TOF Laser Radar System Based on Two Wavelengths and Its Interference Prevention Method

Abstract

A two-wavelength based TOF lidar system and its interference prevention method. The emission unit of the lidar includes a first emission unit for emitting a laser pulse with a wavelength of λ1 and a second emission unit for emitting a laser pulse with a wavelength of λ2. The detector includes a first detector for detecting a laser pulse signal with a wavelength of λ1 and a second detector for detecting a laser pulse signal with a wavelength of λ2. The lidar can operate in both a general mode and an interference prevention mode. When set to the interference prevention mode, the polling mode, the synchronization mode, the λ1 mode, and the λ2 mode can be switched according to the interference situation, enabling the interference prevention function. Through cooperation with the two-wavelength polling switching, it enables the monitoring and processing of interference signals by the lidar, can well handle various interference sources, and has a high interference prevention ability.

Description

Technical Field

[0001] The present invention relates to the technical field of lidar, and in particular, to a two-wavelength-based TOF lidar system and an interference prevention method thereof.

Background Art

[0002] Lidar is an abbreviation for a laser detection and ranging system, which detects information such as the three-dimensional structure, spatial position, surface reflectivity, and motion state of an object by emitting and receiving a laser beam. In a lidar based on the Time Of Flight (TOF) method, the flight time of the laser beam is measured and the echo signal is analyzed to sense the target information. The time-of-flight lidar generally faces interference from signals of the same frequency during actual operation, and it is common for the detection performance of the lidar to be affected. The interference sources include natural light, illumination light sources, lidars of the same frequency, and malicious interference sources of the same frequency. A lidar system generally employs a single-wavelength laser pulse to sense an object, and the system architecture includes assemblies such as a single-wavelength laser source, an optical system, a beam deflection device, and a detector.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The interference prevention techniques used in conventional single-wavelength TOF lidars include finite pulse coding, pulse amplitude modulation, pulse width modulation, pulse interval modulation, etc. These interference prevention techniques can reduce the influence of interference sources to a certain extent, but they cannot well handle complex use cases, especially those in the field of autonomous driving.

[0004] Here, the finite pulse encoding technology and the pulse interval modulation technology remove some interference signal sources while affecting the scanning frequency of the lidar, increasing the design complexity and hardware cost of the lidar. Also, the lidar system using these two technologies is prone to being blinded by interference sources. The pulse amplitude modulation technology achieves the effect of anti-interference by improving the energy of the laser pulse and increasing the signal-to-noise ratio of the echo signal. Such technology is effective against interference caused by natural light and illumination light sources, but its effectiveness against the same-frequency lidar and malicious interference sources is not obvious. The pulse width modulation technology realizes the role of anti-interference by changing the pulse shape of the laser pulse and adding a pulse width limit value for identification during echo signal processing. In addition to the fact that such technology cannot eliminate the influence of the same-frequency interference source, it also has a certain impact on the ranging performance of the lidar.

Means for Solving the Problem

[0005] An object of the present invention is to solve at least one of the technical problems existing in the prior art.

[0006] Therefore, the present invention proposes a two-wavelength-based TOF lidar system and its anti-interference method, and realizes the anti-interference ability of the lidar system in a mode of cooperating with the polling switching of two wavelengths.

[0007] According to the anti-interference method of the two-wavelength-based TOF lidar system according to an embodiment of the present invention, when the lidar is set to the anti-interference mode and both the first detector and the second detector are set to the enabled state, specifically, it includes the following first step to the fifth step. First step: Start the lidar system. Second step: Set the control and signal processing module to the anti-interference mode. Third step: The first case: When the pulse laser emission mode enters the λ1 mode in the default state, the second detector enters the interference monitoring state. Next, it is determined whether the second detector can monitor the interference. When the second detector fails to continuously monitor the interference for N frames, where N is a positive integer greater than or equal to 1, it automatically switches to the λ2 mode, and the first detector enters the interference monitoring state. When the second detector can monitor the interference, it automatically switches to the polling mode. The second case: When the pulse laser emission mode enters the λ2 mode in the default state, the first detector enters the interference monitoring state. Next, it is determined whether the first detector can monitor the interference. When the first detector fails to continuously monitor the interference for N frames, where N is a positive integer greater than or equal to 1, it automatically switches to the λ1 mode, and the second detector enters the interference monitoring state. When the first detector can monitor the interference, it automatically switches to the polling mode. The fourth step: In the polling mode, when the first detector performs signal detection, the second detector enters the interference monitoring state. When the second detector performs signal detection, the first detector enters the interference monitoring state, and the control and signal processing module performs interference prevention processing. The fifth step: The first case: When the first detector and the second detector can continuously monitor the interference simultaneously for M frames, where M is a positive integer greater than or equal to 1, and the interference signal is greater than the set threshold, it automatically switches to the synchronization mode, and the control and signal processing module performs interference prevention processing and determines the degree of interference. When it is determined that the degree of interference is less than the threshold for K consecutive frames, where K is a positive integer greater than or equal to 1, it automatically switches to the polling mode. When it is determined that the degree of interference is greater than or equal to the threshold for K consecutive frames, where K is a positive integer greater than or equal to 1, it automatically switches to the synchronization mode. The second case: When the first detector and the second detector cannot continuously monitor the interference simultaneously for M frames, where M is a positive integer greater than or equal to 1, and the interference signal is less than or equal to the set threshold, it automatically switches to the polling mode.

[0008] The present invention includes a control and signal processing module, a transmitting unit, a transmitting optical system, a beam deflecting device, a detection object, a receiving optical system, and a detector. The control and signal processing module is used to control the laser emission of the transmitting unit, the reception of the detector, and the processing of the echo signal. The transmitting unit is used to emit a laser pulse. The transmitting unit includes a first transmitting unit for emitting a laser pulse with a wavelength of λ1 and a second transmitting unit for emitting a laser pulse with a wavelength of λ2. The transmitting optical system is composed of the emission optical path of the first transmitting unit and the emission optical path of the second transmitting unit. The beam deflecting device is used for deflecting the laser beam to realize scanning within a predetermined field of view. The detection object is an object detectable within the predetermined field of view. The receiving optical system is composed of the reception optical paths of the first detector and the second detector. The detector includes a first detector and a second detector. The first detector is used to detect a laser pulse signal with a wavelength of λ1, and the second detector is used to detect a laser pulse signal with a wavelength of λ2. Further provided is a two-wavelength based TOF laser radar system for realizing an anti-interference method.

[0009] The beneficial effects of the present invention are as follows: By adopting the mode of two light sources and two detectors, the design of a two-wavelength laser radar system is realized. Through the polling switching of the two light sources and two detectors, real-time monitoring of interference is realized. Through the cooperation of the two light sources and two detectors, the processing of interference signals by the laser radar is realized. The anti-interference method of the present invention can well cope with various interference sources and has a high anti-interference ability.

[0010] According to an embodiment of the present invention, the steps for the control and signal processing module to perform interference information processing in the polling mode are as follows: Step (1): Calculate the interference intensities of the first detector and the second detector. Step (2): Compare the interference intensities of the first detector and the second detector. Step (3): Determine primary data and secondary data. Step (4): Output the primary data and the secondary data.

[0011] According to an embodiment of the present invention, the steps of the control and signal processing module performing interference information processing in the synchronous mode are as follows: Step 1: Obtain the detection information of the first detector and the second detector once, including but not limited to distance, angle, reflectivity, and reflection intensity. Step 2: Determine whether the detection data of the first detector and the second detector are within a predetermined deviation range or satisfy a predetermined relationship, and determine whether there is interference in this detection. Step 3: When there is interference, this detection is invalid; when there is no interference, this detection data is valid. Step 4: Output the valid data of the first detector and the second detector simultaneously.

[0012] According to an embodiment of the present invention, any one of a vertical cavity surface emitting laser, an edge emitting laser, and a fiber laser is adopted as the first emission unit, and any one of a vertical cavity surface emitting laser, an edge emitting laser, and a fiber laser is adopted as the second emission unit.

[0013] According to an embodiment of the present invention, the same type of laser light source is adopted as the first emission unit and the second emission unit, or different types of laser light sources are adopted as the first emission unit and the second emission unit.

[0014] According to an embodiment of the present invention, a single laser is adopted as both the first emission unit and the second emission unit, or a laser array is adopted as both the first emission unit and the second emission unit.

[0015] According to an embodiment of the present invention, the emission optical system includes a first aperture, a second aperture, a first collimator lens, a second collimator lens, a first mirror, and a second mirror. The first aperture, the first collimator lens, and the second mirror constitute the emission optical path of the first emission unit. The second aperture, the second collimator lens, the first mirror, and the second mirror constitute the emission optical path of the second emission unit. After the laser beams emitted by the first emission unit and the second emission unit pass through the second mirror, their optical paths overlap, and the beam after the optical paths overlap is emitted to the beam deflector.

[0016] According to an embodiment of the present invention, the receiving optical system includes a third mirror, a fourth mirror, a first filter, a second filter, a first receiving lens group, a second receiving lens group, and a third aperture. The third mirror, the first filter, the first receiving lens group, and the third aperture constitute the receiving optical path of the first detector. The third mirror, the fourth mirror, the second filter, the second receiving lens group, and the third aperture constitute the receiving optical path of the second detector. After the laser pulse with a wavelength of λ1 and / or λ2 emitted from the beam deflector reaches the first mirror, the laser pulse that is one of λ1 and / or λ2 is totally reflected by the third mirror and then reflected by the fourth mirror, and then reaches the second detector through the second filter, the second receiving lens group, and the third aperture. The laser pulse of the other wavelength passes through the third mirror and reaches the first detector through the first filter, the first receiving lens group, and the third aperture.

[0017] According to an embodiment of the present invention, the first detector is located at the focal plane position of the first receiving lens group, and the second detector is located at the focal plane position of the second receiving lens group.

[0018] Other features and advantages of the present invention are described in the following specification, and will be partially apparent from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention are realized and achieved by the structures specifically pointed out in the specification and the drawings.

[0019] To make the above objects, features, and advantages of the present invention more understandable, the following particularly preferred embodiments will be given, and with reference to the accompanying drawings, the following will be described in detail as follows.

[0020] To more clearly explain the technical means in the embodiments of the present invention or in the prior art, in the following, the drawings necessary for the description of the embodiments or the prior art will be briefly introduced. Of course, the drawings in the following description are only some of the embodiments described in this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

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Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0022] To make the objectives, technical means and advantages of the embodiments of the present invention clearer, the technical means in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Naturally, the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are included in the protection scope of the present invention.

[0023] Hereinafter, with reference to the drawings, a two-wavelength-based TOF laser radar system and its interference prevention method according to the embodiments of the present invention will be specifically described.

[0024] As shown in FIG. 1, the two-wavelength-based TOF laser radar system according to the present invention realizes the interference prevention ability of the laser radar system through cooperation with the two-wavelength acousto-optic switching, and includes a control and signal processing module, a transmitting unit, a transmitting optical system, a beam deflector, a detection target, a receiving optical system, and a detector.

[0025] The control and signal processing module is used to control the laser emission of the transmitting unit, the reception of the detector, and the processing of the echo signal.

[0026] The transmitting unit is used to emit laser pulses. The transmitting unit includes a first transmitting unit for emitting laser pulses with a wavelength of λ1 and a second transmitting unit for emitting laser pulses with a wavelength of λ2. For example, λ1 = 905 nm and λ2 = 1550 nm.

[0027] The emission optical system is composed of the emission optical paths of the first emission unit and the second emission unit. Specifically, the emission optical system includes a laser collimator lens, a reflector, an aperture, etc. The emission optical system includes a first aperture, a second aperture, a first collimator lens, a second collimator lens, a first reflector, and a second reflector. The first aperture, the first collimator lens, and the second reflector constitute the emission optical path of the first emission unit, and the second aperture, the second collimator lens, the first reflector, and the second reflector constitute the emission optical path of the second emission unit.

[0028] The beam deflection device is used for deflecting the laser beam to achieve scanning within a predetermined field of view range, for example, a 120° * 25° scan, and may be a rotating prism, a galvanometer mirror, or a micro-electro-mechanical system (MEMS) galvanometer mirror.

[0029] The detection target object is an object that can be detected within the detection field angle range.

[0030] The receiving optical system is composed of the receiving optical paths of the first detector and the second detector. Specifically, the receiving optical system includes a lens, a reflector, an aperture, etc. The receiving optical system includes a third reflector, a fourth reflector, a first filter, a second filter, a first receiving lens group, a second receiving lens group, and a third aperture. The third reflector, the first filter, the first receiving lens group, and the third aperture constitute the receiving optical path of the first detector, and the third reflector, the fourth reflector, the second filter, the second receiving lens group, and the third aperture constitute the receiving optical path of the second detector.

[0031] The detector includes a first detector and a second detector. The first detector is used to detect a laser pulse signal with a wavelength of λ1, and the second detector is used to detect a laser pulse signal with a wavelength of λ2. As the first detector, any one of a PIN photodiode, an avalanche diode (APD), a silicon photomultiplier tube, and a single photon avalanche diode (SPAD) is adopted. For the same reason, as the second detector, any one of a PIN photodiode, an avalanche diode (APD), a silicon photomultiplier tube, and a single photon avalanche diode (SPAD) is adopted.

[0032] As shown in FIG. 2, as the first emission unit, any one of laser emission light sources such as a vertical cavity surface emitting laser (VCSEL), an edge emitting laser (EEL), and a fiber laser is adopted.

[0033] As the second emission unit, any one of laser emission light sources such as a vertical cavity surface emitting laser (VCSEL), an edge emitting laser (EEL), and a fiber laser is adopted.

[0034] The first emission unit emits a laser pulse with a wavelength of λ1, and the second emission unit emits a laser pulse with a wavelength of λ2. The positions of the first emission unit and the second emission unit may be equivalently exchanged.

[0035] The first emission unit and the second emission unit adopt the same type of laser light source, or the first emission unit and the second emission unit adopt different types of laser light sources.

[0036] Both the first emission unit and the second emission unit adopt a single laser, or both the first emission unit and the second emission unit adopt a laser array. When a laser array is adopted as the emission unit, the emission unit includes at least one first emission unit and one second emission unit.

[0037] Considering the temperature drift of the laser, it is necessary to meet the following conditions.

Number

[0038] Here, Δλ1 represents the maximum wavelength temperature drift range of the first emission unit within the operating temperature range of the lidar, and Δλ2 represents the maximum wavelength temperature drift range of the second emission unit within the operating temperature range of the lidar.

[0039] As shown in Figure 3, the first aperture and the second aperture are used to reduce the crosstalk between laser beams and isolate the lasers from each other.

[0040] The first collimator lens group is used for collimating the laser beam emitted by the first emission unit, and may include collimation in the X direction (horizontal direction) and collimation in the Y direction (vertical direction), or may include only collimation in a single direction. The first collimator lens is provided selectively and may be provided according to whether it is necessary to collimate the laser beam of the first emission unit.

[0041] The second collimator lens group is used for collimating the laser beam emitted by the second emission unit, and may include collimation in the X direction (horizontal direction) and collimation in the Y direction (vertical direction), or may include only collimation in a single direction. The second collimator lens is provided selectively and may be provided according to whether it is necessary to collimate the laser beam of the second emission unit.

[0042] The first reflector is a total reflector for λ2, the second reflector is transparent to λ1 and totally reflects λ2. After the laser beams emitted by the first emission unit and the second emission unit pass through the second reflector, their optical paths overlap, and the beam after the optical paths overlap is emitted to the beam deflection device.

[0043] As shown in FIG. 4, the laser pulse reflected from the object to be detected reaches the third reflector after passing through the beam deflection device. The third reflector is transparent to λ1 and totally reflects λ2, and the fourth reflector is a total reflector for λ2. The first filter prevents reflection of the reflected echo of λ1 and can filter and remove the reflected echo of λ2, and the second filter prevents reflection of the reflected echo of λ2 and can filter and remove the reflected echo of λ1. The first receiving lens group and the second receiving lens group are used to converge the received echo. The third aperture serves to isolate the light rays between different detection units and reduce the crosstalk between different detector units. The first detector is located at the focal plane position of the first receiving lens group, and the second detector is located at the focal plane position of the second receiving lens group. The positions of the first detector and the second detector are equivalently exchanged.

[0044] After the laser pulse with a wavelength of λ1 and / or λ2 emitted from the beam deflection device reaches the first reflector, the laser pulse with one of the wavelengths of λ1 and / or λ2 is totally reflected by the third reflector and then reflected by the fourth reflector, and then reaches the second detector through the second filter, the second receiving lens group and the third aperture, and the laser pulse with the other wavelength passes through the third reflector and reaches the first detector through the first filter, the first receiving lens group and the third aperture.

[0045] As shown in FIG. 5, regarding the field of view FOV (Field Of View), the area jointly covered by the first detector and the second detector is the field of view FOV of the lidar system. When detecting a certain spatial position, the light emitting unit 1 and the light emitting unit 2 emit laser pulses to this position simultaneously or in sequence.

[0046] As shown in Fig. 6, regarding the laser pulse emission mode, in Fig. 6, the symbol t represents time, t10, t11, t12, t13, t14... represent the times when the first emission unit emits laser pulses, and t20, t21, t22, t23, t24... represent the times when the second emission unit emits laser pulses.

[0047] The lidar has four pulse emission modes, and the four pulse emission modes are respectively the polling mode, the synchronous mode, the λ1 mode, and the λ2 mode.

[0048] In the polling mode, the first emission unit and the second emission unit emit laser pulses by polling in turn. The time intervals between two pulses of the same emission unit may be set to be the same or different. The emission time intervals between adjacent pulses of the first emission unit and the second emission unit may be set to be the same or different. In the polling mode, the point cloud data from the first emission unit and the first detector and the point cloud data from the second emission unit and the second detector may be output in sequence.

[0049] In the synchronous mode, the first emission unit and the second emission unit emit laser pulses synchronously. The time intervals between two pulses of the same emission unit may be set to be the same or different.

[0050] In the λ1 mode, only the first emission unit emits laser pulses, and the time intervals between two pulses may be set to be the same or different.

[0051] In the λ2 mode, only the second emission unit emits laser pulses, and the time intervals between two pulses may be set to be the same or different.

[0052] Each time the first emission unit emits a pulse, the first detector may be in an enabled state (on state), and the second detector may be set to an enabled state or a non-enabled state (off state).

[0053] For the same reason, each time the second emission unit emits a pulse, the second detector may be in an enabled state (on state), and the first detector may be set to an enabled state or a non-enabled state (off state).

[0054] After the laser tube radar system completes the detection of a complete frame, it switches the laser pulse emission mode when starting the next frame.

[0055] As shown in FIG. 7, regarding the laser radar operation mode, the laser radar can operate in either a general mode or an anti-interference mode. When the laser radar operates in the general mode, the laser pulse emission mode of the laser radar may be set to any one of a polling mode, a synchronization mode, a λ1 mode, and a λ2 mode. In the λ1 mode, only the point cloud data from the first emission unit and the first detector are output, and the second detector is in a non-enabled state. In the λ2 mode, only the point cloud data from the second emission unit and the second detector are output, and the first detector is in a non-enabled state. Compared with the λ1 mode and the λ2 mode, the polling mode can output the point cloud data from the first emission unit and the first detector and the point cloud data from the second emission unit and the second detector in sequence. Compared with the λ1 mode and the λ2 mode, the synchronization mode can output the point cloud of two frames at the same time, one frame is from the first emission unit and the first detector, and the other frame is from the second emission unit and the second detector. When set to the anti-interference mode, the polling mode, the synchronization mode, the λ1 mode, and the λ2 mode can be switched according to the interference situation so as to realize the anti-interference function. After the laser tube radar system completes the detection of a complete frame, it switches the operation mode when starting the next frame.

[0056] According to the interference prevention method of the two-wavelength based TOF lidar system as shown in FIG. 8, the lidar is set to the interference prevention mode, and both the first detector and the second detector are set to the enabled state. Specifically, it includes the following first step to the fifth step: First step: Start the lidar system. Second step: Set the control and signal processing module to the interference prevention mode. Third step: First case: When the pulse laser emission mode enters the λ1 mode in the default state, the second detector enters the interference monitoring state. Next, it is determined whether the second detector can monitor interference. When the second detector fails to continuously monitor interference for N frames, where N is a positive integer greater than or equal to 1, it automatically switches to the λ2 mode, and the first detector enters the interference monitoring state. When the second detector can monitor interference, it automatically switches to the polling mode. Second case: When the pulse laser emission mode enters the λ2 mode in the default state, the first detector enters the interference monitoring state. Next, it is determined whether the first detector can monitor interference. When the first detector fails to continuously monitor interference for N frames, where N is a positive integer greater than or equal to 1, it automatically switches to the λ1 mode, and the second detector enters the interference monitoring state. When the first detector can monitor interference, it automatically switches to the polling mode. Fourth step: In the polling mode, when the first detector performs signal detection, the second detector enters the interference monitoring state. When the second detector performs signal detection, the first detector enters the interference monitoring state, and the control and signal processing module performs interference prevention processing. Fifth step: First case: When the first detector and the second detector can continuously monitor interference simultaneously for M frames, where M is a positive integer greater than or equal to 1, and the interference signal is greater than the set threshold, it automatically switches to the synchronization mode, the control and signal processing module performs interference prevention processing, and determines the degree of interference. When it is determined that the interference level is continuously less than the threshold for K frames, where K is a positive integer greater than or equal to 1, automatically switch to the polling mode. When it is determined that the interference level is continuously greater than or equal to the threshold for K frames, where K is a positive integer greater than or equal to 1, automatically switch to the synchronization mode. Second case: When the first detector and the second detector cannot simultaneously monitor interference continuously for M frames, where M is a positive integer greater than or equal to 1, and the interference signal is below the set threshold, automatically switch to the polling mode.

[0057] The steps for the control and signal processing module to process interference information in the polling mode are as follows. Step (1): Calculate the interference intensities of the first detector and the second detector. Step (2): Compare the interference intensities of the first detector and the second detector. Step (3): Determine the primary data and the secondary data. Step (4): Output the primary data and the secondary data.

[0058] The steps for the control and signal processing module to process interference information in the synchronization mode are as follows. Step 1: The single detection information of the first detector and the second detector includes, but is not limited to, distance, angle, reflectivity, and reflection intensity. Step 2: Determine whether the detection data of the first detector and the second detector are within a predetermined deviation range or satisfy a predetermined relationship, and determine whether interference exists in this detection. Step 3: When interference exists, this detection is invalid; when interference does not exist, this detection data is valid. Step 4: Simultaneously output the valid data of the first detector and the second detector.

[0059] When the laser radar is set to the anti-interference mode, both the first detector and the second detector are set to the enabled state. The pulse laser emission mode enters the λ1 mode in the default state and may also be in the λ2 mode by default, or the λ1 mode and the λ2 mode may be equivalently exchanged in the default state setting. It is necessary to explain this.

[0060] Next, taking the default entry into the λ1 mode as an example. In the λ1 mode, when the second detector enters the interference monitoring state and the second detector fails to continuously monitor interference for N frames (N is a positive integer greater than or equal to 1 and can be set as required), it automatically switches to the λ2 mode. If this condition is not met, it enters the polling mode. In the λ2 mode, when the first detector enters the interference monitoring state and the first detector fails to continuously monitor interference for N frames (N is a positive integer greater than or equal to 1 and can be set as required), it automatically switches to the λ1 mode. If this condition is not met, it enters the polling mode.

[0061] As a condition for considering that interference exists in each frame, if the ratio of the number of interferences that the detector can monitor during the detection period of one frame to the total number of data points in one frame is greater than a certain threshold, it is considered that interference exists. For example, if the data of one frame of the laser radar has 100,000 points, and in the λ1 mode, when the second detector generates more than 5000 detection responses (i.e., at least 5001 detection responses) in the time period of one frame, it is considered that interference exists, and the threshold can be set to 5% at this time. When the second detector generates a total of 5500 detection responses during the period when the first detector completes the detection of a complete frame, it is determined that there is an interference source with a wavelength of λ2. When the second detector generates 4500 detection responses during this period, it is considered that there is no interference source with a wavelength of λ2.

[0062] When the first detector performs signal detection in the polling mode, the second detector enters the interference monitoring state. When the second detector performs signal detection, the first detector enters the interference monitoring state. When starting a frame, the first emission unit and the second emission unit of the lidar poll and emit light (the first emission unit may emit light first, or the second emission unit may emit light first, and the first emission unit and the second emission unit can be equivalently exchanged). When the first emission unit emits light, the first detector is used for echo detection of the object, and the second detector performs interference monitoring. When the second emission unit emits light, the second detector is used for echo detection of the object, and the second detector performs interference monitoring. The control and signal processing module performs interference information processing. As shown in FIG. 9, the interference intensities of the first detector and the second detector are calculated respectively. The one with a low interference intensity is defined as first-level data, and the one with a poor interference intensity is defined as second-level data. The lidar outputs the first-level data and the second-level data simultaneously.

[0063] The interference intensity of the first detector is calculated as the ratio of the number of times the first detector can detect interference during the complete detection period of one frame of data of the second detector to the total number of points of one frame of data. The interference intensity of the second detector is calculated as the ratio of the number of times the second detector can detect interference during the complete detection period of one frame of data of the first detector to the total number of points of one frame of data. When both the first detector and the second detector can monitor the presence of interference, the control and signal processing module calculates the interference signal intensities of the first detector and the second detector. When the predetermined conditions are met, it enters the synchronization mode. The method for determining this condition is as follows: Let the ratio of the number of times the interference signal is detected in one frame of detection of the first detector to the total number of points of one frame of data be T1, and the ratio of the number of times the interference signal is detected in one frame of detection of the second detector to the total number of points of one frame of data be T2. When the situation where T1 is greater than or equal to the threshold set for the first detector and T2 is greater than or equal to the threshold set for the second detector occurs continuously for M frames (M is a positive integer greater than or equal to 1 and can be set according to specific embodiments), it is considered to meet the condition for entering the synchronization mode. For example, when the threshold of the first detector is set to 10%, the threshold of the second detector is set to 15%, M = 1, T1 = 11%, and T2 = 20%, when this situation occurs for one frame, it enters the synchronization mode.

[0064] As shown in FIG. 10, in the synchronization mode, the control and signal processing module performs interference prevention processing and also calculates the degree of interference in the current mode. When the degree of interference is greater than or equal to a certain threshold, it continues to maintain the synchronization mode. When the degree of interference is less than this threshold, it enters the polling mode.

[0065] In the control method in synchronous mode and the interference prevention processing method by the control and signal processing module, the information detected by the first detector and the second detector includes data such as distance, angle, reflectivity, and reflection intensity, but is not limited thereto. When the detection data of both the first detector and the second detector are within a predetermined deviation range or satisfy a predetermined relationship, it is considered that no interference is detected in this detection. Conversely, when the situation is reversed, it is considered that interference is detected. The magnitude of the deviation can be set according to specific embodiments. For example, the distance deviation is within ±10, the angle deviation is within 0.1°, the reflectivity deviation is within 10%, and the reflection intensity deviation is within 10%. Satisfying a predetermined relationship means that when making a comprehensive judgment, weights may be assigned to each detection data. When the control and signal processing module performs interference prevention processing, if it is considered that interference is detected in a certain synchronous detection, the detections of the corresponding first detector and second detector are considered invalid. The invalid detection data by the first detector and the second detector are directly discarded, and the valid detection data are output from the lidar. In the detection of one frame, the degree of interference is represented by the invalid detection ratio, that is, the interference intensity is equal to the ratio of the number of invalid detections within the detection time of one frame to the total number of points of the data of one frame. The threshold value of the interference intensity may be set to a certain value, for example, 10%. When the interference intensity is 10% or more, the synchronous mode is maintained. When the interference intensity is less than 10% and such a situation occurs continuously for K frames (K is a positive integer greater than or equal to 1 and can be set according to specific embodiments), the polling mode is entered.

[0066] As shown in FIG. 11, the first emission unit may also be referred to as a λ1 wavelength emission module, the second emission unit may also be referred to as a λ2 wavelength emission module, the first detector may also be referred to as a λ1 wavelength reception module, and the second detector may also be referred to as a λ2 wavelength reception module.

[0067] The TOF lidar system based on two wavelengths according to the present invention realizes the anti-interference ability of the lidar system and the processing of interference signals through cooperation with the polling switching of two wavelengths. The architecture of the lidar system includes a control and signal processing module, a λ1 wavelength emission module, a λ2 wavelength emission module, an emission optical system, a beam deflection device, a window sheet, a detection object, a reception optical system, a λ1 wavelength reception module, and a λ2 wavelength reception module. The window sheet is transparent to the λ1 wavelength laser and the λ2 wavelength laser, prevents light of other wavelengths from entering the interior of the lidar, and may further have designs for dust and water prevention, anti-fouling and washability, resistance to gravel impact, and defrosting and defogging. The control and signal processing module controls the laser emission of the emission module, the reception of the reception module, and the processing of echo signals. The λ1 wavelength emission module emits a laser pulse with a wavelength of λ1, and the λ2 wavelength emission module emits a laser pulse with a wavelength of λ2. The present invention adopts the configuration of two light sources and two detectors to realize the design of a two-wavelength lidar system, and through the polling switching and cooperation of the two light sources and two detectors, realizes real-time monitoring of interference and processing of interference signals. The system design and anti-interference method of the present invention can well cope with various interference sources, have a high anti-interference ability, and realize efficient detection of lidar.

[0068] The above are only preferred specific embodiments of the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent replacement or change made by any person skilled in the art within the technical scope described in the present invention based on the technical means and inventive concept of the present invention should be included in the protection scope of the present invention.

Claims

1. The laser radar is set to the interference prevention mode, and both the first detector and the second detector are set to the enabled state. Specifically, it includes the following first step to fifth step: First step: Start the laser radar system. Second step: Set the control and signal processing module to the interference prevention mode. Third step: The first case: When the pulse laser emission mode enters the λ mode in the default state １ the second detector enters the interference monitoring state, and then it is determined whether the second detector can monitor the interference. When the second detector fails to continuously monitor the interference for N frames, where N is a positive integer greater than or equal to 1, automatically switch to the λ ２ mode, and the first detector enters the interference monitoring state. When the second detector can monitor interference, automatically switch to the polling mode. Second case: When the pulse laser emission mode enters the λ ２ mode in the default state, the first detector enters the interference monitoring state, and then it is determined whether the first detector can monitor the interference. ２ ​ When the first detector fails to continuously monitor interference for N frames, where N is a positive integer greater than or equal to 1, automatically switch to the λ １ mode, and the second detector enters the interference monitoring state. When the first detector can monitor interference, automatically switch to the polling mode. Fourth step: In the polling mode, when the first detector performs signal detection, the second detector enters the interference monitoring state. When the second detector performs signal detection, the first detector enters the interference monitoring state, and the control and signal processing module performs interference prevention processing. Fifth step: First case: When the first detector and the second detector can continuously monitor interference simultaneously for M frames, where M is a positive integer greater than or equal to 1, and the interference signal is greater than the set threshold, automatically switch to the synchronization mode, and the control and signal processing module performs interference prevention processing and determines the interference degree. When it is determined that the interference degree is continuously less than the threshold for K frames, where K is a positive integer greater than or equal to 1, automatically switch to the polling mode. When it is determined that the interference degree is continuously greater than or equal to the threshold for K frames, where K is a positive integer greater than or equal to 1, automatically switch to the synchronization mode. Second case: When the first detector and the second detector cannot continuously monitor interference simultaneously for M frames, where M is a positive integer greater than or equal to 1, and the interference signal is less than or equal to the set threshold, automatically switch to the polling mode. A method for preventing interference in a two-wavelength based TOF laser radar system is characterized by this.

2. The steps for the control and signal processing module to perform interference information processing in the polling mode are as follows: Step (1): Calculate the interference intensities of the first detector and the second detector. Step (2): Compare the interference intensities of the first detector and the second detector. Step (3): Determine the primary data and the secondary data. Step (4): Output the primary data and the secondary data. The interference prevention method according to Claim 1 is characterized by this.

3. The steps for the control and signal processing module to perform interference information processing in the synchronization mode are as follows: Step 1: Obtain the detection information of the first detector and the second detector once, including but not limited to distance, angle, reflectivity, and reflection intensity. Step 2: Determine whether the detection data of the first detector and the second detector are within a predetermined deviation range or satisfy a predetermined relationship, and decide whether there is interference in the current detection. Step 3: When interference exists, the current detection is invalid; when interference does not exist, the current detection data is valid. Step 4: The interference prevention method according to claim 1, characterized in that the valid data of the first detector and the second detector are output simultaneously.

4. Including a control and signal processing module, a transmitting unit, a transmitting optical system, a beam deflecting device, a detection object, a receiving optical system, and a detector. The control and signal processing module is used to control the laser emission of the transmitting unit, the reception of the detector, and the processing of the echo signal. The emission unit is used to emit laser pulses, and the emission unit emits laser pulses with a wavelength of λ １ including a first emission unit for emitting laser pulses with a wavelength of λ ２ and a second emission unit for emitting laser pulses with a wavelength of λ The transmitting optical system is composed of the emission optical path of the first transmitting unit and the emission optical path of the second transmitting unit. The beam deflecting device is used for deflecting the laser beam to realize scanning within a predetermined field of view. The detection object is an object that can be detected within the predetermined field of view. The receiving optical system is composed of the receiving optical paths of the first detector and the second detector. The detector includes a first detector and a second detector. The first detector is used to detect a laser pulse signal with a wavelength of λ １ and the second detector is used to detect a laser pulse signal with a wavelength of λ ２ A two-wavelength-based TOF laser radar system for realizing the anti-interference method according to claim 1, characterized in that it is used to detect a laser pulse signal with a wavelength of λ

5. The two-wavelength based TOF laser radar system according to claim 4, characterized in that any one of a vertical cavity surface emitting laser, an edge emitting laser, and a fiber laser is adopted as the first transmitting unit, and any one of a vertical cavity surface emitting laser, an edge emitting laser, and a fiber laser is adopted as the second transmitting unit.

6. The two-wavelength based TOF laser radar system according to claim 5, characterized in that the same type of laser light source is adopted as the first transmitting unit and the second transmitting unit, or different types of laser light sources are adopted as the first transmitting unit and the second transmitting unit.

7. The two-wavelength based TOF laser radar system according to claim 5, characterized in that a single laser is adopted as both the first transmitting unit and the second transmitting unit, or a laser array is adopted as both the first transmitting unit and the second transmitting unit.

8. The emission optical system includes a first aperture, a second aperture, a first collimator lens, a second collimator lens, a first mirror, and a second mirror. The first aperture, the first collimator lens, and the second mirror constitute the emission optical path of the first emission unit. The second aperture, the second collimator lens, the first mirror, and the second mirror constitute the emission optical path of the second emission unit. The two-wavelength-based TOF laser radar system according to claim 4, wherein the laser beams emitted by the first emission unit and the second emission unit overlap the optical paths after passing through the second mirror, and the beam after the optical paths overlap is emitted to the beam deflection device.

9. The receiving optical system includes a third mirror, a fourth mirror, a first filter, a second filter, a first receiving lens group, a second receiving lens group, and a third aperture. The third mirror, the first filter, the first receiving lens group, and the third aperture constitute the receiving optical path of the first detector. The third mirror, the fourth mirror, the second filter, the second receiving lens group, and the third aperture constitute the receiving optical path of the second detector. After the laser pulse with a wavelength of λ １ and / or λ ２ reaches the first mirror, the laser pulse with one of the wavelengths of λ １ and / or λ ２ is totally reflected by the third mirror, then reflected by the fourth mirror, and then reaches the second detector via the second filter, the second receiving lens group, and the third aperture. The laser pulse with the other wavelength passes through the third mirror and reaches the first detector via the first filter, the first receiving lens group, and the third aperture. The two-wavelength-based TOF laser radar system according to claim 4, characterized in that.

10. The two-wavelength-based TOF laser radar system according to claim 9, wherein the first detector is located at the focal plane position of the first receiving lens group, and the second detector is located at the focal plane position of the second receiving lens group.

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