Calibration method and calibration device

Abstract

To provide a calibration method and a calibration device that can easily obtain a relative positional relationship between a probe head and stylus ball.SOLUTION: A calibration method includes: a movement step of moving a stylus ball of a probe head along a path on a surface of a calibration ball in a state in which the stylus ball is in contact with the surface of the calibration ball; a self-position estimation step of detecting a position and posture of the probe head on the basis of images that a camera mounted on the probe head has captured a target group while the movement step is being performed; and a calibration step of obtaining a relative positional relationship between the probe head and the stylus ball on the basis of the detection result of the self-position estimation step.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for calibrating a probe head. [Background technology]

[0002] Conventionally, portable three-dimensional coordinate measuring machines (CMMs) have been equipped on robots to automatically measure large workpieces. Portable three-dimensional coordinate measuring machines are gradually meeting the requirements for precision of several tens of microns, but currently bridge-type three-dimensional coordinate measuring machines are used for precision requirements of 10 microns or less.

[0003] Furthermore, measurement methods using laser trackers and markers are known as technologies for achieving accuracy of the order of several tens of micrometers (see, for example, Patent Document 1). These have a base station equipped with a tilt function for adjusting elevation and azimuth angles, and are further equipped with a distance sensor or camera to calculate the distance and attitude of the measurement head. With this measurement method, the movable range of the tilt mechanism and the measurement range of the distance sensor are long, making it possible to measure over a wide range.

[0004] However, in measurement methods using laser trackers or markers, the measurement accuracy tends to deteriorate as the distance between the base station and the measurement head increases, mainly due to limitations in the angular accuracy of the oscillating mechanism.

[0005] Meanwhile, a method is known for detecting the camera's own position (position and attitude) from an image captured by the camera of a target whose position in three-dimensional space is known (see, for example, Patent Document 2). This method has the advantage of easily achieving high accuracy (5 μm or less) with a relatively simple mechanism by performing calculations that associate the position of each target in three-dimensional space with the position of each target in the captured image. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-148515 [Patent Document 2] Japanese Patent Publication No. 2022-30807 Summary of the Invention [Problem to be solved by the invention]

[0007] A stylus is connected to the probe head (measuring head) of a three-dimensional coordinate measuring machine, and a stylus ball (measuring element) is attached to the tip of the stylus. When measuring the three-dimensional coordinates of a workpiece, the probe head is moved relative to the workpiece to bring the stylus ball into contact with the workpiece. At this time, coordinates indicating the position of the stylus ball that has come into contact with the workpiece (stylus coordinates) are measured, and the three-dimensional coordinates of the workpiece are calculated based on the measurement results.

[0008] By mounting a camera on such a probe head and using the camera to capture an image of a target, the probe head's own position (position and attitude) can be detected from the image.

[0009] However, in order to measure the three-dimensional coordinates of the workpiece, it is necessary to determine not only the self-position of the probe head but also the position of the stylus ball in the probe head coordinate system (i.e., the relative positional relationship between the probe head and the stylus ball).

[0010] One method for determining the position of the stylus ball in the probe head coordinate system is to use a jig 110 as shown in FIG. 7. This jig 110 is cylindrical, with a conical recess 112 provided on its top surface. A spherical groove 114 is provided at the bottom of the recess 112. In this method, the stylus ball 104 provided at the tip of the stylus 102 in the probe head 100 is placed in the spherical groove 114, and the probe head 100 is then precessed at various inclination angles. During this process, the center of the stylus ball 104 remains fixed at a constant position regardless of the orientation of the probe head 100. By utilizing this relationship, the position of the stylus ball 104 in the probe head coordinate system can be determined.

[0011] However, the precession of the probe head 100 performed in the above-described method must be performed carefully so as not to bend the shaft (including the stylus 102) connecting the stylus ball 104 and the probe head 100, which has the drawback of making automation difficult. Also, the radius of the stylus ball 104 must be determined by a different method, which increases the effort and cost.

[0012] Furthermore, with a laser tracker, it is possible to select a spherical reflector that comes into contact with the workpiece, eliminating the need for precession at various tilt angles as described above. However, the radius of the spherical reflector must be checked in advance using a separate measuring device, which, like the previous case, increases the amount of work and costs involved. Another problem is that the measurement accuracy of a laser tracker is easily affected by the manufacturing accuracy of the spherical reflector (the accuracy of the optical center and the center of the sphere).

[0013] The present invention has been made in view of the above circumstances, and has as its object to provide a calibration method and calibration device that can easily determine the relative positional relationship between a probe head and a stylus ball. [Means for solving the problem]

[0014] In order to achieve the above object, the present invention comprises the following aspects.

[0015] The calibration method according to the first aspect includes a movement step in which the stylus ball of the probe head is moved along a path on the surface of the calibration ball while the stylus ball is in contact with the surface of the calibration ball, a self-position estimation step in which the position and attitude of the probe head are detected based on images of a group of targets captured by a camera mounted on the probe head while the movement step is being performed, and a calibration step in which the relative positional relationship between the probe head and the stylus ball is determined based on the detection results of the self-position estimation step.

[0016] In the calibration method according to a second aspect, in the first aspect, the path is a three-dimensional path along the surface of a calibration sphere.

[0017] A calibration method according to a third aspect is the second aspect, wherein the calibration step determines the radius of the stylus ball as well as the relative positional relationship.

[0018] A calibration method according to a fourth aspect is the calibration method of the first aspect, wherein the path is a planar path along the surface of the calibration sphere.

[0019] The calibration device according to the fifth aspect comprises an image acquisition unit that acquires images of a group of targets taken by a camera mounted on the probe head, a self-position estimation unit that detects the position and attitude of the probe head based on the images, and a calibration processing unit that determines the relative positional relationship between the probe head and the stylus ball based on the results of detection of the position and attitude of the probe head by the self-position estimation unit while a scanning measurement is being performed in which the stylus ball of the probe head is moved along a path on the surface of the calibration ball. [Effects of the Invention]

[0020] According to the present invention, the relative positional relationship between the probe head and the stylus ball can be easily determined. [Brief explanation of the drawings]

[0021] [Figure 1]1 is a block diagram showing a self-location estimation system according to an embodiment of the present invention; [Figure 2] 1 is a schematic diagram illustrating a schematic configuration of a self-position estimation system according to an embodiment of the present invention. [Figure 3] FIG. 10 is an explanatory diagram for explaining a camera projection model. [Figure 4] 10 is a flowchart illustrating an example of a self-position estimation process executed by the self-position estimation device of the present embodiment. [Figure 5] FIG. 1 is a diagram showing a model of the positional relationship between a probe head, a stylus ball, and a calibration ball. [Figure 6] 1 is a flowchart showing an example of a calibration method according to the present embodiment. [Figure 7] FIG. 1 is a diagram for explaining a conventional calibration method. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0023] [Self-location estimation system] Fig. 1 is a block diagram showing a self-location estimation system 10 according to this embodiment. Fig. 2 is a schematic diagram showing the schematic configuration of the self-location estimation system 10 according to this embodiment.

[0024] 1 and 2, the self-localization system 10 includes a probe head 12, a group of targets 14, and a self-localization device 50. In this embodiment, the self-localization device 50 is configured separately from the probe head 12, but the probe head 12 may include at least some of the functions of the self-localization device 50.

[0025] The probe head 12 is a portable three-dimensional coordinate measuring machine that measures the three-dimensional coordinates of a workpiece (not shown). The probe head 12 is equipped with a contact-type (touch probe) probe 18. The probe 18 includes a stylus 30 and a stylus ball 32, which will be described later. A user holds the probe head 12 and brings the probe 18 into contact with the workpiece to perform a measurement, thereby obtaining the three-dimensional coordinates of the measurement point on the workpiece.

[0026] The probe head 12 has a self-position estimation function, and when the camera 20 mounted on the probe head 12 photographs the target group 14, the self-position (position and attitude) of the probe head 12 can be estimated by the self-position estimation device 50 described below.

[0027] As shown in Fig. 2, the target group 14 is a group of multiple (large numbers of) targets 24 arranged two-dimensionally. Each target 24 is formed in a dot or point shape, and is arranged with a gap between each target 24. Each target 24 may be formed of a small point light source (point light source) such as an LED. The relative positions of the targets 24 in the target group 14 are known. The shape and size of each target 24 in the target group 14 are also known.

[0028] It should be noted that various fixing or supporting members may be used as long as they can fix or support the target group 14 at a predetermined position.

[0029] [Self-position estimation device] Next, the self-location estimation device 50 will be described. As shown in Fig. 1, the self-location estimation device 50 is configured, for example, by a personal computer or the like, and includes an arithmetic processing unit 52 and a storage unit 54. A camera 20 mounted on a probe head 12 is connected to the self-location estimation device 50. The method of connection with the camera 20 is not particularly limited, and the connection may be via a cable, or via a wired or wireless network. The self-location estimation device 50 includes a calibration processing unit 70, which will be described later, and functions as a calibration device of the present invention.

[0030] The storage unit 54 stores control programs and various data. The storage unit 54 is configured, for example, by a hard disk drive (HDD: Hard Disk Drive) or a semiconductor storage device (SSD: Solid State Drive). The storage unit 54 may include a temporary storage element configured, for example, by a random access memory (RAM) such as a dynamic random access memory (DRAM) or a static random access memory (SRAM), and may function as a work area for the arithmetic processing unit 52.

[0031] Target images, which will be described later, are stored in the storage unit 54. The storage unit 54 also stores information (target group information) regarding the shape, size, and arrangement of each target 24 that constitutes the target group 14.

[0032] The arithmetic processing unit 52 executes various arithmetic processing operations performed by the self-position estimation device 50. The arithmetic processing unit 52 includes an arithmetic circuit configured with various processors, memories, etc. The various processors include a central processing unit (CPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), and a programmable logic device (e.g., simple programmable logic device (SPLD), complex programmable logic device (CPLD), and field programmable gate array (FPGA)). Note that the various functions of the arithmetic processing unit 52 may be implemented by a single processor or by multiple processors of the same or different types.

[0033] The calculation processing unit 52 reads and executes a control program stored in the memory unit 54, thereby functioning as an image acquisition unit 60, a self-position estimation unit 62, a determination processing unit 64, and a calibration processing unit 70. The self-position estimation unit 62 includes a feature point detection unit 66 and an optimization calculation unit 68.

[0034] The image acquisition unit 60 is an example of an image acquisition unit of the present invention. The self-position estimation unit 62 is an example of a self-position estimation unit of the present invention. The calibration processing unit 70 is an example of a calibration processing unit of the present invention.

[0035] [Camera projection model] Before describing the self-location estimation process executed by the self-location estimation device 50 of this embodiment, the camera projection model that is the premise of the process will be described. Fig. 3 is an explanatory diagram for explaining the camera projection model.

[0036] As shown in Figure 3, the world coordinate system Σ w is a coordinate system that represents a position in three-dimensional space (real space), and its origin is O w and X w Axis, Yw axis, Z w The world coordinate system Σ is a three-dimensional Cartesian coordinate system with the axes as its coordinate axes. w Any coordinate system may be used as long as it can identify a position in three-dimensional space (three-dimensional position). c is the optical axis center O of the camera 20 c is the origin, and the origin O c From there, turn right and press X c axis, downward direction is Y c axis, the optical axis direction is Z c The image coordinate system Σ is a three-dimensional orthogonal coordinate system with the axes s is the camera coordinate system Σ c Origin of O c From Z c The origin is the upper left corner of the image plane IP, which is a focal length f away in the X direction. c axis and Y c It is a two-dimensional Cartesian coordinate system (pixel coordinate system) with the U axis and V axis in directions parallel to the y-axis and y-axis, respectively.

[0037] First, the world coordinate system Σ of a point P (object point) in three-dimensional space w Coordinates (x w , y w , z w ) is expressed in the camera coordinate system Σ using the rotation matrix R and translation vector t of the camera 20 as shown in the following equation (1): c can be converted to coordinates (x, y, z) in

[0038]

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[0039] where [R|t] w,c is the world coordinate system Σ w From the camera coordinate system Σ c is the transformation matrix (external parameter matrix) for transforming coordinates into the world coordinate system Σ w [R|t] represents the orientation and position of the camera 20 at the time of the w,c Each component r 11 , r 12 , …, r 33 , tx , t y , t z are called the extrinsic parameters of the camera.

[0040] Next, the camera coordinate system Σ c When point P, which is located at (x, y, z) as viewed from the left, is projected onto image plane IP, and the coordinates (pixel coordinates) of projected point Q are (u, v), the following relationships are established as shown in equations (2) to (7).

[0041]

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[0042]

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[0043]

number

[0044]

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[0045]

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[0046]

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[0047] where (x´, y´) is the camera coordinate system Σ c represents the coordinates of the projected point obtained by projecting point P, which is located at (x, y, z) as seen from the camera 20, onto the normalized image plane (z=1). Also, (x″, y″) represents the coordinates of the projected point (distorted point) obtained by projecting point P onto the normalized image plane when the lens distortion of the camera 20 is taken into consideration.

[0048] Also, f x , f y are the focal lengths in the x and y directions in pixels, and c x , c y is the image coordinate system Σ s where k1, k2, and k3 are radial distortion coefficients, and p1 and p2 are tangential distortion coefficients. x , f y , optical center c x , c y are called the internal parameters of the camera 20, and the distortion coefficients k1, k2, k3, p1, and p2 are called the distortion parameters of the camera 20.

[0049] [Self-position estimation method] Next, a processing procedure (an example of a self-location estimation method) of the self-location estimation process executed by the self-location estimation device 50 of this embodiment will be described. FIG. 4 is a flowchart showing an example of the self-location estimation process executed by the self-location estimation device 50 (arithmetic processing unit 52) ​​of this embodiment. Note that, at the start of this flowchart, it is assumed that the camera 20 has already been calibrated, and the camera matrix K including the internal parameters (focal length, optical center) and distortion parameters (distortion coefficients) of the camera 20 is known. It is also assumed that the relative positional relationship between the camera 20 and the probe head 12 is known.

[0050] 2, the target group 14 is photographed by the camera 20 mounted on the probe head 12 (step S10). The image (target image) photographed by the camera 20 is transmitted to the self-position estimation device 50. When the target image is transmitted to the self-position estimation device 50, the image acquisition unit 60 acquires the target image and stores it in the storage unit 54.

[0051] Next, the self-position estimation unit 62 estimates the position and attitude (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.

[0052] First, the feature point detection unit 66 executes a feature point detection process to detect a plurality of feature points from the target image (step S12).

[0053] Specifically, the feature point detection unit 66 reads the target image from the storage unit 54. Then, the feature point detection unit 66 performs predetermined image processing (such as grayscale conversion) on the read target image, detects feature points (image points) indicating the position of each target 24 from the target image, and determines the coordinates (pixel coordinates) of each feature point on the target image (image plane IP; see FIG. 3). Note that the position of the center of gravity of the target 24 is detected as the feature point on the target image.

[0054] Next, the optimization calculation unit 68 uses each feature point detected by the feature point detection unit 66 to determine, by optimization calculation, the position and orientation of the probe head 12 that minimizes the reprojection error of each target 24 in the target group 14 (step S14). Specifically, the optimization calculation unit 68 determines, by optimization calculation, the position and orientation of the camera 20 based on the correspondence between each feature point on the target image and the corresponding object point indicating the position of each target 24 in three-dimensional space. Since the relative positional relationship between the camera 20 and the probe head 12 is known, once the position and orientation of the camera 20 are known, the position and orientation of the probe head 12 can be determined from the relative positional relationship between the camera 20 and the probe head 12. As a result, the position and orientation of the probe head 12 are detected as information indicating the self-position of the probe head 12.

[0055] The self-position estimation unit 62 stores information indicating the position and posture of the probe head 12 obtained as described above (probe head self-position information) in the storage unit 54. 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.

[0056] Next, it is determined whether or not to repeat 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 or not to continue the self-position estimation process of the probe head 12 (YES in step S16), and repeats the processes from step S10 to step S16. As a result, while the probe head 12 is measuring the three-dimensional coordinates of the workpiece, the self-position estimation process of the probe head 12 is continuously and repeatedly performed.

[0057] 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 whether the self-position estimation process of the probe head 12 is completed (NO in step S16), and ends this flowchart.

[0058] [Probe head calibration method] Next, a method for calibrating the probe head 12 will be described.

[0059] Figure 5 is a diagram modeling the positional relationship between the probe head 12, the stylus ball 32, and the calibration ball 34. The stylus ball 32 is the tip ball of the stylus 30 attached to the probe 18 (see Figure 2) provided in the probe head 12. In Figure 5, the radius of the calibration ball 34 is r sp The radius of the stylus ball 32 is r stylus Let's say.

[0060] As shown in FIG. 5, when measurement (probing) is performed by bringing the stylus ball 32 into contact with the surface of the calibration ball 34, the following equation holds true:

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[0061] In addition, in equation (8), x stylus、t is the world coordinate system Σ w is a vector (position vector) that indicates the position of the center point of the stylus ball 32 at sp is the world coordinate system Σ wis a vector (position vector) indicating the position of the center point of the calibration sphere 34 in the image. Note that the subscript t indicates that the parameter depends on a certain time or scene (i.e., the position and attitude of the probe head 12) (the same applies hereinafter).

[0062] Here, the probe head coordinate system (coordinate system based on the probe head 12) Σ h From the world coordinate system Σ w The coordinate transformation matrix to T t Coordinate transformation matrix T t is the rotation matrix R T,t and the translation vector t T,t is defined by T t =[R T,t |t T,t ]. Also, the probe head coordinate system Σ h If the vector indicating the position of the center point of the stylus ball 32 at is represented by s, the following equation (9) holds.

[0063]

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[0064] Next, by substituting equation (9) into equation (8), the following equation (10) is obtained.

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[0065] Here, assuming that the self-position estimation process described above (i.e., the process of estimating the self-position (position and attitude) of the probe head 12 based on the target images of the target group 14 captured by the camera 20 of the probe head 12) is being performed continuously while the calibration process of the probe head 12 is being performed, the world coordinate system Σ w and the probe head coordinate system Σ h The relative positional relationship between the probe head coordinate system Σ h From the world coordinate system Σ w Coordinate transformation matrix T to tis known, and its component, the rotation matrix R T,t and translation vector t T,t Also, since the calibration sphere 34 is a true sphere with a known radius, its radius r sp is also known.

[0066] On the other hand, the probe head coordinate system Σ h A vector s indicating the position of the center point of the stylus ball 32 in the stylus and the world coordinate system Σ w Vector x indicating the position of the center point of the calibration sphere 34 in sp It is unknown.

[0067] These unknown parameters (s, r stylus , x sp ) can be found by optimization calculation. Various nonlinear solution methods such as the Newton-Raphson method and the nonlinear conjugate gradient method can be used for the optimization calculation, but since these are generally well-known methods, their explanation will be omitted here.

[0068] In this embodiment, the above-described calculation algorithm is used to perform calibration processing of the probe head 12. Specifically, scanning measurement is performed in which the stylus ball 32 is moved along a path (calibration path) on the surface of the calibration sphere 34 while the stylus ball 32 is in contact with the surface of the calibration sphere 34. Furthermore, while this scanning measurement is being performed, self-position estimation processing of the probe head 12 is continuously performed.

[0069] The calibration path during scanning measurement should be a three-dimensional path on the surface of the calibration sphere 34. For example, a spiral path on the surface of the calibration sphere 34 is preferably used. Alternatively, it may be a combination of multiple planar paths with different diameters or directions, or a random path. As will be described later, the radius r of the stylus ball 32 is stylus is known, the path on the surface of the calibration sphere 34 does not necessarily have to be a three-dimensional path.

[0070] In this way, by simultaneously performing scanning measurement and self-position estimation in parallel, the position and orientation of the probe head 12 can be obtained at each position of the stylus ball 32 that has moved along the path on the surface of the calibration sphere 34. That is, with the distance between the center point of the stylus ball 32 and the center point of the calibration sphere 34 kept constant, the world coordinate system Σ w The self-positions of the probe heads 12 (i.e., the probe rotation matrix R T,t and translation vector t T,t ) can be obtained multiple times.

[0071] In addition, when scanning measurement is performed, the movement locus of the center point of the stylus ball 32 is determined by the radius r of the stylus ball 32 from the path on the surface of the calibration ball 34. stylus The movement trajectory is offset by this amount.

[0072] Using the self-position of the probe head 12 thus obtained, the calibration parameters (s, r stylus , x sp ) is found.

[0073] The radius r of the stylus ball 32 stylus is known, the calibration path during scanning measurement may be a planar path on the surface of the calibration sphere 34. However, if the radius r of the stylus ball 32 is stylus Even when is known, the calibration path during scanning measurement may of course be a three-dimensional path.

[0074] Next, a method for calibrating the probe head 12 in this embodiment (one example of the calibration method of the present invention) will be described.

[0075] First, scanning measurement is performed on the calibration sphere 34 using the probe head 12 (step S20). In scanning measurement, the stylus ball 32 of the stylus 30 provided in the probe head 12 is brought into contact with the surface of the calibration sphere 34, and the stylus ball 32 is moved along a path (calibration path) on the surface of the calibration sphere 34. As described above, a three-dimensional path such as a spiral path on the surface of the calibration sphere 34 is preferably used as the calibration path during scanning measurement.

[0076] Furthermore, while the scanning measurement is being performed, a self-position estimation process for the probe head 12 is performed (step S22). The self-position estimation process is as described above, and the self-position estimation unit 62 estimates the self-position (position and orientation) of the camera 20 based on target images of the target group 14 captured by the camera 20 mounted on the probe head 12. This allows the position and orientation of the probe head 12 to be determined at each position to which the stylus ball 32 moves during the scanning measurement. The processing in the self-position estimation unit 62 has been described above, so a description thereof will be omitted here.

[0077] Next, the calibration processing unit 70 calculates the calibration parameters (s, r) by solving the above-mentioned equation (10) through optimization calculation based on the self-position data indicating the position and attitude of the probe head 12 obtained during the scanning measurement. stylus , x sp ) is calculated (step S24).

[0078] Next, the calibration processing unit 70 outputs the calibration parameters to an output unit (not shown) (step S26). The calibration processing unit 70 also stores the obtained calibration parameters in the storage unit 54. As a result, when the three-dimensional coordinates of the workpiece are calculated using the probe head 12, the calculation of the three-dimensional coordinates is performed in a state where calibration has been performed using the calibration parameters stored in the storage unit 54.

[0079] This completes the flowchart shown in FIG.

[0080] 〔effect〕 Next, the effects of this embodiment will be described.

[0081] According to this embodiment, by performing a scanning measurement of the calibration sphere 34 using the probe head 12 while performing a self-position estimation process to detect the position and attitude of the probe head 12, it is possible to easily determine the relative positional relationship between the probe head 12 and the stylus sphere 32 using the results.

[0082] Furthermore, according to this embodiment, by making the path on the surface of the calibration sphere 34 a three-dimensional path during scanning measurement, it is possible to determine the radius of the stylus ball 32 along with the above-mentioned relative positional relationship.

[0083] Furthermore, according to this embodiment, if the radius of the stylus ball 32 is known, the calibration path during scanning measurement can be set to a planar path on the surface of the calibration ball 34, making it possible to calibrate the probe head 12 more easily.

[0084] The probe head 12 is not limited to one that is held by a user to measure a workpiece. For example, the probe head 12 may be attached to the tip (end effector) of an articulated robot arm, and the probe head 12 may be moved by controlling the operation of the robot arm, thereby measuring the three-dimensional coordinates of the workpiece.

[0085] Furthermore, in the present embodiment, the case where the target group 14 is configured with a dot pattern in which a plurality of targets 24 formed in a dot or point shape are arranged two-dimensionally has been shown as an example, but the present invention is not limited to this, and the target group 14 may be configured with, for example, a grid pattern or a checkered pattern as disclosed in the above-mentioned Patent Document 2. Furthermore, the target group 14 may be various two-dimensional patterns including an AR marker (Augmented Reality Marker) or a QR code (Quick Response code, registered trademark), etc.

[0086] Although the embodiments of the present invention have been described above, the present invention is not limited to the above examples, and various improvements and modifications may be made without departing from the spirit of the present invention. [Explanation of symbols]

[0087] 10...self-position estimation system, 12...probe head, 14...target group, 18...probe, 20...camera, 24...target, 30...stylus, 32...stylus ball, 34...calibration ball, 50...self-position estimation device, 52...arithmetic processing unit, 54...memory unit, 60...image acquisition unit, 62...self-position estimation unit, 64...determination processing unit, 66...feature point detection unit, 68...optimization calculation unit, 70...calibration processing unit

Claims

1. a moving step of moving the stylus ball of the probe head along a path on the surface of the calibration sphere while the stylus ball is in contact with the surface of the calibration sphere; a self-position estimation step of detecting the position and attitude of the probe head based on images of a group of targets captured by a camera mounted on the probe head while the moving step is being performed; a calibration step of determining a relative positional relationship between the probe head and the stylus ball based on the detection result of the self-position estimation step; Calibration methods including:

2. the path is a three-dimensional path along the surface of the calibration sphere; The calibration method according to claim 1 .

3. the calibration step includes determining the radius of the stylus ball together with the relative positional relationship; The calibration method according to claim 2 .

4. the path is a planar path along the surface of the calibration sphere; The calibration method according to claim 1 .

5. an image acquisition unit that acquires images of the target group taken 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; a calibration processing unit that determines the relative positional relationship between the probe head and the stylus ball based on the results of detection of the position and attitude of the probe head by the self-position estimating unit while a scanning measurement is being performed in which the stylus ball of the probe head is moved along a path on the surface of a calibration ball; A calibration device comprising:

Images