Optical phased array laser radar and scanning method based on edge contour

Abstract

The invention relates to the technical field of laser radar scanning, in particular to an optical phased array laser radar and a scanning method based on an edge contour, and the scanning method comprises the steps: S1, obtaining a gray-scale map of a scene; and S2, extracting an edge contour by adopting an edge contour recognition algorithm, obtaining a point cloud coordinate set uniformly distributed around an edge contour line in a dot matrix form, and recording a scanning phase angle of the optical phased array corresponding to the to-be-measured point. And S3, mapping the coordinate of each point to be measured into a driving voltage value of the optical phased array and an emission wavelength value of the laser through a preset scanning lookup table. And S4, controlling the optical phased array laser radar to scan the edge contours in sequence to obtain point cloud data. The method has the advantages that redundant data are reduced through edge contour extraction, the complexity of subsequent data processing is reduced, and technical support is provided for optical phased array laser radar scanning imaging with higher performance and energy efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser radar scanning, and in particular to an optical phased array laser radar and a scanning method based on an edge profile. BACKGROUND

[0002] An optical phased array (OPA) is a beam pointing technology that dynamically controls the direction, shape and intensity of a light beam by adjusting the phase. An OPA laser radar, which takes an OPA chip as the core, integrates laser ranging and imaging technologies. Its phase control mainly relies on two modulation methods: electro-optic modulation and thermo-optic modulation. The former changes the carrier concentration and refractive index by applying a voltage to the PN junction of the waveguide, and the latter adjusts the temperature by driving voltage to achieve phase control.

[0003] In two-dimensional scanning, an OPA laser radar controls the transverse scanning phase angle by driving voltage and simultaneously changes the laser wavelength to realize longitudinal scanning, thereby covering the entire two-dimensional scene.

[0004] However, the existing OPA laser radar needs to be combined with additional photoelectric detection devices such as cameras to realize the recognition of ROI (region of interest), and the scanning speed is limited. The writing, configuration speed and voltage establishment speed of the control signal together constitute the main bottleneck, which leads to a too low frame rate when performing global scanning, making it difficult to meet the demand of high-speed three-dimensional point cloud acquisition. In addition, in practical applications (such as vehicle-mounted radar), indiscriminate global scanning of low-value areas such as the sky and the road not only generates a large amount of redundant data and wastes hardware resources, but also further restricts the improvement of detection efficiency and frame rate. SUMMARY

[0005] Therefore, the present application proposes an optical phased array laser radar and a scanning method based on an edge profile. Through the internal area array photoelectric detector, the scene is imaged, the profile is extracted, and the OPA laser radar scanning method is autonomously guided. The detection speed of the optical phased array laser radar is improved, the occupation of hardware resources is reduced, the redundant data is effectively eliminated, and the hardware complexity of the subsequent data output and processing module is reduced from the source.

[0006] To achieve the above object, the technical scheme of the present application is implemented as follows: An optical phased array laser radar comprises: a laser for emitting a laser beam to scan objects of a scene; an optical phased array for regulating the laser beam by phase control to change the direction and shape of the laser beam; a planar array photoelectric detector for acquiring a two-dimensional gray scale image of the scene; an image processing module for processing the two-dimensional gray scale image, extracting the edge profile of the two-dimensional gray scale image, and obtaining a periphery point cloud coordinate set of each edge profile; a data processing module for mapping each point coordinate in the point cloud coordinate set into a driving voltage value of the optical phased array and a transmission wavelength value of the laser according to a pre-set scanning lookup table, and generating a control parameter set composed of the driving voltage value and the transmission wavelength value; and a control module for controlling the optical phased array laser radar to scan the profile according to the control parameter set to obtain point cloud data.

[0007] A scanning method based on edge profile is implemented by using the above optical phased array laser radar, and comprises the following steps: S1: acquiring a two-dimensional gray scale image of a scene.

[0008] S2: extracting the edge profile of a target from the two-dimensional gray scale image based on image gray scale difference using an edge profile recognition algorithm to obtain a point cloud coordinate set of the periphery of the edge profile, and recording the scanning phase angle of the optical phased array corresponding to a to-be-measured point in the point cloud.

[0009] S3: mapping the coordinates of the to-be-measured point in the point cloud into a driving voltage value of the optical phased array and a transmission wavelength value of the laser based on the scanning phase angle through a pre-set scanning lookup table, and further generating a control parameter set.

[0010] S4: controlling the optical phased array laser radar to sequentially scan each edge profile according to the control parameter set to generate point cloud data.

[0011] Further, step S2 comprises: performing digital image processing on the two-dimensional gray scale image, extracting the edge profile of the target based on the gray scale difference between pixels using an edge profile detection algorithm, and obtaining a point cloud coordinate set of the periphery of the edge profile.

[0012] Further, the edge profile detection algorithm is implemented by: comparing the gray scale difference between pixels with a pre-set threshold value, and extracting points with a gray scale difference greater than the threshold value to form a profile.

[0013] Further, a geometric offset method based on a normal vector or an inflation method based on image morphology is used to generate the point cloud coordinate set.

[0014] Further, the preset scanning lookup table in step S3 comprises the following steps: driving the optical phased array lidar to scan in the global field of view, recording the transverse angle of each scanning phase angle and the driving voltage value corresponding to the transverse angle, and establishing a transverse scanning lookup table; recording the longitudinal angle of each scanning phase angle and the laser wavelength value corresponding to the longitudinal angle, and establishing a longitudinal scanning lookup table; based on the coordinates of each to-be-measured point, obtaining the driving voltage from the transverse scanning lookup table, and obtaining the laser wavelength from the longitudinal scanning lookup table.

[0015] Further, in step S2, the point cloud coordinate set is uniformly arranged in the periphery of the edge contour in a dot matrix form.

[0016] The application can achieve the following beneficial effects: a two-dimensional gray scale image of a scene is obtained by using a surface array photoelectric detector, a two-dimensional gray scale image in the scene can be obtained without additionally introducing a camera or other detection equipment, the hardware system is simplified, and the cost and complexity are effectively reduced.

[0017] By preprocessing the two-dimensional gray scale image, based on the gray scale difference between pixels, an effective contour is extracted by using an edge detection algorithm, and the identification of a potential important target in the to-be-measured scene can be realized without additionally introducing a photoelectric detection device.

[0018] Based on the gray scale difference between pixels, an effective contour is extracted by using an edge contour detection algorithm, a point cloud coordinate set in the periphery of the edge contour is obtained, the point cloud coordinates are uniformly distributed in the periphery of the edge contour in a dot matrix form, the scanning phase angle required for driving the optical phased array to scan to the to-be-measured point is calculated based on the point cloud coordinates, and then the optical phased array lidar is guided to perform targeted scanning. The flexible steering advantage of the optical phased array is exerted, the potential important target is scanned densely, and the non-important target is scanned sparsely or directly skipped. Redundant data is reduced, and the complexity of subsequent data processing is reduced.

[0019] The method optimizes resource allocation, concentrates limited detection capability on the edge contour of a key target, significantly improves the detection speed of local scanning and the response speed of the system to the target, and finally generates a three-dimensional point cloud with more prominent features and higher quality. In addition, the method reduces redundant data and reduces the complexity of subsequent data processing, thereby providing technical support for realizing an optical phased array lidar scanning imaging with higher performance and energy efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of the application illustrated in the drawings, and their description, are presented to add generic structure of the application and are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. In the drawings: Figure 1 is a flowchart of a scanning method provided according to an embodiment of the application; Figure 2 This is a two-dimensional grayscale image of the scanning field of view of an optical phased array lidar provided according to an embodiment of the present invention; Figure 3 This is an edge contour map extracted from a two-dimensional grayscale image using a contour recognition algorithm, according to an embodiment of the present invention. Figure 4 This is a point cloud coordinate set map provided by an embodiment of the present invention, which is a point cloud coordinate set map uniformly distributed in the form of a dot matrix around the contour line; Figure 5 This is a three-dimensional point cloud map scanned by this method according to an embodiment of the present invention. Detailed Implementation

[0021] 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 specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0023] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] The invention will now be described in detail with reference to specific embodiments.

[0026] like Figures 1 to 5 As shown in the figure, an optical phased array lidar provided by an embodiment of the present invention includes: a laser for emitting a laser beam to scan objects in a scene; an optical phased array for controlling the laser beam through phase control to change the direction and shape of the laser beam; a planar photodetector for acquiring a two-dimensional grayscale image of the scene; an image processing module for processing the two-dimensional grayscale image, extracting the edge contours of the two-dimensional grayscale image, and obtaining a set of peripheral point cloud coordinates for each edge contour; a data processing module for mapping the coordinates of each point in the point cloud coordinate set to the driving voltage value of the optical phased array and the emission wavelength value of the laser according to a pre-set scan lookup table, generating a set of control parameters consisting of the driving voltage value and the emission wavelength value; and a control module for controlling the optical phased array lidar to scan the contours according to the set of control parameters to obtain point cloud data.

[0027] A scanning method based on edge contours, implemented using the aforementioned optical phased array lidar, includes the following steps: S1: The area array photodetector acquires a two-dimensional grayscale image of the scene objects.

[0028] S2: Based on image grayscale differences, an edge contour recognition algorithm is used to extract the edge contour of the target from the two-dimensional grayscale image, obtaining the point cloud coordinate set around the edge contour. Simultaneously, the scanning phase angle of the optical phased array corresponding to the test point in the point cloud is recorded. The point cloud coordinate set is uniformly distributed in a dot matrix form around the edge contour.

[0029] Specifically, the image processing module performs digital image processing on the 2D grayscale image. It preprocesses the original 2D grayscale image (e.g., noise reduction and contrast enhancement) to improve the signal-to-noise ratio. Based on the grayscale differences (grayscale gradients) between pixels, an edge detection algorithm is used to extract the edge contours of the target. The grayscale differences between pixels are compared with a preset threshold, and points with grayscale differences greater than the threshold are extracted to form edge contours, obtaining a set of point cloud coordinates surrounding each edge contour. After these steps, the coordinates of all pixels in the image confirmed as valid edges are extracted, forming a set of point cloud coordinates surrounding the edge contours.

[0030] It should be noted that the preset threshold is an empirical parameter and needs to be flexibly adjusted according to the on-site scenario and detection accuracy requirements. No specific limitation is made here.

[0031] The point cloud coordinate set is evenly distributed in a lattice pattern around the edge contour. This means that the lattice does not just overlap the extracted edge contour, but rather extends outwards and inwards from the contour line of the edge contour as a band-shaped area. The purpose of this is to ensure that even if there are slight deviations in contour recognition, or slight movements in the actual position of the object, the laser beam can completely "cover" the real physical edge.

[0032] The point cloud coordinate set is uniformly distributed in the form of a lattice around the edge contour, which can be achieved in ways including but not limited to the following: The geometric offset method based on normal vectors calculates the unit normal vector of each point in the point cloud of the contour region, and offsets it by a preset distance along the positive and negative directions of the normal vector to generate two extended boundaries, forming a closed strip-shaped polygonal region; then uniform sampling is performed within this polygonal region to generate an extended point cloud coordinate set.

[0033] The image morphology-based dilation method maps the point cloud coordinates of the contour onto a binary image to form a single-pixel-wide contour line; it then performs morphological dilation on the binary image using structuring elements of preset shapes and sizes to generate a band-shaped region; finally, it extracts the coordinates of all pixels within this band-shaped region as an extended point cloud coordinate set, or it can be downsampled and used.

[0034] It should be noted that, regardless of the method used, the purpose is to construct an extended region based on the identified target's edge contour to guide the optical phased array for fine scanning. Those skilled in the art can implement this step by combining known algorithms (such as geometric offset of normal vectors, dilation of image morphology, etc.) according to the above description. In other embodiments, other methods can also be used to uniformly distribute the point cloud coordinate set in a point matrix around the edge contour.

[0035] S3: Based on the scanning phase angle, the data processing module maps the coordinates of the points to be measured in the point cloud to the driving voltage value of the optical phased array and the emission wavelength value of the laser through a pre-set scanning lookup table, thereby generating a set of control parameters.

[0036] The pre-set scan lookup table includes the following steps: drive the optical phased array lidar to scan within the global field of view, record the lateral angle of each scan phase angle and the corresponding drive voltage value, and establish a lateral scan lookup table; record the longitudinal angle of each scan phase angle and the corresponding laser emission wavelength value, and establish a longitudinal scan lookup table; based on the coordinates of each point to be measured, obtain the drive voltage from the lateral scan lookup table and obtain the laser wavelength from the longitudinal scan lookup table.

[0037] Among them, the horizontal scan lookup table and the vertical scan lookup table are used to obtain the corresponding driving voltage and laser wavelength according to the coordinate mapping of each point to be measured during the scanning process.

[0038] The coordinates of each point to be measured are (x1, y1), (x2, y2), ..., (x...). Mi y Mi ), where Mi represents the Mi-th point. A horizontal scan lookup table and a vertical scan lookup table are used to map the control parameter set (V1, λ1), (V2, λ2), ..., (V...) corresponding to the driving voltage V and the emission wavelength λ for each test point. Mi , λ Mi ).

[0039] S4: Based on the set of control parameters, the control module controls the optical phased array lidar to scan each edge contour sequentially and generate point cloud data.

[0040] Steps S1 to S4 are executed iteratively to continuously generate 3D point cloud data of the region of interest.

[0041] The scanning method of the present invention will be described below with reference to a specific embodiment: The original two-dimensional grayscale image obtained by the area array photodetector is processed using a target detection algorithm.

[0042] A planar photodetector acquires the original two-dimensional grayscale image of the scene, as captured by the planar photodetector. The two-dimensional grayscale image is shown below. Figure 2 As shown, The image processing module performs digital image processing on the two-dimensional grayscale image. Based on the grayscale differences between pixels, it uses an edge contour detection algorithm to extract the edge contours of the target, such as... Figure 3 As shown, by comparing the grayscale difference with a preset threshold, all pixels with a difference greater than the threshold are extracted to form an edge contour, thereby obtaining the set of point cloud coordinates around the edge contour.

[0043] The point cloud coordinate set is evenly distributed in a lattice form around the edge contour, forming a band-shaped region centered on the contour line of the edge contour and extending inwards and outwards to both sides, such as... Figure 4 As shown. Subsequently, the scanning phase angle of the optical phased array corresponding to each point to be measured in the point cloud is calculated.

[0044] Based on the calculated scanning phase angle, a pre-set scan lookup table is consulted to map the coordinates of each test point to the driving voltage value of the optical phased array and the emission wavelength value of the laser, thereby generating the final set of control parameters. According to this set of control parameters, the optical phased array lidar is controlled to scan each edge contour sequentially to obtain its high-precision 3D point cloud data. A schematic diagram of the obtained 3D point cloud is shown below. Figure 5 As shown.

[0045] In summary, the scanning method of the present invention uses an area array photodetector to acquire a two-dimensional grayscale image of the scene, without the need for additional detection equipment such as cameras, thus simplifying the hardware system and effectively reducing costs and complexity.

[0046] By preprocessing the two-dimensional grayscale image, an effective edge contour is extracted based on the grayscale difference between pixels using an edge contour detection algorithm. This enables the identification of potentially important targets in the test scene without the need for additional photoelectric detection equipment.

[0047] Based on the grayscale differences between pixels, an edge contour detection algorithm is used to extract effective edge contours, obtaining a set of point cloud coordinates around the edge contours. This set of point cloud coordinates is uniformly distributed in a dot matrix around the edge contours. Simultaneously, the scanning phase angle of the optical phased array corresponding to the point to be measured in the point cloud is recorded, thus guiding the optical phased array lidar to perform targeted scanning. This leverages the flexible steering advantage of the optical phased array, performing dense scanning of potentially important targets while sparsely scanning or skipping non-important targets. This reduces redundant data and lowers the complexity of subsequent data processing.

[0048] This method optimizes resource allocation, concentrating limited detection capabilities on key target contour regions, thereby significantly improving the detection speed of local scanning and the system's response speed to targets. Ultimately, it generates more distinctive and higher-quality 3D point clouds. Furthermore, this method reduces redundant data and lowers the complexity of subsequent data processing, providing technical support for achieving higher performance and energy efficiency in optical phased array lidar scanning imaging.

[0049] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. An optical phased array lidar, comprising: The application relates to a laser radar, and comprises the following parts: a laser for emitting a laser beam to scan an object in a scene; an optical phased array for regulating the laser beam by phase control to change the direction and shape of the laser beam; a planar array photoelectric detector for acquiring a two-dimensional gray scale image of the scene; an image processing module for processing the two-dimensional gray scale image, extracting the edge profile of the two-dimensional gray scale image, and obtaining a point cloud coordinate set of the edge profile; a data processing module for mapping the point cloud coordinate set into a driving voltage value of the optical phased array and a wavelength value of the laser according to a preset scanning lookup table, and generating a control parameter set composed of the driving voltage value and the wavelength value; a control module for controlling the optical phased array laser radar to scan the profile according to the control parameter set, and obtaining point cloud data.

2. A method of edge profile based scanning, implemented using the optical phased array lidar of claim 1, characterized in that, The application comprises the following steps: S1: acquiring a two-dimensional gray scale image of a scene; S2: extracting the edge profile of a target from the two-dimensional gray scale image based on image gray scale difference by using an edge profile recognition algorithm, and obtaining a point cloud coordinate set of the edge profile, and recording the scanning phase angle of the optical phased array corresponding to a to-be-detected point in the point cloud; S3: mapping the coordinates of each to-be-detected point in the point cloud into a driving voltage value of the optical phased array and a wavelength value of the laser according to a preset scanning lookup table based on the scanning phase angle, and then generating a control parameter set; S4: controlling the optical phased array laser radar to sequentially scan each edge profile according to the control parameter set, and generating point cloud data.

3. The edge profile based scanning method of claim 2, wherein, Step S2 comprises: performing digital image processing on the two-dimensional gray scale image, extracting the edge profile of a target based on the gray scale difference between pixels by using an edge profile detection algorithm, and obtaining a point cloud coordinate set of the edge profile.

4. The edge profile based scanning method of claim 3, wherein, The edge profile detection algorithm is realized by comparing the gray scale difference between pixels with a preset threshold value, and extracting points with a gray scale difference greater than the threshold value to form a profile.

5. The edge profile based scanning method of claim 3, wherein, The point cloud coordinate set is generated by using a geometric offset method based on a normal vector or an inflation method based on image morphology.

6. The edge profile based scanning method of claim 2, wherein, The preset scanning lookup table in step S3 comprises the following steps: driving the optical phased array laser radar to scan in a global field of view, recording the transverse angle of each scanning phase angle and the driving voltage value corresponding to the transverse angle, and establishing a transverse scanning lookup table; recording the longitudinal angle of each scanning phase angle and the laser wavelength value corresponding to the longitudinal angle, and establishing a longitudinal scanning lookup table; obtaining the driving voltage from the transverse scanning lookup table and the laser wavelength from the longitudinal scanning lookup table based on the coordinates of each to-be-detected point.

7. The edge profile based scanning method of claim 2, wherein, In step S2, the point cloud coordinate set is uniformly arranged in a dot array form on the periphery of the edge profile.

Images