A lidar

Abstract

The application discloses a laser radar, which comprises a narrow-line-width multi-longitudinal-mode pulse laser, a photoelectric detector, a perforated mirror beam receiving system, a high-resolution narrow-line-width light splitting device and a plurality of single-photon detectors. The output beam of the narrow-line-width multi-longitudinal-mode pulse laser is emitted through the perforated mirror, and the photoelectric detector serves as a local signal. The echo signal photons reflected by a target are received through the receiving system, and are subjected to angle selection and spectral matching filtering through the light splitting device, and finally subjected to logical AND gate operation through the plurality of single-photon detectors, so that the final signal is simultaneously input into a time-correlation single-photon counter. The working performance of the photon counting laser radar in a strong noise environment is effectively improved, the false alarm probability of the laser radar is greatly reduced under the condition of ensuring the detection probability, the grating combined with the plurality of detectors can greatly reduce the background noise, the signal-to-noise ratio of the echo signal is greatly improved, and the detection capability of the laser radar is improved.

Description

Technical Field

[0001] This invention relates to the field of photon counting lidar technology, and more particularly to a lidar. Background Technology

[0002] As a high-precision, high-temporal-resolution, and high-sensitivity active detection technology, lidar is widely used in atmospheric monitoring, long-range active 3D imaging, and many other fields. Photon-counting lidar possesses extremely high detection sensitivity, down to the single-photon level, but it is highly susceptible to background noise, which can render the system ineffective. Improving the performance of photon-counting lidar in environments with strong background noise, effectively increasing the signal-to-noise ratio, and enhancing its all-weather capability have become key research priorities. In existing lidar solutions, the optical emission system typically uses a single-wavelength, narrow-linewidth pulsed laser to emit signal light, and the optical receiving system generally uses direct laser reception. Spectral filtering widely employs narrowband filters that cannot split the light. The bandwidth of commonly used filters is typically on the order of nanometers, and the minimum peak transmittance at the center wavelength is generally around 75%, which cannot meet the requirements of photon-counting lidar operating in environments with strong background noise, significantly impacting its performance. Summary of the Invention

[0003] The purpose of this invention is to effectively improve the background noise suppression capability of lidar, effectively reduce the false alarm probability of lidar, and simultaneously ensure the intensity of the signal light and the detection probability of the signal. This invention features a clear principle, convenient operation, and simple structure, effectively improving the signal-to-noise ratio of the echo signal, significantly reducing the bandwidth of the laser echo signal, and enhancing the performance of lidar in high-noise environments.

[0004] The technical solution of this invention is as follows: A lidar includes a narrow-linewidth multi-mode laser, a photodetector, a perforated mirror, a beam receiving system, a high-resolution narrow-linewidth beam splitter, a logic AND gate, multiple single-photon detectors, and a time-correlated photon counter. The narrow-linewidth multi-mode pulsed laser emits multi-mode pulsed laser light. The photodetector detects the signal as a local signal, which is output by the perforated mirror, reflected by the target, and received by the optical receiving system. The high-resolution narrow-linewidth beam splitter then performs spectral filtering and angle selection. First, the echo light undergoes simultaneous spectral matching filtering and angle selection, causing light of different wavelengths to exit at different angles. These are then received by different single-photon detectors. Background noise photons are not selected by the high-resolution narrow-linewidth beam splitter. Multiple single-photon detectors simultaneously perform a logic AND operation. Only when all multiple single-photon detectors simultaneously detect the signal is the detection signal output, which is then sent to the time-correlated single-photon counter. This significantly reduces the false alarm probability and noise of the system while ensuring the signal strength of each detector, thereby effectively improving the detection performance of the lidar.

[0005] Furthermore, the narrow-linewidth multi-mode pulsed laser can emit multiple pulses with extremely narrow intervals between their longitudinal modes at once.

[0006] Furthermore, the high-resolution narrow-linewidth spectrometer described above has an extremely narrow selective spectral bandwidth and high selection efficiency.

[0007] Furthermore, the aforementioned high-resolution narrow-linewidth beam splitter has angle selectivity, exhibiting different diffraction angles for incident beams of different wavelengths, resulting in high angular resolution and the ability to separate signal light with narrow wavelength intervals. The angular resolution is generally set according to system requirements and has no range requirement.

[0008] Furthermore, the AND gate structure can perform wavelength division of echo light of different wavelengths, perform logical AND operations, and receive signals simultaneously.

[0009] Furthermore, the aforementioned lidar can simultaneously perform wavelength-specific angle selection and spectral matching filtering on echo light of different wavelengths, and filter the center wavelength of each longitudinal mode.

[0010] The principle of this invention is as follows:

[0011] Photon-counting lidar boasts extremely high detection sensitivity but is highly sensitive to noise. This solution employs a specialized multi-mode laser as the light source and a specially designed high-resolution, narrow-linewidth beam splitter to simultaneously perform spectral selection, angle selection, and beam splitting on the lidar echo signal. The beam splitter's spectral filtering bandwidth is typically less than 100 pm, with a diffraction efficiency exceeding 80%. It can perform matched filtering on the center wavelengths of different longitudinal modes and emit the beam at different angles. The high-resolution, narrow-linewidth beam splitter possesses excellent throughput and angle selectivity, enabling the extremely narrow longitudinal mode spacing echo beam to be emitted at different angles, ensuring the intensity of the echo signal while filtering out background noise. At the receiving end, multiple detectors synchronously receive signals at different wavelengths, perform logical AND gate operations, and then simultaneously output the signals to a time-correlated single-photon counter, further reducing noise in each path. This solution significantly improves the performance of photon-counting lidar in high-noise environments.

[0012] The advantages of this invention compared to the prior art are:

[0013] (1) The high-resolution narrow-linewidth beam splitter of the present invention has high beam splitting efficiency and narrow spectral filtering bandwidth.

[0014] (2) Compared with traditional angle selection and beam splitting devices, the body grating of the present invention has higher wavelength resolution, that is, it can separate light of different wavelengths within a narrow spectral interval and has higher beam splitting efficiency, thus ensuring signal strength.

[0015] (3) The narrow linewidth multi-mode laser of the present invention can emit multiple pulses of light with extremely narrow intervals between longitudinal modes at once, and each wavelength beam has a narrow bandwidth.

[0016] (4) The multi-detector receiver of the present invention can simultaneously receive echo beams of different wavelengths and perform detection at the same time.

[0017] (5) Compared with traditional multi-detector lidar, the present invention can simultaneously perform spectral matching filtering on multiple spectral lines of multi-longitudinal mode lasers, process echo signals of multiple wavelengths, and perform logical AND operations.

[0018] (6) The present invention has the characteristics of clear principle, simple structure, convenient operation, effective reduction of laser radar echo signal spectral bandwidth, improvement of signal-to-noise ratio and improvement of signal quality. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a lidar according to the present invention;

[0020] Figure 2 Simulation of a lidar detection probability model and a false alarm probability model.

[0021] Explanation of reference numerals in the attached figures: 1 is a narrow linewidth multi-longitudinal-mode pulsed laser, 2 is a photodetector, 3 is a perforated mirror, 4 is an optical receiving system, 5 is a high-resolution narrow linewidth beam splitter, 6 is multiple single-photon detectors, 7 is a logic AND gate, and 8 is a time-correlated single-photon counter. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0023] Example 1

[0024] like Figure 1 As shown, this invention is a novel lidar system, comprising a narrow-linewidth multi-mode pulsed laser 1, a photodetector 2, a perforated mirror 3, an optical receiving system 4, a high-resolution narrow-linewidth beam splitter 5, multiple single-photon detectors 6, and a logic AND gate operator 7. The narrow-linewidth multi-mode pulsed laser 1 emits pulsed laser light, which is detected by the photodetector 2 as a local signal. This signal is emitted through the perforated mirror 3, reflected by the target object, and received by the optical receiving system 4. The high-resolution narrow-linewidth beam splitter 5 then selects the echo beams of different wavelengths, performing spectral matching filtering and angle selection. These echoes are then received by the multiple single-photon detectors 6, while other noise photons are not selected by the high-resolution narrow-linewidth beam splitter 5. Finally, the signal is output to a time-correlated photon counter 8 via the logic AND gate operator 7. This further narrows the noise in each path of the multiple detectors, thus achieving lidar noise suppression. After filtering by high-resolution, narrow-linewidth beam splitters, the noise level is low. Multiple detectors further reduce noise, and combined with time-correlated single-photon counting technology, near-zero noise can be achieved. Simultaneously, the signal intensity of each path is guaranteed, thus improving the signal-to-noise ratio of the lidar.

[0025] It should be noted that the four detectors in the diagram are for illustrative purposes only, and the actual number of detectors is uncertain.

[0026] Figure 2 The simulation results of the lidar detection probability model and false alarm probability model of the present invention show that, compared with the traditional multi-detector detection scheme, the lidar has higher detection efficiency and significantly reduced false alarm probability.

[0027] As can be seen from the above specific implementation scheme, this invention is a lidar that, compared with traditional lidar, solves the problems of low receiving efficiency, wide spectrum, and low signal-to-noise ratio of traditional devices. It simplifies the internal structure of the lidar, improves its ease of use, greatly enhances its noise suppression capability, and effectively improves its working ability in high-noise environments. This expands the application range of lidar.

[0028] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lidar, characterized in that: The system includes a narrow-linewidth multi-longitudinal-mode pulsed laser (1), a photodetector (2), a perforated mirror (3), an optical receiving system (4), a high-resolution narrow-linewidth beam splitter (5), multiple single-photon detectors (6), an AND gate arithmetic unit (7), and a time-correlated single-photon counter (8). The narrow-linewidth multi-longitudinal-mode pulsed laser (1) emits a pulsed laser beam, and the photodetector (2) detects the beam signal as a local signal. The laser beam exits through the perforated mirror (3) and the echo beam reflected by the target is received by the optical receiving system (4). After angle selection and spectral matching filtering by the high-resolution narrow-linewidth beam splitter (5), echo signals of different wavelengths are obtained. The echo signals are simultaneously received by multiple single-photon detectors (6) and processed by the AND gate arithmetic unit (7) to obtain the calculation result. The calculation result is output to the time-correlated single-photon counter (8). The narrow linewidth multi-mode pulsed laser (1) has a narrow total laser linewidth, a narrow linewidth of a single longitudinal mode, and a narrow longitudinal mode spacing. The total laser linewidth does not exceed 200 pm, the linewidth of a single longitudinal mode does not exceed 50 pm, and the longitudinal mode spacing does not exceed 20 pm. The high-resolution narrow-linewidth beam splitter (5) has a narrow spectral filtering range and high diffraction efficiency. The spectral filtering bandwidth of the beam splitter is less than 100 pm and the diffraction efficiency exceeds 80%. The high-resolution narrow-linewidth beam splitter (5) is a volume grating.

2. The lidar according to claim 1, characterized in that, The high-resolution narrow-linewidth beam splitter (5) has angle selectivity, and has different diffraction angles for incident beams of different wavelengths. It has high angular resolution and can separate signal light with narrow wavelength intervals.

3. The lidar according to claim 1, characterized in that, High-resolution narrow-linewidth beam splitters can simultaneously perform matched filtering on multiple longitudinal modes with different center wavelengths and output multi-longitudinal-mode beams at the same time.

4. The lidar according to claim 1, characterized in that, Each of the multiple single-photon detectors (6) corresponds to one wavelength of the narrow linewidth multi-longitudinal-mode pulsed laser (1). The number of detectors is determined by the number of longitudinal modes of the laser, and is not less than 2 longitudinal modes.

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