Laser ranging distance correction method and system

Abstract

The invention relates to a laser ranging distance correction method and system. The method comprises the following steps that a laser ranging unit and a camera are carried on the same holder at the same time; a plurality of reflective stickers are connected to the calibration plate; moving the calibration plate to enable the calibration plate to be perpendicular to the optical axis of the camera, and enabling the intersection point of the optical axis of the camera and the calibration plate to coincide with the midpoint of the calibration plate; starting a laser ranging unit, adjusting the posture of the laser ranging unit, enabling the laser to sequentially irradiate on each reflective sticker according to a preset sequence, and recording the reflection intensity when the laser irradiates on each reflective sticker; recording the center of the reflective sticker with the maximum reflective intensity as the intersection point of the actual laser optical axis and the calibration plate; constructing a three-dimensional polygon; and solving a laser optical axis correction parameter, and correcting the current actual laser ranging value according to the laser optical axis correction parameter. The implementation process is simple, the laser optical axis correction parameters can be repeatedly used after being obtained at a time, and the problem that the laser ranging value error is too large is efficiently solved.

Description

Technical Field

[0001] The present invention relates to the technical field of computer vision, and particularly to a method and system for correcting laser ranging distance. Background Art

[0002] During the process of target tracking based on an unmanned aerial vehicle (UAV), the situation of losing the target usually occurs. To solve this problem, the target is often re-projected into the image, and the possible positions of the tracking frame are predicted by using the historical coordinate values of the target in the image. In this step, the depth information of the target (i.e., the distance between the UAV and the target) needs to be obtained through a laser ranging unit.

[0003] However, in the prior art, since the optical axes of the laser ranging unit and the camera are not parallel, the error of the depth information of the target actually obtained by the laser ranging unit is very large, further resulting in the inability to complete tasks such as target tracking and re-supplement of lost targets. Summary of the Invention

[0004] To solve the above problems, the present invention provides a method and system for correcting laser ranging distance, the implementation process of which is simple, and the laser optical axis correction parameters can be reused after being obtained once, so as to efficiently solve the problem of excessive error of the laser ranging value.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] On the one hand, a method for correcting laser ranging distance is provided, which includes the following steps:

[0007] Mount a laser ranging unit and a camera on the same turntable, and denote the camera coordinate system as O C -X C Y C Z C , and the coordinate system of the laser ranging unit as O L -X L Y L Z L ;

[0008] Set up a calibration plate, and connect a plurality of reflective stickers to the calibration plate;

[0009] Move the calibration plate so that the optical axis of the calibration plate and the camera are perpendicular to each other, and the intersection point of the optical axis of the camera and the calibration plate coincides with the midpoint C c of the calibration plate;

[0010] Turn on the laser ranging unit to output laser, and on the premise of keeping the position of the origin O L unchanged, adjust the attitude of the laser ranging unit so that the laser irradiates each reflective sticker in a predetermined order, and record the reflection intensity when the laser irradiates each reflective sticker.

[0011] Mark the center of the reflective sticker with the maximum reflective intensity as the intersection point P of the actual laser optical axis and the calibration plate;

[0012] According to the origin O of the camera coordinate system C and the origin O of the laser ranging unit coordinate system L , the intersection point C of the standard laser optical axis and the calibration plate L , the intersection point P, the midpoint C of the calibration plate c , the origin O of the laser ranging unit coordinate system L , and the intersection point P to construct a three-dimensional polygon;

[0013] Solve the laser optical axis correction parameter θ according to the geometric relationship of the three-dimensional polygon;

[0014] Correct the current actual laser ranging value obtained through the laser ranging unit according to the laser optical axis correction parameter θ.

[0015] Preferably, the included angles formed between the X C axis and the X L axis, between the Y C axis and the Y L axis, and between the Z C axis and the Z L axis are all not 0°.

[0016] Preferably, the sizes of each reflective sticker are the same.

[0017] Preferably, the laser reflected after the laser irradiates on the reflective sticker is received by the laser ranging unit, and the corresponding reflective intensity is obtained after signal processing.

[0018] Preferably, the laser optical axis correction parameter θ is the included angle between the line segments O L P, O L C L therebetween.

[0019] Preferably, the expression of the laser optical axis correction parameter θ is as follows:

[0020]

[0021] where W and H are the width and height of the calibration plate respectively; d is the installation distance between the laser ranging unit and the camera; D is the distance D between the camera and the calibration plate; a and b are the abscissa and ordinate of the intersection point P respectively.

[0022] Preferably, correcting the current actual laser ranging value obtained through the laser ranging unit according to the laser optical axis correction parameter θ includes:

[0023] Correct the current actual laser ranging value obtained through the laser ranging unit according to the following formula:

[0024] D real = D m × cosθ

[0025] Wherein, D m is the current actual laser ranging value before calibration; D real is the laser ranging value after calibration.

[0026] Preferably, the length of each reflective sticker is 1 - 3 cm and the width is 1 - 3 cm.

[0027] Preferably, the line segment O c O L is parallel to the Y C axis.

[0028] On the other hand, a laser ranging distance correction system is also provided, which includes:

[0029] A pan-tilt head;

[0030] A calibration board;

[0031] A plurality of reflective stickers, all of which are connected to the calibration board;

[0032] A laser ranging unit, which is used to output laser for ranging;

[0033] A camera, which is used to acquire an image of the calibration board;

[0034] A polygon construction unit, which is used to construct a three-dimensional polygon according to the origin O C of the camera coordinate system, the origin O L of the laser ranging unit coordinate system, the intersection point C L of the standard laser optical axis and the calibration board, the intersection point P of the actual laser optical axis and the calibration board, the midpoint C c of the calibration board, the origin O L of the laser ranging unit coordinate system, and the intersection point P of the actual laser optical axis and the calibration board;

[0035] A correction parameter calculation unit, which is used to solve the laser optical axis correction parameter θ according to the geometric relationship of the three-dimensional polygon;

[0036] A ranging distance correction unit, which is used to correct the current actual laser ranging value obtained by the laser ranging unit according to the laser optical axis correction parameter θ.

[0037] The beneficial effects of the present invention are:

[0038] The calibration method of the present application has a simple implementation process. By setting the reflective stickers on the calibration board and establishing the camera coordinate system, the intersection position of the camera optical axis, the actual laser optical axis of the laser ranging unit and the calibration board can be obtained. Further, the laser optical axis calibration parameter θ can be obtained according to the geometric relationship of the polygon constructed by the intersection points, and the laser ranging value can be calibrated by the laser optical axis calibration parameter θ. Moreover, once the laser optical axis calibration parameter θ is obtained, it can be used repeatedly to efficiently solve the problem of excessive error in the laser ranging value. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a top view schematic diagram of the laser ranging unit, the camera and the calibration board in the present invention;

[0040] Figure 2 It is a schematic diagram of the relative position relationship of the laser ranging unit, the camera and the calibration board in the present invention;

[0041] Figure 3 It is a front view schematic diagram of the calibration board in the present invention;

[0042] Figure 4 It is a schematic diagram of the three-dimensional polygon constructed in the present invention;

[0043] Figure 5 It is a schematic diagram of the structure of the laser ranging distance calibration system in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] To make the objectives, technical solutions and advantages of the present technical solution clearer and more understandable, the present technical solution will be further described in detail below in conjunction with specific embodiments. It should be understood that these descriptions are exemplary and not intended to limit the scope of the present technical solution.

[0045] Embodiment 1:

[0046] This embodiment provides a laser ranging distance calibration method, which includes the following steps:

[0047] S1. As shown in Figure 1-2 , the laser ranging unit L and the camera C are simultaneously mounted on the same pan-tilt 100. Among them, the camera C is horizontally arranged, and the camera coordinate system is denoted as O C -X C Y C Z C . The height direction of the camera C is the X C axis, the lens optical axis direction of the camera C is the Z C axis, and the Z C axis is parallel to the horizontal plane, and the Y C axis is perpendicular to the X C Z C plane; the laser ranging unit L is inclined, and the laser ranging unit coordinate system is denoted as OL -X L Y L Z L The height direction of the laser ranging unit L is the X L axis, and the direction of the laser optical axis output by the laser ranging unit L is the Z L axis, and the Y L axis is perpendicular to the X L Z L plane, and the included angles formed between the X C axis and the X L axis, between the Y C axis and the Y L axis, and between the Z C axis and the Z L axis are all not 0°, and the distance O c O L between O c O L is denoted as the installation distance d between the laser ranging unit L and the camera C. At the same time, the line segment O c O L is parallel to the Y C axis;

[0048] At the same time, as Figure 3 shown, a calibration board B with a regular geometric shape such as a rectangle or a square is set, and the length of the calibration board B is W and the width is H. And m×n reflective stickers 1 are connected (such as by bonding, etc.) on the calibration board B. Among them, m and n are the number of rows and columns respectively. Preferably, in this embodiment, each reflective sticker 1 is a square or a rectangle and has the same size, such as a length of (1 - 3) cm and a width of (1 - 3) cm. The distance between the edge reflective sticker 1 and the edge of the calibration board B, the horizontal distance and the vertical distance between adjacent two reflective stickers 1 are all known. And since the size of each reflective sticker 1 and the length and width of the calibration board B are known, the position of each reflective sticker 1 on the calibration board B is a known quantity;

[0049] S2. Keep the attitudes of the pan-tilt 100 and the camera C unchanged. Establish a calibration board coordinate system with the width direction of the calibration board B as the X axis, the height direction as the Y axis, and the thickness direction as the Z axis. And the X axis and the Y axis are respectively parallel to the Y c axis and the X c axis. Move the calibration board B so that the optical axis of the calibration board B and the camera C are perpendicular to each other. At the same time, the entire calibration board B is within the imaging field of view of the camera C, and the intersection point of the optical axis of the camera C and the calibration board B coincides with the midpoint C c (0.5W, 0.5H) of the calibration board B, and the line segment O c C c is denoted as the distance D between the camera C and the calibration board B at this time;

[0050] S3. Keep the postures of the pan-tilt 100, the camera C, and the calibration board B unchanged. Turn on the laser ranging unit L to output laser. While keeping the origin O L at a fixed position, adjust the posture of the laser ranging unit L (for example, rotate the laser ranging unit L around one of the X L axis, Y L axis, and Z L axis) so that the laser irradiates each reflective sticker 1 in a predetermined order, and record the reflected light intensity when the laser irradiates each reflective sticker 1. In this embodiment, the laser reflected after irradiating the reflective sticker 1 is received by the laser ranging unit L, and the corresponding reflected light intensity is obtained after signal processing;

[0051] And mark the center of the reflective sticker 1 with the maximum reflected light intensity as the intersection point P(a, b) of the actual laser optical axis and the calibration board B. The actual laser optical axis is the laser optical axis output by the laser ranging unit L and irradiating the reflective sticker 1 with the maximum reflected light intensity;

[0052] S4. As shown in Figure 4 , connect the origin O C of the camera coordinate system, the origin O L of the laser ranging unit coordinate system, the intersection point C L of the standard laser optical axis and the calibration board B, the intersection point P of the actual laser optical axis and the calibration board B, and the midpoint C c of the calibration board B in sequence, and connect the origin O L of the laser ranging unit coordinate system and the intersection point P of the actual laser optical axis and the calibration board B to construct a three-dimensional polygon. Among them, the line segment O C C C is collinear with the optical axis of the camera C, the line segment O L P is collinear with the laser optical axis output by the laser ranging unit L and irradiating the reflective sticker 1 with the maximum reflected light intensity, and the line segment O L C L is collinear with the standard laser optical axis. Therefore, the angle θ between the line segments O L P and O L C L is also the angle between the actual laser optical axis and the standard laser optical axis. This angle θ is the laser optical axis correction parameter;

[0053] In this embodiment, the standard laser optical axis refers to when the X L axis, Y L axis, and Z L axis of the laser ranging unit coordinate system correspond to the X C axis, Y C axis, and Z CWhen the axes are parallel, the optical axis of the laser ranging unit L outputs. At this time, the optical axis of the laser is parallel to the optical axis of the camera C, and is also perpendicular to the calibration plate B, and there is O c C c = O L C L = D;

[0054] S5. Solve the laser optical axis correction parameter θ according to the geometric relationship of the three-dimensional polygon;

[0055] Specifically, according to Figure 4 the relationship shown in, the line segment C c C L = O c O L = d can be determined. Then the intersection point C L of the standard laser optical axis and the calibration plate B has coordinates (0.5W - d, 0.5H). Further, since the line segment O L C L is perpendicular to the calibration plate B, then O L C L = D, and the formula (1) holds:

[0056]

[0057] Then

[0058] And S6. Correct the current actual laser ranging value obtained through the laser ranging unit L according to the laser optical axis correction parameter θ, which specifically includes the following steps:

[0059] D real = D m × cosθ (2)

[0060] where D m is the current actual laser ranging value before correction; D real is the laser ranging value after correction.

[0061] Ideally, the optical axes of the laser ranging unit L and the camera C should be parallel. At this time, the laser ranging value obtained by the laser ranging unit L (equivalent to Figure 4 O L C L in) is the ranging value without error. However, due to installation errors, vibrations, etc., in fact, the optical axes of the laser ranging unit L and the camera C are not parallel, resulting in a deviation in the laser ranging value actually obtained by the laser ranging unit L (equivalent to Figure 4 PO L in), so it is necessary to correct the actually obtained laser ranging value to make it close to or equal to the laser ranging value under ideal conditions (that is, equivalent to according to POL Obtaining O L C L in the process).

[0062] In this embodiment, through the setting of the reflective stickers on the calibration board and the establishment of the camera coordinate system, the intersection position of the camera optical axis, the actual laser optical axis of the laser ranging unit and the calibration board can be obtained. Further, according to the geometric relationship of the polygon constructed by the intersection points, the laser optical axis correction parameter θ can be obtained, and then the laser ranging value can be corrected by the laser optical axis correction parameter θ. The whole implementation process is simple, and the laser optical axis correction parameter θ can be reused after being obtained once to solve the problem of excessive error of the laser ranging value.

[0063] Embodiment 2:

[0064] This embodiment provides a laser ranging distance correction system, which can implement the laser ranging distance correction method in Embodiment 1. As Figure 5 shown, the laser ranging distance correction system includes:

[0065] Pan-tilt 100;

[0066] Calibration board B, which is in a regular geometric shape as a whole;

[0067] A plurality of reflective stickers 1, which are all connected to the calibration board B, and the position of each reflective sticker 1 on the calibration board B is known;

[0068] Laser ranging unit L, which is used to output laser for ranging;

[0069] Camera C, which is used to acquire an image of the calibration board B;

[0070] Polygon construction unit 200, which is used to construct a three-dimensional polygon according to the origin O of the camera coordinate system C , the origin O of the laser ranging unit coordinate system L , the intersection point C of the standard laser optical axis and the calibration board B L , the intersection point P of the actual laser optical axis and the calibration board B, the midpoint C of the calibration board B c , the origin O of the laser ranging unit coordinate system L , and the intersection point P of the actual laser optical axis and the calibration board B;

[0071] Correction parameter calculation unit 300, which is used to solve the laser optical axis correction parameter θ according to the geometric relationship of the three-dimensional polygon;

[0072] Ranging distance correction unit 400, which is used to correct the currently obtained actual laser ranging value through the laser ranging unit L according to the laser optical axis correction parameter θ.

[0073] In summary, the calibration method in this application has a simple implementation process. By setting the reflective stickers on the calibration board and establishing the camera coordinate system, the intersection position of the camera optical axis, the actual laser optical axis of the laser ranging unit, and the calibration board can be obtained. Further, the laser optical axis calibration parameter θ can be obtained according to the geometric relationship of the polygon constructed by the intersection points, and then the laser ranging value can be calibrated by the laser optical axis calibration parameter θ. Moreover, after obtaining the laser optical axis calibration parameter θ once, it can be used repeatedly to efficiently solve the problem of excessive error in the laser ranging value.

[0074] The above content is only the preferred embodiment of the present invention. For those of ordinary skill in the art, many changes can be made in the specific implementation manner and application scope according to the idea of the present technical content. As long as these changes do not depart from the concept of the present invention, they all belong to the protection scope of this patent.

Claims

1. A laser ranging distance correction method, characterized in that: The steps include: The laser ranging unit and the camera are mounted on the same gimbal, and the camera coordinate system is denoted as O C -X C Y C Z C , the laser ranging unit coordinate system is O L -X L Y L Z L ; A calibration plate is provided, and a plurality of reflective stickers are connected to the calibration plate; Move the calibration plate so that the optical axes of the calibration plate and the camera are perpendicular to each other, and the intersection of the optical axis of the camera and the calibration plate is at the midpoint C of the calibration plate. c coincide; Turn on the laser distance measuring unit to output laser and keep the origin O L Under the premise of keeping the position unchanged, adjust the posture of the laser ranging unit so that the laser is irradiated on each reflective sticker in a predetermined order, and record the reflective intensity when the laser is irradiated on each reflective sticker; The center of the reflective tape with the highest reflective intensity is recorded as the intersection point P of the actual laser optical axis and the calibration plate; According to the origin of the camera coordinate system O C , laser ranging unit coordinate system origin O L , the intersection point C of the standard laser optical axis and the calibration plate L , intersection point P, midpoint C of the calibration plate c , laser ranging unit coordinate system origin O L , the intersection point P constructs a solid polygon; Solving the laser optical axis correction parameter θ according to the geometric relationship of the three-dimensional polygon; The current actual laser distance measurement value obtained by the laser distance measurement unit is corrected according to the laser optical axis correction parameter θ.

2. The laser ranging distance correction method according to claim 1, characterized in that: The X C Axis and X L Between axes, Y C Axis and Y L Between axes, Z C Axis and Z L The angle between the axes is not 0°.

3. The laser ranging distance correction method according to claim 1, characterized in that: Each reflective tape is the same size.

4. The laser ranging distance correction method according to claim 1, characterized in that: After the laser is irradiated on the reflective sticker, the reflected laser is received by the laser ranging unit, and the corresponding reflection intensity is obtained after signal processing.

5. The laser ranging distance correction method according to claim 1, characterized in that: The laser optical axis correction parameter θ is the line segment O L P, O L C L The angle between.

6. The laser ranging distance correction method according to claim 5, characterized in that: The expression of the laser optical axis correction parameter θ is as follows: Wherein, W and H are the width and height of the calibration plate, respectively; d is the installation distance between the laser ranging unit and the camera; D is the distance D between the camera and the calibration plate; a and b are the horizontal and vertical coordinates of the intersection point P, respectively.

7. The laser ranging distance correction method according to claim 5, characterized in that: The current actual laser distance measurement value obtained by the laser distance measurement unit is corrected according to the laser optical axis correction parameter θ, including: The current actual laser distance measurement value obtained by the laser distance measurement unit is corrected according to the following formula: D real =D m ×cosθ Among them, D m is the current actual laser distance measurement value before correction; D real is the corrected laser distance measurement value.

8. The laser ranging distance correction method according to claim 1, characterized in that: Each reflective tape is 1-3cm long and 1-3cm wide.

9. The laser ranging distance correction method according to claim 1, characterized in that: Line segment O c O L With Y C Axis parallel.

10. A laser ranging distance correction system, characterized in that: include: PTZ; Calibration plate; A plurality of reflective stickers, all of which are connected to the calibration plate; A laser distance measuring unit, which is used to output a laser for distance measurement; A camera for acquiring an image of the calibration plate; A polygon construction unit is used to construct a polygon according to the origin O of the camera coordinate system. C , laser ranging unit coordinate system origin O L , the intersection point C of the standard laser optical axis and the calibration plate L , the intersection point P of the actual laser optical axis and the calibration plate, the midpoint C of the calibration plate c , laser ranging unit coordinate system origin O L , the intersection point P of the actual laser optical axis and the calibration plate constructs a solid polygon; A correction parameter calculation unit, which is used to solve the laser optical axis correction parameter θ according to the geometric relationship of the solid polygon; The ranging distance correction unit is used to correct the current actual laser ranging value obtained by the laser ranging unit according to the laser optical axis correction parameter θ.

Images