Optical amplifier based on single photon avalanche photodiode array and working method

Abstract

The application discloses a kind of photoelectric amplifier and working method based on single-photon avalanche photodiode array, photoelectric amplifier is not susceptible to background light, can directly extract effective echo signal from background light, its signal processing method can convert the voltage pulse generated by SPAD into standard current pulse, is handled by current buffer, and is merged into transimpedance amplification circuit, then is output after being further amplified by post-amplification circuit;This method can give the result in a single measurement, without relying on histogram statistics result, standard pulse current can realize high customization, not in dependence on the output voltage pulse of SPAD, the addition of current buffer summation circuit reduces the sensitivity of overall circuit to parasitic parameter, so higher circuit bandwidth can be realized, and this scheme also retains the single-photon detection capability of SPAD.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photoelectric measurement, in particular to a photoelectric amplifier based on a single-photon avalanche photodiode array and a working method. BACKGROUND

[0002] Photoelectric detection and ranging systems are applied in many fields requiring object identification, as they are able to reconstruct 3D scenes with sub-centimeter resolution. Among different 3D ranging techniques such as stereo vision and structured light projection, the Time of Flight (TOF) method is the most promising by measuring the light echo of the target, and is an ideal solution for long-range measurement. In direct-Time of Flight (dTOF) ranging, a pulsed laser illuminates the scene, and a photoelectric detector detects the backscattered light, which triggers a time-to-digital converter to measure the TOF delay between the light excitation and the echo after the photoelectric detector and signal processing circuit. In the field of autonomous driving, for example, to cope with different situations, the sensor usually has a resolution of only a few centimeters, a range of hundreds of meters, and a very short calculation time. Therefore, the detector must have a wide dynamic range, as the laser echo decreases with the square of the distance, the reflectivity of the target varies greatly, and the background light is usually high.

[0003] In photoelectric detection applications, the current mainstream is the Avalanche PhotoDiode (APD) detector, and in recent years, the research on Single Photon Avalanche Diode (SPAD) has gradually increased. The avalanche multiplication effect of SPAD detectors can realize digital operation and provide single-photon sensitivity. Silicon SPAD (with a spectral response range of up to 1000 nm wavelength) can be used at room temperature, has a low Dark Count Rate (DCR), and can be integrated with on-chip analog and digital electronics for TOF measurement and distance processing. Unfortunately, the dead time required to quench the SPAD and reset it back to the running state after each trigger limits the maximum measurement rate. In addition, since the SPAD (through its quenching and reset circuit) will provide a digital pulse when triggered by at least one photon or any other generation process (such as DCR), it is not possible to distinguish one or more concurrent photons. Due to false triggers, such as the presence of intrinsic DCR and background light, the distance of the target cannot be obtained through a single TOF measurement.

[0004] Typically, the acquisition is repeated many times (from tens to thousands) to accumulate a histogram of TOF measurements, whose peaks typically represent useful laser returns, while other lower peaks can come from false multiple reflections, and the baseline from DCR events and random time distribution of background photons. When the timing electronics can only measure one TOF per laser shot, only the first triggered event is recorded, while all subsequent events are lost. This "electronic pile-up" distorts the histogram, with higher probability of false events (e.g. as the background or target distance increases). Therefore, in noisy environments, a Time-to-Digital Converter (TDC) with multiple shots and a memory capable of recording multiple TOF data per laser shot (including false and true events) is required.

[0005] Some photodetection systems employ Silicon photomultipliers (SiPMs), which are composed of multiple SPADs connected to a common analog output, producing a total current signal given by the sum of the avalanche current pulses of the triggered SPADs. An analog discriminator senses when a given threshold is exceeded, triggering a TDC. Such a threshold either has a high trigger rate or a low sensitivity, without trading off between high values (to minimize false triggers) and low values (to maximize sensitivity), with low system performance.

[0006] In summary, histogram measurement methods based on SPADs are susceptible to interference, have a very narrow dynamic range, cannot distinguish between noise and valid signal triggers, and can only estimate the true measurement distance based on histogram statistics from multiple measurements, without giving a measurement result from a single measurement. Measurement schemes based on SIPM detectors can measure single times, but are limited by the all-parallel structure of the SPAD output, a single quenching resistor, an output pulse that cannot be accurately controlled, and large parasitic parameters that severely limit the bandwidth and other parameters of the subsequent processing circuit. SUMMARY

[0007] The present application aims to provide a single-photon avalanche photodiode array-based photoelectric amplifier and working method to solve the above problems in the prior art.

[0008] In a first aspect, an embodiment of the present application provides a single-photon avalanche photodiode array-based photoelectric amplifier, which comprises:

[0009] a SPAD array, a reference current generation circuit, a readout current generation array, a current buffer summation circuit, a transimpedance amplification circuit, and a post-amplification circuit; the SPAD array, the reference current generation circuit, and the current buffer summation circuit are electrically connected to the readout current generation array; the transimpedance amplification circuit and the post-amplification circuit are electrically connected to the current buffer summation circuit;

[0010] The SPAD array is used to generate a voltage pulse signal;

[0011] A reference current generating circuit is used to generate a pre-prepared reference current signal and a bias signal thereof;

[0012] A readout current generating array is used to generate a pulse current signal based on the bias signal and the voltage pulse signal;

[0013] A current buffer summing circuit is used to obtain a current pulse summing signal based on the pulse current signal;

[0014] A transimpedance amplification circuit is used to convert the current pulse summing signal into an output voltage signal;

[0015] A post-amplification circuit is used to amplify and output the voltage signal.

[0016] Optionally, the reference current generating circuit comprises a reference voltage circuit Vbg, an operational amplifier OPA and a resistor R1; the reference voltage circuit Vbg is connected with the operational amplifier OPA, and the operational amplifier OPA and the resistor R1 constitute a small closed loop connection.

[0017] Optionally, the readout current generating array receives bias voltage VB1 and VB2 signals and corresponds to the SPAD unit one by one, and generates IOUT signals under the driving of the SPAD unit output signal Vpulse.

[0018] Optionally, in the current buffer summing circuit, the IOUT signals of all SPAD pixels are all input into the IIN port of the current buffer summing circuit, and the current is summed and processed, and IOUT is the output current after buffering.

[0019] Optionally, the current buffer summing circuit is an adjustable common-source common-gate structure, and the M1 and R1 branch and the M2 and R2 branch constitute a negative feedback structure.

[0020] Optionally, in the transimpedance amplification circuit, the output current of the current buffer summing circuit is input into the input port of the transimpedance amplification circuit, and the current signal is converted into a voltage signal.

[0021] Optionally, in the post-amplification circuit, the post-amplification circuit is a two-stage structure, the first stage is a feedback proportional amplifier used to provide a set amplification proportion coefficient, and the second stage is an output buffer used to provide a required driving capability.

[0022] Optionally, the readout current generating array corresponds to the SPAD array one by one, and the circuit tube size of the readout current generating array is set as a fixed value or an adjustable value.

[0023] Optionally, the current buffer summing circuit adopts a common-gate structure or an adjustable common-source common-gate structure.

[0024] Optionally, the trans-impedance amplification circuit is single-ended or differential structure, and the overall structure is realized by resistance feedback, and the resistance is set as a fixed value or an adjustable value.

[0025] The application further provides a working method of a photoelectric amplifier based on a single-photon avalanche photodiode array.

[0026] The SPAD array, the reference current generation circuit, the readout current generation array, the current buffer summation circuit, the trans-impedance amplification circuit and the post-amplification circuit are electrically connected with the readout current generation array; the trans-impedance amplification circuit and the post-amplification circuit are electrically connected with the current buffer summation circuit.

[0027] The working method of the photoelectric amplifier based on the single-photon avalanche photodiode array comprises the following steps:

[0028] A voltage pulse signal is generated through the SPAD array;

[0029] A prefabricated reference current signal and a bias signal thereof are generated through the reference current generation circuit;

[0030] A pulse current signal is generated through the readout current generation array based on the bias signal and the voltage pulse signal;

[0031] A current pulse summation signal is obtained through the current buffer summation circuit based on the pulse current signal;

[0032] The current pulse summation signal is converted into an output voltage signal through the trans-impedance amplification circuit;

[0033] The voltage signal is amplified through the post-amplification circuit and then output.

[0034] Compared with the prior art, the technical scheme provided by the application has the following beneficial effects:

[0035] The application provides a single-photon avalanche photodiode array-based photoelectric amplifier and a working method thereof. The application provides a single-photon avalanche photodiode array-based photoelectric amplifier and a working method thereof, and the photoelectric amplifier comprises a SPAD array, a reference current generation circuit, a readout current generation array, a current buffer summation circuit, a transimpedance amplification circuit and a post-amplification circuit; the SPAD array, the reference current generation circuit and the current buffer summation circuit are electrically connected with the readout current generation array; the transimpedance amplification circuit and the post-amplification circuit are electrically connected with the current buffer summation circuit, the circuit is not easily affected by background light, can directly extract an effective echo signal from the background light, the signal processing method thereof can convert a voltage pulse generated by the SPAD into a standard current pulse, the current buffer is processed, and then the current is merged into the transimpedance amplification circuit, and then the signal is further amplified by the post-amplification circuit and output. According to the method, a result can be obtained by single measurement, and the result does not need to depend on a histogram statistical result; the standard pulse current can be highly customized, and does not depend on an output voltage pulse of the SPAD; the current buffer summation circuit is added, the sensitivity of the overall circuit to parasitic parameters is reduced, and therefore a higher circuit bandwidth can be realized; and the single-photon detection capability of the SPAD is also reserved. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 FIG. 1 is a single-photon avalanche photodiode array-based photoelectric amplifier provided by an embodiment of the application.

[0037] Figure 2 FIG. 2 is a reference current generation circuit provided by an embodiment of the application.

[0038] Figure 3 FIG. 3 is a readout circuit current generation unit circuit provided by an embodiment of the application.

[0039] Figure 4 FIG. 4 is a current buffer summation circuit provided by an embodiment of the application.

[0040] Figure 5 FIG. 5 is a transimpedance amplification circuit provided by an embodiment of the application.

[0041] Figure 6 FIG. 6 is a post-amplification circuit provided by an embodiment of the application.

[0042] Figure 7 FIG. 7 is a working method flowchart of a single-photon avalanche photodiode array-based photoelectric amplifier provided by an embodiment of the application.

[0043] Figure 8 FIG. 8 is a working method flowchart of another single-photon avalanche photodiode array-based photoelectric amplifier provided by an embodiment of the application. DETAILED DESCRIPTION

[0044] The application will be described in detail below with reference to the drawings.

[0045] Embodiment 1

[0046] As Figure 1 shown, the embodiment of the application provides a photoelectric amplifier based on a single-photon avalanche photodiode array, which comprises a SPAD array, a reference current generation circuit, a readout current generation array, a current buffer summation circuit, a transimpedance amplification circuit and a post-amplification circuit. The SPAD array, the reference current generation circuit and the current buffer summation circuit are electrically connected with the readout current generation array, and the transimpedance amplification circuit and the post-amplification circuit are electrically connected with the current buffer summation circuit.

[0047] The SPAD array is used to generate a voltage pulse signal.

[0048] The reference current generation circuit is used to generate a prefabricated reference current signal and a bias signal thereof.

[0049] The readout current generation array is used to generate a pulse current signal based on the bias signal and the voltage pulse signal.

[0050] The current buffer summation circuit is used to obtain a current pulse summation signal based on the pulse current signal.

[0051] The transimpedance amplification circuit is used to convert the current pulse summation signal into an output voltage signal.

[0052] The post-amplification circuit is used to amplify and output the voltage signal.

[0053] The photoelectric amplifier based on the single-photon avalanche photodiode array described above is not susceptible to background light, can directly extract an effective echo signal from the background light, and the signal processing method thereof can convert the voltage pulse generated by the SPAD into a standard current pulse, process it through a current buffer, merge it into a transimpedance amplifier, and then output it after further amplification by a post-amplifier. This method can give a result in a single measurement without relying on histogram statistical results, and the standard pulse current can be highly customized without relying on the output voltage pulse of the SPAD. The addition of the current buffer circuit reduces the sensitivity of the overall circuit to parasitic parameters, so a higher circuit bandwidth can be achieved, and the single-photon detection capability of the SPAD is also retained. Optionally, the SPAD is arranged in an array, and the detector can be manufactured by SI (silicon), GE (germanium) and InGaAs (indium gallium arsenide) processes.

[0054] As further, Figure 2As shown, the reference current generating circuit includes a reference voltage circuit Vbg, an operational amplifier OPA and a resistor R1; the reference voltage circuit Vbg is connected with the operational amplifier OPA, and the operational amplifier OPA and the resistor R1 constitute a small closed loop connection. By using the negative feedback principle, the resistance end voltage is locked, so as to generate a precise current controllable by the resistance, and the temperature characteristic of the current is completely consistent with the reference voltage vbg. The reference current generating circuit generates a reference current IREF which is independent of temperature, and the bias voltage required by the readout circuit current generating unit can be generated by IREF, and a specific numerical current is output. Figure 2 In the figure, Vbg represents the reference voltage circuit, OPA represents the operational amplifier, R1 represents the resistor, and GND represents the ground end of the device. IREF represents the reference current.

[0055] Optionally, the reference current can be a current independent of temperature or other reference current with a temperature coefficient.

[0056] In the embodiment of the present application, the readout current generating array receives the bias voltage VB1 and VB2 signals and corresponds to the SPAD unit one by one, and generates the IOUT signal under the driving of the SPAD unit output signal Vpulse. For details, please refer to Figure 3 .

[0057] Optionally, the readout current generating array corresponds to the SPAD array one by one, and the circuit tube size can be set to a fixed value or an adjustable value.

[0058] Pixel triggering refers to that in the SPAD array, each pixel (i.e. each independent SPAD unit) sends out a trigger signal when detecting a photon. For details, please refer to Figure 4 In the current buffer summation circuit, the IOUT signals of all SPAD pixels are all input into the IIN port of the current buffer summation circuit. The current is processed, INN represents the input current, and IOUT is the output current after buffering. The current buffer summation circuit is an adjusting common source common gate structure, I0 is a bias current, and the M1 and R1 branch and the M2 and R2 branch constitute a negative feedback structure. R1 and R2 are resistors, and M1 and M2 are transistors. VDD represents the power supply end of the device, and GND represents the ground end of the device.

[0059] Optionally, the current buffer circuit can adopt a common gate structure or an adjusting common source common gate structure, and the latter can effectively reduce the input impedance of the current buffer circuit structure.

[0060] For details, please refer to Figure 5 In the transimpedance amplification circuit, the output current of the current buffer summation circuit is input into the input port of the transimpedance amplification circuit, and the current signal is converted into a voltage signal. Here, the transimpedance amplifier (transimpedance amplification circuit) can be a fully differential structure. Figure 5In the figure, R1, R2 represent resistance, OPA represents operational amplifier, IIP and IIN both represent input of trans-impedance amplifier circuit, VOP and VOA represent output of trans-impedance amplifier circuit. IIN and IIP represent two differential input interfaces, IIN represents negative input interface, INP represents positive input interface, which can be used in full differential mode or single-ended mode.

[0061] Optionally, the trans-impedance amplifier can be single-ended or differential structure, and the overall structure is realized by resistance feedback, and the resistance can be set as a fixed value or an adjustable value.

[0062] Please refer to Fig. 6, in the post-amplification circuit, the post-amplification circuit is a two-stage structure, the first stage is a feedback proportional amplifier, which is used to provide a set amplification proportional coefficient, and the set value can be the proportion of the equivalent resistance value of the diode connected MOS tube M3 / M4 and the resistance R1 resistance 1 / 2, and the second stage is an output buffer, which is used to provide the required driving capability. In Fig. 6, I1, I2, I3 and I4 represent current, R1 represents resistance, M1, M2, M3, M4, M5 and M6 are transistors, I1, I2, I3 and I4 represent current source circuit, provide bias current, R1 represents resistance, M1, M2, M3, M4, M5 and M6 are transistors, VIP and VIN represent the voltage input positive and negative ports of the circuit respectively, VOP and VON represent the voltage output positive and negative ports of the circuit respectively. I1, I2, R1, M1, M2, M3 and M4 constitute the first stage proportional amplifier. I3, I4, M3 and M4 constitute the second stage output buffer, which provides the required driving capability.

[0063] Optionally, the post-amplification circuit at least covers an output buffer stage, which provides sufficient driving capability, and a proportional amplifier can be inserted as needed to provide additional gain.

[0064] The embodiment of the present application also provides a working method of the photoelectric amplifier based on the single-photon avalanche photodiode array, and the method comprises the steps shown in the figure: Figure 7

[0065] S1: The pixel of the SPAD array is triggered to generate a voltage pulse signal.

[0066] S2: The reference current generation circuit generates a pre-prepared reference current signal and a bias signal, and the current generation array of the readout circuit generates a pulse current signal based on the bias signal and under the driving of the output voltage pulse signal of the SPAD pixel.

[0067] S3: The buffer current circuit outputs a current pulse summation signal and inputs the trans-impedance amplifier.

[0068] In the figure, the buffer current circuit represents a buffer current summation circuit.

[0069] ​S4: The trans-impedance amplifier outputs the signal to a post-amplifier, and generates a final output signal.

[0070] As an optional implementation, the working method comprises the steps as shown in the figure. Figure 8

[0071] S101: A voltage pulse signal is generated by a SPAD array.

[0072] S102: A pre-prepared reference current signal and a bias signal thereof are generated by a reference current generation circuit.

[0073] S103: A pulse current signal is generated by a readout current generation array based on the bias signal and the voltage pulse signal.

[0074] S104: A current pulse summation signal is obtained by a current buffer summation circuit based on the pulse current signal.

[0075] S105: The current pulse summation signal is converted into an output voltage signal by a trans-impedance amplification circuit.

[0076] S106: The voltage signal is amplified by a post-amplification circuit and then outputted.

[0077] In the above steps, the specific implementation structure and mode of each step have been described in the above introduction about the photovoltaic amplifier based on the single-photon avalanche photodiode array, and specific reference can be made to the above description, which will not be repeated here.

[0078] By adopting the above scheme, the photovoltaic amplifier based on the single-photon avalanche photodiode array and the working method proposed by the application are not susceptible to background light, can directly extract effective echo signals from background light, the signal processing method can convert the voltage pulse generated by the SPAD into a standard current pulse, the current buffer is processed, and the trans-impedance amplifier is merged, and then the post-amplifier is further amplified and outputted. This method can give the result in a single measurement, without relying on the histogram statistical result, the standard pulse current can realize high customization, and the output voltage pulse of the SPAD is not relied on, the addition of the current buffer circuit reduces the sensitivity of the overall circuit to parasitic parameters, so that higher circuit bandwidth can be realized, and this scheme also retains the single-photon detection capability of the SPAD.​

Claims

1. A photoelectric amplifier based on a single-photon avalanche photodiode array, characterized in that: The photoelectric amplifier comprises: SPAD array, reference current generating circuit, readout current generating array, current buffer summing circuit, transimpedance amplifier circuit and post-amplifier circuit; SPAD array, reference current generating circuit and current buffer summing circuit are electrically connected to the readout current generating array; transimpedance amplifier circuit and post-amplifier circuit are electrically connected to the current buffer summing circuit; The SPAD array is used to generate voltage pulse signals; A reference current generating circuit is used to generate a prefabricated reference current signal and a bias signal thereof; the reference current generating circuit generates a reference current that is independent of temperature; The reference current generating circuit includes a reference voltage circuit Vbg, an operational amplifier OPA, and a resistor R1; the reference voltage circuit Vbg is connected to the operational amplifier OPA, and the operational amplifier OPA and the resistor R1 form a small closed loop connection; The readout current generating array is used to generate a pulse current signal based on a bias signal and a voltage pulse signal; The readout current generation array receives the bias voltages VB1 and VB2 and corresponds to the SPAD units one by one. Then, driven by the SPAD unit output signal Vpulse, it generates the IOUT signal. The readout current generating array corresponds to the SPAD array one-to-one, and the circuit tube size of the readout current generating array is set to a fixed value or an adjustable value; The current buffer summing circuit is used for obtaining a current pulse summing signal based on the pulse current signal; The current buffer summing circuit is a cascode structure with the M1 and R1 branches forming a negative feedback structure with the M2 and R2 branches. The transimpedance amplifier circuit is used to convert the current pulse summation signal into an output voltage signal; The post-amplifier circuit is used to amplify the voltage signal and then output it.

2. The photoelectric amplifier based on a single photon avalanche photodiode array according to claim 1, characterized in that: In the current buffer summing circuit, the IOUT signals of all SPAD pixels are fed into the IIN port of the current buffer summing circuit, where the currents are summed and IOUT is the output current after buffering.

3. The photoelectric amplifier based on a single photon avalanche photodiode array according to claim 1, characterized in that: In the transimpedance amplifier circuit, the output current of the current buffer summing circuit is input to the input port of the transimpedance amplifier circuit, and the current signal is converted into a voltage signal.

4. The photoelectric amplifier based on a single photon avalanche photodiode array according to claim 1, characterized in that: In the post-amplifier circuit, the post-amplifier circuit has a two-stage structure, the first stage is a feedback proportional amplifier, which is used to provide a set amplification proportional coefficient, and the second stage is an output buffer, which is used to provide the required driving capability.

5. The photoelectric amplifier based on a single photon avalanche photodiode array according to claim 1, characterized in that: The transimpedance amplifier circuit is a single-ended or differential structure, and the overall structure is implemented by resistor feedback, and the resistance is set to a fixed value or an adjustable value.

6. A method for operating a photoelectric amplifier based on a single-photon avalanche photodiode array, characterized in that: The photoelectric amplifier comprises: SPAD array, reference current generating circuit, readout current generating array, current buffer summing circuit, transimpedance amplifier circuit and post-amplifier circuit; SPAD array, reference current generating circuit and current buffer summing circuit are electrically connected to the readout current generating array; transimpedance amplifier circuit and post-amplifier circuit are electrically connected to the current buffer summing circuit; The operating method of the photoelectric amplifier based on the single photon avalanche photodiode array comprises the following steps: Generate voltage pulse signals through the SPAD array; A prefabricated reference current signal and a bias signal thereof are generated by a reference current generating circuit; the reference current generating circuit generates a reference current that is independent of temperature; generating a pulse current signal based on a bias signal and a voltage pulse signal by reading out a current generating array; obtaining a current pulse summation signal based on the pulse current signal through a current buffer summation circuit; The current buffer summing circuit is a cascode structure with the M1 and R1 branches forming a negative feedback structure with the M2 and R2 branches. The current pulse summation signal is converted into an output voltage signal through a transimpedance amplifier circuit; The voltage signal is amplified by the post-amplifier circuit and then output.

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