changed, the intensity of the acquisition signal undergoing A / D conversion also changes according to the gain, and thus the area of ​​the acquired waveform changes as well. As a result, the photon counting circuit calculates the area of ​​the waveform with a correction for the change in the intensity of the acquisition signal, which corresponds to the change in gain. Alternatively, the acquisition signal undergoing A / D conversion is corrected according to the gain of the amplifier and only then subjected to threshold processing.

[0042] In the light quantity detection device for measuring the amount of light with a change in the measurement conditions, as shown in the flowchart of the Fig. As shown in Figure 13, first the measurement conditions are changed (S111), and then the amplifier gain is adjusted (S112). When the gain is changed, the threshold and the reference value are also changed (S113).

[0043] In step S113, the threshold and reference values ​​are calculated and adjusted according to the changed gain, whereby the threshold and reference values ​​can be determined using current measurement data after the gain has been set. Then, in step S114, the amount of light is measured, and steps S111 to S114 are repeated until the measurement has been performed under all measurement conditions (S115).

[0044] If the intensity of the acquisition signal changes at a rate lower than the sampling rate of the A / D converter 6, the gain of the variable amplifier 53 can be adjusted depending on the change in signal intensity. The sequence of steps is described by the Fig. 14 described. First, as in Fig. Figure 14(a) shows that the waveform of the intensity of the detection signal divides the entire measurement period 121 into a number of measurement period units 122. The gain of the amplifier is adjusted for each measurement period unit as shown in Fig. Figure 14(b) shows a configuration where the amplifier gain during a subsequent n + 1 period is determined based on the intensity of the acquisition signal during the nth period. For example, if the intensity of the acquisition signal during the nth period is above a desired signal range, the gain in the subsequent n + 1 period is decreased, and if the acquisition signal is below the desired signal range, the gain in the subsequent period is increased. As described, the amplifier gain is thus changed depending on the intensity of the measured acquisition signal. With the change in gain, the threshold and the reference value for threshold processing are also changed depending on the amplifier gain. This corrects the intensity of the A / D-converted acquisition signal according to the gain.

[0045] If the intensity of the detection signal changes rapidly over time, the change in gain is delayed in relation to the signal intensity. When measuring a detection signal whose intensity changes at high speed, the signal is measured with a fixed gain after the amplifier gain has been appropriately set beforehand. This allows, for example, the measurement of the characteristics of a transient response that ends in a short time. Third embodiment

[0046] Based on the Fig. Section 15 now describes the construction of the light quantity detection device in a third embodiment of the present invention. A feature of the light quantity detection device of the third embodiment is that the detection signal of the photon counting light detector 3 is amplified by a logarithmic amplifier 54.

[0047] If the input voltage, output voltage, and gain of the logarithmic amplifier are denoted by Vi, Vo, and K, the output voltage of the logarithmic amplifier can be represented by the following equation: Vo=K⋅logVi .

[0048] By using the logarithmic amplifier, the large dynamic range of the light detector's detection signal can be reduced to a smaller dynamic range after output from the logarithmic amplifier. For example, if the light detector's detection signal has a dynamic range of over three orders of magnitude, the amplified signal can be reduced to a dynamic range three times greater. The detection signal with a large dynamic range can then be effectively converted by the A / D converter 6, and the light quantity detection device with a large dynamic range can be implemented by using the A / D converter 6 together with the threshold processing circuit and the photon count calculation circuit. Fourth embodiment

[0049] Based on the Fig. Section 16 now describes the construction of the light quantity detection device in a fourth embodiment of the present invention. A feature of the light quantity detection device of the fourth embodiment is that a memory 71 is provided for storing the detection signal converted into a digital signal by the A / D converter 6.

[0050] The detection signal from the photon counting light detector 3 is amplified by the amplifier 5 and converted from an analog signal to a digital signal by the A / D converter. The A / D-converted detection signal is stored in memory 71. After the measurements are complete, the signal stored in memory 71 is read out and subjected to threshold processing by the threshold processing circuit 7, and the number of photons or the amount of light incident on the light detector is calculated by the photon count calculation circuit 8.

[0051] The reference value for threshold processing can be determined using the method described in the first embodiment and compared with the stored detection signal based on the Fig.The method described in section 17 is used to determine the reference value. The drawing shows an example of the waveform of the acquisition signal stored in measurement period 121. To determine the reference value, signals equal to or less than the threshold are extracted from the stored signal, and the reference value is determined from the average of these signals and similar parameters. Subsequently, with reference to the waveform of the stored acquisition signal, the threshold processing is performed by replacing the signals equal to or less than the threshold with the reference value, and the number of photons or the amount of light is calculated by the photon count calculation circuit 8. The threshold can also be determined from the waveform of the stored acquisition signal.

[0052] The present invention has been described in more detail above on the basis of embodiments, but it is obvious that the present invention is not limited to the embodiments and that, without deviating from this, various modifications are possible. Industrial applicability

[0053] The present invention can be used in the fields of the environment, pharmaceuticals and biology in a method and in a device for detecting the amount of light in a device that detects the light emitted by a sample, or in a device that detects transmitted and scattered light when light is shone on the sample, or in a device that detects the fluorescence that occurs on the sample when it is irradiated with light.

[0054] In particular, the present invention can be used in a semiconductor testing device that irradiates a semiconductor wafer with light and measures the transmitted or reflected light in order to examine circuits on the semiconductor wafer or to check the wafer for foreign matter, and in a device for measuring aerosols suspended in the air by shining a laser beam into the air and measuring the scattered light. Reference symbol list 1 light source 2 Sample 3 photon counting light detector 31 Analog type light detector 32 Detector output signal 4 A / D conversion signal acquisition circuit 5 amplifiers 51 Integrator 52 Integrator output signal 53 amplifiers with variable gain 54 logarithmic amplifier 6 A / D converters 61 Comparator 62 Comparator output signal 63 counters 7 Threshold Processing Circuit 71 storage 8 photon count calculation circuit 90 CPU 91 Input / Output Device 92 GUI screen for setting threshold processing 93 Threshold input field 94 Reference value input field

Claims

[1] Light quantity detection device with a light detector (3) for detecting light and for outputting a detection signal; an amplifier (5) for amplifying the detection signal of the light detector (3), wherein the detection signal contains noise signals; an A / D converter (6) for A / D conversion of the detection signal amplified by the amplifier (5); a threshold processing circuit unit (7) for performing threshold processing on the detection signal converted by the A / D converter (6) using a threshold (V th ); and with a photon count calculation circuit unit (8) for calculating the intensity of the light or the number of photons incident on the light detector (3) from the detection signal which has been subjected to threshold processing by the threshold processing circuit unit (7), wherein the photon count calculation circuit unit (8) calculates the intensity of the light or the number of photons incident on the light detector (3) on the basis of an area of ​​the signal waveform of the detection signal which has been subjected to threshold processing by the threshold processing circuit unit (7), characterized by , that the threshold processing circuit unit (7) a signal with a level that is equal to or less than the threshold (V) in the A / D converted detection signals th ), by a given reference value (V base ) replaced and the reference value (V base ) outputs to the photon count calculation circuit unit (8), where the reference value (V base ) smaller than the threshold (V th ) the threshold processing is and from the mean of the noise signals is determined. [2] Light quantity detection device according to claim 1, wherein the photon count calculation circuit unit (8) calculates the number of photons incident on the light detector (3) on the basis of the ratio of the area of ​​the signal waveform of the detection signal, which has been subjected to threshold processing by the threshold processing circuit unit (7), to the area of ​​a reference signal waveform based on the area of ​​the signal waveform of a threshold (V th ) exceeding proportion of the waveforms of the signals that were detected after the A / D conversion of the detection signal by the A / D converter (6) when a photon hits the light detector (3). [3] Light quantity detection device according to claim 1, further comprising a threshold setting unit for setting the threshold value (V th ) for threshold processing by the threshold processing circuit unit (7) from the outside. [4] Light quantity detection device according to claim 1, further comprising a threshold setting unit for setting the threshold value (V th ) for the threshold processing of the A / converted detection signal by the threshold processing circuit unit (7) on the basis of the output signal of the light detector (3) when no light is incident. [5] Light quantity detection device according to claim 1, wherein the detector is a photon counting light detector (3). [6] Light quantity detection device according to claim 1, wherein the amplifier (5) is an amplification unit whose amplification is variable. [7] Light quantity measurement methods with a detection of light with a light detector (3) and output of a detection signal; an amplification of the detection signal from the light detector (3) to detect light, wherein the detection signal contains noise signals; an A / D conversion of the amplified detection signal; threshold processing of the A / D-converted acquisition signal using a predefined threshold (V) th ); and with a calculation of the intensity of the light or the number of photons incident on the light detector (3) from the detection signal which has been subjected to threshold processing, wherein the calculation of the intensity of the light or the number of photons incident on the light detector (3) is based on an area of ​​the signal waveform of the detection signal which has been subjected to threshold processing, characterized by , that The signal that has undergone threshold processing is a signal that is obtained by replacing a signal with a level that is equal to or less than the threshold (V) in the A / D-converted acquisition signals. tn ), by a given reference value (Vbase ) is obtained, where the reference value (V base ) smaller than the threshold (V th ) the threshold processing is and from the mean of the noise signals is determined. [8] Light quantity detection method according to claim 7, wherein the number of photons incident on the light detector (3) is calculated on the basis of the ratio of the area of ​​the signal waveform of the detection signal that has been subjected to threshold processing to the area of ​​a reference signal waveform that is based on the area of ​​the signal waveform of a threshold (V th ) exceeding proportion of the waveforms of the signals that were detected after the A / D conversion of the detection signal when a photon hits the light detector (3). [9] Light quantity detection method according to claim 7, wherein the predetermined threshold (V th ) is a threshold value that is entered from the outside. [10] Light quantity detection method according to claim 7, wherein the predetermined threshold value (V th ) is a threshold value based on the output signal that is given when the light detector (3) does not detect any light. [11] Light quantity detection method according to claim 7, wherein the light detector (3) is a photon counting light detector, wherein the intensity of the light or the number of photons falling on the photon counting light detector is calculated. [12] Light quantity detection method according to claim 7, wherein the detection signal of the light detector (3) is amplified by an amplifier (5) whose amplification is variable.

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