JP2014079474A - Golf club head, swing analysis system using the same, and swing measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf club head able to be arranged with a marker at a predetermined position, and to provide a swing analysis system and a swing measuring method which use the golf club head.SOLUTION: A golf club head, at least one of a position and an attitude of which is calculated on the basis of its image captured by using one camera, includes: two or more markers having reflection surfaces for reflecting light so that their images are captured by the camera; and a golf club head body having two or more attachment parts each with a same planar shape or a similarity shape as that of each marker, the attachment parts being attached with the markers, respectively. Here, a difference in area between the attachment part and the marker is 20 mmor less.

Description

  The present invention relates to a golf club head, a swing analysis system using the same, and a swing measurement method.

  In recent years, various methods for analyzing the swing of a golf club have been developed. For example, a method has been proposed in which a marker having a reflective surface that reflects light is fixed to a golf club head and the resulting image is captured by a camera. In this method, the posture of the golf club head and the like are calculated based on the imaged marker.

  As the marker, for example, a reflective tape is employed, and is attached to a plurality of locations (for example, 3 locations or more) of the golf club head. The specific position (for example, centroid) of the attached reflective tape is stored in the computer as known coordinate information.

  A computer is used to calculate the posture of the head. The computer calculates the posture of the head based on the position of the marker imaged by the camera and the known information. For this calculation, for example, a DLT (Direct Linear Transformation) method is preferably used. Calculating the posture of the golf club head during a swing is useful for club development or for teaching a swing. Related technologies include the following.

JP 2004-24488 A JP 2007-167549 A JP 2004-61483 A

  By the way, when the posture of the head is calculated, the outline of each marker is extracted from the captured image, and a specific position of each marker, for example, the centroid is calculated. The centroid of the marker must be accurately identified because it is the basis for subsequent calculations.

  In particular, when shooting a marker with a single camera, the posture cannot be accurately calculated unless the position of the marker relative to the head is accurately specified. Therefore, the marker is attached at a predetermined position. However, since such a marker is detachably attached to a golf club head and is often re-applied many times due to wear or the like, there is a problem that the marker is likely to be displaced from a predetermined position. there were. For this reason, errors often occur in the calculation of the posture, and improvements have been demanded.

  The present invention has been made to solve the above problems, and provides a golf club head capable of accurately arranging a marker at a predetermined position, a swing analysis system using the golf club head, and a swing measurement method. The purpose is to do.

The present invention is a golf club head in which at least one of a position and a posture is calculated based on photographing by one camera, and a plurality of markers having a reflecting surface that reflects light so as to be photographed by the camera. And a golf club head body having a plurality of attachment portions to which the respective markers are attached, and a difference between the area of the attachment portion and the area of the marker is 20 mm ² or less.

  In the golf club head, the attachment portion may be constituted by a bottom surface of a recess formed on the surface of the golf club head main body, and the marker may be disposed on the bottom surface.

  In the golf club head, the relationship between the depth X of the recess and the thickness Y of the marker can be Y> X−0.4 mm.

  In the golf club head, the attachment portion may be constituted by a region surrounded by an annular groove formed on the surface of the golf club head main body.

  A golf club swing analysis system according to the present invention includes a golf club having any of the above-described golf club heads, a camera capable of capturing the head image by capturing the golf club head, and capturing the head image. And a calculation device for calculating at least one of the position and orientation of the head based on the marker.

The golf club head swing measuring method according to the present invention includes a step of preparing a plurality of markers having a reflecting surface that reflects light, and a step of preparing a golf club head body having a plurality of attachment portions to which the markers are attached. And attaching each marker to each attachment portion of the golf club head main body to form a golf club head, and photographing the golf club head with one camera, and based on the photographed marker Calculating at least one of the position and posture of the golf club head, and the difference between the area of the mounting portion and the area of the marker is 20 mm ² or less.

  According to the present invention, the marker can be accurately arranged at a predetermined position.

It is a whole block diagram of the analysis system which performs the measuring method of a golf club head. It is a front view of FIG. It is a front view of a wood type golf club head. It is a top view of a wood type golf club head. It is a diagram which shows the relationship between the coordinate in real space, and the coordinate on the film surface of a camera. It is the front view explaining the example of the attachment part in an iron type golf club head, and a partial sectional view. It is the front view and other part sectional view explaining other examples of the attaching part in an iron type golf club head.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a golf club head according to the present invention, a swing analysis system using the same, and a swing measurement method will be described with reference to the drawings.

  The present embodiment relates to an analysis method for calculating the position and orientation of a golf club head in order to analyze the swing of the golf club, and to the golf club head used therefor. This analysis method includes a step of imaging a golf club head to which a marker having a reflecting surface that reflects light is fixed with a camera (an imaging step), and a step of detecting the posture of the golf club head based on the captured marker ( Calculation step). First, the imaging process and the calculation process will be briefly described.

<1. Schematic configuration of analysis system>
FIG. 1 shows an example of an overall configuration diagram of an analysis system 10 used in the imaging process, and FIG. 2 shows a front view thereof. In the analysis system 10, a club head (hereinafter, simply referred to as “head”) 2 of the golf club 1 is imaged. The head 2 of the golf club 1 does not move by itself, but moves by the swing of the golfer M.

  In the embodiment of FIG. 1, a right-handed golfer M is shown. With the swing of the golfer M, the golf ball 3 is launched to the left of the golfer M in the address posture of FIG. However, the golfer M may be substituted with a swing robot or the like.

  The analysis system 10 includes, for example, a base 12, a first camera 14 for photographing the head 2 of the golf club 1, a second camera 16 for photographing the golf ball 3, and a control device that controls the cameras 14 and 16. 18 and an information processing device (calculation device) 20 that records information captured by the cameras 14 and 16. Specifically, the control device 18 is connected to the first camera 14 and the second camera 16 described above, various sensors 26, 27, and 28, strobes 25 and 29, and an information processing device 20 described later.

  The base 12 has a plate shape, and is placed, for example, on the floor surface of the measurement room. On the base 12 of this embodiment, a floor board 21 on which the golfer M stands and addresses is placed. A tee 23 for placing the golf ball 3 is provided on the floor plate 21.

  The base 12 is provided with a support column 24 extending upward. A strobe 25 that emits light toward the head 2 of the golf club 1 is provided at the top of the support 24.

  For convenience of explanation, as shown in FIGS. 1 and 2, orthogonal coordinates having an X axis, a Y axis, and a Z axis are defined in the analysis system 10. The X axis is parallel to the ground and parallel to a straight line connecting the ball 3 before hitting the ball and the target direction. The Z axis is the vertical direction. The Y axis is both perpendicular to the X axis and Z.

  A trigger sensor 26 is provided on the base 12. The trigger sensor 26 is a combination of a projector 26a provided on the front (abdominal side) of the swinging golfer M and a light receiver 26b provided on the rear (back side) of the golfer M and receiving the light of the projector 26a. . The trigger sensor 26 is aligned so that the light emitted from the light projector 26a in the Y-axis direction is blocked by the passage of the golf club 1 during the downswing.

  The base 12 is further provided with a first sensor 27. The first sensor 27 includes a projector 27a provided in front of the swinging golfer M, and a light receiver 27b provided in the rear of the golfer M and receiving the light of the projector 27a. The first sensor 27 is provided in front of the swing (the flying direction of the hit golf ball 3) in the X-axis direction than the trigger sensor 26. Accordingly, during the downswing, the first sensor 27 detects the golf club 1 that is swinging slightly behind the trigger sensor 26.

  A second sensor 28 is further provided on the base 12. The second sensor 28 also includes a light projector 28a provided in front of the swinging golfer M and a light receiver 28b provided in the rear of the golfer M and receiving the light from the light projector 28a. The second sensor 28 is provided in front of the swing in the X-axis direction with respect to the first sensor 27. Therefore, the second sensor 28 detects the golf club 1 during the swing slightly later than the first sensor 27 during the downswing.

  The first camera 14 is provided above the golfer M so that a crown portion that is the upper surface portion of the head 2 of the golf club 1 can be photographed.

  The second camera 16 is provided in front of the golfer M from the tee 23 and in front of the swing in the X-axis direction so that the shot golf ball 3 can be photographed from the side. A strobe 29 is provided around the second camera 16.

  The information processing apparatus 20 includes a monitor as an output unit, an interface board as a data input unit, a memory, a CPU, and a hard disk. The information processing apparatus may include a keyboard and a mouse. A general-purpose computer may be used as it is as the information processing apparatus.

  The hard disk stores programs. The memory is rewritable, and constitutes a storage area and a work area for programs called from the hard disk and various data. The CPU can read a program stored in the hard disk. The CPU can expand the program in the work area of the memory. The CPU can execute various processes according to the program. For example, this program can calculate the position and orientation of the head based on the head image.

  Head image data can be input to the interface board. Head image data, ball image data, and synchronization data of the two image data may be input. These human data are output to the CPU. The CPU performs various processes. By this processing, the posture and position of the head 2 can be calculated. Further, a club behavior value and a ball behavior value may be calculated. Of these calculated values, a predetermined data is output to the monitor. In addition, predetermined data is stored in the hard disk.

<2. Club Head Overview>
Here, only the outline of the club head 2 used in the analysis system 10 will be described, and a detailed description will be given later. FIG. 3 is a front view of the club head 2, and FIG. 4 is a plan view thereof. The head 2 includes a face 2a which is a surface for hitting a ball, and a crown portion 2b which is connected to the face 2a and forms a head upper surface portion.

  The club head 2 is provided with a marker 30. The marker 30 has a reflective surface that reflects light, and can be formed of, for example, a white or silver reflective tape. The head 2 is provided with a plurality of attachment portions for attaching the marker 30, and a marker is attached to each attachment portion. At this time, the club head 2 is preferably provided with three or more markers 30 in one photographing frame. The marker 30 can be provided at a position other than the face 3a. In this embodiment, four markers 30 a to 30 d are provided on the crown portion 2 b of the head 2.

<3. Swing measurement by control device (imaging process)>
The operation of the control device 18 is as follows. When the golf swing is started by the golfer M, the control device 18 receives a detection signal indicating that the trigger sensor 26 has detected the golf club 1 during the downswing. Based on this detection signal, the control device 18 outputs a shooting start signal that causes the first camera 14 and the second camera 16 to start shooting.

  Based on this imaging start signal, the shutter of the first camera 14 is opened for a predetermined time (for example, 1/30 second). While the shutter is open, a detection signal indicating that the first sensor 27 and the second sensor 28 have detected the head 2 or the shaft of the golf club 1 is sequentially input to the control device 18. The control device 18 outputs a signal for causing the strobe 25 to emit light based on the detection signal from the first sensor 27. Thereafter, the control device 18 outputs a signal for causing the strobe 29 to emit light based on the detection signal from the second sensor 28.

  Therefore, the strobe 25 and the strobe 29 emit light sequentially while the shutter is open. As a result, the first camera 14 can capture one piece of image data including the club head 2 detected by the first sensor 27 and the club head 2 detected by the first sensor 28. . Therefore, in this embodiment, the club head 2 is photographed by one camera. Further, the second camera 29 photographs the hit ball 3.

<4. Calculation of position and orientation of golf club head by information processing device (calculation process)>
Image data captured by the first camera 14 and the second camera 16 is output to the information processing apparatus 20. By analyzing this data, the information providing apparatus 20 calculates at least one of the posture and position of the club head 2 by executing the above-described program. Examples of data in the vicinity of the impact that can be calculated (hereinafter also referred to as impact data) are given below.

[Example of impact data]
・ Head position relative to the ball ・ Fitting point on the face surface ・ Lie angle ・ Loft angle ・ Face angle ・ Head track (blow angle, approach angle, etc.)
The calculation process includes, for example, the following steps a to d.

(A) Identify each marker 30 from the obtained image of the head 2 (b) Calculate the three-dimensional position of each marker 30 (c) Calculate the position, posture, etc. of the head 2 based on the three-dimensional position (d) However, prior to these steps, calibration for obtaining camera constants described later is performed. This point will be described later. Hereinafter, each step will be described.
[Step a]
Step a is performed manually or automatically. When step a is performed manually, the user discriminates the marker 30 from the image with the naked eye, and inputs the position information and the like of the marker 30 to the information processing apparatus 20. When step a is automatically performed, the information processing apparatus 20 generally performs a known edge extraction process or the like using luminance information or the like for each pixel of the image. Thereby, the marker 30 is extracted from the image.
[Step b]
In step b, the three-dimensional coordinates of each marker 30 are calculated. As an example of this calculation method, the DLT method described above is known. The DLT method is a method for obtaining three-dimensional spatial coordinates of a specific position using a plurality of images viewed from different directions. In the DLT method, three-dimensional coordinates are reconstructed based on an image of a point (control point) whose three-dimensional coordinates are known.

  FIG. 5 shows coordinates (X, Y, Z) in the real space and coordinates (U) on the film plane of the camera (U) when a point P in the real space (Object space) is photographed by the camera. , V). Point O is the center point of the lens of the camera. The coordinate system X′Y′Z ′ is a coordinate system in which the point O is the origin and the on-film coordinate system UV is parallel to the X ′ axis and the Y ′ axis. The distance L is a distance on the Z ′ axis from the point O to the point P. The distance F is a distance on the Z ′ axis from the point O to the point Q (mapping point P). Point (U, V) is an intersection of a straight line including the Z ′ axis and the film surface. In this case, the following explanation and formula (F1) are established.

  In order to obtain the eleven camera constants of the above formula (F1), first, six or more points with known real space coordinates (X, Y, Z) and film surface coordinates (U, V) are photographed by the camera. The Next, (X, Y, Z) and (U, V) of each point are substituted into the formula (F1), and a total of 12 or more equations are set. Then, eleven camera constants are obtained by solving these equations by the method of least squares (calibration). If eleven camera constants are obtained, the coordinates (U, V) on the film plane can be obtained for points whose real space coordinates (X, Y, Z) are known.

  On the other hand, in order to obtain the real space coordinates (X, Y, Z) from the coordinates (U, V) on the film plane, the same point is obtained by using two or more cameras with known camera constants. By substituting (U1, V1), (U2, V2)... Into the above equation, four or more equations are set, and (X, Y, Z) is obtained by the least square method.

In the above method, two cameras are required to obtain the coordinates of one independent point in the space, and the coordinates of the point cannot be obtained from one camera image. However, with respect to the coordinates of a plurality of points fixed to an object having a size, if the positional relationship between the points (that is, the coordinates of each point in the object coordinate system) is known, the relational expression is the spatial coordinate (X , Y, Z) is added to the equation for obtaining the coordinates, so that the coordinates of a plurality of points can be obtained. That is, even with a single camera image, the coordinates of one independent point in space can be obtained.
[Step c]
The coordinates of each marker 30 in the object coordinate system (the coordinate system of the club head 2) can be obtained, for example, by measuring a three-dimensional shape of the object. Hereinafter, a case where the spatial coordinates (X, Y, Z) of the representative point of the object and the posture (α, β, γ) of the object are solved as unknowns will be described.

  In the above formula (F3), Ri (x) represents the x component of Ri, Ri (y) represents the y component of Ri, and Ri (z) represents the z component of Ri.

  The simultaneous equations (F3) having six unknowns and 2n equations can be solved by the Newton-Raphson method (solution of nonlinear simultaneous equations). Thereby, six unknowns, that is, the position of the object representative point and the posture of the object can be obtained. Note that α, β, and γ indicate coordinate conversion angles from the space coordinate system to the object coordinate system. In the present embodiment, the coordinate system Cs1 is obtained by rotating the spatial coordinate system XYZ about the Z axis by α °, and the coordinate system Cs2 is obtained by rotating the coordinate system Cs1 by β ° about the Y axis. When the coordinate system Cs3 is rotated by γ ° around the X axis to obtain the coordinate system Cs3, the coordinate system Cs3 coincides with the object coordinate system.

  The 2n simultaneous equations described above are defined as an equation (F3). A method for solving the equation (F3) by the Newton-Raphson method is as follows.

  The above method is an example of a so-called gradient method. This gradient method is simpler in calculation than, for example, the genetic algorithm used in Patent Document 3 above. In this way, based on the relative relationship between points whose coordinates in the object coordinate system are known, from one head image, the spatial coordinates of the representative point of the head and the three-dimensional posture (for example, face angle, lie angle, etc.) ) Can be calculated. Then, the calculation result is output.

  By the way, in the method described above, the marker 30 serves as a reference for calculation, and therefore the position of the marker 30 on the head 2 must be accurately specified. In particular, as described above, when the marker 30 is made of a reflective tape or the like, it is easy to wear out, so that the marker 30 may be frequently removed. Therefore, if the position of the marker is shifted every time it is removed, the calculation cannot be performed accurately. Therefore, in this embodiment, in order to uniquely determine the position of the marker 30, an attachment portion is provided on the head 2, and the marker 30 is attached to this attachment portion. Hereinafter, the mounting portion in the head 2 and the marker 30 will be described in more detail. In the present invention, the head is configured by attaching the marker to the head main body, but here, the portion corresponding to the head main body may be simply referred to as the head.

<5. Head mounting portion and marker mode 1>
FIG. 6 is a plan view and a partial cross-sectional view of the head 2 of the iron type golf club according to the first aspect. As shown in these drawings, a circular recess 201 is formed on the surface of the head 2, and the marker 30 is attached to the bottom surface of the recess 201. The bottom surface of the recess 201 constitutes an attachment portion to which the marker 30 is attached. The marker 30 is formed in a circular shape like the concave portion 201, and is adhered to the bottom surface of the concave portion 201 with the bottom surface serving as an adhesive surface. At this time, the method for adhering the marker 30 and the bottom surface of the recess 201 is not particularly limited. It can also be attached.

  The marker 30 needs to have a smaller diameter than the recess 201 so that the marker 30 can be securely fitted into the recess 201. If it is too small, it will be difficult to identify it as a marker on the image. On the other hand, if it is too large, the appearance will be impaired and the swing will be hindered. Accordingly, the diameter D1 of the marker 30 is preferably, for example, 3 to 15 mm, and more preferably 5 to 10 mm.

As described above, the position of the marker 30 in the head 2 should be at the same position no matter how many times the marker 30 is re-applied in order to perform an accurate calculation. Therefore, when the concave portion 201 is formed in the head 2 and the marker 30 is attached to the concave portion 201, the position of the marker 30 is always constant, and the marker 30 can be prevented from being displaced. Moreover, since the marker 30 should just be fitted in the recessed part 201, there also exists an advantage that it is easy to position. However, if the position of the marker 30 in the recess 201 changes, it affects the calculation. Therefore, the difference between the area of the bottom surface of the recess 201 and the area of the adhesion surface (bottom surface) of the marker 30 needs to be as small as possible. is there. As a result of the study, the inventors of the present application have found that the difference between the area of the bottom surface of the recess 201 and the area of the adhesion surface of the marker 30 is preferably 20 mm ² or less, and more preferably 10 mm ² or less. . This point will be described in more detail. The inventor of the present application has found that correct measurement cannot be performed unless the error between the original marker position and the actual marker position is 0.4 mm or less. In order to reduce this error to 0.4 mm or less, it is necessary to reduce the pasting error that occurs when the marker is pasted. To that end, the area of the bottom surface of the recess 201 and the marker 30 It has been found that the difference from the area of the adhesive surface is set as small as possible, as described above. In terms of diameter, the difference between the diameter D2 of the bottom surface of the recess 201 and the diameter D1 of the marker is preferably within 1.84 mm, and more preferably 0.98 mm or less.

  Further, the depth of the recess 201 is not particularly limited, but can be determined in relation to the thickness of the marker 30. That is, in order to reliably image the marker 30 in the above-described imaging process, it is necessary to prevent the imaging of the marker 30 from being hindered by the inner wall surface of the recess 201. Therefore, in consideration of the above-described error, it is preferable that the marker thickness Y> the recess depth X−0.4 mm.

  The method for creating the recess 201 is not particularly limited, and can be performed by various methods. For example, in the case of an iron type golf club as shown in FIG. 6, the recess can be formed by machining. Moreover, although the said description is an iron type golf club, the same recessed part can be formed also in a wood type golf club. In this case, the concave portion can be formed by machining, but can be formed by casting in which the concave portion is formed in advance. The casting method is not particularly limited, and for example, a lost wax method or the like can be applied.

<6. Head mounting part and marker mode 2>
FIG. 7 is a perspective view of the head 2 of the iron type golf club according to aspect 2, and FIG. 7 is a cross-sectional view of the surface thereof. As shown in these drawings, an annular groove 202 is formed on the surface of the head 2, and the marker 30 is attached to a circular region 203 surrounded by the groove 202. The diameter D3 of the circular region 203 is the same as the diameter of the bottom surface of the recess 201, and this circular region 203 constitutes an attachment portion to which the marker 30 is attached. The method for forming the groove 202 is not particularly limited, but can be formed by the same method as that for the recess 201. Further, the depth of the groove 202 is not particularly limited because it does not affect the marker 30. The configuration of the marker 30 used here is also as described above.

In this aspect, the user can visually recognize the circular region 203 surrounded by the groove portion 202 to perform positioning when attaching the marker 30, and in order to make the attachment position of the marker 30 constant, the area of the circular region 203 is The difference in the area of the adhesion surface (bottom surface) of the marker 30 should be as small as possible. That is, similarly to the aspect 1, the difference between the area of the bottom surface of the circular region 203 and the area of the adhesion surface of the marker is preferably 20 mm ² or less, and more preferably 10 mm ² or less.

<7. Features>
As described above, according to this embodiment, the attachment portions 201 and 203 to which the marker 30 is attached to the golf club head 2 are provided. The user attaches the marker 30 so that the attachment portions 201 and 203 and the marker 30 are aligned while visually recognizing the attachment portions 201 and 203. Therefore, the difference between the area of the attachment portions 201 and 203 and the area of the marker 30 is determined. If is small, it is possible to prevent the marker 30 from shifting. In particular, in the analysis system in which at least one of the position and posture of the golf club head 2 is calculated based on the shooting by one camera as described above, the deviation of the marker 30 has a great influence on the analysis. From this point of view, the difference between the area of the attachment portions 201 and 203 and the area of the marker is 20 mm ² or less.

<8. Modification>
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, although the marker and the attachment portion are formed in a circular shape in plan view, they can be formed in a rectangular shape or a polygonal shape. Further, the planar shape of the marker and the planar shape of the attachment portion may be the same or similar, but are not strict, and the planar shape is not particularly limited as long as the marker is attached to the attachment portion.

  Further, in addition to forming the concave portion 201 and the circular region 203, for example, the surface of the head 2 can be subjected to blasting, and this processing region can be used as an attachment portion. When such blasting is performed, the attachment portion can be visually recognized as compared with other regions on the head 2, and further, the displacement of the marker 30 can be reduced by making the area of this processing region the same as that of the concave portion described above. Can be prevented. In addition, the configuration is not particularly limited as long as the attachment portion can be visually recognized from other regions. For example, the attachment portion can be formed by coloring.

  Further, the number and position of the attachment portions are not particularly limited, and the number of attachment portions is preferably 3 or more. In addition to the face of the club, the position of the mounting portion may be any position that can be photographed with a camera, and it is preferable to avoid a position where the golfer can get in the way and cannot be photographed with the camera.

  Examples of the present invention will be described below. However, the present invention is not limited to the following examples. Here, in order to confirm the effect of the present invention, a marker was attached to the head of an iron type golf club as shown in FIG. That is, it was examined whether or not the head to which the marker was attached could withstand the calculation of the position and orientation of the head. The examination procedure is as follows.

  First, 11 golf clubs having the following iron type golf club heads were prepared (Examples 1 to 6 and Comparative Examples 1 to 3). Each club head was provided with four attachment portions for attaching the markers, as shown in FIGS. The markers attached to the heads of the clubs were all the same, and were formed of a circular tape in plan view. More specifically, a silver reflective surface was formed on the surface, and a double-sided tape was attached to the bottom surface as an adhesive surface. The marker has a diameter of 6.0 mm and a thickness of 0.4 mm. On the other hand, the attachment part of each club was formed as follows.

  In addition, the depth of each recessed part was 0.4 mm. That is, since it is the same as the thickness of the marker, the surface of the marker substantially coincides with the face surface of the club.

  Next, five test subjects were asked to affix a marker on the mounting portion of each head. Thereafter, the head to which the marker was attached was measured three-dimensionally to determine the center coordinate of the marker, and the absolute value of the error (distance) from a predetermined position coordinate, that is, the center coordinate of the mounting portion was calculated. The results are as follows. Below, the average of the error by five test subjects is shown.

Here, considering the determination, in the analysis system described above, the measurement accuracy differs depending on the number of pixels of the camera that performs imaging, but accurate measurement is possible when the imaging range per pixel exceeds about 0.4 mm × 0.4 mm. Can not. From this point of view, it was determined that accurate measurement could not be performed if a deviation greater than 0.4 mm occurred from the position where the marker was originally attached. Therefore, in the above determination, it was determined that accurate measurement can be performed with an error of 0.4 mm or less as A determination. On the other hand, when the error was larger than 0.4 mm, the determination was B, and it was determined that accurate measurement could not be performed. Therefore, as shown in the Examples, it was found that if the difference between the area of the attachment portion and the area of the marker is greater than 20 mm ² , the user cannot accurately position the marker.

DESCRIPTION OF SYMBOLS 1 Golf club 2 Head 2B Crown part 20 Information processing apparatus (calculation apparatus)
30 markers

Claims (6)

A golf club head in which at least one of a position and a posture is calculated based on shooting by one camera,
A plurality of markers having reflective surfaces for reflecting light, as photographed by the camera;
A golf club head body having a plurality of attachment portions to which the respective markers are attached;
With
A golf club head, wherein a difference between an area of the attachment portion and an area of the marker is 20 mm ² or less.   The golf club head according to claim 1, wherein the attachment portion is configured by a bottom surface of a recess formed on a surface of the golf club head main body, and the marker is disposed on the bottom surface.   The golf club head according to claim 2, wherein a relationship between the depth X of the concave portion and the thickness Y of the marker is Y> X−0.4 mm.   The golf club head according to claim 1, wherein the attachment portion is configured by a region surrounded by an annular groove formed on a surface of the golf club head main body. A golf club having the golf club head according to claim 1;
A camera capable of photographing the golf club head and acquiring a head image;
A golf club swing analysis system comprising: a calculation device that calculates at least one of a position and a posture of the head based on a marker photographed in the head image. Providing a plurality of markers having a reflective surface for reflecting light;
Preparing a golf club head body having a plurality of attachment portions to which the respective markers are attached;
Attaching each marker to each attachment portion of the golf club head body to form a golf club head;
Photographing the golf club head with one camera, and calculating at least one of the position and posture of the golf club head based on the photographed marker;
With
A method for measuring a swing of a golf club head, wherein a difference between an area of the attachment portion and an area of the marker is 20 mm ² or less.