A laser ranging method, system, lidar, and radar article

Abstract

This invention relates to a laser ranging method, system, lidar, and radar product. The method includes the following steps: recording the number of triggers of each pixel in the photosensitive receiving array during the ranging period to form a grayscale image of the light spot, and finding the centroid position of the light spot in the grayscale image; obtaining the histogram of the photosensitive receiving array, and determining the peak-finding range in the DTOF ranging histogram based on the centroid position of the light spot in the grayscale image as a reference to determine the centroid-distance relationship; performing peak finding based on the determined peak-finding range to perform peak fitting to calculate the accurate ranging time, and converting it into the distance value. This invention uses the grayscale image of the light spot of the photosensitive receiving matrix to determine the peak-finding range of the DTOF ranging histogram, reducing internal resource consumption and peak-finding computational power, lowering system costs, and filtering noise peaks on the histogram, resulting in higher short-range accuracy and better system stability for the DTOF scheme.

Description

Technical Field

[0001] This invention relates to the field of lidar technology, and more specifically, to a laser ranging method, system, lidar, and radar products. Background Technology

[0002] DTOF stands for Direct Time of Flight. It works by continuously sending light pulses to a target and then using a sensor to receive the light returning from the object. The distance to the target is determined by measuring the round-trip time of the light pulses. The distance D = C * T / 2, where C is the speed of light (3 * 10⁻⁶). 8 Meters per second, where T is the time interval from transmission to reception; Currently, there are generally two methods for DTOF ranging. One method uses a single APD or PD transistor as the receiving device, generating a ranging time with each transmission. The second method uses a SPAD array. Since SPADs can be manufactured using CMOS technology and can be integrated with the TDC back-end processing circuit, it is currently the mainstream low-cost DTOF solution. However, because SPAD arrays are very sensitive, they use multiple laser transmissions and receive multiple ranging data to generate a histogram. The ranging time is found by peak finding in the histogram, which requires a large area of ​​RAM resources on the chip for histogram storage. Furthermore, due to the accuracy of TDC and peak finding errors, the current DTOF solution has poor accuracy and high cost at close range. Therefore, a laser ranging method that can improve this problem is needed. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a laser ranging method, system, lidar and radar product, which addresses the above-mentioned deficiencies of the prior art.

[0004] The technical solution adopted by this invention to solve its technical problem is: A laser ranging method is constructed, comprising the following steps: Record the number of triggers of each pixel in the photosensitive receiving array during the ranging period to form a grayscale image of the light spot, and find the centroid position of the light spot in the grayscale image; Obtain the histogram of the photosensitive receiving array, and determine the peak-finding range in the histogram based on the centroid position of the light spot in the grayscale image; The distance measurement time is calculated by finding the peak within the determined peak range and fitting the peak value. The distance value is then calculated by multiplying the peak value by 1 / 2 the speed of light.

[0005] The laser ranging method of the present invention, wherein the method of recording the number of triggers of each pixel of the photosensitive receiving array within the ranging period to form a grayscale image of the light spot, and finding the centroid position of the light spot in the grayscale image includes the following method: The laser of the dToF module emits pulse waves into the scene. A SPAD or other photosensitive receiver array receives the pulse waves reflected back from the target object. Individual cells on the array are triggered probabilistically. The dToF module emits and receives N light signals within a single frame measurement time, then records the number of times each cell is triggered during those N flight times, forming a continuous 2D image. The value of each cell is f(x, y), where x represents the cell's position in the X-direction of the array, and y represents its position in the Y-direction. Using this 2D image, let the coordinates of each pixel in the x-direction be Xi, the sum of the corresponding pixel values ​​be Pi, and the coordinates of the centroid in the x-direction be Xo. Then: ;

[0006] Let the y-coordinate of each pixel in the 2D image be Yj, the sum of the corresponding pixel values ​​be Pj, and the y-coordinate of the centroid be Yo. Then: .

[0007] The laser ranging method of the present invention, wherein determining the peak-finding range in the histogram based on the centroid position of the light spot in the grayscale image includes the following method: After obtaining the centroid positions Xo and Yo, the peak-finding range of the histogram is determined according to the calibrated lookup table; This search table sets up several targets at different distances through the lidar calibration process, calibrates the centroid position and distance range, confirms the histogram peak finding range, and facilitates the subsequent DTOF histogram peak finding algorithm calculation.

[0008] In the laser ranging method of the present invention, the photosensitive receiving array is a SPAD array, a SiPM array, or an APD array.

[0009] A laser ranging system includes a photosensitive receiving array unit, a data processing unit, and a distance value calculation unit; The photosensitive receiving array unit records the number of triggers of each pixel in the photosensitive receiving array during the ranging period, forms a grayscale image of the light spot, and finds the centroid position of the light spot in the grayscale image; it is also used to generate a histogram of the photosensitive receiving array. The data processing unit determines the peak-finding range in the histogram based on the centroid position of the light spot in the grayscale image. The distance calculation unit calculates the distance measurement time by finding the peak within the determined peak range and fitting the peak value, and then multiplies it by 1 / 2 the speed of light to obtain the distance value.

[0010] In the laser ranging system of the present invention, the photosensitive receiving array unit records the number of triggers of each pixel of the photosensitive receiving array during the ranging period, forming a grayscale image of the light spot. The centroid position of the light spot in the grayscale image is found by: The laser of the dToF module emits pulse waves into the scene. A SPAD or other photosensitive receiver array receives the pulse waves reflected back from the target object. Individual cells on the array are triggered probabilistically. The dToF module emits and receives N light signals within a single frame measurement time, then records the number of times each cell is triggered during those N flight times, forming a continuous 2D image. The value of each cell is f(x, y), where x represents the cell's position in the X-direction of the array, and y represents its position in the Y-direction. Using this 2D image, let the coordinates of each pixel in the x-direction be Xi, the sum of the corresponding pixel values ​​be Pi, and the coordinates of the centroid in the x-direction be Xo. Then: ; Let the y-coordinate of each pixel in the 2D image be Yj, and the corresponding pixel value be Pi. Let the y-coordinate of the centroid be Yo. Then: .

[0011] In the laser ranging system of the present invention, the data processing unit determines the peak-finding range in the histogram based on the centroid position of the light spot in the grayscale image using a lookup table. This search table sets up several targets at different distances through the lidar calibration process, calibrates the centroid position and distance range, confirms the histogram peak finding range, and facilitates the subsequent DTOF histogram peak finding algorithm calculation.

[0012] In the laser ranging system of the present invention, the photosensitive receiving array is a SPAD array, a SiPM array, or an APD array.

[0013] A lidar, wherein the lidar is equipped with a laser ranging system as described above.

[0014] A radar product, wherein the radar product is provided with a lidar as described above.

[0015] The beneficial effects of this invention are as follows: This invention uses the grayscale image of the light spot of the photosensitive receiving matrix to determine the peak-finding range of the histogram of DTOF ranging, reducing internal resource consumption and peak-finding computing power, reducing system cost, and at the same time filtering noise peaks on the histogram, making the DTOF scheme more accurate at close range and more stable. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort: Figure 1 This is a flowchart of a laser ranging method according to a preferred embodiment of the present invention; Figure 2 This is a schematic diagram of the laser ranging method according to a preferred embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the distance measurement calculation principle of the laser ranging method according to a preferred embodiment of the present invention; Figure 4 This is a grayscale image of the laser ranging method of the preferred embodiment of the present invention when the distance is relatively far. Figure 5 This is a grayscale image of the laser ranging method of the preferred embodiment of the present invention at a suitable distance; Figure 6 This is a grayscale image of the laser ranging method of the preferred embodiment of the present invention when the distance is relatively close; Figure 7 The laser ranging method of the preferred embodiment of the present invention includes a histogram of a photosensitive receiving array with corresponding markers for different distances; Figure 8 This is a block diagram illustrating the principle of a laser ranging system according to a preferred embodiment of the present invention.

[0017] Figure 9 This is a block diagram for filtering histogram peaks and finding interference in this invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, a clear and complete description will be provided below in conjunction with the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention. Example 1

[0019] The laser ranging method of the preferred embodiment of the present invention, such as Figure 1 As shown, see also Figure 2-7 This includes the following steps: S01: Record the number of triggers of each pixel in the photosensitive receiving array during the ranging period to form a grayscale image of the light spot and find the centroid position of the light spot in the grayscale image; S02: Obtain the histogram of the photosensitive receiving array, and determine the peak-finding range in the histogram based on the centroid position of the light spot in the grayscale image; S03: Based on the determined peak search range, perform peak search and peak fitting to calculate the distance measurement time, and multiply by 1 / 2 the speed of light to calculate the distance value; This invention uses the grayscale image of the light spot of the photosensitive receiving matrix to determine the peak-finding range of the histogram of DTOF ranging, reducing internal resource consumption and peak-finding computational power, and lowering system cost. At the same time, filtering noise peaks on the histogram makes the DTOF scheme more accurate at close range and more stable.

[0020] like Figure 4-6 As shown, the light spot at close range will shift to the edge of the receiving SPAD array, while the farther away it is, the more centered it will be. Figure 7 As shown, the corresponding distances correspond to histogram intervals for different time periods. By using this correspondence to filter out noise peaks on the histogram, we can reduce internal resource consumption and peak-finding computing power, improve short-range accuracy, and make the entire system more stable. Preferably, the method of recording the number of triggers of each pixel in the photosensitive receiving array during the ranging period to form a grayscale image of the light spot, and finding the centroid position of the light spot in the grayscale image includes the following steps: The laser of the dToF module emits pulse waves into the scene. A SPAD or other photosensitive receiver array receives the pulse waves reflected back from the target object. Individual cells on the array are triggered probabilistically. The dToF module emits and receives N light signals within a single frame measurement time, then records the number of times each cell is triggered during those N flight times, forming a continuous 2D image. The value of each cell is f(x, y), where x represents the cell's position in the X-direction of the array, and y represents its position in the Y-direction. Using this 2D image, let the coordinates of each pixel in the x-direction be Xi, the sum of the corresponding pixel values ​​be Pi, and the coordinates of the centroid in the x-direction be Xo. Then: ; Let the y-coordinate of each pixel in the 2D image be Yj, and the corresponding pixel value be Pi. Let the y-coordinate of the centroid be Yo. Then: .

[0021] Preferably, determining the peak-finding range in the histogram based on the centroid position of the light spot in the grayscale image includes the following methods: After obtaining the centroid positions Xo and Yo, the peak-finding range of the histogram is determined according to the calibrated lookup table; A preferred list of correspondences is shown below:

[0022] Furthermore, the search table sets up several targets at different distances through the lidar calibration process to calibrate the centroid position and distance range, confirm the histogram peak finding range, and facilitate the subsequent DTOF histogram peak finding algorithm calculation.

[0023] Preferably, the photosensitive receiving array is a SPAD array, SiPM array, APD array, etc. Example 2

[0024] A laser ranging system, such as Figure 8 As shown, see also Figure 9 It includes a photosensitive receiving array unit 1, a data processing unit 2, and a distance value calculation unit 3; Photosensitive receiving array unit 1 records the number of triggers of each pixel of the photosensitive receiving array during the ranging period, forms a grayscale image of the light spot, and finds the centroid position of the light spot in the grayscale image; it is also used to generate a histogram of the photosensitive receiving array. Data processing unit 2 determines the peak finding range in the histogram based on the centroid position of the light spot in the grayscale image; The distance calculation unit 3 calculates the distance measurement time by finding the peak and fitting the peak value based on the determined peak range, and multiplies it by 1 / 2 the speed of light to calculate the distance value. This invention uses the grayscale image of the light spot of the photosensitive receiving matrix to determine the peak-finding range of the histogram of DTOF ranging, reducing internal resource consumption and peak-finding computational power, and lowering system cost. At the same time, filtering noise peaks on the histogram makes the DTOF scheme more accurate at close range and more stable.

[0025] Preferably, the photosensitive receiving array unit records the number of triggers of each pixel of the photosensitive receiving array during the ranging period, forming a grayscale image of the light spot. The centroid position of the light spot in the grayscale image is found by: The laser of the dToF module emits pulse waves into the scene. A SPAD or other photosensitive receiver array receives the pulse waves reflected back from the target object. Individual cells on the array are triggered probabilistically. The dToF module emits and receives N light signals within a single frame measurement time, then records the number of times each cell is triggered during those N flight times, forming a continuous 2D image. The value of each cell is f(x, y), where x represents the cell's position in the X-direction of the array, and y represents its position in the Y-direction. Using this 2D image, let the coordinates of each pixel in the x-direction be Xi, the sum of the corresponding pixel values ​​be Pi, and the coordinates of the centroid in the x-direction be Xo. Then: ; Let the y-coordinate of each pixel in the 2D image be Yj, the sum of the corresponding pixel values ​​be Pj, and the y-coordinate of the centroid be Yo. Then: .

[0026] Preferably, the data processing unit determines the peak-finding range in the histogram based on the centroid position of the light spot in the grayscale image using the following method: After obtaining the centroid positions Xo and Yo, the peak-finding range of the histogram is determined according to the calibrated lookup table.

[0027] Furthermore, this search table uses a lidar calibration process to set up several targets at different distances, calibrating the centroid position and distance range, confirming the histogram peak finding range, and facilitating subsequent DTOF histogram peak finding algorithm calculations. Figure 9 As shown, when the centroid position detects the dashed area, interference peaks from other areas can be filtered out, ensuring the stability of the ranging.

[0028] Preferably, the photosensitive receiving array is a SPAD array, a SiPM array, or an APD array. Example 3

[0029] A lidar, wherein the lidar is equipped with a laser ranging system as described above. Example 4

[0030] A radar product, wherein the radar product is equipped with a lidar as described above; the radar product referred to in this application is a product that uses lidar, such as a robot vacuum cleaner, a robot, etc. It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A laser ranging method, characterized in that, Includes the following steps: Record the number of triggers of each pixel in the photosensitive receiving array during the ranging period to form a grayscale image of the light spot, and find the centroid position of the light spot in the grayscale image; Obtain the histogram of the photosensitive receiving array, and determine the peak-finding range in the histogram based on the centroid position of the light spot in the grayscale image; The distance measurement time is calculated by finding the peak within the determined peak range and fitting the peak value. The distance value is then calculated by multiplying the peak time by 1 / 2 the speed of light. The method for determining the peak-finding range in the histogram based on the centroid position of the light spot in the grayscale image includes: after obtaining the centroid positions Xo and Yo, the peak-finding range of the histogram is determined according to the calibrated lookup table; the lookup table is set with several targets at different distances through the lidar calibration process to calibrate the centroid position and distance range, confirm the peak-finding range of the histogram, and facilitate the subsequent DTOF histogram peak-finding algorithm calculation.

2. The laser ranging method according to claim 1, characterized in that, The method for recording the number of triggers of each pixel in the photosensitive receiving array during the ranging period to form a grayscale image of the light spot, and finding the centroid position of the light spot in the grayscale image includes: The laser of the dToF module emits pulse waves into the scene, and the photosensitive receiving array receives the pulse waves reflected back from the target object. Individual cells on the array are triggered probabilistically. The dToF module emits and receives N light signals within a single frame measurement time, then records the number of times each cell is triggered during those N flight times, forming a continuous 2D image. The value of each cell is f(x, y), where x represents the cell's position in the X-direction of the array, and y represents its position in the Y-direction. Using this 2D image, let the coordinates of each pixel in the x-direction be Xi, the sum of the corresponding pixel values ​​be Pi, and the coordinates of the centroid in the x-direction be Xo. Then: ； Let the coordinate of each pixel in the y-direction of the two-dimensional image be Yj, the sum of the corresponding pixel values ​​be Pj, and the coordinate of the centroid in the y-direction be Yo. Then: 。 3. The laser ranging method according to claim 1, characterized in that, The photosensitive receiving array is a SPAD array, a SiPM array, or an APD array.

4. A laser ranging system, characterized in that, It includes a photosensitive receiving array unit, a data processing unit, and a distance value calculation unit; The photosensitive receiving array unit records the number of triggers of each pixel in the photosensitive receiving array during the ranging period, forms a grayscale image of the light spot, and finds the centroid position of the light spot in the grayscale image; it is also used to generate a histogram of the photosensitive receiving array. The data processing unit determines the peak-finding range in the histogram based on the centroid position of the light spot in the grayscale image. The distance calculation unit calculates the distance measurement time by finding the peak within the determined peak range and fitting the peak value, and then multiplies it by 1 / 2 the speed of light to calculate the distance value. The method for determining the peak-finding range in the histogram based on the centroid position of the light spot in the grayscale image includes: after obtaining the centroid positions Xo and Yo, the peak-finding range of the histogram is determined according to the calibrated lookup table; the lookup table is set with several targets at different distances through the lidar calibration process to calibrate the centroid position and distance range, confirm the peak-finding range of the histogram, and facilitate the subsequent DTOF histogram peak-finding algorithm calculation.

5. The laser ranging system according to claim 4, characterized in that, The photosensitive receiving array unit records the number of triggers for each pixel of the photosensitive receiving array during the ranging period, forming a grayscale image of the light spot. The centroid position of the light spot in the grayscale image is found using: The laser of the dToF module emits pulse waves into the scene, and the photosensitive receiving array receives the pulse waves reflected back from the target object. Individual cells on the array are triggered probabilistically. The dToF module emits and receives N light signals within a single frame measurement time, then records the number of times each cell is triggered during those N flight times, forming a continuous 2D image. The value of each cell is f(x, y), where x represents the cell's position in the X-direction of the array, and y represents its position in the Y-direction. Using this 2D image, let the coordinates of each pixel in the x-direction be Xi, the sum of the corresponding pixel values ​​be Pi, and the coordinates of the centroid in the x-direction be Xo. Then: ； Let the coordinate of each pixel in the y-direction of the two-dimensional image be Yj, the sum of the corresponding pixel values ​​be Pj, and the coordinate of the centroid in the y-direction be Yo. Then: 。 6. The laser ranging system according to claim 4, characterized in that, The photosensitive receiving array is a SPAD array, a SiPM array, or an APD array.

7. A lidar, characterized in that, The lidar is equipped with a laser ranging system as described in any one of claims 4-6.

8. A radar product, characterized in that, The radar product is equipped with the lidar as described in claim 7.

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