WO2021120911A1

WO2021120911A1 - Three-dimensional coordinate calibration method for plate-like workpiece

Info

Publication number: WO2021120911A1
Application number: PCT/CN2020/126585
Authority: WO
Inventors: 李海秋; 周善荣; 袁春林; 黄睿; 贺建兰
Original assignee: 中兴通讯股份有限公司
Priority date: 2019-12-17
Filing date: 2020-11-04
Publication date: 2021-06-24
Also published as: CN112985257A

Abstract

A three-dimensional coordinate calibration method for a plate-like workpiece, comprising: moving a camera (4) having a predetermined focal length f from different starting positions, and taking a plurality of images of the plate-like workpiece by using the camera (4); determining three non-collinear reference positions with the same distance from the plate-like workpiece according to the definition of the plurality of images, taking a plane determined by the three reference positions as a reference plane (100), and determining a Z-axis calibration direction; moving the camera (4) in the reference plane (100) to capture a first predetermined feature (201) on the plate-like workpiece, obtaining a deflection angle of the first predetermined feature (201), and determining X-axis and Y-axis calibration directions according to the deflection angle; and determining the coordinate axis direction of a three-dimensional coordinate system where the plate-like workpiece is located.

Description

Three-dimensional coordinate calibration method of plate-shaped workpiece

Cross-references to related applications

This application is based on a Chinese patent application with application number 201911302623.3 and an application date of December 17, 2019, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby incorporated into this application by way of introduction.

Technical field

The embodiments of the present application relate to the field of detection technology, and in particular to a method for calibrating a three-dimensional coordinate of a plate-shaped workpiece.

Background technique

With the development of electronic product technology, the trend of miniaturization of components has become more and more obvious, and the density of products has also increased. Therefore, in the manufacturing industry of electronic products, surface mount technology (SMT) is used for PCBA ( Printed Circuit Board Assembly) manufacturing and assembly, using automated machine vision measurement technology for the visual inspection of PCBA products.

Summary of the invention

The embodiment of the present application provides a method for calibrating a three-dimensional coordinate of a plate-shaped workpiece, which includes the following steps: moving a camera with a predetermined focal length f from different starting positions and in a direction closer to/away from the plate-shaped workpiece. The camera is used to take multiple images of the plate-shaped workpiece; according to the definition of the multiple images, three non-collinear reference positions that are the same distance from the plate-shaped workpiece are determined, and the three reference positions are determined The plane is used as a reference plane, and the Z-axis calibration direction is determined according to the reference plane; the camera is moved in the reference plane to grab the first predetermined feature on the plate-shaped workpiece, and the first predetermined feature is analyzed. Image, acquiring the deflection angle of the first predetermined feature, and determining the X-axis calibration direction and the Y-axis calibration direction according to the deflection angle; according to the X-axis calibration direction, the Y-axis calibration direction, and the Z-axis calibration The direction determines the coordinate axis direction of the calibration three-dimensional coordinate system where the plate-shaped workpiece is located.

Description of the drawings

One or more embodiments are exemplified by the pictures in the corresponding drawings. These exemplified descriptions do not constitute a limitation on the embodiments. The elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the attached drawings do not constitute a scale limitation.

Fig. 1 is a flowchart of a method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to a first embodiment of the present application;

2 is a schematic diagram of a method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to the first embodiment of the present application;

3 is a flowchart of a method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to a second embodiment of the present application;

4 is a front view of the fixing structure after fixing the plate-shaped workpiece according to the second embodiment of the present application;

5 is a top view of the fixing structure after fixing the plate-shaped workpiece according to the second embodiment of the present application;

Fig. 6 is a schematic diagram of a method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to a second embodiment of the present application;

Fig. 7 is a flowchart of a method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to a third embodiment of the present application;

Fig. 8 is a flowchart of a method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to a fourth embodiment of the present application;

Fig. 9 is a flowchart of a method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to a fifth embodiment of the present application.

Detailed ways

In order to make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the various embodiments of the present application will be described in detail below with reference to the accompanying drawings. However, those of ordinary skill in the art can understand that in each embodiment of the present application, many technical details are proposed in order to enable readers to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solution claimed in this application can be realized. The following divisions of the various embodiments are for convenience of description, and should not constitute any limitation on the specific implementation manners of the present application, and the various embodiments may be combined with each other without contradiction.

The inventor found that there are at least the following problems in the prior art: machine vision measurement technology can realize high-precision defect detection. High-precision detection requires the measured object to be at a fixed magnification during imaging. In visual measurement, a fixed-focus lens is usually used to achieve a fixed magnification. At this time, the measured object is required to be positioned with a positioning fixture to ensure high-precision positioning. The working distance between camera lenses is constant. Therefore, how to provide economical and reliable three-dimensional coordinate calibration for high-precision machine vision measurement is an urgent technical problem to be solved.

Based on this, the purpose of the embodiments of the present application is to provide a three-dimensional coordinate calibration method for a plate-shaped workpiece, which provides economical and reliable three-dimensional coordinate calibration for high-precision machine vision measurement.

The first embodiment of the present application relates to a method for calibrating three-dimensional coordinates of plate-shaped workpieces, which can be applied to the three-dimensional coordinate calibration of plate-shaped workpieces such as PCBA. The core of the first embodiment of the present application is: Move a camera with a predetermined focal length f in the direction close to/away from the plate-shaped workpiece, and use the camera to take multiple images of the plate-shaped workpiece during each movement; determine the distance to the plate-shaped workpiece according to the sharpness of the multiple images The same three non-collinear reference positions, the plane determined by the three reference positions is used as the reference plane, and the Z-axis calibration direction is determined according to the reference plane; the camera is moved in the reference plane to grasp Take the first predetermined feature on the plate-shaped workpiece, analyze the image of the first predetermined feature, obtain the deflection angle of the first predetermined feature, and determine the X-axis calibration direction and the Y-axis calibration direction according to the deflection angle ; Determine the coordinate axis direction of the calibration three-dimensional coordinate system where the plate-shaped workpiece is located according to the X-axis calibration direction, the Y-axis calibration direction and the Z-axis calibration direction.

In the first embodiment of the present application, the plate-shaped workpiece is photographed by a camera with a predetermined focal length to correct the Z-axis direction, and the X-axis and Y-axis directions are corrected by using the deflection angle of the first predetermined feature.

1. As the camera and the plate-shaped workpiece are at different distances, the captured images have different definitions. In this way, at least three positions that are the same distance from the plate-shaped workpiece and are not collinear can be determined according to the sharpness of the image. The at least three non-collinear position points can determine a plane parallel to the plate-shaped workpiece, that is, parallel to the "XY plane" of the "three-dimensional coordinate system constructed with the plane of the plate-shaped workpiece as the XY plane" Reference plane, and then determine the Z-axis direction perpendicular to the reference plane;

2. Because the theoretical design angle of the first predetermined feature on the plate-shaped workpiece has a predetermined angle relationship with the "X-axis, Y-axis" of the "three-dimensional coordinate system constructed with the plane of the plate-shaped workpiece as the XY plane" In this way, after the deflection angle of the first predetermined feature on the plate-shaped workpiece is obtained, the torsion angle of the "X-axis, Y-axis" can be determined by referring to the relationship between the theoretical design angle of the first predetermined feature and the predetermined included angle. To determine the X-axis and Y-axis directions;

In this way, in the subsequent visual measurement, as long as the fixed focus lens is moved along the plane perpendicular to the Z-axis calibration direction (that is, the XY plane composed of the X-axis calibration direction and the Y-axis calibration direction), it can ensure that the fixed focus lens is in The working distance between the object and the measured object is constant during the movement. The entire calibration process only needs to be achieved with a monocular camera with a predetermined focal length, which can provide economical and reliable three-dimensional coordinate calibration for high-precision machine vision measurement. .

The implementation details of the three-dimensional coordinate calibration method of the plate-shaped workpiece of this embodiment will be described in detail below. Since this method is suitable for plate-shaped workpieces like PCBA, the PCBA assembled into the chassis is taken as an example in this embodiment. , Explain the three-dimensional coordinate calibration method of PCBA assembled in the chassis. It should be noted that the following content is only the implementation details provided for ease of understanding, and is not necessary for the implementation of this solution. Referring to FIG. 1, the method for calibrating a three-dimensional coordinate of a plate-shaped workpiece provided by the first embodiment of the present application includes the following steps.

S101. Move a camera with a predetermined focal length f from different starting positions in a direction close to/away from the plate-shaped workpiece, and use the camera to take multiple images of the plate-shaped workpiece during each movement.

Specifically, please refer to FIG. 2 together. In step S101, three starting positions A, B, and C that are far away from PCBA2 and are not collinear can be preselected. The camera 4 is moved in the direction close to PCBA2 (the arrow direction shown in FIG. 2) with the three starting positions A, B, and C as starting points, respectively. In the process of moving from the starting position A in the direction close to PCBA, in the process of moving from the starting position B in the direction close to PCBA2, and in the process of moving from the starting position C in the direction close to PCBA, use all The camera captures multiple images of a plate-shaped workpiece.

It should be noted that, in this embodiment, the use of the camera to capture multiple images of the plate-shaped workpiece can be “continuously captured images during the movement” or “every time a preset distance is moved, all images The camera takes an image of a plate-shaped workpiece". Understandably, in the solution of “using the camera to take an image of a plate-shaped workpiece every time a preset distance is moved”, the preset distance can be appropriately adjusted with reference to the preset focal length f of the camera, so as to ensure a certain calibration accuracy. , Appropriately reduce the number of images taken, reduce the amount of calculation for image definition analysis, and speed up the calibration.

In addition, it is understandable that the process of moving the camera 4 is not limited to moving from the starting point in a direction close to PCBA2. Three starting positions A, B, and C that are closer to PCBA2 and not collinear can also be selected in advance. , And then move the camera 4 in the direction away from the PCBA2 (the direction opposite to the arrow direction shown in FIG. 2) with the three starting positions A, B, and C as the starting points.

S102. Determine three non-collinear reference positions that are the same distance from the plate-shaped workpiece according to the definition of the multiple images, use the plane determined by the three reference positions as the reference plane, and determine Z according to the reference plane. Axis calibration direction.

Since the camera 4 and PCBA2 are at different distances, the captured images have different definitions. Therefore, each time the camera 4 moves closer to the PCBA2, the position where the camera 4 takes the clearest image must be the distance f from the PCBA2. s position. Therefore, in step S102, it is possible to first obtain multiple pictures taken by the camera 4 during each movement; then analyze the multiple pictures taken during each movement, and obtain the clearness of the multiple pictures taken during each movement. The picture with the highest degree of resolution; the positions A', B', C'where the camera 4 is located when the picture with the highest definition is taken are determined as the reference positions. Then, the plane determined by the three reference positions A', B', and C'can be used as the reference plane 100, and the direction perpendicular to the reference plane 100 can be determined as the Z-axis calibration direction (shown by the dotted line in FIG. 2) .

S103. Move the camera in the reference plane to grab the first predetermined feature on the plate-shaped workpiece, analyze the image of the first predetermined feature, and obtain the deflection angle of the first predetermined feature, The X-axis calibration direction and the Y-axis calibration direction are determined according to the deflection angle.

Specifically, the camera 4 can be moved back and forth along the rough XY plane in the reference plane 100, so that the angle of view of the camera 4 sweeps through various areas of the PCBA2, and multiple images of the PCBA2 are taken during the movement of the camera 4, And when the image of the first predetermined feature 201 on the PCBA 2 is captured, the image of the first predetermined feature 201 is analyzed to obtain the deflection angle of the first predetermined feature 201. Since the theoretical design angle of the first predetermined feature 201 on the PCBA2 is in a predetermined angle relationship with the "X-axis, Y-axis" of the "3D coordinate system constructed with the PCBA as the XY plane", in this way, when After obtaining the deflection angle of the first predetermined feature 201 on the PCBA2, the torsion angle of the "X axis, Y axis" can be determined by referring to the theoretical design angle of the first predetermined feature 201 and the predetermined included angle, thereby determining the X axis , Y axis direction.

For example, when the first predetermined feature 201 is a rectangle and its theoretical design angle is "the long side of the rectangle is parallel to the X axis (that is, perpendicular to the Y axis)",

a. If it is detected that the deflection angle of the long side of the first predetermined feature 201 in the rough XY plane is 0 degrees, because "the long side of the rectangle is parallel to the X axis (that is, perpendicular to the Y axis)", then the current The X-axis direction in the rough XY plane is parallel to the X-axis calibration direction, you can determine that the X-axis calibration direction is parallel to the X-axis direction in the currently rough XY plane, and the Y-axis calibration direction is in the current rough XY plane. X axis direction is vertical;

b. If it is detected that the deflection angle of the long side of the first predetermined feature 201 in the rough XY plane is 5 degrees in the clockwise direction, because "the long side of the rectangle is parallel to the X axis (that is, perpendicular to the Y axis) ", then it means that the X-axis direction in the current rough XY plane is deviated by 5 degrees in the counterclockwise direction compared to the X-axis calibration direction. In this way, the X-axis calibration direction can be determined to be the X in the current rough XY plane. The axis direction is the direction deviated by 5 degrees in the clockwise direction, and the Y-axis calibration direction is the direction where the X axis direction in the current rough XY plane is deviated by 95 degrees in the clockwise direction.

S104. Determine the coordinate axis direction of the calibration three-dimensional coordinate system where the plate-shaped workpiece is located according to the X-axis calibration direction, the Y-axis calibration direction, and the Z-axis calibration direction.

Specifically, after acquiring the X-axis calibration direction, the Y-axis calibration direction, and the Z-axis calibration direction, it can be learned that the PCBA is in the current fixed position, and "the three-dimensional coordinate system established with PCBA2 as the XY plane" is compared with The deflection angle of the "coarsely defined three-dimensional coordinate system established by the rough XY plane", so as to achieve the calibration of each axis direction of the three-dimensional coordinates of the PCBA, which is convenient for subsequent use of machine vision to measure, refer to the XY plane of the calibration three-dimensional coordinate system to move the camera lens , To ensure that the working distance between the PCBA under test and the camera lens is constant.

The second embodiment of the present application provides a three-dimensional coordinate calibration method of a plate-shaped workpiece, which is substantially the same as the three-dimensional coordinate calibration method of a plate-shaped workpiece provided in the first embodiment. The difference is that the method provided in the second embodiment of the present application The three-dimensional coordinate calibration method of the plate-shaped workpiece additionally includes the preparation steps of fixing the plate-shaped workpiece and selecting the starting position. Specifically, referring to FIG. 3, the method for calibrating a three-dimensional coordinate of a plate-shaped workpiece provided by the second embodiment of the present application includes the following steps:

S201. Fix the plate-shaped workpiece on the fixed fixture, and determine the initial three-dimensional coordinate system according to the fixed fixture;

S202. Determine three non-collinear starting positions in the initial initial three-dimensional coordinate system, wherein, in the Z-axis direction of the initial three-dimensional coordinate system, each of the starting positions and the plate-shaped workpiece The distance between is f+△E/f-△E, where △E is the assembly tolerance of the plate-shaped workpiece in the Z-axis direction;

S203. Move a camera with a predetermined focal length f from different starting positions in a direction close to/away from the plate-shaped workpiece, and use the camera to take multiple images of the plate-shaped workpiece during each movement;

S204. Determine three non-collinear reference positions that are the same distance from the plate-shaped workpiece according to the definition of the multiple images, use the plane determined by the three reference positions as the reference plane, and determine Z according to the reference plane. Axis calibration direction;

S205. Move the camera in the reference plane to grab the first predetermined feature on the plate-shaped workpiece, analyze the image of the first predetermined feature, and obtain the deflection angle of the first predetermined feature, Determine the X-axis calibration direction and the Y-axis calibration direction according to the deflection angle;

S206. Determine the coordinate axis direction of the calibration three-dimensional coordinate system where the plate-shaped workpiece is located according to the X-axis calibration direction, the Y-axis calibration direction, and the Z-axis calibration direction.

Regarding step S201, referring to FIG. 4 and FIG. 5, specifically, the chassis 1 equipped with the PCBA 2 is fixed on the fixing fixture 3 first. Since the PCBA2 to be calibrated is assembled in the chassis 1, the PCBA2 is indirectly fixed on the fixing fixture 3, as shown in Figs. 4 and 5.

In an ideal state, a well-designed fixing fixture 3 can accurately hold the PCBA2 in the XY plane perpendicular to the drawing surface shown in Figure 4 (also perpendicular to the drawing surface shown in Figure 5). However, in actual situations, After the PCBA2 is assembled in the chassis 1 to complete other tests, the PCBA2 cannot be disassembled and then inspected during the visual inspection. At this time, the chassis 1 needs to be accurately positioned. However, when the chassis 1 is large in size and weight, it will be more difficult to implement the positioning of the chassis 1 itself, and the implementation cost will be higher. In addition, when PCBA2 is assembled in chassis 1, the internal assembly tolerances of chassis 1 make it impossible to accurately locate PCBA2 even if chassis 1 can be accurately positioned. Therefore, a method is needed to achieve precise positioning of PCBA2 inside chassis 1 alone. . After fixing the PCBA2 on the fixing fixture 3, the initial three-dimensional coordinate system XYZ is determined according to the fixing fixture 3, as shown in FIG. 6. The so-called "initial three-dimensional coordinate system" refers to an ideal three-dimensional coordinate system determined by taking the plane of PCBA2 as the XY plane in an ideal state where there is no assembly tolerance between PCBA2 and chassis 1. But in fact, the three-dimensional coordinate system determined by the plane where the assembled PCBA2 is located, its X-axis, Y-axis, and Z-axis directions will all be affected by the assembly tolerance between PCBA2 and the chassis 1, which is different from the aforementioned initial three-dimensional coordinate system. The X-axis, Y-axis, and Z-axis directions of the system (that is, the ideal three-dimensional coordinate system) are different.

Regarding step S202, three non-collinear starting positions A, B, and C are determined in the initial three-dimensional coordinate system, as shown in FIG. 6. In this embodiment, in the Z-axis direction of the initial three-dimensional coordinate system, the distance between each of the initial positions and the plate-shaped workpiece is f+△E/f-△E, where △E is The assembly tolerance of the plate-shaped workpiece in the Z-axis direction. This setting takes into account the assembly tolerance △E of the plate-shaped workpiece,

a. If the position where "the distance to the plate-shaped workpiece is f+△E" is taken as the starting point of the movement, then the "distance from the plate-shaped workpiece is f-△E" in the moving direction. As the end of the movement;

b. If the position where "the distance from the plate-shaped workpiece is f-△E" is the starting point of the movement, then the "distance from the plate-shaped workpiece is f+△E" in the moving direction. As the end of the movement,

Ensure that the camera can pass through the optimal imaging position when moving in the direction close to/away from the plate-shaped workpiece, so that a clear image at the optimal imaging position can be captured during each movement, which is convenient for subsequent use of clear images to determine and The distance of the plate-shaped workpiece is the reference position of f.

It needs to be supplemented that, as shown in Figs. 4 and 5, a mechanical arm 5 is also provided on one side of the fixing jig 3. A camera 4 is fixed at the end of the mechanical arm 5, and the camera 4 is a monocular camera with a predetermined focal length f. Driven by the robotic arm 5, the camera 4 can move freely in the X-axis direction, the Y-axis direction, and the Z-axis direction of the initial three-dimensional coordinate system.

Regarding step S203, specifically, the three starting positions A, B, and C are used as starting points, and the Z-axis direction of the initial three-dimensional coordinate system is moved toward/away from the plate-shaped workpiece with a predetermined focal length f. camera. Since the Z-axis direction of the initial three-dimensional coordinate system is the closest to the direction "perpendicular to" the plate-shaped workpiece, moving the camera along the direction perpendicular or nearly perpendicular to the plate-shaped workpiece can quickly traverse to the reference with a distance of f from the plate-shaped workpiece Obtain a clear image based on the location and shorten the calibration time.

Regarding step 204, since the camera 4 and PCBA2 are at different distances from each other, the captured images have different definitions. Therefore, each time the camera 4 moves closer to the PCBA2, the position where the camera 4 takes the clearest image must be the same The position of PCBA2 away from f. Therefore, in step S102, the multiple pictures taken by the camera 4 during each movement can be obtained first; then the multiple pictures taken during each movement are analyzed, and the sharpness of the multiple pictures taken during each movement can be obtained. The picture with the highest degree of resolution; the positions A', B', C'where the camera 4 is located when the picture with the highest definition is taken are determined as the reference positions. Then, the plane determined by the three reference positions A', B', C'can be used as the reference plane 100, and the direction perpendicular to the reference plane 100 can be determined as the Z-axis calibration direction (shown by the dotted line in FIG. 6) .

Step S204 to step S206 are substantially the same as step S102 to step S104 of the first embodiment, and will not be repeated here.

In the method for calibrating the three-dimensional coordinates of a plate-shaped workpiece provided by the second embodiment of the present application, after obtaining the X-axis calibration direction, the Y-axis calibration direction, and the Z-axis calibration direction, it can be learned that the PCBA is at the current fixed position, "with PCBA2 in The deflection angle of the "three-dimensional coordinate system established by the XY plane" compared to the "coarse three-dimensional coordinate system established by the rough XY plane", so as to achieve the three-dimensional coordinate calibration of PCBA.

The third embodiment of the present application provides a three-dimensional coordinate calibration method of a plate-shaped workpiece, which is substantially the same as the three-dimensional coordinate calibration method of a plate-shaped workpiece provided in the second embodiment, except that the third embodiment of the present application provides The method for calibrating the three-dimensional coordinates of a plate-shaped workpiece further specifically refines step S205 of the second embodiment. Specifically, referring to FIG. 7, the method for calibrating a three-dimensional coordinate of a plate-shaped workpiece provided by the third embodiment of the present application includes the following steps:

S301. Fix the plate-shaped workpiece on the fixed fixture, and determine the initial three-dimensional coordinate system according to the fixed fixture;

S302. Determine three non-collinear starting positions in the initial initial three-dimensional coordinate system, wherein, in the Z-axis direction of the initial three-dimensional coordinate system, each of the starting positions and the plate-shaped workpiece The distance between is f+△E/f-△E, where △E is the assembly tolerance of the plate-shaped workpiece in the Z-axis direction;

S303. Move a camera with a predetermined focal length f from different starting positions in a direction close to/away from the plate-shaped workpiece, and use the camera to take multiple images of the plate-shaped workpiece during each movement;

S304. Determine three non-collinear reference positions that are the same distance from the plate-shaped workpiece according to the definition of the multiple images, use the plane determined by the three reference positions as the reference plane, and determine Z according to the reference plane. Axis calibration direction;

S305. Use a direction located in the reference plane and parallel to the X axis of the initial three-dimensional coordinate system as the first direction, and use a direction located in the reference plane and parallel to the Y axis of the initial three-dimensional coordinate system as the first direction. The second direction; within the reference plane, move the camera along the first direction and the second direction, and take images of the plate-shaped workpiece during the movement until the camera captures the plate-shaped The first predetermined feature on the workpiece;

S306. Acquire the theoretical design angle of the first predetermined feature on the plate-shaped workpiece, wherein the X-axis direction and Y-axis direction of the three-dimensional coordinate system where the plate-shaped workpiece is actually located have a predetermined relationship with the theoretical design angle Obtain the angular difference between the theoretical design angle and the deflection angle; determine the X-axis calibration direction and the Y-axis calibration direction according to the angular difference and the predetermined relationship;

S307. Determine the coordinate axis direction of the calibration three-dimensional coordinate system where the plate-shaped workpiece is located according to the X-axis calibration direction, the Y-axis calibration direction, and the Z-axis calibration direction.

Steps S301 to S304 are substantially the same as steps S201 to S204 of the second embodiment, and step S307 is substantially the same as step S206 of the second embodiment, and will not be repeated here.

The third embodiment of the present application provides a method for calibrating the three-dimensional coordinates of a plate-shaped workpiece, which moves the camera along the X-axis and Y-axis directions of the initial three-dimensional coordinate system. Based on the advantages of the second embodiment, it also has the advantages of facilitating the camera The advantage of scanning the plate-shaped workpiece step by step and grabbing the first predetermined feature as soon as possible.

The fourth embodiment of the present application provides a three-dimensional coordinate calibration method of a plate-shaped workpiece, which is substantially the same as the three-dimensional coordinate calibration method of a plate-shaped workpiece provided in the third embodiment, except that the method provided by the fourth embodiment of the present application The three-dimensional coordinate calibration method of the plate-shaped workpiece additionally determines the origin of the calibration three-dimensional coordinate system. Specifically, referring to FIG. 8, the method for calibrating a three-dimensional coordinate of a plate-shaped workpiece provided by the fourth embodiment of the present application includes steps.

S401. Fix the plate-shaped workpiece on the fixed fixture, and determine the initial three-dimensional coordinate system according to the fixed fixture;

S402. Determine three non-collinear starting positions in the initial initial three-dimensional coordinate system, wherein, in the Z-axis direction of the initial three-dimensional coordinate system, each of the starting positions and the plate-shaped workpiece The distance between is f+△E/f-△E, where △E is the assembly tolerance of the plate-shaped workpiece in the Z-axis direction;

S403. Move a camera with a predetermined focal length f from different starting positions in a direction close to/away from the plate-shaped workpiece, and use the camera to take multiple images of the plate-shaped workpiece during each movement;

S404. Determine three non-collinear reference positions that are the same distance from the plate-shaped workpiece according to the definition of the multiple images, use the plane determined by the three reference positions as the reference plane, and determine Z according to the reference plane. Axis calibration direction;

S405. Use a direction located in the reference plane and parallel to the X axis of the initial three-dimensional coordinate system as the first direction, and use a direction located in the reference plane and parallel to the Y axis of the initial three-dimensional coordinate system as the first direction. The second direction; within the reference plane, move the camera along the first direction and the second direction, and take images of the plate-shaped workpiece during the movement until the camera captures the plate-shaped The first predetermined feature on the workpiece;

S406. Acquire the theoretical design angle of the first predetermined feature on the plate-shaped workpiece, wherein the X-axis direction and Y-axis direction of the three-dimensional coordinate system where the plate-shaped workpiece is actually located have a predetermined relationship with the theoretical design angle Obtain the angular difference between the theoretical design angle and the deflection angle; determine the X-axis calibration direction and the Y-axis calibration direction according to the angular difference and the predetermined relationship;

S407. Determine the coordinate axis direction of the calibration three-dimensional coordinate system where the plate-shaped workpiece is located according to the X-axis calibration direction, the Y-axis calibration direction, and the Z-axis calibration direction;

S408. Determine the calibration three-dimensional coordinate system according to the theoretical design position of the first predetermined feature on the plate-shaped workpiece, the predetermined focal length f, and the position at which the camera captures the first predetermined feature The origin position.

Steps S401 to S407 are substantially the same as steps S301 to S307 of the third embodiment, and will not be repeated here.

Regarding step S408, since the theoretical design position of the first predetermined feature on the plate-shaped workpiece has a predetermined positional relationship with the origin of the "three-dimensional coordinate system constructed with the plane on which the plate-shaped workpiece is located as the XY plane", in this way, according to The theoretical design position of the first predetermined feature and the predetermined focal length f can determine the positional relationship between the origin and "the position at which the first predetermined feature is captured", so that the positional relationship between the "first predetermined feature is captured" "The position of the object in time" deduces the position of the origin.

The method for calibrating the three-dimensional coordinates of a plate-shaped workpiece provided by the fourth embodiment of the present application is based on the theoretical design position of the first predetermined feature on the plate-shaped workpiece, the predetermined focal length f, and the location when the camera grabs the first predetermined feature. The position of determines the origin position of the calibration three-dimensional coordinate system, which can additionally determine the origin position of the calibration three-dimensional coordinate system based on the advantages of the third embodiment.

The fifth embodiment of the present application provides a method for calibrating a three-dimensional coordinate of a plate-shaped workpiece, which is substantially the same as the method for calibrating a three-dimensional coordinate of a plate-shaped workpiece provided in the fourth embodiment. The difference is that the fifth embodiment of the present application provides The three-dimensional coordinate calibration method of the plate-shaped workpiece additionally provides a verification method for calibrating the three-dimensional coordinate system. Specifically, referring to FIG. 9, the method for calibrating a three-dimensional coordinate of a plate-shaped workpiece provided by the fifth embodiment of the present application includes steps.

S501. Fix the plate-shaped workpiece on the fixed fixture, and determine the initial three-dimensional coordinate system according to the fixed fixture;

S502. Determine three non-collinear starting positions in the initial initial three-dimensional coordinate system, wherein, in the Z-axis direction of the initial three-dimensional coordinate system, each of the starting positions and the plate-shaped workpiece The distance between is f+△E/f-△E, where △E is the assembly tolerance of the plate-shaped workpiece in the Z-axis direction;

S503. Move a camera with a predetermined focal length f from different starting positions in a direction close to/away from the plate-shaped workpiece, and use the camera to take multiple images of the plate-shaped workpiece during each movement.

S504. Determine three non-collinear reference positions that are the same distance from the plate-shaped workpiece according to the definition of the multiple images, use the plane determined by the three reference positions as the reference plane, and determine Z according to the reference plane. Axis calibration direction.

S505. Use a direction located in the reference plane and parallel to the X axis of the initial three-dimensional coordinate system as the first direction, and use a direction located in the reference plane and parallel to the Y axis of the initial three-dimensional coordinate system as the first direction. The second direction; within the reference plane, move the camera along the first direction and the second direction, and take images of the plate-shaped workpiece during the movement until the camera captures the plate-shaped The first predetermined feature on the workpiece.

S506. Acquire the theoretical design angle of the first predetermined feature on the plate-shaped workpiece, wherein the X-axis direction and Y-axis direction of the three-dimensional coordinate system where the plate-shaped workpiece is actually located have a predetermined relationship with the theoretical design angle Obtain the angular difference between the theoretical design angle and the deflection angle; determine the X-axis calibration direction and the Y-axis calibration direction according to the angular difference and the predetermined relationship.

S507. Determine the coordinate axis direction of the calibration three-dimensional coordinate system where the plate-shaped workpiece is located according to the X-axis calibration direction, the Y-axis calibration direction, and the Z-axis calibration direction.

S508. Determine the calibration three-dimensional coordinate system according to the theoretical design position of the first predetermined feature on the plate-shaped workpiece, the predetermined focal length f, and the position at which the camera captures the first predetermined feature The origin position.

S509. Calculate the projection position of the second predetermined feature on the reference plane according to the theoretical design position of the second predetermined feature on the plate-shaped workpiece, and use the camera to photograph the plate-shaped workpiece at the projection position image;

If the image of the plate-shaped workpiece taken at the projection position includes the second predetermined feature, the calibrated three-dimensional coordinate system is used as the effective three-dimensional coordinate system of the plate-shaped workpiece;

If the image of the plate-shaped workpiece taken at the projection position does not include the second predetermined feature, the three-dimensional coordinates of the plate-shaped workpiece are recalibrated.

Steps S501 to S508 are substantially the same as steps S501 to S508 of the fourth embodiment, and will not be repeated here.

Specifically, with regard to step S509, after determining the axis directions and origin positions of the calibration three-dimensional coordinate system, according to the theoretical design position of the second predetermined feature on the plate-shaped workpiece, it is determined that "the second predetermined feature can be photographed on the plate-shaped workpiece. Then move the camera to the projection position to shoot the plate-shaped workpiece. If the captured image of the plate-shaped workpiece contains the second predetermined feature, it will be explained The calibrated three-dimensional coordinate system obtained by calibration is sufficiently accurate and can be used as an effective three-dimensional coordinate system for subsequent machine vision measurement; if the captured image of the plate-shaped workpiece does not contain the second predetermined feature, the calibrated three-dimensional coordinate system obtained by calibration If there is an error, it can be re-calibrated according to the aforementioned steps S501 to S508 to obtain a valid three-dimensional coordinate system.

Based on the advantages of the fourth embodiment, the method for calibrating the three-dimensional coordinates of a plate-shaped workpiece provided by the fifth embodiment of the present application can additionally verify the accuracy of the calibration of the three-dimensional coordinate system. The reliability of the three-dimensional coordinate calibration of the shaped workpiece.

Those of ordinary skill in the art can understand that the above implementations are specific examples for realizing the present application. The steps of the various methods above are divided for clarity of description, and can be combined into one step or some steps can be split during implementation. , Decomposed into multiple steps, and in actual application, various changes can be made in form and details without departing from the spirit and scope of this application. As long as the same logical relationship is included, they are protected by this patent. Within range.

Claims

A method for calibrating three-dimensional coordinates of a plate-shaped workpiece, which includes:

Move a camera with a predetermined focal length f from different starting positions in a direction close to/away from the plate-shaped workpiece, and use the camera to take multiple images of the plate-shaped workpiece during each movement;

Determine three non-collinear reference positions that are the same distance from the plate-shaped workpiece according to the definition of the multiple images, use the plane determined by the three reference positions as the reference plane, and determine the Z-axis calibration according to the reference plane direction;

Move the camera in the reference plane to grab the first predetermined feature on the plate-shaped workpiece, analyze the image of the first predetermined feature, and obtain the deflection angle of the first predetermined feature, according to the The deflection angle determines the X-axis calibration direction and Y-axis calibration direction;

Determine the coordinate axis direction of the calibration three-dimensional coordinate system where the plate-shaped workpiece is located according to the X-axis calibration direction, the Y-axis calibration direction and the Z-axis calibration direction.
The method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to claim 1, wherein the photographing multiple images of the plate-shaped workpiece with the camera during each movement is:

Every time a preset distance is moved, an image of a plate-shaped workpiece is taken by the camera.
The method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to claim 1, wherein the determining three non-collinear reference positions at the same distance from the plate-shaped workpiece according to the sharpness of the multiple images includes:

Acquiring multiple pictures taken by the camera during each movement;

Analyze the multiple pictures taken during each movement, and obtain the picture with the highest definition among the multiple pictures taken during each movement;

The position where the camera is located when the picture with the highest definition is taken is determined as the reference position.
The method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to claim 3, wherein the step of moving the camera with a predetermined focal length f from different starting positions in a direction closer to/away from the plate-shaped workpiece includes:

Fix the plate-shaped workpiece on the fixed fixture, and determine the initial three-dimensional coordinate system according to the fixed fixture;

Determine three non-collinear starting positions in the initial initial three-dimensional coordinate system, wherein, in the Z-axis direction of the initial three-dimensional coordinate system, between each of the starting positions and the plate-shaped workpiece The distance of is f+△E/f-△E, where △E is the assembly tolerance of the plate-shaped workpiece in the Z-axis direction.
The method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to claim 4, wherein the moving the camera with a predetermined focal length f from different starting positions in a direction closer to/away from the plate-shaped workpiece is:

Moving the camera with a predetermined focal length f along the Z-axis direction of the initial three-dimensional coordinate system in a direction approaching/away from the plate-shaped workpiece with the three starting positions as starting points, respectively.
The method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to claim 4, wherein the moving the camera in the reference plane to grab the first predetermined feature on the plate-shaped workpiece is:

The direction located in the reference plane and parallel to the X axis of the initial three-dimensional coordinate system is taken as the first direction, and the direction located in the reference plane and parallel to the Y axis of the initial three-dimensional coordinate system is taken as the second direction. direction;

In the reference plane, move the camera along the first direction and the second direction respectively, and take an image of the plate-shaped workpiece during the movement, until the camera grabs the first plate-shaped workpiece. A predetermined feature.
The method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to claim 4, wherein the determining the X-axis calibration direction and the Y-axis calibration direction according to the deflection angle comprises:

Acquiring the theoretical design angle of the first predetermined feature on the plate-shaped workpiece, wherein the X-axis direction and the Y-axis direction of the three-dimensional coordinate system where the plate-shaped workpiece is actually located have a predetermined relationship with the theoretical design angle;

Acquiring the angular difference between the theoretical design angle and the deflection angle;

According to the angle difference and the predetermined relationship, the X-axis calibration direction and the Y-axis calibration direction are determined.
The method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to claim 7, wherein the method for determining where the plate-shaped workpiece is located is determined according to the X-axis calibration direction, the Y-axis calibration direction, and the Z-axis calibration direction. After calibrating the coordinate axis direction of the three-dimensional coordinate system, it also includes:

Determine the origin of the calibration three-dimensional coordinate system according to the theoretical design position of the first predetermined feature on the plate-shaped workpiece, the predetermined focal length f, and the position at which the camera captures the first predetermined feature position.
The method for calibrating a three-dimensional coordinate of a plate-shaped workpiece according to claim 8, wherein the theoretically designed position on the plate-shaped workpiece according to the first predetermined feature, the predetermined focal length f, and the camera grabbing After the position of the first predetermined characteristic object is determined after the origin position of the calibrated three-dimensional coordinate system is determined, the method further includes:

Calculating the projection position of the second predetermined feature on the reference plane according to the theoretical design position of the second predetermined feature on the plate-shaped workpiece;

Using the camera to take an image of the plate-shaped workpiece at the projection position;

If the image of the plate-shaped workpiece taken at the projection position includes the second predetermined feature, the calibrated three-dimensional coordinate system is used as the effective three-dimensional coordinate system of the plate-shaped workpiece.
9. The method for calibrating the three-dimensional coordinates of the plate-shaped workpiece according to claim 9, wherein after the use of the camera to take an image of the plate-shaped workpiece at the projection position, the method further comprises:

If the image of the plate-shaped workpiece taken at the projection position does not include the second predetermined feature, the three-dimensional coordinates of the plate-shaped workpiece are recalibrated.