A ranging method, apparatus, and computer device based on SiPM signals

Abstract

This invention relates to the field of photoelectric detection technology, and in particular to a ranging method, apparatus, and computer device based on SiPM signals. The processing method includes: acquiring a SiPM signal received at the current moment; calculating a photon excitation sequence based on the SiPM signal and a pre-acquired single-photon signal; determining the return time of the light from the emitting unit based on the photon excitation sequence and a pre-acquired emission signal; and obtaining the ranging distance based on the return time. Therefore, the ranging accuracy of the SiPM-based lidar can be guaranteed when detecting weak signals.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection technology, and in particular to a ranging method, apparatus, and computer equipment based on SiPM signals. Background Technology

[0002] Silicon photomultiplier (SiPM), also known as MPPC (multi-pixel photon counter) by HAMAMATSU, is a novel photodetector device composed of an array of avalanche diodes operating in Geiger mode. It features high gain, high sensitivity, low bias voltage, insensitivity to magnetic fields, and a compact structure, and is widely considered a promising direction for future development of extremely weak light detectors. In lidar, it can reduce radar size and improve detection capabilities. Ranging accuracy is a crucial performance indicator for lidar. The inventors of this invention discovered during long-term research that when using SiPM-based lidar to detect weak signals, ranging accuracy remains difficult to guarantee. Summary of the Invention

[0003] Based on the problems and shortcomings of the existing technology, the present invention provides a ranging method, device and computer equipment based on SiPM signal to solve the problem that the ranging accuracy is still difficult to guarantee when SiPM is used to detect weak signals.

[0004] One embodiment of the present invention provides a ranging method based on SiPM signals, comprising:

[0005] Obtain the SiPM signal received at the current moment;

[0006] Based on the SiPM signal and the pre-acquired single-photon signal, the photon excitation sequence is calculated;

[0007] Based on the photon excitation sequence and the pre-acquired emission signal, the return time of the light from the light-emitting unit is determined;

[0008] The distance is obtained based on the return time.

[0009] Optionally, determining the return time of the light from the light-emitting unit based on the photon excitation sequence and the pre-acquired emission signal includes:

[0010] Calculate the cross-correlation function between the photon excitation sequence and the pre-acquired emission signal;

[0011] The return time of the light from the light-emitting unit is determined based on the cross-correlation function.

[0012] Optionally, the time corresponding to the maximum value of the cross-correlation function is taken as the return time of the light from the light-emitting unit.

[0013] Optionally, based on the SiPM signal and the single-photon signal, a photon excitation sequence is calculated, including:

[0014] Based on the SiPM signal and the single-photon signal, the photon excitation sequence is calculated using the deconvolution method.

[0015] Optionally, calculating the photon excitation sequence based on the SiPM signal and the single-photon signal includes:

[0016] Perform a Fourier transform on the SiPM signal to obtain the frequency domain signal of the SiPM signal;

[0017] Perform a Fourier transform on the single-photon signal to obtain the frequency domain signal of the single-photon signal;

[0018] The frequency domain signals of the SiPM signal and the single-photon signal are subjected to Wiener filtering to obtain the photon excitation sequence.

[0019] Optionally, obtaining the distance based on the return time includes:

[0020] according to And the distance measured by the return time;

[0021] Wherein, d is the distance measured, Δt is the return time, and c is a preset coefficient constant.

[0022] Based on the same inventive concept, one embodiment of the present invention also provides a ranging device based on SiPM signals, comprising:

[0023] The signal acquisition module is used to acquire the SiPM signal received at the current moment;

[0024] The photon excitation sequence calculation module is used to calculate the photon excitation sequence based on the SiPM signal and the pre-acquired single-photon signal;

[0025] The return time calculation module is used to determine the return time of the light from the light-emitting unit based on the photon excitation sequence and the pre-acquired emission signal.

[0026] The distance calculation module is used to obtain the measured distance based on the return time.

[0027] Optionally, the return time calculation module includes:

[0028] The cross-correlation function calculation submodule is used to calculate the cross-correlation function between the photon excitation sequence and the pre-acquired emission signal;

[0029] The return time determination submodule is used to determine the return time of the light from the light-emitting unit based on the cross-correlation function.

[0030] Optionally, the return time is the time corresponding to the maximum value of the cross-correlation function.

[0031] Based on the same inventive concept, one embodiment of the present invention also provides a computer device, including a memory and one or more processors, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the one or more processors, the one or more processors perform the steps of the above-described method.

[0032] One of the above technical solutions has the following advantages and beneficial effects:

[0033] This invention provides a ranging method, apparatus, computer device, and medium based on SiPM signals. The ranging method based on SiPM signals acquires the SiPM signal received at the current moment, calculates a photon excitation sequence based on the SiPM signal and pre-acquired single-photon signals, determines the return time of the light from the emitting unit based on the photon excitation sequence and pre-acquired emission signals, and obtains the measured distance based on the return time. Therefore, the ranging accuracy of the SiPM-based lidar can be guaranteed when detecting weak signals. Attached Figure Description

[0034] The embodiments of this invention will be described in conjunction with the accompanying drawings. The accompanying drawings are for illustrative purposes only and are intended to describe the embodiments.

[0035] Figure 1 A flowchart illustrating a ranging method based on SiPM signals, provided as an embodiment of the present invention;

[0036] Figure 2 A schematic diagram of a transmission signal provided according to an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of a photon receiving sequence and a photon excitation sequence provided in one embodiment of the present invention;

[0038] Figure 4 A schematic diagram of a single-photon signal pulse provided in one embodiment of the present invention;

[0039] Figure 5 This is a schematic diagram of the final acquired signal provided in one embodiment of the present invention;

[0040] Figure 6 A schematic diagram of the frequency domain values ​​of a single-photon signal provided in one embodiment of the present invention;

[0041] Figure 7 This is a schematic diagram of a ranging device based on SiPM signals, provided as an embodiment of the present invention. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It is to be understood that the specific embodiments described herein are only for explaining the present invention and not for limiting the present invention. Furthermore, it should be noted that, for ease of description, only the parts related to the present invention are shown in the accompanying drawings, not all structures. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0043] The terms "first," "second," etc., used in this invention are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0044] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0045] like Figure 1As shown, in one embodiment, a ranging method based on SiPM signals is provided. The SiPM (Silicon Photomultiplier Tube) consists of a large number (hundreds to thousands) of avalanche diode (APD) units. Each unit consists of an APD and a large-value quenching resistor connected in series, and these micro-elements are connected in parallel to form a planar array. After applying a reverse bias voltage (typically tens of volts) to the silicon photomultiplier tube, the depletion layer of each micro-element's APD has a high electric field. If a photon enters, the APD of the micro-element undergoes avalanche. At this time, the current in each micro-element circuit suddenly increases, and the voltage drop across the quenching resistor R also increases. The electric field in the APD instantly decreases, meaning the avalanche stops after the APD outputs a momentary current pulse. Since the quenching resistor values ​​are the same for different micro-elements, theoretically, each micro-element will output a pulse of equal magnitude. The APD is an analog device, but macroscopically, each micro-element is a logic unit; a signal output is "1", and no signal output is "0". Within the dynamic range of the silicon photomultiplier tube, the magnitude of its output current is proportional to the number of micro-elements undergoing avalanche. When a pixel in a SiPM receives an incident photon, it outputs a pulse of a certain amplitude. If multiple pixels receive incident photons, each pixel will output a pulse. These pulses will eventually be superimposed and output from a common output terminal. For example, if three photons are simultaneously incident on different pixels and detected at the same time, the silicon photomultiplier tube will output a signal with an amplitude equal to the height of the superposition of the three pulses.

[0046] The method includes the following steps:

[0047] Step 101: Obtain the SiPM signal received at the current moment;

[0048] like Figure 2 As shown, the signal of the SiPM is emitted by the light-emitting unit. The emitted signal is not an ideal impulse function, but rather a Gaussian-like waveform lasting for a certain duration, i.e., it has a certain pulse width, such as... Figure 3 As shown, after reflection and attenuation by the reflector, the signal is received by the receiving unit. The waveform of the attenuated signal is similar to that of the transmitted signal. The time axis t remains unchanged, while the power P decreases by a certain factor. Differentiating the time axis, the optical power within the time interval dt is dP, and the optical energy E = dt·dP. According to the wave-particle duality of light, each photon carries a certain amount of energy. Therefore, it can be determined how many photons are received within each time interval dt, forming a photon reception sequence, such as... Figure 4 As shown in the bar graph, each photon within time dt strikes the SiPM and is absorbed by a certain infinitesimal element on the SiPM, generating a single-photon signal pulse with a certain probability. Figure 3 As shown in the light gray bar graph, there are a number of infinitesimal excitations within the time interval dt, forming a photon excitation sequence, such as... Figure 5As shown, each excited SiPM micro-element in the sequence generates a single-photon signal pulse. The output of these single-photon signal pulses is the convolution of the photon excitation sequence and the single-photon signal pulses. The output signal is then superimposed with circuit noise and acquired by an ADC to obtain the signal data we have acquired.

[0049] Obtain the SiPM signal y(n) emitted by the light-emitting unit at the current moment.

[0050] Step 102: Calculate the photon excitation sequence based on the SiPM signal and the pre-acquired single-photon signal;

[0051] In one embodiment of this application, step 102 includes:

[0052] Sub-step S11: Based on the SiPM signal and the single-photon signal, the photon excitation sequence is calculated using the deconvolution method.

[0053] In one embodiment of this application, sub-step S11 includes:

[0054] Sub-step S111: Perform a Fourier transform on the SiPM signal to obtain the frequency domain signal of the SiPM signal;

[0055] Sub-step S112: Perform a Fourier transform on the single-photon signal to obtain the frequency domain signal of the single-photon signal;

[0056] Sub-step S113 involves performing Wiener filtering on the frequency domain signals of the SiPM signal and the single-photon signal to obtain the photon excitation sequence.

[0057] Let the transmitted signal be s(t) and the received signal be s'(t), satisfying s'(t) = a·s(t), where a is the attenuation coefficient. Let the photon excitation sequence be x(t). Ignoring the effect of time, x(t) is probabilistically related to s'(t). Let the single-photon signal be h(t) and the received signal be y(t).

[0058] y(t)=x(t)*h(t)+ε(t) (1)

[0059] The asterisk (*) represents the convolution symbol.

[0060] Its discrete form is:

[0061]

[0062] Where ε(n) is the superposition of circuit noise and quantization noise acquired by the ADC, which can be considered as white noise.

[0063] Based on the principle of signal generation, a ranging algorithm is derived, which consists of the detected signal and the pre-obtained photon excitation sequence.

[0064] To obtain the photon excitation sequence, we consider using the deconvolution method. According to equation (2): y(n)=x(n)*h(n)+ε(n), ignoring the influence of noise, then...

[0065] y(n)=x(n)*h(n) (3)

[0066] When converted to the frequency domain,

[0067] Y(ω)=X(ω)H(ω) (4)

[0068] Wherein, X(ω) is the frequency domain signal of the photon excitation sequence, Y(ω) is the frequency domain signal of the SiPM signal, and H(ω) is the frequency domain signal of the single photon signal, and thus the photon excitation sequence can be calculated.

[0069] have to

[0070]

[0071] The convolution process is essentially a filtering process, equivalent to performing a low-pass filter on the photon excitation sequence using the frequency domain of the single-photon signal. The frequency domain values ​​of the single-photon signal are as follows: Figure 6 As shown.

[0072] The high-frequency components of H(ω) approach 0, so the high-frequency components of 1 / H(ω) approach ∞. However, noise has many high-frequency components. During deconvolution, the high-frequency components of noise will be amplified, resulting in poor deconvolution results.

[0073] To achieve deconvolution, Wiener filtering is used to suppress noise.

[0074] From equation (2), y(n) = x(n) * h(n) + ε(n), we hope to find a filter g(n) that takes y(n) as input and outputs:

[0075]

[0076] x'(n) is an estimate of x(n) that satisfies the orthogonality principle, i.e., (x(n)-x'(n)) is orthogonal to y(n).

[0077]

[0078] Right now

[0079]

[0080] Right now

[0081]

[0082] Convert to frequency domain

[0083] R xy (ω)=R yy (ω)G(ω) (10)

[0084] and

[0085] R yy (ω)=|H(ω)| 2 R xx (ω)+R nn (ω) (11)

[0086] R xy (ω)=H * (ω)R xx (ω) (12)

[0087] The asterisk (*) represents the conjugate symbol.

[0088] achievable

[0089]

[0090] achievable

[0091]

[0092] Without knowing R nn (ω) or R xx When (ω) is used, it can be replaced by γ, that is...

[0093]

[0094] Where γ is a positive constant, it should be the reciprocal of the noise ratio.

[0095] Then, the estimated photon excitation sequence x'(n) can be obtained by inverse Fourier transform.

[0096] Step 103: Based on the photon excitation sequence and the pre-acquired emission signal, determine the return time of the light from the light-emitting unit;

[0097] In one embodiment of this application, step 103 includes:

[0098] Sub-step S21: Calculate the cross-correlation function of the photon excitation sequence and the pre-acquired emission signal;

[0099] Sub-step S22: Determine the return time of the light from the light-emitting unit based on the cross-correlation function.

[0100] In one embodiment of this application, sub-step S22 includes:

[0101] Sub-step S221: The time corresponding to the maximum value of the cross-correlation function is taken as the return time of the light from the light-emitting unit.

[0102] Calculate the cross-correlation function between x'(n) and the emitted signal s(n).

[0103]

[0104] Where, r xs (m) represents the return time of light.

[0105] The time when the cross-correlation function reaches its maximum value is taken as the return time of the light.

[0106] Step 104: Obtain the distance measured based on the return time.

[0107] In one embodiment of this application, step 104 includes:

[0108] Sub-step S31, according to And the distance measured by the return time;

[0109] Wherein, d is the distance measured, Δt is the return time, and c is a preset coefficient constant.

[0110] Unlike existing technologies, this method acquires the SiPM signal received at the current moment, calculates a photon excitation sequence based on the SiPM signal and a pre-acquired single-photon signal, determines the return time of the light from the emitting unit based on the photon excitation sequence and a pre-acquired emission signal, and obtains the distance based on the return time. This ensures the ranging accuracy of lidar using SiPM when detecting weak signals.

[0111] like Figure 7 As shown, based on the same inventive concept, one embodiment of the present invention also provides a ranging device based on SiPM signals, comprising:

[0112] The signal acquisition module 701 is used to acquire the SiPM signal received at the current moment;

[0113] The photon excitation sequence calculation module 702 is used to calculate the photon excitation sequence based on the SiPM signal and the pre-acquired single photon signal;

[0114] The return time calculation module 703 is used to determine the return time of the light from the light-emitting unit based on the photon excitation sequence and the pre-acquired emission signal;

[0115] The distance calculation module 704 is used to obtain the distance measured based on the return time.

[0116] In one embodiment of this application, the return time calculation module 703 includes:

[0117] The cross-correlation function calculation submodule is used to calculate the cross-correlation function between the photon excitation sequence and the pre-acquired emission signal;

[0118] The return time determination submodule is used to determine the return time of the light from the light-emitting unit based on the cross-correlation function. In this embodiment, the time corresponding to the maximum value of the cross-correlation function is taken as the return time of the light from the light-emitting unit.

[0119] In one embodiment of this application, the photon excitation sequence calculation module 702 includes:

[0120] The deconvolution photon excitation sequence calculation submodule is used to calculate the photon excitation sequence based on the SiPM signal and the single photon signal using the deconvolution method.

[0121] In one embodiment of this application, the photon excitation sequence calculation module 702 includes:

[0122] The Fourier transform calculation submodule is used to perform Fourier transform on the SiPM signal to obtain the frequency domain signal of the SiPM signal;

[0123] The frequency domain signal calculation submodule is used to perform Fourier transform on the single-photon signal to obtain the frequency domain signal of the single-photon signal;

[0124] The Wiener filtering calculation submodule is used to perform Wiener filtering on the frequency domain signals of the SiPM signal and the single-photon signal to obtain the photon excitation sequence.

[0125] In one embodiment of this application, the distance calculation module 704 includes:

[0126] Return to the time calculation submodule, used to calculate based on And the distance measured by the return time;

[0127] Wherein, d is the distance measured, Δt is the return time, and c is a preset coefficient constant.

[0128] Based on the same inventive concept, one embodiment of the present invention also provides a computer device, including a memory and one or more processors, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the one or more processors, the one or more processors perform the steps of the above-described method.

[0129] Based on the same inventive concept, one embodiment of the present invention also provides a computer-readable storage medium, wherein when the computer-readable instructions are executed by one or more processors, the one or more processors perform the steps of the above method.

[0130] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0131] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0132] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0133] In the embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0134] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0135] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0136] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0137] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A ranging method based on SiPM signals, characterized in that, include: Obtain the SiPM signal received at the current moment; Based on the SiPM signal and the pre-acquired single-photon signal, the photon excitation sequence is calculated; Based on the photon excitation sequence and the pre-acquired emission signal, the return time of the light from the light-emitting unit is determined; The distance is obtained based on the return time.

2. The ranging method based on SiPM signals according to claim 1, characterized in that, Determining the return time of the light from the light-emitting unit based on the photon excitation sequence and the pre-acquired emission signal includes: Calculate the cross-correlation function between the photon excitation sequence and the pre-acquired emission signal; The return time of the light from the light-emitting unit is determined based on the cross-correlation function.

3. The ranging method based on SiPM signals according to claim 2, characterized in that, Determining the return time of the light from the light-emitting unit based on the cross-correlation function includes: The time corresponding to the maximum value of the cross-correlation function is taken as the return time of the light from the light-emitting unit.

4. The ranging method based on SiPM signals according to claim 1, characterized in that, The calculation of the photon excitation sequence based on the SiPM signal and the single-photon signal includes: Based on the SiPM signal and the single-photon signal, the photon excitation sequence is calculated using the deconvolution method.

5. The ranging method based on SiPM signals according to claim 4, characterized in that, The calculation of the photon excitation sequence based on the SiPM signal and the single-photon signal includes: Perform a Fourier transform on the SiPM signal to obtain the frequency domain signal of the SiPM signal; Perform a Fourier transform on the single-photon signal to obtain the frequency domain signal of the single-photon signal; Wiener filtering is performed on the frequency domain signals of the SiPM signal and the single-photon signal to obtain the photon excitation sequence.

6. The ranging method based on SiPM signals according to claim 1, characterized in that, The distance measured based on the return time includes: according to And the distance measured at the time of return; Among them, the The distance to be measured. For the return time, These are pre-defined coefficient constants.

7. A ranging device based on SiPM signals, characterized in that, include: The signal acquisition module is used to acquire the SiPM signal received at the current moment; The photon excitation sequence calculation module is used to calculate the photon excitation sequence based on the SiPM signal and the pre-acquired single-photon signal; The return time calculation module is used to determine the return time of the light from the light-emitting unit based on the photon excitation sequence and the pre-acquired emission signal; The distance calculation module is used to obtain the measured distance based on the return time.

8. The ranging device based on SiPM signals according to claim 7, characterized in that, The return time calculation module includes: The cross-correlation function calculation submodule is used to calculate the cross-correlation function between the photon excitation sequence and the pre-acquired emission signal; The return time determination submodule is used to determine the return time of the light from the light-emitting unit based on the cross-correlation function.

9. The ranging device based on SiPM signals according to claim 8, characterized in that, The returned time is the time corresponding to the maximum value of the cross-correlation function.

10. A computer device comprising a memory and one or more processors, the memory storing computer-readable instructions which, when executed by the one or more processors, cause the one or more processors to perform the steps of the method of any one of claims 1 to 6.

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