Optical phased array lidar and edge profile based scanning method

Abstract

The present application relates to the technical field of laser radar scanning, and more particularly to an optical phased array laser radar and a scanning method based on edge contour, the scanning method comprising: S1: acquiring a grayscale image of a scene; S2: extracting an edge contour using an edge contour recognition algorithm, obtaining a point cloud coordinate set uniformly distributed in a dot matrix around the edge contour line, and recording a scanning phase angle of the optical phased array corresponding to a to-be-measured point; S3: mapping the coordinates of each to-be-measured point into a driving voltage value of the optical phased array and a transmission wavelength value of a laser through a pre-set scanning lookup table; and S4: controlling the optical phased array laser radar to sequentially scan each edge contour and acquire point cloud data. The present application has the advantage that edge contour extraction reduces redundant data and reduces the complexity of subsequent data processing, thereby providing technical support for realizing an optical phased array laser radar scanning imaging with higher performance and energy efficiency.

Description

Technical Field

[0001] This invention relates to the field of lidar scanning technology, and more particularly to an optical phased array lidar and a scanning method based on edge contours. Background Technology

[0002] Optical phased array (OPA) is a beam pointing technology that dynamically controls the direction, shape, and intensity of a beam by manipulating its phase. OPA lidar, with an OPA chip at its core, integrates laser ranging and imaging technologies. Its phase control primarily relies on two modulation methods: electro-optic and thermo-optic. Electro-optic modulation changes the carrier concentration and refractive index by applying a voltage to the PN junction of the waveguide; thermo-optic modulation achieves phase control by adjusting the temperature through a driving voltage.

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

[0004] However, existing OPA LiDAR systems require additional photoelectric detection equipment such as cameras to identify ROIs (Regions of Interest), limiting scanning speed. The writing and configuration speeds of control signals, as well as voltage setup speeds, constitute the main bottlenecks, resulting in excessively low frame rates during global scanning, making it difficult to meet the demands of high-speed 3D point cloud acquisition. Furthermore, in practical applications (such as automotive radar), indiscriminate global scanning of low-value areas like the sky and roads 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 of the Invention

[0005] Based on this, this invention proposes an optical phased array lidar and an edge contour-based scanning method. The OPA lidar scanning method uses an internal area array photodetector to image the scene, extract contours, and autonomously guide the scanning process. This improves the detection speed of the optical phased array lidar while reducing hardware resource consumption, effectively eliminating redundant data, and fundamentally reducing the hardware complexity of subsequent data output and processing modules.

[0006] To achieve the above objectives, the technical solution of this invention is implemented as follows: An optical phased array lidar 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.

[0007] A scanning method based on edge contours, implemented using the aforementioned optical phased array lidar, includes the following steps:

[0008] S1: Obtain a 2D grayscale image of the scene.

[0009] S2: Based on the image grayscale difference, an edge contour recognition algorithm is used to extract the edge contour of the target from the two-dimensional grayscale image, obtain the set of point cloud coordinates around the edge contour, and at the same time record the scanning phase angle of the optical phased array corresponding to the point to be measured in the point cloud.

[0010] S3: Based on the scanning phase angle, the coordinates of the points to be measured in the point cloud are mapped 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.

[0011] S4: Based on the set of control parameters, control the optical phased array lidar to scan each edge contour sequentially to generate point cloud data.

[0012] Furthermore, step S2 includes: performing digital image processing on the two-dimensional grayscale image, extracting the edge contour of the target based on the grayscale difference between pixels using an edge contour detection algorithm, and obtaining a set of point cloud coordinates around the edge contour.

[0013] Furthermore, the edge contour detection algorithm is implemented by comparing the grayscale differences between pixels with a preset threshold and extracting points with grayscale differences greater than the threshold to form contours.

[0014] Furthermore, a point cloud coordinate set is generated by employing a geometric offset method based on normal vectors or a dilation method based on image morphology.

[0015] Furthermore, the pre-set scan lookup table in step S3 includes the following steps: driving the optical phased array lidar to scan within the global field of view, recording the lateral angle of each scan phase angle and the driving voltage value corresponding to the lateral angle, and establishing a lateral scan lookup table; recording the longitudinal angle of each scan phase angle and the laser emission wavelength value corresponding to the longitudinal angle, and establishing a longitudinal scan lookup table; based on the coordinates of each point to be measured, obtaining the driving voltage from the lateral scan lookup table, and obtaining the laser wavelength from the longitudinal scan lookup table.

[0016] Furthermore, in step S2, the point cloud coordinate set is evenly distributed in the form of a lattice around the edge contour.

[0017] The present invention can achieve the following beneficial effects: by using an area array photodetector to obtain a two-dimensional grayscale image of a scene, it is possible to obtain a two-dimensional grayscale image of the scene without the need to introduce additional detection equipment such as cameras, which simplifies the hardware system and effectively reduces costs and complexity.

[0018] By preprocessing the two-dimensional grayscale image, an edge detection algorithm is used to extract effective contours based on the grayscale differences between pixels, enabling the identification of potentially important targets in the test scene without the need for additional photoelectric detection equipment.

[0019] Based on the grayscale differences between pixels, an edge contour detection algorithm is used to extract effective contours, obtaining a set of point cloud coordinates around the edge contours. These point cloud coordinates are uniformly distributed in a dot matrix around the edge contours. Based on these point cloud coordinates, the scanning phase angle required to drive the optical phased array to scan to the target point is calculated, thus guiding the optical phased array lidar for 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 less important targets. This reduces redundant data and lowers the complexity of subsequent data processing.

[0020] This method optimizes resource allocation, concentrating limited detection capabilities on the edge contours of key targets, thereby significantly improving the detection speed of local scanning and the system's response speed to targets. Ultimately, it generates more salient 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. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0022] Figure 1 This is a flowchart of a scanning method provided according to an embodiment of the present invention;

[0023] 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;

[0024] 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.

[0025] Figure 4 This is a point cloud coordinate set diagram provided by an embodiment of the present invention, which is a point cloud coordinate set diagram uniformly distributed in the form of a dot matrix around the contour line;

[0026] Figure 5 This is a three-dimensional point cloud map scanned by this method according to an embodiment of the present invention. Detailed Implementation

[0027] 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.

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0029] 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.

[0030] 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.

[0031] The invention will now be described in detail with reference to specific embodiments.

[0032] 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.

[0033] A scanning method based on edge contours, implemented using the aforementioned optical phased array lidar, includes the following steps:

[0034] S1: The area array photodetector acquires a two-dimensional grayscale image of the scene objects.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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:

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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 ).

[0047] 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.

[0048] Steps S1 to S4 are executed iteratively to continuously generate 3D point cloud data of the region of interest.

[0049] The scanning method of the present invention will be described below with reference to a specific embodiment:

[0050] The original two-dimensional grayscale image obtained by the area array photodetector is processed using a target detection algorithm.

[0051] 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,

[0052] 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 3As 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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, characterized in that, include: A laser is used to emit a laser beam to scan objects in a scene. An optical phased array is used to control a laser beam through phase control, thereby changing the direction and shape of the laser beam; A planar photodetector is used to acquire a two-dimensional grayscale image of the scene. The image processing module is used to process the two-dimensional grayscale image, extract the edge contours of the two-dimensional grayscale image, and obtain the set of surrounding point cloud coordinates for each edge contour. The data processing module is used to map 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 the pre-set scanning lookup table, and generate a set of control parameters consisting of the driving voltage value and the emission wavelength value. The control module is used to control the optical phased array lidar to scan the contour according to the set of control parameters to obtain point cloud data.

2. A scanning method based on edge contours, implemented using the optical phased array lidar of claim 1, characterized in that, Includes the following steps: S1: Obtain a 2D grayscale image of the scene; S2: Based on the image grayscale difference, the edge contour recognition algorithm is used to extract the edge contour of the target from the two-dimensional grayscale image, obtain the set of point cloud coordinates around the edge contour, and at the same time record the scanning phase angle of the optical phased array corresponding to the point to be measured in the point cloud. S3: Based on the scanning phase angle, the coordinates of each point to be measured in the point cloud are mapped 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; S4: According to the set of control parameters, control the optical phased array lidar to scan each edge contour sequentially to generate point cloud data.

3. The edge contour-based scanning method according to claim 2, characterized in that, Step S2 includes: performing digital image processing on the two-dimensional grayscale image, extracting the edge contour of the target based on the grayscale difference between pixels using an edge contour detection algorithm, and obtaining a set of point cloud coordinates around the edge contour.

4. The edge contour-based scanning method according to claim 3, characterized in that, The edge contour detection algorithm is implemented by comparing the grayscale difference between pixels with a preset threshold and extracting points with a grayscale difference greater than the threshold to form a contour.

5. The edge contour-based scanning method according to claim 3, characterized in that, The point cloud coordinate set is generated using either a geometric offset method based on normal vectors or a dilation method based on image morphology.

6. The edge contour-based scanning method according to claim 2, characterized in that, The pre-set scan lookup table in step S3 includes the following steps: The optical phased array lidar is driven to scan within the global field of view, and the lateral angle of each scanning phase angle and the corresponding driving voltage value are recorded to establish a lateral scan lookup table. Record the longitudinal angle of each scanning phase angle and the corresponding laser emission wavelength value, and establish a longitudinal scanning lookup table; Based on the coordinates of each test point, the driving voltage is obtained from the horizontal scan lookup table, and the laser wavelength is obtained from the vertical scan lookup table.

7. The edge contour-based scanning method according to claim 2, characterized in that, In step S2, the point cloud coordinate set is evenly distributed in the form of a dot matrix around the edge contour.

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