Laser radar search system and method

Abstract

The application discloses a laser radar searching system and method. The method is applied to an electronic device, and the method comprises the following steps: a laser radar system comprises a laser emitting device, a laser detecting device, a time-dependent single-photon counting device and the electronic device; the laser detecting device can be adjusted to obtain a time difference between a laser detector searching echo signal and a laser signal emitted by a last laser emitter and a field of view angle; according to the time difference and the field of view angle, the number of photons of the echo signal and a noise rate corresponding to a scene to be searched are determined; according to the number of photons and the noise rate, a current signal-to-noise ratio is determined; when the current signal-to-noise ratio satisfies a signal-to-noise ratio threshold value, a larger searching range for searching a target mobile terminal exists, so that the searching range can be expanded, and the efficiency of searching the target mobile terminal is improved.

Description

Technical Field

[0001] This application relates to the field of lidar, and more specifically, to a lidar search system and method. Background Technology

[0002] With the development of science and technology, drones and unmanned aerial vehicles (UAVs) have become increasingly popular. Therefore, lidar for UAV detection in the Earth's atmosphere has received more research attention. Due to their small size and small radar cross-section, UAVs are difficult for lidar to detect at long distances. Currently, UAVs can be searched using spot scanning, but the search range is small, resulting in low efficiency. Summary of the Invention

[0003] In view of the above problems, this application proposes a lidar search system and method to solve the above problems.

[0004] In a first aspect, embodiments of this application provide a lidar search system, including a laser emitting device, a laser detection device, a time-correlated single-photon counting device, and an electronic device. The laser emitting device is connected to the time-correlated single-photon counting device, the laser detection device is connected to the time-correlated single-photon counting device, and the time-correlated single-photon counting device is connected to the electronic device. The laser emitting device is used to emit a laser signal, wherein the laser signal is transmitted along the emission optical path of the laser signal to the scene to be searched. The laser detection device is used to receive the echo signal reflected after the emitted laser signal encounters a target mobile terminal in the scene to be searched, and adjust the laser detection device to change the field of view. The time-correlated single-photon counting device is used to store the time difference between searching for the echo signal and the most recent emission of the laser signal. The electronic device is used to determine the range of the target mobile terminal based on the time difference.

[0005] Secondly, embodiments of this application provide a lidar search method, the method comprising: acquiring the time difference between the laser detector searching for the echo signal and the most recently emitted laser signal from the laser emitter, and the field of view corresponding to the second optical lens; determining the unidirectional transmittance of the laser signal of the lidar search system on a horizontal path based on the time difference; determining the number of photons in the echo signal based on the transmittance; determining the noise rate corresponding to the scene to be searched based on the transmittance and the field of view; determining the current signal-to-noise ratio (SNR) based on the number of photons and the noise rate; determining whether the current SNR meets a SNR threshold; if the current SNR does not meet the SNR threshold, re-acquiring an adjusted noise rate, and determining the SNR corresponding to the adjusted noise rate based on the adjusted noise rate; if the current SNR meets the SNR threshold, determining the range within which the electronic device searches for the target mobile terminal based on the current SNR.

[0006] The lidar search system and method provided in this application can adjust the lidar detection device to increase the receiving field of view. The higher the received noise rate, the lower the signal-to-noise ratio. When the signal-to-noise ratio reaches the signal-to-noise ratio threshold, there is a large range for searching target mobile terminals. In nighttime environments, the noise is low and the noise rate is high, so the range for searching target mobile terminals is even larger, thereby expanding the search range and improving the efficiency of searching for target mobile terminals. Attached Figure Description

[0007] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0008] Figure 1 A schematic diagram of a lidar search system provided in an embodiment of this application is shown;

[0009] Figure 2 A flowchart illustrating the lidar search method provided in an embodiment of this application is shown;

[0010] Figure 3 The diagram shows the echoes of a UAV at different field of view angles at 500m using the lidar search method provided in this embodiment of the application.

[0011] Figure 4 This diagram illustrates the echo histogram of a UAV using the lidar search method provided in this embodiment of the application in a dark environment at a distance of 500m.

[0012] Figure 5 The diagram illustrates the search results of a UAV at different distances using the lidar search method provided in this embodiment of the application.

[0013] Figure 6 This paper illustrates two sets of UAV echo models at similar distances but different field of view angles for the lidar search method provided in this application embodiment;

[0014] Figure 7 This illustration shows the actual photon echoes of a UAV at different distances in three field-of-view angles using the lidar search method provided in this application embodiment.

[0015] Figure 8 A block diagram of the lidar search device provided in an embodiment of this application is shown;

[0016] Figure 9 A block diagram of an electronic device for performing a lidar search method according to an embodiment of this application is shown;

[0017] Figure 10 A storage unit for storing or carrying program code implementing the lidar search method according to an embodiment of the present application is shown. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0019] LiDAR has proven to possess high sensitivity and temporal resolution, and due to its excellent beam directionality, most applications focus on ranging and imaging. LiDAR based on Time-correlated Single Photon Counting (TCSPC) can provide single-photon sensitivity and picosecond resolution for time-of-flight measurements, and has made significant progress in experimental development for various applications, including autonomous rendezvous and docking in space, space target search, UAV navigation, Advanced Driving Assistance Systems (ADAS), and autonomous driving. The University of Science and Technology of China (USTC) laboratory has successfully conducted single-photon imaging experiments on targets 200 kilometers away.

[0020] In recent years, unmanned aerial vehicles (UAVs) and other unmanned aerial vehicles have become increasingly popular. Therefore, lidar for UAV detection in the Earth's atmosphere has received more research attention. Due to their small size and small radar cross-section, UAVs are difficult for lidar to detect at long distances. During long-range detection, the Earth's atmosphere causes the number of echo photons to decrease quadrupled with increasing distance. The inventors found that most previously published research focused on how to use light spot scanning to search for UAV-like targets and how to increase the density of scanning points. For example, MEMS galvanometers are electromagnetically driven galvanometers using unique Micro-Electro-Mechanical System (MEMS) technology. MEMS galvanometers can be used to obtain the field of view (FOV), but the obtained FOV is relatively small.

[0021] To address the aforementioned problems, the inventors, through long-term research, discovered and proposed the lidar search system and method provided in this application. The lidar search system includes a laser emitting device, a laser detection device, a time-correlated single-photon counting device, and electronic equipment. The lidar search system can adjust the laser detection device to increase the receiving field of view. A higher received noise rate results in a lower signal-to-noise ratio (SNR). When the SNR reaches a threshold, a larger search range for target mobile terminals exists, and this range is even greater in nighttime environments, thereby expanding the search range and improving the efficiency of searching for target mobile terminals. The specific lidar search method will be described in detail in subsequent embodiments.

[0022] The following will describe the lidar search method that can be used in the embodiments of this application.

[0023] Please see Figure 1 , Figure 1 This illustration shows a schematic diagram of a lidar search system provided in an embodiment of this application. Specifically, the system may include a laser emitting device 110, a laser detection device 120, a time-correlated single-photon counting device 130, and an electronic device 200. The laser emitting device 110 is connected to the time-correlated single-photon counting device 130, the laser detection device 120 is connected to the time-correlated single-photon counting device 130, and the time-correlated single-photon counting device 130 is connected to the electronic device 200. The electronic device 200 may include smartphones, smartwatches, tablets, computers, or other electronic devices capable of running applications, and is not limited thereto.

[0024] The laser emitting device 110 can be used to emit laser signals, which are transmitted along the emission optical path to the scene to be searched. The scene to be searched can include the outdoors, and is not limited thereto.

[0025] Specifically, laser signals can include pulsed lidar, continuous wave lidar, and hybrid lidar, etc., without limitation.

[0026] In some embodiments, the laser emitting device 110 may include a laser emitter 111, through which the lidar can provide a light source. The laser emitter 110 may be a pulsed solid-state laser that uses a near-infrared wavelength, which can reduce solar background and low atmospheric absorption loss and transmit maximum pulse energy. The specific type of laser emitter is not limited here.

[0027] The laser detection device 120 can be used to receive the echo signal reflected after the laser signal is emitted and encounters a mobile terminal in the scene to be searched, and to adjust the laser detection device to change the field of view.

[0028] In this embodiment, the laser detection device can be adjusted to change the field of view.

[0029] In some embodiments, the laser detection device 120 may include a laser detector 121, which may be a compact, low-noise single-photon avalanche diode detector. The core diameter of the laser detector 121 may be 12.6 μm. The specific type of laser detector and the core diameter of the laser detector are not limited herein.

[0030] In some implementations, the target mobile terminal may include a small drone or a drone with a small radar cross-section, and there is no limitation herein.

[0031] The time-correlated single-photon counting device 130 can be used to store the time difference between the search echo signal and the most recently emitted laser signal. It should be noted that the time-correlated single-photon counting device 130 can record the time difference between photon search and the most recent laser irradiation, and send this time difference to electronic equipment for analysis. Since the time jitter of the time-correlated single-photon counting device 130 and the laser detector 120 is much smaller than the laser pulse width, the measured time jitter value of the lidar search system is small. Because the number of photons in the echo signal of a long-range lidar is very limited, the noise of the search scene in the lidar search system needs to be very low. The noise is mainly generated by the backscattering of laser pulses from the near-field atmosphere and common receiving optical elements. Therefore, the noise of the search scene is low at night, and the search range of the lidar system for target mobile terminals can be expanded by an order of magnitude.

[0032] In this embodiment, the laser emitting device 110 includes a laser emitter 111 and a first optical lens 112. The first optical lens 112 is disposed after the emitting optical path of the laser emitter 111. The laser detection device 120 includes a laser detector 121 and a second optical lens 1213. The second optical lens 123 is disposed before the optical path of the laser detector 121 receiving the echo signal.

[0033] In some embodiments, the first optical lens 112 can be used to diffuse the laser signal into the scene to be searched. As one method, the divergence angle can be changed by altering the position of the first optical lens 112. As another embodiment, the divergence angle of the first optical lens 112 can be changed by rotating it.

[0034] In some embodiments, a second optical lens 123 can be used to focus the echo signal onto the laser detector 121. The second optical lens 123 can couple the returned signal into a laser detector with an appropriate core diameter for efficient collection.

[0035] In some implementations, the field of view can be changed by altering the position of the second optical lens 123. One method is to rotate the second optical lens 123 to change its corresponding field of view. A larger field of view results in more received noise, a higher noise rate, and a lower signal-to-noise ratio (SNR). When the SNR reaches a threshold, the maximum range of the target mobile terminal that the lidar search system can search for is reached.

[0036] In some embodiments, the first optical lens 112 and the second optical lens 123 may be the same size, but the divergence angle corresponding to the first optical lens 112 is greater than the field of view angle corresponding to the second optical lens 123.

[0037] In some embodiments, the laser detection device 120 further includes a bandpass filter 122, which is disposed between the laser detector 120 and the second optical lens 123 to filter out signals other than the echo signal and prevent the wavelength of the non-selected echo signal from entering the laser detector 122, thereby reducing background noise and enabling the laser radar search system to search for target mobile terminals over a wider range.

[0038] Please see Figure 2 , Figure 2 A flowchart illustrating the lidar search method provided in an embodiment of this application is shown. In a specific embodiment, the lidar search method is applied to, for example... Figure 8 The laser radar search system shown and the electronic equipment 200 equipped with the laser radar search device 300 are shown. Figure 9The following will use an electronic device as an example to illustrate the specific process of this embodiment. Of course, it is understood that the electronic device used in this embodiment can be a terminal device with computing capabilities, such as smartphones, tablets, desktop computers, wearable electronic devices, etc., and is not limited thereto. The following will focus on... Figure 2 The process shown will be described in detail. The lidar search method may specifically include the following steps:

[0039] Step S110: Obtain the time difference between the laser detector searching for the echo signal and the most recent laser signal emitted by the laser emitter, as well as the field of view corresponding to the second optical lens.

[0040] In this embodiment, the electronic device can obtain the time difference between the laser detector search callback signal and the laser signal most recently emitted by the laser emitter, as well as the field of view corresponding to the second optical lens.

[0041] In some implementations, the electronic device can directly acquire the time difference between the laser detector search callback signal and the most recently emitted laser signal from the laser emitter, as well as the field of view corresponding to the second optical lens. As one approach, when the electronic device detects a laser signal emitted by the laser emitter, it can acquire the time difference between the laser detector search callback signal and the most recently emitted laser signal from the laser emitter, as well as the field of view corresponding to the second optical lens. Alternatively, the electronic device can pre-set and store a preset time; when the preset time is reached, the electronic device can acquire the time difference between the laser detector search callback signal and the most recently emitted laser signal from the laser emitter, as well as the field of view corresponding to the second optical lens. Yet another approach, the electronic device can receive a command; upon receiving a search command, the electronic device acquires the time difference between the laser detector search callback signal and the most recently emitted laser signal from the laser emitter, as well as the field of view corresponding to the second optical lens.

[0042] Step S120: Based on the time difference, determine the unidirectional transmittance of the laser signal of the lidar search system on the horizontal path.

[0043] In some implementations, the electronic device can determine the distance between the electronic device and the target mobile terminal based on the time difference between the laser detector search echo signal and the most recently emitted laser signal from the laser transmitter, and then determine the unidirectional transmittance of the laser signal of the lidar search system on the horizontal path based on the distance between the electronic device and the target mobile terminal.

[0044] In some implementations, the electronic device can pre-set and store a preset calculation formula for calculating the time difference. Based on this formula, it calculates the time difference between the laser detector search echo signal and the most recently emitted laser signal from the laser emitter, determining the unidirectional transmittance of the laser signal in the horizontal path of the lidar search system. As one approach, when the electronic device acquires the time difference between the laser detector search echo signal and the most recently emitted laser signal, it can calculate this time difference according to the preset formula to determine the unidirectional transmittance of the laser signal in the horizontal path of the lidar search system. In another implementation, the electronic device can store multiple time differences between laser detector search echo signals and the most recently emitted laser signal. When the electronic device receives a command to search for a target mobile terminal, it queries the time difference corresponding to that target mobile terminal, calculates the time difference according to the preset formula, and determines the unidirectional transmittance of the laser signal in the horizontal path of the lidar search system corresponding to that target mobile terminal. For example, the time difference between the laser detector search callback signal corresponding to target mobile terminal 1 and the laser signal emitted by the most recent laser emitter is time difference 1, and the time difference between the laser detector search callback signal corresponding to target mobile terminal 2 and the laser signal emitted by the most recent laser emitter is time difference 2. The electronic device can store time difference 1 and time difference 2. When the electronic device receives the instruction to search for target mobile terminal 1, it queries the time difference 1 corresponding to target mobile terminal 1, calculates the time difference 1 according to the preset calculation formula, and determines the unidirectional transmittance of the laser signal of the laser radar search system corresponding to target mobile terminal 1 on the horizontal path.

[0045] In some implementations, the electronic device can determine the distance R between itself and the target mobile terminal based on the distance calculation formula R=c×t, where c represents the speed of light and t represents the time difference. The electronic device can pre-set and store the distance calculation formula, and calculate the distance between itself and the target mobile terminal based on the time difference between the laser detector's search callback signal and the most recent laser signal emitted by the laser emitter, as well as the speed of light.

[0046] In some implementations, the electronic device determines the unidirectional transmittance of the laser signal of the lidar search system along the horizontal path according to formula (1). :

[0047] (1)

[0048] in, This represents the unidirectional transmittance of the laser signal in the horizontal path of the lidar search system. Expressed as the atmospheric molecular absorption coefficient, It is expressed as the atmospheric aerosol absorption coefficient. Expressed as the atmospheric molecular scattering coefficient, Let R represent the scattering coefficient of atmospheric aerosol particles, and let R represent the distance between the electronic device and the mobile terminal. Characterizes the atmospheric extinction coefficient.

[0049] In some implementations, the electronic device can determine the atmospheric extinction coefficient according to formula (2). :

[0050] (2)

[0051] in, The value represents the atmospheric extinction coefficient, and D represents atmospheric visibility. denoted as wavelength, q represents the correction factor.

[0052] Step S130: Determine the number of photons in the echo signal based on the transmittance.

[0053] In some implementations, the electronic device can determine the echo signal power of the lidar search system based on the unidirectional transmittance of the laser signal in the horizontal path, and then determine the number of photons in the echo signal based on the echo signal power of the lidar search system.

[0054] In some implementations, the electronic device can determine the echo signal power of the lidar search system according to formula (3). :

[0055] (3)

[0056] in, The power is expressed as the echo signal power of the lidar search system. Expressed as the target scattering coefficient, This represents the unidirectional transmittance of the laser signal in the horizontal path of the lidar search system. This is expressed as the luminous efficiency of the first optical lens. This is expressed as the luminous efficiency of the second optical lens. This is represented by the angle between the optical axis of the laser emitter and the normal of the mobile terminal. This is represented as the reflective area of ​​the target mobile terminal. This is represented by the area of ​​the reflected light spot from the target mobile terminal. Let R represent the area of ​​the second optical lens, and let R represent the distance between the electronic device and the mobile terminal. This represents the peak power of the signal emitted by the laser emitter.

[0057] In some implementations, the electronic device can determine the number of photons in the echo signal according to formula (4). :

[0058] (4)

[0059] in, This is expressed as the echo signal power of the lidar search system. Represented as the frequency of the laser signal, Represented as wavelength, Represented as the speed of light, Let be the photon energy, and h be Planck's constant.

[0060] Step S140: Based on the transmittance and the field of view, determine the noise rate corresponding to the scene to be searched.

[0061] In this embodiment, the electronic device can determine the noise rate of the scene to be searched based on the unidirectional transmittance of the laser signal of the lidar search system on the horizontal path and the field of view corresponding to the second optical lens. It should be noted that when the noise rate is greater than the saturation count rate of the laser detector, the target mobile terminal cannot be searched. Therefore, when the noise rate is lower than the saturation count rate of the laser detector, there is a maximum field of view during the lidar search process. After determining the laser detector and laser energy, the field of view becomes the key to improving the search efficiency.

[0062] In some implementations, the electronic device can determine the noise rate corresponding to the scene to be searched based on formula (5). :

[0063] (5)

[0064] in, This is represented by the noise rate corresponding to the scene to be searched. Let λ be the wavelength and h be Planck's constant. Let E represent the speed of light, and E represent the solar spectral irradiance. Expressed as the target scattering coefficient, This represents the unidirectional transmittance of the laser signal in the horizontal path of the lidar search system. This represents the area of ​​the second optical lens. This is expressed as the luminous efficiency of the second optical lens. This is expressed as the bandwidth of the bandpass filter. θr represents the solar altitude angle, and θr represents the field of view angle received by the laser detector.

[0065] Step S150: Determine the current signal-to-noise ratio based on the number of photons and the noise rate.

[0066] In this embodiment, the electronic device can determine the signal-to-noise ratio based on the number of photons and the noise rate of the echo signal. The greater the distance between the electronic device and the target mobile terminal, the smaller the signal-to-noise ratio.

[0067] In some implementations, the electronic device can determine the signal-to-noise ratio according to formula (6). :

[0068] (6)

[0069] SNR stands for Signal-to-Noise Ratio. This is expressed as the number of photons in the echo signal. This represents the noise rate corresponding to the scene to be searched.

[0070] Step S160: Determine whether the current signal-to-noise ratio meets the signal-to-noise ratio threshold. If the current signal-to-noise ratio does not meet the signal-to-noise ratio threshold, re-acquire the adjusted noise rate, and determine the signal-to-noise ratio corresponding to the adjusted noise rate based on the adjusted noise rate.

[0071] In this embodiment, the electronic device can pre-set and store the signal-to-noise ratio (SNR) threshold, judge the current SNR and the SNR threshold, and if the current SNR does not meet the SNR threshold, re-acquire the adjusted noise rate, and determine the SNR corresponding to the adjusted noise rate based on the adjusted noise rate.

[0072] In some implementations, when the current signal-to-noise ratio is greater than the signal-to-noise ratio threshold, the second optical lens is adjusted, the field of view corresponding to the adjusted second optical lens is obtained, the noise rate corresponding to the field of view is calculated, the adjusted noise rate is obtained again, and the signal-to-noise ratio corresponding to the noise rate is determined based on the noise rate.

[0073] Step S170: If the current signal-to-noise ratio meets the signal-to-noise ratio threshold, determine the range for the electronic device to search for the target mobile terminal based on the current signal-to-noise ratio.

[0074] In some implementations, when the current signal-to-noise ratio (SNR) is equal to a SNR threshold, the electronic device can determine the range within which it searches for the target mobile terminal based on the current SNR.

[0075] In some implementations, the electronic device can store the correspondence between signal-to-noise ratio and the range of the target mobile terminal to be searched. The electronic device can determine the range of the target mobile terminal to be searched based on the signal-to-noise ratio and the correspondence.

[0076] In some implementations, the electronic device can preset and store a signal-to-noise ratio (SNR) threshold. When the second optical lens is rotated, the field of view increases, the noise received by the lidar system increases, and the noise rate also increases. Then, the SNR corresponding to the field of view decreases. When the SNR reaches the SNR threshold, there is a maximum field of view corresponding to the SNR, thereby determining the range of the electronic device searching for the target mobile terminal.

[0077] In some implementations, the target mobile terminal may include a drone, but this is not a limitation. See also... Figure 3 , Figure 3 This diagram illustrates the echoes from a UAV at different field-of-view angles at 500m using the lidar search method provided in this embodiment of the application. Figure 3 (a) and Figure 3 (b) illustrates the case where the noise rate is higher than the laser detector's saturation count rate; Figure 3 (c) Figure 3 (d) Figure 3 (e) Figure 3 The field of view angles used in (f) are 0.9 mrad, 0.8 mrad, 0.6 mrad, and 0.5 mrad, respectively. Figure 3 (c) Figure 3 (d) Figure 3 (e) Figure 3 (f) shows the case where the noise rate is lower than the laser detector's saturation count rate. Figure 3 (c) Figure 3 (d) Figure 3 (e) Figure 3 (f) illustrates the echoes at different noise rates.

[0078] Please see Figure 4 , Figure 4 This diagram illustrates the echo histogram of a UAV using the lidar search method provided in this embodiment of the application in a dark environment at a distance of 500m. Figure 4 (a) Figure 4 (b) Figure 4 (c) Figure 4 (d) The field of view angles are 40 mrad, 30 mrad, 25 mrad, and 20 mrad, respectively. Figure 4 (a) Figure 4 (b) Figure 4 (c) Figure 4 (d) shows that the signal-to-noise ratio (SNR) gradually increases as the field of view decreases; that is, the SNR is related to the field of view. Please refer to [link / reference]. Figure 5 , Figure 5 This diagram illustrates the search results of a UAV at different distances using the lidar search method provided in this embodiment. Figure 5 (a) Figure 5 (b) Figure 5 (c) Figure 5 (d) The field of view angles are 40 mrad, 30 mrad, 25 mrad, and 20 mrad, respectively. Figure 5 (a) Figure 5 (b) Figure 5 (c) Figure 5 (d) shows that the drone is too far away, and even if the noise rate does not exceed the saturation count rate of the laser detector, the signal-to-noise ratio of the drone echo cannot be identified.

[0079] Please see Figure 6 , Figure 6 This illustration shows two sets of UAV echo models at similar distances but different field-of-view angles, representing the lidar search method provided in this application. Figure 6 (a) is a histogram of the counts of a target with a field of view of 32 mard and 160 mrad located at approximately 125 m. Figure 6 (b) is the count histogram of targets located at 75m with field of view angles of 160mard and 220mard. The target distance was calibrated using a laser rangefinder, and the echo photon count was fitted using Gaussian fitting to obtain the center value of the echo photons. Figure 6 (a) and Figure 6 (b) The rightmost waveform represents the brick tower and other buildings 540 meters away. Figure 6 (b) The middle waveform represents trees. When clouds are present due to fog, backscattering from atmospheric particles produces a gamma distribution, with a large number of photons appearing at the initial position of the clouds. Since the air humidity at the experimental site is close to 70%, the center of the first backscattering can be chosen as the zero point of time to calculate the distance between the UAV and the electronic equipment. According to Figure 6 (a) The corresponding actual distances are 126.56m and 122.33m, according to Figure 6 (b) The calculated actual distances are 72.4m and 76.2m. From Figure 6 It can be concluded that the signal-to-noise ratio decreases with increasing field of view. When clouds are present due to fog, backscattering from atmospheric particles produces a gamma distribution, with a large number of photons appearing at the initial position of the clouds. Since the air humidity at the experimental site is close to 70%, we can choose the center of the first backscattering as the zero point of time to calculate the distance between the target and us. Figure 6 (a) The corresponding experimentally calculated actual distances are 126.56m and 122.33m, according to Figure 6 (b) The calculated actual distances are 72.4m and 76.2m. Figure 6 This demonstrates that SNR decreases as FOV increases.

[0080] Please see Figure 7 , Figure 7 The diagram shows the actual photon echoes of a UAV at different distances in three field-of-view angles using the lidar search method provided in this application embodiment. Figure 7 (a) Figure 7 (b) Figure 7 (c) The corresponding field angles are 32 mrad, 160 mrad, and 220 mrad, respectively. Figure 7 It can be concluded that in a low-noise environment, the signal-to-noise ratio gradually decreases with increasing distance. Table 1 shows... Figure 7 Data on the field of view, correction distance, measurement distance, error distance, and distance variance.

[0081] Table 1

[0082]

[0083] according to Figure 3 , Figure 4 , Figure 5 , Figure 6 as well as Figure 7 It can be concluded that the larger the field of view, the smaller the signal-to-noise ratio. Therefore, after determining the signal-to-noise ratio, there exists a maximum field of view for searching target terminal devices to expand the search range and speed up the target search. In low-noise environments at night, the field of view can be expanded by an order of magnitude. In high-noise environments during the day, the key to searching for target mobile terminals is noise suppression.

[0084] The lidar search method provided in this application includes a lidar search system comprising a laser emitting device, a laser detection device, a time-correlated single-photon counting device, and electronic equipment. The lidar search system can adjust the laser detection device to increase the receiving field of view. The higher the received noise rate, the lower the signal-to-noise ratio. When the signal-to-noise ratio reaches the signal-to-noise ratio threshold, there is a larger range for searching target mobile terminals. In nighttime environments, the range for searching target mobile terminals is even larger, thereby expanding the search range and improving the efficiency of searching for target mobile terminals.

[0085] Please see Figure 8 , Figure 8 A block diagram of a lidar search device according to an embodiment of this application is shown. This lidar search device 300 is applied to the aforementioned electronic device, and will be discussed below. Figure 8 The block diagram shown illustrates that the lidar search device 300 includes: an information acquisition module 310, a transmittance determination module 320, a photon quantity determination module 330, a noise rate determination module 340, a signal-to-noise ratio determination module 350, a judgment module 360, and a search range determination module 370, wherein:

[0086] The information acquisition module 310 is used to acquire the time difference between the laser detector searching for the echo signal and the most recent laser signal emitted by the laser emitter, as well as the field of view corresponding to the second optical lens.

[0087] The transmittance determination module 320 is used to determine the unidirectional transmittance of the laser signal of the lidar search system on the horizontal path based on the time difference.

[0088] Furthermore, the transmittance determination module 320 includes: a distance determination submodule and a unidirectional transmittance determination submodule, wherein:

[0089] The distance determination submodule is used to determine the distance between the electronic device and the target mobile terminal based on the time difference.

[0090] The unidirectional transmittance determination submodule is used to determine the unidirectional transmittance of the laser signal of the lidar search system on the horizontal path based on the distance between the electronic device and the target mobile terminal.

[0091] Furthermore, the unidirectional transmittance determination submodule includes: a first formula calculation unit and a second formula calculation unit, wherein:

[0092] The first formula calculation unit is used to determine the unidirectional transmittance of the laser signal of the lidar search system on the horizontal path based on formula (1). :

[0093] (1)

[0094] in, The unidirectional transmittance of the laser signal of the lidar search system along the horizontal path is characterized. Characterizing the absorption coefficient of atmospheric molecules, Characterizing the atmospheric aerosol absorption coefficient, Characterizing the scattering coefficient of atmospheric molecules, The scattering coefficient characterizes atmospheric aerosol particles, and R characterizes the distance between the electronic device and the mobile terminal. Characterizing the atmospheric extinction coefficient;

[0095] The second formula calculation unit is used to determine the atmospheric extinction coefficient based on formula (2). :

[0096] (2)

[0097] in, The atmospheric extinction coefficient is represented by D, and atmospheric visibility is represented by D. The wavelength is represented by q, and the correction factor is represented by q.

[0098] The photon count determination module 330 is used to determine the number of photons in the echo signal based on the transmittance.

[0099] Furthermore, the photon quantity determination module 330 includes: a third formula calculation submodule and a fourth formula calculation submodule, wherein:

[0100] The third formula calculation submodule is used to determine the echo signal power of the lidar search system based on formula (3). :

[0101] (3)

[0102] in, Characterizing the echo signal power of the lidar search system, Characterizing the target scattering coefficient, The unidirectional transmittance of the laser signal of the lidar search system along the horizontal path is characterized. Characterizes the luminous efficiency of the first optical lens. Characterizing the luminous efficiency of the second optical lens, The angle between the optical axis of the laser emitter and the normal of the mobile terminal is used to characterize the angle between them. Characterizing the reflective area of ​​the target mobile terminal. Characterizing the area of ​​the reflected light spot of the target mobile terminal, R represents the area of ​​the second optical lens, and R represents the distance between the electronic device and the mobile terminal. Characterizes the peak power of the signal emitted by the laser emitter;

[0103] The fourth formula calculation submodule is used to determine the number of photons in the echo signal based on formula (4). :

[0104] (4)

[0105] in, The number of photons representing the echo signal, Characterizing the echo signal power of the lidar search system, Characterizing the frequency of the laser signal, Characterizing wavelength, Characterizing the speed of light h represents the photon energy, and h represents Planck's constant.

[0106] The noise rate determination module 340 is used to determine the noise rate corresponding to the scene to be searched based on the transmittance and the field of view.

[0107] Furthermore, the noise rate determination module 340 includes: a fifth formula calculation submodule, wherein:

[0108] The fifth formula calculation submodule is used to determine the noise rate corresponding to the scene to be searched based on formula (5). :

[0109] (5)

[0110] in, Characterizes the noise rate corresponding to the scene to be searched. The wavelength is represented by h, and Planck's constant is represented by h. E represents the speed of light, and E represents the solar spectral irradiance. Characterizing the target scattering coefficient, The unidirectional transmittance of the laser signal of the lidar search system along the horizontal path is characterized. Characterizing the area of ​​the second optical lens, Characterizing the luminous efficiency of the second optical lens, Characterizing the bandwidth of the bandpass filter, The solar altitude angle is represented by θr, and the field of view angle received by the laser detector is represented by θr.

[0111] The signal-to-noise ratio determination module 350 is used to determine the current signal-to-noise ratio based on the number of photons and the noise rate.

[0112] The judgment module 360 ​​is used to determine whether the current signal-to-noise ratio meets the signal-to-noise ratio threshold. If the current signal-to-noise ratio does not meet the signal-to-noise ratio threshold, the adjusted noise rate is re-acquired, and the signal-to-noise ratio corresponding to the adjusted noise rate is determined based on the adjusted noise rate.

[0113] The search range determination module 370 determines the search range of the electronic device for the target mobile terminal based on the current signal-to-noise ratio if the current signal-to-noise ratio meets the signal-to-noise ratio threshold.

[0114] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the above-described device and module can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0115] In the several embodiments provided in this application, the coupling between modules can be electrical, mechanical, or other forms of coupling.

[0116] Furthermore, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0117] Please see Figure 9 This diagram illustrates a structural block diagram of an electronic device 200 provided in an embodiment of this application. The electronic device 200 can be a smartphone, tablet computer, e-reader, or other electronic device capable of running applications. The electronic device 200 in this application may include one or more of the following components: a processor 210, a memory 220, and one or more applications, wherein the one or more applications can be stored in the memory 220 and configured to be executed by one or more processors 210, and the one or more applications are configured to perform the methods described in the foregoing method embodiments.

[0118] The processor 210 may include one or more processing cores. The processor 210 connects to various parts within the electronic device 200 using various interfaces and lines, and performs various functions and processes data by running or executing instructions, programs, code sets, or instruction sets stored in the memory 220, and by calling data stored in the memory 220. Optionally, the processor 210 may be implemented using at least one hardware form of Digital Signal Processing (DSP), Field-Programmable Gate Array (FPGA), or Programmable Logic Array (PLA). The processor 210 may integrate one or a combination of several of the following: Central Processing Unit (CPU), Graphics Processing Unit (GPU), and modem. The CPU primarily handles the operating system, user interface, and applications; the GPU is responsible for rendering and drawing the content to be displayed; and the modem handles wireless communication. It is understood that the modem may also not be integrated into the processor 210 and may be implemented separately using a communication chip.

[0119] The memory 220 may include random access memory (RAM) or read-only memory (ROM). The memory 220 can be used to store instructions, programs, code, code sets, or instruction sets. The memory 220 may include a program storage area and a data storage area. The program storage area may store instructions for implementing an operating system, instructions for implementing at least one function (such as touch functionality, sound playback functionality, image playback functionality, etc.), and instructions for implementing the various method embodiments described below. The data storage area may also store data created by the terminal 100 during use (such as phonebook data, audio and video data, chat log data, etc.).

[0120] Please see Figure 10 This diagram illustrates a structural block diagram of a computer-readable storage medium provided in an embodiment of this application. The computer-readable medium 400 stores program code that can be called by a processor to execute the methods described in the above method embodiments.

[0121] Computer-readable storage medium 400 may be an electronic memory such as flash memory, EEPROM (Electrically Erasable Programmable Read-Only Memory), EPROM, hard disk, or ROM. Optionally, computer-readable storage medium 400 includes a non-transitory computer-readable storage medium. Computer-readable storage medium 300 has storage space for program code 410 that performs any of the method steps described above. This program code can be read from or written to one or more computer program products. The program code 410 may be compressed, for example, in a suitable form.

[0122] In summary, the lidar search system and method provided in this application include a lidar system comprising a laser emitting device, a laser detection device, a time-correlated single-photon counting device, and electronic equipment. The laser detection device can be adjusted to obtain the time difference and field of view between the laser detector's search echo signal and the most recently emitted laser signal. Based on this time difference and field of view, the number of photons in the echo signal and the noise rate corresponding to the scene to be searched are determined. Furthermore, the current signal-to-noise ratio (SNR) can be determined based on the number of photons and the noise rate. When the current SNR meets the SNR threshold, a larger search range exists for searching the target mobile terminal, thereby expanding the search range and improving the efficiency of searching for the target mobile terminal.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A lidar search system, characterized in that, It includes a laser emitting device, a laser detection device, a time-correlated single-photon counting device, and an electronic device. The laser emitting device is connected to the time-correlated single-photon counting device, the laser detection device is connected to the time-correlated single-photon counting device, and the time-correlated single-photon counting device is connected to the electronic device. The laser emitting device is used to emit a laser signal, wherein the laser signal is transmitted to the scene to be searched along the emission optical path of the laser signal; The laser detection device is used to receive the echo signal reflected after the laser signal is emitted and encounters the target mobile terminal in the scene to be searched, and to adjust the laser detection device to change the field of view. The laser detection device includes a laser detector and a second optical lens. The second optical lens is disposed before the optical path of the laser detector receiving the echo signal. The second optical lens is used to focus the echo signal onto the laser detector. When the angle of the second optical lens changes, the current signal-to-noise ratio corresponding to the second optical lens changes. When the current signal-to-noise ratio is greater than the signal-to-noise ratio threshold, the second optical lens is adjusted to obtain the field of view corresponding to the adjusted second optical lens. The time-correlated single-photon counting device is used to store the time difference between searching the echo signal and the most recent laser signal emission; The electronic device is used to determine the range of the target mobile terminal based on the time difference; The lidar search system adjusts the laser detection device to increase the receiving field of view. The higher the received noise rate, the lower the signal-to-noise ratio. When the signal-to-noise ratio reaches the signal-to-noise ratio threshold, there is a large range for searching target mobile terminals.

2. The system according to claim 1, characterized in that, The laser emitting device includes a laser emitter and a first optical lens, wherein the first optical lens is disposed after the emitting optical path of the laser emitter; The first optical lens is used to disperse the laser signal into the scene to be searched. When the angle of the first optical lens changes, the emission angle corresponding to the first optical lens changes.

3. The system according to claim 2, characterized in that, When the angle of the second optical lens rotates, the field of view corresponding to the second optical lens changes, and the current signal-to-noise ratio changes.

4. The system according to claim 2, characterized in that, The laser detection device further includes a bandpass filter, which is disposed between the laser detector and the second optical lens; The bandpass filter is used to filter out signals other than the echo signal.

5. A lidar search method, characterized in that, The method is applied to the electronic device of claim 2, comprising: The time difference between the laser detector searching for the echo signal and the most recent laser signal emitted by the laser emitter, as well as the field of view corresponding to the second optical lens, are obtained. Based on the time difference, the unidirectional transmittance of the laser signal of the lidar search system on the horizontal path is determined; Based on the transmittance, the number of photons in the echo signal is determined; Based on the transmittance and the field of view, the noise rate corresponding to the scene to be searched is determined; The current signal-to-noise ratio is determined based on the number of photons and the noise rate; Determine whether the current signal-to-noise ratio (SNR) meets the SNR threshold. If the current SNR does not meet the SNR threshold, re-acquire the adjusted noise rate and determine the SNR corresponding to the adjusted noise rate based on the adjusted noise rate. If the current signal-to-noise ratio (SNR) meets the SNR threshold, the range for the electronic device to search for the target mobile terminal is determined based on the current SNR.

6. The method according to claim 5, characterized in that, Determining the unidirectional transmittance of the laser signal of the lidar search system along the horizontal path based on the time difference includes: Based on the time difference, the distance between the electronic device and the target mobile terminal is determined; Based on the distance between the electronic device and the target mobile terminal, the unidirectional transmittance of the laser signal of the lidar search system on the horizontal path is determined.

7. The method according to claim 6, characterized in that, Determining the unidirectional transmittance of the laser signal of the lidar search system along the horizontal path based on the distance between the electronic device and the target mobile terminal includes: The unidirectional transmittance of the laser signal of the lidar search system on the horizontal path is determined based on formula (1). : （1） in, The unidirectional transmittance of the laser signal of the lidar search system along the horizontal path is characterized. Characterizing the absorption coefficient of atmospheric molecules, Characterizing the atmospheric aerosol absorption coefficient, Characterizing the scattering coefficient of atmospheric molecules, The scattering coefficient characterizes atmospheric aerosol particles, and R characterizes the distance between the electronic device and the mobile terminal. Characterizing the atmospheric extinction coefficient; Atmospheric extinction coefficient determined based on formula (2) : （2） in, The atmospheric extinction coefficient is represented by D, and atmospheric visibility is represented by D. The wavelength is represented by q, and the correction factor is represented by q.

8. The method according to claim 5, characterized in that, Determining the number of photons in the echo signal based on the transmittance includes: The echo signal power of the lidar search system is determined based on formula (3). : （3） in, Characterizing the echo signal power of the lidar search system, Characterizing the target scattering coefficient, The unidirectional transmittance of the laser signal of the lidar search system along the horizontal path is characterized. Characterizes the luminous efficiency of the first optical lens. Characterizing the luminous efficiency of the second optical lens, The angle between the optical axis of the laser emitter and the normal of the mobile terminal is used to characterize the angle between them. Characterizing the reflective area of ​​the target mobile terminal. Characterizing the area of ​​the reflected light spot of the target mobile terminal, R represents the area of ​​the second optical lens, and R represents the distance between the electronic device and the mobile terminal. Characterizes the peak power of the signal emitted by the laser emitter; The number of photons in the echo signal is determined based on formula (4). : （4） in, The number of photons representing the echo signal, Characterizing the echo signal power of the lidar search system, Characterizing the frequency of the laser signal, Characterizing wavelength, Characterizing the speed of light h represents the photon energy, and h represents Planck's constant.

9. The method according to claim 5, characterized in that, The step of determining the noise rate corresponding to the scene to be searched based on the transmittance and the field of view includes: The noise rate corresponding to the scene to be searched is determined based on formula (5). : （5） in, Characterizes the noise rate corresponding to the scene to be searched. The wavelength is represented by h, and Planck's constant is represented by h. E represents the speed of light, and E represents the solar spectral irradiance. Characterizing the target scattering coefficient, The unidirectional transmittance of the laser signal of the lidar search system along the horizontal path is characterized. Characterizing the area of ​​the second optical lens, Characterizing the luminous efficiency of the second optical lens, Characterizing the bandwidth of a bandpass filter, The solar altitude angle is represented by θr, and the field of view angle received by the laser detector is represented by θr.

10. The method according to claim 5, characterized in that, The laser radar search system according to any one of claims 1-4 searches for target mobile terminals, and the method is applied to electronic devices.

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