Adaptive segmented gain multi-wavelength laser ranging method and system

Abstract

The invention discloses an adaptive segmented gain multi-wavelength laser ranging method and system, and the method comprises the steps that a multi-wavelength laser emits laser pulses through an emission optical system under the control of a trigger signal, and the trigger mode comprises synchronous, equally-spaced and coded emission. Laser echoes are guided to the detector by the receiving system and converted by the segmented gain module to generate digital signals. And the control processing module processes the signal and calculates information including a distance measurement value and echo intensity. The weak signal detection capability is improved through self-adaptive segmented gain, suppression of strong signals by using a low-magnification gain circuit at a short distance and switching of a high-magnification gain circuit at a long distance, step gain is formed through gain partition, and a segmented area is adaptively adjusted according to an echo ranging value to avoid distortion. And the control processing module completes data transmission. The short-distance signal distortion and the long-distance signal leak detection are avoided, and the reliability and the detection capability of the system are improved.

Description

Technical Field

[0001] The present invention belongs to the field of laser ranging, and more specifically, relates to a multi-wavelength laser ranging method and system with adaptive segmented gain. Background Art

[0002] Pulsed laser ranging relies on measuring the time difference between the transmitted laser and the echo reflected by the target. Therefore, a one-to-one correspondence between the transmitted pulse and the echo is required. When the target is too far away or the laser repetition frequency is too fast, the next laser pulse may be triggered before the echo of the previous laser pulse is received by the detector, resulting in an incorrect pairing of the transmitted pulse and the echo, causing ranging ambiguity. In other words, there is a problem of difficulty in balancing the measurement frequency and measurement range. Unlike traditional microwave radar, due to the limitations of the laser and the requirements of the ranging range, it is difficult to distinguish different transmitted pulses through pulse modulation in hardware. Existing software processing and solution methods will have a certain solution error rate, which will generate noise in the point cloud.

[0003] Traditional laser ranging also faces the challenge of insufficient dynamic range. Within a single pulse cycle, the system must capture both strong echo signals from close-range, highly reflective targets and weak echo signals from distant, low-reflective targets. The energy span between these two signals can reach 120dB. This results in nonlinear distortion in traditional fixed-gain receiver links due to signal saturation at close range, while weak targets are missed at long ranges due to insufficient signal-to-noise ratio. A common approach uses a multi-channel receiving architecture (high-gain and low-gain channels in parallel) combined with adaptive gain control to achieve dynamic range expansion. However, multiple channels increase the complexity of the optical system, requiring more detectors, signal conditioning circuits, and high-speed ADC channels. Adaptive gain control requires feedback based on the size of the received signal to adjust the gain. In complex and changing environments, the dynamic response speed of this feedback mechanism is difficult to meet requirements.

[0004] At the same time, a single laser wavelength has limitations in target detection. For example, the infrared band has strong propagation capabilities in the air but cannot penetrate the water surface medium. The point cloud measured by the airborne lidar will form holes on the water surface. A single wavelength can only obtain the reflectivity of the target in this band, and it is necessary to use an optical camera or a hyperspectral camera to obtain more target spectral information.

[0005] Based on the above defects and shortcomings, this field urgently needs a multi-wavelength laser ranging method with adaptive segmented gain to effectively improve the measurement frequency and dynamic range of large-scale laser ranging, add multi-spectral information, and expand application scenarios such as surface and underwater. Summary of the Invention

[0006] This invention aims to address the challenges of traditional laser ranging, including the difficulty in balancing measurement frequency and range, insufficient dynamic range, and the limitations of single-wavelength detection. By proposing a multi-wavelength laser ranging method with adaptive segmented gain, this method effectively increases the measurement frequency and dynamic range of large-scale laser ranging. This method utilizes multiple wavelengths to acquire multispectral information about a target, expanding its application to surface and underwater scenarios. It also reduces point cloud noise, avoids near-range signal distortion and long-range signal underdetection, and improves system reliability and detection capabilities.

[0007] In response to the above-mentioned defects or improvement needs of the prior art, as a first aspect of the present invention, a multi-wavelength laser ranging method with adaptive segmented gain is provided, comprising:

[0008] S1. A multi-wavelength laser emits laser pulses through a transmitting optical system under the control of a trigger signal. Triggering modes include synchronous emission, equally spaced emission, and coded emission.

[0009] S2. The laser pulse is reflected by the target to form an echo, and the receiving system makes the echo of each wavelength be received by the detector separately;

[0010] S3. The echoes of different wavelengths are converted into electrical signals by the segmented gain module, and then converted into digital signals through high-speed analog-to-digital conversion. The control processing module processes the digital signals and calculates information including ranging values ​​and echo strength according to design requirements.

[0011] S4. Adaptive segmented gain settings are used to address the simultaneous detection of weak signals at long distances and strong signals at close ranges. Within the close range, a low-amplification gain circuit is used to suppress the echo strength of close-range signals. Outside the close range, a high-amplification gain circuit is switched to improve the detection of weak signals at long distances. Furthermore, the number of gain segments is increased to form a stepped gain, depending on the measurement range. Furthermore, segmented regions are adaptively adjusted based on echo ranging values ​​and other factors to avoid signal distortion.

[0012] S5. The control processing module communicates and transmits the processed data to the host computer.

[0013] Furthermore, the scenarios for synchronous transmission, equally spaced transmission, and coded transmission distribution adaptation in S1 are as follows:

[0014] Synchronous emission mode, used for simultaneous detection of different media;

[0015] The purpose of the equal-interval emission method is to ensure the uniformity of the laser trigger interval, thereby ensuring the uniformity of the measured point cloud and facilitating the subsequent point cloud processing;

[0016] The coded transmission method can further expand the unambiguous range of ranging and the ability to resist interference from other lidars. By encoding the trigger intervals of lasers of different wavelengths and judging the relative position relationship between the ranging values ​​of echoes received at different wavelengths, it can be used to determine which laser triggering the echo matches, breaking through the ambiguity range limit of a single pulse, or judging whether the echo belongs to the laser pulse echo emitted by this system, avoiding interference from other laser measurement systems.

[0017] Furthermore, the receiving system in S2 uses spectroscopic and narrowband filtering to allow echoes of different wavelengths to be received separately by the detector, thus preventing laser pulses of different wavelengths from interfering with each other.

[0018] Furthermore, the method for setting the gain partition in S4 is:

[0019] The system's ranging range is designed to be d min ~d max , the total number of gain levels is L, then the distance d between the junction of the i-th gain level and the i+1-th gain level is g-i Set as:

[0020]

[0021] Where, d max and d min They are the maximum and minimum values ​​of the junction distance, corresponding to the upper and lower limits of the junction adjustment range.

[0022] Furthermore, in S4, the segmented area is adaptively adjusted based on the echo ranging value and other factors to avoid signal distortion. The specific method is as follows:

[0023] Assume that the echo ranging value obtained by the last laser trigger is d measured ;

[0024] Assume that the time interval between the echo and the boundary position is Δt e-b , which is obtained by converting the echo ranging value and the boundary position distance through the speed of light c, that is:

[0025]

[0026] Let the adjustment threshold be T adj , the lower limit of the boundary adjustment range is T org , the upper limit of the boundary adjustment range is T org +ΔT, the distance between the adjusted i-th gain and i+1-th gain is

[0027] Judgment |Δt e-b |With T adj The size relationship, and Δt e-bThe relative position to the boundary adjustment range;

[0028] When |Δt e-b | <T adj And Δt e-b When approaching the lower limit of the range, Adjust the junction to the distance corresponding to the upper limit of the range:

[0029]

[0030] When |Δt e-b | <T adj And Δt e-b When approaching the upper limit of the range, Adjust the junction to the distance corresponding to the upper limit of the range:

[0031]

[0032] When |Δt e-b |≥T adj , the junction position remains unchanged, that is:

[0033]

[0034] When the junction position is adjusted to the upper or lower limit of the allowable adjustment range, the junction position can be readjusted to the lower limit, upper limit, initial position or any position without echo. reset :

[0035] like or but

[0036] Furthermore, the medium-interval emission mode of the multi-wavelength laser in S1 is specifically:

[0037] For M wavelength laser transceiver modules, after setting the trigger frequency of a single wavelength laser to PRR, the trigger interval between lasers of different wavelengths is set to

[0038] According to the calculated trigger interval, lasers of different wavelengths are triggered to emit laser pulses in sequence; that is, after the first wavelength laser is emitted, the second wavelength laser is triggered to emit after a specific time interval, and so on, until all M wavelength lasers have completed one emission; then a new round of emission is started again from the first wavelength laser, and this cycle is repeated to ensure uniform laser triggering intervals;

[0039] The emitted laser pulse is reflected by the target to form an echo, which is collected by the receiving optical system. After being split by the spectroscopic system, the echoes of different wavelengths are received by the corresponding detectors and converted into electrical signals. Then, digital signals are generated through high-speed analog-to-digital conversion. The control processing module processes these digital signals and calculates information including the corresponding distance measurement value and the echo intensity of different wavelengths.

[0040] Since laser pulses of different wavelengths are not emitted simultaneously in the equally spaced emission mode, and echoes of different wavelengths do not measure the same target, spectral registration of the same target is achieved through upsampling and interpolation of point clouds of different wavelengths.

[0041] Furthermore, the method of upsampling and interpolating point clouds of different wavelengths to achieve the same target spectral registration is specifically as follows:

[0042] The upsampling interpolation and spectral registration of point clouds with different wavelengths only need to consider the scan line direction;

[0043] Assume that the echo intensity of the jth laser trigger with wavelength λ1 is Then the echo intensity sequence Perform M-fold interpolation to obtain the interpolated echo intensity sequence The calculation formula is as follows:

[0044]

[0045] In the formula, k represents the interpolated sequence and the index values ​​of the relevant intermediate interpolation sequences; The sequence is Insert M-1 0s between each pair of sequence values, so The length of the sequence becomes The sequence is M times; for the echo intensity sequence before and after interpolation, there are:

[0046]

[0047] Therefore, for an echo intensity sequence of M wavelengths emitted at equal intervals, the target spectrum information obtained by the j-th laser triggering of the m-th wavelength is:

[0048]

[0049] In the formula, each parameter represents λ1 represents I jIn the echo intensity sequence of M wavelengths emitted at equal intervals, when the laser is triggered for the jth time, the vector composed of the interpolated echo intensity values ​​corresponding to each wavelength represents the target spectral information obtained for this trigger; M is the interpolation factor, which indicates the multiple by which the data density of the original echo intensity sequence is increased when interpolating; m is used to identify the mth wavelength in a multi-wavelength system, where m = 1, 2, …, M.

[0050] Furthermore, the specific method of adaptive segmented gain in S4 is as follows: a resistor with multiple resistance values ​​is set in parallel in the transimpedance amplifier circuit at the rear end of the detector, and each parallel resistor is connected in series with a switch device to control the connection and disconnection of the resistor in the transimpedance amplifier circuit; the switch device is controlled by the control and processing module through high and low level control.

[0051] The equivalent transimpedance of the transimpedance amplifier circuit is:

[0052]

[0053] Where g(i)=0,1 is the state of the i-th switch, R i is the resistance of the i-th resistor.

[0054] As a second aspect of the present invention, there is provided a multi-wavelength laser ranging system with adaptive segmented gain, characterized in that it includes:

[0055] Laser emission unit, used for emitting laser pulses through the emission optical system under the control of trigger signals of multi-wavelength lasers; triggering modes include synchronous emission, equal interval emission and coded emission;

[0056] The echo receiving unit is used for the laser pulse to be reflected by the target to form an echo, and the receiving system allows the echo of each wavelength to be received by the detector respectively;

[0057] The signal conversion and processing unit is used to convert echoes of different wavelengths into electrical signals through the segmented gain module, and then generate digital signals through high-speed analog-to-digital conversion. The control processing module processes the digital signals and calculates information including ranging value and echo intensity according to design requirements;

[0058] The gain adjustment unit is used to solve the problem of simultaneous detection of weak signals at long distances and strong signals at close ranges through adaptive segmented gain settings: within the close range, a low-amplification gain circuit is used to suppress the echo intensity of close-range signals; outside the close range, a high-amplification gain circuit is switched to improve the detection capability of weak signals at long distances; at the same time, the number of gain partitions is further increased according to the needs of the measurement range to form a stepped gain; at the same time, the segmented areas are adaptively adjusted according to the echo ranging value to avoid signal distortion;

[0059] The control processing unit is used to control the processing module to communicate and transmit the processed data to the host computer.

[0060] As a third aspect of the present invention, a computer-readable storage medium is provided, on which a computer program is stored, and the computer program is used by a processor to execute any step of the multi-wavelength laser ranging method with adaptive segmented gain.

[0061] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0062] 1. The adaptive segmented gain multi-wavelength laser ranging method of the present invention sets the trigger frequency of a single-wavelength laser, determines the trigger interval between lasers of different wavelengths, and sequentially triggers the emission of laser pulses according to this interval. The echo of the laser after reflection from the target is collected, split, converted, and processed by the system. Given that laser pulses of different wavelengths are not emitted simultaneously, spectral alignment is achieved by upsampling and interpolation of point clouds of different wavelengths. This method can simultaneously acquire multi-wavelength information, increase data dimensionality, ensure uniform and stable laser emission, improve the accuracy of multispectral information acquisition, and achieve comprehensive and accurate perception of target characteristics.

[0063] 2. The multi-wavelength laser ranging method with adaptive segmented gain of the present invention is achieved by building a specific transimpedance amplifier circuit on the hardware, connecting multiple resistors of different resistance values ​​in parallel, and connecting switching devices in series, which are controlled by the control module through high and low voltage levels. At the algorithm level, the total number of gain gears and the junction of each gear are calculated according to the system ranging range, and the segmented area is adaptively adjusted according to the time relationship between the echo and the junction position. The hardware and algorithm cooperate with each other so that the segmented gain can be flexibly adjusted according to the actual ranging requirements, ensuring that the circuit can reasonably amplify the signal in different distance segments, and providing an efficient and stable gain adjustment mechanism for the laser ranging system. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 This is a flow chart of a multi-wavelength laser ranging method with adaptive segmented gain according to an embodiment of the present invention;

[0065] Figure 2 A system module diagram of a multi-wavelength laser ranging method using an adaptive segmented gain according to an embodiment of the present invention;

[0066] Figure 3 Schematic diagram of the circuit segment gain principle of an embodiment of the present invention;

[0067] Figure 4 This is an example diagram of an equally spaced transmission method according to an embodiment of the present invention;

[0068] Figure 5 This is an example diagram of the circuit segment gain according to an embodiment of the present invention;

[0069] Figure 6 2 is a diagram of system units according to an embodiment of the present invention. DETAILED DESCRIPTION

[0070] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0071] Example 1

[0072] Please refer to Figure 1 This embodiment 1 provides a multi-wavelength laser ranging method with adaptive segmented gain, including:

[0073] S1. A multi-wavelength laser emits laser pulses through a transmitting optical system under the control of a trigger signal. Triggering modes include synchronous emission, equally spaced emission, and coded emission.

[0074] S2. The laser pulse is reflected by the target to form an echo, and the receiving system makes the echo of each wavelength be received by the detector separately;

[0075] S3. The echoes of different wavelengths are converted into electrical signals by the segmented gain module, and then converted into digital signals through high-speed analog-to-digital conversion. The control processing module processes the digital signals and calculates information including ranging values ​​and echo strength according to design requirements.

[0076] S4. Adaptive segmented gain settings are used to address the simultaneous detection of weak signals at long distances and strong signals at close ranges. Within the close range, a low-amplification gain circuit is used to suppress the echo strength of close-range signals. Outside the close range, a high-amplification gain circuit is switched to improve the detection of weak signals at long distances. Furthermore, the number of gain segments is increased to form a stepped gain, depending on the measurement range. Furthermore, segmented regions are adaptively adjusted based on echo ranging values ​​and other factors to avoid signal distortion.

[0077] S5. The control processing module communicates and transmits the processed data to the host computer.

[0078] This embodiment 1 specifically describes the above method steps:

[0079] Please refer to Figure 2This embodiment 1 includes a multi-wavelength laser transceiver module, a segmented gain module, and a control and processing module. Under the control of a trigger signal, the multi-wavelength laser emits laser pulses through a transmitting optical system. The laser pulses are reflected by the target, forming echoes that are received by a receiving optical system. The echoes of different wavelengths are split by the optical splitting system and converted into electrical signals by the segmented gain module. High-speed analog-to-digital conversion then generates digital signals that are processed by the control and processing module to obtain information such as the corresponding distance measurement value and the echo intensity of different wavelengths. Finally, the control and processing module communicates with the host computer and transmits data.

[0080] Multi-wavelength laser transceiver module. By using lasers of different wavelengths to emit light alternately, the receiving system uses spectroscopic and narrowband filtering to allow echoes of different wavelengths to be received separately by the detector, thus avoiding mutual interference between laser pulses of different wavelengths.

[0081] There are three main ways to trigger lasers of different wavelengths: synchronous emission, equally spaced emission, and coded emission, which correspond to different application scenarios and purposes.

[0082] The synchronous emission mode is mainly used for the simultaneous detection of different media, such as airborne blue-green bathymetric lidar for simultaneous surface and underwater detection, or for scenarios with high requirements for spectral and temporal synchronization, such as high-speed scanning or high-speed movement of the carrier and the target is far away, to avoid asynchronous emission causing different laser pulses to hit different targets and cause measurement inaccuracy.

[0083] The purpose of the equally spaced emission method is to ensure uniform laser trigger intervals, thereby ensuring uniformity in the measured point cloud and facilitating subsequent point cloud processing. Within the same ranging ambiguity range, the number of lasers of different wavelengths determines the multiple of the maximum measurement frequency of this invention compared to traditional single-wavelength laser ranging.

[0084] The coded transmission method can further expand the unambiguous range of ranging and resist interference from other laser radars. By encoding the trigger intervals of lasers of different wavelengths and judging the relative position relationship between the ranging values ​​of the echoes received at different wavelengths, it can determine which laser triggering the echo matches. This can break through the ambiguity range of single-pulse ranging or determine whether the echo belongs to the laser pulse echo emitted by the system, thus avoiding interference from other laser measurement systems. In terms of increasing measurement frequency, compared with the equally spaced transmission method, the coded transmission method requires fewer lasers of different wavelengths, but it does require an additional encoding and decoding processing module.

[0085] Furthermore, each wavelength echo carries information about the target's reflectivity at that wavelength. By measuring different wavelengths, we can obtain multispectral information about the target and generate a colored point cloud. Because laser pulses of different wavelengths are not emitted simultaneously in the equally spaced and coded emission methods, echoes of different wavelengths do not represent the same target. Spectral registration of the same target is achieved through upsampling and interpolation of point clouds at different wavelengths.

[0086] The adaptive segmented gain module solves the problem of simultaneously detecting weak signals at long range and strong signals at close range. Within the close range, a low-amplification gain circuit is used to suppress the echo strength of short-range signals. Outside the close range, a high-amplification gain circuit is switched to improve the detection of weak signals at long range. Since the adaptive gain control eliminates the need for feedback on echo signal strength, issues with dynamic response speed and complex control algorithms are avoided, thereby improving system reliability. The number of gain segments can be further increased to form a stepped gain structure, depending on the measurement range.

[0087] In order to ensure a reasonable gain range and signal quality, if the system's ranging range is designed to be d min ~d max , the total number of gain levels is L, then the boundary between the i-th level gain and the i+1-th level gain is set to:

[0088]

[0089] Furthermore, in order to avoid distortion of the echo signal caused by the gain switching between adjacent areas, it is necessary to perform adaptive adjustment on the segmented areas within a certain range.

[0090] Please refer to Figure 3 Based on the echo ranging value obtained from the last laser trigger and the intersection position of the segmented gain range, the time interval between the echo and the intersection position is calculated. If the absolute value of the time interval is less than the threshold, the intersection position on the time axis is increased or decreased accordingly, so that the intersection position is further away from the valid echo area. When the intersection position is adjusted to the upper (lower) limit of the allowable adjustment range, the intersection position is readjusted to the lower (upper) limit, the initial position, or any position without echo.

[0091] In a preferred embodiment, the segmented area is adaptively adjusted based on the echo ranging value to avoid signal distortion. The specific method is as follows:

[0092] Assume that the echo ranging value obtained by the last laser trigger is d measured ;

[0093] Assume that the time interval between the echo and the boundary position is Δt e-b , which is obtained by converting the echo ranging value and the boundary position distance through the speed of light c, that is:

[0094]

[0095] Let the adjustment threshold be T adj , the lower limit of the boundary adjustment range is T org , the upper limit of the boundary adjustment range is T org +ΔT, the distance between the adjusted i-th gain and i+1-th gain is

[0096] Judgment |Δt e-b |With T adj The size relationship, and Δt e-b The relative position to the boundary adjustment range;

[0097] When |Δt e-b | <T adj And Δt e-b When approaching the lower limit of the range, Adjust the junction to the distance corresponding to the upper limit of the range:

[0098]

[0099] When |Δt e-b | <T adj And Δt e-b When approaching the upper limit of the range, Adjust the junction to the distance corresponding to the upper limit of the range:

[0100]

[0101] When |Δt e-b |≥T adj , the junction position remains unchanged, that is:

[0102]

[0103] When the junction position is adjusted to the upper or lower limit of the allowable adjustment range, the junction position can be readjusted to the lower limit, upper limit, initial position or any position without echo. reset :

[0104] like or but

[0105] Please refer to Figure 4 The specific embodiment of the multi-wavelength equal interval transmission mode in the multi-wavelength laser transceiver module is shown in the figure below: For the M-wavelength laser transceiver module, after setting the trigger frequency of the single-wavelength laser to PRR, the trigger interval between different wavelength lasers is set to This increases the laser measurement frequency by M times.

[0106] Since the airborne laser radar will try to set the rotation speed, point frequency, speed and other parameters to ensure the uniformity of the point density directly below during the scanning process, the upsampling interpolation and spectral registration of point clouds with different wavelengths only need to consider the scanning line direction. Assume that the echo intensity of the jth laser trigger with wavelength λ1 is Then the echo intensity sequence Perform M-fold interpolation to obtain the interpolated echo intensity sequence The calculation formula is as follows:

[0107]

[0108] In the formula, k represents the interpolated sequence and the index values ​​of the relevant intermediate interpolation sequences; The sequence is Insert M-1 0s between each pair of sequence values, so The length of the sequence becomes The sequence is M times; for the echo intensity sequence before and after interpolation, there are:

[0109]

[0110] Therefore, for an echo intensity sequence of M wavelengths emitted at equal intervals, the target spectrum information obtained by the j-th laser triggering of the m-th wavelength is:

[0111]

[0112] In the formula, each parameter represents λ1 represents I j In the echo intensity sequence of M wavelengths emitted at equal intervals, when the laser is triggered for the jth time, the vector composed of the interpolated echo intensity values ​​corresponding to each wavelength represents the target spectral information obtained for this trigger; M is the interpolation factor, which indicates the multiple by which the data density of the original echo intensity sequence is increased when interpolating; m is used to identify the mth wavelength in a multi-wavelength system, where m = 1, 2, …, M.

[0113] The above is only one embodiment of upsampling interpolation and spectral registration, and other interpolation algorithms may also be used.

[0114] Please refer to Figure 5 In a preferred embodiment, the specific method for achieving circuit segmented gain is to set resistors of multiple resistance values ​​in parallel in the transimpedance amplifier circuit at the back end of the detector. Each parallel resistor is connected in series with a switch device to control the switching of the resistor in the transimpedance amplifier circuit. The switch device is controlled by the control and processing module through high and low voltage levels.

[0115] The equivalent transimpedance of the transimpedance amplifier circuit is:

[0116]

[0117] Where g(i)=0,1 is the state of the i-th switch, R i is the resistance of the i-th resistor. Through reasonable resistance design, the maximum value that can be obtained is 2 N -1 different resistance level.

[0118] For a simple example, two resistors, 1k ohm and 10k ohm, are designed for gear switching. The 10k ohm switch is in a normally closed state, and the 1k ohm resistor switch is switched according to the high and low level signals sent by the control and processing module to avoid the competition and risk of simultaneous open circuits when the switch circuits of the two resistors are switched at the same time. In this example, the segmented gain is divided into two levels, namely the 10k level for a single 10k ohm resistor and the 0.9k level for a 10k ohm resistor in parallel with a 1k ohm resistor. If the system's ranging range is designed to be 5m to 1500m, the intersection of the two gain levels is set to:

[0119]

[0120] The junction of the two gain levels is based on the time difference Δt between the center of the previous echo and the junction. e-b Decide whether to adjust. The adjustment range is limited to a certain area at the initial intersection. A specific adjustment strategy is given below:

[0121] Directly set the upper and lower limits of the boundary adjustment range [T org ,T org +200ns], when |Δt e-b |Less than the adjustment threshold T adj When it is close to the lower limit of the range, adjust the junction to the upper limit of the range, and vice versa. adj The minimum value is determined by the echo pulse width, otherwise the junction will be located within the echo waveform. For example, the threshold T adj Set it to 3 times the echo pulse width, that is, when the echo pulse width is 10ns, adjust the threshold T adj Set to 30ns.

[0122] For multiple gain levels or other complex situations, more sophisticated adjustment strategies can be designed.

[0123] Example 2

[0124] Please refer to Figure 4 This embodiment 2 provides a multi-wavelength laser ranging system with adaptive segmented gain, including:

[0125] Laser emission unit, used for emitting laser pulses through the emission optical system under the control of trigger signals of multi-wavelength lasers; triggering modes include synchronous emission, equal interval emission and coded emission;

[0126] The echo receiving unit is used for the laser pulse to be reflected by the target to form an echo, and the receiving system allows the echo of each wavelength to be received by the detector respectively;

[0127] The signal conversion and processing unit is used to convert echoes of different wavelengths into electrical signals through the segmented gain module, and then generate digital signals through high-speed analog-to-digital conversion. The control processing module processes the digital signals and calculates information including ranging value and echo intensity according to design requirements;

[0128] The gain adjustment unit is used to solve the problem of simultaneous detection of weak signals at long distances and strong signals at close ranges through adaptive segmented gain settings: within the close range, a low-amplification gain circuit is used to suppress the echo intensity of close-range signals; outside the close range, a high-amplification gain circuit is switched to improve the detection capability of weak signals at long distances; at the same time, the number of gain partitions is further increased according to the needs of the measurement range to form a stepped gain; at the same time, the segmented areas are adaptively adjusted according to the echo ranging value to avoid signal distortion;

[0129] The control processing unit is used to control the processing module to communicate and transmit the processed data to the host computer.

[0130] Example 3

[0131] This embodiment 3 also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it can implement any step of a multi-wavelength laser ranging method with adaptive segmented gain.

[0132] The computer-readable storage medium may include: a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, etc., which can store program codes.

[0133] For an introduction to the computer-readable storage medium provided in this application, please refer to the above method embodiment, and this application will not go into details here.

[0134] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-wavelength laser ranging method with adaptive segmented gain, characterized in that: include: S1. A multi-wavelength laser emits laser pulses through a transmitting optical system under the control of a trigger signal. Triggering modes include synchronous emission, equally spaced emission, and coded emission. S2. The laser pulse is reflected by the target to form an echo, and the receiving system makes the echo of each wavelength be received by the detector separately; S3. The echoes of different wavelengths are converted into electrical signals by the segmented gain module, and then converted into digital signals through high-speed analog-to-digital conversion. The control processing module processes the digital signals and calculates information including ranging values ​​and echo strength according to design requirements. S4. Adaptive segmented gain settings are used to address the simultaneous detection of weak signals at long distances and strong signals at close ranges. Within the close range, a low-amplification gain circuit is used to suppress the echo strength of close-range signals. Outside the close range, a high-amplification gain circuit is switched to improve the detection of weak signals at long distances. Furthermore, the number of gain segments is increased to form a stepped gain, depending on the measurement range. Furthermore, segmented regions are adaptively adjusted based on echo ranging values ​​and other factors to avoid signal distortion. S5. The control processing module communicates and transmits the processed data to the host computer.

2. The multi-wavelength laser ranging method with adaptive segmented gain according to claim 1, characterized in that: The scenarios in which synchronous transmission, equally spaced transmission and coded transmission distribution adaptation in S1 are: Synchronous emission mode, used for simultaneous detection of different media; The purpose of the equal-interval emission method is to ensure the uniformity of the laser trigger interval, thereby ensuring the uniformity of the measured point cloud and facilitating the subsequent point cloud processing; The coded transmission method can further expand the unambiguous range of ranging and the ability to resist interference from other lidars. By encoding the trigger intervals of lasers of different wavelengths and judging the relative position relationship between the ranging values ​​of echoes received at different wavelengths, it can be used to determine which laser triggering the echo matches, breaking through the ambiguity range limit of a single pulse, or judging whether the echo belongs to the laser pulse echo emitted by this system, avoiding interference from other laser measurement systems.

3. The multi-wavelength laser ranging method with adaptive segmented gain according to claim 1, characterized in that: The receiving system in S2 adopts the method of light splitting and narrow-band filtering to allow echoes of different wavelengths to be received by the detector respectively, thereby avoiding mutual interference between laser pulses of different wavelengths.

4. The multi-wavelength laser ranging method with adaptive segmented gain according to claim 1, characterized in that: The method for setting the gain partition in S4 is: The system's ranging range is designed to be d min ~d max , the total number of gain levels is L, then the distance d between the junction of the i-th gain level and the i+1-th gain level is g-i Set as: Where, d max and d min They are the maximum and minimum values ​​of the junction distance, corresponding to the upper and lower limits of the junction adjustment range.

5. The multi-wavelength laser ranging method with adaptive segmented gain according to claim 1, characterized in that: In the above S4, the segmented area is adaptively adjusted according to the echo ranging value and other factors to avoid signal distortion. The specific method is as follows: Assume that the echo ranging value obtained by the last laser trigger is d measured ; Assume that the time interval between the echo and the boundary position is Δt e-b , which is obtained by converting the echo ranging value and the boundary position distance through the speed of light c, that is: Let the adjustment threshold be T adj , the lower limit of the boundary adjustment range is T org , the upper limit of the boundary adjustment range is T org +ΔT, the distance between the adjusted i-th gain and i+1-th gain is Judgment |Δt e-b |With T adj The size relationship, and Δt e-b The relative position to the boundary adjustment range; When |Δt e-b | <T adj And Δt e-b When approaching the lower limit of the range, Adjust the junction to the distance corresponding to the upper limit of the range: When |Δt e-b | <T adj And Δt e-b When approaching the upper limit of the range, Adjust the junction to the distance corresponding to the upper limit of the range: When |Δt e-b |≥T adj , the junction position remains unchanged, that is: When the junction position is adjusted to the upper or lower limit of the allowable adjustment range, the junction position can be readjusted to the lower limit, upper limit, initial position or any position without echo. reset : like or but 6. The multi-wavelength laser ranging method with adaptive segmented gain according to claim 1, characterized in that: The specific mode of medium interval emission of the multi-wavelength laser in S1 is: For M wavelength laser transceiver modules, after setting the trigger frequency of a single wavelength laser to PRR, the trigger interval between lasers of different wavelengths is set to According to the calculated trigger interval, lasers of different wavelengths are triggered to emit laser pulses in sequence; that is, after the first wavelength laser is emitted, the second wavelength laser is triggered to emit after a specific time interval, and so on, until all M wavelength lasers have completed one emission; then a new round of emission is started again from the first wavelength laser, and this cycle is repeated to ensure uniform laser triggering intervals; The emitted laser pulse is reflected by the target to form an echo, which is collected by the receiving optical system. After being split by the spectroscopic system, the echoes of different wavelengths are received by the corresponding detectors and converted into electrical signals. Then, digital signals are generated through high-speed analog-to-digital conversion. The control processing module processes these digital signals and calculates information including the corresponding distance measurement value and the echo intensity of different wavelengths. Since laser pulses of different wavelengths are not emitted simultaneously in the equally spaced emission mode, and echoes of different wavelengths do not measure the same target, spectral registration of the same target is achieved through upsampling and interpolation of point clouds of different wavelengths.

7. The multi-wavelength laser ranging method with adaptive segmented gain according to claim 6, characterized in that: The method of upsampling and interpolating point clouds of different wavelengths to achieve the same target spectral registration is specifically as follows: The upsampling interpolation and spectral registration of point clouds with different wavelengths only need to consider the scan line direction; Assume that the echo intensity of the jth laser trigger with wavelength λ1 is Then the echo intensity sequence Perform M-fold interpolation to obtain the interpolated echo intensity sequence The calculation formula is as follows: In the formula, k represents the interpolated sequence and the index values ​​of the relevant intermediate interpolation sequences; The sequence is Insert M-1 0s between each pair of sequence values, so The length of the sequence becomes The sequence is M times; for the echo intensity sequence before and after interpolation, there are: Therefore, for an echo intensity sequence of M wavelengths emitted at equal intervals, the target spectrum information obtained by the j-th laser triggering of the m-th wavelength is: In the formula, each parameter represents λ1 represents I j In the echo intensity sequence of M wavelengths emitted at equal intervals, when the laser is triggered for the jth time, the vector composed of the interpolated echo intensity values ​​corresponding to each wavelength represents the target spectral information obtained for this trigger; M is the interpolation factor, which indicates the multiple by which the data density of the original echo intensity sequence is increased when interpolating; m is used to identify the mth wavelength in a multi-wavelength system, where m = 1, 2, …, M.

8. The multi-wavelength laser ranging method with adaptive segmented gain according to claim 1, characterized in that: The specific method of adaptive segment gain in S4 is: In the transimpedance amplifier circuit at the rear end of the detector, resistors with multiple resistance values ​​are connected in parallel. Each parallel resistor is connected in series with a switch device to control the connection and disconnection of the resistor in the transimpedance amplifier circuit. The switch device is controlled by the control and processing module through high and low level control. The equivalent transimpedance of the transimpedance amplifier circuit is: Where g(i)=0,1 is the state of the i-th switch, R i is the resistance of the i-th resistor.

9. A multi-wavelength laser ranging system with adaptive segmented gain, characterized in that: include: The laser emission unit is used for emitting laser pulses through the emission optical system under the control of the trigger signal of the multi-wavelength laser; Triggering modes include synchronous transmission, equal interval transmission and coded transmission; The echo receiving unit is used for the laser pulse to be reflected by the target to form an echo, and the receiving system allows the echo of each wavelength to be received by the detector respectively; The signal conversion and processing unit is used to convert echoes of different wavelengths into electrical signals through the segmented gain module, and then generate digital signals through high-speed analog-to-digital conversion. The control processing module processes the digital signals and calculates information including ranging value and echo intensity according to design requirements; The gain adjustment unit is used to solve the problem of simultaneous detection of weak signals at long distances and strong signals at close ranges through adaptive segmented gain settings: within the close range, a low-amplification gain circuit is used to suppress the echo intensity of close-range signals; outside the close range, a high-amplification gain circuit is switched to improve the detection capability of weak signals at long distances; at the same time, the number of gain partitions is further increased according to the needs of the measurement range to form a stepped gain; at the same time, the segmented areas are adaptively adjusted according to the echo ranging value to avoid signal distortion; The control processing unit is used to control the processing module to communicate and transmit the processed data to the host computer.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: The computer program is executed by a processor to execute the multi-wavelength laser ranging method with adaptive segmented gain according to any one of claims 1 to 8.

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