A method and system for determining the position of a laser point on a two-dimensional plane

Abstract

The present invention provides a method and system for determining the position of a laser point on a two-dimensional plane, the method comprising: obtaining the number of laser lines that can be hit on a calibration plate; obtaining the laser line segments and corresponding laser intensity curves obtained when each laser line hits the calibration plate; finding the numbers of two laser lines located at the boundary of the colored area of ​​the calibration plate according to the laser intensity curve; finding the corresponding grayscale values ​​on the calibration plate based on the laser intensity values ​​of the two laser lines located at the boundary of the calibration plate, and determining the absolute longitudinal positions of the two laser lines hitting the calibration plate based on the grayscale values. By designing a special calibration plate, the present invention can directly examine the relationship between the reflected laser intensity of the laser radar and the grayscale value of the calibration plate plane, thereby determining the position of the laser line hitting the calibration plate, and using the laser intensity information in the laser radar to perform scene recognition and realize a series of functions.

Description

Technical Field

[0001] The present invention relates to the field of lasers, and more specifically, to a method and system for determining a laser point position on a two-dimensional plane. Background Art

[0002] 2D LiDAR is a commonly used sensor in robots, which can be used for distance measurement, obstacle avoidance, positioning, and mapping. In order to accurately use the measurement values ​​of LiDAR, it is necessary to calibrate the external parameters of LiDAR relative to the robot body to obtain the actual external parameters of LiDAR relative to the robot body, including position offset and angle offset. Among them, angle offset is the main parameter that affects the use of LiDAR, because when LiDAR measures obstacles at a long distance, a small angle offset error will be amplified into a larger distance offset, which will cause the robot to make incorrect algorithm decisions.

[0003] The existing methods for calibrating the external parameters of 2D LiDAR mainly calibrate the laser and camera together, which is not only computationally intensive, but also has high requirements on the hardware of the sensor and the software of the sensor clock synchronization, and it is impossible to obtain the external parameter relationship between the LiDAR and the encoder. In order to simplify the calibration of the laser external parameters and quickly obtain the angle offset of the LiDAR relative to the robot encoder, a simple angle offset calibration technology is designed to avoid some of the shortcomings of the above traditional calibration methods. This calibration method relies on determining the absolute position of the laser line on the two-dimensional calibration plate plane, so a method for matching one-dimensional line segments on the two-dimensional code plane is designed, which is called the line pattern matching method. Summary of the invention

[0004] The present invention aims at solving the technical problems existing in the prior art and provides a method and system for determining the position of a laser point on a two-dimensional plane.

[0005] According to a first aspect of the present invention, a method for determining the position of a laser point on a two-dimensional plane is provided, comprising: obtaining the number of the laser line hitting the calibration plate according to the distance information of each laser line and the plane equation obtained according to the plane characteristics of the calibration plate; obtaining the laser line segment and the corresponding laser intensity curve obtained when each laser line hits the calibration plate, wherein the laser intensity on the laser intensity curve has a corresponding relationship with the grayscale value on the calibration plate; finding the numbers of two laser lines located at the boundary of the colored area of ​​the calibration plate according to the laser intensity curve; finding the corresponding grayscale value on the calibration plate based on the laser intensity values ​​of the two laser lines located at the boundary of the calibration plate, and determining the absolute longitudinal position of the two laser lines hitting the calibration plate based on the grayscale value; the calibration plate comprises a colored area and a colorless area, the colored area comprises a plurality of alternating dark areas and light areas in the width direction of the calibration plate, the widths of different dark areas and different light areas are different, and the depth value of the same area is different in the height direction.

[0006] According to a second aspect of the present invention, a system for determining the position of a laser point on a two-dimensional plane is provided, comprising: a first acquisition module, for acquiring the number of the laser line hitting the calibration plate according to the distance information of each laser line and the plane equation obtained according to the plane characteristics of the calibration plate; a second acquisition module, for acquiring the laser line segment and the corresponding laser intensity curve obtained by each laser line hitting the calibration plate, wherein the laser intensity on the laser intensity curve has a corresponding relationship with the grayscale value on the calibration plate; a search module, for finding the numbers of two laser lines located at the boundary of the colored area of ​​the calibration plate according to the laser intensity curve; a determination module, for finding the corresponding grayscale value on the calibration plate based on the laser intensity values ​​of the two laser lines located at the boundary of the calibration plate, and determining the longitudinal absolute position of the two laser lines hitting the calibration plate based on the grayscale value; the calibration plate comprises a colored area and a colorless area, the colored area comprises a plurality of alternating dark areas and light areas in the width direction of the calibration plate, the widths of different dark areas and different light areas are different, and the depth value of the same area is different in the height direction.

[0007] The present invention provides a method and system for determining the position of a laser point on a two-dimensional plane. By designing a special calibration plate, the relationship between the reflected laser intensity of the laser radar and the grayscale value of the calibration plate plane can be directly examined, and the position of the laser line hitting the calibration plate can be determined. The laser intensity information in the laser radar is used for scene recognition to achieve a series of functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 A flow chart of a method for determining the position of a laser point on a two-dimensional plane provided by the present invention;

[0009] Figure 2 A schematic diagram of a calibration plate designed for an embodiment of the present invention;

[0010] Figure 3 A schematic diagram of a laser line segment formed by a laser line hitting a calibration plate;

[0011] Figure 4 It is a schematic diagram of the laser intensity curve corresponding to the laser line segment;

[0012] Figure 5 It is a schematic diagram of the corresponding matching of the calibration plate, laser line segment and laser intensity curve;

[0013] Figure 6 Schematic diagram for solving the lateral coordinates of all laser points in the colored area of ​​the calibration plate;

[0014] Figure 7 A schematic structural diagram of a system for determining the position of a laser point on a two-dimensional plane provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0015] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0016] The measurement information of 2D laser radar includes distance information and reflected laser intensity information. At present, the use of laser radar is to use the distance information of laser radar for ranging, obstacle avoidance, positioning and mapping functions, and there is little research on using the reflected laser intensity to achieve functions. For 2D laser radar, the position of the laser line hitting the calibration plate cannot be determined by distance information alone, and point cloud information is difficult to use. Therefore, a special calibration plate is designed. Combined with the laser intensity information, the absolute position of the laser line hitting the calibration plate can be determined.

[0017] Line pattern matching is a matching method. By hitting a special calibration plate, a certain pattern of laser line intensity can be obtained. Furthermore, the reflectivity change of the target area can be judged by the laser intensity pattern. This technology can be used for loop detection of visual SLAM. When the robot returns to an area with extremely similar reflectivity, it can be judged that it has returned to a passing point, and then the positioning of the robot can be corrected, eliminating the cumulative positioning error, and significantly improving the positioning accuracy of positioning technologies such as hector-SLAM that do not have a loop detection link; while judging the reflectivity of the target area, it can be used to segment different reflective areas in the scene, such as glass and walls, to segment and identify the target area and build a semantic map.

[0018] Before explaining the method provided by the embodiment of the present invention in detail, some basic concepts are explained. First, the line segment information to be matched is explained. Here, only the 2D laser radar is considered. A single laser line hits the calibration plate. Because of the reflection of the calibration plate, the laser receiver will receive a laser echo coherent with the output laser line. According to the Lambert body reflection hypothesis, the laser line will have a laser echo in any direction outside the plane from the target position on the calibration plate. Therefore, the fastest laser light path returning to the laser receiver is the original return path. The laser is used to measure distance based on this principle. After the laser line returns, it can be considered that the end of the output laser line is terminated on the plane of the calibration plate to form a laser point.

[0019] When a single laser line rotates rapidly around the Z axis of the laser coordinate system, the single laser line will form a laser surface, and the laser point will form a straight line. The part of the straight line on the calibration plate can be considered as a line segment. Because the laser line itself is also an electromagnetic wave, calibration plates of different colors have different absorption and reflection coefficients for the laser line, so that the same laser can get different laser intensities when it hits calibration plates of different colors at the same distance.

[0020] The laser itself is a 2D single-line laser, which rotates rapidly around the Z axis of the laser coordinate system for scanning. The plane formed by the laser line is exactly the XOY plane of the laser coordinate system, and the Y axis of the laser line is the center line of the laser line. Because the laser line scans very quickly, the laser line is viewed as a static multi-line laser line. Each laser line has a corresponding laser line number, laser line distance information, and laser line intensity information. The center line of the laser line is numbered 0.

[0021] See also Figure 1 , is a flow chart of a method for determining the position of a laser point on a two-dimensional plane provided by the present invention, such as Figure 1 As shown, the method includes: S1, obtaining the laser line number on the calibration plate according to the distance information of each laser line and the plane equation obtained according to the plane characteristics of the calibration plate.

[0022] It is understandable that when a single laser line quickly rotates around the Z axis of the laser coordinate system, the single laser line will form a laser surface, and the laser point will form a straight line. The part of the straight line on the calibration board can be considered as a line segment. It should be noted here that not every laser line can hit the calibration board. This step S1 is to find the laser lines that can hit the calibration board. When calculating the position of the laser points on the calibration board, it is only necessary to calculate the positions of the corresponding laser points on the calibration board of the laser lines that can hit the calibration board.

[0023] In this step S1, the number of the laser line on the calibration plate is obtained according to the distance information of each laser line and the plane equation of the calibration plate.

[0024] Among them, the method for determining the number of the laser line hitting the calibration plate is: according to the number of each laser line and the corresponding laser distance information, calculate the coordinates of the point where each laser line hits the calibration plate in the laser coordinate system; according to the transformation matrix of the laser coordinate system and the calibration plate coordinate system, convert the coordinates of the point where each laser line hits the calibration plate in the laser coordinate system into the position in the calibration plate coordinate system; based on the laser point hitting the calibration plate satisfying the plane constraint, establish a plane constraint equation, the plane constraint equation characterizes the relationship between the transformation matrix, the laser line number and the laser distance information; based on the specific numbers of multiple laser lines and the corresponding laser distance information, solve the plane constraint equation; substitute the number of each laser line and the corresponding laser distance information into the solved plane constraint equation for verification, and obtain the number of the laser line that can be hit on the calibration plate.

[0025] The specific implementation method is to set the angle resolution of the laser line to θ0, and the distance information of the laser line numbered Id=n (n=-504~504, assuming that the total number of laser lines is 1081) is d n, then the angle between the laser line and the center line of the laser line in the laser line coordinate system is nθ0. Since the center line of the laser line is the Y axis of the laser line coordinate system, the coordinate of the point where the laser line with Id=n hits the calibration plate in the laser coordinate system is p n_laser =(d n sin(nθ0),d n cos(nθ0),0).

[0026] Let the transformation matrix between the laser coordinate system and the calibration plate coordinate system be T target_laser , then the position of the point at the end of the laser line in the laser coordinate system in the calibration plate coordinate system is T target_laser p n_laser , let p n_target =T target_ laser p n_laser .

[0027] Let the transformation matrix

[0028] t target_laser =[t1 t2 t3],

[0029]

[0030]

[0031] Among them, because the laser point on the calibration plate must satisfy the plane constraint at this time, p n_target The coordinate axis in the Z-axis direction must be 0, so the plane constraint equation can be established:

[0032] p n_target =R 31 d n sin(nθ0)+R 32 d n cos(nθ0)+t3=0.

[0033] Because the calibration plate is large in size, the yaw angle deviation of the laser line will not be too large. Here, it can be ensured that the laser lines numbered -1, 0, and 1 are located on the plane of the calibration plate. Substituting the above plane constraint equation into the equation, we get:

[0034]

[0035] Solving the above equations, we can get R 31 , R 32 , about d0,d1,d -1 ,θ0, because d0,d1,d-1 ,θ0 are known quantities in the single frame laser data, so the current R 31 ,R 32 ,t3, then the plane equation is known. After the plane constraint equation is solved, the number of each laser line and the corresponding distance information are substituted into the plane constraint equation for verification. When the plane constraint equation is satisfied, it means that the laser line can be hit on the calibration board. Find out the numbers of all laser lines that can be hit on the calibration board.

[0036] It is understandable that the design of the calibration plate is very important for line pattern matching. According to the Lambert body reflection hypothesis,

[0037]

[0038] Among them, I rec Represents the reflected laser intensity, P rec represents the reflected laser power, It indicates the surface reflectivity, α indicates the incident angle, and r indicates the laser measurement distance. It can be seen that the laser intensity is linearly related to the material surface reflectivity. Considering that only the grayscale value is different on the calibration plate plane, the black area has a higher absorption rate for the laser and a lower reflected laser intensity. Correspondingly, the white area has the lowest absorption rate for the laser and the laser intensity received by the laser is the highest. The gray area is between the two. Therefore, the relative size of the grayscale values ​​of two adjacent laser point positions can be determined by the relative laser intensity information of adjacent laser lines.

[0039] Before performing laser line intensity matching, the design principle of the calibration plate is explained first, wherein the designed calibration plate includes a colored area and a colorless area, wherein the colored area includes a plurality of alternating dark areas and light areas in the width direction of the calibration plate, wherein the widths of different dark areas and different light areas are different, and the depth values ​​of the same area are different in the height direction. The grayscale value of the deep area on the calibration plate is greater than the depth value of the light area, and the grayscale value of the same dark area or the same light area in the height direction changes in a step-by-step unidirectional manner, and the grayscale value difference between different areas is significantly greater than the grayscale value difference within the area, the middle of the calibration plate is the light area with the largest width, and the colorless area is located at the two end edges of the calibration plate.

[0040] For details, see Figure 2 , Figure 2 For the designed calibration plate, Figure 2As shown in , the calibration plate is symmetrical on the left and right, and asymmetrical on the top and bottom. It can be divided into colored areas and colorless areas according to the grayscale value (pure white represents colorless areas, black and gray represent colored areas), and the colored areas are roughly divided into dark areas and light areas. Let the height of the colored area be H and the width be L. The width of the dark area from the outside to the inside in the width direction of the calibration plate is 1, 2*1, and 3*1 respectively. Each dark area and each light area are equally divided into multiple sub-areas in the height direction of the calibration plate, and the grayscale value of each sub-area is different. The grayscale value of the light area gradually decreases from bottom to top, and the grayscale value of the dark area gradually increases from bottom to top. Different dark areas or different light areas have the same grayscale value at the same height. The color of the dark area is pure black to gray, and the color of the light area is gray to light gray. In the embodiment of the present invention, the grayscale value of the dark area is designed to change to 0, 20, 40, 60, 80, 100, and the grayscale value of the light area is changed to 155, 175, 195, 215, 235, 255.

[0041] Among them, a few points need to be explained:

[0042] ① The design that the grayscale value difference between regions is significantly greater than the grayscale value difference within the region is to be able to quickly segment a single region and then determine the absolute value of the slope of the laser line segment.

[0043] ② The design of unidirectional change of gray value in the area is to determine the positive and negative sign of the slope of the laser line segment. At the same time, the gray value step can be used to determine the absolute horizontal position of the laser line currently located at the step position.

[0044] ③The design with the largest width in the middle area is to quickly determine the area where the center line of the laser line is located.

[0045] ④ The pure white area on the calibration plate is used to determine the maximum reflected laser intensity, and then directly determine the laser line number at the edge of the colored area.

[0046] ⑤ The grayscale value steps in the longitudinal direction of the entire calibration plate are used to determine the absolute longitudinal position of the laser line segment and to make the calculated roll angle of the laser coordinate system as close to the actual roll angle as possible.

[0047] ⑥Because the 180° roll angle symmetry of the laser is not considered here, the calibration plate is designed to be bilaterally symmetrical.

[0048] S2, obtaining a laser line segment and a corresponding laser intensity curve obtained by each laser line hitting the calibration plate, wherein the laser intensity on the laser intensity curve has a corresponding relationship with the grayscale value on the calibration plate.

[0049] A special calibration board is designed. When multiple laser lines hit the calibration board, laser line segments are formed on the calibration board. Assuming that the incident angle and distance value of the laser line are exactly the same, and only the grayscale value of the target area is different, a laser line segment is obtained by scanning on the calibration board. The laser line segment formed on the calibration board is as follows: Figure 3 As shown in FIG. 1 , since the grayscale values ​​at different positions on the calibration plate are different, the laser intensities of the laser points at different positions on the calibration plate are different. The laser intensity curve corresponding to the laser line segment is shown in FIG. Figure 4 shown.

[0050] The schematic diagram of putting the laser line segment, laser intensity curve and calibration plate together is as follows: Figure 5 As shown by Figure 5 It can be seen that the laser intensity step from left to right on the laser intensity curve is an upward trend in the light-colored area and a downward trend in the dark-colored area, so the slope of the laser line on the calibration plate must be positive. Examining the low area in the laser intensity curve alone, it can be seen that the laser reflection intensity has five step decreases in the whole process, so we can conclude that the laser line segment extends from the darkest part of the low area to the brightest part of the low area. Similarly, the high area of ​​the laser intensity also has five step increases, so it also extends from the darkest part of the high area to the brightest part of the high area. And in the process, we can determine the corresponding grayscale value of each interval of the laser line segment.

[0051] S3, according to the laser intensity curve, find the numbers of the two laser lines located at the boundary of the colored area of ​​the calibration plate.

[0052] It can be understood that in the above step S2, the laser line segments and corresponding laser intensity curves of the laser lines hitting the calibration plate are obtained. The boundaries of each area on the calibration plate can be identified from the laser intensity curve, and then the numbers of the two laser lines located at the boundaries of the colored areas of the calibration plate can be found.

[0053] Specifically, the above step S1 obtains the number of the laser line that can be hit on the calibration plate. In order to obtain the number of the laser line located at the boundary of the area, this step S3 uses a sliding window to obtain the variance of the local area in the laser intensity curve. The size of the variance can be used to determine whether the current window is located in the area or between areas. For example, during the sliding of the window, when the difference in laser intensity values ​​is relatively large, it means that the sliding window spans the interval; if the difference in laser intensity is very small, it indicates that the sliding window is sliding within the interval. The size of the initial variance can be considered to use the size of the laser intensity variance in the area where the center line of the laser line is located. The width of the initial window can refer to the minimum area width l. Here, it is assumed that the area where the center line of the laser line is located is roughly in the middle of the calibration plate.

[0054] Use a large window to determine the area type in the window (dark or light area), then use a small window to determine the area features in the current window, and find the area boundary. If there is no area boundary, use the current window as a region, expand the current window, and then find the area boundary, and continue to expand the region until the area boundaries on both sides are found. Using the same method, all area boundaries can be obtained.

[0055] Among them, after identifying the boundaries of each area on the calibration plate, the slope of the laser line segment on the calibration plate can be calculated based on the light-colored area with the largest width on the calibration plate, the measured length of the laser line segment on the light-colored area and the actual design width of the light-colored area; based on the slope of the laser line segment, the length of the laser line segment in each area and the absolute lateral position of all laser lines hitting the colored area of ​​the calibration plate are calculated.

[0056] It can be understood that for different grayscale value intervals on the calibration plate, corresponding to the laser intensity curve, alternating laser intensity peaks and valleys can be seen. Because the width of the light-colored area in the middle is the largest, there must be a laser intensity peak with the largest width in the laser intensity shape. This large-width laser intensity peak can be used to roughly determine the angle information of the laser relative to the calibration plate. The slope of the straight line formed by the laser points on the calibration plate can be calculated from the ratio of the measured length of a certain area in the laser intensity shape to the actual length of the area.

[0057] Assume the laser line number is m i ,m j The two laser lines hit the two ends of the light-colored area s with the largest width. The distance between the two laser lines is d i ,d j , the angle between the two laser lines θ=(m i -m j )*θ0, let m i is the laser line with a larger number. The measured length of the laser line segment on the light-colored area is If the actual design length of the light-colored area is l s , then the slope of the straight line is k = l s ' / l s , so it is expected that the length of the laser line segment on the entire calibration plate is L'=kL.

[0058] After obtaining the slope of the laser line segment, since the proportion of each area on the laser line segment is the same as the actual design value, we can further calculate the length of all areas on the laser line segment and the horizontal coordinates of all laser points in the colored area of ​​the calibration plate. The process of solving the horizontal coordinates of all laser points in the colored area of ​​the calibration plate can be found in Figure 6 As shown, specifically, assuming that AB is numbered m iThe laser line AC is numbered m j The laser lines of m, B and C are the laser points on the calibration board hit by the two laser lines, and AD is an arbitrary number between m i ,m j The laser line between the two, assuming that the AD number is m k , the laser ranging information is d k , are all known quantities. Then the BD length can be calculated using the cosine theorem:

[0059] BD length

[0060] This theorem can be used to determine the positions of all laser lines between BDs, and then determine the lateral coordinates of the laser point.

[0061] S4, based on the laser intensity values ​​of the two laser lines located at the boundary of the calibration plate, find the corresponding grayscale value on the calibration plate, and based on the grayscale value, determine the absolute longitudinal position of the two laser lines on the calibration plate.

[0062] Among them, according to the laser intensity values ​​of the two laser lines, the corresponding grayscale value on the calibration plate is found; based on the grayscale value, the corresponding vertical absolute position is found in the dark area of ​​the position boundary.

[0063] It is understandable that in order to determine the absolute longitudinal position of the laser line segment, grayscale value steps are designed in different areas of the calibration plate, and the grayscale value change direction of the light area and the dark area is designed to be opposite, eliminating the symmetry of the upper and lower calibration plate. Because the grayscale value change direction of the light area and the dark area is opposite, this causes the step height of the laser line segment from one area to another to change.

[0064] When the total number of steps in the dark area or light area is the maximum number of steps in the area, we can directly conclude that the laser line segment extends from the bottom corner to the upper right corner or from the upper left corner to the lower right corner. When the number of steps is less than the maximum number of steps, the beginning and end intervals of the laser line segment in the colored area can be determined by the step conditions at both ends of the laser line segment. Examining two adjacent areas, we can see that from top to bottom, the heights of the grayscale value steps are 235, 195, 155, 115, 75, and 35, respectively. Therefore, the absolute position of the vertical height of the current laser line can be determined from the maximum step height at both ends of the laser line segment.

[0065] If the actual length of the laser intensity line segment is less than L', it means that one side of the laser line segment is emitted from above or below the colored area, then the longitudinal position of one side of the laser line segment can be directly determined. Because the slope of the laser line segment has been determined, the absolute position of the laser line can be directly determined (the situation where the laser roll angle is too large and the laser line segment only covers the middle light-colored area is not considered here).

[0066] By changing the height of the calibration plate and thus the height size of the grayscale steps in the area, the size of the area where the laser roll angle cannot be determined can be continuously reduced, thereby approaching the true value of the laser roll angle. The principle of laser line segment pattern matching is as above. Now we add the influence of laser line distance and incident angle.

[0067] When the laser line discussed above is emitted from a light source position, the incident angle and distance of the laser line will actually change. Assuming that the pitch angle of the laser relative to the calibration plate is 0 at this time, there must be a laser line that hits the calibration plate vertically, and the laser lines on both sides of the laser line hit the calibration plate symmetrically. The incident angle gradually increases, and the distance information can be directly calculated based on the incident angle. The calculation process is as follows:

[0068] Assume that the laser line id currently vertically projected onto the calibration board is m t , the laser line distance is d t , then the incident angle of the laser line is 0 degrees, with the laser line as the center line, id = m t -1,m t -2,m t -3,....,m t The incident angles of the laser lines of -n are θ0, 2θ0, 3θ0, ..., nθ0, and the corresponding laser line distance is d t / cos(θ0),d t / cos(2θ0),d t / cos(3θ0)...d t / cos(nθ0), similarly, id=m t +1,m t +2.....m t The incident angles of the laser lines of +n are θ0, 2θ0, 3θ0, ..., nθ0, and the distance of the laser lines is d t / cos(θ0),d t / cos(2θ0),d t / cos(3θ0)...d t / cos(nθ0), we can see that id=m t The laser line distance is the smallest and the incident angle is the smallest, so the vertically incident laser line ID can be determined by the laser line distance information. Substituting the above conclusion into the Lambert body reflection intensity formula, we can get:

[0069]

[0070] Where n represents the current laser line number, d t Laser line number m t The distance is an even function that is symmetric about n.

[0071] When the pitch angle is not 0, let the pitch angle be δ, and also assume that the laser line id currently vertically hitting the calibration board is m t , the laser line distance is d t , take the laser line as the center line, id = m t -1,m t -2,m t -3,....,m t -n The laser line distance is d t / cos(θ0),d t / cos(2θ0),d t / cos(3θ0)...d t / cos(nθ0), similarly, id=m t +1,m t +2.....m t The laser line distance of the laser line of +n is d t / cos(θ0),d t / cos(2θ0),d t / cos(3θ0)...d t / cos(nθ0), because the incident angle of the laser line is more complicated, it is not expanded here, id=m t The laser line distance is the smallest and the incident angle is the smallest. The vertical incident laser line ID can also be determined by the laser line distance information. Substituting the above conclusion into the Lambert body reflection intensity formula, we can get:

[0072]

[0073] Where n represents the current laser line number and laser line number m t Because of the symmetry of the laser line, the function is also an even function symmetric about n, and the pitch angle as a constant does not change the shape of the curve.

[0074] When the yaw angle and roll angle are not 0, only the laser line number m will be changed. t , the remaining laser line group characteristics will not change, so they are not discussed.

[0075] For single-frame laser data, we have converted the distance variable into the incident angle variable, thus reducing the number of variables that need to be examined. Because there is no coupling relationship between reflectivity and incident angle, after we obtain the actual laser intensity information, we first obtain the laser line number m through the laser line distance information. t , and then cos 3 (nθ0) is moved to the left, and the obtained laser intensity curve can be directly used for mode matching:

[0076]

[0077] Among them, d t and sin(δ) are constants for a single frame of laser data.

[0078] See also Figure 7 , a system for determining the position of a laser point on a two-dimensional plane is provided, comprising a first acquisition module 701, a second acquisition module 702, a search module 703 and a determination module 704, wherein:

[0079] The first acquisition module 701 is used to obtain the number of the laser line hitting the calibration plate according to the distance information of each laser line and the plane equation obtained according to the plane characteristics of the calibration plate; the second acquisition module 702 is used to obtain the laser line segment and the corresponding laser intensity curve obtained by each laser line hitting the calibration plate, and the laser intensity on the laser intensity curve has a corresponding relationship with the grayscale value on the calibration plate; the search module 703 is used to find the numbers of the two laser lines located at the boundary of the colored area of ​​the calibration plate according to the laser intensity curve; the determination module 704 is used to find the corresponding grayscale value on the calibration plate based on the laser intensity value of the two laser lines located at the boundary of the calibration plate, and determine the longitudinal absolute position of the two laser lines hitting the calibration plate based on the grayscale value; wherein the calibration plate includes a colored area and a colorless area, and the colored area includes a plurality of alternating dark areas and light areas in the width direction of the calibration plate, and the widths of different dark areas and different light areas are different, and the depth value of the same area is different in the height direction.

[0080] It can be understood that the system for determining the position of a laser point on a two-dimensional plane provided by the present invention corresponds to the method for determining the position of a laser point on a two-dimensional plane provided by the aforementioned embodiments. The relevant technical features of the system for determining the position of a laser point on a two-dimensional plane can refer to the relevant technical features of the method for determining the position of a laser point on a two-dimensional plane, and will not be repeated here.

[0081] The embodiment of the present invention provides a method and system for determining the position of a laser point on a two-dimensional plane. By designing a special calibration plate, the relationship between the reflected laser intensity of the laser radar and the grayscale value of the calibration plate plane can be directly examined, and then the position where the laser line hits the calibration plate can be determined. The laser intensity information in the laser radar is used for scene recognition to achieve a series of functions.

[0082] It should be noted that in the above embodiments, the description of each embodiment has its own emphasis, and for parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0083] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0084] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0085] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0086] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0087] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0088] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for determining the position of a laser point on a two-dimensional plane, characterized in that: include: According to the distance information of each laser line and the plane equation obtained according to the plane characteristics of the calibration plate, the number of the laser line on the calibration plate is obtained; Obtaining a laser line segment and a corresponding laser intensity curve obtained by each laser line hitting the calibration plate, wherein the laser intensity on the laser intensity curve has a corresponding relationship with the grayscale value on the calibration plate; According to the laser intensity curve, find the numbers of the two laser lines located at the boundary of the colored area of ​​the calibration plate; Based on the laser intensity values ​​of the two laser lines located at the boundary of the calibration plate, the corresponding grayscale values ​​on the calibration plate are found, and based on the grayscale values, the absolute longitudinal positions of the two laser lines on the calibration plate are determined; The calibration plate includes a colored area and a colorless area, the colored area includes a plurality of alternating dark areas and light areas in the width direction of the calibration plate, different dark areas and different light areas have different widths, and the depth value of the same area is different in the height direction; The method of obtaining the number of the laser line on the calibration board according to the distance information of each laser line and the plane equation obtained according to the plane characteristics of the calibration board includes: According to the number of each laser line and the corresponding laser distance information, the coordinates of the point where each laser line hits the calibration plate in the laser coordinate system are calculated; According to the transformation matrix of the laser coordinate system and the calibration plate coordinate system, the coordinates of each point where the laser line hits the calibration plate in the laser coordinate system are converted into the position in the calibration plate coordinate system; Based on the fact that the laser points on the calibration plate satisfy the plane constraint, a plane constraint equation is established, wherein the plane constraint equation represents the relationship between the transformation matrix, the laser line number and the laser distance information; Solving the plane constraint equation based on the specific numbers of the multiple laser lines and the corresponding laser distance information; Substitute the number of each laser line and the corresponding laser distance information into the solved plane constraint equation for verification, and obtain the number of the laser line that can be projected on the calibration plate.

2. The method according to claim 1, characterized in that The grayscale value of the deep area on the calibration plate is greater than the depth value of the light area. The grayscale value of the same dark area or the same light area in the height direction changes in a step-by-step unidirectional manner. The difference in grayscale value between different areas is significantly greater than the difference in grayscale value within the area. The middle of the calibration plate is the light-colored area with the largest width, and the colorless area is located at the two end edges of the calibration plate.

3. The method according to claim 2, characterized in that The step of finding the numbers of two laser lines located at the boundary of the colored area of ​​the calibration plate according to the laser intensity curve comprises: Based on the calibration plate, the laser line segments formed by the laser line hitting the calibration plate, and the corresponding laser intensity information, a sliding window method is used on the laser intensity curve to identify the boundaries of different areas on the calibration plate; Find the two positions where the laser intensity step is the largest on the laser intensity curve. These are the two laser points on the calibration plate where the two laser lines located at the boundary of the colored area of ​​the calibration plate hit the calibration plate.

4. The method according to claim 3, characterized in that The method of finding the corresponding grayscale value on the calibration plate based on the laser intensity values ​​of the two laser lines located at the boundary of the calibration plate, and determining the absolute longitudinal positions of the two laser lines on the calibration plate based on the grayscale value, comprises: According to the laser intensity values ​​of the two laser lines, find the corresponding grayscale value on the calibration plate; Find the corresponding vertical absolute position in the dark area of ​​the position boundary based on the grayscale value.

5. The method according to claim 3, characterized in that: Also includes: Based on the light-colored area with the largest width on the calibration plate, the measured length of the laser line segment on the light-colored area and the actual design width of the light-colored area, the slope of the laser line segment on the calibration plate is calculated; Based on the slope of the laser line segment, the length of the laser line segment in each area and the absolute lateral position of all laser lines hitting the colored area of ​​the calibration plate are calculated.

6. The method according to claim 5, characterized in that The step of calculating the slope of the laser line segment on the calibration plate based on the light-colored area with the maximum width on the calibration plate, the measured length of the laser line segment on the light-colored area, and the actual designed width of the light-colored area comprises: Assume the laser line number is m i ,m j The two laser lines hit the two ends of the light-colored area s with the largest width. The distance measurement result of the two laser lines is d i ,d j , the angle between the two laser lines θ=(m i -m j )*θ0, θ0 is the angular resolution of the laser line, let m i For laser lines with larger numbers, the length of the laser line segment measured in the light-colored area is If the actual design length of the light-colored area is l s , then the slope of the laser line segment is k = l s ′ / l s .

7. A system for determining the position of a laser point on a two-dimensional plane, characterized in that: include: A first acquisition module is used to acquire the number of the laser line on the calibration plate according to the distance information of each laser line and the plane equation obtained according to the plane characteristics of the calibration plate; A second acquisition module is used to acquire a laser line segment and a corresponding laser intensity curve obtained by each laser line hitting the calibration plate, wherein the laser intensity on the laser intensity curve has a corresponding relationship with the grayscale value on the calibration plate; A search module is used to search for the numbers of two laser lines located at the boundary of the colored area of ​​the calibration plate according to the laser intensity curve; A determination module is used to find the corresponding grayscale value on the calibration plate based on the laser intensity values ​​of the two laser lines located at the boundary of the calibration plate, and determine the absolute longitudinal positions of the two laser lines on the calibration plate based on the grayscale value; The calibration plate includes a colored area and a colorless area, the colored area includes a plurality of alternating dark areas and light areas in the width direction of the calibration plate, different dark areas and different light areas have different widths, and the depth value of the same area is different in the height direction; The first acquisition module is specifically used to calculate the coordinates of the point where each laser line hits the calibration board in the laser coordinate system according to the number of each laser line and the corresponding laser distance information, and convert the coordinates of the point where each laser line hits the calibration board in the laser coordinate system into the position in the calibration board coordinate system according to the transformation matrix between the laser coordinate system and the calibration board coordinate system. Based on the laser point hitting the calibration board satisfying the plane constraint, a plane constraint equation is established, which characterizes the relationship between the transformation matrix, the laser line number and the laser distance information. Based on the numbers of multiple specific laser lines and the corresponding laser distance information, the plane constraint equation is solved, and the number of each laser line and the corresponding laser distance information are substituted into the solved plane constraint equation for verification, so as to obtain the number of the laser line that can hit the calibration board.

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