Golf club head measurement system

1. A system for measuring a golf club head during an impact with a golf ball, the club head having a club face with at least one score line, wherein the club face is substantially planar, the system comprising:

at least three markers placed on the club face, the marker placement adapted to (1) define the geometry of the club face, and (2) conform to a known tolerance of relative spacing and orientation between the markers, wherein at least two of the markers define a HEEL-TOE line that is parallel to the score line and at least one marker is not placed in alignment with the HEEL-TOE line;

at least two cameras positioned ahead of the golf ball and adapted to capture a plurality of images prior to and at impact of the markers during a swing and communicating those images to a processor;

the processor configured to perform the following steps;

a. performing threshold processing on the images to detect pixels that may correspond to the markers;

b. determining a position for the markers in three dimensional space;

c. finding a group of markers that fall within the tolerance of a known geometric relationship based on the planarity of club face and the known orientation of the at least two markers along the HEEL-TOE line and the at least one marker not placed in alignment with the HEEL-TOE line;

d. labeling the markers based on their position with respect to the known geometric relationship; and

e. calculating the position of the club head during the swing based on the 3D position of the markers.

2. The system of claim 1 , further comprising:

at least four markers placed on the club face, wherein the four markers are placed at the TOE TOP, TOE, TOE BOTTOM and HEEL positions of the club face and wherein D 1 is defined as a line connecting the HEEL and TOE markers, D 2 is a line connecting the TOE TOP and TOE markers, and D 3 is a line connecting the TOE BOTTOM to TOE markers; and

wherein known tolerance of relative spacing and orientation between the markers comprises:

i. D 1 has and minimum and maximum known lengths for standard golf clubs;

ii. D 1 is always longer than D 2 and D 3 ;

iii. D 1 is substantially closer to horizontal relative to the ground than vertical at impact with a golf ball;

iv. the TOE TOP marker is above D 1 at impact;

v. the TOE BOTTOM marker is below D 1 at impact; and

vi. all markers lie substantially in the same plane.

3. The system of claim 1 , wherein the processor performs the following additional steps:

f. identifying groups of neighboring pixels found in step ( a ); and

g. performing a centroid algorithm on pixels groups detected in step ( f ); and

h. stereoscopically matching the centroids detected in step ( g ).

4. The system of claim 1 , wherein the processor performs the following additional step of determining the position of the golf ball in three dimensional space before impact.

5. The system of claim 4 , the system further comprising an alerting structure connected to the processor, wherein the alerting structure produces an alert when the processor determines the position of the golf ball.

6. The system of claim 4 , wherein the processor performs the following additional step of determining the point on the club face where the club face first contacts the ball.

7. The system of claim 1 , wherein a plurality of club heads having club faces are marked, the processor performs the following additional steps of:

f. measuring and storing a list of the precise geometric layout of the markers on each of the plurality of golf club heads;

g. locating the geometric layout from the plurality of images for the club head that is being swung; and

h. identifying which golf club head in the plurality is being swung based on a match of the located geometric layout of step (g) to the stored geometric layout.

8. The system of claim 1 wherein the club face is part of a golf club, the system further comprising:

an inertial navigation system connected to the golf club and adapted to capture inertial data during the swing and communicate the data to the processor; and

the processor performs the following additional steps:

f. converting the inertial data to rotation and translation values of an inertial coordinate frame;

g. converting the club face position data of step (e) to rotation and translation values of a club face coordinate frame; and

h. determining a relationship between the inertial coordinate frame and the club face coordinate frame.

9. The system of claim 8 , wherein the relationship in step (h) is determined by using a method for solving an overdefined system of equations.

10. The system of claim 8 , wherein the relationship between the club face coordinate frame and the inertial coordinate frame is used to calculate the club face position and orientation when at least one of the markers is not in the field of view of the cameras.

11. The system of claim 8 , wherein the golf club has a club shaft with a shaft axis, and the processor performs the following additional step of calculating the position of the club shaft based on a known relationship between the inertial navigation system and the shaft axis.

12. The system of claim 11 , wherein the system displays a 3D model of the golf club throughout at least a portion of the swing.

13. The system of claim 12 , wherein the portion of the swing modeled does not correspond to a portion of the swing that was captured by the cameras.

14. The system of claim 1 , wherein the processor performs the following additional step of calculating a club face attribute selected from a group consisting of: club swing path, club speed and club face orientation.

15. The system of claim 4 , wherein the processor performs the following additional step of calculating the time at which the club face first contacts the golf ball and further calculates a club face attribute at the time of impact selected from a group consisting of: club swing path, club speed, club face orientation and point of impact on the club face.

16. The system of claim 14 , further comprising a display connected to the processor, the display adapted to display the club face attribute.

17. The system of claim 1 , further comprising:

a tilt sensor adapted to measure the position of the at last two cameras relative to earth tangential and communicate tilt data to the processor; and

the processor performs the following additional step of using the tilt data to refine the calculation of step (e).

18. The system of claim 1 , wherein the golf club head, a golf club hosel connected to the club head or a shaft connected to the club head further comprises additional markers, and the processor performs the following additional step of:

f. identifying the additional markers from the plurality of images;

g, calculating and storing the geometric relationship between the additional markers and the markers found in step (d) and;

h. calculating the position of any marker that is occluded based on the geometric relationship to the markers that are visible; and

i. step (e) further comprises using the location position from step (h) to calculate the position of the club head during the swing.

19. The system of claim 1 , wherein the markers are retro-reflective.

20. The system of claim 1 , wherein the markers have a center with a contrasting concentric ring.

21. A method of measuring the orientation of a golf club head during a and impact with a golf ball, the golf club head having a club face with at least one score line, wherein the club face is substantially planar, the method comprising:

a. applying at least three markers placed on the club face, the marker placement is such that (1) the markers define the geometry of the club face, and (2) the markers' relative spacing and orientation to each other are within a known tolerance, wherein at least two of the markers define HEEL-TOE line that is parallel to the score line and at least one marker is not placed in alignment with the HEEL-TOE line;

b. capturing a plurality of images from at least two cameras of the golf club face during a swing and at impact;

c. performing threshold processing on the images to detect pixels that may correspond to the markers;

d. determining a position for the markers in three dimensional space;

e. finding a group of markers that fall within the tolerance of a known geometric relationship based on the planarity of the club face and the known orientation of the at least two markers along the HEEL-TOE line and the at least one marker not placed in alignment with the HEEL-TOE line;

f. labeling the markers based on their position with respect to the known geometric relationship; and

g. calculating the position of the club head during the swing based on the 3D position of the markers.

22. The method of claim 21 , further comprising the steps of:

h. identifying groups of neighboring pixels found in step (c);

i. performing a centroid algorithm on pixels groups detected in step (h); and

j. stereoscopically matching the centroids detected in step (i).

23. The method of claim 21 , wherein:

step (a) comprises applying four markers are placed at the TOE TOP, TOE, TOE BOTTOM and HEEL positions of the club face and wherein D 1 is defined as a line connecting the HEEL and TOE markers, D 2 is a line connecting the TOE TOP and TOE markers, and D 3 is a line connecting the TOE BOTTOM to TOE markers; and

wherein known tolerance of relative spacing and orientation between the markers comprises:

i. D 1 has and minimum and maximum known lengths for standard golf clubs;

ii. D 1 is always longer than D 2 and D 3 ;

iii. D 1 is substantially closer to horizontal relative to the ground than vertical at impact with a golf ball;

iv. the TOE TOP marker is above D 1 at impact;

v. the TOE BOTTOM marker is below D 1 at impact; and

vi. all markers lie substantially in the same plane.

24. The method of claim 21 , wherein step (a) comprises applying additional markers to the golf club head, a golf club hosel connected to the club head or a shaft connected to the club head further comprises additional markers, and the method further comprising the steps of:

h. identifying the additional markers from the plurality of images;

i, calculating and storing the geometric relationship between the additional markers and the markers found in step (f) and;

j. calculating the position of any marker that is occluded based on the geometric relationship to the markers that are visible; and

k. step (g) further comprises using the location position from step (j) to calculate the position of the club head during the swing.