Front-end circuit of photodetector, photodetector array, laser radar and ranging method

Abstract

The embodiments of the present disclosure disclose a front-end circuit of a photodetector, a photodetector array, a laser radar, and a ranging method applied to the laser radar. A specific implementation of the front-end circuit of the photodetector includes a quenching module and an active recovery module, wherein the active recovery module includes an oscillation unit, and the oscillation unit is suitable for generating a pulse oscillation signal to the output end of the active recovery module under the joint action of a detection signal and a feedback signal. Thus, the photodetector is restored to a working state where photons can be detected again by the pulse oscillation signal generated by the oscillation unit included in the active recovery module.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the field of laser radar, and in particular to a front-end circuit of a photodetector, a photodetector array, a laser radar, and a ranging method applied to the laser radar. Background Art

[0002] The description in this section is limited to the understanding of the present disclosure, and does not indicate that the contents in this section are all prior art.

[0003] Single Photon Avalanche Diode (SPAD) is an avalanche photodiode (APD) that works in a special state (Geiger mode) and can detect single photons. When a certain reverse bias voltage Vbias is added to the avalanche photodiode, photons carrying energy are injected into the PN junction, which transfers energy to the electrons on the covalent bonds, causing the electrons to break free from the covalent bonds to form electron-hole pairs, also known as photogenerated carriers.

[0004] If the reverse bias voltage Vbias is large enough, the photogenerated carriers in the depletion layer can obtain high enough kinetic energy, and when colliding with the lattice, the covalent bonds can be broken to produce electron-hole pairs, which is also called impact ionization. New carriers will continue to generate new impact ionizations, forming a chain effect, causing an avalanche multiplication effect of carriers, and obtaining a very large pulse current. The minimum reverse bias voltage that can cause such an avalanche effect in SPAD is called the avalanche breakdown voltage Vbreak. The avalanche breakdown voltage is determined by the material and process of SPAD. The actual applied reverse bias voltage Vbias will be appropriately greater than the avalanche breakdown voltage Vbreak.

[0005] As a light detector, SPAD has the advantages of small size, high gain (single photon detection), high sensitivity, and high dynamic range. Therefore, its demand in applications such as light intensity detection and laser ranging is increasing.

[0006] When the single-photon avalanche diode receives a photon and generates an avalanche effect, it is necessary to quench the single-photon avalanche diode first, and then restore the reverse bias of the single-photon avalanche diode to the Geiger mode. In these applications, SPAD is usually used with a quenching circuit (making the SPAD's reverse bias voltage Vbias < avalanche breakdown voltage Vbreak) and a recovery circuit (also called a reset circuit, making the SPAD's reverse bias voltage Vbias > avalanche breakdown voltage Vbreak). Therefore, after completing one reception, the single-photon avalanche diode can receive photons again to generate an avalanche effect.

[0007] The two actions of quenching and recovery can each be an active operation or a passive operation. In this case, specifically, the quenching and recovery circuits can usually be divided into four schemes: passive quenching passive recharge (hereinafter referred to as PQPR), passive quenching active recharge (hereinafter referred to as PQAR), active quenching passive recharge (hereinafter referred to as AQPR), and active quenching active recharge (hereinafter referred to as AQAR). Quenching is usually faster and does not require active quenching. Therefore, the two more common schemes are PQPR and PQAR.

[0008] Dead-time is a key parameter of the SPAD quenching recovery circuit, which determines the dynamic range of the SPAD. Dead-time consists of the quenching phase plus the recovery phase, that is, dead-time = quenching-time (quenching) + recharge-time (recovery). Compared with PQPR, PQAR achieves a shorter recovery time due to active recovery, thus obtaining a shorter dead-time. However, the circuit structure of PQAR is more complex than that of PQPR, and the area of ​​the circuit part is larger, which is not conducive to the fill factor of the SPAD circuit. Summary of the invention

[0009] This disclosure section is provided to introduce concepts in a brief form, which will be described in detail in the detailed description section below. This disclosure section is not intended to identify key features or essential features of the claimed technical solution, nor is it intended to limit the scope of the claimed technical solution.

[0010] The embodiments of the present disclosure provide a front-end circuit of a photodetector, a photodetector array, a laser radar, and a ranging method applied to the laser radar. The photodetector is restored to a working state where it can detect photons through a pulse oscillation signal generated by an oscillation unit included in an active recovery module.

[0011] In a first aspect, an embodiment of the present disclosure provides a front-end circuit of a photodetector, which includes a quenching module and an active recovery module, wherein: the quenching module is used to quench the photodetector after the photodetector receives a photon signal and undergoes avalanche breakdown; the active recovery module has an input end and an output end both coupled to the output end of the photodetector, and the output end has a preset time delay relative to the input end, and is used to restore the photodetector to a working state for detecting photons after the quenching module quenches the photodetector; the active recovery module includes an oscillation unit, which is suitable for generating a pulse oscillation signal to the output end of the active recovery module under the joint action of a detection signal and a feedback signal, wherein the detection signal is a signal output from the photodetector after detecting a photon, and the feedback signal is a signal output from the output end of the oscillation unit after the oscillation unit inputs the signal output by the photodetector when detecting the last photon.

[0012] In a second aspect, an embodiment of the present disclosure provides a photodetector array, which includes a two-dimensional photodetector array, and the two-dimensional photodetector array includes a predetermined number of photodetector modules. Each detector module includes a photodetector. For each photodetector, it is connected to the front-end circuit of the photodetector described in the first aspect. After the photodetector is selected, the photodetector operates in a state where an echo signal can be detected. When the photodetector receives an echo signal, it outputs an electrical signal corresponding to the echo signal. The photodetector is quenched by a quenching module, and is restored to a state where an echo signal can be detected by an active recovery circuit to detect the next echo signal.

[0013] In a third aspect, an embodiment of the present disclosure provides a laser radar, which includes a laser array, a photodetector array as described in the second aspect, a front-end circuit corresponding to each photodetector in the photodetector array, and a signal readout circuit. Each laser in the laser array is used to emit a detection signal for detecting a detection object when the laser is driven. The photodetector array includes a two-dimensional photodetector array, and the two-dimensional photodetector array includes a predetermined number of photodetector modules. Each detector module includes a photodetector. For each photodetector, after the photodetector is selected, the echo signal returned after the detection signal encounters the detection object is received, wherein the active recovery module of the front-end circuit of the photodetector restores the photodetector to a state where the echo signal can be detected when the oscillation unit outputs the oscillation signal; when the photodetector receives the echo signal, the electrical signal corresponding to the echo signal is output to the signal readout circuit for calculating the distance of the detection object; the photodetector is quenched by the quenching module, and the active recovery circuit is restored to a state where the echo signal can be detected to detect the next echo signal.

[0014] In a fourth aspect, an embodiment of the present disclosure provides a ranging method applied to the laser radar described in the third aspect above, and the ranging method includes: using a control circuit to output a first drive signal to drive the laser in the laser array of the laser radar to emit a detection signal, and recording a first time when the detection signal is emitted; when the detection signal encounters a detection object in space, an echo signal will be generated; using the control circuit to output a second drive signal to drive a photodetector in a photodetector array that matches the laser, and the photodetector works in a detectable echo signal state under the action of its front-end circuit; in the detectable echo signal state, when the photodetector receives the echo signal, it outputs an electrical signal corresponding to the echo signal to the signal readout circuit; using the signal readout circuit to read the electrical signal, and recording a second time when the electrical signal is read out; based on the first time and the second time, determining the distance between the laser radar and the detection object.

[0015] In the related art, when the photodetector continuously receives photons, a large breakdown current is generated in the photodetector, resulting in quenching failure of the photodetector, thereby causing the photodetector to be unable to effectively continue to detect subsequent photons.

[0016] In another related technology, the active recovery module includes multiple recovery branches for restoring the photodetector to a working state where it can receive photons. Therefore, the complexity of the active recovery module is increased, and even the area of ​​the active recovery module is increased. Generally, the larger the area of ​​the active recovery module, the lower the efficiency (PDE) of the photodetector in detecting photons.

[0017] The front-end circuit of the photodetector, the photodetector array, the laser radar and the ranging method applied to the laser radar provided by the embodiments of the present disclosure quench the photodetector through a quenching module after the photodetector detects avalanche breakdown of photons. After quenching, the active recovery module automatically restores the photodetector to a working state capable of detecting photons under the action of a pulse oscillation signal generated by an oscillation unit included therein. On the one hand, the pulse oscillation signal generated by the oscillation unit can improve the ability of the photodetector to continuously detect photons. On the other hand, without adding an additional recovery branch to the active recovery module, the photodetector is restored to a working state capable of detecting photons, thereby improving the ability of the photodetector to continuously detect photons. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and the originals and elements are not necessarily drawn to scale.

[0019] Figure 1 is a structural diagram of some embodiments of the front-end circuit of the photodetector according to the present disclosure;

[0020] Figure 2A and Figure 2B They are structural diagrams of some further embodiments of the front-end circuit of the photodetector according to the present disclosure;

[0021] Figure 3 is a structural diagram of some embodiments of the front-end circuit of the photodetector according to the present disclosure;

[0022] Figure 4A and Figure 4B They are structural diagrams of some embodiments of the oscillation unit according to the present disclosure;

[0023] Figure 5 is a structural diagram of some embodiments of the front-end circuit of the photodetector according to the present disclosure;

[0024] Fig. 6A and Figure 6B is a circuit timing diagram of some embodiments of the front-end circuit of the photodetector according to the present disclosure;

[0025] Figure 7 is a circuit simulation diagram of some embodiments of the front-end circuit of the photodetector according to the present disclosure;

[0026] Fig. 8A and Figure 8B They are structural diagrams of some embodiments of the front-end circuit of the photodetector according to the present disclosure;

[0027] Fig. 9 is a structural diagram of some embodiments of the front-end circuit of the photodetector according to the present disclosure;

[0028] Fig. 10A and Fig. 10B They are structural diagrams of some embodiments of the oscillation unit according to the present disclosure;

[0029] Fig.11A is a functional structure diagram of a laser radar according to some embodiments of the present disclosure;

[0030] Fig. 11B is a schematic diagram of the structure of a laser radar according to some embodiments of the present disclosure;

[0031] Fig.12 is a schematic diagram of a process in which a photoelectric detector array and a laser array included in a laser radar in some embodiments of the present disclosure interact to achieve obstacle distance detection;

[0032] Fig.13 is a flow chart of some embodiments of the ranging method applied to laser radar according to the present disclosure;

[0033] Fig.14 is a circuit block diagram for outputting an electrical signal to a signal readout circuit according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0034] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as being limited to the embodiments described herein, which are instead provided for a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not intended to limit the scope of protection of the present disclosure.

[0035] It should be understood that the various steps described in the method embodiments of the present disclosure may be performed in different orders and / or in parallel. In addition, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present disclosure is not limited in this respect.

[0036] The term "including" and its variations used herein are open inclusions, i.e., "including but not limited to". The term "based on" means "based at least in part on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The relevant definitions of other terms will be given in the following description.

[0037] It should be noted that the concepts such as "first" and "second" mentioned in the present disclosure are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0038] It should be noted that the modifications of "one" and "plurality" mentioned in the present disclosure are illustrative rather than restrictive, and those skilled in the art should understand that unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0039] Please refer to Figure 1 , which shows a structural diagram of some embodiments of the front-end circuit of the photodetector according to the present disclosure. Figure 1 As shown, the structure diagram includes a quenching module 10 and an active recovery module 20.

[0040] In this embodiment, the quenching module 10 is used to quench the photodetector after the photodetector receives a photon signal and undergoes avalanche breakdown. The input end and the output end of the active recovery module 20 are both coupled to the output end of the photodetector. The output end of the active recovery module 10 has a preset time delay relative to its input end, and is used to restore the photodetector to a working state where photons can be detected again after the quenching module 10 quenches the photodetector. The active recovery module 20 includes an oscillation unit 30. The oscillation unit 30 forms a closed loop, and the output signal will be used as one of the input signals and input to the input end together, and is suitable for generating a pulse oscillation signal under the joint action of a detection signal (from one of the input ends) and a feedback signal (as another input end, from the output end, with a certain time delay relative to the detection signal from one of the input ends), and the pulse oscillation signal is transmitted to the output end of the active recovery module 20 to adjust the working state of the photodetector, specifically, to adjust the reverse bias voltage of the photodetector to be greater than the breakdown voltage, so that it can work in the Geiger mode again, and effectively detect photons when the next photon arrives. The detection signal is a signal outputted from the photodetector after detecting the current (e.g., nth) photon. The feedback signal is a signal outputted from the output end of the oscillation unit 30 after the oscillation unit 30 receives the detection signal outputted by the photodetector after detecting the last (e.g., n+1th) photon.

[0041] Usually, the signal receiving end of the laser radar can use a photodetector to receive the echo signal returned when the detection signal sent by the transmitting end encounters an external object. When the photodetector is in working state, it can detect the echo signal, and then by analyzing the echo signal, it can obtain information such as the distance and reflectivity of the external object.

[0042] In practical applications, when the applied reverse bias voltage is greater than or equal to the avalanche breakdown voltage, the photodetector operates in a working state where photons can be detected.

[0043] As an implementation method, the above-mentioned photodetector may include, for example, a SPAD(s). When a certain reverse bias is applied to the SPAD(s), photons carrying energy are injected into the PN junction of the SPAD(s), which transfers energy to electrons on the covalent bonds, thereby causing the electrons to break free from the covalent bonds to form electron-hole pairs, that is, to form photogenerated carriers. When the reverse bias of the SPAD is large enough, the photogenerated carriers in the depletion layer can obtain sufficiently high kinetic energy, and when colliding with the lattice, the covalent bonds can be broken to generate electron-hole pairs. New carriers will continuously generate new impact ionizations, resulting in an avalanche multiplication effect of carriers, thereby forming a very large pulse current.

[0044] If the photodetector generates a large pulse current for a long time, the device may be damaged and unable to detect subsequent photons. Therefore, when the photodetector detects photons and generates a large pulse current, the photodetector can be quenched by the quenching module 10.

[0045] After quenching, the reverse bias voltage of the photodetector is usually less than the avalanche breakdown voltage. At this time, the photodetector is not working in a working state where photons can be detected. That is, the photodetector cannot detect photons. Therefore, after quenching, the photodetector can be restored to a working state where photons can be detected again by the active recovery module 20.

[0046] Specifically, after the photodetector undergoes avalanche breakdown upon receiving a photon, the generated detection signal can be transmitted to the active recovery module 20. The active recovery module 20 can transmit the received signal to the oscillation unit 30. The oscillation unit 30 can restore the photodetector to a working state where it can detect photons again based on the signal generated by the photodetector at that time and the feedback signal output from its output end after the photon signal was detected last time.

[0047] In this embodiment, when the photodetector detects that a photon has undergone avalanche breakdown, the photodetector is quenched by the quenching module. After quenching, the photodetector is automatically restored to a working state where photons can be detected again under the action of a pulse oscillation signal generated by an oscillation unit included in the active recovery module, thereby avoiding quenching failure and improving the ability of continuous detection.

[0048] See also Figure 2A and Figure 2B , which shows a structural diagram of some embodiments of the front-end circuit of the photodetector according to the present disclosure. Figure 1The same quenching module, photodetector, and active recovery module are also included.

[0049] exist Figure 2A In the embodiment shown, the quenching module 10 is coupled to the voltage supply terminal at one end and to the output terminal of the photodetector at the other end, and the anode of the photodetector is connected to the low potential. The cathode of the photodetector is coupled to the other end of the quenching module 10 as the output terminal of the detection signal. The oscillation unit 30 includes a NAND gate 301 and a delay unit 303. The first input terminal of the NAND gate 301 is coupled to the input terminal of the active recovery module 20 as the input terminal of the entire oscillation unit 30, the second input terminal of the NAND gate 301 is connected to the output terminal of the oscillation unit 30 for inputting the last output signal (also called feedback signal) of the oscillation unit 30, and the output terminal of the NAND gate 301 is coupled to the input terminal of the delay unit 303. The output terminal of the delay unit 303 is transmitted to the photodetector as the output terminal of the oscillation unit 30 to adjust the reverse bias voltage of the photodetector.

[0050] exist Figure 2B In the embodiment shown, Figure 2A Based on the front-end circuit shown, the oscillation unit 30 further includes an odd number of first inverters 302. The output end of the NAND gate 301 is connected to the input end of the first inverter 302. The output end of the first inverter 302 is coupled to the input end of the delay unit 303.

[0051] Here, a reverse bias is applied to the photodetector by applying a low potential to the anode of the photodetector. It should be noted that the low potential may be a potential lower than a predetermined potential. In some scenarios, the low potential may be grounded. Accordingly, the high potential may be a potential higher than a predetermined potential, that is, the high potential is higher than the low potential.

[0052] That the oscillation unit 30 includes one first inverter 302 is only one implementation manner. In other implementation manners, the oscillation unit 30 may include an odd number of first inverters 302 , such as 3 or 5 first inverters.

[0053] The delay unit 303 can delay the input signal. Optionally, the delay unit 303 can also include an odd number of inverters (for example, the delay unit 303 includes a fourth inverter) to invert the signal. In addition, the odd number of inverters additionally included in the delay unit 303 can also be used as part of the oscillation unit, so that the entire oscillation unit includes an even number of inverters in addition to the NAND gate.

[0054] Figure 2AIn the front-end circuit shown, the active recovery module 20 restores the photodetector to a working state capable of detecting photons through the NAND gate 301 and the delay unit 303 included in the oscillation unit 30 . Figure 2B In the front-end circuit shown, the active recovery module 20 restores the photodetector to a working state capable of detecting photons through the NAND gate 301 , the first inverter 302 and the delay unit 303 included in the oscillation unit 30 . Figure 2A and Figure 2B The front-end circuit shown in FIG. 1 uses a similar method to restore the photodetector to a working state where it can detect photons. Figure 2B Taking the front-end circuit shown as an example, it describes how the front-end circuit restores the photodetector to a working state where it can detect photons.

[0055] Specifically, when the photodetector detects that a photon has undergone avalanche breakdown, the generated signal can be transmitted to the input end of the active recovery module 20. The above signal can be transmitted to the first input end of the NAND gate 301 inside the active recovery module. The second input end of the NAND gate 301 can output the feedback signal output after the photodetector detected the photon last time. The output end of the NAND gate 301 outputs a signal to the first inverter 302 based on the signal input from the first input end and the feedback signal fed back from the second input end. The signal output from the output end of the NAND gate 301 is inverted by the first inverter 302, and then delayed (or delayed and inverted) by the delay unit 303, and finally transmitted to the output end of the oscillation unit 30. The signal output from the output end of the oscillation unit 30 can control the active recovery module to output an electrical signal that puts the photodetector in a working state.

[0056] Thus, the photodetector is restored to a working state capable of detecting photons through the signal output by the oscillation unit 30 included in the active recovery module 20 .

[0057] Figure 2BThe NAND gate 301, the first inverter 302 and the delay unit for realizing the oscillation unit are added. The first inverter 302, the delay unit 303 and the NAND gate 301 constitute a monostable circuit. The monostable circuit is a basic pulse unit circuit with two working states: steady state and transient state. When there is no external signal trigger, the circuit is in a steady state. Under the trigger of the external signal, the circuit flips from the steady state to the transient state, and after a period of time, the circuit automatically returns to the steady state. The NAND gate 301 will output a low level 0 only when both inputs are high level 1, and the output is high level 1 at other times. The signal of node B is directly input to the first input terminal of the NAND gate 301, and the signal of node B is input to the first inverter 302 after passing through the NAND gate 301 and inverted again. The signal of node B after being inverted again is input to the delay unit 303, and after a certain delay in the delay unit 303, it is inverted again and input to the second input terminal of the NAND gate 301. The signal input to the first input terminal of the NAND gate 301 is different from the signal input to the second input terminal. In addition, there is a time difference between the state change of the signal input to the second input terminal and the signal input to the first input terminal. Therefore, the output of the NAND gate 301 is sometimes 1 and sometimes 0, and it will jump. This can ensure that the output of node D is a pulse signal (that is, a signal with jumps. For example, when quenching has not been completed, the voltage of node D is originally 0. After the output of the monostable circuit, that is, the NAND gate 301, is 1, the voltage change constitutes a negative pulse, for example, Figure 6B Under the action of the above pulse signal (relative to the state of always maintaining a low level, the pulse signal is a jumping signal), the active recovery module 20 can output a signal that makes the detector in a working state where photons can be detected, rather than being unable to be quenched.

[0058] Reference below Figure 3 , describing some implementations of the above-mentioned front-end circuit when a low potential is applied to the anode of the photodetector and a reverse bias is applied to the photodetector.

[0059] In some embodiments, the active recovery module 20 further includes a second switch unit 60. The second switch unit 60 includes a control signal input terminal, a high level signal input terminal and a signal output terminal. The control signal input terminal is coupled to the output terminal of the oscillation unit 30. The high level signal input terminal is connected to the high level signal supply terminal. The signal output terminal is connected to the output terminal of the active recovery module 20.

[0060] like Figure 3 As shown, the second switch unit 60 may be a PMOS tube, the gate of which may be a control signal input terminal, the source of which may be a high level signal input terminal, and the drain of which may be a signal output terminal.

[0061] Typically, the second switch unit 60 is turned on or off by controlling the signal at the signal input terminal, and the photodetector is restored to a working state capable of detecting photons by the signal at the signal output terminal.

[0062] In some embodiments, the active recovery module 20 further includes a second inverter 305 and a third inverter 306. The input end of the second inverter 305 is connected to the output end of the oscillation unit 30, and the output end of the second inverter 305 is connected to the input end of the third inverter 306. The output end of the third inverter 306 is connected to the control signal input end of the second switch unit 60.

[0063] In some scenarios, the signal output by the oscillation unit 30 is a ramp signal, and the output signal of the oscillation unit 30 can be shaped into a digital signal through the second inverter 305 and the third inverter 306. Therefore, the signal output by the oscillation unit 30 is first shaped by the second inverter 305 and the third inverter 306, and then the opening and closing of the second switch unit 60 is controlled by the shaped signal.

[0064] In some embodiments, the delay unit 303 includes a fourth inverter 3031, a delay capacitor 3032 and a delay resistor 3033. The delay unit 303 is used to provide a delay. The size of the delay of the delay unit 303 is related to the product of the delay capacitor 3032 and the delay resistor 3033. The fourth inverter 3031 is used to invert the signal input at the input end. The input end of the fourth inverter 3031 is connected to the input end of the delay unit 303, and the output end of the fourth inverter 3031 and the first electrode of the delay capacitor 3032 are connected to the output end of the delay unit 303. The second electrode of the delay capacitor 3032 is connected to a low voltage. One end of the delay resistor 3033 is connected to the power supply end, and the other end is coupled to the fourth inverter 3031.

[0065] The delay of the delay unit 303 may be, for example, recharge-time=f(R x C), where recharge-time represents the delay of the delay unit 303, f represents the delay function, R represents the resistance value of the delay resistor 3033, and C represents the capacitance value of the delay capacitor 3032. Thus, the input signal of the oscillation unit 30 is first delayed by the delay circuit formed by the delay capacitor 3032 and the delay resistor 3033, and then the delayed signal is output to the output end of the oscillation unit.

[0066] In some embodiments, the active recovery module 20 further includes an inverting unit 40. The input end of the oscillation unit 30 is connected to the output end of the inverting unit 40, and the input end of the inverting unit 40 is coupled to the input end of the active recovery module 20. The inverting unit 40 may be a unit for inverting an input signal. The inverting unit 40 includes a first PMOS tube 401 and a first NMOS tube 402.

[0067] like Figure 3 As shown, the gate of the first PMOS tube 401 and the gate of the first NMOS tube 402 are connected to the input end of the inverting unit 40, the drain of the first PMOS tube 401 and the drain of the first NMOS tube 402 are connected to the output end of the inverting unit 40, the source of the first PMOS tube 401 is connected to a high potential, and the source of the first NMOS tube 402 is connected to a low potential.

[0068] Therefore, the signal output by the photodetector is first inverted by the inverting unit 40 , and then the inverted signal is input to the oscillating unit 30 .

[0069] When a reverse bias is applied to the photodetector by applying a low potential to the anode of the photodetector, Figure 2A , Figure 2B and Figure 3 The oscillation unit 30 shown in FIG. 1 may also have other embodiments.

[0070] In some embodiments, the oscillation unit 30 further includes a second inverter 305 and a third inverter 306. The input end of the second inverter 305 is connected to the output end of the first inverter 302, the output end of the second inverter 305 is connected to the input end of the third inverter 306, and the output end of the third inverter 306 is connected to the input end of the delay unit 303.

[0071] In some cases, see Figure 4A As shown in the structural diagram of the oscillation unit 30, the delay unit 303 may include a fourth inverter 3031, a delay capacitor 3032 and a delay resistor 3033. Here, the first electrode of the delay capacitor 3032 is connected to the output end of the delay unit 303, and the second electrode of the delay capacitor 3032 is connected to the low potential. One end of the delay resistor 3033 is connected to the low potential, and the other end is coupled to the fourth inverter 3031. The input end of the fourth inverter 3031 is connected to the output end of the third inverter 306 as the input end of the delay unit 303, and the output end of the fourth inverter 3031 is connected to the output end of the oscillation unit 30 as the output end of the delay unit 303.

[0072] In some embodiments, the oscillation unit 30 further includes a second inverter 305 and a third inverter 306. The input end of the second inverter 305 is connected to the output end of the delay unit 303, the output end of the second inverter 305 is connected to the input end of the third inverter 306, and the output end of the third inverter 306 is connected to the second input end of the NAND gate 304 as the output end of the oscillation unit 30.

[0073] In some cases, see Figure 4BAs shown in the structural diagram of the oscillation unit 30, the delay unit 303 may include a fourth inverter 3031, a delay capacitor 3032 and a delay resistor 3033. Here, the first electrode of the delay capacitor 3032 is connected to the output end of the delay unit 303, and the second electrode of the delay capacitor 3032 is connected to the low potential. One end of the delay resistor 3033 is connected to the low potential, and the other end is coupled to the fourth inverter 3031. The input end of the fourth inverter 3031 is connected to the output end of the first inverter 302 as the input end of the delay unit 303, and the output end of the fourth inverter 3031 is connected to the input end of the second inverter 305 as the output end of the delay unit 303.

[0074] It should be noted that in Figure 3 In the front-end circuit shown, each PMOS transistor and NMOS transistor included in the active recovery module can be placed in a deep well (DNW), so that the voltage domain of all devices in the active recovery module becomes higher, thereby eliminating the coupling capacitor required for high and low voltage switching.

[0075] The following combination Figure 3 , Fig. 6A and Figure 6B , introducing the specific working process of the circuit in the present application: at the beginning, the whole circuit is in an initial state, the high potential → quenching module 10 → photodetector → low potential path is not conductive, the node S is a high potential HV, the reverse bias voltage Vbias of the photodetector = HV > breakdown voltage Vbreak (the photodetector is in Geiger mode, that is, the voltage drop on the photodetector is greater than the breakdown voltage, also called the over-breakdown voltage region), the second switch unit 60 is cut off, and the node D is a high level.

[0076] Quenching process: Once the photodetector is stimulated by photon 1 and breaks down, the potential of node S is quickly pulled down (the photodetector generates a large current I, the voltage drop on the quenching module 10 is large, and the potential of node S V = HV-Rq×I). When the potential is pulled down to near the breakdown voltage VBD of the photodetector, the photodetector breaks down and the quenching ends. This falling edge of node S is the quenching process.

[0077] Recovery process: Node A and node S are coupled through capacitor C1, so node A changes closely with node S. This falling edge is flipped successively through the inverter and NAND gate 301 and the second inverter 302, and will be transmitted to the delay unit 303, and enter the feedback branch of node C→node D→drain end of the second switch unit 60, and then the node C node is slowly dropped through RC discharge. When the potential of node C drops to a certain value, node D is pulled to a low potential after the second inverter 305 and the third inverter 306 are flipped successively. The falling edge of node D is transmitted to the gate end of the second switch unit 60, so that the second switch unit 60 is turned on. The second switch unit 60 is generally a device of a larger size, and the node S node can be quickly pulled up to a high potential through HV, thereby quickly restoring the photodetector to the Geiger mode. The rising edge of node S is the recovery stage. The rising edge of node S will also be transmitted back to node D through the loop, so that the potentials of all nodes are restored to the initial state. Thus, the active recovery module 20 can receive the trigger of the next photon.

[0078] Further reference below Figure 5 , describing some implementations of the above-mentioned front-end circuit when a low potential is applied to the anode of the photodetector and a reverse bias is applied to the photodetector.

[0079] In some embodiments, the active recovery module 20 in the front-end circuit further includes a first initial potential setting unit 50. The first initial potential setting unit 50 includes a first capacitor 501 and a first switch unit 502. The input end of the first initial potential setting unit 50 is connected to the input end of the active recovery module 20. One electrode of the first capacitor 501 is connected to the input end of the first initial potential setting unit 50. The other electrode of the first capacitor 501 is connected to the output end of the first initial potential setting unit 50, and the other electrode of the first capacitor 501 is connected to the output end of the first switch unit 502. The output end of the first initial potential setting unit 50 is connected to the input end of the inverting unit 40.

[0080] like Figure 5 As shown, the first switch unit 502 may be a PMOS tube, the gate of which is connected to a low potential, the source of which is connected to a high potential, and the drain of which serves as the output end of the first switch unit 502 .

[0081] In practical applications, the first initial potential setting unit 50 can couple the signal at its input end and the signal at its output end through the first capacitor 501 included therein. Thus, when the first initial potential setting unit 50 is set between the high voltage region and the low voltage region, the high potential in the high voltage region can be slowly transitioned to the low voltage region. In this way, the isolation of the high voltage domain and the low voltage domain can be achieved, ensuring the normal operation of the device in the low voltage domain.

[0082] In some embodiments, the active recovery module 20 in the front-end circuit further includes a second initial potential setting unit 70. The second initial potential setting unit 70 includes a second capacitor 701 and a third switch unit 702. The input end of the second initial potential setting unit 70 is coupled to the output end of the oscillation unit 30. One electrode of the second capacitor 701 is connected to the input end of the second initial potential setting unit 70. Another electrode of the second capacitor 701 is connected to the output end of the second initial potential setting unit 70, and another electrode of the second capacitor 701 is connected to the output end of the third switch unit 702.

[0083] It should be noted that the functions of the second initial potential setting unit 70 and the first initial potential setting unit 50 are similar and will not be described in detail herein.

[0084] In some embodiments, the active recovery module 20 includes a second inverter 305 and a third inverter 306. The input end of the second inverter 305 is connected to the output end of the oscillation unit 30, and the output end of the second inverter 305 is connected to the input end of the third inverter 306. The output end of the third inverter 306 is connected to the input end of the second initial potential setting unit 70.

[0085] In a specific implementation, the quenching module 10 can be a quenching resistor for passive quenching (generally speaking, the quenching resistor is positively correlated with the reverse resistance of the photodetector). The second switch unit 60 is a PMOS tube for active recovery. The node OUT is used to output a detection signal. When an avalanche breakdown occurs, an avalanche signal (detection signal) appears on the quenching module 10. The output detection signal passes through the amplification module and is then sent to the signal comparison circuit. When the pulse is determined to be higher than the set threshold value (th) in the signal comparison circuit, it is determined to be a valid photon number and is counted by the counting circuit (for example, Fig.14 The counting circuit 1402 shown in FIG. 1 can then measure parameters such as obstacle distance and reflectivity.

[0086] The feedback branch from the output node OUT to the node D and then to the drain of the second switch unit 60 is used to delay the dead-time of the photodetector by restoring the reverse bias voltage Vbias of the photodetector to a state where it can receive photons again. Here, dead-time = quenching-time + recharge-time, where quenching-time represents the time for quenching the photodetector, and recharge-time represents the time for actively recovering the photodetector. The above feedback branch controls the active recovery time recharge-time of the photodetector, and its size is mainly determined by the RC time constant of the resistance R of the delay capacitor 3032 and the capacitance C of the delay resistor 3033.

[0087] It should be noted that due to Figure 5 The photodetector structure used is one in which the anode is connected to a low potential, and the cathode is connected to a higher breakdown high voltage domain HV, so the first capacitor 501 and the second capacitor 701 are needed to isolate the high and low voltage domains, thereby ensuring the reliability of the low voltage domain devices, the first switch unit 502, the first PMOS tube 401 and the first NMOS tube 40 and all gate circuits. However, the second switch unit 60 and the third switch unit 702 need to use high voltage devices (such as LDMOS) that can withstand high voltage, or use a deep well process (PMOS+DNW, DNW is a deep N well isolation structure, Deep N-WELL, there is another layer of N-injection under NWELL) to isolate the high voltage. Of course, the second switch unit 60, the first switch unit 502, the first switch unit 502, the first PMOS tube 401 and the first NMOS tube 40 can also use high voltage devices to expand the working voltage range of the photodetector. The role of the first switch unit 502 and the third switch unit 702 is to provide an initialization voltage bias for the capacitively coupled node A and node D.

[0088] See below Fig. 6A and Figure 6B , which shows Figure 5 The circuit timing diagram of the front-end circuit shown responds to photons detected by the photodetector. Figure 7 yes Figure 5 The circuit simulation diagram of the front-end circuit responding to the photons detected by the photodetector is shown below. Figure 3-Figure 7 , describe the working principle of the front-end circuit.

[0089] like Fig. 6A As shown, when the photodetector does not receive a photon, the quenching module 10 and the branch where the photodetector is located are not conducting, and a high potential is formed at node S. At this time, the reverse bias voltage of the photodetector is greater than the breakdown voltage, and it is in a working state where photons can be detected. The second switch unit 60 is cut off, and accordingly, a high potential is formed at node D. The high potential of node S is coupled by the first initial potential setting unit 50 to form a high potential at node A that is almost the same as that of node S. The high potential of node A is inverted by the inverting unit 40 to form a low potential at node B. The low potential of node B is subjected to the action of the NAND gate 301, the first inverter 302 and the delay unit 303 to form a high potential at node C.

[0090] like Fig. 6A and Figure 6BAs shown, when the photodetector receives photon 1 and undergoes avalanche breakdown, the quenching module 10 and the branch where the photodetector is located are turned on, thereby pulling down the potential of node S. When the potential of node S is pulled down to a level close to the breakdown voltage of the photodetector, the quenching of the photodetector ends. This process is the quenching process in which the quenching module 10 quenches the avalanche breakdown of the photodetector after receiving photon 1. This quenching process is embodied as follows: Fig. 6A and Figure 6B The falling edge shown is formed after receiving photon 1.

[0091] The low potential of node S is coupled by the first initial potential setting unit 50, and a low potential almost similar to that of node S is formed at node A. The low potential of node A is inverted by the inverting unit 40, and a high potential is formed at node B. The high potential of node B and the high potential formed at node C last time are subjected to the action of the NAND gate 301, the first inverter 302 and the delay unit 303, and a low potential is formed at node C. Under the discharge action of the delay unit 303, node C slowly drops from the high potential output last time to a low potential. When the potential of node C drops to a certain value, a low potential is formed at node D after the shaping of the inverter 305 and the inverter 306. The low potential of node D is coupled by the second initial potential setting unit 70 and transmitted to the gate of the third switch unit 702. At this time, the third switch unit 702 is turned on.

[0092] After being turned on, the third switch unit 702 can pull the potential of the node S to a high potential. Thus, the reverse bias voltage of the photodetector is restored to a value greater than the breakdown voltage. This recovery process is reflected as follows: Fig. 6A and Figure 6B The rising edge between t1 and t2 shown. The potential of node S during the recovery process is transmitted to node D through nodes A, B, and C. At this time, the potential of each node is restored to the initial state when no photon is received, and the front-end circuit can receive the trigger of the next photon.

[0093] Specifically, the NAND gate 301, the first inverter 302 and the fourth inverter 3031 can form a ring oscillation circuit. When the input (that is, node B) of the oscillation unit 30 is a low potential 0, the output (that is, node C) is a high potential 1, and when the input of the oscillation unit 30 is a high potential 1, the output is a low potential 0. It can be seen that the potential of the output end (that is, node C) of the oscillation unit 30 jumps and oscillates between 0 and 1. As a result, the potential of node D will oscillate and switch between high and low levels without maintaining a low level. When the potential of node D is cut to a high level, the photodetector can be successfully restored to a working state where photons can be received. When the potential of node D is switched to a low level, the photodetector will undergo an active recovery process again and quickly recover to a reverse bias voltage greater than the breakdown voltage. Until a low potential is formed at node B, a high potential can be formed at node D. At this time, the second switch unit 60 is turned off, the oscillation process of the oscillation unit 30 ends, and each node is restored to a working state where photons can be received. It should be noted that the change process of the potential formed at each node when the front-end circuit receives photon 1 and photon 2 can also be seen in Figure 7 The circuit simulation diagram is shown.

[0094] It should be noted that Fig. 6A , Figure 6B and Figure 7 The node OUT shown in the figure may be a node corresponding to the potential formed after the potential of the node B is processed by the buffer. That is, the input end of the buffer is connected to the node B, and the output end is connected to the node OUT.

[0095] Based on the above analysis, it is not difficult to find that the active recovery module 20 recorded in the present application controls the opening and closing of the second switch unit 60 by switching the potential output by the oscillation unit 30 between high and low levels. That is, the recovery process of the photodetector by the active recovery module 20 depends on the opening and closing of the second switch unit 60 without adding additional devices. Therefore, after the quenching module 10 quenches the photodetector, the photodetector can be restored to a working state where it can detect photons again relatively quickly.

[0096] In a specific implementation, when the quenching is completed and the node D is switched to a low level, the photodetector will undergo an active recovery process and quickly recover to the over-breakdown voltage. Then the node B recovers to a low level and the oscillation ends. The actual oscillation only causes the node D to increase a negative pulse once. The recovery time is very short because the recovery process depends on the opening and closing of the second switch unit 60. Therefore, the continuous detection capability of the photodetector can be improved, and no additional devices are added, so the fill factor can be improved.

[0097] In practical applications, the flip voltage of the NAND gate 301 may be lower than the flip voltage of the second inverter 305 , and the NAND gate 301 reacts slower than the second inverter 305 , which ensures that the oscillation occurs after normal active recovery.

[0098] See also Fig. 8A and Figure 8B , which shows a structural diagram of some embodiments of the front-end circuit of the photodetector according to the present disclosure. Figure 1 The same quenching module, photodetector, and active recovery module are also included.

[0099] exist Fig. 8A In the illustrated embodiment, the quenching module 10 is coupled to the voltage supply terminal at one end and to the output terminal of the photodetector at the other end. The cathode of the photodetector is connected to a high potential. The anode of the photodetector is used as an output terminal and is coupled to the other end of the quenching module 10. The oscillation unit 30 includes a NOR gate 304 and a delay unit 303. The first input terminal of the NOR gate 304 is used as the input terminal of the oscillation unit 30 and is coupled to the input terminal of the active recovery module 20. The second input terminal of the NOR gate 304 is connected to the output terminal of the oscillation unit 30 for inputting the last output signal of the oscillation unit 30. The output terminal of the NOR gate 304 is connected to the input terminal of the delay unit 303. The output terminal of the delay unit 303 is used as the output terminal of the oscillation unit 30.

[0100] exist Figure 8B In the embodiment shown, Fig. 8A Based on the front-end circuit shown in FIG. 1 , the oscillation unit 30 further includes an odd number of first inverters 302 . The output end of the delay unit 303 is connected to the input end of the first inverter 302 . The output end of the first inverter 302 serves as the output end of the oscillation unit 30 .

[0101] Here, a reverse bias is applied to the photodetector by applying a high potential to the cathode of the photodetector.

[0102] Fig. 8A In the front-end circuit shown, the active recovery module 20 restores the photodetector to a working state capable of detecting photons through the NOR gate 304 and the delay unit 303 included in the oscillation unit 30 . Figure 8B In the front-end circuit shown, the active recovery module 20 restores the photodetector to a working state capable of detecting photons through the NOR gate 304 , the first inverter 302 and the delay unit 303 included in the oscillation unit 30 .

[0103] Fig. 8A and Figure 8B The front-end circuit shown in FIG. 1 uses a similar method to restore the photodetector to a working state where it can detect photons. Figure 8BTaking the front-end circuit shown as an example, it describes how the front-end circuit restores the photodetector to a working state where it can detect photons.

[0104] Specifically, when the photodetector detects that a photon has undergone avalanche breakdown, the generated signal can be transmitted to the first input end of the NOR gate 304. The second input end of the NOR gate 304 can output the feedback signal output by the photodetector after the photon was detected last time. The output end of the NOR gate 304 outputs a signal to the first inverter 302 based on the signal input from the first input end and the feedback signal fed back from the second input end. The signal output from the output end of the NOR gate 304 is inverted by the first inverter 302, delayed (or delayed and inverted) by the delay unit 303, and output to the output end of the oscillation unit 30. Thus, the photodetector is restored to a working state where photons can be detected by the signal output by the oscillation unit 30 included in the active recovery module 20.

[0105] Reference below Fig. 9 , describing some implementations of the above front-end circuit when a high potential is applied to the cathode of the photodetector and a reverse bias is applied to the photodetector.

[0106] In some embodiments, the active recovery module 20 further includes a fourth switch unit 80. The fourth switch unit 80 includes a control signal input terminal, a low level signal input terminal and a signal output terminal. The control signal input terminal is coupled to the output terminal of the oscillation unit 30. The low level signal input terminal is connected to the low level signal supply terminal. The signal output terminal is connected to the output terminal of the active recovery module 20.

[0107] like Fig. 9 As shown, the fourth switch unit 80 may be an NMOS tube, the gate of the NMOS tube may be a control signal input terminal, the source of the NMOS tube may be a low level signal input terminal, and the drain of the NMOS tube may be a signal output terminal.

[0108] Usually, the fourth switch unit 80 is turned on or off by a signal at the control signal input terminal of the fourth switch unit 80. The photodetector is restored to a working state capable of detecting photons by a signal at the signal output terminal of the fourth switch unit 80.

[0109] In some embodiments, the active recovery module 20 further includes a second inverter 305 and a third inverter 306. The input end of the second inverter 305 is connected to the output end of the oscillation unit 30, the output end of the second inverter 305 is connected to the input end of the third inverter 306, and the output end of the third inverter 306 is connected to the control signal input end of the fourth switch unit 80.

[0110] In some embodiments, the active recovery module 20 further includes an inverting unit 40 . The input end of the oscillation unit 30 is connected to the output end of the inverting unit 40 , and the input end of the inverting unit 40 is coupled to the input end of the active recovery module 20 .

[0111] For the description of the inverting unit 40 , please refer to the above content and will not be repeated here.

[0112] Fig. 9 The front-end circuit shown shows an implementation of an oscillating unit (ie, Fig. 10A 3031). Specifically, the delay unit 303 may include a fourth inverter 3031, a delay capacitor 3032 and a delay resistor 3033. Here, the first electrode of the delay capacitor 3032 is connected to the output end of the delay unit 303, and the second electrode of the delay capacitor 3032 is connected to the low voltage. One end of the delay resistor 3033 is connected to the low potential, and the other end is coupled to the fourth inverter 3031. The input end of the fourth inverter 3031 is connected to the output end of the NOR gate 304 as the input end of the delay unit 303, and the output end of the fourth inverter 3031 is connected to the input end of the first inverter 302 as the output end of the delay unit 303.

[0113] When a high potential is applied to the cathode of the photodetector, a reverse bias is applied to the photodetector. Fig. 9 and Fig. 10A The oscillating unit 30 shown may also have other modifications.

[0114] In some embodiments, the oscillation unit 30 further includes a second inverter 305 and a third inverter 306. The input end of the second inverter 305 is connected to the output end of the NOR gate 304, the output end of the third inverter 306 is connected to the input end of the delay unit 303, the input end of the third inverter 306 is connected to the output end of the first inverter 302, and the output end of the third inverter 306 is connected to the second input end of the NOR gate 304 as the output end of the oscillation unit 30.

[0115] In some cases, see Fig. 10B As shown in the structural diagram of the oscillation unit 30, the delay unit 303 may include a fourth inverter 3031, a delay capacitor 3032 and a delay resistor 3033. Here, the first electrode of the delay capacitor 3032 is connected to the output end of the delay unit 303, and the second electrode of the delay capacitor 3032 is connected to a low voltage. One end of the delay resistor 3033 is connected to a high potential, and the other end is coupled to the fourth inverter 3031. The input end of the fourth inverter 3031 is connected to the output end of the second inverter 305 as the input end of the delay unit 303, and the output end of the fourth inverter 3031 is connected to the input end of the first inverter 302 as the output end of the delay unit 303.

[0116] In practical applications, by adding a NAND gate 301 or a NOR gate 304 in the active recovery module 20, the oscillation unit 30 outputs an oscillation signal, and the photodetector can be actively restored to a working state capable of detecting photons while increasing the area of ​​the front-end circuit to a negligible level. Thus, the problem of quenching failure can be solved at a relatively low circuit cost without increasing the recovery time.

[0117] Please refer to Fig.11A and Fig. 11B , shows the structure of the laser radar according to the present disclosure. Specifically, Fig.11A The functional structure diagram of the laser radar is shown. Fig. 11B A schematic diagram of the structure of a laser radar is shown.

[0118] Lidar includes an array of photodetectors (e.g. Fig.11A The SPAD array shown) and the laser array (e.g., Fig.11A The VCSEL array shown in FIG. Fig. 11B As shown, the photodetector array is arranged on the focal plane of the transmitting lens group, and the laser array is arranged on the focal plane of the receiving lens group.

[0119] In some embodiments, the present application discloses a photodetector array, which includes a two-dimensional photodetector array (eg, Fig.11A The above-mentioned two-dimensional photodetector array includes a predetermined number of photodetector modules, each of which includes a photodetector. Each photodetector is connected to the front-end circuit of the photodetector in the above-mentioned embodiment. After the photodetector is selected, the photodetector works in a state where the echo signal can be detected. When the photodetector receives the echo signal, it outputs an electrical signal corresponding to the echo signal, and the photodetector is quenched by the quenching module. The photodetector is restored to a state where the echo signal can be detected by the active recovery module to detect the next echo signal.

[0120] Generally, the active recovery module including the oscillation unit can restore the photodetector to a state capable of detecting the echo signal in a relatively short time, thereby shortening the time interval for the photodetectors in the photodetector array to detect the echo signal.

[0121] Please refer to Fig.12 , showing a schematic diagram of the interaction between the photodetector array and the laser array included in the laser radar according to the present disclosure.

[0122] In this embodiment, the laser radar includes a laser array (for example, Fig.12 TX shown in ), a photodetector array (e.g., Fig.12RX shown in ), a front-end circuit corresponding to each photodetector in the photodetector array, and a signal readout circuit.

[0123] In this embodiment, each laser in the laser array is used to emit a signal to the detection object (for example, Fig.12 Ob) shown in the figure is used to detect the detection signal.

[0124] In this embodiment, the photodetector array includes a two-dimensional photodetector array, and the two-dimensional photodetector array includes a predetermined number of photodetector modules.

[0125] In this embodiment, each detector module may include one or more photodetectors.

[0126] It should be noted that when the detector module includes multiple photodetectors, each photodetector can be enabled individually, or multiple photodetectors forming a photodetector group can be enabled together (to improve the dynamic range) to receive the echo signal.

[0127] In this embodiment, for each photodetector, after the photodetector is selected, the echo signal returned after the detection signal encounters the detection object is received. When the oscillation unit outputs the oscillation signal, the active recovery module of the front-end circuit of the photodetector adjusts the reverse bias of the photodetector to restore the photodetector to a state where the echo signal can be detected. When the photodetector receives the echo signal, it can output an electrical signal corresponding to the echo signal to the signal readout circuit, and the quenching module quenches the photodetector, and the active recovery circuit restores the photodetector to a state where the echo signal can be detected to detect the next echo signal.

[0128] Therefore, after the photodetector receives the echo signal, the photodetector is quenched by the quenching module included in the front-end circuit, and the photodetector is restored to a state where the echo signal can be detected by the active recovery module included in the front-end circuit, so that the photodetector can be quickly restored to a state where the echo signal can be detected. Further, the efficiency of the laser radar in detecting the echo signal can be achieved.

[0129] Please refer to Fig.13 , which shows a flow chart of a distance measurement method applied to the above-mentioned laser radar according to the present disclosure. The flow chart includes step 1301, step 1302, step 1303 and step 1304.

[0130] Step 1301, use the control circuit to output a first driving signal to drive the laser in the laser array of the laser radar to emit a detection signal, and record the first time when the above detection signal is emitted.

[0131] In this embodiment, the first laser radar can use the control circuit to output the first driving signal to drive the lasers in the laser array to emit the detection signal. In addition, the laser radar can record the first time when the detection signal is emitted.

[0132] When the detection signal encounters a detection object in space, an echo signal will be generated. It should be understood that the laser radar can drive one or more lasers in the laser array to emit a detection signal.

[0133] Step 1302, use the above-mentioned control circuit to output a second driving signal to drive the photodetector in the photodetector array that matches the above-mentioned laser; the photodetector, under the action of its front-end circuit, works in a state where the echo signal can be detected; in the state where the echo signal can be detected, when the photodetector receives the echo signal, it outputs an electrical signal corresponding to the above-mentioned echo signal to the above-mentioned signal readout circuit.

[0134] In this embodiment, the laser radar can use the control circuit to output a second driving signal to drive the photodetector in the photodetector array that matches the above-mentioned laser.

[0135] It should be understood that the above-mentioned photoelectric detector can receive the echo signal returned by the detection signal emitted by the above-mentioned laser after encountering the detection object.

[0136] In this embodiment, in the state where the echo signal can be detected, when the echo signal is received, the photodetector can output an electrical signal corresponding to the echo signal to the signal readout circuit.

[0137] In some scenarios, LiDAR can Fig.14 The circuit block diagram shown in FIG. outputs the electrical signal corresponding to the echo signal received by the photodetector to the signal readout circuit. Fig.14 As shown, the above circuit block diagram includes a front-end circuit, a signal processing circuit and a counting circuit. Specifically, after the photodetector receives the echo signal, the electrical signal corresponding to the echo signal can be output to the front-end circuit. Furthermore, the front-end circuit can quench the photodetector through the included quenching module, and restore the photodetector to a state where the echo signal can be detected through the included active recovery module. The front-end circuit can output the electrical signal corresponding to the echo signal to the signal processing circuit, and perform operations such as filtering, shaping, and amplifying the electrical signal. The signal processing circuit can output the processed electrical signal to the counting circuit, and count the processed electrical signal. The counting circuit can output the counted electrical signal to the signal readout circuit.

[0138] Therefore, after the photodetector avalanches, the front-end circuit promptly quenches the avalanche (making the reverse bias voltage Vbias of the photodetector less than the avalanche breakdown voltage Vbreak), and then quickly restores the photodetector to its initial state (making the reverse bias voltage Vbias of the photodetector greater than the avalanche breakdown voltage Vbreak), while outputting an avalanche pulse signal. The dead time of the quenching circuit should be as small as possible to ensure a high photon detection efficiency. The signal processing circuit filters and shapes the avalanche pulse signal to reduce the influence of dark counts (the probability of avalanche counts generated by noise carriers when there is no incident photons). Finally, after counting, the signal is output through the readout circuit for distance and reflectivity calculations.

[0139] Step 1303: Use a signal readout circuit to read out the electrical signal, and record a second time when the electrical signal is read out.

[0140] In this embodiment, the laser radar can use a signal readout circuit to read out the electrical signal. In addition, the laser radar can record the second time of reading out the electrical signal.

[0141] Step 1304, based on the first time and the second time, determine the distance between the laser radar and the detection object.

[0142] In this embodiment, the laser radar can determine the distance to the detection object based on the first time when the laser sends out the detection signal and the second time when the electrical signal corresponding to the echo signal is read out.

[0143] As an example, the first time is t1 and the second time is t2. The laser radar can obtain the distance to the detected object by dividing the product of the difference between t2 and t1 and the propagation speed of the laser by 2. That is, the determined distance is (t2-t1)*c / 2, where c represents the propagation speed of the laser in the air.

[0144] Therefore, after the photodetector receives the echo signal, the photodetector is quenched by the quenching module included in the front-end circuit, and the photodetector is restored to a state where the echo signal can be detected by the active recovery module included in the front-end circuit, so that the photodetector can be quickly restored to a state where the echo signal can be detected. Further, the efficiency of continuous ranging of the laser radar can be improved.

[0145] The above descriptions are only some preferred embodiments of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of disclosure involved in the embodiments of the present disclosure is not limited to the technical solutions formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above disclosed concept. For example, the above features are replaced with the technical features with similar functions disclosed in the present disclosure (but not limited to) to form a technical solution.

[0146] In addition, although each operation is described in a specific order, this should not be understood as requiring these operations to be performed in the specific order shown or in a sequential order. Under certain circumstances, multitasking and parallel processing may be advantageous. Similarly, although some specific implementation details are included in the above discussion, these should not be interpreted as limiting the scope of the present disclosure. Some features described in the context of a separate embodiment can also be implemented in a single embodiment in combination. On the contrary, the various features described in the context of a single embodiment can also be implemented in multiple embodiments individually or in any suitable sub-combination mode.

[0147] Although the subject matter has been described in language specific to structural features and / or methodological logical actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. On the contrary, the specific features and actions described above are merely example forms of implementing the claims.

Claims

1. A front-end circuit of a photodetector, It is characterized in that It includes a quenching module and an active recovery module, wherein: The quenching module is used to quench the photodetector after the photodetector receives a photon signal and undergoes avalanche breakdown; The active recovery module, the input end and the output end are both coupled to the output end of the photodetector, the output end has a preset time delay relative to the input end, and is used to restore the photodetector to a working state where it can detect photons again after the quenching module quenches the photodetector; The active recovery module includes an oscillation unit, which is suitable for generating a pulse oscillation signal to the output end of the active recovery module under the joint action of a detection signal and a feedback signal, wherein the detection signal is a signal output from the photodetector after detecting a photon, and the feedback signal is a signal output from the output end of the oscillation unit after inputting a signal output by the photodetector when detecting a photon last time; In which, the oscillation unit includes a NAND gate and a delay unit, the first input end of the NAND gate serves as the input end of the oscillation unit and is coupled to the input end of the active recovery module, the second input end of the NAND gate is connected to the output end of the oscillation unit for inputting the output signal of the oscillation unit, the output end of the NAND gate is coupled to the input end of the delay unit, and the output end of the delay unit serves as the output end of the oscillation unit; or, the oscillation unit includes a NOR gate and a delay unit, the first input end of the NOR gate serves as the input end of the oscillation unit and is coupled to the input end of the active recovery module, the second input end of the NOR gate is connected to the output end of the oscillation unit for inputting the output signal of the oscillation unit, the output end of the NOR gate is coupled to the input end of the delay unit, and the output end of the delay unit serves as the output end of the oscillation unit.

2. The front-end circuit of the photodetector according to claim 1, It is characterized in that The quenching module has one end coupled to the voltage supply end and the other end coupled to the output end of the photodetector; The anode of the photodetector is connected to a low potential; the cathode of the photodetector is used as an output terminal and is coupled to the other end of the quenching module; The oscillation unit includes the NAND gate and the delay unit.

3. The front-end circuit of the photodetector according to claim 2, It is characterized in that The oscillation unit further includes an odd number of first inverters, the output end of the NAND gate is connected to the input end of the first inverter, and the output end of the first inverter is coupled to the input end of the delay unit; The active recovery module also includes an inverting unit, the input end of the oscillation unit is connected to the output end of the inverting unit, and the input end of the inverting unit is coupled to the input end of the active recovery module; wherein the inverting unit includes a first PMOS tube and a first NMOS tube.

4. The front-end circuit of the photodetector according to claim 3, It is characterized in that The active recovery module further includes a first initial potential setting unit, wherein the first initial potential setting unit includes a first capacitor and a first switch unit; The input end of the first initial potential setting unit is connected to the input end of the active recovery module. One electrode of the first capacitor is connected to an input terminal of the first initial potential setting unit; Another electrode of the first capacitor is connected to the output end of the first initial potential setting unit, and another electrode of the first capacitor is connected to the output end of the first switch unit; The output end of the first initial potential setting unit is connected to the input end of the inverting unit.

5. The front-end circuit of the photodetector according to claim 2, It is characterized in that The active recovery module further includes a second switch unit, which includes a control signal input terminal, a high-level signal input terminal and a signal output terminal; The control signal input terminal is coupled to the output terminal of the oscillation unit; the high level signal input terminal is connected to the high level signal supply terminal; and the signal output terminal is connected to the output terminal of the active recovery module.

6. The front-end circuit of the photodetector according to claim 5, It is characterized in that The active recovery module further includes a second initial potential setting unit, wherein the second initial potential setting unit includes a second capacitor and a third switch unit; Wherein, the input end of the second initial potential setting unit is coupled to the output end of the oscillation unit, One electrode of the second capacitor is connected to the input terminal of the second initial potential setting unit; Another electrode of the second capacitor is connected to the output end of the second initial potential setting unit, and another electrode of the second capacitor is connected to the output end of the third switch unit.

7. The front-end circuit of the photodetector according to claim 6, It is characterized in that The active recovery module also includes a second inverter and a third inverter, the input end of the second inverter is connected to the output end of the oscillation unit, the output end of the second inverter is connected to the input end of the third inverter, and the output end of the third inverter is connected to the input end of the second initial potential setting unit.

8. The front-end circuit of the photodetector according to claim 5, It is characterized in that The active recovery module also includes a second inverter and a third inverter, the input end of the second inverter is connected to the output end of the oscillation unit, the output end of the second inverter is connected to the input end of the third inverter, and the output end of the third inverter is connected to the control signal input end of the second switch unit.

9. The front-end circuit of the photodetector according to claim 1, It is characterized in that The quenching module has one end coupled to the voltage supply end and the other end coupled to the output end of the photodetector; The cathode of the photodetector is connected to a high potential; the anode of the photodetector is used as an output terminal and is coupled to the other end of the quenching module; The oscillation unit includes the NOR gate and the delay unit.

10. The front-end circuit of the photodetector according to claim 9, It is characterized in that The oscillation unit further includes an odd number of first inverters, the output end of the delay unit is connected to the input end of the first inverter, and the output end of the first inverter serves as the output end of the oscillation unit; The active recovery module further includes a fourth switch unit, wherein the fourth switch unit includes a control signal input terminal, a low level signal input terminal and a signal output terminal; The control signal input terminal is coupled to the output terminal of the oscillation unit; the low level signal input terminal is connected to the low level signal supply terminal; and the signal output terminal is connected to the output terminal of the active recovery module.

11. The front-end circuit of the photodetector according to claim 10, It is characterized in that The active recovery module also includes an inverting unit, the input end of the oscillation unit is connected to the output end of the inverting unit, and the input end of the inverting unit is coupled to the input end of the active recovery module; wherein the inverting unit includes a first PMOS tube and a first NMOS tube.

12. The front-end circuit of the photodetector according to claim 11, It is characterized in that The active recovery module also includes a second inverter and a third inverter, the input end of the second inverter is connected to the output end of the oscillation unit, the output end of the second inverter is connected to the input end of the third inverter, and the output end of the third inverter is connected to the control signal input end of the fourth switch unit.

13. The front-end circuit of the photodetector according to claim 3, It is characterized in that The oscillation unit further includes a second inverter and a third inverter, wherein The input end of the second inverter is connected to the output end of the first inverter, the output end of the second inverter is connected to the input end of the third inverter, and the output end of the third inverter is connected to the input end of the delay unit.

14. The front-end circuit of the photodetector according to any one of claims 2 to 7, It is characterized in that The oscillation unit further includes a second inverter and a third inverter, wherein The input end of the second inverter is connected to the output end of the delay unit; the output end of the second inverter is connected to the input end of the third inverter, and the output end of the third inverter is connected to the second input end of the NAND gate as the output end of the oscillation unit.

15. The front-end circuit of the photodetector according to any one of claims 9 to 11, It is characterized in that The oscillation unit further includes a second inverter and a third inverter, wherein The input end of the second inverter is connected to the output end of the NOR gate, and the output end of the third inverter is connected to the input end of the delay unit; The input end of the third inverter is connected to the output end of the first inverter, and the output end of the third inverter is connected to the second input end of the NOR gate as the output end of the oscillation unit.

16. The front-end circuit of the photodetector according to any one of claims 2 to 8 or any one of claims 9 to 12, It is characterized in that The delay unit is used to provide a time delay, and includes: a fourth inverter, a delay capacitor and a delay resistor, and the size of the time delay is related to the product of the delay capacitor and the delay resistor; The fourth inverter is used to invert the signal inputted at the input end, the input end of the fourth inverter is connected to the input end of the delay unit, the output end of the fourth inverter and the first electrode of the delay capacitor are connected to the output end of the delay unit, and the second electrode of the delay capacitor is connected to a low voltage; One end of the delay resistor is connected to the power supply end, and the other end is coupled to the fourth inverter.

17. A photodetector array, It is characterized in that A two-dimensional photodetector array is provided, wherein the two-dimensional photodetector array includes a predetermined number of photodetector modules, wherein: Each detector module includes a photodetector; For each photodetector, connect to the front-end circuit of the photodetector according to any one of claims 1 to 16; After the photodetector is selected, the photodetector operates in a state where an echo signal can be detected. When the photodetector receives an echo signal, it outputs an electrical signal corresponding to the echo signal. The quenching module quenches the photodetector, and the active recovery module restores the photodetector to a state where an echo signal can be detected to detect the next echo signal.

18. A laser radar, It is characterized in that The method comprises a laser array, a photodetector array as claimed in claim 17, a front-end circuit corresponding to each photodetector in the photodetector array, and a signal readout circuit, wherein: Each laser in the laser array is used to emit a detection signal for detecting a detection object when the laser is driven; The photodetector array comprises a two-dimensional photodetector array, wherein the two-dimensional photodetector array comprises a predetermined number of photodetector modules, wherein: Each detector module includes a photodetector; For each photodetector, after the photodetector is selected, the echo signal returned after the detection signal encounters the detection object is received, wherein the active recovery module of the front-end circuit of the photodetector restores the photodetector to a state where the echo signal can be detected when the oscillation unit outputs an oscillation signal; when the photodetector receives the echo signal, the electrical signal corresponding to the echo signal is output to the signal readout circuit for calculating the distance of the detection object; the quenching module quenches the photodetector, and the active recovery circuit restores the photodetector to a state where the echo signal can be detected to detect the next echo signal.

19. A distance measurement method applied to the laser radar according to claim 18, It is characterized in that include: Using the control circuit to output a first driving signal, driving the laser in the laser array of the laser radar to emit a detection signal, and recording the first time when the detection signal is emitted, the detection signal generates an echo signal when encountering a detection object in space; The control circuit is used to output a second driving signal to drive a photodetector in a photodetector array that matches the laser, wherein the photodetector, under the action of its front-end circuit, operates in a state capable of detecting an echo signal; in the state capable of detecting an echo signal, when the photodetector receives an echo signal, the photodetector outputs an electrical signal corresponding to the echo signal to the signal readout circuit; Using the signal readout circuit to read out the electrical signal, and recording a second time of reading out the electrical signal; Based on the first time and the second time, a distance between the laser radar and the detection object is determined.

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