Single photon counter circuit for weak light detection based on photomultiplier

Abstract

The invention relates to the technical field of photoelectric detection, and provides a single-photon counter circuit for weak light detection based on a photomultiplier, and the single-photon counter comprises a photoelectric conversion circuit, a differential amplification circuit, a threshold comparison circuit and a signal shaping circuit. The photoelectric conversion circuit is composed of a photomultiplier, a high-voltage power supply circuit and a voltage division circuit, detects weak light signals and outputs two paths of current signals through photoelectric conversion. The differential amplification circuit carries out differential amplification on the two current signals through a differential amplifier. The threshold comparison circuit compares two input signals, filters out signals with the amplitude lower than 1 / 2 of a set threshold, and outputs a single-path effective signal. And the signal shaping circuit shapes the effective signal and finally outputs the effective signal in a TTL pulse mode. According to the single photon counter circuit for weak light detection, the background dark counting rate is low, the sensitivity is high, and the counting unit module specially used for digital pulse statistics is connected behind the single photon counter circuit for counting single photons.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection technology, especially weak signal detection technology, and more specifically to a single-photon counter circuit for weak light detection based on a photomultiplier tube. Background Technology

[0002] In the field of optoelectronic detection technology, especially for the detection of extremely weak light signals (such as bioluminescence, chemiluminescence, high-resolution spectral analysis, quantum communication, astronomical observation, etc.), single-photon counting technology has become a key method due to its extremely high sensitivity. In these application scenarios, the light signal is often as weak as a single photon and is accompanied by a large amount of environmental noise and circuit background noise, which places stringent requirements on the sensitivity, dark counting suppression capability, and stability of the counter.

[0003] Currently, mainstream single-photon counters are mainly built based on photomultiplier tubes (PMTs) and avalanche photodiodes (APDs). As a high-performance photomultiplier tube, the PMT is the preferred device for weak light detection due to its high gain, low noise, and fast response. However, traditional PMT single-photon counters use high-voltage power supply circuits with poor output stability, and the voltage divider network design often employs resistor series voltage division, resulting in uneven voltage distribution across the PMT's multiplier electrodes. Thermionic emission from the cathode and field-induced emission from the multiplier electrode intensify, generating a large amount of dark current in the absence of light. After subsequent multiplication and amplification, this forms a pulse with an amplitude similar to the real photon signal, severely interfering with the effective identification of weak light signals. Performance degradation is particularly noticeable in low-temperature operating environments, leading to a significant deterioration in the signal-to-noise ratio (SNR). Even with subsequent signal amplification via a common-mode rejection module, typically using a single-ended amplifier circuit, the low CMR makes it difficult to effectively distinguish between signal and noise, resulting in insufficient SNR at the amplifier output and affecting the accuracy of subsequent signal identification.

[0004] In the signal filtering and shaping output stage, given the differential characteristics of the PMT output signal, using a fixed single threshold for filtering cannot effectively filter out noise pulses with amplitudes close to the threshold. Moreover, some existing fixed single thresholds rely on discrete resistor voltage division for generation, resulting in poor threshold stability and a tendency to miss valid signals or falsely detect noise during long-term operation. Summary of the Invention

[0005] In view of the defects and shortcomings of the existing single-photon counter circuit for weak light detection, the purpose of this invention is to provide a single-photon counter circuit for weak light detection based on a photomultiplier tube with strong structural robustness and low dark count rate, so as to achieve high sensitivity and stable detection of weak light.

[0006] According to a first aspect of the present invention, a single-photon counter circuit for weak light detection based on a photomultiplier tube is provided, comprising a photoelectric conversion circuit, a differential amplifier circuit, a threshold comparison circuit, and a signal shaping circuit; The photoelectric conversion circuit is used to convert the detected weak light signal into a photoelectric signal. The photoelectric conversion circuit consists of a photomultiplier tube, a high-voltage power supply circuit, and a voltage divider circuit. The high-voltage power supply circuit provides a high-voltage signal. The high-voltage signal is applied to each multiplier electrode of the photomultiplier tube after being divided step by step by the voltage divider circuit. It outputs two differential current signals, the secondary anode current and the anode current, and inputs them to the differential amplifier circuit. The differential amplifier circuit consists of a differential amplifier and a feedback loop, and is used to differentially amplify the two differential current signals output by the photoelectric conversion circuit. The threshold comparison circuit includes a threshold generation circuit and a comparison circuit. The threshold generation circuit generates a threshold voltage for the comparison circuit. The comparison circuit receives two differential amplified signals output by the differential amplifier circuit. By comparing the two input signals and filtering out invalid signals with amplitudes lower than 1 / 2 of the threshold voltage, the valid signals are retained and a single valid signal is output. The signal shaping circuit is used to shape the single valid signal output by the threshold comparison circuit and finally output it in TTL pulse mode.

[0007] The single-photon counter circuit for weak light detection according to the above embodiments of the present invention includes a photoelectric conversion circuit, a differential amplifier circuit, a threshold comparison circuit, and a signal shaping circuit. The photoelectric conversion circuit consists of a photomultiplier tube, a high-voltage power supply circuit, and a voltage divider circuit, detecting weak light signals and converting them into two current signals. The differential amplifier circuit consists of a differential amplifier and a feedback loop, differentially amplifying the two current signals. The threshold comparison circuit compares the two input signals, filtering out signals with amplitudes below half a set threshold, and outputting a single valid signal. The signal shaping circuit shapes the valid signal and outputs it as a TTL pulse. The single-photon counter circuit for weak light detection of the present invention has a low background dark count rate and high sensitivity. When connected to a dedicated counting unit module for digital pulse statistics, it can realize digital counting of single photons.

[0008] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below may be considered part of the inventive subject matter of this disclosure, provided that such concepts do not contradict each other. Furthermore, all combinations of the claimed subject matter are considered part of the inventive subject matter of this disclosure.

[0009] The foregoing and other aspects, embodiments, and features of the teachings of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the invention, such as features and / or beneficial effects of exemplary embodiments, will become apparent from the following description or may be learned through practice of specific embodiments according to the teachings of the present invention. Attached Figure Description

[0010] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings.

[0011] Figure 1 This is a schematic diagram of a single-photon counter circuit for weak light detection based on a photomultiplier tube according to an embodiment of the present invention.

[0012] Figure 2 This is a circuit diagram of a high-voltage power supply circuit according to an embodiment of the present invention.

[0013] Figure 3 This is a circuit diagram of a voltage divider circuit according to an embodiment of the present invention.

[0014] Figure 4 This is a circuit diagram of a photomultiplier tube according to an embodiment of the present invention.

[0015] Figure 5 This is a circuit diagram of a differential amplifier circuit according to an embodiment of the present invention.

[0016] Figure 6 This is a schematic diagram of the signal output of a differential amplifier circuit according to an embodiment of the present invention.

[0017] Figure 7 This is a circuit diagram of a threshold generation circuit according to an embodiment of the present invention.

[0018] Figure 8 This is a circuit diagram of a comparison circuit according to an embodiment of the present invention.

[0019] Figure 9 This is a schematic diagram of the output signal of the threshold comparison circuit according to an embodiment of the present invention.

[0020] Figure 10 This is a circuit diagram of a signal shaping circuit according to an embodiment of the present invention.

[0021] Figure 11 This is a schematic diagram of the signal output of a signal shaping circuit according to an embodiment of the present invention. Figure 12 This is a schematic diagram of the dark count rate test results according to an embodiment of the present invention.

[0022] Figure 13 The results are from a single-photon counter test of a 1pW light source according to an embodiment of the present invention. Detailed Implementation

[0023] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0024] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, which illustrate numerous illustrative embodiments. The embodiments of this disclosure are not necessarily intended to encompass all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed herein are not limited to any particular implementation. Furthermore, some aspects of the invention disclosed may be used alone or in any suitable combination with other aspects of the invention disclosed.

[0025] {Example 1} Combined with appendix Figures 1 to 13 As shown, the single-photon counter circuit for weak light detection based on a photomultiplier tube according to an embodiment of the present invention includes a photoelectric conversion circuit, a differential amplifier circuit, a threshold comparison circuit, and a signal shaping circuit.

[0026] A photoelectric conversion circuit is used to convert the weak light signal being detected into a photoelectric signal. For example... Figure 1 As shown, the photoelectric conversion circuit consists of a photomultiplier tube, a high-voltage power supply circuit, and a voltage divider circuit. The high-voltage power supply circuit provides a high-voltage signal, which is then applied to each multiplier electrode of the photomultiplier tube after being divided step by step by the voltage divider circuit. The output consists of two differential current signals: the secondary anode current and the anode current, which are then input to the differential amplifier circuit. A differential amplifier circuit, consisting of a differential amplifier and a feedback loop, is used to differentially amplify the two differential current signals output from a photoelectric conversion circuit.

[0027] The threshold comparison circuit includes a threshold generation circuit and a comparison circuit. The threshold generation circuit generates the threshold voltage for the comparison circuit. The comparison circuit receives two differential amplified signals from the differential amplifier circuit. By comparing the two input signals and filtering out invalid signals with amplitudes lower than 1 / 2 of the threshold voltage, the valid signals are retained and a single valid signal is output.

[0028] The signal shaping circuit is used to shape the single valid signal output by the threshold comparison circuit and finally output it in TTL pulse mode.

[0029] Combination Figure 2The example shown includes a high-voltage power supply circuit comprising a high-voltage power supply module U0, an adjustable resistor VR1, a first polarity capacitor C1, and a second polarity capacitor C2, for providing the high voltage required for the photomultiplier tube to operate.

[0030] The VIN pin of the high-voltage power supply module is connected to the power signal and to the positive terminal of the first polarized capacitor C1. The negative terminal of the first polarized capacitor C1 is connected to the ground signal. The GND pin of the high-voltage power supply module U0 is connected to the ground signal; The VADJ pin of the high-voltage power supply module U0 is connected to the tap of the adjustable resistor VR1. The VREF and Case pins of the high-voltage power supply module U0 are respectively connected to the two fixed terminals of the adjustable resistor VR1. The HV pin of the high-voltage power supply module U0 is connected to one end of the second polarity capacitor C2, and the other end of the second polarity capacitor C2 is grounded; and the high-voltage signal output by the HV pin is connected to the HV signal of the voltage divider circuit.

[0031] Combination Figure 2 As shown, after the high-voltage power module U0 is powered on, different HV high voltage values ​​can be obtained by adjusting the tap terminals of the adjustable resistor VR1. It should be understood that the adjustable resistor VR1 can be a knob-type adjustable resistor or a slide-type adjustable resistor. The resistance value of VR1 can be adjusted by turning the knob or sliding the slide, thereby obtaining different HV high voltage values.

[0032] Combination Figure 3 The example shown has a voltage divider circuit consisting of 12 resistors, 8 capacitors, and 2 transistors, used to provide different levels of voltage multiplication to the dynode of the photomultiplier tube. The photomultiplier tube has 11 dynodes, and the signal pins from the cathode to the anode are defined as K, D1, D2, D3, D4, D5, D6, D7, D8, D9, D10 and P, respectively. Each signal pin is connected to a voltage divider circuit.

[0033] Furthermore, combined Figure 3 , Figure 4 As shown, for ease of explanation, the first to twelfth resistors in the 12 resistors are defined as R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R23, and R24, respectively. The first to eighth capacitors in the 8 capacitors are defined as C11, C12, C13, C14, C15, C16, C17, and C18, respectively.

[0034] like Figure 3 , Figure 4 As shown, the connection relationship between the voltage divider circuit and the signal pins of the photomultiplier tube includes: One end of the first resistor R1 is connected to ground and to pin K of the photomultiplier tube, and the other end is connected to pin D1 of the photomultiplier tube and to one end of the second resistor R2. The other end of the second resistor R2 is connected to pin D2 of the photomultiplier tube and to one end of the third resistor R3; The other end of the third resistor R3 is connected to pin D3 of the photomultiplier tube and to one end of the fourth resistor R4. The other end of the fourth resistor R4 is connected to pin D4 of the photomultiplier tube and to one end of the fifth resistor R5. The other end of the fifth resistor R5 is connected to pin D5 of the photomultiplier tube and to one end of the sixth resistor R6. The other end of the sixth resistor R6 is connected to pin D6 of the photomultiplier tube and to one end of the seventh resistor R7. The other end of the 7th resistor R7 is connected to pin D7 of the photomultiplier tube and to one end of the 8th resistor R8. The other end of the 8th resistor R8 is connected to pin D8 of the photomultiplier tube, and is also connected to one end of the 9th resistor R9, one end of the 1st capacitor C11, one end of the 10th resistor R10, and one end of the 2nd capacitor C12. The other end of the 9th resistor R9 is connected to pin D9 of the photomultiplier tube, and to the other end of the 1st capacitor C11, one end of the 3rd capacitor R3, and the emitter (E) of the first NPN transistor Q1. The other end of the 10th resistor R10 is connected to the base (B) of the 1st NPN transistor Q1, and is also connected to the other end of the 2nd capacitor C12, one end of the 11th resistor R23, and one end of the 4th capacitor C14. The other end of the third capacitor C13 is connected to pin D10 of the photomultiplier tube, and is connected to the collector (C) of the first NPN transistor Q1, the emitter (E) of the second NPN transistor Q2, one end of the fifth capacitor C15, and one end of the sixth capacitor C16. The other end of the fifth capacitor C15 outputs a current signal D10_OUT, which serves as the secondary anode current and is connected to the input of the differential amplifier circuit. The other end of the 11th resistor R23 is connected to the base (B) of the 2nd NPN transistor Q2, and is also connected to the other end of the 4th capacitor C14, one end of the 12th resistor R24, and one end of the 7th capacitor C17. The other end of the sixth capacitor C17 is connected to the P pin of the photomultiplier tube, and to the collector (C) of the second NPN transistor Q2, the other end of the 12th resistor R24, the other end of the seventh capacitor C17, and one end of the eighth capacitor C18. The other end of the eighth capacitor C18 outputs a current signal P_OUT, which serves as the anode current and is connected to the other input terminal of the differential amplifier circuit.

[0035] Combination Figure 3 , Figure 4 As shown, pin D10 of the photomultiplier tube is connected to capacitor C15 of the voltage divider circuit, outputting the current signal D10_OUT; pin P is connected to another capacitor C18 of the voltage divider circuit, outputting the current signal P_OUT.

[0036] Therefore, the composite voltage divider network formed by the voltage divider circuit provides uniform and stable graded voltages for the 11 stages of the photomultiplier tube, avoiding field emission caused by excessive local electric field. Combined with the high-frequency filtering effect of capacitors C11~C18, the noise of the multiplier is further suppressed.

[0037] Combination Figure 5 The example shown illustrates a differential amplifier circuit including a signal input terminal, a differential amplifier U1, and a signal output terminal, used to amplify the differential signal output from the photoelectric conversion circuit. The two signal input terminals are used to receive two differential current signals D10_OUT and P_OUT from the photoelectric conversion circuit, respectively.

[0038] Differential amplifier U1 is used to differentially amplify two differential current signals according to a preset gain and output them. The differentially amplified output signals P_OPA_OUT and D10_OPA_OUT are respectively input to the signal input terminal of the threshold comparison circuit through its two signal output terminals.

[0039] like Figure 5 As shown, the differential amplifier circuit includes a differential amplifier U1, two switching diodes, and six resistors.

[0040] The IN1 pin of the differential amplifier U1 is connected to the secondary anode current D10_OUT output by the photoelectric conversion circuit, and the IN2 pin of the differential amplifier U1 is connected to the anode current P_OUT output by the photoelectric conversion circuit.

[0041] One end of the first resistor R11 is grounded, and the other end is connected in series with the second resistor R12 and then connected to VCC. At the intersection of the series connection of the first resistor R11 and the second resistor R12, connect the first switching diode VD1 to the signal input terminal corresponding to P_OUT, and connect the second switching diode VD2 to the signal input terminal corresponding to D10_OUT.

[0042] The third resistor R13 is connected in parallel with the first switching diode VD1; the fourth resistor R14 is connected in parallel with the second switching diode VD2.

[0043] A fifth resistor R15 is connected between the GA and GB pins of the differential amplifier U1 to control the gain of the differential amplifier.

[0044] The output of pin OUT1 of differential amplifier U1 is used as the first signal output terminal, outputting the secondary anode amplified signal D10_OPA_OUT; pin OUT2 of differential amplifier U1 is used as the second signal output terminal, outputting the anode amplified signal P_OPA_OUT, and pin OUT2 is connected to the sixth resistor R16 and then grounded.

[0045] like Figure 5 As shown, the voltage V1 at the intersection of resistors R11 and R12 in series is equal to VCC*r11 / (r11+r22); the forward voltage of switching diodes VD1 and VD2 (using the same model) is VF. Therefore, the common-mode voltage VCM of D10_OUT and P_OUT is calculated as follows: VCM = VCC * r11 / (r11 + r22) - VF.

[0046] When the resistance values ​​of resistor R11 and resistor R12 are equal, VCM = 0.5VCC - VF, which is used to raise the common-mode voltage of the input signal.

[0047] Therefore, in the differential amplifier circuit, a common-mode voltage boosting module is constructed based on switching diodes VD1 and VD2 and parallel resistors R13 and R14. This module can stabilize the input signal common-mode voltage at 0.5VCC-VF. Combined with differential amplifier U1 and gain control resistor R15, precise amplification of the differential signal is achieved (adjustable gain range of 10~100 times), with a common-mode rejection ratio ≥80dB, effectively suppressing power supply ripple and electromagnetic interference. The differential signals of D10_OUT and P_OUT are amplified by the differential amplifier before being output.

[0048] The amplified signal outputs D10_OPA_OUT and P_OPA_OUT are connected to the signal input of the threshold comparison circuit.

[0049] like Figure 6 As shown, an exemplary diagram illustrates the signal output waveform of a differential amplifier circuit.

[0050] Combination Figure 7The example shown includes a threshold generation circuit comprising a reference voltage chip U2, two capacitors, and a voltage output signal. Filter capacitors C31 and C32 are connected to ground at the IN and OUT pins of the reference voltage chip U2, respectively, for filtering. The GND pin of the reference voltage chip U2 is grounded. A stable threshold voltage VTH is obtained by outputting the threshold voltage through the OUT pin of the reference voltage chip U2.

[0051] Combination Figure 8 The example shown has a comparator circuit that includes two signal inputs, one comparator chip, three capacitors, two resistors, and one signal output.

[0052] The sub-anode amplified signal D10_OPA_OUT and the anode amplified signal P_OPA_OUT of the differential amplifier circuit are respectively connected to the two signal input terminals of the comparator circuit: the anode amplified signal P_OPA_OUT corresponds to the first input terminal, and the sub-anode amplified signal D10_OPA_OUT corresponds to the second input terminal.

[0053] like Figure 8 As shown, the first input terminal corresponding to the anode amplification signal P_OPA_OUT is connected to the output pin OUT of the reference voltage chip U2 after being connected to the DC blocking capacitor C3, to obtain the output threshold voltage VTH and the output signal P_COMP_IN. This output signal P_COMP_IN is input to the IN- pin of the comparator chip U3. The first input terminal is connected to the first DC blocking capacitor C3 and then grounded through the first resistor R17.

[0054] Correspondingly, the second input terminal of the secondary anode amplification signal D10_OPA_OUT is connected to the second DC blocking capacitor C4 and then connected to ground via the second resistor R18. The output signal D10_COMP_IN is connected to the IN+ pin of the comparator chip U3.

[0055] As shown in the attached figure, the signal preprocessing network constructed by dual DC blocking capacitors C3 and C4 and resistors R17 and R18 enables accurate comparison of the amplified differential signal, filters out invalid noise pulses with amplitudes lower than 1 / 2VTH (discrimination threshold), and improves the effective signal recognition rate by more than 30%.

[0056] Combination Figure 8 The V+ pin of comparator chip U3 is connected to the third capacitor C5 and then grounded; the V- pin of comparator chip U3 is connected to ground; the OUT pin of comparator chip U3 outputs the threshold comparison signal COMP_OUT.

[0057] like Figure 9An example is shown of the signal output waveform of the threshold comparison circuit.

[0058] Combination Figure 10 As shown, the signal shaping circuit includes one signal input terminal, one dual-channel D flip-flop chip, two capacitors, three resistors, one diode, and one signal output terminal. It is used to shape the output waveform for subsequent digital acquisition. For example, it can be connected to a digital counting unit based on an FPGA or microcontroller for counting.

[0059] like Figure 10 As shown, the single valid signal output by the threshold comparison circuit is connected to the signal input terminal of the signal shaping circuit, and the signal input terminal of the signal shaping circuit is connected to the CLK pin of the first flip-flop of the dual-channel D flip-flop chip U4.

[0060] The 1D pin of the first flip-flop is connected to VCC, the #1PRE pin is connected to VCC, the first resistor R19 is connected between the #1Q pin and the #1CLR pin, and the #1CLR pin is connected to the first capacitor C6 and then grounded. The 1Q pin of the first flip-flop is connected to the 2CLK pin of the second flip-flop; The 2D pin of the second flip-flop is connected to VCC, the #2PRE pin is connected to VCC, the second resistor R20 and the diode VD3 are connected between the #2Q pin and the #2CLR pin respectively, the anode of the diode VD3 is connected to the #2Q pin, the cathode is connected to the #2CLR pin, and the #2CLR pin is connected to the second capacitor C7 and then grounded. The second flip-flop's 2Q pin is connected to the third resistor R21, and the third resistor R19 is connected to the signal output terminal, outputting TTL_OUT.

[0061] Figure 11 The waveform of the output signal of the signal shaping circuit is shown as an example.

[0062] {Example 2} In this embodiment, we conducted dark count rate testing and sensitivity and stability testing of a picometer-level 400nm light source based on the single-photon counter circuit for weak light detection proposed in this invention.

[0063] Dark count rate test results are as follows Figure 12 As shown, the test lasted for 1 hour. Figure 12 The results shown have an average dark count rate of approximately 26, which is extremely low.

[0064] The test results of sensitivity and stability of the 400nm light source at the picowatt level are as follows: Figure 13 As shown, the test lasted for 10 hours. The tested sensitivity of the 400nm picosecond light source was 4.7 × 10⁻⁶. 5 s -1 ·pW -1It can effectively capture extremely weak light signals; the stability CV value is 0.2%, which is excellent.

[0065] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A single photon counter circuit for weak light detection based on a photomultiplier tube, characterized by The circuit comprises a photoelectric conversion circuit, a differential amplification circuit, a threshold comparison circuit and a signal shaping circuit, wherein: The photoelectric conversion circuit is used for photoelectric conversion of the detected weak light signal, and is composed of a photomultiplier, a high-voltage power supply circuit and a voltage dividing circuit. The high-voltage power supply circuit provides a high-voltage signal, the high-voltage signal is step-by-step divided by the voltage dividing circuit and then applied to each multiplication electrode of the photomultiplier, and two differential current signals of a secondary anode current and an anode current are output and input to the differential amplification circuit. The differential amplification circuit is composed of a differential amplifier and a feedback loop, and is used for differential amplification of the two differential current signals output by the photoelectric conversion circuit. The threshold comparison circuit comprises a threshold generation circuit and a comparison circuit. The threshold generation circuit is used for generating a threshold voltage of the comparison circuit. The comparison circuit receives the two differential amplification signals output by the differential amplification circuit, compares the two input signals, filters out invalid signals with an amplitude lower than 1 / 2 of the threshold voltage, retains valid signals and outputs a single valid signal. The signal shaping circuit is used for shaping the single valid signal output by the threshold comparison circuit, and finally outputs a TTL pulse.

2. The single photon counter circuit for weak light detection based on a photomultiplier tube according to claim 1, characterized in that, The high-voltage power supply circuit comprises a high-voltage power supply module U0, an adjustable resistor VR1, a first polarity capacitor C1 and a second polarity capacitor C2, and is used for providing the required high voltage for the operation of the photomultiplier. The VIN pin of the high-voltage power supply module is connected to a power supply signal and the positive terminal of the first polarity capacitor C1. The negative terminal of the first polarity capacitor C1 is connected to a ground signal. The GND pin of the high-voltage power supply module U0 is connected to a ground signal. The VADJ pin of the high-voltage power supply module U0 is connected to the tap terminal of the adjustable resistor VR1. The VREF pin and the Case pin of the high-voltage power supply module U0 are respectively connected to the two fixed terminals of the adjustable resistor VR1. The HV pin of the high-voltage power supply module U0 is connected to one end of the second polarity capacitor C2, and the other end of the second polarity capacitor C2 is grounded. The high-voltage signal output by the HV pin is connected to the HV signal of the voltage dividing circuit.

3. The single photon counter circuit for weak light detection based on a photomultiplier tube according to claim 2, characterized in that, After the power supply is turned on, the tap terminal of the adjustable resistor VR1 is adjusted to obtain different values of HV high voltage.

4. The single photon counter circuit for weak light detection based on a photomultiplier tube according to claim 2, characterized in that, The voltage dividing circuit comprises 12 resistors, 8 capacitors and 2 triodes, and is used for providing different levels of voltage to the multiplication electrodes of the photomultiplier. The photomultiplier has 11 multiplication electrodes, and the signal pins from the cathode to the anode are defined as K, D1, D2, D3, D4, D5, D6, D7, D8, D9, D10 and P in sequence. Each signal pin is connected to the voltage dividing circuit.

5. The photomultiplier tube-based single-photon counter circuit for weak light detection according to claim 3, wherein The connection relationship between the voltage dividing circuit and the signal pins of the photomultiplier comprises: The first resistor to the twelfth resistor in the 12 resistors are defined as R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R23 and R24, respectively. The first to eighth capacitors are defined as C11, C12, C13, C14, C15, C16, C17, and C18, respectively; One end of the first resistor R1 is connected to the ground and to the K pin of the photomultiplier tube, and the other end is connected to the D1 pin of the photomultiplier tube and to one end of the second resistor R2; The other end of the second resistor R2 is connected to the D2 pin of the photomultiplier tube and to one end of the third resistor R3; The other end of the third resistor R3 is connected to the D3 pin of the photomultiplier tube and to one end of the fourth resistor R4; The other end of the fourth resistor R4 is connected to the D4 pin of the photomultiplier tube and to one end of the fifth resistor R5; The other end of the fifth resistor R5 is connected to the D5 pin of the photomultiplier tube and to one end of the sixth resistor R6; The other end of the sixth resistor R6 is connected to the D6 pin of the photomultiplier tube and to one end of the seventh resistor R7; The other end of the seventh resistor R7 is connected to the D7 pin of the photomultiplier tube and to one end of the eighth resistor R8; The other end of the eighth resistor R8 is connected to the D8 pin of the photomultiplier tube and to one end of the ninth resistor R9, one end of the first capacitor C11, one end of the tenth resistor R10, and one end of the second capacitor C12; The other end of the ninth resistor R9 is connected to the D9 pin of the photomultiplier tube and to the other end of the first capacitor C11, one end of the third capacitor R3, and the emitter (E) of the first NPN transistor Q1; The other end of the tenth resistor R10 is connected to the base (B) of the first NPN transistor Q1, the other end of the second capacitor C12, one end of the eleventh resistor R23, and one end of the fourth capacitor C14; The other end of the third capacitor C13 is connected to the D10 pin of the photomultiplier tube and to the collector (C) of the first NPN transistor Q1, the emitter (E) of the second NPN transistor Q2, one end of the fifth capacitor C15, and one end of the sixth capacitor C16; The other end of the fifth capacitor C15 outputs a current signal D10_OUT, which is the secondary anode current, to the input of the differential amplification circuit; The other end of the eleventh resistor R23 is connected to the base (B) of the second NPN transistor Q2, the other end of the fourth capacitor C14, one end of the twelfth resistor R24, and one end of the seventh capacitor C17; The other end of the sixth capacitor C17 is connected to the P pin of the photomultiplier tube and to the collector (C) of the second NPN transistor Q2, the other end of the twelfth resistor R24, the other end of the seventh capacitor C17, and one end of the eighth capacitor C18; The other end of the eighth capacitor C18 outputs a current signal P_OUT, which is the anode current, to the other input of the differential amplification circuit.

6. The photomultiplier tube-based single-photon counter circuit for weak light detection according to claim 4, wherein The differential amplification circuit comprises a signal input end, a differential amplifier and a signal output end, and is used for amplifying a differential signal output by the photoelectric conversion circuit, wherein: The two signal input ends are respectively used for receiving two differential current signals D10_OUT and P_OUT output by the photoelectric conversion circuit. The differential amplifier is used for differentially amplifying the two differential current signals according to a preset gain, and outputs the differential amplified signals P_OPA_OUT and D10_OPA_OUT through two signal output ends.

7. The single photon counter circuit for weak light detection based on a photomultiplier tube according to claim 6, characterized in that, The differential amplification circuit comprises a differential amplifier U1, two switching diodes and six resistors, wherein: The IN1 pin of the differential amplifier U1 is connected to the secondary anode current D10_OUT output by the photoelectric conversion circuit, and the IN2 pin of the differential amplifier U1 is connected to the anode current P_OUT output by the photoelectric conversion circuit. One end of the first resistor R11 is grounded, and the other end is connected to VCC in series with the second resistor R12. At the series intersection of the first resistor R11 and the second resistor R12, the first switching diode VD1 is connected to the signal input end corresponding to P_OUT, and the second switching diode VD2 is connected to the signal input end corresponding to D10_OUT. The third resistor R13 is connected in parallel with the first switching diode VD1. The fourth resistor R14 is connected in parallel with the second switching diode VD2. The fifth resistor R15 is connected between the GA and GB pins of the differential amplifier U1, and is used for controlling the gain of the differential amplification. The out1 pin of the differential amplifier U1 outputs as the first signal output end, and outputs the secondary anode amplification signal D10_OPA_OUT. The out2 pin of the differential amplifier U1 outputs as the second signal output end, and outputs the anode amplification signal P_OPA_OUT, and the out2 pin is connected to the sixth resistor R16 and then grounded.

8. The photomultiplier tube-based single-photon counter circuit for weak light detection according to claim 1, wherein, The threshold generation circuit comprises one reference voltage chip U2, two capacitors and one voltage output signal, wherein the IN pin and the OUT pin of the reference voltage chip U2 are connected to the filter capacitors C31 and C32 and grounded for filtering, the GND pin of the reference voltage chip U2 is grounded, and the threshold voltage VTH is output through the OUT pin of the reference voltage chip U2.

9. The single photon counter circuit for weak light detection based on a photomultiplier tube according to claim 8, characterized in that, The comparison circuit comprises two signal input ends, one comparator chip, three capacitors, two resistors and one signal output end. The secondary anode amplification signal D10_OPA_OUT and the anode amplification signal P_OPA_OUT output by the differential amplification circuit are respectively connected to the two signal input ends of the comparison circuit: the anode amplification signal P_OPA_OUT corresponds to the first input end, and the secondary anode amplification signal D10_OPA_OUT corresponds to the second input end. The first input end corresponding to the anode amplification signal P_OPA_OUT is connected to the output pin OUT of the reference voltage chip U2 after connecting the DC blocking capacitor C3, to obtain the output threshold voltage VTH, and output the signal P_COMP_IN, which is input to the IN- pin of the comparator chip U3 and the comparator chip U3; wherein the first input end is connected to the ground via the first resistor R17 after connecting the first DC blocking capacitor C3; The second input end corresponding to the secondary anode amplification signal D10_OPA_OUT is connected to the ground via the second resistor R18 after connecting the second DC blocking capacitor C4, and outputs the signal D10_COMP_IN, wherein the first resistor R17 is connected to the second resistor R18, and the output signal D10_COMP_IN is input to the IN+ pin of the comparator chip U3 and the comparator chip U3; The V+ pin of the comparator chip U3 is connected to the ground after connecting the third capacitor C5; The V- pin of the comparator chip U3 is connected to the ground; The OUT pin of the comparator chip U3 outputs the signal COMP_OUT after threshold comparison.

10. The single photon counter circuit for weak light detection based on a photomultiplier tube according to claim 9, characterized in that, The signal shaping circuit includes one signal input end, one dual-channel D flip-flop chip, two capacitors, three resistors, one diode, and one signal output end, which is used to realize the shaping of the output waveform, wherein: The single-channel effective signal output by the threshold comparison circuit is input to the signal input end of the signal shaping circuit, and the signal input end of the signal shaping circuit is connected to the CLK pin of the first flip-flop of the dual-channel D flip-flop chip U4; The 1D pin of the first flip-flop is connected to VCC, the #1PRE pin is connected to VCC, the #1Q pin and the #1CLR pin are connected to the first resistor R19, and the #1CLR pin is connected to the first capacitor C6 and then connected to the ground; The 1Q pin of the first flip-flop is connected to the 2CLK pin of the second flip-flop; The 2D pin of the second flip-flop is connected to VCC, the #2PRE pin is connected to VCC, the #2Q pin and the #2CLR pin are connected to the second resistor R20 and the diode VD3 respectively, the anode of the diode VD3 is connected to the #2Q pin, the cathode is connected to the #2CLR pin, and the #2CLR pin is connected to the second capacitor C7 and then connected to the ground; The 2Q pin of the second flip-flop is connected to the third resistor R21, and the third resistor R19 is connected to the signal output end and outputs the TTL_OUT.

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