A method and system for automatic alignment of laser optical axis with detector

Abstract

This invention discloses a method and system for automatic alignment of a laser optical axis with a detector. The method includes: controlling a three-axis displacement stage to scan the echo signal coordinates and automatically adjusting the laser emission power; determining the spatial range of the echo signal through scanning, and deploying initial particles on the axial plane with a small spot size and high light intensity; after setting particle swarm parameters, using a dynamic PSO particle swarm optimization algorithm to iteratively update the inertia weight and particle number, calculate particle positions and obtain light intensity values, and determine the optimal relative position at close range; simultaneously, calculating the image distance difference between near and far targets, and controlling the Z-axis of the three-axis displacement stage to complete axial compensation; calculating the echo offset angle and radial displacement based on the motor speed, target distance, and light speed, and combining this with the detector target radius to control the X-axis to complete radial compensation, achieving precise alignment. This significantly improves alignment efficiency and accuracy, overcoming the shortcomings of traditional methods such as slow positioning and low accuracy.

Description

Technical Field

[0001] This invention belongs to the field of lidar detection technology, and more specifically, relates to a method and system for automatically aligning the laser optical axis with the detector. Background Technology

[0002] In the field of lidar detection technology, lidar, as an active three-dimensional spatial information acquisition technology, has been widely used in surveying, remote sensing, autonomous driving, and other fields. To improve its detection range, it is necessary to utilize the physical optical focal characteristics of the echo receiving optical system to accurately position the detector at the point of maximum echo signal intensity, achieving coincidence with the optical focal point, thereby optimizing the system's detection performance.

[0003] Currently, the adjustment of the laser optical axis and detector position mainly relies on manual experience. Existing methods typically use fixtures to fix the optical structure, manually adjust the detector position, and then use an oscilloscope to find the point with the strongest echo amplitude before fixing it. This method has significant drawbacks: First, the adjustment process is highly dependent on the operator's experience, making it difficult to guarantee adjustment accuracy and failing to meet the requirements of high-precision detection; second, the optical axis adjustment process is complex, requiring multiple steps such as indoor coarse adjustment, outdoor fine adjustment, and dynamic target offset compensation, resulting in long assembly cycles and low efficiency; third, due to the lack of a unified adjustment strategy, existing methods are difficult to adapt to different optical structures, have poor universality, and limit their application in diverse products.

[0004] Furthermore, existing technologies have shortcomings in laser power control, failing to automatically adjust the emission power based on factors such as target distance and laser model. This leads to issues like echo signal saturation or being submerged in noise, affecting focus position determination. In terms of spatial search, the lack of efficient algorithms makes it difficult to quickly locate the detector's optimal position. Simultaneously, existing methods cannot achieve dynamic and precise compensation for target misses during long-distance ranging while the motor is rotating, limiting the long-range detection performance of lidar under high-speed scanning.

[0005] Therefore, there is an urgent need for a method and device for automatic alignment of the laser optical axis and the detector that can overcome the above-mentioned defects, so as to achieve rapid and stable automatic alignment, reduce manual intervention, improve assembly efficiency, and have good versatility and adaptability to meet the needs of lidar technology development. Summary of the Invention

[0006] This invention proposes a method and device for automatic alignment of laser optical axis and detector, which can quickly and stably achieve automatic alignment between the optical axis and detector of lidar optical system in a single scenario, with low degree of manual intervention and effectively improve system assembly efficiency.

[0007] To address the aforementioned deficiencies or improvement needs of the existing technology, as a first aspect of the present invention, a method for automatically aligning a laser optical axis with a detector is provided, comprising:

[0008] S1. The echo signal coordinates are obtained by scanning through a three-axis displacement stage. The laser ranging module’s transmission power is automatically adjusted based on the feedback to confirm the final transmission power.

[0009] S2. The spatial range of the echo signal is determined by scanning using a three-axis displacement stage;

[0010] Initial particles are randomly placed on an axial plane where the light spot area is smaller and the received light intensity is greater.

[0011] After setting the particle swarm parameters, the inertia weight and particle number are iteratively updated using the dynamic PSO particle swarm optimization method.

[0012] Calculate and update the particle position and obtain the received light intensity value, and converge to determine the optimal relative position of the laser optical axis and the detector at close range;

[0013] S3. Calculate the difference between the image distance of the near target and the image distance of the target at infinity, and obtain the distance that the detector needs to move along the optical axis. By controlling the three-axis displacement stage to move the Z-axis by the corresponding distance, axial compensation is completed.

[0014] Based on the motor speed, target distance, and light speed, the target echo offset angle caused by the time difference during laser scanning is calculated, and then the maximum radial displacement of the echo spot center is obtained. Combined with the radius constraint of the circular detector target surface, the distance that the detector needs to move radially along the optical axis is determined, and the three-axis displacement stage is controlled to move this distance along the X-axis to complete the radial compensation.

[0015] Furthermore, the specific method for automatically adjusting the laser ranging module's emission power based on feedback in step S1 is as follows:

[0016] The initial laser emission power is set to an empirical constant, and the three-axis displacement stage is controlled to quickly and roughly scan in space. If the detector does not receive effective echo information, the emission power energy is too low, and the system automatically increases the energy to rescan until the detector receives an effective echo signal.

[0017] If the detector receives a saturation signal, the transmitted power energy is too high, and the received light intensity near the saturation area is higher than other areas. The location information of the saturation signal area is preserved, the laser power is reduced, and the area is scanned again until there is no intensity saturation point in the area and the detector can receive effective echo information.

[0018] Furthermore, the method for calculating the received light intensity in S2 is as follows:

[0019] Treating the laser as a Gaussian beam, the target as a Lambertian plane, and neglecting aberrations; according to the Gaussian imaging formula, under ideal conditions, its intensity distribution on the image plane is:

[0020] ,

[0021] in, The light intensity coefficient, , Represents the radial spatial position. Reduce the light intensity at the target location to the light intensity at the center. The beam radius at that location This refers to the distance between the laser emitted by the lidar and the target. Focal length;

[0022] Considering diffraction and defocusing, the spatial intensity distribution of parallel light emitted from an infinity point source after passing through an irregularly shaped aperture stop and optical system is as follows:

[0023] ,

[0024] in, This is the defocus amount. The amplitude of the incident plane wave, For wave number, Transmittance of irregular aperture complex amplitude;

[0025] For a point target at close range, it is equivalent to a target at infinity passing through a concave lens and then being focused by an optical system. At this time, the focal plane of the equivalent optical system composed of the virtual concave lens and the optical system is the image plane of the point target at close range, that is, the equivalent focal point is the image distance.

[0026] Treating the three-dimensional spatial energy distribution of the light intensity from the point source as a point spread function, the final light intensity distribution of the echo spot at the detector target surface is:

[0027] ,

[0028] According to the formula at close range The equivalent focal position of the optical system is the position of the maximum light spot intensity.

[0029] Furthermore, the particle swarm parameters in S2 include:

[0030] Initial number of search particles Minimum threshold for particle number, inertia weight maximum value and minimum value Individual learning factor, group learning factor, maximum number of iterations and the search boundary in three-dimensional space; wherein the initial number of particles is not less than 30.

[0031] Furthermore, the inertia weight iterative update method in S2 is as follows:

[0032] In each iteration, the inertia weights are updated by decreasing a quadratic function. The weight calculation formula is as follows:

[0033] ,

[0034] in, This represents the current iteration number. By dynamically adjusting the inertia weight, the inertia weight decreases slowly in the early stages, resulting in a greater proportion of global search. In the later stages, the inertia weight decreases more rapidly, enhancing the search precision in the local space, which aligns with the actual search principle of starting with the overall and then moving to the local.

[0035] Furthermore, the particle number iterative update method in S2 is as follows:

[0036] The particle count is dynamically adjusted by decreasing it based on the number of iterations. The calculation formula is as follows:

[0037] ,

[0038] in, This represents the current iteration number. The minimum threshold for the number of particles is set.

[0039] By dynamically adjusting the number of particles during the iteration process, the particle swarm with the largest difference from the target is removed. Using individual particles improves overall computational efficiency, reduces redundancy, and enables the system to converge quickly and stably.

[0040] Furthermore, the specific method for calculating the axial compensation in S3 is as follows:

[0041] For echoes at different distances, long-distance echoes can be approximated as parallel light, with the light spot focused at the focal point of the optical system; short-distance echoes are focused behind the focal point, a position that can be calculated using the Gaussian imaging formula:

[0042] ,

[0043] in, Image distance, This refers to the distance between the indoor near-range target and the ranging module.

[0044] To meet the ranging requirements at medium to long distances, the detector position is compensated along the axial direction, and the distance moved is [not specified]. for:

[0045] ,

[0046] In the formula, Indicates focal length.

[0047] Furthermore, the specific method for calculating the radial compensation in S3 is as follows:

[0048] When the motor rotates at high speed, due to the time difference between laser emission and echo reception, the scanning mechanism has rotated a certain angle during this time difference. This causes the laser endpoint to shift from the instantaneous field of view center when the target echo is received by the lidar. In other words, the focusing position of the echo after passing through the receiving optical system shifts from the center of the detector target surface. The angle of this shift is:

[0049] ,

[0050] in, The laser scanning line speed, The distance between the target and the lidar. The speed of light;

[0051] When the offset angle exceeds the field of view, the ranging module will be unable to receive the echo signal, severely affecting the long-range ranging capability of the lidar under high-speed scanning. Radial offset allows the system to still receive echo signals at varying distances even while the motor is rotating. This is achieved by considering the radius of the circular detector target surface. Constraints and effective detection capability of targets at different distances under different rotation speeds, radial compensation The following conditions must be met:

[0052] ,

[0053] ,

[0054] in, This represents the maximum displacement of the echo spot center under the constraints of the system's maximum rotational speed and maximum distance measurement parameters.

[0055] As a second aspect of the present invention, a laser optical axis and detector automatic alignment system is provided, comprising:

[0056] The transmission power adjustment unit is used to obtain the coordinates of the echo signal by controlling the three-axis displacement stage to scan and automatically adjust the transmission power of the laser ranging module according to the feedback, and confirm the final transmission power.

[0057] The spatial search unit is used to determine the spatial range of the echo signal by controlling a three-axis displacement stage to scan.

[0058] Initial particles are randomly placed on an axial plane where the light spot area is smaller and the received light intensity is greater.

[0059] After setting the particle swarm parameters, the inertia weight and particle number are iteratively updated using the dynamic PSO particle swarm optimization method.

[0060] Calculate and update the particle position and obtain the received light intensity value, and converge to determine the optimal relative position of the laser optical axis and the detector at close range;

[0061] The dynamic compensation off-target unit is used to calculate the difference between the image distance of the near target and the image distance of the infinity target, and to determine the distance that the detector needs to move along the optical axis. By controlling the three-axis displacement stage to move the Z-axis by the corresponding distance, axial compensation is completed.

[0062] Based on the motor speed, target distance, and light speed, the target echo offset angle caused by the time difference during laser scanning is calculated, and then the maximum radial displacement of the echo spot center is obtained. Combined with the radius constraint of the circular detector target surface, the distance that the detector needs to move radially along the optical axis is determined, and the three-axis displacement stage is controlled to move this distance along the X-axis to complete the radial compensation.

[0063] As a third aspect of the invention, a computer-readable storage medium is also provided, on which a computer program is stored, which is executed by a processor of any step of the laser optical axis and detector automatic alignment method.

[0064] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0065] 1. The automatic laser optical axis and detector alignment method of the present invention achieves adaptive adjustment of laser emission power by establishing an emission power control algorithm. During the detection process, for different distance targets and laser models, the system sets the initial laser emission power to an empirical constant and controls the three-axis displacement stage to scan the echo signal. If no valid echo is received, the power is automatically increased; if a saturation signal appears, the position is recorded and the power is reduced to rescan until a valid and non-saturated echo signal is obtained. This algorithm effectively avoids the problem of signal saturation caused by excessive emission power or the echo being submerged in noise due to insufficient power, ensuring that the laser emission power is always within a suitable range, providing a stable signal basis for accurately determining the focal position, and significantly improving the reliability and stability of the alignment process.

[0066] 2. The automatic laser optical axis and detector alignment method of this invention achieves rapid and accurate positioning of the equivalent focal position of a near-range target by constructing a spatial search algorithm combined with a dynamic PSO particle swarm optimization algorithm. In three-dimensional space, a precision displacement stage is first controlled to perform a millimeter-level coarse search to determine the echo signal region. Then, based on the spot size and intensity distribution characteristics, initial search particles are rationally deployed on the key plane. During algorithm operation, the inertial weight is updated by decreasing a quadratic function to balance global and local search capabilities; the number of particles is dynamically adjusted based on the number of iterations to reduce redundant calculations. After multiple iterations to update particle positions and record the received light intensity, the algorithm finally converges to obtain the position of the maximum received light intensity, achieving micrometer-level precision search. This significantly improves alignment efficiency and accuracy, overcoming the shortcomings of traditional methods such as slow positioning and low accuracy.

[0067] 3. The automatic laser optical axis and detector alignment method of this invention solves the target miss problem in medium- and long-range ranging and motor rotation scenarios by establishing a dynamic compensation off-target algorithm. The axial offset is calculated based on the Gaussian imaging formula, and the precision three-axis displacement stage is controlled to move along the Z-axis to compensate for the defocusing caused by changes in target distance. Combining motor speed, target distance, and light speed, the echo offset angle and maximum radial displacement are calculated. The radial compensation amount is determined based on the detector target surface constraint, and the X-axis movement is controlled to complete the radial compensation. This algorithm effectively eliminates the influence of distance and motor rotation on echo reception, ensuring that the detector can accurately receive echo signals under different operating conditions. It significantly improves the detection performance and adaptability of the lidar in dynamic environments, enabling the system to maintain good working condition even in complex application scenarios. Attached Figure Description

[0068] Figure 1 This is a flowchart of a method for automatically aligning the laser optical axis with the detector according to an embodiment of the present invention;

[0069] Figure 2 This is a device layout diagram according to an embodiment of the present invention;

[0070] Figure 3 This is a flowchart of the algorithm according to an embodiment of the present invention;

[0071] Figure 4 This is a system unit diagram of an embodiment of the present invention. Detailed Implementation

[0072] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0073] Example 1

[0074] Please refer to Figure 1 This embodiment 1 provides a method for automatically aligning the laser optical axis with the detector, including:

[0075] S1. The echo signal coordinates are obtained by scanning through a three-axis displacement stage. The laser ranging module’s transmission power is automatically adjusted based on the feedback to confirm the final transmission power.

[0076] S2. The spatial range of the echo signal is determined by scanning through a three-axis displacement stage; initial particles are randomly placed on the axial plane where the light spot area is smaller and the received light intensity is greater; after setting the particle swarm parameters, the inertial weight and the number of particles are iteratively updated by the dynamic PSO particle swarm optimization method; the particle positions are calculated and updated and the received light intensity value is obtained, and the optimal relative position between the laser optical axis and the detector is determined by convergence.

[0077] S3. Calculate the difference between the image distance of the near target and the image distance of the infinitely far target to obtain the distance that the detector needs to move along the optical axis. By controlling the Z-axis of the three-axis displacement stage to move the corresponding distance, axial compensation is completed. Based on the motor speed, target distance and light speed, calculate the target echo offset angle caused by the time difference during laser scanning, and then obtain the maximum radial displacement of the echo spot center. Combined with the radius constraint of the circular detector target surface, determine the distance that the detector needs to move radially along the optical axis. Control the X-axis of the three-axis displacement stage to move this distance to complete radial compensation.

[0078] This embodiment 1 further elaborates on the above content:

[0079] Please refer to Figure 2 This embodiment 1 proposes a method and apparatus for automatically aligning the laser optical axis with the detector. It fixes the laser transmitter of the lidar and the echo receiving optical system, PD board, and high-speed ADC acquisition chip in the ranging module. A photodetector is installed on a precision three-axis displacement stage, where the Z-axis of the displacement stage is the axial direction of the optical axis, and the X and Y directions are the radial directions of the optical axis. In an indoor environment, the control device emits a laser towards a fixed target. By controlling the movement of the precision three-axis displacement stage in space, the position of the maximum light intensity received by the detector is found, completing the focus position search within the close-range range. Then, a dynamic compensation algorithm for missing the target is established to compensate for the scanning miss amount in long-range ranging.

[0080] Please refer to Figure 3 In this embodiment 1, the relative position between the detector and the optical system is controlled by controlling the laser emission power and the movement of the precision three-axis displacement stage.

[0081] (1) Establish a transmit power control algorithm

[0082] The laser power emitted varies depending on the target's distance and the type of laser used. Excessive power will result in numerous saturation points within the scanning area; conversely, insufficient power will cause the echo signal to be submerged in environmental noise, both affecting the determination of the focal point. Therefore, a power control algorithm is established based on the strength of the received signal: the initial laser emission power is set to an empirical constant, and the three-axis stage is rapidly and coarsely scanned in space. If the detector does not receive valid echo information, the emission power is too low, and the system automatically increases the power and rescans until the detector receives a valid echo signal. If the detector receives a saturated signal, the emission power is too high, and the received light intensity near the saturation area is higher than in other areas. The position information of the saturated signal area is preserved, the laser power is reduced, and the area is scanned again until no intensity saturation points appear and the detector receives valid echo information. This ensures that the laser emission power is controlled within a suitable range during subsequent scanning.

[0083] (2) Establishing a spatial search algorithm

[0084] Due to the influence of various factors such as laser beam energy distribution, target surface characteristics, anisotropic aperture, defocusing, diffraction, and aberrations, the echo focused on the detector target surface is a light spot with a certain spatial energy distribution. For ease of analysis, the laser is considered a Gaussian beam, the target is considered a Lambertian plane, and the influence of aberrations is ignored. According to the Gaussian imaging formula, under ideal conditions, its intensity distribution on the image plane is:

[0085] ,

[0086] in, The light intensity coefficient, , Represents the radial spatial position. Reduce the light intensity at the target location to the light intensity at the center. The beam radius at that location This refers to the distance between the laser emitted by the lidar and the target. It is the focal length.

[0087] Considering diffraction and defocusing, the spatial intensity distribution of parallel light emitted from an infinity point source after passing through an irregularly shaped aperture stop and optical system is as follows:

[0088] ,

[0089] in, This is the defocus amount. The amplitude of the incident plane wave, For wave number, The transmittance of the complex amplitude of the irregular aperture.

[0090] For a point target at close range, it can be equivalent to a target at infinity passing through a concave lens and then being focused by an optical system. In this case, the focal plane of the equivalent optical system formed by the virtual concave lens and the optical system is the image plane of the point target at close range, that is, the equivalent focal point is the image distance.

[0091] Treating the three-dimensional spatial energy distribution of the light intensity from the point source as a point spread function, the final light intensity distribution of the echo spot at the detector target surface is:

[0092] ,

[0093] According to the above formula, close range The equivalent focal position of the optical system is the location of the maximum light spot intensity. A millimeter-level coarse search is performed by moving a precision displacement stage in three-dimensional space to find the region where the detector receives the echo signal. The PSO (Particle Swarm Optimization) algorithm is then used to find the location of the point with the maximum intensity in space. The specific steps are as follows:

[0094] According to the above formula, the received light intensity distribution in space exhibits the characteristics of greater intensity and smaller spot radius closer to the focal point, and smaller intensity and larger spot radius farther from the focal point. When selecting initial search particles, considering both the spot size and maximum intensity on each XY plane, more initial search particles are set on planes with smaller spots and higher intensity, totaling no fewer than 30 initial search particles, with their initial velocity set to 0.

[0095] Set the initial number of search particles Inertia weight maximum value and minimum value Learning factors for individuals and groups, maximum number of iterations And the search boundary in three-dimensional space. To find the location of the point with the maximum light intensity in space as accurately and quickly as possible, the dynamic PSO particle swarm algorithm is used.

[0096] In each iteration, the inertia weights are updated by decreasing a quadratic function. The weight calculation formula is as follows:

[0097] ,

[0098] in, This represents the current iteration number. By dynamically adjusting the inertia weight, the inertia weight decreases slowly in the early stages, giving greater weight to global search, while in the later stages, the inertia weight decreases more rapidly, enhancing the search precision within the local space, which aligns with the actual search principle of starting with the global and then moving to the local.

[0099] The particle count is dynamically adjusted by decreasing it based on the number of iterations. The calculation formula is as follows:

[0100] ,

[0101] in, This represents the current iteration number. This sets a minimum threshold for the number of particles. By dynamically adjusting the number of particles during the iteration process, the particle swarm with the largest deviation from the target is removed. Increasing the number of particles can improve overall computational efficiency, reduce redundancy, and enable the system to converge quickly and stably.

[0102] Based on the Particle Swarm Optimization (PSO) algorithm, the velocity and position of each particle are updated through multiple iterations. The detector is moved to the corresponding position, and the received light intensity at the corresponding position is recorded. This allows the local and global optimal positions to be found, and finally converges to obtain the position of the maximum received light intensity, achieving micron-level precision search for the position of the equivalent focal point at close range indoors.

[0103] (3) Establish a dynamic compensation off-target algorithm

[0104] It achieves good echo reception even when measuring distances at varying distances while the motor is rotating.

[0105] For echoes at different distances, long-distance echoes can be approximated as parallel light, with the light spot focused at the focal point of the optical system; short-distance echoes are focused behind the focal point, a position that can be calculated using the Gaussian imaging formula:

[0106] ,

[0107] in, Image distance, This represents the distance between the indoor near-range target and the ranging module. To meet the ranging requirements at medium to long ranges, the detector position is compensated along the axial direction, shifting the distance... for:

[0108] ,

[0109] When the motor rotates at high speed, due to the time difference between laser emission and echo reception, the scanning mechanism has rotated a certain angle during this time difference. This causes the laser's focal point to shift from the instantaneous field of view center when the target echo is received by the lidar. In other words, the focusing position of the echo after passing through the receiving optical system shifts from the center of the detector target surface. The angle of this shift is:

[0110] ,

[0111] in, The laser scanning line speed, The distance between the target and the lidar. The speed is the speed of light. When the offset angle exceeds the field of view, the ranging module will be unable to receive the echo signal, severely affecting the long-range ranging capability of the lidar under high-speed scanning. Radial offset allows the system to still receive echo signals at varying distances even when the motor is rotating; the radial compensation magnitude... Satisfying:

[0112] ,

[0113] ,

[0114] in, This represents the maximum displacement of the echo spot center under the constraints of the system's highest rotational speed and furthest ranging parameters. Taking into account the radius of the circular detector target surface... Constraints and effective detection capability of targets at different distances under different rotation speeds, radial compensation The above formula must be satisfied.

[0115] By controlling a precision three-axis displacement stage, the detector is compensated in the radial and axial directions. Then, the relative positions between the detector and the optical system are fixed by means of welding, gluing, etc., so as to complete the automatic alignment of the laser optical axis and the detector.

[0116] In some specific scenarios, the above method is applied in preferred embodiments. In these preferred embodiments, the components involved include: a laser for emitting pulsed laser light, and a laser wavelength. Laser divergence angle The optical system of the ranging module is used for collimating the emitted pulsed laser and focusing the target echo; the aperture of the receiving optical system is [not specified]. ,focal length The detector, used to photoelectrically convert the reference light and the target echo, employs an APD detector with a target surface radius of [missing information]. The system includes: a shaping and amplification circuit for shaping and amplifying the weak signal after photoelectric conversion from the detector; an ADC acquisition circuit for digitizing the echo analog signal using a high-speed ADC chip; a control and signal processing module for processing the digitized echo signal, as well as controlling components such as the laser and peripheral sensors; a detector clamping and moving device for adjusting the relative position of the detector or the circuit board it is mounted on to the optical system, clamping the detector on a precision three-axis displacement stage controlled by a stepper motor, with a movable range of ±1cm, controlling the relative position between the detector and the optical system with sub-micron level precision; and a control method for automatic alignment of the laser optical axis and the detector, controlling the movement of the precision three-axis displacement stage and real-time reception of the echo signal intensity.

[0117] The detector clamping and moving device can be an internal module of the lidar or an auxiliary device during the assembly and adjustment process, and it is removed after the detector position is adjusted and fixed.

[0118] The preferred embodiment adjusts the relative positional relationship between the detector and the optical system. Therefore, the method of adjusting the position of the optical system while keeping the detector stationary is also covered in the preferred embodiment.

[0119] The following are the specific implementation steps of the preferred embodiment.

[0120] Step 1: Determine the emission power of the laser ranging module. In an indoor environment, set up a standard reflectivity plate with a reflectivity of 80% as the target object at a distance of 10.5m from the ranging module, and restore the precision three-axis displacement stage to its center position. If the initial transmission power is manually set to 100, and the three-axis displacement stage is controlled to perform an S-shaped scan within the range to roughly scan the echo signal intensity and its corresponding coordinate position, then due to the low power, there is no effective echo signal. The system automatically controls the laser to adjust the transmission power to 110. At this point, an effective echo signal appears within the range and there is no saturated echo signal, and the transmission power adjustment is complete. If the initial transmission power is manually set to 150, and the three-axis displacement stage is controlled to perform an S-shaped scan within the range to roughly scan the echo signal intensity and its corresponding coordinate position, then due to the high power, multiple saturated echo signals are received. The system records the spatial position of the saturated echo signal and reduces the transmission power. It then performs an S-shaped scan on the saturated echo signal area until no saturated echo signal appears in the area and an effective echo can be received. The system automatically controls the laser to adjust the transmission power to 115, and the transmission power adjustment is complete.

[0121] Step 2: Establish a spatial search algorithm to automatically align the laser optical axis with the detector in close-range environments. By controlling the three-axis displacement stage to move and scan in an S-shape within its range, the spatial range in the spatial domain where echo signals can be received is found. The experiment calculated the area of ​​the light spot on the axial plane with different radial values. Considering both the size of the light spot area and the maximum received light intensity, more initial particles were randomly placed on the axial plane with smaller light spot areas and higher received light intensity, ensuring that the number of initial particles was no less than 30. In the experiment, it was found that there were 5 controller axial planes that received effective echoes. Based on the size of the light spot area and the maximum received light intensity on these planes, 10, 8, 6, 4, and 2 initial particles were randomly placed, respectively.

[0122] Set the initial number of search particles Minimum particle number threshold 5, inertia weight The maximum value is 0.9 and the minimum value is 0.4, the individual learning factor is 2, the group learning factor is 2, the maximum number of iterations is 10, and the search boundary in three-dimensional space is... The dynamic PSO (Particle Swarm Optimization) algorithm is used to dynamically adjust the inertia weight and the number of search particles in each iteration, calculate and update the position of the particles, and then obtain the received light intensity value at the corresponding position. After multiple iterations, the global optimal position is obtained, thus finding the optimal relative position between the laser optical axis and the detector in a close-range environment.

[0123] Step 3: Establish a dynamic compensation off-target algorithm to achieve position compensation at medium to long ranges in dynamic environments. Utilize the distance traveled... The formula for calculating the distance to infinity and 10.5 The axial offset between the distances is approximately 97.82. Control the Z-axis displacement stage to compensate for axial offset; within the measurement range of Maximum motor speed revolutions per second, depending on the radial compensation magnitude The relevant formulas calculate that the maximum miss distance of the target at this time is approximately Therefore, to ensure All echo spots can be detected by the detector; the radial deviation is set to... The precision three-axis displacement stage is controlled to compensate for radial offset in the X direction, thus achieving dynamic compensation for target miss.

[0124] Step 4: After automatically aligning the laser optical axis with the detector, fix the relative position between the detector and the optical system using a fixing device. The fixing device can be a mechanical structure such as a positioning screw or locking mechanism, or it can be made of materials such as optical adhesive, UV adhesive, or solder.

[0125] Example 2

[0126] Please refer to Figure 4 This embodiment 2 provides an automatic laser optical axis and detector alignment system, including:

[0127] The transmission power adjustment unit is used to obtain the coordinates of the echo signal by controlling the three-axis displacement stage to scan and automatically adjust the transmission power of the laser ranging module according to the feedback, and confirm the final transmission power.

[0128] The spatial search unit is used to determine the spatial range of the echo signal by scanning through a three-axis displacement stage; initial particles are randomly deployed on the axial plane where the light spot area is smaller and the received light intensity is greater; after the particle swarm parameters are set, the inertial weight and the number of particles are iteratively updated through the dynamic PSO particle swarm optimization method; the particle positions are calculated and updated and the received light intensity value is obtained, and the optimal relative position between the laser optical axis and the detector is determined by convergence.

[0129] The dynamic compensation off-target unit is used to calculate the difference between the image distance of the near target and the image distance of the infinitely far target, and to determine the distance that the detector needs to move along the optical axis. By controlling the Z-axis of the three-axis displacement stage to move the corresponding distance, axial compensation is completed. Based on the motor speed, target distance and light speed, the target echo offset angle caused by the time difference during laser scanning is calculated, and then the maximum radial displacement of the echo spot center is obtained. Combined with the radius constraint of the circular detector target surface, the distance that the detector needs to move radially along the optical axis is determined, and the X-axis of the three-axis displacement stage is controlled to move the distance to complete the radial compensation.

[0130] Example 3

[0131] This embodiment 3 also provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it can implement any step of a method for automatically aligning a laser optical axis with a detector.

[0132] The computer-readable storage medium may include various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0133] For a description of the computer-readable storage medium provided in this application, please refer to the above method embodiments; further details will not be repeated here.

[0134] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for automatically aligning a laser optical axis with a detector, characterized in that, include: S1. The echo signal coordinates are obtained by scanning through a three-axis displacement stage. The laser ranging module’s transmission power is automatically adjusted based on the feedback to confirm the final transmission power. S2. The spatial range of the echo signal is determined by scanning through a three-axis displacement stage; initial particles are randomly placed on the axial plane where the light spot area is smaller and the received light intensity is greater; after setting the particle swarm parameters, the inertial weight and the number of particles are iteratively updated by the dynamic PSO particle swarm optimization method; the particle positions are calculated and updated and the received light intensity value is obtained, and the optimal relative position between the laser optical axis and the detector is determined by convergence. S3. Calculate the difference between the image distance of the near target and the image distance of the infinitely far target to obtain the distance that the detector needs to move along the optical axis. By controlling the Z-axis of the three-axis displacement stage to move the corresponding distance, axial compensation is completed. Based on the motor speed, target distance and light speed, calculate the target echo offset angle caused by the time difference during laser scanning, and then obtain the maximum radial displacement of the echo spot center. Combined with the radius constraint of the circular detector target surface, determine the distance that the detector needs to move radially along the optical axis. Control the X-axis of the three-axis displacement stage to move this distance to complete radial compensation.

2. The method for automatically aligning the laser optical axis with the detector according to claim 1, characterized in that, The specific method for automatically adjusting the laser ranging module's emission power based on feedback in S1 is as follows: The initial laser emission power is set to an empirical constant, and the three-axis displacement stage is controlled to quickly and roughly scan in space. If the detector does not receive effective echo information, the emission power energy is too low, and the system automatically increases the energy to rescan until the detector receives an effective echo signal. If the detector receives a saturation signal, the transmitted power energy is too high, and the received light intensity near the saturation area is higher than other areas. The location information of the saturation signal area is preserved, the laser power is reduced, and the area is scanned again until there is no intensity saturation point in the area and the detector can receive effective echo information.

3. The method for automatically aligning the laser optical axis with the detector according to claim 1, characterized in that, The method for calculating the intensity of the light received in S2 is as follows: Treating the laser as a Gaussian beam, the target as a Lambertian plane, and neglecting aberrations; according to the Gaussian imaging formula, under ideal conditions, its intensity distribution on the image plane is: ， in, The light intensity coefficient, , Represents the radial spatial position. Reduce the light intensity at the target location to the light intensity at the center. The beam radius at that location This refers to the distance between the laser emitted by the lidar and the target. Focal length; Considering diffraction and defocusing, the spatial intensity distribution of parallel light emitted from an infinity point source after passing through an irregularly shaped aperture stop and optical system is as follows: ， in, This is the defocus amount. The amplitude of the incident plane wave, For wave number, Transmittance of irregular aperture complex amplitude; Indicates wavelength; For a point target at close range, it is equivalent to a target at infinity passing through a concave lens and then being focused by an optical system. At this time, the focal plane of the equivalent optical system composed of the virtual concave lens and the optical system is the image plane of the point target at close range, that is, the equivalent focal point is the image distance. Treating the three-dimensional spatial energy distribution of the light intensity from the point source as a point spread function, the final light intensity distribution of the echo spot at the detector target surface is: ， According to the formula at close range The equivalent focal position of the optical system is the position of the maximum light spot intensity.

4. The method for automatically aligning the laser optical axis with the detector according to claim 1, characterized in that, The particle swarm parameters in S2 include: Initial number of search particles Minimum threshold for particle number, inertia weight maximum value and minimum value Individual learning factor, group learning factor, maximum number of iterations and the search boundary in three-dimensional space; wherein the initial number of particles is not less than 30.

5. The method for automatically aligning the laser optical axis with the detector according to claim 1, characterized in that, The inertial weight iterative update method in S2 is as follows: In each iteration, the inertia weights are updated by decreasing a quadratic function. The weight calculation formula is as follows: ， in, This represents the current iteration number. By dynamically adjusting the inertia weight, the inertia weight decreases slowly in the early stages, resulting in a larger proportion of global search. In the later stages, the inertia weight decreases more rapidly, enhancing the search precision in the local space, which aligns with the actual search principle of starting with the overall and then moving to the local. This represents the maximum value of the inertia weight. This represents the minimum inertial weight, which is preset manually. This indicates the maximum number of iterations.

6. The method for automatically aligning the laser optical axis with the detector according to claim 1, characterized in that, The particle number iterative update method in S2 is as follows: The particle count is dynamically adjusted by decreasing it based on the number of iterations. The calculation formula is as follows: ， in, This represents the current iteration number. The minimum threshold for the number of particles is set. Indicates the maximum number of iterations By dynamically adjusting the number of particles during the iteration process, the particle swarm with the largest difference from the target is removed. Using individual particles improves overall computational efficiency, reduces redundancy, and enables the system to converge quickly and stably.

7. The method for automatically aligning the laser optical axis with the detector according to claim 2, characterized in that, The specific method for calculating the axial compensation in S3 is as follows: For echoes at different distances, long-distance echoes can be approximated as parallel light, with the light spot focused at the focal point of the optical system; short-distance echoes are focused behind the focal point, a position that can be calculated using the Gaussian imaging formula: ， in, Image distance, This refers to the distance between the indoor near-range target and the ranging module. To meet the ranging requirements at medium to long distances, the detector position is compensated along the axial direction, and the distance moved is [not specified]. for: ， In the formula, Indicates focal length.

8. The method for automatically aligning the laser optical axis with the detector according to claim 2, characterized in that, The specific method for calculating the radial compensation in S3 is as follows: When the motor rotates at high speed, due to the time difference between laser emission and echo reception, the scanning mechanism has rotated a certain angle during this time difference. This causes the laser endpoint to shift from the instantaneous field of view center when the target echo is received by the lidar. In other words, the focusing position of the echo after passing through the receiving optical system shifts from the center of the detector target surface. The angle of this shift is: ， in, The laser scanning line speed, The distance between the target and the lidar. The speed of light; When the offset angle exceeds the field of view, the ranging module will be unable to receive the echo signal, severely affecting the long-range ranging capability of the lidar under high-speed scanning. Radial offset allows the system to still receive echo signals at varying distances even while the motor is rotating. This is achieved by considering the radius of the circular detector target surface. Constraints and effective detection capability of targets at different distances under different rotation speeds, radial compensation The following conditions must be met: ， ， in, This represents the maximum displacement of the echo spot center under the constraints of the system's maximum rotational speed and maximum distance measurement parameters. Indicates focal length; This indicates the system's maximum ranging range.

9. A laser optical axis and detector automatic alignment system, characterized in that, include: The transmission power adjustment unit is used to obtain the coordinates of the echo signal by controlling the three-axis displacement stage to scan and automatically adjust the transmission power of the laser ranging module according to the feedback, and confirm the final transmission power. The spatial search unit is used to determine the spatial range of the echo signal by scanning through a three-axis displacement stage; initial particles are randomly deployed on the axial plane where the light spot area is smaller and the received light intensity is greater; after the particle swarm parameters are set, the inertial weight and the number of particles are iteratively updated through the dynamic PSO particle swarm optimization method; the particle positions are calculated and updated and the received light intensity value is obtained, and the optimal relative position between the laser optical axis and the detector is determined by convergence. The dynamic compensation off-target unit is used to calculate the difference between the image distance of the near target and the image distance of the infinitely far target, and to determine the distance that the detector needs to move along the optical axis. By controlling the Z-axis of the three-axis displacement stage to move the corresponding distance, axial compensation is completed. Based on the motor speed, target distance and light speed, the target echo offset angle caused by the time difference during laser scanning is calculated, and then the maximum radial displacement of the echo spot center is obtained. Combined with the radius constraint of the circular detector target surface, the distance that the detector needs to move radially along the optical axis is determined, and the X-axis of the three-axis displacement stage is controlled to move the distance to complete the radial compensation.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, The computer program is executed by the processor using the automatic laser optical axis and detector alignment method according to any one of claims 1-8.

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