Correction method and correction device

Abstract

A calibration method and apparatus are provided that can easily determine the relative positional relationship between a probe head and a probe ball. The calibration method includes: a movement step in which the probe ball is moved along a path along the surface of the calibration ball while the probe head is in contact with the surface of the calibration ball; a self-position estimation step in which, during the movement step, the position and orientation of the probe head are detected based on images of a target group captured by a camera mounted on the probe head; and a calibration step in which the relative positional relationship between the probe head and the probe ball is determined based on the detection results of the self-position estimation step.

Description

Technical Field

[0001] This invention relates to a method and apparatus for calibrating probe tips. Background Technology

[0002] Previously, robots were equipped with portable coordinate measuring machines (CMMs) to automatically measure large workpieces. While portable CMMs have gradually met the accuracy requirements of around tens of μm, bridge-type CMMs are still used for high-precision requirements below ten μm.

[0003] Furthermore, as a technique for achieving accuracy around tens of μm, measurement methods utilizing laser trackers and markers are known (see, for example, Patent Document 1). These methods have elevation and azimuth tilting functions at the base station and also include distance sensors or cameras to calculate the distance and orientation of the measuring head. According to this measurement method, due to the long range of motion of the tilting mechanism and the long range of the distance sensor, measurements can be performed over a wide area.

[0004] However, in measurement methods that utilize laser trackers, markers, etc., the measurement accuracy tends to deteriorate as the distance between the reference station and the measuring head increases, mainly due to the limit of the angular accuracy of the swing head mechanism.

[0005] On the other hand, there is a known method for detecting the camera's own position (position and pose) based on an image obtained from a target whose position is known in three-dimensional space, captured by the camera (for example, see Patent Document 2). According to this method, by establishing a correlation between the position of each target in three-dimensional space and the position of each target in the captured image, it has the advantage of being able to obtain high accuracy (less than 5 μm) with a relatively simple mechanism.

[0006] Prior art literature

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2020-148515

[0009] Patent Document 2: Japanese Patent Application Publication No. 2022-30807 Summary of the Invention

[0010] -The problem the invention aims to solve-

[0011] However, in a three-dimensional coordinate measuring machine, a probe head (measuring head) is connected to a probe, and a probe ball (measuring element) is placed at the front end of the probe. When measuring the three-dimensional coordinates of a workpiece, the probe head is moved relative to the workpiece to bring the probe ball into contact with the workpiece. At this time, the coordinates (probe coordinates) indicating the position of the probe ball in contact with the workpiece are measured, and the three-dimensional coordinates of the workpiece are calculated based on the measurement result.

[0012] By mounting a camera on such a probe head and using the camera to photograph the target, the probe head's own position (position and orientation) can be detected based on the image.

[0013] However, in order to determine the three-dimensional coordinates of the workpiece, it is necessary not only to determine the position of the probe head itself, but also to determine the position of the probe ball in the probe head coordinate system (i.e., the relative positional relationship between the probe head and the probe ball).

[0014] One method for determining the position of the probe ball in the probe head coordinate system is, for example, using... Figure 7 The method described is based on the clamp 110. The clamp 110 is cylindrical, with a conical recess 112 on its upper surface. Furthermore, a spherical groove 114 is provided at the bottom of the recess 112. In this method, with the probe ball 104, located at the front end of the probe 102 of the probe head 100, positioned in the spherical groove 114, the probe head 100 is precessed at various tilt angles. At this time, the center point of the probe ball 104 is fixed in a fixed position regardless of the orientation of the probe head 100. Using this relationship, the position of the probe ball 104 in the probe head coordinate system can be determined.

[0015] However, the precession of the probe head 100 performed in the aforementioned method requires careful handling to prevent the shaft (including the probe 102) connecting the probe ball 104 and the probe head 100 from bending, which presents a drawback in terms of difficulty in automation. Furthermore, the radius of the probe ball 104 needs to be determined using other methods, leading to increased labor and costs.

[0016] Furthermore, in the case of a laser tracker, the reflector in contact with the workpiece can be selected to be a spherical structure, thus eliminating the need for precession at various tilt angles as described above. However, the radius of the spherical reflector needs to be investigated beforehand in other measuring machines, leading to increased labor and costs, similar to the situation described above. Moreover, the measurement accuracy of the laser tracker is also susceptible to being affected by the manufacturing accuracy of the spherical reflector (the accuracy of the optical center and the center of the sphere).

[0017] The present invention was made in view of the following circumstances, and its object is to provide a correction method and correction device that can easily determine the relative positional relationship between the probe head and the probe ball.

[0018] -Methods used to solve problems-

[0019] The present invention is constructed in the following manner to achieve the above objectives.

[0020] The first method involves a correction method comprising: a movement step in which the probe ball of the probe head is in contact with the surface of the correction ball, and the probe ball is moved along a path along the surface of the correction ball; a self-position estimation step in which, during the movement step, the position and orientation of the probe head are detected based on images of the target group captured by a camera mounted on the probe head; and a correction step in which the relative positional relationship between the probe head and the probe ball is determined based on the detection results of the self-position estimation step.

[0021] The correction method involved in the second method is a three-dimensional path along the surface of the correction sphere, as in the first method.

[0022] The third method involves a correction method that, in the second method, calculates the radius of the probe ball and its relative positional relationship together.

[0023] The fourth method involves a correction method in which, in the first method, the path is a path along the plane of the surface of the correction sphere.

[0024] The fifth method of the calibration device includes: an image acquisition unit that acquires an image of a target group captured by a camera mounted on the probe head; a self-position estimation unit that detects the position and orientation of the probe head based on the image; and a calibration processing unit that determines the relative positional relationship between the probe head and the probe ball based on the result of the detection of the position and orientation of the probe head by the self-position estimation unit during a contour measurement that moves the probe ball along the surface of the calibration ball.

[0025] -Invention Effects-

[0026] According to the present invention, the relative positional relationship between the probe tip and the probe ball can be easily determined. Attached Figure Description

[0027] Figure 1 This is a block diagram illustrating the self-position estimation system involved in this embodiment.

[0028] Figure 2 This is a schematic diagram showing the general structure of the self-position estimation system involved in this embodiment.

[0029] Figure 3 This is an explanatory diagram used to illustrate the camera projection model.

[0030] Figure 4 This is a flowchart illustrating an example of the self-position estimation process performed by the self-position estimation device in this embodiment.

[0031] Figure 5 It is a diagram that models the positional relationship between the probe head, the probe ball, and the calibration ball.

[0032] Figure 6 This is a flowchart illustrating an example of the correction method involved in this embodiment.

[0033] Figure 7 This diagram is used to illustrate previous correction methods. Detailed Implementation

[0034] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0035] [Self-position estimation system]

[0036] Figure 1 This is a block diagram illustrating the self-position estimation system 10 involved in this embodiment. Figure 2 This is a schematic diagram showing the general structure of the self-position estimation system 10 involved in this embodiment.

[0037] like Figure 1 as well as Figure 2 As shown, the self-position estimation system 10 includes a probe head 12, a target group 14, and a self-position estimation device 50. In this embodiment, the self-position estimation device 50 and the probe head 12 are separate components, but the probe head 12 may also have at least some of the functions of the self-position estimation device 50.

[0038] The probe head 12 is a portable three-dimensional coordinate measuring machine for measuring the three-dimensional coordinates of a workpiece (not shown). The probe head 12 includes a contact-type (contact probe type) probe 18. The probe 18 is configured to include a probe 30 (described later) and a probe ball 32. By bringing the probe 18 into contact with the workpiece while the user holds the probe head 12, the three-dimensional coordinates of the measurement point on the workpiece can be obtained.

[0039] The probe head 12 has a self-position estimation function. By taking pictures of the target group 14 by the camera 20 mounted on the probe head 12, the self-position estimation device 50 described later can estimate the self-position (position and attitude) of the probe head 12.

[0040] like Figure 2 As shown, the target group 14 is formed by arranging multiple targets 24 in a two-dimensional manner. Each target 24 is formed into a dot or circular shape and is arranged at intervals between each other. Furthermore, each target 24 may also be composed of a small point light source (point light source) such as an LED. In addition, the relative positions of the targets 24 in the target group 14 are known. Furthermore, the shape and size of each target 24 in the target group 14 are also known.

[0041] In addition, various fixing or supporting components can be used as long as the target group 14 can be fixed or supported in a given position.

[0042] [Self-position estimation device]

[0043] Next, the self-position estimation device 50 will be described. For example... Figure 1 As shown, the self-position estimation device 50 is configured, for example, by a personal computer, and includes a processing unit 52 and a storage unit 54. Furthermore, a camera 20 mounted on the probe head 12 is connected to the self-position estimation device 50. The connection method to the camera 20 is not particularly limited; it can be via a cable, or via a wired or wireless network. Additionally, the self-position estimation device 50 includes a correction processing unit 70, which functions as a correction device according to the present invention.

[0044] The storage unit 54 stores the control program and various data. The storage unit 54 may be composed of, for example, a hard disk drive (HDD) or a solid state drive (SSD). The storage unit 54 may include temporary storage elements composed of RAM (Random Access Memory) such as DRAM (Dynamic Random Access Memory) or SRAM (Static Random Access Memory), and may also function as a working area of ​​the arithmetic processing unit 52.

[0045] The target images, which will be described later, are stored in the storage unit 54. In addition, the storage unit 54 also stores information related to the shape, size, and configuration of each target 24 constituting the target group 14 (target group information).

[0046] The arithmetic processing unit 52 performs various arithmetic operations implemented by the self-position estimation device 50. The arithmetic processing unit 52 includes arithmetic circuitry composed of various processors and memory. These processors include CPUs (Central Processing Units), GPUs (Graphics Processing Units), ASICs (Application Specific Integrated Circuits), and programmable logic devices [such as SPLDs (Simple Programmable Logic Devices), CPLDs (Complex Programmable Logic Devices), and FPGAs (Field Programmable Gate Arrays)]. Furthermore, the various functions of the arithmetic processing unit 52 can be implemented by a single processor or by multiple processors of the same or different types.

[0047] The arithmetic processing unit 52 reads and executes the control program stored in the storage unit 54, thereby functioning as the image acquisition unit 60, the self-position estimation unit 62, the determination processing unit 64, and the correction processing unit 70. The self-position estimation unit 62 includes a feature point detection unit 66 and an optimization calculation unit 68.

[0048] Furthermore, the image acquisition unit 60 is an example of the image acquisition unit of the present invention. The self-position estimation unit 62 is an example of the self-position estimation unit of the present invention. The correction processing unit 70 is an example of the correction processing unit of the present invention.

[0049] [Camera projection model]

[0050] Before explaining the self-position estimation process performed by the self-position estimation device 50 in this embodiment, the camera projection model, which is a prerequisite for it, will be explained. Figure 3 This is an explanatory diagram used to illustrate the camera projection model.

[0051] like Figure 3 As shown, the world coordinate system (world coordinate system) Σ w It is a coordinate system that represents a position in three-dimensional space (actual space), with the origin as O. w With mutually orthogonal X w Axis, Y w Axis, Z w The axes are a three-dimensional orthogonal coordinate system. Additionally, there is a world coordinate system Σ. wAny coordinate system can be used as long as the position in three-dimensional space (3D position) can be determined. Camera coordinate system Σ c The optical axis center O of camera 20 c Starting from the origin, starting from the origin O c Let the rightward direction be X c Axis, set the downward direction to Y c And set the optical axis direction to Z. c A three-dimensional orthogonal coordinate system of axes. Image coordinate system Σ s Therefore, from the camera coordinate system Σ c Origin O c To Z c The origin is located at the upper left of the image plane IP, which is oriented away from the focal length f, and intersects with the X-axis. c axis and Y c A two-dimensional orthogonal coordinate system (pixel coordinate system) with U-axis and V-axis parallel to each other.

[0052] First, point P (the object point) in three-dimensional space is in the world coordinate system Σ w coordinates (x) w y w z w The camera coordinate system Σ can be transformed using the rotation matrix R and translation vector t of camera 20, as shown in equation (1) below. c The coordinates (x, y, z) in the equation.

[0053] [Mathematical Expression 1]

[0054]

[0055] Here, [R|t] w，c It is used to transfer coordinates from the world coordinate system Σ w Towards the camera coordinate system Σ c The transformation matrix (external parameter matrix) for coordinate transformation represents the world coordinate system Σ. w The pose and position of camera 20 in the image. [R|t] w，c Each component r 11 r 12 ... r 33 t x t y t z These are called the camera's external parameters.

[0056] Next, from the camera coordinate system Σ c When the coordinates (pixel coordinates) of the projection point Q of the image plane IP from point P located at (x, y, z) are set to (u, v), the following equations (2) to (7) hold true.

[0057] [Mathematical Expression 2]

[0058]

[0059] [Mathematical Expression 3]

[0060]

[0061] [Mathematical Expression 4]

[0062]

[0063] [Mathematical Expression 5]

[0064]

[0065] [Mathematical Expression 6]

[0066]

[0067] [Mathematical Expression 7]

[0068]

[0069] Here, (x′, y′) represents the coordinate system Σ from the camera coordinate system. c Observe the coordinates of the projection point of point P, which is located at (x, y, z), onto the normalized image plane (z = 1). Furthermore, (x″, y″) represents the coordinates of the projection point (distorted point) of point P onto the normalized image plane, taking into account the lens distortion of camera 20.

[0070] In addition, f x f y This represents the focal length in the x and y directions, expressed in pixels. Additionally, c... x c y Representing the image coordinate system Σ s The optical center (the position where the optical axis of camera 20 intersects the image plane IP, the optical center of the pixel unit). Furthermore, k1, k2, and k3 are the distortion coefficients in the radial direction, and p1 and p2 are the distortion coefficients in the tangential direction. In this specification, the focal length f... x f y Optical Center c x c y The internal parameters of camera 20 are referred to as the distortion coefficients k1, k2, k3, p1, and p2, which are called the distortion parameters of camera 20.

[0071] [Method for estimating one's own position]

[0072] Next, the processing steps of the self-position estimation process performed by the self-position estimation device 50 in this embodiment (an example of a self-position estimation method) will be described. Figure 4 This is a flowchart illustrating an example of the self-position estimation process performed by the self-position estimation device 50 (processing unit 52) ​​in this embodiment. Furthermore, at the beginning of this flowchart, the camera 20 has already been calibrated, and the camera matrix K, which includes the internal parameters (focal length, optical center) and distortion parameters (distortion coefficients) of the camera 20, is known. In addition, the relative positional relationship between the camera 20 and the probe head 12 is also known.

[0073] First, such as Figure 2 As shown, the target group 14 is photographed by the camera 20 mounted on the probe head 12 (step S10). The image (target image) captured by the camera 20 is sent to the self-position estimation device 50. If the target image is sent to the self-position estimation device 50, the image acquisition unit 60 acquires the target image and stores it in the storage unit 54.

[0074] Next, the self-position estimation unit 62 estimates the position and orientation (self-position) of the probe head 12 based on the target image captured by the camera 20. The processing performed by the self-position estimation unit 62 will be described below.

[0075] First, the feature point detection unit 66 performs feature point detection processing (step S12) to detect multiple feature points from the target image.

[0076] Specifically, the feature point detection unit 66 reads the target image from the storage unit 54. Then, after performing given image processing (grayscale conversion, etc.) on the read target image, the feature point detection unit 66 detects feature points (image points) representing the positions of each target 24 in the target image, and calculates the target image (image plane IP; reference). Figure 3 The coordinates (pixel coordinates) of each feature point on the target image are used. Additionally, the position of the centroid of target 24 is detected as a feature point on the target image.

[0077] Next, the optimization calculation unit 68 uses the feature points detected by the feature point detection unit 66 to calculate the position and pose of the probe head 12 with the minimum reprojection error of each target 24 in the target group 14 through optimization calculation (step S14). Specifically, the optimization calculation unit 68 calculates the position and pose of the camera 20 through optimization calculation based on the correspondence between each feature point on the target image and the object points representing the positions of each target 24 in the corresponding three-dimensional space. Since the relative positional relationship between the camera 20 and the probe head 12 is known, if the position and pose of the camera 20 are known, the position and pose of the probe head 12 can be calculated based on the relative positional relationship between the camera 20 and the probe head 12. Thus, the position and pose of the probe head 12 are detected as information representing the position of the probe head 12 itself.

[0078] The self-position estimation unit 62 stores information (probe head self-position information) representing the position and orientation of the probe head 12 as determined as described above in the storage unit 54. Furthermore, the probe head self-position information stored in the storage unit 54 is used when calculating the three-dimensional coordinates of the workpiece using the probe head 12.

[0079] Next, it is determined whether to repeatedly perform the self-position estimation process of the probe head 12 (step S16). Specifically, while the probe head 12 is measuring the three-dimensional coordinates of the workpiece, the determination processing unit 64 determines whether the self-position estimation process of the probe head 12 is still being performed ("yes" in step S16), and repeats the process from step S10 to step S16. Thus, the self-position estimation process of the probe head 12 is continuously and repeatedly performed during the measurement of the three-dimensional coordinates of the workpiece by the probe head 12.

[0080] On the other hand, when the measurement of the three-dimensional coordinates of the workpiece by the probe head 12 is completed, the determination processing unit 64 determines the end of the self-position estimation processing of the probe head 12 (in step S16, it is "No"), and ends this flowchart.

[0081] [Probe head calibration method]

[0082] Next, the calibration method for probe head 12 will be explained.

[0083] Figure 5 This is a diagram that models the positional relationship between the probe head 12, the probe ball 32, and the calibration ball 34. The probe ball 32 is attached to the probe head 12 and includes the probe 18 (see reference). Figure 2 The probe tip ball of 30. Figure 5 In the middle, the radius of the correction sphere 34 is set as r. sp Let the radius of the probe ball 32 be r. stylus .

[0084] like Figure 5 As shown, when the probe ball 32 is in contact with the surface of the calibration ball 34 for measurement (probing), the following formula holds.

[0085] [Mathematical Expression 8]

[0086]

[0087] In addition, in equation (8), x stylus、t It represents the world coordinate system Σ w The vector (position vector) representing the position of the center point of the probe ball 32. Furthermore, x sp It represents the world coordinate system Σ w The vector (position vector) represents the position of the center point of the calibration sphere 34. Additionally, the subscript t indicates a parameter that depends on a specific moment or scenario (i.e., the position and orientation of the probe head 12) (the same applies below).

[0088] Here, we will start from the probe head coordinate system (the coordinate system based on probe head 12) ∑ h To the world coordinate system ∑ w Let the coordinate transformation matrix be T. t Coordinate transformation matrix T t From the rotation matrix R T，t Translation vector t T，t Definition, T t =[R T，t |t T，t Furthermore, if we use s to represent the probe head coordinate system Σ h If the vector of the position of the center point of the probe ball 32 is given, then the following equation (9) holds.

[0089] [Mathematical Expression 9]

[0090]

[0091] Next, substituting equation (9) into equation (8), we obtain the following equation (10).

[0092] [Mathematical Expression 10]

[0093]

[0094] Here, if the aforementioned self-position estimation process (i.e., the process of estimating the self-position (position and orientation) of the probe head 12 based on the target image obtained by the camera 20 of the probe head 12 capturing the target group 14) is continuously performed during the calibration process of the probe head 12, then the world coordinate system Σ w With probe head coordinate system Σ h The relative positions are known. Therefore, from the probe head coordinate system Σh To the world coordinate system Σ w coordinate transformation matrix T t It is known that the rotation matrix R, which is a component of it, is... T，t and translation vector t T，t It is also known. Furthermore, since the correction sphere 34 uses a sphere with a known radius, its radius r... sp This is also known.

[0095] On the other hand, the probe head coordinate system Σ h The vector s of the center point of the probe ball 32 and the radius r of the probe ball 32. stylus , and represent the world coordinate system ∑ w The vector x representing the position of the center point of the correction sphere 34 in the middle. sp unknown.

[0096] These unknown parameters (s, r) stylus x sp The answer can be obtained through optimization. Optimization can be performed using various nonlinear methods such as the Newton-Raphson method and the nonlinear conjugate gradient method, but since these are generally known methods, their explanation is omitted here.

[0097] In this embodiment, the calibration process of the probe head 12 is performed using the calculation algorithm described above. Specifically, a contour measurement is performed, in which the probe ball 32 is moved along a path (calibration path) on the surface of the calibration ball 34 while the probe ball 32 is in contact with the surface of the calibration ball 34. Furthermore, during the contour measurement, the self-position estimation process of the probe head 12 is continuously performed.

[0098] As a correction path during contour measurement, it is sufficient that the path on the surface of the correction sphere 34 is at least a three-dimensional path. For example, a spiral path on the surface of the correction sphere 34 is preferred. Furthermore, it can be a path combining multiple planar paths with different diameters or directions, or it can be a random path. Additionally, as will be described later, given the known radius r of the probe sphere 32... stylus In this case, the path on the surface of the correction sphere 34 does not necessarily need to be a three-dimensional path.

[0099] By simultaneously performing contour measurement and self-position estimation in parallel, the position and orientation of the probe head 12 can be obtained at various positions of the probe ball 32, which moves along the path on the surface of the calibration ball 34. That is, with the distance between the center point of the probe ball 32 and the center point of the calibration ball 34 fixed, multiple world coordinate systems Σ can be obtained. w The positions of the probe heads 12 and their own positions with different orientations (i.e., the probe head rotation matrix R) are within the range of the probe heads 12. T，tand translation vector t T，t ).

[0100] Furthermore, during contour measurement, the trajectory of the center point of the probe ball 32 becomes a path offset from the surface of the calibration ball 34 by the radius r of the probe ball 32. stylus The trajectory of the quantity movement.

[0101] Using the position of the probe head 12 obtained in this way, the correction parameters (s, r) as unknown parameters are obtained through optimization calculation in the above equation (10). stylus x sp ).

[0102] In addition, given the radius r of the probe ball 32 stylus In this case, the correction path during contour measurement can also be the path of the plane on the surface of the correction sphere 34. However, even if the radius r of the probe sphere 32 is known... stylus In this case, the correction path during contour measurement can of course also be a three-dimensional path.

[0103] Next, the calibration method for the probe head 12 in this embodiment (an example of the calibration method of the present invention) will be described. Figure 6 This is a flowchart illustrating an example of a calibration method for probe head 12.

[0104] First, the probe head 12 is used to perform a contour measurement on the calibration ball 34 (step S20). During the contour measurement, with the probe ball 32 of the probe 30 attached to the probe head 12 in contact with the surface of the calibration ball 34, the probe ball 32 is moved along a path (correction path) on the surface of the calibration ball 34. As described above, the correction path used in the contour measurement is preferably a three-dimensional path such as a spiral on the surface of the calibration ball 34.

[0105] Furthermore, during the contour measurement, a self-position estimation process for the probe head 12 is performed (step S22). As described above, the self-position estimation unit 62 estimates the self-position (position and orientation) of the camera 20 based on target images obtained by the camera 20 mounted on the probe head 12 capturing images of the target group 14. Thus, the position and orientation of the probe head 12 are determined at each position the probe ball 32 moves during the contour measurement. The processing in the self-position estimation unit 62 is as described above, and therefore will not be explained here.

[0106] Next, the correction processing unit 70 solves equation (10) above by means of its own position data, which represents the position and posture of the probe head 12 obtained during the contour measurement, and thereby obtains the correction parameters (s, r). stylus x sp (Step S24).

[0107] Next, the calibration processing unit 70 outputs calibration parameters to the output unit (not shown) (step S26). Furthermore, the calibration processing unit 70 stores the calculated calibration parameters in the storage unit 54. Therefore, when calculating the three-dimensional coordinates of the workpiece using the probe head 12, the calculation of the three-dimensional coordinates is performed while the workpiece has been calibrated using the calibration parameters stored in the storage unit 54.

[0108] thus, Figure 6 The flowchart shown ends here.

[0109] 〔Effect〕

[0110] Next, the effects of this implementation method will be explained.

[0111] According to this embodiment, by using the probe head 12 to perform contour measurement on the calibration ball 34 and performing self-position estimation processing of the position and posture of the probe head 12, the relative positional relationship between the probe head 12 and the probe ball 32 can be easily determined using the results.

[0112] Furthermore, according to this embodiment, by setting the path on the surface of the calibration ball 34 as a calibration path that becomes a three-dimensional path during the contour measurement, the radius of the probe ball 32 can also be determined together with the above-mentioned relative positional relationship.

[0113] Furthermore, according to this embodiment, when the radius of the probe ball 32 is known, the calibration of the probe head 12 can be performed more easily by setting the calibration path during contour measurement to the path of the plane on the surface of the calibration ball 34.

[0114] Furthermore, the probe head 12 is not limited to being held by the user for workpiece measurement. For example, the probe head 12 can also be installed at the end of a multi-joint robotic arm (end effector), and the probe head 12 can be moved by controlling the movement of the robotic arm, thereby measuring the three-dimensional coordinates of the workpiece through the probe head 12.

[0115] Furthermore, this embodiment illustrates a case where the target group 14 is composed of a two-dimensional arrangement of multiple targets 24 arranged in a dot pattern, but it is not limited to this. For example, the target group 14 may also be composed of a grid pattern or a checkerboard pattern as disclosed in Patent Document 2. Additionally, the target group 14 may be various two-dimensional patterns including AR markers (Augmented Reality Markers) or QR codes (Quick Response codes, registered trademarks).

[0116] The embodiments of the present invention have been described above, but the present invention is not limited to the above examples. Of course, various improvements and modifications can be made without departing from the spirit of the present invention.

[0117] -Explanation of Figure Markers-

[0118] 10…Self-position estimation system, 12…Probe head, 14…Target group, 18…Probe, 20…Camera, 24…Target, 30…Probe, 32…Probe ball, 34…Calibration ball, 50…Self-position estimation device, 52…Computation processing unit, 54…Storage unit, 60…Image acquisition unit, 62…Self-position estimation unit, 64…Decision processing unit, 66…Feature point detection unit, 68…Optimization calculation unit, 70…Calibration processing unit.

Claims

1. A calibration method, characterized in that, include: In the moving step, with the probe ball of the probe tip in contact with the surface of the calibration ball, the probe ball is moved along the path of the surface of the calibration ball; The self-position estimation step involves detecting the position and orientation of the probe head based on images of the target group captured by a camera mounted on the probe head during the movement step. as well as The calibration step involves determining the relative positional relationship between the probe head and the probe ball based on the detection results of the self-position estimation step.

2. The correction method according to claim 1, wherein, The path is a three-dimensional path along the surface of the correction sphere.

3. The correction method according to claim 2, wherein, The calibration step calculates the radius of the probe ball together with the relative positional relationship.

4. The correction method according to claim 1, wherein, The path is a path along the plane of the surface of the correction sphere.

5. A calibration device, characterized in that, have: The image acquisition unit acquires images of the target group captured by a camera mounted on the probe head; The self-position estimation unit detects the position and orientation of the probe head based on the image; as well as The calibration processing unit determines the relative positional relationship between the probe head and the probe ball based on the results of the position and posture detection of the probe head performed by the self-position estimation unit during the conformal measurement that moves the probe ball along the surface of the calibration ball.

Images