Positioning method, device, equipment and medium based on laser spot profile characteristics

Abstract

The present invention discloses a positioning method, device, equipment and medium based on the contour feature of a laser spot, including inputting a laser spot image; performing binary segmentation on the laser spot image to extract the spot contour of the laser spot; taking each point on the spot contour as a contour feature point of the laser spot, estimating the position sub-pixel coordinates of each contour feature point; and determining the final positioning point coordinates of the laser spot based on the position sub-pixel coordinates of all contour feature points. The present invention utilizes the contour feature of the laser spot image to achieve spot positioning with sub-pixel accuracy and effectively improves the stability of the spot positioning point. The present invention has a more stable and robust laser spot positioning point extraction capability than centroid and centroid extraction, and is expected to effectively improve the closed-loop control accuracy of the beam pointing control system based on image positioning point coordinate feedback, which is of great significance and engineering value for achieving high-precision and high-stability pointing control of the laser beam.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of image processing and light beam control, and in particular to a positioning method, device, equipment and medium based on laser spot profile characteristics. Background Art

[0002] Extracting positioning points with high stability and high robustness for laser spot image is a necessary condition for high stability closed-loop control of laser beam.

[0003] In beam control technology, the residual between the light spot positioning point and the theoretical closed-loop point is often used to control the stable pointing of the light beam in real time. The control goal is generally to make the light spot positioning point coincide with the theoretical closed-loop point stably. Commonly used light spot positioning points are mostly the centroid or centroid of the light spot. For an ideal light spot, both of these positioning point extraction methods can obtain relatively stable positioning point coordinates, and the algorithm implementation is relatively simple. However, when the light spot morphology is not ideal and randomly distorted over time, using the light spot centroid or centroid as the light spot positioning point will cause a large positioning point position jitter, thereby increasing the control error of the beam pointing and causing the beam optical axis to jitter.

[0004] In fact, it is much more difficult to extract highly stable and robust positioning points from laser spot images than from ordinary extended target images. This is because the grayscale value jump between adjacent pixels in laser spot images is small, making it difficult to extract feature points such as gradients or corners. Therefore, when extracting positioning points from laser spot images, the available feature points or positioning point extraction methods are very limited. Especially for light spots with random distortion, the existing positioning point extraction methods based on centroid or centroid can no longer meet the needs of high-precision and high-stability beam control.

[0005] In summary, there is an urgent need for a solution to extract highly stable and robust positioning points from laser spot images. Summary of the invention

[0006] In view of the technical problems existing in the prior art, the present invention provides a positioning method, device, equipment and medium based on the laser spot profile feature. The present invention can perform highly stable and robust positioning for distorted laser spot images, and the extracted spot positioning point can be used as a stable parameter for closed-loop control of beam pointing.

[0007] In order to solve the above problems, the technical solution of the present invention is as follows:

[0008] On the one hand, the present invention provides a positioning method based on laser spot profile features, comprising:

[0009] Input laser spot image;

[0010] Binarization segmentation is performed on the laser spot image to obtain a spot binary image of the laser spot image, and a spot contour of the laser spot is extracted based on the spot binary image;

[0011] Each point on the spot contour is taken as a contour feature point of the laser spot, and the sub-pixel coordinates of the position of each contour feature point are estimated;

[0012] Based on the sub-pixel coordinates of all contour feature points, the final positioning point coordinates of the laser spot are determined.

[0013] On the one hand, a positioning device based on laser spot profile features is provided, comprising:

[0014] The first module is used to input the laser spot image;

[0015] The second module is used to perform binary segmentation on the laser spot image to obtain a spot binary image of the laser spot image, and extract the spot contour of the laser spot based on the spot binary image;

[0016] The third module is used to take each point on the spot contour as a contour feature point of the laser spot and estimate the sub-pixel coordinates of the position of each contour feature point;

[0017] The fourth module is used to determine the final positioning point coordinates of the laser spot based on the sub-pixel coordinates of all contour feature points.

[0018] On the other hand, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above-mentioned positioning method based on the laser spot profile feature when executing the computer program.

[0019] On the other hand, a computer-readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the above-mentioned positioning method based on the laser spot profile feature are implemented.

[0020] Compared with the prior art, the technical effects of the present invention are as follows:

[0021] For laser spot images with random distortion, a positioning method based on laser spot profile features provided by the present invention can achieve spot positioning point extraction that is more stable and robust than centroid and center of mass extraction, which is of great significance for improving the closed-loop control accuracy of the laser beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0023] Figure 1 It is a flow chart of a positioning method based on laser spot profile features provided by an embodiment;

[0024] Figure 2 It is an original laser spot image and contour extraction effect diagram in one embodiment;

[0025] Figure 3 Schematic diagram of anchor node distribution and positioning points in a laser spot image in one embodiment, wherein (a) is a schematic diagram of anchor node distribution in the field of view of the laser spot image; (b) is a schematic diagram of positioning points obtained by using the method of the present invention;

[0026] Figure 4 1 is a graph comparing coordinate value curves of the positioning points extracted by the centroid, the centroid and the method of the present invention in one embodiment, wherein (a) is a graph comparing the X coordinate value curves of the positioning points extracted by the centroid, the centroid and the method of the present invention, and (b) is a graph comparing the Y coordinate value curves of the positioning points extracted by the centroid, the centroid and the method of the present invention;

[0027] Figure 5 This is a comparison diagram of RMS curves of the positioning points extracted by the centroid, the centroid and the method of the present invention in different light emission time periods in an embodiment.

[0028] The present invention will be further described in detail below with reference to the accompanying drawings. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention more clearly understood, the following will be used to clearly illustrate the spirit of the content disclosed by the present invention with the accompanying drawings and detailed descriptions. After understanding the embodiments of the content of the present invention, any person skilled in the art can change and modify the technology taught by the content of the present invention without departing from the spirit and scope of the content of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0030] The present invention utilizes the contour features of the laser spot image to achieve spot positioning with sub-pixel accuracy and effectively improve the stability of the spot positioning point. The positioning method based on the laser spot contour features proposed in the present invention has a more stable and robust laser spot positioning point extraction capability than the centroid and centroid extraction, and is expected to effectively improve the closed-loop control accuracy of the beam pointing control system based on the image positioning point coordinate feedback, which is of great significance and engineering value for achieving high-precision and high-stability pointing control of the laser beam.

[0031] Reference Figure 1 , an embodiment provides a positioning method based on laser spot profile features, comprising:

[0032] Input laser spot image;

[0033] Binarization segmentation is performed on the laser spot image to obtain a spot binary image of the laser spot image, and a spot contour of the laser spot is extracted based on the spot binary image;

[0034] Each point on the spot contour is taken as a contour feature point of the laser spot, and the sub-pixel coordinates of the position of each contour feature point are estimated;

[0035] Based on the sub-pixel coordinates of all contour feature points, the final positioning point coordinates of the laser spot are determined.

[0036] The input laser spot image is segmented into two values ​​to remove the interference of background noise in the spot image. In order to combat the random fluctuation of the brightness of the distorted spot, the adaptive threshold image segmentation method is used to segment the spot image into two values.

[0037] In a preferred embodiment, the maximum between-class variance method (OTSU) is used to perform binary segmentation on the laser spot image. The maximum between-class variance method performs statistical classification on the grayscale histogram of the spot image and uses the grayscale value when the between-class variance is the largest as the segmentation threshold to binarize the image. Since the OTSU method performs adaptive threshold calculation on each spot image, it has better image segmentation effect and image adaptability.

[0038] After obtaining the binary image of the laser spot image, the Sobel edge detection operator is used to perform edge detection to obtain the contour of the laser spot. Figure 2 , is an original laser spot image and contour extraction effect diagram in an embodiment, the spot diameter is about 15 to 17 pixels. Among them, the first line is the spot grayscale image of the same laser beam at different times, the second line is the binary segmentation result of the spot image using the maximum inter-class variance method. The third line is the result of extracting the above spot contour using the Sobel edge detection operator. Figure 2It can be seen that the spot shape is obviously not an ideal spot, and the spot shape at different times is obviously distorted. This indicates that there are relatively serious random disturbances in the laser light source or laser transmission optical path, which will seriously reduce the stability and robustness of traditional spot positioning point extraction methods such as centroid and centroid.

[0039] The contour of the laser spot is a closed curve formed by the pixel points at the edge of the spot, which essentially represents the morphological characteristics of the spot. In the present invention, each point on the spot contour is a contour feature point, which is used to calculate the spot positioning point.

[0040] In one embodiment, based on the sub-pixel coordinates of all contour feature points, the final positioning point coordinates of the laser spot are determined, and the method includes:

[0041] The anchor node coordinates are set in the entire laser spot image field of view. The anchor nodes are arranged in a uniform square matrix. The distances between adjacent anchor nodes are equal. The anchor node coordinates are all known, and each contour feature point on the spot contour is used as a node to be estimated.

[0042] When the distance d from the anchor node to the current node to be estimated is less than the set threshold D, the anchor node is considered to be connected to the current node to be estimated, and the positioning weight of the anchor node is 1 / d;

[0043] The estimated sub-pixel coordinates of each contour feature point are the weighted centroids of all anchor nodes connected to it, as shown in formula (1) and formula (2):

[0044]

[0045]

[0046] Among them, (X m ,Y m ) is the precise estimated coordinate of the mth node to be estimated, m = 1, 2, ..., M, M is the total number of feature points of the spot profile, (X n ,Y n ) is the coordinate of the nth anchor node connected to the node to be estimated, w n is the weight value of the nth anchor node. Obviously, the position coordinate estimation result of each contour feature point obtained by the above method is sub-pixel level.

[0047] The spacing between adjacent anchor nodes is determined according to the actual size of the laser spot. The larger the laser spot size, the larger the spacing between adjacent anchor nodes. The threshold D is set to more than twice the spacing between adjacent anchor nodes to ensure the number of anchor nodes.

[0048] After estimating the sub-pixel accurate position coordinates of all contour feature points of the spot, the final positioning point coordinates (X core ,Y core )as follows:

[0049]

[0050]

[0051] Among them, (X m ,Y m ) is the precise estimated coordinate of the mth node to be estimated, m = 1, 2, ..., M, and M is the total number of feature points of the spot profile.

[0052] To illustrate the effectiveness of the positioning method based on the laser spot profile feature provided by the present invention, refer to Figure 2 , is an original laser spot image and contour extraction effect diagram in an embodiment, the spot diameter is about 15 to 17 pixels. Among them, the first line is the spot grayscale image of the same laser beam at different times, the second line is the binary segmentation result of the spot image using the maximum inter-class variance method. The third line is the result of extracting the above spot contour using the Sobel edge detection operator. Figure 3 Schematic diagram of anchor node distribution and positioning points in the laser spot image, wherein (a) is a schematic diagram of anchor node distribution in the field of view of the laser spot image; (b) is a schematic diagram of positioning points obtained by using the method of the present invention; Figure 3 In (a), the red dots give the coordinates of the anchor nodes. The distance between adjacent anchor nodes is 4 pixels, and the anchor nodes are arranged in a uniform square matrix. The white curve is the outline of the light spot. Each point on the outline curve is a contour feature point, and RSSI is required for accurate position estimation. The yellow dot represents one of the contour feature points on the light spot contour. All anchor nodes within the circle with this point as the center and the distance threshold d as the radius are the connected anchor nodes of the contour feature point. For each contour feature point, based on the pre-set distance threshold, determine which anchor nodes are connected to it, so as to accurately estimate the position coordinates of the contour feature point based on these anchor nodes. Finally, the average of the precise position coordinates of these contour feature points after optimization is used as the positioning point of the entire light spot. Figure 3 In (b), the red dot is the final positioning point of the entire light spot.

[0053] Figure 4The present invention is a graph comparing coordinate value curves of the positioning points extracted by the centroid, centroid and the method of the present invention respectively based on 1300 frames of continuous laser spot images in one embodiment, wherein (a) is a graph comparing the X coordinate value curves of the positioning points extracted by the centroid, centroid and the method of the present invention respectively, and (b) is a graph comparing the Y coordinate value curves of the positioning points extracted by the centroid, centroid and the method of the present invention respectively; the three positioning point extraction methods all use the maximum inter-class variance method to perform binary segmentation on the spot image. Figure 4 In the figure, the blue curve is the coordinates of the positioning points using the centroid extraction method, the green curve is the coordinates of the positioning points using the centroid extraction method, and the red curve is the coordinates of the positioning points using the extraction method of the present invention. Figure 4 The coordinate fluctuation of the positioning point extracted by the method of the present invention is the smallest, which indicates that the stability of the light spot positioning point extracted by the method of the present invention is higher.

[0054] Further quantitative evaluation using RMS value Figure 4 The results are shown, and the RMS definition is shown in the following formula.

[0055]

[0056] In the above formula, N is the amount of data in the data set, S i is the i-th data in the data set, and μ is the mean of the data set. Figure 4 Data, in the X direction, the RMS of the centroid, centroid and the positioning point extracted by the method of the present invention are 0.4085, 0.4060 and 0.3643 respectively, in the Y direction, the RMS of the three methods are 0.4155, 0.4119 and 0.3360 respectively, and the root mean square value of the RMS of the three methods is 0.5827, 0.5784 and 0.4956 respectively. Obviously, the positioning point extracted by the method of the present invention has the smallest RMS value, while the RMS values ​​of the centroid and centroid positioning points are very different.

[0057] Figure 5 This is a comparison diagram of the RMS curves of the centroid, the centroid and the method of the present invention for extracting the positioning points in different light-emitting time periods during a light-emitting process in an embodiment, and the sampling frequency is 60 frames / second. Figure 5 , As the light emission time increases, the number of spot image frames increases accordingly, and the RMS of the centroid, centroid and the positioning points extracted by the method of the present invention all show a downward trend, which shows that the positioning point accuracy of the above three light spot positioning methods is affected by the change of the light spot's own characteristics, and the trend is consistent. However, the RMS of the positioning points of the method of the present invention in all time periods is always smaller than the centroid and centroid positioning points, which shows that the method of the present invention has better stability and robustness throughout the light emission time. At the same time, the RMS curves of the centroid and centroid positioning points are almost overlapped, which shows that the actual difference between the two is very small.

[0058] In another embodiment, a positioning device based on laser spot profile features is provided, comprising:

[0059] The first module is used to input the laser spot image;

[0060] The second module is used to perform binary segmentation on the laser spot image to obtain a spot binary image of the laser spot image, and extract the spot contour of the laser spot based on the spot binary image;

[0061] The third module is used to take each point on the spot contour as a contour feature point of the laser spot and estimate the sub-pixel coordinates of the position of each contour feature point;

[0062] The fourth module is used to determine the final positioning point coordinates of the laser spot based on the sub-pixel coordinates of all contour feature points.

[0063] The implementation method of each of the above modules can adopt the method described in any of the above embodiments, which will not be repeated here.

[0064] On the other hand, the present invention provides a computer device, including a memory and a processor, the memory stores a computer program, and the processor implements the steps of the positioning method based on the laser spot profile feature provided in any of the above embodiments when executing the computer program. The computer device can be a server. The computer device includes a processor, a memory, a network interface and a database connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store sample data. The network interface of the computer device is used to communicate with an external terminal through a network connection.

[0065] On the other hand, the present invention provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the steps of the positioning method based on the laser spot profile feature provided in any of the above embodiments are implemented.

[0066] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0067] Matters not covered by the present invention are known technologies.

[0068] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A positioning method based on laser spot profile features, characterized in that: include: Input laser spot image; Binarization segmentation is performed on the laser spot image to obtain a spot binary image of the laser spot image, and a spot contour of the laser spot is extracted based on the spot binary image; Each point on the spot contour is taken as a contour feature point of the laser spot, and the sub-pixel coordinates of the position of each contour feature point are estimated, including: Anchor node coordinates are set in the field of view of the laser spot image. The coordinates of the anchor nodes are known, and each contour feature point on the spot contour is used as a node to be estimated. When the distance from the anchor node to the current node to be estimated d Less than the set threshold D , it is considered that the anchor node is connected to the current node to be estimated, and the positioning weight of the anchor node is 1 / d , where the threshold D is set to be more than twice the distance between adjacent anchor nodes; The estimated sub-pixel coordinates of each contour feature point are the weighted centroids of all anchor nodes connected to it, as shown in formula (1) and formula (2): （1） （2） in, For the m The precise estimated coordinates of the nodes to be estimated, m= 1,2 ,...,M , M is the total number of feature points of the spot profile, is the first node connected to the node to be estimated n Anchor node coordinates, For the n The weight value of the anchor node; Based on the sub-pixel coordinates of all contour feature points, the final positioning point coordinates of the laser spot are determined.

2. The positioning method based on the laser spot profile feature according to claim 1 is characterized in that: The laser spot image is binarized using an adaptive threshold image segmentation method.

3. The positioning method based on the laser spot profile feature according to claim 1 is characterized in that: The maximum inter-class variance method is used to perform binary segmentation on the laser spot image.

4. The positioning method based on the laser spot profile feature according to claim 1, 2 or 3, characterized in that: The Sobel edge detection operator is used to perform edge detection on the spot binary image and extract the spot contour of the laser spot.

5. The positioning method based on the laser spot profile feature according to claim 4 is characterized in that: The spacing between adjacent anchor nodes is determined according to the actual size of the laser spot. The larger the laser spot size, the larger the spacing between adjacent anchor nodes.

6. The positioning method based on the laser spot profile feature according to claim 1, 2, 3 or 5, characterized in that: Final positioning point coordinates of the laser spot as follows: （3） （4） in, For the m The precise estimated coordinates of the nodes to be estimated, m= 1,2 ,...,M , M is the total number of feature points of the spot profile.

7. A positioning device based on the laser spot profile feature, characterized in that: include: The first module is used to input the laser spot image; The second module is used to perform binary segmentation on the laser spot image to obtain a spot binary image of the laser spot image, and extract the spot contour of the laser spot based on the spot binary image; The third module is used to take each point on the spot contour as a contour feature point of the laser spot and estimate the sub-pixel coordinates of the position of each contour feature point, including: Anchor node coordinates are set in the field of view of the laser spot image. The coordinates of the anchor nodes are known, and each contour feature point on the spot contour is used as a node to be estimated. When the distance from the anchor node to the current node to be estimated d Less than the set threshold D , it is considered that the anchor node is connected to the current node to be estimated, and the positioning weight of the anchor node is 1 / d , where the threshold D is set to be more than twice the distance between adjacent anchor nodes; The estimated sub-pixel coordinates of each contour feature point are the weighted centroids of all anchor nodes connected to it, as shown in formula (1) and formula (2): （1） （2） in, For the m The precise estimated coordinates of the nodes to be estimated, m= 1,2 ,...,M , M is the total number of feature points of the spot profile, is the first node connected to the node to be estimated n Anchor node coordinates, For the n The weight value of the anchor node; The fourth module is used to determine the final positioning point coordinates of the laser spot based on the sub-pixel coordinates of all contour feature points.

8. The positioning device based on the laser spot profile feature according to claim 7, characterized in that: Final positioning point coordinates of the laser spot as follows: （3） （4） in, For the m The precise estimated coordinates of the nodes to be estimated, m= 1,2 ,...,M , M is the total number of feature points of the spot profile.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the positioning method based on the laser spot profile feature of claim 1 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the positioning method based on the laser spot profile feature of claim 1 are implemented.

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