CN116342710B

CN116342710B - Calibration method of binocular camera for laser tracker

Info

Publication number: CN116342710B
Application number: CN202310154505.2A
Authority: CN
Inventors: 张和君; 冯福荣; 吴兴发; 陈源; 廖学文
Original assignee: Chotest Technology Inc
Current assignee: Chotest Technology Inc
Priority date: 2023-02-10
Filing date: 2023-02-10
Publication date: 2024-01-30
Anticipated expiration: 2043-02-10
Also published as: CN118115598A; CN118172424A; CN116342710A

Abstract

The present disclosure describes a calibration method for a binocular camera of a laser tracker, the calibration method comprising: the binocular camera emits a first light beam, the first light beam is reflected by the target back to the first lens, the first light beam is converged to the first imaging element and first light spot data comprising a first component and a second component along the second component is obtained, the binocular camera emits a second light beam, the second light beam is reflected by the target back to the second lens, the second light beam is converged to the second imaging element and second light spot data comprising a third component and a fourth component is obtained; moving the target to change the distance between the target and the binocular camera; in the moving process of the target, acquiring a first component, a third component and the distance between the target and the binocular camera; the distance of the first lens and the second lens is calibrated based on the first component, the third component, the focal lengths of the first lens and the second lens, and preset device parameters of the first imaging element and the second imaging element.

Description

Calibration method of binocular camera for laser tracker

Technical Field

The present disclosure relates generally to the industry of intelligent manufacturing equipment, and more particularly to a calibration method for a binocular camera of a laser tracker.

Background

The basic principle of the laser tracker is that a target (also called a reflector or a target ball) is arranged on a to-be-measured point, a laser beam emitted by a laser tracking head of the laser tracker is emitted onto the target along a measuring optical axis of the laser tracker, the laser beam is reflected by the target and returns to the laser tracking head, and when the target moves, the laser tracker adjusts the direction of the laser beam to aim at the target. Meanwhile, the returned laser beam is received and identified by a detection system of the laser tracker and is used for measuring and calculating the spatial position of the target.

In the prior art, when a target deviates from the aiming optical axis of a laser tracker, the laser tracker can aim the target through a binocular camera, so that a position detector (also called a fine aiming unit) of the laser tracker receives a laser beam reflected by the target, thereby monitoring an effective laser beam signal, and the laser tracker can finely aim according to a coordinate signal of the target fed back by the position detector, track the locked target and measure the distance of the target.

Because various errors exist, before a target is aimed by using a binocular camera of a laser tracker, if the binocular camera is not calibrated, the measurement accuracy of the target aimed by the binocular camera is reduced, and the existing calibrating method is not suitable for the binocular camera of the laser tracker.

Disclosure of Invention

The present disclosure has been made in view of the above-described conventional circumstances, and an object thereof is to provide a method that is simple to operate and that can accurately calibrate a binocular camera of a laser tracker.

To this end, the present disclosure provides a calibration method of a binocular camera for a laser tracker including a measurement host capable of rotating around a first rotation axis and a second rotation axis and emitting a laser beam, and a binocular camera provided to the measurement host, the intersection point of the first rotation axis and the second rotation axis being a rotation center of the binocular camera, the direction in which the first rotation axis extends being a first direction, the direction in which the second rotation axis extends being a second direction, the calibration method comprising: the binocular camera emits a first light beam, the first light beam is received by a target and reflected back to the binocular camera, the first light beam reflected by the target is converged to a first imaging element of the binocular camera through a first lens of the binocular camera and first light spot data is obtained, the first light spot data comprises a first component along the second direction and a second component along the first direction, the binocular camera emits a second light beam, the second light beam is received by the target and reflected back to the binocular camera, the second light beam reflected by the target is converged to a second imaging element of the binocular camera through a second lens of the binocular camera and second light spot data is obtained, the second light spot data comprises a third component along the second direction and a fourth component along the first direction, and a connecting line of a light center of the first lens and a light center of the second lens is parallel to the second rotation axis; moving the target to change a distance of the target from the binocular camera; acquiring the first component, the third component and the distance between the target and the binocular camera in the moving process of the target; calibrating the distance between the first lens and the second lens based on the first component, the third component, the focal lengths of the first lens and the second lens, and preset device parameters of the first imaging element and the second imaging element.

In this embodiment, the first light beam and the second light beam emitted by the binocular camera may be used to obtain corresponding first light spot data and second light spot data, respectively, and based on the first component of the first light spot data and the third component of the second light spot data, a calculation formula of the distance between the target and the binocular camera may be obtained. In this case, the first component and the third component corresponding to the target can be obtained by placing the target at positions with different distances from the binocular camera, and the first linear equation can be obtained by using the linear fitting method.

In addition, in the calibration method according to the present embodiment, the target is optionally moved on a straight line where the laser beam is located to change the distance between the target and the binocular camera. In this case, the target is moved on a straight line where the laser beam is located to change the distance between the target and the binocular camera, that is, the target is moved on the sighting optical axis of the binocular camera, firstly, the movement of the target can be controlled more easily, and secondly, the target is moved on the sighting optical axis of the binocular camera, so that the influence caused by the deviation of the target relative to the sighting optical axis in the first direction and the second direction can be reduced, the distance between the target and the binocular camera can be determined more precisely by using the detection system of the laser tracker, and thus, the distance between the target and the binocular camera can be obtained simply and precisely, and therefore, the accuracy and precision of the calibration method can be improved.

In addition, in the calibration method according to the present embodiment, optionally, the method includes calibrating a first parameter configured to calculate, in cooperation with the first component and the third component, a first rotation angle of the measurement host about the first rotation axis with the rotation center as a center point when the laser tracker tracks the target, and the method for calibrating the first parameter includes: placing the target on a straight line where the laser beam is positioned; acquiring the first component and the third component; a first parameter is obtained based on the first component and the third component. In this case, since the first rotation angle when aiming the binocular camera at the target can be calculated by using the first parameter when aiming the target by using the binocular camera, the influence that the first rotation angle cannot be accurately calculated due to the parallax between the binocular camera and the aiming optical axis is reduced, and therefore, before aiming the target by using the binocular camera, the first parameter can be directly called by calibrating the binocular camera to obtain the first parameter, so that the rotation angle of the binocular camera required to rotate in the process of aiming the target can be accurately and conveniently calculated.

In addition, in the calibration method according to the present embodiment, optionally, the calculation formula of the first rotation angle is:

wherein α is the first rotation angle, u is preset equipment parameters of the first imaging element and the second imaging element, L is the distance from the rotation center to the binocular camera, D is the distance from the target to the binocular camera, f is the focal lengths of the first lens and the second lens, K is the first parameter, x ₁ And x ₂ Representing the first component and the third component, respectively. Thus, the angle at which the binocular camera needs to rotate along the first rotation axis with the rotation center as the center point in the process of aiming at the target can be calculated based on the formula of the first rotation angle.

In addition, in the calibration method according to the present embodiment, optionally, the method for calibrating the focal lengths of the first lens and the second lens includes: moving the target within a preset plane having a first preset distance from the binocular camera and relative to the binocular camera in a manner different from the second direction; enabling the target and the rotation center to form a preset position relation; acquiring the second component, the fourth component and a preset position relation between the target and the rotation center in the process of moving the target relative to the binocular camera in the preset plane along a mode different from the second direction; and calibrating focal lengths of the first lens and the second lens based on the preset position relation, a second preset distance from the rotation center to the binocular camera, the second component and the fourth component, and preset equipment parameters of the first imaging element and the second imaging element. In this case, by calibrating the focal lengths of the first lens and the second lens, the assembly error between the first lens and the first imaging element and the assembly error between the second lens and the second imaging element can be reduced, and thus, the rotation angle of the binocular camera, that is, the first rotation angle and the second rotation angle, which need to be rotated in the process of aiming at the target can be accurately and conveniently calculated according to the calibrated focal lengths of the first lens and the second lens.

In addition, in the calibration method according to the present embodiment, optionally, the preset positional relationship is that, in a process that the target moves in the preset plane along the first direction perpendicular to and intersecting with the line where the laser beam is located, a second rotation angle between a line connecting the target and the rotation center and the line where the laser beam is located is smaller than a preset angle. In this case, the target moves relative to the binocular camera in the first direction perpendicular to and intersecting with the line where the laser beam is located in the preset plane, so that the movement of the target relative to the binocular camera can be controlled more easily, the influence caused by the offset of the target relative to the sighting optical axis in the moving process of the target relative to the binocular camera can be reduced, and therefore, the first preset distance between the target and the binocular camera can be determined more precisely and the second rotation angle can be acquired precisely by using the detection system of the laser tracker.

In the calibration method according to the present embodiment, optionally, the second rotation angle has a second functional relationship:

wherein beta is _i In the process that the target moves relative to the binocular camera along the first direction perpendicular to and intersecting with the straight line of the laser beam in the preset plane, the second rotation angle acquired at the ith moment is L, D, and f, wherein L is the distance from the rotation center to the binocular camera, D is the distance from the target to the binocular camera, and f is the distance from the rotation center to the binocular cameraThe focal lengths of the first lens and the second lens, u is a preset equipment parameter of the first imaging element and the second imaging element, y _i And obtaining the average value of the second component and the fourth component at the ith moment in the process that the target moves relative to the binocular camera along the first direction which is perpendicular to and intersected with the straight line where the laser beam is positioned in the preset plane. Therefore, when the second rotation angle is smaller than the preset angle, the relation between a plurality of second rotation angles and a plurality of corresponding second components and fourth components can be obtained through the characteristic of the arctangent function atan, a second linear equation is obtained through calibration by using a linear fitting method, and the slope of the second linear equation can be used for calibrating The focal lengths of the first lens and the second lens can be calibrated based on the preset parameter L, D, u, and the calculation accuracy of the calibration method can be improved by calibrating the second linear equation by using the average value of the second component and the fourth component.

In addition, in the calibration method according to the present embodiment, optionally, the method includes calibrating a second parameter, where the second parameter is configured to calculate a distance from the target to the binocular camera in cooperation with the first component and the third component, and the method for calibrating the second parameter includes: the second parameter is calculated based on a distance of the first lens and the second lens, a focal length of the first lens and the second lens. Thus, in the process of aiming the binocular camera at the target, the binocular camera can directly call the second parameter for calculating the distance from the target to the binocular camera.

In addition, in the calibration method according to the present embodiment, optionally, the calibration method includes calibrating a third parameter configured as an offset of an image center of the first imaging element and an optical axis of the first lens in the second direction, and a fourth parameter configured as an offset of an image center of the second imaging element and an optical axis of the second lens in the second direction, and the method for calibrating the third parameter and the fourth parameter includes: the third parameter and the fourth parameter are obtained based on the first parameter and the second parameter. In this case, the third parameter and the fourth parameter can be calibrated based on the calibrated second parameter and the first parameter, the positional deviation between the optical axis of the first lens and the image center of the first imaging element and the positional deviation between the optical axis of the second lens and the image center of the second imaging element can be evaluated, and thus the third parameter and the fourth parameter are taken into consideration when the binocular camera is aimed at and calibrated, thereby the accuracy of the binocular camera is improved and the accuracy of the binocular camera is calibrated, and the production process of the laser tracker can be guided.

In addition, in the calibration method according to the present embodiment, optionally, a difference between the first component and the third component has a first functional relationship with a distance from the target to the binocular camera:

wherein D is _i In order to obtain the distance from the target to the binocular camera at the ith moment in the moving process of the target, f is the focal length of the first lens and the second lens, b is the second parameter, A is the distance between the first lens and the second lens, u is the preset equipment parameters of the first imaging element and the second imaging element, and x _i Is the difference between the first component and the third component at the i-th moment in the process of moving the target. In this case, by acquiring the first component and the third component in the position state of different distances of the target to the binocular camera, D can be based on _i And x _i The corresponding relation between the first lens and the second lens is calibrated to obtain a first linear equation, so that the distance between the first lens and the second lens can be calibrated based on the slope of the first linear equation and the first functional relation.

According to the present disclosure, a method that is easy to operate and that can accurately calibrate a binocular camera of a laser tracker can be provided.

Drawings

Fig. 1 is a schematic diagram showing a laser tracker according to an example of the present embodiment.

Fig. 2 is a schematic diagram showing a method of aiming a target based on a binocular camera according to an example of the present embodiment.

Fig. 3 is a schematic diagram showing the composition of the binocular camera according to the present embodiment example.

Fig. 4 is a schematic diagram showing an actual optical path of the binocular camera according to the present embodiment example.

Fig. 5 is a schematic diagram showing a first equivalent optical path of the binocular camera according to the present embodiment example.

Fig. 6 is a schematic diagram showing a first coordinate system and a second coordinate system according to an example of the present embodiment.

Fig. 7 is a schematic diagram showing a distance to a measurement target based on a binocular camera according to an example of the present embodiment.

Fig. 8 is a flow chart showing calibration of the distances of the first lens and the second lens according to the present embodiment example.

Fig. 9 is a schematic view showing an optical path for calibrating the first parameter according to the example of the present embodiment.

Fig. 10 is a flow chart showing calibration of the first parameter according to the example of the present embodiment.

Fig. 11 is a schematic view showing a first rotation angle according to an example of the present embodiment.

Fig. 12 is a schematic view showing a second rotation angle according to the present embodiment example.

Fig. 13 is a flow chart showing calibration of focal lengths of the first lens and the second lens according to the present embodiment example.

Fig. 14 is a schematic diagram showing calibration of focal lengths of the first lens and the second lens according to the present embodiment example.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that the terms "first," "second," "third," and "fourth," etc. in the description and claims of the present invention and in the above figures are used for distinguishing between different objects and not for describing a particular sequential order. Furthermore, the terms "comprise" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those listed steps or elements but may include other steps or elements not listed or inherent to such process, method, article, or apparatus. In the following description, the same members are denoted by the same reference numerals, and overlapping description thereof is omitted. In addition, the drawings are schematic, and the ratio of the sizes of the components to each other, the shapes of the components, and the like may be different from actual ones.

The present embodiment relates to a calibration method of a binocular camera for a laser tracker (hereinafter, may be simply referred to as "calibration method").

Fig. 1 is a schematic diagram showing a laser tracker 30 according to an example of the present embodiment. Fig. 2 is a schematic diagram showing a method of aiming at the target 20 based on the binocular camera 10 according to the present embodiment example.

In this embodiment, referring to fig. 1, the laser tracker 30 may include a measurement host 31 and a binocular camera 10 disposed on the measurement host 31. The working process of the laser tracker 30 aiming at the target 20 based on the binocular camera 10 may be that a target 20 (may also be called a "reflector" or a "target ball") is placed on a to-be-measured point, the measurement host 31 of the laser tracker 30 may emit a laser beam and may emit the laser beam onto the target 20 along the measurement optical axis of the laser tracker 30, the laser beam may be reflected by the target 20 and may return to the laser tracker 30, and at the same time, the returned laser beam is received and identified by the detection system of the laser tracker 30, so that the detection system of the laser tracker 30 can calculate the spatial distance and the position of the target 20. When the moving range of the target 20 is larger, the detection system of the laser tracker 30 cannot receive and identify the laser beam reflected back by the target 20, and then the laser tracker 30 can aim at the target 20 based on the binocular camera 10 arranged on the measuring host 31, and adjust the position and the posture of the measuring host 31 so that the target 20 is positioned on the aiming optical axis M of the binocular camera 10, that is, the target 20 is positioned on the line where the laser beam is positioned, so that the reflected laser beam can be received and identified by the detection system of the laser tracker 30, and further the detection system of the laser tracker 30 can calculate the spatial position of the target 20, wherein the aiming optical axis M of the binocular camera 10 can be the measuring optical axis of the laser tracker 30, that is, the line where the laser beam emitted by the laser tracker 30 is positioned.

In some examples, the detection system of the laser tracker 30 may include a laser interferometer and a laser absolute distance meter, which may be used to measure the distance D of the target 20 to the binocular camera 10. In this case, in the calibration method, the distance D of higher accuracy can be acquired with the detection system of the laser tracker 30, thereby facilitating the calculation of the verification method, and the process of setting the distance D (described later) can be simplified.

Referring to fig. 2, in some examples, the laser tracker 30 may further include a first rotation axis 13 and a second rotation axis 12, the first rotation axis 13 may extend in a first direction, that is, a Y-axis direction (may also be referred to as a "vertical direction") shown in fig. 2, and the second rotation axis 12 may extend in a second direction, that is, an X-axis direction (may also be referred to as a "horizontal direction") shown in fig. 2, and the measurement master 31, that is, the binocular camera 10 may rotate in a horizontal direction about the first rotation axis 13 and may rotate in a vertical direction about the second rotation axis 12, wherein an intersection point of the first rotation axis 13 and the second rotation axis 12 may be a rotation center 11 of the binocular camera 10.

In some examples, the first rotation axis 13, the second rotation axis 12, and the sighting optical axis M of the binocular camera 10 may be vertical in pairs, 20a may be a projection position of the target 20 in a plane formed by the sighting optical axis M and the second rotation axis 12, i.e., an X-axis direction (may also be referred to as a "horizontal direction") shown in fig. 2, and 20b may be a projection position of the target 20 in a plane formed by the sighting optical axis M and the first rotation axis 13, i.e., a Y-axis direction (may also be referred to as a "vertical direction") shown in fig. 2. In this case, in the process of aiming the binocular camera 10 at the target 20, that is, positioning the target 20 on the aiming optical axis M of the binocular camera 10, the binocular camera 10 may be rotated along the first and second rotation axes 13 and 12 with the rotation center 11 as a center point according to the first and second rotation angles α and β so that the target 20 is positioned on the aiming optical axis M.

Fig. 3 is a schematic diagram showing the composition of the binocular camera 10 according to the present embodiment example.

In some examples, the binocular camera 10 may include a first light source 15 to emit a first light beam 151, a second light source 16 to emit a second light beam 161, and an acquisition unit 17 to receive the first and second light beams 151, 161 reflected back by the target 20. In this case, the acquisition unit 17 can receive the first light beam 151 and the second light beam 161 reflected back from the target 20, and thus, the acquisition unit 17 can correspond to the first light spot 152 and first light spot data (described later) and the second light spot 162 and second light spot data (described later) of the second light beam 161 that form the first light beam 151.

In some examples, the acquisition unit 17 may include a first acquisition unit 171 and a second acquisition unit 172, the first acquisition unit 171 may have a first lens 1711 and a first imaging element 1712, and the second acquisition unit 172 may have a second lens 1721 and a second imaging element 1722 (see fig. 3). Thus, the first light beam 151 can be reflected off the target 20 to the first lens 1711, focused through the first lens 1711 onto the first imaging element 1712 as a first spot 152 and forming first spot data, and the second light beam 161 can be reflected off the target 20 to the second lens 1721, focused through the second lens 1721 onto the second imaging element 1722 as a second spot 162 and forming second spot data.

In some examples, the first lens 1711 and the second lens 1721 can lie in the same plane and the optical center of the first lens 1711 and the optical center of the second lens 1721 lie in the plane. Thereby facilitating the structural design of the binocular camera 10 and enabling a simpler calibration method.

In some examples, the line connecting the optical center of the first lens 1711 and the optical center of the second lens 1721 may be parallel to the second rotation axis 12. Thereby facilitating the structural design of the binocular camera 10 and enabling a simpler calibration method.

In some examples, the optical axis T1 of the first lens 1711 and the optical axis T2 of the second lens 1721 may be parallel and symmetrically distributed on both sides of the aiming optical axis M of the binocular camera 10. Thereby facilitating the structural design of the binocular camera 10 and enabling a simpler calibration method.

In some examples, the projections of the optical axis T1 of the first lens 1711 and the optical axis T2 of the second lens 1721 on the first rotation axis 13 may overlap, and the optical axis T1 and the optical axis T2 overlap with the projection of the sighting optical axis M on the first rotation axis 13. Thus, the structural design of the binocular camera 10 is facilitated, and the calibration method can be made simpler and more accurate.

In some examples, the first lens 1711 and the second lens 1721 may have the same focal length. Thus, the calibration method can be simplified.

In some examples, the first lens 1711 and the second lens 1721 may have different focal lengths. This can improve the adaptability of the binocular camera 10.

In some examples, the first and second imaging elements 1712, 1722 may include a photosensitive array (or referred to as a pixel array). The photosensitive array can be composed of a plurality of pixel points, and can convert received optical signals into electric signals for output. Thus, the first spot 152 and the first spot data, and the second spot 162 and the second spot data can be obtained.

In some examples, the photosensitive array of the first imaging element 1712 and the photosensitive array of the second imaging element 1722 can be CMOS photosensitive elements or CCD photosensitive elements.

In some examples, the photosensitive array of the first imaging element 1712 and the photosensitive array of the second imaging element 1722 may have the same preset device parameters. For example, the photosensitive array of the first imaging element 1712 and the photosensitive array of the second imaging element 1722 may have the same effective pixel array and pixel size, in other words, the photosensitive array of the first imaging element 1712 and the photosensitive array of the second imaging element 1722 may have the same number of pixels in the horizontal direction and the vertical direction, respectively, that is, may have the same total width of pixels. The size of each pixel dot may be the same, i.e., the width of each pixel dot in the horizontal direction and the vertical direction may be the same. Thus, the calibration method can be simplified, and the design of the binocular camera 10 is facilitated.

In some examples, the number of the first light sources 15 may be plural, the plurality of first light sources 15 may be arranged around the first acquisition unit 171, in particular, the plurality of first light sources 15 may be arranged around the first lens 1711, and the first spot data may be spot data obtained by a plurality of light spots obtained by a plurality of first light beams 151 emitted by the plurality of first light sources 15 being reflected by the target 20 and acquired by the first acquisition unit 171. In this case, since the plurality of first light sources 15 are arranged around the first acquisition unit 171, the spots formed by the plurality of first light sources 15 acquired by the first acquisition unit 171 are also in a surrounding shape, and the first spot data is calculated using the joint center of gravity of the plurality of spots, one first spot data with higher accuracy can be obtained, and thus, not only calculation can be simplified, but also calculation accuracy can be improved.

In some examples, the number of second light sources 16 may be plural, the plurality of second light sources 16 may be arranged around the second acquisition unit 172, in particular, the plurality of second light sources 16 may be arranged around the second lens 1721, and the second spot data may be spot data obtained by a plurality of light spots obtained by a plurality of second light beams 161 emitted by the plurality of second light sources 16 being reflected by the target 20 and acquired by the second acquisition unit 172. In this case, since the plurality of second light sources 16 are arranged around the second acquisition unit 172, the spots formed by the plurality of second light sources 16 acquired by the second acquisition unit 172 are also in a surrounding shape, and the second spot data is calculated using the combined center of gravity of the plurality of spots, one second spot data with higher accuracy can be obtained, and thus, not only calculation can be simplified, but also calculation accuracy can be improved.

In some examples, the combined center of gravity of the spots of the plurality of first spots 152 and/or the plurality of second spots 162 on the first imaging element 1712 and the second imaging element 1722, respectively, may be calculated using any one of a centroid tracking method, a grayscale centroid method, a circular fitting method, and a Hough transform method. This can improve the adaptability of the calculation method of the sighting target 20.

In some examples, the first light source 15 and the second light source 16 may be diffuse light sources. In particular, the first light source 15 and the second light source 16 may be infrared LED light sources having a light emission angle of 10-50 degrees, whereby the first light beam 151 and the second light beam 161 can be emitted in a large range, so that the probability of the object 20 reflecting the first light beam 151 and the second light beam 161 can be improved, and the field of view range of the binocular camera 10 can be enlarged.

In some examples, the field of view overlap range of the first light source 15 and the second light source 16 may be greater than the field of view range of the first acquisition unit 171 and the second acquisition unit 172. Thereby, the field of view of the binocular camera 10 can be further widened.

In some examples, the first light source 15 may be a plurality of infrared LED light sources symmetrically distributed on both sides of the first lens 1711. This can expand the field of view of the binocular camera 10.

In some examples, the second light source 16 may be a plurality of infrared LED light sources symmetrically distributed on both sides of the second lens 1721. This can further expand the field of view of the binocular camera 10.

Fig. 4 is a schematic diagram showing an actual optical path of the binocular camera 10 according to the present embodiment example, and fig. 5 is a schematic diagram showing a first equivalent optical path of the binocular camera 10 according to the present embodiment example. In this embodiment, for convenience in explaining the calibration method, the present disclosure may propose a first equivalent optical path as shown in fig. 5 based on the actual optical path of fig. 4.

In the present embodiment, the first lens 1711 and the second lens 1721 may be located in the same plane, specifically, the optical axis of the first lens 1711 and the optical axis of the second lens 1721 may be parallel, and the optical center of the first lens 1711 and the optical center of the second lens 1721 may be located in the same plane; the optical axis T1 of the first lens 1711 and the optical axis T2 of the second lens 1721 may be symmetrically distributed on two sides of the aiming optical axis M of the binocular camera 10, and a line connecting the optical center of the first lens 1711 and the optical center of the second lens 1721 may be parallel to the second rotation axis 12; the center of rotation 11 of the binocular camera 10 may be located on the aiming optical axis M, and the distance of the center of rotation 11 to the same plane in which the first lens 1711 and the second lens 1721 are located may have a second preset distance L; the distance between the first lens 1711 and the second lens 1721 can be represented by a distance a between the optical center of the first lens 1711 and the optical center of the second lens 1721 in the plane in which the first lens 1711 and the second lens 1721 lie; the parameters of the photosensitive array of the first imaging element 1712 and the photosensitive array of the second imaging element 1722 may have the same preset device parameters, e.g., the same total width of pixels, and the size of each pixel dot may be the same, i.e., the width of each pixel dot in the first direction and the second direction is the same; the first light source 15 may be two infrared LED light sources symmetrically distributed on both sides of the first lens 1711, that is, the first light source 15A and the first light source 15B shown in fig. 4, the second light source 16 may be two infrared LED light sources symmetrically distributed on both sides of the second lens 1721, that is, the second light source 16A and the second light source 16B shown in fig. 4, the first light source 15A and the first light source 15B may have corresponding virtual light sources 15A and 15B (see fig. 4) respectively, the two second light sources 16A and 16B may have corresponding virtual light sources 16A and 16B (see fig. 4) respectively, the virtual light sources 15A and 15B may be equivalent to the first virtual light source 153 shown in fig. 5, the virtual light sources 16A and 16B may be equivalent to the second virtual light source 163 shown in fig. 5, and the target 20 may be located at a midpoint position of the first virtual light source 153 of the first lens 1711, and the target 20 may be located at a midpoint position of the second virtual light source 163 of the second lens 1711. Thus, the design of the binocular camera 10 is facilitated, and the calibration method is conveniently calculated. The calibration method is described below with reference to the first equivalent optical path shown in fig. 5.

It should be noted that the setting of the positions and the partial parameters of the lens and the photosensitive array in the present disclosure should not be construed as limiting the method, for example, the focal lengths of the first lens 1711 and the second lens 1721 may be different, the first lens 1711 and the second lens 1721 may not be symmetrically disposed about the sighting optical axis M, and the photosensitive array may have different total pixel widths, in which case the following formulas may be adaptively modified.

Fig. 6 is a schematic diagram showing a first coordinate system C1 and a second coordinate system C2 according to the present embodiment example.

In some examples, referring to fig. 6, with the C-C direction in fig. 5 as the view direction, a first coordinate system C1 and a second coordinate system C2 may be established based on the first imaging element 1712 and the second imaging element 1722, respectively, the upper left corner of the first imaging element 1712 may be the origin O1 of the first coordinate system C1, the horizontal axis direction of the first coordinate system C1, that is, the X1 axis direction may be the second direction (may also be referred to as the "horizontal direction"), the longitudinal axis direction of the first coordinate system C1, that is, the Y1 axis direction may be the first direction (may also be referred to as the "vertical direction"), and the description of the first coordinate system C1 may be equally applicable to the second coordinate system C2 with reference to fig. 6, which is not repeated herein. In this case, the first spot data can be decomposed into a first component in the second direction and a second component in the first direction in the first coordinate system C1, and the second spot data can be decomposed into a third component in the second direction and a fourth component in the first direction in the second coordinate system C2, thereby facilitating calculation of the first spot data and the second spot data.

In some examples, the units of the horizontal and vertical axes of the first and second coordinate systems C1 and C2 may be the number of pixels, in other words, coordinates located in the first and second coordinate systems C1 and C2 may be expressed in terms of pixel offset.

In some examples, the lateral axis directions of the first coordinate system C1 and the second coordinate system C2 may coincide. Thus, the design of the binocular camera 10 is facilitated and the calibration method is made simpler.

In some examples, the first and second imaging elements 1712, 1722 may have the same overall pixel width, in other words, the first and second imaging elements 1712, 1722 may have the same overall pixel width in the lateral and longitudinal axis directions, and the width of each pixel point in the lateral and longitudinal axis directions may be the same, i.e., the first and second imaging elements 1712, 1722 shown in fig. 6 may have the same third preset distance W.

In addition, P1 and P2 in fig. 6 may represent the image centers of the first and second imaging elements 1712 and 1722, respectively, that is, the centers of the photosensitive elements of the first and second imaging elements 1712 and 1722.

In some examples, the first spot data may include a first component along the second direction and a second component along the first direction, where the first component may be a coordinate value of the first spot 152 in the X1 axis direction of the first coordinate system C1, in other words, the first component may be a pixel offset of the first spot 152 in the X1 axis direction, that is, the second direction, relative to the origin O1 of the first coordinate system C1, and the second component may be a pixel offset of the first spot 152 in the Y1 axis direction of the first coordinate system C1, that is, the first direction, relative to the optical axis T1 of the first lens 1711. Therefore, the format meaning of the first light spot data can be clearly defined, so that the calculation of the calibration method is facilitated.

In some examples, the second spot data may include a third component along the second direction and a fourth component along the first direction, where the third component may be a coordinate value of the second spot 162 in the X2 axis direction in the second coordinate system C2, in other words, the third component may be a pixel offset of the second spot 162 in the X2 axis direction of the second coordinate system C2, that is, the second direction relative to the origin O2 of the second coordinate system C2, and the fourth component may be a pixel offset of the second spot 162 in the Y2 axis direction, that is, the first direction relative to the optical axis T2 of the second lens 1721. Therefore, the format meaning of the second light spot data can be clearly defined, so that the calculation of the calibration method is facilitated.

Fig. 7 is a schematic diagram showing the measurement of the distance of the target 20 based on the binocular camera 10 according to the present embodiment example.

In some examples, referring to fig. 7, the distance between the target 20 and the binocular camera 10 may be represented by a distance D of the target 20 to the same plane in which the first lens 1711 and the second lens 1721 lie.

Referring to fig. 7, according to the similar trigonometric relationship, there is formula (1):

wherein d ₁ May be the distance, d, of the first spot 152 from the optical axis T1 of the first lens 1711 in the second direction, i.e. in the X1 axis direction in the first coordinate system C1 ₂ May be a distance of the second light spot 162 from the optical axis T2 of the second lens 1721 in the second direction, i.e., the X2 axis direction in the second coordinate system C2 (see fig. 6), f may be a focal length of the first lens 1711 and the second lens 1721, a may be a distance between the first lens 1711 and the second lens 1721, and a distance of the first virtual light source 153 and the second virtual light source 163 integrally moving in the second direction, i.e., the horizontal direction may be h due to the position of the target 20 moving relative to the sighting optical axis M.

The addition cancellation h of the two formulas in the above formula (1) gives formula (2):

accordingly, the distance D between the target 20 and the binocular camera 10 can be conveniently measured, and the spatial position of the target 20 relative to the binocular camera 10 can be also determined, so that the first rotation angle α and the second rotation angle β can be conveniently calculated.

When the focal lengths of the first lens 1711 and the second lens 1721 are different, the expression (3) can be expressed according to the triangular relationship:

referring to FIG. 6, x can be used ₁ And x ₂ Representing a first component and a third component, respectively, in other words x ₁ May be the X1 axis coordinate value, X of the first light spot data in the first coordinate system C1 ₂ May be an X2 axis coordinate value of the second spot data in a second coordinate system C2; at the same time, in order to improve the calculation accuracy of the method of aiming the target 20, the optical axis T1 of the first lens 1711 and the image center P1 of the first imaging element 1712 may be considered to have an offset b in the X1 axis direction in the first coordinate system C1, i.e., the second direction ₁ B can be represented by a third parameter ₁ The optical axis T2 of the second lens 1721 and the image center P2 of the second imaging element 1722 may be considered to have a preset offset b in the second coordinate system C2 along the X2 axis, i.e. the second direction ₂ B can be represented by a fourth parameter ₂ Wherein b when the optical axis T1 is located on the right side of the image center P1 ₁ Can be positive, otherwise b ₁ Can be negative, and likewise, b when the optical axis T2 is located to the right of the image center P2 ₂ Can be positive, otherwise b ₂ Can be negative; the first and second imaging elements 1712, 1722 may have the same preset device parameters, e.g., may have the same total width of pixels, and are represented by a third preset distance W, the preset width of each pixel point of the first and second imaging elements 1712, 1722 in the horizontal and vertical directions being represented by u, which may be in millimeters mm or other units of length, thereby obtaining equation (4):

let b=b ₂ -b ₁ Formula (2) can be converted to formula (5):

let x _i ＝x ₁ -x ₂ Equation (5) can be equivalently converted to equation (6), resulting in a first functional relationship:

wherein D is _i May be the distance from the target 20 to the binocular camera 10 at the ith moment in time during the movement of the target 20, f may be the focal lengths of the first lens 1711 and the second lens 1721, b may be the second parameter, a may be the distance of the first lens 1711 and the second lens 1721, u may be the preset device parameters of the first imaging element 1712 and the second imaging element 1722, i.e., u may be the preset width of each pixel point of the first imaging element 1712 and the second imaging element 1722 in the horizontal direction and the vertical direction, x _i May be the difference between the first component and the third component at the i-th moment in time during the movement of the object 20. In this case, by acquiring the first component and the third component in the position state of different distances of the target to the binocular camera, D can be based on _i And x _i The corresponding relation between the first lens and the second lens is calibrated to obtain a first linear equation, so that the distance between the first lens and the second lens can be calibrated based on the slope of the first linear equation and the first functional relation.

Fig. 8 is a schematic diagram showing a flow of calibrating the distance a of the first lens 1711 and the second lens 1721 according to the present embodiment example.

In some examples, the distance a of the first lens 1711 and the second lens 1721 may be calibrated based on equation (6), i.e., the first functional relationship.

In some examples, referring to fig. 8, a method of calibrating a distance a of a first lens 1711 and a second lens 1721 may include: the first beam 151 is emitted, and the first spot data is obtained by using the first beam 151, the second beam 161 is emitted, and the second spot data is obtained by using the second beam 161 (step S100), the target 20 is moved to change the distance D of the target 20 from the binocular camera 10 (step S200), the first component, the third component, and the distance D of the target 20 from the binocular camera 10 are acquired (step S300), and the distances a of the first lens 1711 and the second lens 1721 are calibrated (step S400).

In step S100, the binocular camera 10 may emit a first light beam 151 and a second light beam 161, the first light beam 151 may be received by the target 20 and reflected back to the binocular camera 10, the first light beam 151 reflected by the target 20 may be converged to the first imaging element 1712 of the binocular camera 10 through the first lens 1711 of the binocular camera 10 and obtain first spot data, the second light beam 161 may be received by the target 20 and reflected back to the binocular camera 10, the second light beam 161 reflected by the target 20 may be converged to the second imaging element 1722 of the binocular camera 10 through the second lens 1721 of the binocular camera 10 and obtain second spot data, wherein the first spot data may include a first component in the second direction and a second component in the first direction, and the second spot data may include a third component in the second direction and a fourth component in the first direction.

In step S200, the target 20 may be moved to change the distance D of the target 20 from the binocular camera 10.

In some examples, the distance D in step S200 may take a preset data set, and the target 20 may be moved to the preset distance D. Thus, first spot data and second spot data corresponding to positions of the target 20 at different distances D can be obtained.

In some examples, the distance D may be obtained by a detection system of the laser tracker 30. In this case, the detection system of the laser tracker 30 can acquire the distance D in real time as the target 20 moves, and thus, the distance D can be more accurately determined and the calibration efficiency can be improved.

In some examples, the target 20 may be moved to the preset distance D by a human. Thereby, it is possible to adapt to the accurate calibration of the measuring range over short distances, e.g. less than 20 meters.

In some examples, the target 20 may also be moved by an automated movement device. Therefore, the method can be suitable for the accurate calibration of the measuring range of long distance, such as 20 meters to 60 meters.

In some examples, the target 20 may be moved on a line along which the laser beam is located to change the distance D of the target 20 from the binocular camera 10, in other words, the target 20 may be moved on the aiming optical axis M of the binocular camera 10 to obtain the distance D of the target 20 from the binocular camera 10. In this case, the target 20 is moved on a straight line where the laser beam is located to change the distance D between the target 20 and the binocular camera 10, that is, the target 20 is moved on the sighting optical axis M of the binocular camera 10, firstly, the movement of the target 20 can be more easily controlled, and secondly, the target 20 is moved on the sighting optical axis M of the binocular camera 10, so that the influence of the deviation of the target 20 with respect to the sighting optical axis M in the first and second directions can be reduced, the distance between the target 20 and the binocular camera D can be more precisely determined by using the detection system of the laser tracker 30, and thus the distance between the target 20 and the binocular camera 10 can be simply and precisely obtained, and thus, the accuracy and precision of the calibration method can be improved.

In step S300, during the movement of the target 20, the first component, the third component, and the distance D of the target 20 from the binocular camera 10 may be acquired. In this case, with the straight line fitting method, it is possible to base the distance D from the target 20 to the binocular camera 10 at the i-th timing _i And x _i The corresponding relation between the first linear equation and the second linear equation is obtained, so that the variable in the first functional relation can be calibrated according to the first linear equationAnd->

In some examples, the straight line fitting method may include any one of least squares, gradient descent, gauss newton.

In step S400, the distance a of the first lens 1711 and the second lens 1721 may be calibrated based on the first component, the third component, the focal lengths f of the first lens 1711 and the second lens 1721, and the preset device parameters u of the first imaging element 1712 and the second imaging element 1722. In this case, the identification can be based on the identification in step S300Is calibrated to the distance a of the first lens 1711 and the second lens 1721.

In some examples, the first linear equation may be obtained by implementing a linear fit through preset software. Therefore, the efficiency, convenience and accuracy of the calibration method can be improved.

In the present embodiment, corresponding first and second spot data may be obtained by the first and second light beams 151 and 161 emitted from the binocular camera 10, respectively, and based on the first and third components of the first and second spot data, a calculation formula (5) of the distance D of the target 20 from the binocular camera 10 may be obtained, and a formula (6) may be obtained based on the formula (5). In this case, the first component and the third component corresponding to the target 20 can be obtained by placing the target 20 at different distances D from the binocular camera 10, and the first linear equation can be obtained by using the linear fitting method, and since the slope of the first linear equation is associated with the distance a between the first lens 1711 and the second lens 1721, the distances between the first lens 1711 and the second lens 1721 can be calibrated based on the first linear equation, so that the measurement accuracy of the binocular camera aiming target can be improved, and the distance a between the first lens 1711 and the second lens 1721 can be directly called for accurately and conveniently calculating the rotation angles, that is, the first rotation angle α and the second rotation angle β, of the binocular camera 10 that need to be rotated in the aiming target 20.

In some examples, the calibration method may include calibrating a second parameter b, which may be configured to calculate the distance D of the target 20 to the binocular camera 10 in cooperation with the first and third components. Thus, during the aiming of the binocular camera 10 at the target 20, the binocular camera 10 can directly call the second parameter b and calculate the distance D of the target 20 to the binocular camera 10 based on equation (5).

In some examples, the method for calibrating the second parameter b may include: the second parameter b is calculated based on the distance a of the first lens 1711 and the second lens 1721, the focal length f of the first lens 1711 and the second lens 1721. In this case, based on the distance a of the first lens 1711 and the second lens 1721, the focal length f of the first lens 1711 and the second lens 1721, the first imaging element 1712, and the second imaging element 1722, the preset equipment parameter u is calibrated in step S300Can be calibrated to obtain the second parameter b.

In some examples, the variables in the first linear equation and the first functional relationship calibrated in step S300 may also be based onAnd->The value Guan Jibiao therebetween defines a second parameter b.

Fig. 9 is a schematic view of an optical path showing the calibration first parameter K according to the present embodiment example, and fig. 10 is a schematic view of a flow chart showing the calibration first parameter K according to the present embodiment example.

In some examples, the calibration method may further include calibrating a first parameter K, where the first parameter K may be configured to calculate, in conjunction with the first component and the third component, a first rotation angle α of the binocular camera 10 about the first rotation axis 13 with the rotation center 11 as a center point when the laser tracker 30 tracks the target 20.

In some examples, referring to fig. 9, the optical axis T1 of the first lens 1711 and the optical axis T2 of the second lens 1721 may be parallel and may be symmetrically distributed on both sides of the aiming optical axis M of the binocular camera 10, and the target 20 is placed on a line where the laser beam is located, that is, the target 20 is placed on the aiming optical axis M of the binocular camera 10, referring to fig. 9, may have formula (7):

d ₁ ＝d ₂

in connection with fig. 6, there is formula (8):

from this, formula (9) can be obtained:

x ₁ +x ₂ ＝W+b ₁ +b ₂

in other words, when the target 20 is placed at an arbitrary position on the line where the laser beam is located, that is, when the target 20 is placed at an arbitrary position D on the sighting optical axis M, the first component of the first spot data and the third component of the second spot data may both satisfy the following formula (10):

K＝x ₁ +x ₂ ＝W+b ₁ +b ₂

the third preset distance W in the formula (10) can be a preset fixed value, and the third parameter b ₁ And fourth parameter b ₂ May be obtained by calibrating the binocular camera 10, or may consider the third parameter b during the aiming of the binocular camera 10 at the target 20 ₁ And fourth parameter b ₂ It may be left unchanged, in other words, the target 20 may be positioned on the sighting optical axis M, and the first parameter K may be calibrated based on the sum of the first component of the first spot data and the third component of the second spot data. In this case, since the first rotation angle α when aiming the binocular camera 10 at the target 20 can be calculated using the first parameter K when aiming the target 20 using the binocular camera 10, thereby reducing the influence that the first rotation angle α cannot be accurately calculated due to the parallax between the binocular camera 10 and the aiming optical axis M, the binocular camera 10 is calibrated to obtain the first parameter K before aiming the target 20 using the binocular camera 10, and the calibrated first parameter K can be directly called, thereby accurately and conveniently calculating the first rotation angle α of the binocular camera 10 that needs to be rotated in the process of aiming the target 20.

In some examples, according to the calculation process of equation (10) above, referring to fig. 10, the method of calibrating the first parameter K may include: the target 20 is placed on a straight line where the laser beam is located (step T100), the first component and the third component are acquired (step T200), and the first parameter K is obtained based on the first component and the third component (step T300).

In step T100, the target 20 may be placed on the line on which the laser beam is located, i.e. the target 20 is placed on the aiming optical axis M of the binocular camera 10. Thus, the first parameter K can be specified based on the equation (10).

In step T200, a first component and a third component of the target 20 when placed on the sighting optical axis M of the binocular camera 10 are acquired.

In step T300, the first parameter K may be obtained based on the first component and the third component.

In some examples, the target 20 may be placed at different positions on the aiming optical axis M of the binocular camera 10, so as to obtain a plurality of corresponding first components and third components, and a corresponding plurality of first parameters K may be calculated based on the equation (10), and an average value of the plurality of first parameters K may be taken as the first parameters K. Thereby, the first parameter K of higher accuracy can be obtained.

In some examples, the calibration method may further include calibrating the third parameter b ₁ And fourth parameter b ₂ Calibrating the third parameter b ₁ And fourth parameter b ₂ The method for calibrating can comprise the following steps: obtaining a third parameter b based on the first parameter K and the second parameter b ₁ And fourth parameter b ₂ Wherein the third parameter b ₁ May be configured as an offset of the image center P1 of the first imaging element 1712 from the optical axis T1 of the first lens 1711 in the second direction, a fourth parameter b ₂ May be configured as an offset of the image center P2 of the second imaging element 1722 from the optical axis T2 of the second lens 1721 in the second direction.

In the present embodiment, in the third parameter b ₁ And fourth parameter b ₂ In the calibration process of (2), the formula (11) can be:

in this case, the third parameter b can be calibrated based on the calibrated second parameter b and the first parameter K ₁ And fourth parameter b ₂ The positional deviation between the optical axis T1 of the first lens 1711 and the image center P1 of the first imaging element 1712 and the positional deviation between the optical axis T2 of the second lens 1721 and the image center P2 of the second imaging element 1722 can be evaluated, whereby the third parameter b is taken into account during aiming of the binocular camera 10 at the target 20 and when calibrating the binocular camera 10 ₁ And fourth parameter b ₂ Thereby, the accuracy of aiming the binocular camera 10 at the target 20 and the accuracy of calibrating the binocular camera 10 can be improved, and the production process of the laser tracker 30 can be guided.

Fig. 11 is a schematic diagram showing a first rotation angle α according to the present embodiment example.

In some examples, referring to fig. 11, the first rotation angle α may be calculated based on the first component, the third component, the distance D between the target 20 and the binocular camera 10, the second preset distance L, the focal lengths f of the first and second lenses 1711 and 1721, and the first parameter K. Thereby, the first rotation angle α can be calculated easily. As shown in fig. 11, when the target 20 deviates from the aiming optical axis M of the binocular camera 10, the target 20 may have a first rotation angle α in a second direction, i.e., a lateral axis direction of the first coordinate system C1 and the second coordinate system C2, with respect to the rotation center 11 of the binocular camera 10, i.e., formula (12)

The relation (1) can be given by the formula (13):

by combining the expression (12) and the expression (13), a first rotation angle α of the measurement host 31, that is, the binocular camera 10 about the first rotation axis 13 with the rotation center 11 as a center point, that is, the expression (14):

where u may be the preset device parameters u, L of the first and second imaging elements 1712, 1722 may be a second preset distance from the center of rotation 11 of the binocular camera 10 to the binocular camera 10, D may be the distance from the target 20 to the binocular camera 10, f may be the focal lengths of the first and second lenses 1711, 1721, K may beTaking the first parameter, x ₁ And x ₂ The first component and the third component may be represented separately. Thus, the angle at which the binocular camera 10 needs to rotate about the rotation center 11 as a center point along the first rotation axis 13 in the process of aiming the target 20 can be calculated based on the formula of the first rotation angle α.

Fig. 12 is a schematic diagram showing a second rotation angle β according to the present embodiment example.

For the convenience of description of the calculation process, the projection is performed in the direction of the B-B view shown in fig. 5, so that the second equivalent optical path shown in fig. 12 proposed in the present disclosure may be obtained, in other words, the optical path of the first acquisition unit 171 may be projected in the first direction, that is, in the vertical direction, so that the second equivalent optical path shown in fig. 12 may be obtained. The second equivalent optical path may include the first lens 1711 and the first imaging element 1712, the optical axis T1 of the first lens 1711 may be a projection of the aiming optical axis M of the binocular camera 10 in a first direction, the optical axis T1 of the first lens 1711 may overlap with the projection of the aiming optical axis M in the first direction, the optical axis T1 of the first lens 1711 represented by the aiming optical axis M in fig. 12 may be an offset distance of the first light spot 152 in the first direction, i.e., a vertical direction, relative to the aiming optical axis M, and h1 may be an offset distance of the target 20 in the first direction, i.e., a vertical direction, relative to the aiming optical axis M, and the distance between the center of rotation 11 and the first lens 1711 may be a second preset distance L.

It should be noted that, the second equivalent optical path of the present disclosure may also be projected in the opposite direction of the B-B view direction shown in fig. 5 to obtain the second equivalent optical path with the second acquisition unit 172 as a component.

In some examples, when the target 20 deviates from the aiming optical axis M of the binocular camera 10, the target 20 may have a second angle of rotation β in a first direction, i.e., in the direction of the longitudinal axes of the first and second coordinate systems C1, C2, relative to the center of rotation 11 of the binocular camera 10. This makes it possible to obtain the second rotation angle β by which the binocular camera 10 needs to rotate about the second rotation axis 12 in the first direction with the rotation center 11 as the center point in the process of aiming the target 20.

Referring to fig. 12, from the trigonometric function, the second rotation angle β, that is, equation (15), can be derived:

from the similar triangle formula, equation (16) can be derived:

referring to FIG. 6, y can be used ₁ And y ₂ Representing a second component of the first spot data in the first coordinate system C1 and a fourth component of the second spot data in the second coordinate system C2, respectively. In some examples, the projections of the optical axis T1 of the first lens 1711 and the optical axis T2 of the second lens 1721 in the first direction may overlap the sighting optical axis M, i.e., there may be no parallax with the sighting optical axis M in the first direction of the optical axis T1 of the first lens 1711 and the optical axis T2 of the second lens 1721. The second rotation angle β can thus be calculated in the following manner.

In some examples, the second rotation angle β may be calculated based on the second component of the first spot data in a second equivalent optical path as shown in fig. 12 projected in the B-B view direction as shown in fig. 5. In this case, the formula (17) can be obtained: d=uy ₁ From this, formula (18) can be calculated by combining formula (17) and formula (16):

namely, the second rotation angle β:

in some examples, the second rotation angle β may be calculated based on a fourth component of the second spot data in projecting with a view direction opposite to B-B shown in fig. 5 to obtain a second equivalent optical path. In this case, the formula (19) can be obtained: d=uy ₂ From this, formula (20) can be calculated by combining formula (19) and formula (16):

namely, the second rotation angle β:

in some examples, the second rotation angle β may be calculated based on an average of the second component of the first spot data and the fourth component of the second spot data, and equation (21) may be obtained:

in this case, since there is no parallax between the optical axis T1 of the first lens 1711 and the optical axis T2 of the second lens 1721 and the sighting optical axis M in the first direction, the target 20 is located at an arbitrary position within the fields of view of the first lens 1711 and the second lens 1721, the second rotation angle β calculated based on the second component of the first spot data and the second rotation angle β calculated based on the fourth component of the second spot data can be substantially identical, whereby the distance d can be reduced to an average value of the second component and the fourth component, and thus the calculation accuracy of the calibration method can be improved.

From this, the formula (22) can be derived

Where L may be a second preset distance from the rotation center 11 to the binocular camera 10, D may be a first preset distance from the target 20 to the binocular camera 10, f may be focal lengths of the first lens 1711 and the second lens 1721, u may be preset device parameters of the first imaging element 1712 and the second imaging element 1722, y ₁ And y ₂ And may be a second component and a fourth component.

Fig. 13 is a schematic diagram showing a flow of calibrating the focal lengths f of the first lens 1711 and the second lens 1721 according to the present embodiment example, and fig. 14 is a schematic diagram showing the focal lengths f of the first lens 1711 and the second lens 1721 according to the present embodiment example.

In some examples, the focal length f of the first lens 1711 and the second lens 1721 can be calibrated based on any one of the formulas (18), (20), and (22) above.

In some examples, referring to fig. 13, a method of calibrating the focal length f of the first lens 1711 and the second lens 1721 can include: moving the target 20 in a different manner from the second direction in a preset plane E having a first preset distance D from the binocular camera 10 (step Y100), forming a preset positional relationship between the target 20 and the rotation center 11 (step Y200), acquiring a second component, a fourth component, and a preset positional relationship between the target 20 and the rotation center 11 (step Y300), and calibrating focal lengths f of the first lens 1711 and the second lens 1721 (step Y400). In this case, by calibrating the focal lengths f of the first lens 1711 and the second lens 1721, the assembly error between the first lens 1711 and the first imaging element 1712 and the assembly error between the second lens 1721 and the second imaging element 1722 can be reduced, and thus, the rotation angles of the binocular camera 10, that is, the first rotation angle α and the second rotation angle β, which need to be rotated in the process of aiming the target 20 can be accurately and conveniently calculated according to the calibrated focal lengths f of the first lens 1711 and the second lens 1721.

In step Y100, the target 20 may be moved relative to the binocular camera 10 in a different manner than the second direction within a preset plane E having a first preset distance D from the binocular camera 10, wherein the preset plane E may be perpendicular to the sighting optical axis M and spaced from the plane in which the first lens 1711 and the second lens 1721 lie by the first preset distance D (see fig. 13). In this case, when the focal lengths f of the first lens 1711 and the second lens 1721 are calibrated, the first preset distance D can be a fixed value, and the moving direction of the target 20 relative to the binocular camera in the preset plane E does not overlap with the second direction, in other words, when the target 20 moves relative to the binocular camera in the preset plane E, the second component and the fourth component corresponding to the different second rotation angle β state can be obtained, and if the target 20 moves relative to the binocular camera 10 along the second direction, the second component and the fourth component corresponding to the different second rotation angle β state cannot be obtained, that is, the focal lengths f of the first lens 1711 and the second lens 1721 cannot be calibrated.

In some examples, the target 20 may be positioned at the sighting optical axis M of the binocular camera 10, i.e., the target 20 is placed in an initial position on the line of the laser beam. Therefore, the detection system of the laser tracker 30 can directly calculate the distance D from the target 20 to the binocular camera 10, so that the preset plane E does not need to be prepared in advance, the verification method can be more flexible, the initial position is taken as the position for starting verification, and the second component and the fourth component corresponding to different second rotation angles β can be conveniently obtained and recorded.

In some examples, the target 20 may be positioned on the sighting optical axis M of the binocular camera 10 and held stationary, and the binocular camera 10 may be rotated in a vertical direction to obtain a plurality of second and fourth components at a different plurality of second rotational angles β. Therefore, the detection system of the laser tracker 30 can directly measure the distance D from the target 20 to the binocular camera 10, so that the preset plane E does not need to be prepared in advance, the verification method can be more flexible, the mode of relatively moving the target 20 and the binocular camera 10 is easier to control, and more accurate second rotation angles beta and corresponding second components and fourth components can be obtained.

In some examples, the target 20 may be located on the aiming optical axis M of the binocular camera 10, and the binocular camera 10 may be kept stationary, and the target 20 may be moved in a different manner from the second direction in the preset plane E to obtain a plurality of second rotation angles β and a corresponding plurality of second and fourth components.

In step Y200, the target 20 and the rotation center 11 are brought into a predetermined positional relationship.

In some examples, referring to fig. 14, the preset positional relationship in step Y200 may be that, in the process that the target 20 moves relative to the binocular camera 10 in the preset plane E along the first direction (the Y-axis direction in the preset plane E) perpendicular to and intersecting the line where the laser beam is located, the second rotation angle β between the line where the target 20 and the rotation center 11 is located and the line where the laser beam is located, that is, the sighting optical axis M, may be smaller than the preset angle, in other words, the second rotation angle β between the line where the target 20 and the rotation center 11 is located and the sighting optical axis M in the preset plane E along the first direction perpendicular to and intersecting the sighting optical axis M may be smaller than the preset angle, in other words, the target 20 may move by h1 distance in the first direction relative to the sighting optical axis M in the case that the first preset distance D is a fixed value, and the second rotation angle β between the line where the target 20 and the rotation center 11 is located and the sighting optical axis M may be smaller than the preset angle, in other words, the second rotation angle β between the target 20 and the sighting optical axis M may be smaller than the preset angle in radian, which may not be the preset angle. In this case, the target 20 is moved relative to the binocular camera 10 in a first direction perpendicular to and intersecting the straight line of the laser beam in the preset plane E, so that the movement of the target 20 relative to the binocular camera 10 can be controlled more easily, the influence caused by the offset of the target 20 relative to the sighting optical axis M during the movement of the target 10 can be reduced, and thus the first preset distance D between the target 20 and the binocular camera 10 and the second rotation angle β can be determined more precisely by using the detection system of the laser tracker 30, and in addition, when the second rotation angle β is smaller than the preset angle, the arctangent function atan can have a characteristic of an approximate straight line, and the relationship between the plurality of second rotation angles β and the corresponding plurality of second and fourth components can be obtained by using the characteristic of the arctangent function atan (see equation (23) described later), and the second straight line equation, that is, the relationship between the second rotation angle β and the second and fourth components can be calibrated by using the straight line fitting method, and the first equation of the second straight line 1721 can be obtained in combination with the calculation of the second rotation angle β and the calibrated slope of the second straight line.

In some examples, when the second rotation angle β is smaller than the preset angle, the following formula (23), that is, the second functional relationship, can be derived according to the characteristics of the arctangent function atan:

wherein beta is _i Can be the second rotation angle beta obtained at the ith moment in the process that the target 20 moves relative to the binocular camera 10 along the first direction perpendicular to and intersecting with the straight line of the laser beam in the preset plane E _i L may be a second preset distance from the rotation center 11 to the binocular camera 10, D may be a first preset distance from the target 20 to the binocular camera 10, that is, a distance between the binocular camera 10 and the preset plane E, f may be focal lengths to be calibrated of the first lens 1711 and the second lens 1721, u is a preset device parameter of the first imaging element 1712 and the second imaging element 1722, y _i The average of the second and fourth components taken at the i-th moment during the movement of the object 20 relative to the binocular camera 10 in a different manner than the second direction within the preset plane E may be taken. Therefore, when the second rotation angle beta is smaller than the preset angle, the relation between a plurality of second rotation angles and a plurality of corresponding second components and fourth components can be obtained through the characteristic of the arctangent function atan (see formula (23)), and a second linear equation can be obtained through calibration by using a linear fitting method, and further the slope of the second linear equation can be used for calibrating The focal lengths f of the first lens 1711 and the second lens 1721 can be calibrated based on the preset parameter L, D, u, and the calculation accuracy of the calibration method can be improved by calibrating the second linear equation using the average value of the second component and the fourth component.

In some examples, y in formula (23) _i The second component or the fourth component acquired at the i-th moment during the movement of the object 20 relative to the binocular camera 10 in a different manner than the second direction within the preset plane E may be used. In this case, focal lengths respectively calibrating the first lens 1711 and the second lens 1721 can be calibrated based on the second component or the fourth component.

It should be noted that, in the preset positional relationship described in the present specification, a specific track of the movement of the object 20 relative to the binocular camera 10 is not limited, and the object 20 may also move relative to the binocular camera 10 in any direction different from the second direction within the preset plane E.

In step Y300, the second component, the fourth component, and the preset positional relationship between the target 20 and the rotation center 11 during the movement of the target 20 relative to the binocular camera 10 in a manner different from the second direction in the preset plane E may be acquired. In this case, the second linear equation can be fitted based on the second rotation angle β and its corresponding second and fourth components in the preset positional relationship of the target 20 and the rotation center 11 using any one of the linear fitting methods, for example, the least square method, the gradient descent method, and the gauss newton method.

In step Y400, the focal lengths f of the first lens 1711 and the second lens 1721 may be calibrated based on the above-described preset positional relationship, the second preset distance L from the rotation center 11 to the binocular camera 10, the second and fourth components, and the preset device parameters u of the first and second imaging elements 1712 and 1722. In this case, based on the slope of the second linear equation obtained in step Y200, it is possible to calibrate outThereby enabling the focal length f of the first lens 1711 and the second lens 1721 to be calibrated based on the first preset distance D, the second preset distance L, the preset device parameters u of the first imaging element 1712 and the second imaging element 1722.

In some examples, the focal lengths of the first lens 1711 and the second lens 1721 may be different. In this case, when the focal length of the first lens 1711 is calibrated, a linear equation relation between the second rotation angle β and its corresponding second component can be obtained using a linear fitting method based on the above-described steps. Thus, the focal length of the first lens 1711 can be obtained by combining equation (18). Similarly, a linear equation relation between the second rotation angle β and the fourth component corresponding thereto can be obtained by using a linear fitting method, and the focal length of the second lens 1721 can be obtained by combining equation (20) and calibration.

In the present specification, the directions of the preset angle, the first rotation angle α, and the second rotation angle β are not limited, that is, the binocular camera 10 can rotate bidirectionally about the first rotation axis 13 and the second rotation axis 12.

Various embodiments of the present invention are described above in the detailed description. While the description directly describes the above embodiments, it should be understood that modifications and/or variations to the specific embodiments shown and described herein will occur to those skilled in the art. Any such modifications or variations that fall within the scope of this disclosure are intended to be included therein. Unless specifically indicated otherwise, the inventors intend that words and phrases in the specification and claims be given the ordinary and accustomed meaning of a person of ordinary skill.

The foregoing description of various embodiments of the invention that are known to the applicant at the time of filing this application have been presented and are intended for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and many modifications and variations are possible in light of the above teaching. The embodiments described are provided to explain the principles of the invention and its practical application and to enable others skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed for carrying out this invention.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings of this invention, changes and modifications may be made without departing from this invention and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of this invention. It will be understood by those within the art that, in general, terms used herein are generally intended to be "open" terms (e.g., the term "comprising" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "comprising" should be interpreted as "including but not limited to," etc.).

Claims

1. The calibration method for the binocular camera of the laser tracker comprises a measuring host machine capable of rotating around a first rotating shaft and a second rotating shaft and emitting laser beams and the binocular camera arranged on the measuring host machine, wherein the intersection point of the first rotating shaft and the second rotating shaft is the rotating center of the binocular camera, the extending direction of the first rotating shaft is a first direction, the extending direction of the second rotating shaft is a second direction,

The calibration method comprises the following steps:

the binocular camera emits a first light beam, the first light beam is received by a target and reflected back to the binocular camera, the first light beam reflected by the target is converged to a first imaging element of the binocular camera by a first lens of the binocular camera and first light spot data is obtained, the first light spot data includes a first component along the second direction and a second component along the first direction,

the binocular camera emits a second light beam, the second light beam is received by the target and reflected back to the binocular camera, the second light beam reflected by the target is converged to a second imaging element of the binocular camera through a second lens of the binocular camera and second light spot data is obtained, the second light spot data comprises a third component along the second direction and a fourth component along the first direction, and a connecting line of a light center of the first lens and a light center of the second lens is parallel to the second rotation axis;

moving the target to change a distance of the target from the binocular camera;

acquiring the first component, the third component and the distance between the target and the binocular camera in the moving process of the target;

Calibrating the distance between the first lens and the second lens based on the first component, the third component, the focal lengths of the first lens and the second lens, and preset device parameters of the first imaging element and the second imaging element,

the difference between the first component and the third component has a first functional relationship with the distance of the target to the binocular camera:

wherein D is _i In order to obtain the distance from the target to the binocular camera at the ith moment in the moving process of the target, f is the focal length of the first lens and the second lens, b is a second parameter, A is the distance between the first lens and the second lens, u is a preset device parameter of the first imaging element and the second imaging element, x _i To provide a difference between the first component and the third component at an i-th moment in the course of the movement of the object,

in addition, the second parameter satisfies the formula:

b＝b ₂ -b ₁

wherein b is the second parameter, b ₁ B is the offset of the optical axis of the first lens and the image center of the first imaging element in the second direction in the first coordinate system ₂ Is an offset of an optical axis of the second lens and an image center of the second imaging element in the second direction in a second coordinate system.

2. The method of calibrating according to claim 1, wherein,

the target is moved in a line where the laser beam is located to change the distance of the target from the binocular camera.

3. The method of calibrating according to claim 2, wherein,

comprises calibrating a first parameter configured to calculate a first rotation angle of the measurement host about the first rotation axis with the rotation center as a center point in cooperation with the first component and the third component when the laser tracker tracks the target,

the method for calibrating the first parameter comprises the following steps:

placing the target on a straight line where the laser beam is positioned;

acquiring the first component and the third component;

the first parameter is obtained based on the first component and the third component.

4. A calibration method according to claim 3, wherein,

the calculation formula of the first rotation angle is as follows:

wherein α is the first rotation angle, u is preset equipment parameters of the first imaging element and the second imaging element, L is the distance from the rotation center to the binocular camera, D is the distance from the target to the binocular camera, f is the focal lengths of the first lens and the second lens, K is the first parameter, x ₁ And x ₂ Representing the first component and the third component, respectively.

5. The method of calibrating according to claim 1, wherein,

the method for calibrating the focal length of the first lens and the second lens comprises the following steps:

moving the target within a preset plane having a first preset distance from the binocular camera and relative to the binocular camera in a manner different from the second direction;

enabling the target and the rotation center to form a preset position relation;

acquiring the second component, the fourth component and a preset position relation between the target and the rotation center in the process of moving the target relative to the binocular camera in the preset plane along a mode different from the second direction;

and calibrating focal lengths of the first lens and the second lens based on the preset position relation, a second preset distance from the rotation center to the binocular camera, the second component and the fourth component, and preset equipment parameters of the first imaging element and the second imaging element.

6. The method of calibrating according to claim 5, wherein,

The preset position relationship is that a second rotation angle between a connecting line of the target and the rotation center and a straight line of the laser beam is smaller than a preset angle in a process that the target moves relative to the binocular camera in the preset plane along the first direction perpendicular to and intersecting with the straight line of the laser beam.

7. The method of calibrating according to claim 6, wherein,

the second rotation angle has a second functional relationship:

wherein beta is _i In the process that the target moves relative to the binocular camera along the first direction perpendicular to and intersecting the straight line of the laser beam in the preset plane, the second rotation angle acquired at the ith moment is L, which is the distance from the rotation center to the binocular camera, D, which is the distance from the target to the binocular camera, f, which is the focal lengths of the first lens and the second lens, u, which is preset equipment parameters of the first imaging element and the second imaging element, y _i And obtaining the average value of the second component and the fourth component at the ith moment in the process that the target moves relative to the binocular camera along the first direction which is perpendicular to and intersected with the straight line where the laser beam is positioned in the preset plane.

8. The method of calibrating according to claim 1, wherein,

comprises calibrating a second parameter configured to calculate a distance of the target to the binocular camera in cooperation with the first component and the third component,

the method for calibrating the second parameter comprises the following steps:

the second parameter is calculated based on a distance of the first lens and the second lens, a focal length of the first lens and the second lens.

9. The method of calibrating according to claim 8, wherein,

comprises calibrating a third parameter configured as an offset of an image center of the first imaging element from an optical axis of the first lens in the second direction and a fourth parameter configured as an offset of an image center of the second imaging element from an optical axis of the second lens in the second direction,

the method for calibrating the third parameter and the fourth parameter comprises the following steps:

and acquiring the third parameter and the fourth parameter based on the second parameter.