WO2001035063A1

WO2001035063A1 - Apparatus for detecting luminous energy

Info

Publication number: WO2001035063A1
Application number: PCT/JP1999/006282
Authority: WO
Inventors: Takashi Koike; Toyoshi Ito
Original assignee: Hamamatsu Photonics K.K.
Priority date: 1998-05-12
Filing date: 1999-11-11
Publication date: 2001-05-17
Also published as: JP3863290B2; JPH11329340A

Abstract

The current signal from the anode (12) of a photomultiplier tube (10) is converted into a voltage signal (V1) by a current-to-voltage converter (30), and the voltage signal (V1) is compared with a reference signal (V0) by a comparator (50). When the received luminous energy is smaller than a predetermined quantity, the comparator (50) judges that the voltage signal (V1) is smaller than the reference voltage (V0), and a power source (60) applies a constant voltage to the photomultiplier tube (10). A signal processor (80) calculates the received luminous energy based on the voltage signal (V1). When the received luminous energy is greater than a predetermined quantity, the comparator (50) judges that the voltage signal (V1) is greater than the reference voltage (V0), and the power source (60) applies such a voltage to the photomultiplier tube (10) that the voltage signal (V1) approaches the reference voltage (V0). A buffer (70) amplifies the output signal from the comparator (50), and the signal processor (80) calculates the received luminous energy based on the voltage signal (V2) output from the buffer.

Description

Akitoda

Light intensity detector Technical field

The present invention relates to a light amount detection device that quantitatively detects the amount of received light. Background art

Conventionally, a light amount detection device using a photomultiplier tube has been known. In a conventional light quantity detection device, a constant voltage is applied to the photocathode of the photomultiplier tube and that of the dynode, and a photon is emitted from the photocathode in response to light incident on the photocathode, and the photoelectron is emitted. Is multiplied by the dynode to generate secondary electrons, and a current signal corresponding to the number of the secondary electrons is output from the anode electrode. Then, based on the magnitude of the current signal output from the anode electrode, the amount of light incident on the photocathode is quantitatively detected.

However, in this light quantity detection device, when excessive light is incident on the photocathode, the number of secondary electrons generated by multiplying photons by the dynode becomes excessive, which results in: ¾, photoelectron multiplication The tube and peripheral circuits may be destroyed by excessive current. Also, from this, it is necessary for the user to take care that excessive light does not enter the photomultiplier tube, so that handling is not easy, and the dynamic range of light amount detection is narrow. is there.

The light quantity detection device disclosed in Japanese Patent Publication No. 59-500018 was proposed to solve such a problem, and it was developed from an anode electrode of a photomultiplier tube. The voltage applied to each of the photocathode and the dynode of the photomultiplier tube is feedback-controlled so that the magnitude of the input current signal is constant, and based on the value of the applied voltage, the light incident on the photocathode is controlled. The quantity of light is detected quantitatively. And like this This prevents excessive current from flowing through the photomultiplier tube and peripheral circuits, avoids damage to the photomultiplier tube and peripheral circuits, and facilitates handling. Is trying to expand. Disclosure of the invention

However, in the light amount detection device disclosed in Japanese Unexamined Patent Publication No. 59-50018, although the excessive current does not flow, the adjustment range of the voltage applied to the photomultiplier tube is limited. It is necessary to be large, and when the incident light is extremely weak, the applied voltage becomes extremely high, and there is a risk that peripheral circuits may be destroyed due to the extremely high voltage. Therefore, even with this light amount detection device, the dynamic range of light amount detection is not sufficient.

The present invention has been made in order to solve the above problems, and has as its object to provide a light amount detection device having a wide dynamic range of light amount detection.

The light quantity measuring device according to the present invention comprises: (1) a photocathode that emits a number of photoelectrons according to the amount of received light, a dynode that multiplies the photoelectrons to generate secondary electrons, and a number of the secondary electrons. A photomultiplier tube having an anode electrode that outputs a current signal corresponding to the current, (2) a current-to-voltage converter that converts the current signal output from the anode into a voltage signal, and (3) a current-to-voltage converter. A comparator for comparing the output voltage signal with the reference voltage; and (4) applying a constant voltage to the photocathode of the photomultiplier tube, the dynode, and the like when the comparator determines that the voltage signal is smaller than the reference voltage. When it is determined that the voltage signal is equal to or higher than the reference voltage, a power supply unit that applies the applied voltage adjusted so that the voltage signal matches the reference voltage to each of the photocathode and the dynode of the photomultiplier tube. And (5) a signal processing unit that calculates a light reception amount based on the voltage signal when the voltage signal is smaller than the reference voltage, and calculates a light reception amount based on the applied voltage when the voltage signal is equal to or higher than the reference voltage. Features.

According to this light quantity measuring device, the current output from the anode electrode of the photomultiplier tube The signal is converted into a voltage signal by the current-voltage converter, and the voltage signal is compared with the reference signal by the comparator. When the amount of received light is smaller than a certain amount, the comparator determines that the voltage signal is smaller than the reference voltage, a constant voltage is applied from the power supply unit to the photocathode of the photomultiplier tube and the dynode, and the signal processing unit The received light amount is calculated based on the signal. On the other hand, when the amount of received light is equal to or more than a certain amount, the comparator determines that the voltage signal is equal to or higher than the reference voltage. The voltage is applied to the photocathode and the dynode of the intensifier, and the signal processing unit calculates the amount of received light based on the applied signal. Note that the applied voltage includes not only the applied voltage actually applied to the photomultiplier tube but also a voltage having a correlation with the applied voltage.

When the voltage signal is smaller than the reference voltage, the signal processor linearly converts the value of the voltage signal to calculate the amount of received light, and when the voltage signal is equal to or higher than the reference voltage, performs inverse logarithmic conversion on the value of the applied voltage to receive light. It is preferred to calculate the amount. In this case, the received light amount calculated by the signal processing unit has linearity with respect to the received light amount of the photocathode of the photomultiplier tube.

Further, it is preferable that the signal processing unit calculates the amount of received light by linearly correcting the value of the applied voltage after performing an inverse logarithmic conversion. In this case, the received light amount calculated by the signal processing unit has excellent linearity with respect to the received light S of the photocathode of the photomultiplier tube. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a configuration diagram showing a preferred embodiment of a light quantity detection device according to the present invention. FIG. 2A is a graph showing the relationship between the voltage signal V I output from the current-to-voltage converter and the amount of light received by the photomultiplier.

FIG. 2B is a graph showing the relationship between the voltage signal V2 output from the buffer unit and the amount of light received by the photomultiplier tube.

Figure 2C shows the signal V3 output from the signal processing unit and the light received by the photomultiplier tube. 6 is a graph showing a relationship between the light amount and the light amount.

FIG. 3 is a front chart showing the operation of the signal processing unit of the light amount detection device shown in FIG. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of a light amount detection device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a configuration diagram of a light quantity detection device 1 according to the present embodiment. The light amount detection device 1 includes a photomultiplier tube 10, a voltage divider 20, a current-voltage converter 30, a reference voltage generator 40, a comparator 50, a power supply 60, a buffer 70, and a signal processor 80.

The photomultiplier tube 10 includes a photocathode 11 that emits a number of photoelectrons according to the amount of incident light, and a dynode Dy, which multiplies the photoelectrons emitted from the photocathode 11 to generate secondary electrons. DDy ₉ and an anode electrode 12 that outputs a current signal according to the number of secondary electrons from the dynodes Dy, 〜Dy ₉ are provided in a vacuum vessel 13. When the photomultiplier tube 10 is applied with the photocathode 11, the dynodes Dy, to Dy ₉ , the anode 12, and a predetermined voltage applied thereto, the photomultiplier tube 10 responds to the light amount Photoelectrons are emitted from the photocathode 11, the photoelectrons are multiplied by dynodes D to Dy ₉ to generate secondary electrons, and a current signal is output according to the secondary electrons reaching the anode electrode 12. Current signal output from the anode electrode 12 are those according to the amount of light received, also those corresponding to the dynode Dy, multiplication factor i.e. the voltage applied by ~ D y _9.

The voltage dividing section 20 applies a predetermined voltage to the photomultiplier tube 10, and includes a resistor R21. To R 2 1 ₉ and a resistor R 22. Comprising a to R 22 _3. Resistor R2 1. To R 2 1 ₉ constitutes a resistor string connected in series. The first end of the resistor R 2 1 ₉ side of the resistor string is grounded, the resistor R 2 1 of the resistor string. The second end of the side is a resistor R22. Connected to the photocathode 11 via the Voltage is applied. The connection point between the resistor R 21 and the resistor R 21 i is connected to the dynode D _yi via the resistor R 22 i (i = l to 3). The connection point between the resistor and the resistor R2i is directly connected to the dynode Dy] (i = 4 to 9). The voltage divider 20 is a resistor R 21 connected in series. ：: Each potential generated by voltage division by R 2 _{19 is connected} to a resistor R 22. To R 2 2 ₃ via or directly to photocathode 1 1 and the dynode Dy of the photomultiplier tube 1 0, ~Dy ₉ which is applied to it.

When a current signal output from the anode electrode 12 of the photomultiplier tube 10 is input, the current-voltage converter 30 integrates the current signal, converts the current signal into a voltage signal, and outputs the voltage signal. It is. The current-voltage converter 30 includes a differential amplifier A31, resistors R31 to R34, and a capacitor C31. The resistor R33 and the resistor R34 connected in series are provided between the output terminal of the differential amplifier A31 and the ground terminal. The resistor R31 and the resistor R32 connected in series are provided between the first input terminal of the differential amplifier A31 and the connection point of the resistor R33 and the resistor R34. I have. The connection point between the resistor R31 and the resistor R32 is connected to the anode electrode 12 of the photomultiplier tube 10. The capacitor C31 is provided between the first input terminal and the output terminal of the differential amplifier A31. The input terminal of ^ 2 of the differential amplifier A31 is grounded. The voltage signal VI output from the current-voltage converter 30 is the potential of the output terminal of the differential amplifier A31. When the light incident on the photocathode 11 is extremely weak, the current signal output from the anode 12 becomes pulse-like, and the voltage applied to the photomultiplier 10 fluctuates. In this case, the ft current signal also fluctuates, but even in these cases, by appropriately determining the capacitance value of the capacitor C31, the integration time for converting the current signal to the voltage signal can be reduced. It is sufficient to eliminate the effects of fluctuations in the current signal.

The reference voltage generation section 40 generates a reference voltage V0 to be applied to the comparison section 50, and includes a zener diode D41. Zener diode D 4 1 Caso The anode terminal is connected to the power supply voltage Vcc via the resistor R2, and the anode terminal is grounded. The reference voltage V0 output from the reference voltage generator 40 is the potential of the force source terminal of the Zener diode D41.

The comparator 50 receives the voltage signal VI (potential of the output terminal of the differential amplifier A31) output from the current-voltage converter 30 via the resistor R1, and outputs the voltage signal VI from the reference voltage generator 40. It receives the reference voltage V0 (potential of the power source terminal of the Zener diode D41), amplifies the difference between these voltage values, and outputs the result. The comparison unit 50 includes a differential amplifier A51, a resistor R51, and a transistor Tr51. The first input terminal of the differential amplifier A5 1 is connected to the force source terminal of the zener diode D41, and the second input terminal is connected to the output of the differential amplifier A31 of the current-to-voltage converter 30. Connected to terminal via resistor R1. The base terminal of the transistor Tr 51 is connected to the output terminal of the differential amplifier A 51 via a resistor R 51, and the collector terminal is connected to a resistor R 2 and a variable resistor connected in series. It is connected to the power supply voltage Vcc via the resistor R3 and the resistor R4, and the emitter terminal is grounded. The output signal output from the comparing unit 50 is the potential of the collector terminal of the transistor Tr51, and is based on the difference between the voltage signal VI and the reference signal V0. That is, when the voltage signal VI becomes larger than the reference voltage V0, a voltage is applied from the differential amplifier A51 to the base terminal of the transistor Tr51, and the voltage between the collector terminal and the emitter terminal of the transistor Tr51 is changed. The resistance becomes low, and the output signal output from the comparison section 50 becomes small.

Upon receiving the output signal (potential of the collector terminal of the transistor Tr 51) output from the comparison unit 50, the power supply unit 60 supplies the output signal to both ends of the resistor string of the voltage division unit 20 based on the output signal. Generates voltage. The power supply unit 60 includes resistors R61 to R65, differential amplifier A61, capacitors C61 to C67, transistors Tr61 to Tr63, coil L61, diode D61. DD 64 and a transformer T 61. Since the oscillation frequency of the power supply section 60 is high, Because of the high power consumption, no excessive current flows and power consumption is low.

The resistor R61 and the resistor R62 are connected in series between the collector terminal of the transistor Tr51 of the comparing section 50 and the first end of the resistor row of the voltage dividing section 20. I have. A first input terminal of the differential amplifier A61 is connected to a connection point between the resistor R61 and the resistor R62, and a second input terminal is grounded. The collector terminal of the transistor Tr 61 is connected to the power supply voltage Vcc and grounded via the capacitor C 61, and the base terminal is connected to the output of the differential amplifier A 61 via the resistor R 63. Terminal, and the emitter terminal is grounded via a capacitor C62.

The primary side of transformer T61 consists of two coils. The first coil on the primary side has a first end connected to the collector terminal of the transistor Tr62 and a second end connected to the collector terminal of the transistor Tr63. The second coil on the primary side has a first end connected to the base terminal of the transistor Tr62 and a second end connected to the base terminal of the transistor Tr63. The first end of the first coil and the first end of the second coil are connected via a resistor R64. A point in the middle of the primary coil on the primary side is connected to the emitter terminal of the transistor Tr61 via the coil L61. The emitter terminals of the transistors Tr 62 and Tr 63 are grounded. The first end of the secondary coil of transformer T61 is connected in series with capacitors C63 and C64, and the other end is grounded and connected in series with capacitors C65 and C66. Have been. The anode terminal of the diode D61 is connected to the connection point of the capacitor C63 and the capacitor C64, and the cathode terminal is connected to the second end of the secondary coil of the transformer T61. The anode terminal of diode D62 is connected to the connection point of capacitors C65 and C66, and the cathode terminal is connected to the connection point of capacitors C63 and C64. C The anode terminal of the diode D 63 is connected to the capacitor C 64, and the cathode terminal is connected to the connection point of the capacitors C 65 and C 66. The anode terminal of diode D64 is connected to capacitor C66, and the cathode terminal is connected to capacitor C66. Connected to Densa C64. The second end of the secondary coil of transformer T61 is connected to capacitor C66 via capacitor C67 and resistor R65 in this order. Further, the connection point of the capacitor C 67 and the resistor R 65 is connected to the first end of the resistor row of the voltage divider 20.

The buffer unit 70 receives the output signal (potential of the collector terminal of the transistor Tr51) output from the comparison unit 50, amplifies the output signal, and outputs a voltage signal V2. The voltage signal V2 has a correlation with an applied voltage applied to the photomultiplier tube 10 from the power supply unit 60. The signal processing unit 80 receives the voltage signal VI output from the current-voltage conversion unit 30 and the voltage signal V2 output from the buffer unit 70, performs a predetermined calculation based on these, and performs photoelectron enhancement. The light intensity of the light received by the multiplier 10 is determined, and a signal V3 representing the amount of received light is output. The signal processing section 80 may process the voltage signals VI and V2, which are analog values, digitally after A / D conversion, or may process the voltage signals VI, V2, respectively, in an analog manner. Next, the operation of the light quantity detection device according to the present embodiment will be described. FIG. 2A is a graph showing the relationship between the voltage signal V I output from the dc voltage converter 30 and the amount of light received by the photomultiplier 10. FIG. 2B is a graph showing the relationship between the voltage signal V2 output from the buffer unit 70 and the light received by the photomultiplier 10. FIG. 2C is a graph showing the relationship between the signal V 3 output from the signal processing unit 80 and the amount of light received by the photomultiplier tube 10.

When the amount of light received by the photomultiplier tube 10 is small and equal to or less than a certain amount of received light P 0, the voltage applied from the light source unit 60 to the photomultiplier tube 10 via the voltage dividing unit 20 is It is constant. As the amount of light received by the photomultiplier tube 10 increases, the current signal output from the anode electrode 12 increases, and the voltage signal VI output from the current-voltage converter 30 increases. However, in a range smaller than the light reception amount P 0, the voltage signal VI output from the current-voltage converter 30 is smaller than the reference voltage V0 output from the reference voltage generator 40. This is detected by the comparing section 50, and the voltage applied by the power supply section 60 to the photomultiplier tube 10 via the voltage dividing section 20 is kept constant. In other words, in a range smaller than the light reception amount P 0, the larger the light reception amount, the larger the voltage signal VI output from the current-voltage converter 30, but the voltage signal V 2 output from the buffer 70 is constant. is there.

If the voltage applied by the power supply section 60 to the photomultiplier tube 10 is always constant, if the amount of light received by the photomultiplier tube 10 increases, the current signal output from the anode electrode 12 also increases. As a result, the voltage signal VI output from the current-voltage converter 30 also increases. When the amount of received light is equal to or greater than P0, the voltage signal VI is higher than the reference voltage V0. However, the fact is detected by the comparing section 50, and the voltage applied from the power supply section 60 to the photomultiplier tube 10 via the voltage dividing section 20 decreases, and the current output from the anode electrode 12 is reduced. The signal also decreases, and the voltage signal VI output from the current-voltage converter 30 also decreases to the reference voltage V0. As a result, the current signal output from the anode electrode 12 does not become larger than a certain value, and the voltage signal VI output from the current-voltage converter 30 does not become larger than the reference voltage V0.

Conversely, when the amount of light received by the photomultiplier tube 10 decreases in the range 1 above P 0, the current signal output from the anode electrode 12 decreases, and the current-to-voltage converter 30 outputs The voltage signal VI falls below the reference voltage V0. Then, the voltage is applied to the photomultiplier tube 10 by the power supply unit 60 via the voltage dividing unit 20, and the voltage is output from the current-voltage conversion unit 30. f Pressure signal VI rises. However, the voltage applied by the power supply section 60 to the photomultiplier tube 10 rises until the voltage signal VI output from the current / voltage conversion section 30 reaches the reference voltage V0. As a result, the current signal output from the anode electrode 12 does not become smaller than a fixed value, and the voltage signal V I output from the current-voltage converter 30 does not become smaller than the reference voltage V0.

When the amount of light received by the photomultiplier tube 10 changes from P 0 or more to P 0 or less, The current signal output from the node electrode 12 becomes smaller, and the voltage signal VI output from the current-voltage converter 30 becomes lower than the reference voltage V0. This is detected by the comparing section 50, and the voltage applied by the power supply section 60 to the photomultiplier tube 10 via the voltage dividing section 20 increases. However, the applied voltage does not exceed a certain voltage. When the applied voltage reaches the constant voltage, the voltage signal VI output from the current-voltage converter 30 is equal to or lower than the reference voltage V0.

As described above, in the range where the amount of light received by the photomultiplier tube 10 is smaller than P 0, the voltage applied by the power supply unit 60 to the photomultiplier tube 10 is constant. The voltage signal VI output from the current-voltage converter 30 is large. However, the voltage signal V2 output from the buffer unit 70 is constant. On the other hand, when the amount of light received by the photomultiplier tube 10 is in the range of P 0 or more, the light amount detection device according to the present embodiment constitutes a feedback circuit. The voltage signal VI output from 30 is maintained at the same value as the reference voltage vo. However, the larger the light reception a, the smaller the voltage signal V2 output from the buffer unit 70.

It is desired that the setting of the voltage applied to the photomultiplier tube 10 by the power supply section 60 follows the change in the received light S at high speed. However, when the amount of received light increases sharply, the current flowing through the photomultiplier tube 10 increases. Even in such a case, the resistor R 22 of the voltage dividing section 20. RR 2 2 _{3 By} setting each of them to have a high resistance value, it is possible to prevent an excessive current from flowing through the photomultiplier tube 10.

Next, the operation of the signal processing unit 80 of the light quantity detection device according to the present embodiment will be described. FIG. 3 is a flowchart illustrating the operation of the signal processing unit 80 of the light amount detection device according to the present embodiment. The signal processing unit 80 receives the voltage signals VI and V2, performs an operation described below based on these, calculates the amount of light received by the photomultiplier tube 10, and calculates the amount of received light. And outputs a signal V3 representing.

First, in step S1, the signal processing unit 80 compares the input voltage signal VI and the stored reference voltage V0 with each other in magnitude, and if the voltage signal VI is If it is smaller than the signal VO, go to step S2, otherwise go to step S3. At this time, considering the influence of noise or the like, if the difference between the voltage signal VI and the reference signal V 0 is equal to or less than a certain value, it may be determined that the two are equal. Further, instead of comparing the voltage signal V 1 with the reference signal V 0, the process may proceed to either step S 2 or S 3 based on the voltage signal V 2. If the value of the voltage signal VI or V2 is not stable due to a change in the amount of received light, it may wait until the value of the voltage signal VI or V2 becomes stable.

In step S2, the signal processing unit 80 calculates the value of the signal V3 representing the amount of received light based on the value of the voltage signal VI. On the other hand, in step S3, the signal processing unit 80 calculates the value of the signal V3 representing the amount of received light based on the value of the voltage signal V2. To output a signal V3 that is linearly related to the amount of received light, follow the steps below. In other words, in the range where the light receiving amount of the photomultiplier tube 10 is smaller than P0, the voltage signal VI has a substantially linear relationship with the light receiving amount.In step S2, the voltage signal VI is linearly transformed. To calculate the value of the signal V3. On the other hand, when the amount of light received by the photomultiplier tube 10 is equal to or greater than P 0, the voltage signal V2 has a substantially linear relationship with the logarithmic value of the amount of light received. Convert to calculate the value of signal V3. Further, when the amount of light received by the photomultiplier tube 10 is P 0, steps S 2 and S 3 and the signal V3 calculated thereby need to be substantially equal to each other. Further, the derivative of the signal V 3 with respect to the received light amount is required to be substantially constant over a wide received light amount range. Therefore, in step S2 and / or S3, a predetermined linear transformation is performed to satisfy these requirements.

In step S4 following step S3, the value of the signal V3 calculated in step S3 is linearly corrected. In the range where the actual amount of light received by the photomultiplier tube 10 is equal to or greater than P 0, the voltage applied by the power supply unit 60 to the photomultiplier tube 10 via the voltage dividing unit 20 becomes small, and therefore, The linearity between the signal V 3 and the actual amount of received light may be poor only by performing the antilogarithmic conversion in step S3. Therefore, the value of signal V 3 is linearly corrected Thus, the linearity between the signal V3 and the actual amount of received light is improved.

In the light amount detection device according to the present embodiment described above, the dynamic range of the light amount detection is about 2 to 4 digits in the range of the light reception amount P 0 or less, and 4 in the range of the light reception amount P 0 or more. It is about 6 to 6 digits. Therefore, a dynamic range of about eight digits can be obtained as a whole. Also, since the current signal output from the anode electrode 12 of the photomultiplier tube 10 is less than a certain fixed value, the power consumption is small, and the photomultiplier tube 10 and peripheral circuits are The risk of destruction is small and easy to handle.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, the signal processing unit 80 replaces the voltage signal V2 output from the comparison unit 50 via the buffer unit 70 with the voltage from the power supply unit 60 to the photomultiplier tube 10 via the voltage dividing unit 20. The applied voltage to be applied may be received, and the amount of received light may be calculated based on the applied voltage. Further, the signal processing section 80 may output a signal representing a logarithmic value of the received light amount, instead of the signal V3 representing a value having a linear relationship with the received light amount. Industrial applicability

As described above, according to the present invention, the current signal output from the anode electrode of the photomultiplier is converted into a voltage signal by the current-voltage converter, and the voltage signal is compared with the reference signal by the comparator. . When the amount of received light is smaller than a certain amount, the comparator determines that the voltage signal is smaller than the reference voltage, and applies a certain voltage from the power supply to the photocathode of the photomultiplier, the dynode, and signal processing. The unit calculates the amount of received light based on the voltage signal. On the other hand, when the amount of received light is more than a certain amount, the comparator determines that the voltage signal is higher than the reference voltage, and the applied voltage adjusted so that the voltage signal matches the reference voltage is supplied from the power supply to the photomultiplier. The signal is applied to the photocathode and dynode of the tube, and the signal processor calculates the amount of received light based on the applied signal. Therefore, a wide dynamic range of about 8 digits can be obtained as a whole.

Claims

Scope of word blue

1. A photocathode that emits a number of photoelectrons according to the amount of received light, a dynode that multiplies the photoelectrons to generate secondary electrons, and an anode electrode that outputs a current signal according to the number of the secondary electrons A photomultiplier tube,

A current-voltage converter for converting the current signal output from the anode electrode into a voltage signal;

A comparison unit that compares the voltage signal output from the current-voltage conversion unit with a reference voltage;

When the comparing unit determines that the voltage signal is smaller than the reference voltage, a constant voltage is applied to the photocathode and the dynode of the photomultiplier tube, and the voltage signal is set to the reference voltage. When it is determined that the voltage is equal to or higher than the voltage, a power supply unit that applies the applied voltage adjusted so that the voltage signal matches the reference voltage, the photocathode of the photomultiplier tube, the dynode, and the like,

A signal processing unit that calculates a light reception amount based on the voltage signal when the voltage signal is smaller than the reference voltage, and calculates a light reception amount based on the applied voltage when the voltage signal is equal to or higher than the reference voltage;

A light amount detection device comprising:

2. The signal processing unit calculates the amount of received light by linearly converting the value of the voltage signal when the voltage signal is smaller than the reference voltage, and calculates the applied light when the voltage signal is equal to or higher than the reference voltage. 2. The light amount detection device according to claim 1, wherein an amount of received light is calculated by performing an inverse logarithmic conversion of the voltage value.

3. The light amount detection device according to claim 2, wherein the signal processing unit calculates the amount of received light by performing linear correction on the value of the applied voltage after performing an inverse logarithmic conversion.