Random single-photon laser ranging method and system

Abstract

The invention provides a random single-photon laser ranging method and system, and belongs to the field of laser ranging. According to the invention, only one SPAD (single photon avalanche photodiode) is adopted to complete distance measurement, and the signal screening module is added to ensure that the screened signal still meets the true random requirement, and the screened signal is used as an excitation signal to ensure that the detection process can be continuously carried out once the detection process starts without interruption and additional control. Therefore, the cost can be reduced, the size of the system can be reduced, distance measurement can be completed only by using one SPAD, and the effect is equivalent to that of a random single-photon laser distance measurement method using two SPADs.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser ranging, and particularly relates to a random single-photon laser ranging method and system. Background Art

[0002] Random single-photon laser ranging uses a single-photon avalanche photodiode (SPAD) as a detector, which can measure weak signal targets at long distances. At the same time, the emitted pulses use a randomly encoded pulse sequence. This pulse sequence can improve the signal-to-noise ratio of the ranging signal on the one hand, and on the other hand, the target distance can be obtained in one detection without multiple accumulations, greatly reducing the ranging time and enabling the detection of high-dynamic targets. Currently, random single-photon laser ranging methods have received extensive attention in the field of laser ranging.

[0003] Existing random single-photon laser ranging methods use 2 SPADs. One of the SPADs responds to thermal noise or background light noise to generate a true random pulse sequence, which is used to encode the output signal of the laser. The other SPAD is used as a detector to receive the laser echo signal. The encoded signal and the echo signal are subjected to a correlation operation to obtain the distance information. Considering that the current production of SPADs in the near-infrared band is not high and the price is expensive, and each SPAD requires a complex peripheral circuit for driving, this random single-photon laser ranging method has much higher cost and system volume than traditional fixed-frequency ranging methods. Summary of the Invention

[0004] In view of the above technical problems, the present invention proposes a random single-photon laser ranging method and system to reduce the system volume and cost.

[0005] In a first aspect of the present invention, a random single-photon laser ranging system is disclosed. The system includes a photoelectric detection front-end circuit, a photon counting module, a signal screening module, a laser emitting unit, and a signal processing module; wherein,

[0006] The photoelectric detection front-end circuit includes a single-photon avalanche photodiode, which is used to output a random pulse electrical signal or convert the echo light pulse signal into an electrical pulse signal and output it, and send the output result to the photon counting module;

[0007] The photon counting module is used to perform time-correlated counting on the output result of the single-photon avalanche photodiode to obtain an initial reference pulse sequence and its corresponding dark count rate or an echo pulse sequence, and send it to the signal screening module;

[0008] The signal screening module screens the initial reference pulse sequence or the echo pulse sequence according to the dark count rate, and divides the screened electrical signal into two paths, one path is sent to the laser emitting unit, and the other path is sent to the signal processing module;

[0009] After the laser emission unit receives the filtered signal, it converts the signal into a sequence of optical pulses, emits the sequence to the target, and forms an echo signal optical pulse signal through the scattering of the target, which is then sent to the single-photon avalanche photodiode;

[0010] The signal processing module is used to perform a correlation operation on the filtered signals obtained twice adjacent to each other to obtain the target distance information.

[0011] The photoelectric detection front-end circuit further includes an amplifier circuit;

[0012] The amplifier circuit is used to amplify the amplitude of the output of the single-photon avalanche photodiode and send the amplified result to the photon counting module.

[0013] The number of signals of the filtered signal within a preset time does not exceed the dark count rate, and the signal pulse time interval is much larger than the SPAD dead time.

[0014] The signal screening module and the signal processing module are integrated on the FPGA circuit board.

[0015] The laser emission unit includes a drive circuit, a laser, and an optical system; among them,

[0016] After the drive circuit receives the filtered signal, it drives the laser according to the signal sequence to emit a sequence of optical pulses, which are then irradiated to the target through the optical system.

[0017] The second aspect of the present invention discloses a random single-photon laser ranging method, which is implemented by the random single-photon laser ranging system described in any one of the above, and the method includes:

[0018] S1, controlling the single-photon avalanche photodiode to turn on so that it outputs a random pulse electrical signal, performing time-correlated counting on the random pulse electrical signal through the photon counting module, determining its dark count rate, and outputting an initial reference pulse sequence;

[0019] S2, screening the initial reference pulse sequence by the signal screening module according to the dark count rate, and dividing the filtered electrical signal into two paths, one path is sent to the laser emission unit as an excitation signal, and the other path is sent to the signal processing module as a reference sequence;

[0020] S3, after the laser emission unit receives the filtered signal, it converts the signal into a sequence of optical pulses, emits the sequence to the target, and forms an echo signal optical pulse signal through the scattering of the target, which is then sent to the single-photon avalanche photodiode;

[0021] S4. Convert the returned optical pulse signal into an electrical pulse signal through a single-photon avalanche photodiode, and send it to the photon counting module for time-correlated counting to obtain an echo pulse sequence.

[0022] S5. Screen the echo pulse sequence by the signal screening module according to the dark count rate, and divide the screened electrical signal into two paths. One path of the excitation signal is sent to the laser emission unit and returns to execute step S3; the other path is sent to the signal processing module and step S6 is executed.

[0023] S6. Perform correlation operation on the screened signals obtained twice adjacent to each other through the signal processing module to obtain the target distance information.

[0024] The method further includes: amplifying the amplitude of the output of the single-photon avalanche photodiode through an amplifier circuit, and sending the amplified result to the photon counting module.

[0025] The number of signals of the signal screened by the signal screening module within the preset time does not exceed the dark count rate, and the signal pulse time interval is much larger than the SPAD dead time.

[0026] The third aspect of the present invention discloses a lidar, which includes the random single-photon laser ranging system described in any one of the above.

[0027] In summary, the solution proposed by the present invention has the following technical effects: Compared with the existing methods, the present invention can complete ranging only by using one SPAD (single-photon avalanche photodiode). And by adding a signal screening module, it can ensure that the screened signal still meets the true random requirement and use it as the excitation signal to ensure that the detection process can continue once it starts without interruption and external control. Therefore, the present invention can reduce costs and reduce the system volume. It can complete ranging only by using 1 SPAD, and the effect is equivalent to the random single-photon laser ranging method using 2 SPADs. Description of the Drawings

[0028] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required to be used in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 It is the implementation principle diagram of a random single-photon laser ranging system according to an embodiment of the present invention.

[0030] Figure 2 It is the structure diagram of a random single-photon laser ranging system according to an embodiment of the present invention. Detailed implementation mode

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0032] The first aspect of the present invention discloses a random single-photon laser ranging system, and the system includes a photoelectric detection front-end circuit, a photon counting module, a signal screening module, a laser emission unit, and a signal processing module; wherein,

[0033] The photoelectric detection front-end circuit includes a single-photon avalanche photodiode, which is used to output a random pulse electrical signal or convert the received light pulse signal into an electrical pulse signal and output it, and send the output result to the photon counting module;

[0034] The photon counting module is used to perform time-related counting on the output result of the single-photon avalanche photodiode to obtain an initial reference pulse sequence and its corresponding dark count rate or an echo pulse sequence, and send it to the signal screening module;

[0035] The signal screening module screens the initial reference pulse sequence or the echo pulse sequence according to the dark count rate, and divides the screened electrical signal into two paths, one path is sent to the laser emission unit, and the other path is sent to the signal processing module;

[0036] After receiving the screened signal, the laser emission unit converts it into an optical pulse sequence, emits it to the target, and forms an echo signal optical pulse signal after being scattered by the target, and sends it to the single-photon avalanche photodiode;

[0037] The signal processing module is used to perform a correlation operation on the screened signals obtained twice adjacent to each other to obtain the target distance information.

[0038] Please refer to Figure 1 , the present invention uses 1 SPAD as both a true random sequence generator and an echo signal detector at the same time.

[0039] At the beginning of ranging, the laser is not turned on temporarily, and the SPAD is turned on first. A true random signal sequence a(n) of a certain length is obtained by using the dark count of the SPAD. This sequence is first statistically processed by the photon counting module to determine its dark count rate N0, that is, the dark count generated per second.

[0040] After that, the photon counting module transmits the dark count rate information to the signal screening module. The signal screening module screens the output sequence a(n) of the SPAD according to this information. The screening goal is to ensure that the number of signals in a(n) within 1 second does not exceed the dark count rate N0, and the signal pulse time interval is much larger than the SPAD dead time.

[0041] One path of the signal output by the signal screening module is transmitted to the laser driver control module, and the other path is transmitted to the signal processing module. After receiving the signal output by the signal screening module, the laser drive control module drives the laser according to the signal sequence to emit a light pulse sequence.

[0042] After that, the SPAD will receive the reflected light pulse signal and output an electrical signal. The photon counting module records the echo sequence b(n) of the SPAD during this period. The signal processing module performs a correlation operation on the true random signal sequence a(n) and the echo sequence b(n) to obtain the target distance information.

[0043] Once the above process starts, it can continue without interruption and external control.

[0044] Through signal screening, the number of light pulses received by the SPAD always remains at its dark count level. The advantage of this is that the output signal spacing will not be too small due to excessive pulses. Once the output signal spacing becomes as small as the dead time, it will become a periodic signal with a period equal to the dead time. At this time, screening this signal cannot guarantee randomness.

[0045] Screening when the SPAD output signal spacing is far from decreasing to the dead time can ensure that the signals output by the SPAD come from the superposition of past dark counts and current dark counts, making the screened signals still meet the true random requirements.

[0046] Optionally, please refer to Figure 2 , the system consists of a photoelectric detection front-end circuit board, a laser and its drive circuit board, a signal detection and processing circuit board, TCSPC, and a host computer control device.

[0047] The photoelectric detection front-end circuit board includes an SPAD and an amplifier. The SPAD is responsible for converting the light pulse signal into an electrical pulse signal or outputting a random pulse sequence, and the amplifier is responsible for amplifying the millivolt-level electrical signal output by the SPAD to a level amplitude that can be recognized by the backend.

[0048] The laser and its drive circuit board includes an LD and a drive circuit, which are responsible for converting the electrical pulse signal into a light pulse signal.

[0049] The signal detection and processing circuit board includes an FPGA and a communication interface. The FPGA is responsible for receiving, storing, and screening the random pulse sequence output by the SPAD, driving the laser to emit optical pulse signals, providing trigger signals for the TCSPC, and performing related processing on the sequence signals. The communication interface is responsible for communicating with the host control device.

[0050] The TCSPC is responsible for performing time-correlated counting on the signals output by the SPAD.

[0051] The host control device is responsible for controlling and adjusting the parameters of each module and displaying the ranging results.

[0052] The working process of the system is as follows:

[0053] 1. First, turn on the SPAD, use the dark count of the SPAD to output a true random pulse sequence a(n), perform statistics through the TCSPC to determine its dark count rate N0, and transmit the dark count rate information to the FPGA.

[0054] 2. The FPGA screens a(n), removes some pulse signals, and ensures that the total count of the screened signal sequence does not exceed N0 and the interval between adjacent pulse signals is much greater than the SPAD dead time. (Almost no processing is required for the initial screening to meet the requirements. The purpose of the screening process is to screen the subsequent signals)

[0055] 3. The FPGA controls the LD to emit optical pulse signals through the drive circuit. The optical pulse timing is the same as the above true random pulse sequence. At the same time, the FPGA sends a trigger signal to start counting to the TCSPC.

[0056] 4. The SPAD starts to respond to the reflected optical pulse signal to generate an electrical signal and transmits the signal to the TCSPC. The TCSPC outputs an electrical pulse signal sequence b(n).

[0057] 5. The TCSPC sends the received electrical pulse signal sequence b(n) to the FPGA.

[0058] 6. The FPGA performs correlation operations on a(n) and b(n), and transmits the operation results to the host control device through the communication interface for result display.

[0059] 7. The FPGA screens b(n), and the screening process is the same as in 2, and then returns to 3.

[0060] Optionally, the laser emission unit includes a drive circuit, a laser, and an optical system; among them,

[0061] After receiving the screened signal, the drive circuit drives the laser according to the signal sequence to make it emit an optical pulse sequence, which is irradiated to the target through the optical system.

[0062] The second aspect of the present invention discloses a random single-photon laser ranging method, which is implemented by the random single-photon laser ranging system described in any one of the above. The method includes:

[0063] S1, control the single-photon avalanche photodiode to turn on so that it outputs a random pulse electrical signal, and perform time-correlated counting on the random pulse electrical signal through the photon counting module to determine its dark count rate, and output an initial reference pulse sequence;

[0064] S2, screen the initial reference pulse sequence according to the dark count rate through the signal screening module, and divide the screened electrical signal into two paths. One path is sent to the laser emitting unit as an excitation signal, and the other path is sent to the signal processing module as a reference sequence;

[0065] S3, after the laser emitting unit receives the screened signal, convert it into an optical pulse sequence, and emit it to the target, and form an echo signal optical pulse signal after scattering by the target, and send it to the single-photon avalanche photodiode;

[0066] S4, convert the echo optical pulse signal into an electrical pulse signal through the single-photon avalanche photodiode, and send it to the photon counting module for time-correlated counting to obtain an echo pulse sequence;

[0067] S5, screen the echo pulse sequence according to the dark count rate through the signal screening module, and divide the screened electrical signal into two paths. One path of the excitation signal is sent to the laser emitting unit and returns to execute step S3; the other path is sent to the signal processing module and step S6 is executed;

[0068] S6, perform correlation operation on the screened signals obtained twice adjacent to each other through the signal processing module to obtain the target distance information.

[0069] The method further includes: amplifying the amplitude of the output of the single-photon avalanche photodiode through an amplifier circuit, and sending the amplified result to the photon counting module.

[0070] The number of signals of the signal screened by the signal screening module within a preset time does not exceed the dark count rate, and the signal pulse time interval is much larger than the SPAD dead time.

[0071] The third aspect of the present invention discloses a lidar, which includes the random single-photon laser ranging system described in any one of the above.

[0072] In summary, the solution proposed by the present invention has the following technical effects: Compared with the existing methods, the present invention can complete ranging by only using one SPAD (Single Photon Avalanche Diode), and by adding a signal screening module, it can ensure that the screened signal still meets the requirements of true randomness and use it as the excitation signal to ensure that once the detection process starts, it can continue without interruption and external control. Therefore, the present invention can reduce costs and the system volume, complete ranging by only using 1 SPAD, and the effect is equivalent to that of the random single photon laser ranging method using 2 SPADs.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that it is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A random single-photon laser ranging system, characterized in that: The system includes a photoelectric detection front-end circuit, a photon counting module, a signal screening module, a laser emission unit and a signal processing module; wherein, The photoelectric detection front-end circuit includes a single-photon avalanche photodiode, which is used to output a random pulse electrical signal or convert an echo optical pulse signal into an electrical pulse signal and output it, and send the output result to the photon counting module; The photon counting module is used to perform time-correlated counting on the output results of the single-photon avalanche photodiode to obtain an initial reference pulse sequence and its corresponding dark count rate or echo pulse sequence, and send them to the signal screening module; The signal screening module screens the initial reference pulse sequence or the echo pulse sequence according to the dark count rate, and divides the screened electrical signal into two paths, one path is sent to the laser emission unit, and the other path is sent to the signal processing module; After receiving the screened signal, the laser emission unit converts it into a light pulse sequence and emits it to the target, and the echo signal light pulse signal is formed by the target scattering and sent to the single photon avalanche photodiode; The signal processing module is used to perform correlation operation on the filtered signals obtained twice adjacently to obtain the target distance information.

2. The random single-photon laser ranging system according to claim 1, characterized in that: The photoelectric detection front-end circuit also includes an amplifier circuit; The amplifier circuit is used to amplify the amplitude of the output of the single-photon avalanche photodiode and send the amplified result to the photon counting module.

3. The random single-photon laser ranging system according to claim 1, characterized in that: The number of signals filtered by the signal filtering module within a preset time does not exceed the dark count rate, and the time interval between signal pulses is much larger than the SPAD dead time.

4. The random single-photon laser ranging system according to claim 1, characterized in that: The signal screening module and the signal processing module are integrated on the FPGA circuit board.

5. The random single-photon laser ranging system according to claim 1, characterized in that: The laser emitting unit includes a driving circuit, a laser and an optical system; wherein, After receiving the screened signal, the driving circuit drives the laser according to the signal sequence, causing it to emit a sequence of light pulses that are then irradiated to the target through the optical system.

6. A random single-photon laser ranging method, characterized in that: The method is implemented by the random single-photon laser ranging system according to any one of claims 1 to 5, and the method comprises: S1, control the single photon avalanche photodiode to turn on so that it outputs a random pulse electrical signal, and perform time-correlated counting on the random pulse electrical signal through a photon counting module to determine its dark count rate, and output an initial reference pulse sequence; S2, screening the initial reference pulse sequence according to the dark count rate through the signal screening module, and dividing the screened electrical signal into two paths, one of which is sent to the laser emission unit as an excitation signal, and the other is sent to the signal processing module as a reference sequence; S3, after receiving the screened signal through the laser emission unit, it is converted into a light pulse sequence and emitted to the target, and the echo signal light pulse signal is formed by the target scattering and sent to the single photon avalanche photodiode; S4, converting the echo optical pulse signal into an electrical pulse signal through a single photon avalanche photodiode, and sending it to a photon counting module for time-correlated counting to obtain an echo pulse sequence; S5, the echo pulse sequence is screened according to the dark count rate by the signal screening module, and the screened electrical signal is divided into two paths, one of which is an excitation signal sent to the laser emitting unit and returns to execute step S3; the other is sent to the signal processing module and executes step S6; S6, performing correlation operation on the filtered signals obtained twice consecutively through the signal processing module to obtain target distance information.

7. The random single-photon laser ranging method according to claim 6, characterized in that: The method further includes: amplifying the amplitude of the output of the single-photon avalanche photodiode by an amplifier circuit, and sending the amplified result to the photon counting module.

8. The random single-photon laser ranging method according to claim 6, characterized in that: The number of signals filtered by the signal filtering module within a preset time does not exceed the dark count rate, and the time interval between signal pulses is much larger than the SPAD dead time.

9. A laser radar, characterized in that: The laser radar includes the random single-photon laser ranging system described in any one of claims 1-5.

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