SiPM front-end circuit with background light rejection

Abstract

The application provides a SiPM front-end circuit with background light suppression, wherein the cathode of the external APD is connected with an external high-voltage power supply; the input end of a background light intensity sensing and concurrency detection threshold generation circuit is connected with the anode of the external APD, and the output end is connected with the input end of a concurrency detection circuit; the input end of an OR tree is connected with the output end of a SiPM pixel, and the output end is connected with the input end of the concurrency detection circuit; the external APD is used for sensing the background light intensity; the background light intensity sensing and concurrency detection threshold generation circuit is used for outputting a binary threshold according to the background light intensity; the SiPM pixel is used for outputting a response voltage according to a return signal; the OR tree is used for outputting a pulse sequence according to the response voltage; and the concurrency detection circuit is used for outputting a signal capable of reflecting the time information of a target return signal according to the pulse sequence and the binary threshold, so that the background light can be effectively suppressed, and the performance index of a laser radar receiver is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser radar, and particularly relates to a SiPM front-end circuit with background light suppression. BACKGROUND

[0002] LiDAR is a kind of active detection sensor device of laser, and the working principle of pulse time of flight (TOF) is roughly as follows: a laser beam is emitted by the transmitter of LiDAR, and after encountering an object, the laser beam is returned to the laser receiver through diffuse reflection, and the radar module calculates the distance between the transmitter and the object according to the time interval between the sending signal T START and the receiving signal T STOP , multiplies the time interval by the speed of light c, and then divides by 2.

[0003] Background light refers to light generated by other light sources in the environment in addition to target signal light. Especially in low light conditions or occasions requiring high sensitivity detection, when LiDAR detects a long-distance target, the return signal is weak, and the return signal is easily lost in the background light or the background light is mistakenly recognized as a target return signal, resulting in an increase in the false alarm probability of LiDAR. In order to reduce the false alarm probability of LiDAR, a technology capable of suppressing background light is urgently needed. SUMMARY

[0004] In order to solve the above problems existing in the prior art, the present application provides a SiPM front-end circuit with background light suppression, which specifically comprises:

[0005] In a first aspect, the present application provides a SiPM front-end circuit with background light suppression, which comprises:

[0006] an externally connected APD, a background light intensity sensing and concurrency detection threshold generation circuit, a SiPM pixel, an OR tree and a concurrency detection circuit; wherein

[0007] the cathode of the externally connected APD is connected to an external high-voltage power supply V HV , and the anode is connected to the input end of the background light intensity sensing and concurrency detection threshold generation circuit;

[0008] the output end of the background light intensity sensing and concurrency detection threshold generation circuit is connected to the input end of the concurrency detection circuit;

[0009] the output end of the SiPM pixel is connected to the input end of the OR tree;

[0010] the output end of the OR tree is connected to the input end of the concurrency detection circuit;

[0011] the externally connected APD is used for sensing the background light intensity and converting the sensed background light intensity value into a photoelectric current i APD ;

[0012] Background light intensity sensing and concurrent detection threshold generation circuit, used to quantize photocurrent i APD And output the binary threshold N thi ;

[0013] SiPM pixels are used to receive echo signals and process the received echo signals to output a response voltage.

[0014] An OR tree is used to receive the response voltage and output a pulse sequence V based on the response voltage. OR ;

[0015] Concurrency detection circuit, used for pulse sequence V OR After counting and binary threshold N thi The comparison is performed, and a signal reflecting the timing information of the target echo signal is output based on the comparison result.

[0016] In a second aspect, the present invention also provides a chip comprising any of the SiPM front-end circuits with background light suppression provided in the first aspect.

[0017] Thirdly, the present invention also provides a lidar receiver, comprising any of the chips provided in the second aspect.

[0018] The beneficial effects of this invention are:

[0019] The SiPM front-end circuit with background light suppression provided by this invention includes an external APD, a background light intensity sensing and concurrent detection threshold generation circuit, SiPM pixels, an OR tree, and a concurrent detection circuit; wherein, the cathode of the external APD is connected to an external high-voltage power supply V. HV The anode is connected to the input terminal of the background light intensity sensing and concurrent detection threshold generation circuit; the output terminal of the background light intensity sensing and concurrent detection threshold generation circuit is connected to the input terminal of the concurrent detection circuit; the output terminal of the SiPM pixel is connected to the input terminal of the OR tree; the output terminal of the OR tree is connected to the input terminal of the concurrent detection circuit; an external APD is connected to sense the background light intensity and convert the sensed background light intensity value into photocurrent i. APD Background light intensity sensing and concurrent detection threshold generation circuit, used to quantize photocurrent i APD And output the binary threshold N thi The SiPM pixel is used to receive the echo signal and output a response voltage after processing the received echo signal; the OR tree is used to receive the response voltage and output a pulse sequence V based on the response voltage. OR Concurrency detection circuit, used for pulse sequence V OR After counting and binary threshold N thiThe circuit compares the signals and outputs a signal that reflects the timing information of the target echo signal based on the comparison result. This circuit can effectively suppress background light, improve the performance of the lidar receiver, reduce the false alarm probability of the receiver, and improve the reliability of the lidar.

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 A schematic diagram of a SiPM front-end circuit with background light suppression provided by the present invention;

[0022] Figure 2 A schematic diagram of a background light intensity sensing and concurrent detection threshold generation circuit provided by the present invention;

[0023] Figure 3 This invention provides a schematic diagram of the structure of a SiPM pixel;

[0024] Figure 4 This is a schematic diagram of an OR tree structure provided by the present invention. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0026] The linear mode of an avalanche photodiode (APD), also known as the non-Geiger mode, is the operating state of the APD when the reverse bias voltage is lower than its avalanche breakdown voltage. In this mode, the APD linearly amplifies the incident photoelectrons, and the photocurrent is directly proportional to the incident light intensity. In Geiger mode, the output pulse height of each single-photon avalanche diode (SPAD) pixel is independent of the number of photons entering the pixel. This means that each SPAD pixel only responds to received or unreceived photons and provides echo photon information.

[0027] Based on this, the present invention provides a silicon photomultiplier (SiPM) front-end circuit with background light suppression, which determines the timing information of the target echo signal by comparing the acquired ambient light intensity and the received echo signal.

[0028] Specifically, such as Figure 1 As shown, the SiPM front-end circuit with background light suppression provided by the present invention includes:

[0029] External APD 11, background light intensity sensing and concurrent detection threshold generation circuit 12, SiPM pixel 13, OR tree 14 and concurrent detection circuit 15.

[0030] The cathode of the external APD11 is connected to an external high-voltage power supply V. HV The anode is connected to the input terminal of the background light intensity sensing and concurrent detection threshold generation circuit 12.

[0031] The output of the background light intensity sensing and concurrent detection threshold generation circuit 12 is connected to the input of the concurrent detection circuit 15.

[0032] The output of SiPM cell 13 is connected to the input of OR tree 14.

[0033] The output of OR tree 14 is connected to the input of concurrency detection circuit 15.

[0034] An external APD11 is used to sense the background light intensity and convert the sensed background light intensity value into photocurrent i. APD .

[0035] Background light intensity sensing and concurrent detection threshold generation circuit 12, used to quantize photocurrent i APD And output the binary threshold N thi .

[0036] SiPM pixel 13 is used to receive signals and output a response voltage after processing the received signals.

[0037] OR tree 14 is used to receive the response voltage and output a pulse sequence V based on the response voltage. OR .

[0038] Concurrency detection circuit 15 is used for pulse sequence V OR After counting and binary threshold N thi The comparison is performed, and a signal reflecting the timing information of the target echo signal is output based on the comparison result.

[0039] In this invention, the external APD11 operates in linear mode, ensuring that the number of photons and the response intensity are proportional within a certain range of light intensity and pulse time. The APD11 detects ambient background light, and the background light intensity sensing and concurrent detection threshold generation circuit 12 generates a binary threshold N characterizing the background light intensity. thi .

[0040] The SiPM front-end circuit with background light suppression provided by this invention can adapt to the high-sensitivity sensing echo signal of the lidar receiver under different background light conditions, and adaptively adjust the binary threshold N according to the background light intensity value. thi This reduces the false alarm rate of the lidar receiver's detected echo.

[0041] Furthermore, optional, such as Figure 2 As shown, the background light intensity sensing and concurrent detection threshold generation circuit 12 includes:

[0042] Transimpedance amplifier 121, reference voltage generation circuit 122, first comparator 123, second comparator 124 and third comparator 125.

[0043] The input terminal of the transimpedance amplifier 121 is the input terminal of the background light intensity sensing and concurrent detection threshold generation circuit 12, and is connected to the anode of the external APD 11.

[0044] The output of the transimpedance amplifier 121 is connected to the non-inverting inputs of the first comparator 123, the second comparator 124, and the third comparator 125, respectively.

[0045] The three output terminals of the reference voltage generation circuit 122 are connected to the inverting input terminals of the first comparator 123, the second comparator 124, and the third comparator 125, respectively.

[0046] The outputs of the first comparator 123, the second comparator 124, and the third comparator 125 are all outputs of the background light intensity sensing and concurrent detection threshold generation circuit 120. The signals output by the first comparator 123, the second comparator 124, and the third comparator 125 sequentially constitute a binary threshold N. thi Each value.

[0047] Furthermore, optionally, the three outputs of the reference voltage generation circuit 122 are used to output three different voltage signals.

[0048] Furthermore, optional, such as Figure 3 As shown, SiPM pixel 13 includes multiple SPAD devices and their front-end circuitry 131.

[0049] Each SPAD device and its front-end circuit 131 includes a SPAD device 1311, a quenching circuit 1312, and a pulse compression circuit 1313.

[0050] The output of SPAD device 1311 is connected to the input of quenching circuit 1312.

[0051] The output terminal of the quenching circuit 1312 is connected to the input terminal of the pulse compression circuit 1313.

[0052] The output of the pulse compression circuit 1313 is the output of the corresponding SPAD device and its front-end circuit 131.

[0053] The signal waveform after passing through SPAD device 1311, quenching circuit 1312 and pulse compression circuit 1313 is as follows:Figure 3 As shown, the SPAD device output waveform has a short rise time and a long fall time. The quenching circuit digitizes the SPAD device output waveform to obtain high and low levels, and the pulse compression circuit compresses the pulse width output by the quenching circuit, then outputs as shown. Figure 3 The narrow pulse signal shown.

[0054] SPADs offer high sensitivity for single-photon detection, but suffer from current tailing, resulting in excessively long dead time and affecting the detection of subsequent echo photons. To mitigate the impact of current tailing, a quenching circuit rapidly reduces the pulse current to shorten the dead time, and a pulse compression circuit reduces the pulse width, enabling echo photon detection to be completed within a short time window.

[0055] Furthermore, optionally, multiple SPAD devices and their front-end circuits 131 are arranged in an array structure.

[0056] In this array structure, the number of elements in each row can be the same as the number in each column, for example, an m×n array, where m≠n, or they can be different, for example, an m×m array.

[0057] Furthermore, optionally, the SiPM pixel 13 includes nine SPAD devices and their front-end circuitry 131, with the nine SPAD devices and their front-end circuitry 131 forming a 3×3 array structure.

[0058] like Figure 1 As shown, SiPM pixel 13 is used to output the response voltage V. SP1 ~V SP9 OR tree 14 is used to receive the response voltage V. SP1 ~V SP9 And output pulse sequence V OR .

[0059] This invention uses arrayed SPAD devices and their front-end circuits to realize SiPM pixels, overcoming the disadvantage of low detection efficiency of a single silicon-based SPAD device.

[0060] Furthermore, optional, such as Figure 4 As shown, the OR tree 14 includes four identical three-input OR gates: the first three-input OR gate 141, the second three-input OR gate 142, the third three-input OR gate 143, and the fourth three-input OR gate 144.

[0061] The inputs of the first three-input OR gate 141, the second three-input OR gate 142, the third three-input OR gate 143, and the fourth three-input OR gate 144 constitute the inputs of OR tree 14. That is, OR tree 14 has 9 inputs.

[0062] The outputs of the first three-input OR gate 141, the second three-input OR gate 142, and the third three-input OR gate 143 are all inputs of the fourth three-input OR gate 144.

[0063] The output of the fourth three-input OR gate 144 is the output of the OR tree 14.

[0064] pass Figure 4 The OR tree 14 shown can combine the single pulses output by SiPM pixel 13 into a pulse sequence string within a time window, which is convenient for subsequent concurrent detection circuits to count.

[0065] Furthermore, optionally, the concurrency detection circuit 15 is specifically used for: calculating the pulse sequence V OR The number of pulses N; the pulse sequence V OR The number N and the binary threshold N thi Compare, if N≤N thi Then the signal detected by SiPM pixel 13 is determined to be ambient background light, and the output signal of the concurrent detection circuit 15 is zero; if N>N thi The signal detected by SiPM pixel 13 is determined to be the target echo signal. The output signal of the concurrent detection circuit 15 changes, and the moment when the output signal of the concurrent detection circuit 15 changes is the moment information of the target echo signal.

[0066] Therefore, the input of the concurrent detection circuit 15 compares the output signal of the background light intensity sensing and concurrent detection threshold generation circuit 12 with the output signal of the OR tree 14 to determine whether the current time is the arrival time of the target echo. That is, the concurrent detection circuit 15 identifies and records the number of pulse sequences output by the OR tree 14, comparing them within a certain time window with the binary threshold N representing the background light intensity. thi By comparing the results, the effective timing information of the echo signal can be obtained.

[0067] The SiPM front-end circuit with background light suppression provided by this invention is suitable for situations where background light has a significant impact on the lidar receiver. It can effectively suppress background light, improve the performance indicators of the lidar receiver, reduce the false alarm probability of the receiver, and improve the reliability of the lidar.

[0068] The present invention also provides a chip comprising any of the SiPM front-end circuits with background light suppression as provided in the circuit embodiments described above.

[0069] The present invention also provides a lidar receiver, including any of the chips provided by the present invention.

[0070] For the chip / LiDAR receiver embodiment, since it is basically similar to the circuit embodiment, the description is relatively simple. For details and beneficial effects, please refer to the description of the circuit embodiment.

[0071] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0072] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A SiPM front-end circuit with background light rejection, characterized by, include: External APD, background light intensity sensing and concurrent detection threshold generation circuit, SiPM pixel, OR tree and concurrent detection circuit; among which, The cathode of the external APD is connected to an external high voltage power supply V HV , and the anode is connected to the input end of the background light intensity sensing and concurrency detection threshold generating circuit. The output terminal of the background light intensity sensing and concurrent detection threshold generation circuit is connected to the input terminal of the concurrent detection circuit; The output of the SiPM cell is connected to the input of the OR tree; The output of the OR tree is connected to the input of the concurrency detection circuit; The outer APD is used to perceive the background light intensity and convert the perceived background light intensity value into photocurrent i APD ; The background light intensity sensing and concurrency detection threshold generation circuit is used to quantify the photocurrent i APD and output a binary threshold N thi ; The SiPM pixel is used to receive echo signals and output a response voltage after processing the received echo signals. The OR tree is configured to receive the response voltage and output a pulse sequence V according to the response voltage OR ; The concurrence detection circuit is configured to compare the pulse sequence V OR after counting and the binary threshold N thi and output a signal capable of reflecting time information of the target echo signal according to a comparison result.

2. The circuit of claim 1, wherein, The background light intensity sensing and concurrent detection threshold generation circuit includes: The circuit consists of a transimpedance amplifier, a reference voltage generation circuit, a first comparator, a second comparator, and a third comparator, wherein: The input terminal of the transimpedance amplifier is the input terminal of the background light intensity sensing and concurrent detection threshold generation circuit, and is connected to the anode of the external APD. The output terminal of the transimpedance amplifier is connected to the non-inverting input terminals of the first comparator, the second comparator, and the third comparator, respectively. The three output terminals of the reference voltage generation circuit are respectively connected to the inverting input terminals of the first comparator, the second comparator, and the third comparator; The output terminals of the first comparator, the second comparator and the third comparator are all output terminals of the background light intensity sensing and concurrency detection threshold generation circuit, and the signals output by the first comparator, the second comparator and the third comparator sequentially constitute each bit value of the binary threshold N thi .

3. The circuit of claim 2, wherein, The three output terminals of the reference voltage generation circuit are used to output three different voltage signals.

4. The circuit of claim 3, wherein, The SiPM pixel includes multiple SPAD devices and their front-end circuitry; Any of the aforementioned SPAD devices and their front-end circuitry, including, SPAD device, quenching circuit and pulse compression circuit; The output terminal of the SPAD device is connected to the input terminal of the quenching circuit; The output terminal of the quenching circuit is connected to the input terminal of the pulse compression circuit; The output terminal of the pulse compression circuit is the corresponding output terminal of the SPAD device and its front-end circuit.

5. The circuit of claim 4, wherein, Multiple SPAD devices and their front-end circuits (131) are arranged in an array structure.

6. The circuit of claim 5, wherein, The SiPM pixel includes nine SPAD devices and their front-end circuits, which form a 3×3 array structure.

7. The circuit of claim 6, wherein, The OR tree includes: Four identical three-input OR gates are defined as the first three-input OR gate, the second three-input OR gate, the third three-input OR gate, and the fourth three-input OR gate, wherein: The input terminals of the first three-input OR gate, the second three-input OR gate, the third three-input OR gate, and the fourth three-input OR gate constitute the input terminals of the OR tree; The output terminals of the first three-input OR gate, the second three-input OR gate, and the third three-input OR gate are all input terminals of the fourth three-input OR gate; The output of the fourth three-input OR gate is the output of the OR tree.

8. The circuit of claim 7, wherein, The concurrent detection circuit is specifically used for: calculating the pulse sequence V OR the number N of pulses; The pulse sequence V OR is compared with the binary threshold N thi , if N≤N thi , the signal detected by the SiPM pixel is determined as the environmental background light, and the output signal of the concurrency detection circuit is zero; if N>N thi , the signal detected by the SiPM pixel is determined as the target echo signal, the output signal of the concurrency detection circuit jumps, and the time information of the target echo signal is the time when the output signal of the concurrency detection circuit jumps.

9. A chip, characterized by Includes the SiPM front-end circuit with background light suppression as described in any one of claims 1-8.

10. A lidar receiver, comprising: The chip as described in claim 9.

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