Self-adaptive optical axis and visual axis consistency correction method

Abstract

A self-adaptive optical axis and visual axis consistency correction method comprises the following steps: firstly, calibrating an angle between a camera coordinate system and a laser coordinate system, adjusting an image visual axis to be parallel to the axis of a guide rail by using a standard long linear guide rail, controlling a plane target vertical to the guide rail to move on the linear guide rail, and shooting images at the positions of the nearest working distance and the farthest working distance; the distance values of the two positions are recorded at the same time, the pixel coordinates of the laser spots in the image are obtained through image processing, the space coordinates of the two light spots in a camera coordinate system are calculated through the focal length and pixel size parameters of the camera according to a camera imaging model, and a linear equation of the laser axis is established in the camera coordinate system; then, according to the distance obtained through laser ranging, the actual focal length of the camera and the pixel size, the pixel coordinate of a laser spot deviating from the center of the image at the current position is solved through a laser axis linear equation, the original image is cut and displayed with the pixel coordinate of the laser spot as the center, and real-time correction of the visual axis is achieved.

Description

Technical Field

[0001] The invention relates to an adaptive optical axis sight axis consistency correction method, which can ensure that the light spot emitted by the optical axis is always in the center of the camera image when the measuring distance and the camera focal length change, and belongs to the field of photoelectric detection technology. Background Art

[0002] Three-dimensional coordinate photoelectric detection equipment generally has two mechanical rotating axes and two optical detection axes, namely the laser ranging optical axis and the camera imaging visual axis. The three-dimensional coordinate photoelectric detection equipment controls the direction of the laser through the mechanical rotating axis, and uses the measured mechanical angle and laser distance to realize the scanning measurement of the three-dimensional shape of the target. While detecting the distance of the target, the operator needs to observe the specific detection position through the camera. However, due to the existence of installation errors, there is a small angle deviation between the laser optical axis and the camera imaging visual axis. The deviation displacement will increase with the increase of distance. Therefore, there will be a state where the center of the camera image and the laser point do not coincide, and the laser point will change relative to the center of the image with the change of target distance, rotation angle and camera magnification. Therefore, it is necessary to further use image processing methods to ensure that the laser point is always in the center of the image, and will not change significantly with the change of angle, distance and camera magnification, so as to ensure that the target image displayed in the center of the image is the measurement position of the laser measurement point. Summary of the invention

[0003] In order to eliminate the situation that the laser point is not in the center of the image due to the inconsistency between the laser ranging optical axis and the camera imaging visual axis in the three-dimensional coordinate photoelectric detection equipment, an adaptive optical axis visual axis consistency correction method is proposed. This method can compensate the deviation of the laser point from the image center in real time according to the changes in target distance, rotation angle and camera magnification, thereby ensuring that the laser point is always in the center of the displayed image.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] An adaptive optical axis and visual axis consistency correction method, first of all, needs to calibrate the angle between the camera coordinate system and the laser coordinate system. Using a standard long linear guide rail, the image visual axis is adjusted to be parallel to the guide rail axis, and the plane target of the vertical guide rail is controlled to move on the linear guide rail. Images are taken at the closest working distance and the farthest working distance respectively, and the distance values ​​at the two positions are recorded at the same time. The pixel coordinates of the laser point in the image are obtained through image processing, and the spatial coordinates of the two light points in the camera coordinate system are calculated according to the camera imaging model through the focal length and pixel size parameters of the camera, and the linear equation of the laser axis is established in the camera coordinate system.

[0006] Then, in the actual measurement process of applying optoelectronic equipment, the pixel coordinates of the laser spot at the current position that deviates from the center of the image can be solved based on the distance obtained by laser ranging, the actual focal length of the camera, and the pixel size, using the straight line equation of the laser axis. By cutting and displaying the original image with the laser point pixel coordinates as the center, real-time correction of the visual axis can be achieved.

[0007] Compared with the prior art, the present invention has the following beneficial effects:

[0008] (1) The method of the present invention can realize the consistency correction of the laser optical axis and the imaging visual axis in the three-dimensional coordinate photoelectric detection device. After the correction, the jump amount of the laser light spot at the center of the image will be less than 1 pixel.

[0009] (2) The method of the present invention can make the laser spot always be in the center of the image visually, and the amount of its jump is difficult for the human eye to discern, which helps to improve the operability of the device.

[0010] (3) The method of the present invention allows the existence of consistency errors between the optical axis and the visual axis, which helps to reduce equipment installation costs and improve production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the structure of a three-dimensional coordinate photoelectric detection device.

[0012] Figure 2 This is a layout diagram of the correction method.

[0013] Figure 3 To calibrate the target map.

[0014] Figure numerals: 1. ranging laser, 2. monitoring camera, 3. imaging visual axis, 4. azimuth rotation axis, 5. pitch rotation axis, 6. laser ranging optical axis, 7. base; 8. three-dimensional coordinate photoelectric detection equipment, 9. sliding platform, 10. calibration target, 11. two-dimensional adjustment table, 12. long linear guide rail. DETAILED DESCRIPTION

[0015] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0016] An adaptive optical axis and visual axis consistency correction method, comprising:

[0017] (1) Place a three-dimensional coordinate photoelectric detection device 8 at one end of the long linear guide rail 12, set the azimuth rotation axis 4 of the three-dimensional coordinate photoelectric detection device 8 to a 0° position, set the pitch rotation axis 5 to a 0° position, and adjust the horizontal bubble of the three-dimensional coordinate photoelectric detection device 8 to the central position;

[0018] (2) adjusting the translation, height and azimuth position of the three-dimensional coordinate photoelectric detection device 8 through the base 7 of the three-dimensional coordinate photoelectric detection device 8 so that the light emission direction is roughly consistent with the direction of the long linear guide rail 12, and the laser emitted by the ranging laser 1 hits the light spot on the calibration target 10 on the long linear guide rail 12, and the distance from the center of the calibration target 10 is within 2 scale marks;

[0019] (3) The calibration target 10 consists of a grid scale with a spacing of 10 mm, concentric circles, and white dots with a black outer circle. The dot diameter is 6 mm, and the two dots are located at the center and +60 mm on the positive Y axis. The calibration target 10 is fixed on the two-dimensional adjustment stage 11, wherein the X-axis and Y-axis of the calibration target 10 are parallel to the two vertical axes of the two-dimensional adjustment stage 11.

[0020] (4) The two-dimensional adjustment table 11 is fixed on the sliding platform 9 of the long linear guide rail 12. The two axes of the two-dimensional adjustment table 11 are perpendicular to the axis of the long linear guide rail 12. One axis of the two-dimensional adjustment table 11 is horizontal. The motion range of the two axes is greater than 20 mm.

[0021] (5) Adjust the azimuth axis and pitch axis of the three-dimensional coordinate photoelectric detection device 8, and simultaneously adjust the two-dimensional adjustment table 11 on the calibration target 10, so that when the calibration target 10 moves from one end to the other along the long linear guide rail 12, the image center of the monitoring camera 2 in the three-dimensional coordinate photoelectric detection device 8 always coincides with the center of the dot at the origin on the calibration target 10. The image coordinates of the center dot of the calibration target 10 in the image are extracted by sub-pixel feature extraction algorithm. The coordinate change is within 0.5 pixels during the entire travel process, and the current azimuth axis α0 and pitch axis β0 of the three-dimensional coordinate photoelectric detection device 8 are recorded;

[0022] (6) Adjust the position of the calibration target 10 on the long linear guide rail 12 so that it is 1 m ± 100 mm away from the center of the azimuth rotation axis of the three-dimensional coordinate photoelectric detection device 8, and use the three-dimensional coordinate photoelectric detection device 8 to measure the distance d1 from the three-dimensional coordinate photoelectric detection device 8 to the calibration target 10;

[0023] (7) Set the focal length of the monitoring camera 2 in the three-dimensional coordinate photoelectric detection device 8 to the minimum value f min , take an image of the calibration target 10, extract the image coordinates (u1, v1) and (u2, v2) of two points on the calibration target 10 in the image by sub-pixel feature extraction algorithm, and calculate the distance d1' from the image coordinate system to the calibration target 10 by the ideal imaging model:

[0024]

[0025] Where pix is ​​the physical size of the surveillance camera pixel unit.

[0026] The distance Δd from the image coordinate system to the device coordinate system is calculated by the following formula:

[0027] Δd=d1'-d1(2)

[0028] (6) Turn on the ranging laser 1 indicating laser and set the focal length of the monitoring camera 2 of the three-dimensional coordinate photoelectric detection device 8 to the maximum value f max ;

[0029] (7) Restore the three-dimensional coordinate photoelectric detection device 8 to the azimuth axis α0 and the pitch axis β0, adjust the position of the calibration target 10 on the long linear guide rail 12 so that the distance between the three-dimensional coordinate photoelectric detection device 8 and the calibration target 10 is 1 / 3 of the measuring range of the three-dimensional coordinate photoelectric detection device 8, and use the three-dimensional coordinate photoelectric detection device 8 to measure the distance d2 from the three-dimensional coordinate photoelectric detection device 8 to the calibration target 10;

[0030] (8) Finely adjust the azimuth axis and pitch axis of the three-dimensional coordinate photoelectric detection device 8, and calculate the coordinates of the centroid of the laser spot in the image obtained by the observation monitoring camera 2. When the deviation between the centroid coordinates of the laser spot and the image center coordinates is less than 0.2 pixels, stop the adjustment and record the current azimuth axis α1 and pitch axis β1 of the three-dimensional coordinate photoelectric detection device 8;

[0031] (9) Restore the three-dimensional coordinate photoelectric detection device 8 to the azimuth axis α0 and the pitch axis β0, adjust the position of the calibration target 10 on the long linear guide rail 12 so that the distance from the three-dimensional coordinate photoelectric detection device 8 is the maximum range of the three-dimensional coordinate photoelectric detection device 8, and use the three-dimensional coordinate photoelectric detection device 8 to measure the distance d3 from the three-dimensional coordinate photoelectric detection device 8 to the calibration target 10;

[0032] (10) According to step 8, fine adjustment is made so that the deviation between the centroid coordinates of the laser spot and the image center coordinates is less than 0.2 pixels, and the current azimuth axis α2 and pitch axis β2 of the three-dimensional coordinate photoelectric detection device 8 are recorded;

[0033] (11) Then, at any distance d, different focal lengths f and azimuth angles α, the pixel distance of the laser spot emitted by the ranging laser 1 from the center of the image of the surveillance camera 2 is:

[0034]

[0035] (12) According to the above formula, the center of the overall image of the monitoring camera 2 is offset by (Δu, Δv), and then the original image is cut and displayed with this position as the center, so that the center of the displayed image always coincides with the center of the laser light spot emitted by the ranging laser 1, thereby realizing real-time correction of the imaging visual axis 3 and the laser ranging optical axis 6.

[0036] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

[0037] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. An adaptive optical axis and visual axis consistency correction method, characterized in that: include: S1. Calibrate the angle between the camera coordinate system and the laser coordinate system, use a standard long linear guide rail to adjust the image visual axis to be parallel to the guide rail axis, control the plane target of the vertical guide rail to move on the linear guide rail, take images at the closest working distance and the farthest working distance respectively, and record the distance values ​​at the two positions at the same time. Obtain the pixel coordinates of the laser point in the image through image processing, and calculate the spatial coordinates of the two light points in the camera coordinate system according to the camera imaging model through the focal length and pixel size parameters of the camera, and establish the linear equation of the laser axis in the camera coordinate system; S2. In the actual measurement process of applying optoelectronic equipment, the pixel coordinates of the laser spot at the current position that deviates from the center of the image can be solved based on the distance obtained by laser ranging, the actual focal length of the camera, and the pixel size, using the straight line equation of the laser axis. By cutting and displaying the original image with the laser point pixel coordinates as the center, real-time correction of the visual axis can be achieved.

2. The adaptive optical axis and visual axis consistency correction method according to claim 1, characterized in that: In S1, when calibrating the angle between the camera coordinate system and the laser coordinate system, first place a three-dimensional coordinate photoelectric detection device at one end of the long linear guide rail, set the azimuth axis of the three-dimensional coordinate photoelectric detection device to the 0° position, the pitch axis to the 0° position, and adjust the horizontal bubble of the three-dimensional coordinate photoelectric detection device to the central position.

3. The adaptive optical axis and visual axis consistency correction method according to claim 2, characterized in that: After adjusting the horizontal bubble of the three-dimensional coordinate photoelectric detection device to the central position, adjust the translation, height and azimuth position of the three-dimensional coordinate photoelectric detection device through the base of the three-dimensional coordinate photoelectric detection device so that the light output direction is consistent with the direction of the long linear guide rail, and the laser emitted by the ranging laser hits the light spot on the calibration target on the long linear guide rail, and the distance to the center of the calibration target is within 2 scale marks.

4. The adaptive optical axis and visual axis consistency correction method according to claim 3, characterized in that: The calibration target consists of a grid scale with fixed intervals, concentric rings, and white dots with a black outer ring, with two dots at the center and somewhere on the positive Y axis.

5. The adaptive optical axis and visual axis consistency correction method according to claim 3, characterized in that: The X-axis and Y-axis of the calibration target are parallel to the two perpendicular axes of the two-dimensional adjustment stage.

6. The adaptive optical axis and visual axis consistency correction method according to claim 3, characterized in that: When the laser emitted by the ranging laser hits the spot on the calibration target on the long linear guide rail and the distance to the center of the calibration target is within 2 scales, the two-dimensional adjustment table is fixed on the sliding platform of the long linear guide rail, and the two axes of the two-dimensional adjustment table are perpendicular to the axis of the long linear guide rail.

7. The adaptive optical axis and visual axis consistency correction method according to claim 6, characterized in that: After the two-dimensional adjustment table is fixed on the sliding platform of the long linear guide and the two axes of the two-dimensional adjustment table are perpendicular to the axis of the long linear guide, the azimuth axis and pitch axis of the three-dimensional coordinate photoelectric detection device are adjusted, and the two-dimensional adjustment table on the correction target is adjusted at the same time, so that when the correction target moves from one end to the other end along the long linear guide, the image center of the monitoring camera in the three-dimensional coordinate photoelectric detection device always coincides with the center of the circle at the origin on the correction target. The image coordinates of the center circle of the correction target in the image are extracted by sub-pixel feature extraction algorithm. The coordinate change is within 0.5 pixels during the entire stroke, and the current azimuth axis α0 and pitch axis β0 of the three-dimensional coordinate photoelectric detection device are recorded.

8. The adaptive optical axis and visual axis consistency correction method according to claim 7, characterized in that: After recording the current azimuth axis α0 and pitch axis β0 of the three-dimensional coordinate photoelectric detection device, adjust the position of the calibration target on the long linear guide rail so that it is 1m±100mm away from the azimuth axis center of the three-dimensional coordinate photoelectric detection device, and use the three-dimensional coordinate photoelectric detection device to measure the distance d1 from the three-dimensional coordinate photoelectric detection device to the calibration target; Set the focal length of the monitoring camera in the three-dimensional coordinate photoelectric detection device to the minimum value f min , take an image of the calibration target, extract the image coordinates (u1, v1) and (u2, v2) of two points on the calibration target in the image by sub-pixel feature extraction algorithm, and calculate the distance d1' from the image coordinate system to the calibration target by the ideal imaging model: Where pix is ​​the physical size of the surveillance camera pixel unit; The distance Δd from the image coordinate system to the device coordinate system is calculated by the following formula: Δd=d1'-d1 (2) Turn on the ranging laser indicator laser and set the focal length of the monitoring camera of the three-dimensional coordinate photoelectric detection device to the maximum value f max ; Restore the three-dimensional coordinate photoelectric detection device to the azimuth axis α0 and the pitch axis β0, adjust the position of the calibration target on the long linear guide rail so that the distance from the three-dimensional coordinate photoelectric detection device to the three-dimensional coordinate photoelectric detection device is 1 / 3 of the measuring range of the three-dimensional coordinate photoelectric detection device, and use the three-dimensional coordinate photoelectric detection device to measure the distance d2 from the three-dimensional coordinate photoelectric detection device to the calibration target; Finely adjust the azimuth and pitch axes of the three-dimensional coordinate photoelectric detection device, and calculate the coordinates of the centroid of the laser spot in the image obtained by the observation monitoring camera. When the deviation between the centroid coordinates of the laser spot and the image center coordinates is less than 0.2 pixels, stop the adjustment and record the current azimuth axis α1 and pitch axis β1 of the three-dimensional coordinate photoelectric detection device; Restore the three-dimensional coordinate photoelectric detection device to the azimuth axis α0 and the pitch axis β0, adjust the position of the correction target on the long linear guide rail so that the distance from the three-dimensional coordinate photoelectric detection device is the maximum range of the three-dimensional coordinate photoelectric detection device, and use the three-dimensional coordinate photoelectric detection device to measure the distance d3 from the three-dimensional coordinate photoelectric detection device to the correction target.

9. The adaptive optical axis and visual axis consistency correction method according to claim 8, characterized in that: After measuring the distance d3 from the three-dimensional coordinate photoelectric detection device to the calibration target, fine-tune it so that the deviation between the centroid coordinates of the laser spot and the image center coordinates is less than 0.2 pixels, and record the current azimuth axis α2 and pitch axis β2 of the three-dimensional coordinate photoelectric detection device; Then, at any distance d, different focal lengths f and azimuth angles α, the pixel distance of the laser spot emitted by the ranging laser from the center of the surveillance camera image is: According to the above formula, the center of the overall image of the surveillance camera is offset by (Δu, Δv), and then the original image is cut and displayed with this position as the center, so that the center of the displayed image always coincides with the center of the laser light spot emitted by the ranging laser, thereby realizing real-time correction of the imaging visual axis and the laser ranging optical axis.

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