Calibration device and calibration method suitable for industrial camera

Abstract

The invention discloses a calibration device and a calibration method suitable for an industrial camera, and the calibration device comprises a device body which is formed by at least extending along a preset direction; the calibration unit is arranged on at least one side of the device body at least along the preset direction; wherein the calibration unit protrudes out of the device body. The calibration device and the calibration method have the beneficial effects that secondary calibration can be efficiently carried out on the industrial camera installed on the production line.

Description

Technical Field

[0001] This application relates to the field of industrial camera calibration technology, and more specifically, to a calibration device and calibration method suitable for industrial cameras. Background Technology

[0002] Industrial cameras, especially 3D industrial cameras, are used in various industries due to their high acquisition speed, accuracy, and high repeatability.

[0003] The pixel coordinate system of the image sensor inside the 3D industrial camera differs from the planar coordinate system of the 3D industrial camera's field of view, resulting in inconsistent pixel resolution in each area of ​​the 3D industrial camera's field of view; furthermore, the distortion caused by the 3D industrial camera's lens is also inconsistent.

[0004] Therefore, the correspondence between the pixel coordinate system of a 3D industrial camera and the planar coordinate system of the camera's field of view is quite complex. In order to obtain high detection accuracy, it is particularly important to control the object imaging within the optimal accuracy region of the camera coordinate system.

[0005] Different areas of the image sensor have different light-sensitive areas at different heights, meaning that the pixel resolution of a 3D industrial camera varies at each depth of field.

[0006] In addition, when a 3D industrial camera is installed on a production line for measurement, it is necessary to establish a relationship between the production line coordinate system and the camera coordinate system.

[0007] To ensure the accuracy of 3D industrial camera measurements, especially when the accuracy of the measured object is close to the camera resolution, secondary calibration of the field of view on the production line is particularly important (because the required operating range of the production line cannot be known when the 3D industrial camera is manufactured). After the 3D industrial camera is deployed on the production line, the field of view used needs to be calibrated.

[0008] Currently, there is no suitable calibration device or calibration method for achieving the above calibration. Summary of the Invention

[0009] The summary section of this application is intended to provide a brief overview of the concepts, which will be described in detail in the detailed description section below. This summary section is not intended to identify key or essential features of the claimed technical solutions, nor is it intended to limit the scope of the claimed technical solutions.

[0010] Some embodiments of this application propose calibration devices and calibration methods suitable for industrial cameras to solve the technical problems mentioned in the background section above.

[0011] As a first aspect of this application, some embodiments of this application provide a calibration device, including: a device body extending at least along a preset direction; and a calibration unit disposed at least along the preset direction on at least one side of the device body; wherein the calibration unit protrudes from the device body.

[0012] Optionally, in some embodiments of this application, the device body has a body base surface, which is configured as a plane parallel to the preset direction.

[0013] Optionally, in some embodiments of this application, the device body is constructed as a rectangular body; the calibration unit is disposed on the largest rectangular surface of the rectangular body.

[0014] Optionally, in some embodiments of this application, the calibration unit has a top calibration surface; the top calibration surface is constructed as a plane parallel to the preset direction; the top calibration surface is disposed on the top of the calibration unit.

[0015] Optionally, in some embodiments of this application, the calibration unit has a side calibration surface; the side calibration surface is constructed as a plane that intersects the preset direction at an angle; the outline of the side calibration surface is an isosceles trapezoid.

[0016] As a second aspect of this application, some embodiments of this application provide a calibration method, including: translating the calibration device along a preset direction; scanning the device body and calibration unit in the calibration device with an industrial camera to be calibrated; generating a camera model based on the scanning data of the industrial camera; and comparing the camera model with the real model of the calibration device to complete the calibration of the industrial camera.

[0017] Optionally, in some embodiments of this application, the laser beam from the industrial camera is made perpendicular to the preset direction.

[0018] Optionally, in some embodiments of this application, the axis of the lens of the industrial camera is tilted to intersect the preset direction.

[0019] Optionally, in some embodiments of this application, the step of comparing the camera model and the real model of the calibration device to complete the calibration of the industrial camera includes: obtaining the parameters of the industrial camera based on the comparison between the camera model and the real model; obtaining the transformation matrix between the coordinate system of the industrial camera and the coordinate system of the calibration device based on the comparison between the camera model and the real model; and saving the data of the transformation matrix.

[0020] The beneficial effects of this application are: it provides a calibration device and calibration method that can efficiently perform secondary calibration of industrial cameras installed on production lines. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application.

[0022] Furthermore, throughout the accompanying drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and the elements are not necessarily drawn to scale.

[0023] In the attached diagram: Figure 1 This is a three-dimensional structural schematic diagram of a calibration device according to an embodiment of this application; Figure 2 yes Figure 1 The diagram shows a top view of the calibration device. Figure 3 yes Figure 1 A side view of the calibration device is shown. Figure 4 yes Figure 1 A three-dimensional schematic diagram of the calibration device during calibration. Figure 5 yes Figure 1 A schematic diagram of the calibration device during calibration. Figure 6 This is a schematic diagram illustrating the main steps of a calibration method according to an embodiment of this application; Figure 7 This is a schematic diagram of some steps in a calibration method according to an embodiment of this application.

[0024] Meaning of the reference numerals in the attached figures: 100. Calibration device; 110. Device body; 111. Main body base surface; 120. Calibration Unit; 121. Top marker positioning; 122. Side marker positioning; 123. Corner line; 200. Industrial cameras; 210. Laser beam; 220. Lens axis; D. Preset direction. Detailed Implementation

[0025] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0026] It should also be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other.

[0027] It should be noted that the concepts of "first" and "second" mentioned in this disclosure are used only to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or their interdependencies.

[0028] It should be noted that the terms "a" and "a plurality of" used in this disclosure are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0029] The names of messages or information exchanged between multiple devices in the embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of such messages or information.

[0030] This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] Reference Figures 1 to 3 As shown, the calibration device 100 for an industrial camera 200 of this application includes: a device body 110 and a calibration unit 120.

[0032] The device body 110 extends at least along a preset direction D; the calibration unit 120 is arranged at least along the preset direction D on at least one side of the device body 110; and the calibration unit 120 protrudes from the device body 110.

[0033] In this way, the height difference between the calibration unit 120 and the device body 110, as well as the distance between the calibration unit 120, can be in different pixel areas when the calibration device 100 passes the industrial camera 200. Thus, based on the conversion and comparison between the size measured by the industrial camera 200 and the actual size of the calibration device 100, a secondary calibration of the current field of view of the industrial camera 200 on the production line can be completed.

[0034] Reference Figures 1 to 3As shown, in some embodiments of this application, the device body 110 has a body base surface 111, which is constructed as a plane parallel to a preset direction D. This facilitates the provision of a solid plane for the coordinate plane during secondary calibration.

[0035] Reference Figures 1 to 3 As shown, in some embodiments of this application, the device body 110 is constructed as a rectangular body; the calibration unit 120 is disposed on the largest rectangular surface of the rectangular body. This facilitates ensuring the volume of the calibration unit 120, and also facilitates the industrial camera 200 to photograph the device body 110 and the calibration unit 120.

[0036] Reference Figures 1 to 3 As shown, in some embodiments of this application, the calibration unit 120 has a top calibration surface 121; the top calibration surface 121 is constructed as a plane parallel to a preset direction D; the top calibration surface 121 is disposed on the top of the calibration unit 120. The advantage of this is that the height direction and flatness can be effectively calibrated by using two parallel but different planes, the body base surface 111 and the top calibration surface 121.

[0037] Reference Figures 1 to 3 As shown, in some embodiments of this application, the calibration unit 120 has a side calibration surface 122; the side calibration surface 122 is configured as a plane that intersects with a preset direction D at an angle; the outline of the side calibration surface 122 is an isosceles trapezoid.

[0038] That is, the top calibration surface 121 of the calibration unit 120 is a smaller rectangular plane. The bottom calibration surface (not shown in the figure) of the calibration unit 120 is a larger rectangular plane. Their rectangular sides are parallel, their rectangular centers (the intersection of their diagonals) are aligned, and then their corresponding vertices are connected to form inclined ridges 123, which are the sides of the isosceles trapezoids of the side calibration surface 122; as an optional option, both the larger and smaller rectangles are squares.

[0039] The advantages of this approach are that the design of the calibration unit 120, which is smaller at the top and larger at the bottom, facilitates unobstructed shooting by the industrial camera 200; the symmetrical design of the calibration unit 120 allows for simultaneous calibration of two opposing industrial cameras 200 without considering their opposite shooting directions; the ridge line 123, which tends to intersect with the three dimensions, extends in different directions to simultaneously calibrate the linearity (the linearity of a straight line after imaging) in different directions; and the side calibration surface 122 can calibrate the contour.

[0040] As can be seen from the above description, the ingenious design of the calibration unit 120 in this application can simultaneously satisfy the planar information, inclined plane information and straight line information required for calibration.

[0041] Reference Figures 1 to 3 As shown, in some embodiments of this application, the above-mentioned calibration unit 120 is provided on both sides of the device body 110, so that the industrial camera 200 arranged in the vertical direction can be calibrated simultaneously. The calibration unit 120 on both sides constitutes a mirror symmetry.

[0042] Reference Figures 1 to 3 As shown in some embodiments of this application, multiple identical calibration units 120 can be provided on one side of the device body 110. More specifically, the number of calibration units 120 is an odd number, so that one calibration unit 120 can be used as a reference. Of course, the number of calibration units can be adjusted according to the number of cameras on site and the width of the field of view.

[0043] In some embodiments of this application, as an extension, the calibration unit 120 can gradually increase in size along a preset direction D, for example, by increasing the top calibration surface 121, the bottom calibration surface, and the distance between them by an arithmetic progression. This allows for better calibration (providing richer information) when dealing with parts with complex shapes.

[0044] Of course, multiple cameras can be arranged to scan simultaneously onto the calibration unit 120, so that the relative positional relationship between each camera can be known.

[0045] As a second aspect of this application, the calibration method of this application will be described below with reference to the accompanying drawings.

[0046] Reference Figures 4 to 7 As shown, the calibration method of this application is mainly implemented by using the calibration device 100 of this application.

[0047] In some embodiments of this application, the calibration method mainly includes the following steps: S100: Move the calibration device 100 along the preset direction D; S200: The industrial camera 200 to be calibrated scans the device body 110 and calibration unit 120 in the calibration device 100; the action of the camera to acquire images can be triggered by sensors such as encoders.

[0048] S300: Generates a camera model based on the scanning data of industrial camera 200; S400: The industrial camera 200 is calibrated by comparing the camera model with the real model of the calibration device 100.

[0049] Reference Figure 4 and Figure 5As shown, the calibration method of this application is mainly applicable to 3D industrial camera 200 (also known as 3D laser triangulation industrial camera 200); in some embodiments of this application, when calibrating, the laser light 210 of the industrial camera 200 is made perpendicular to the preset direction D, and the axis of the lens of the industrial camera 200 is made to intersect the preset direction D at an angle.

[0050] Reference Figure 7 As shown, step S400 specifically includes the following steps: S401: Obtain the parameters of industrial camera 200 based on the comparison between the camera model and the real model; S402: Obtain the transformation matrix between the industrial camera 200 coordinate system and the calibration device 100 coordinate system based on the comparison between the camera model and the real model; S403: Stores the data of the transformation matrix.

[0051] More specifically, contour processing algorithms (such as the Canny edge detection algorithm) can be used to solve for camera parameters, including focal length, principal point coordinates, distortion coefficients, etc.; then the transformation matrix is ​​regenerated and the compensation values ​​are burned into the underlying storage unit of the industrial camera 200.

[0052] In some embodiments of this application, the accuracy of the industrial camera 200 can also be evaluated through calibration, specifically including the following steps: calculating the calibration error and analyzing the accuracy of the intrinsic parameters of the industrial camera 200. The calibration results can be verified by testing the measurement accuracy of the calibration device 100 at different heights. If necessary, the calibration device 100 can be adjusted at different positions and heights within the field of view to re-optimize the calibration data.

[0053] The transformation between the production line coordinate system and the camera coordinate system can be achieved by rotation and translation. The specific method is a technical solution well known to those skilled in the art, and it is not the focus of this application, so it will not be described in detail here.

[0054] The secondary calibration performed in this application is to obtain the area in the camera's field of view where the part to be inspected performs better (generally, the area with higher resolution) by comparing the camera model and the real model, thereby avoiding the problem of poor inspection results caused by the mismatch between the better calibration area and the production line after the industrial camera 200 is installed on the production line.

[0055] When the industrial camera 200 is fixed on the production line, a positional relationship is established. The conveyor belt continuously transports the parts being measured, which means that the coordinate system of the workpiece is constantly changing. Moreover, the posture and position of each transported part cannot be consistent. Without calibration, this will cause great inconvenience to subsequent contour data extraction and processing.

[0056] When the industrial camera 200 is fixed on the production line, the calibration device 100 and calibration method of this application are used to scan the camera outline (camera model) of the calibration device 100 and compare it with the actual outline (real model) of the calibration device 100 to obtain the conversion formula between the two models, thereby correcting the deviation of the scan field of view and enabling numerical interpolation in subsequent measurements.

[0057] The solution of this application can also output contour correction. An origin coordinate system is set on each measured part. After scanning to obtain the contour, the origin and coordinate axis are first identified. After identification, coordinate translation and rotation are performed, and then the contour is compared with the real contour to make corrections to achieve contour correction.

[0058] The above description is merely a selection of preferred embodiments of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in the embodiments of this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in the embodiments of this disclosure.

Claims

1. A calibration device suitable for industrial cameras, characterized in that: The calibration device includes: The device body extends at least along a predetermined direction; The calibration unit is arranged at least on at least one side of the device body along the preset direction; The calibration unit protrudes from the main body of the device.

2. The calibration device according to claim 1, characterized in that: The device body has a body base surface, which is constructed as a plane parallel to the preset direction.

3. The calibration device according to claim 2, characterized in that: The device body is constructed as a rectangular body; the calibration unit is located on the largest rectangular surface of the rectangular body.

4. The calibration device according to any one of claims 1 to 3, characterized in that: The calibration unit has a top calibration surface; the top calibration surface is constructed as a plane parallel to the preset direction; the top calibration surface is disposed on the top of the calibration unit.

5. The calibration device according to claim 4, characterized in that: The calibration unit has a side calibration surface; the side calibration surface is constructed as a plane that intersects the preset direction at an angle; the outline of the side calibration surface is an isosceles trapezoid.

6. A calibration method suitable for industrial cameras, characterized in that: The calibration method uses the calibration apparatus described in any one of claims 1 to 5.

7. The calibration method according to claim 6, characterized in that: The calibration method includes: The calibration device is moved along the preset direction; The industrial camera to be calibrated scans the device body and calibration unit in the calibration apparatus; A camera model is generated based on the scanning data from the industrial camera; The calibration of the industrial camera is completed by comparing the camera model with the actual model of the calibration device.

8. The calibration method according to claim 7, characterized in that: The laser beam from the industrial camera is made perpendicular to the preset direction.

9. The calibration method according to claim 8, characterized in that: The axis of the lens of the industrial camera is tilted to intersect with the preset direction.

10. The calibration method according to claim 9, Its features are: The step of calibrating the industrial camera by comparing the camera model with the actual model of the calibration device includes: The parameters of the industrial camera are obtained by comparing the camera model with the real model; The transformation matrix between the industrial camera coordinate system and the calibration device coordinate system is obtained based on the comparison between the camera model and the real model. Save the data of the transformation matrix.

Images