Method for extracting impact time in golf swing

1. A method for extracting impact time in a golf swing, comprising the steps of:

acquiring at least one chronological waveform among chronological waveforms of an angular velocity ωx about x-axis, an angular velocity ωy about y-axis, and an angular velocity ωz about z-axis obtained when a golf ball is hit by a golf club attached with a sensor capable of measuring angular velocities about three axes, when the x-axis is orientated in a direction along a toe-heel direction of a golf club head, when the y-axis is orientated so as to follow along a direction in which a ball is hit, and when the z-axis is orientated to match an axial direction of a shaft;

acquiring timing at which laser light, disposed immediately in front of where the golf club head impacts the ball, is shielded by the golf club head or the shaft; and

determining an impact time using the at least one chronological waveform and the timing, wherein

the step of determining comprises the sub-steps of:

calculating, when timing at which a signal indicating laser blockage transmitted from a light receiver configured to receive the laser light is received by the sensor is defined as trigger timing, an amount of change of the angular velocity about the x-axis in a predetermined time interval before the trigger timing; and

determining whether or not the calculated amount of change of the angular velocity is larger than a predetermined threshold.

2. The method for extracting impact time in a golf swing according to claim 1 , wherein at the step of determining, when the calculated amount of change of the angular velocity is determined to be smaller than a predetermined threshold, the step of determining further comprises the sub-steps of:

judging whether or not the angular velocity ωz is over range in a predetermined time duration;

configuring a first provisional impact time when a judgment of over range is obtained in the step of judging, and configuring a second provisional impact time when a judgment of over range has not been obtained in the step of judging;

acquiring three candidates for impact time from respective chronological waveforms of the angular velocity ωx, the angular velocity ωy, and the angular velocity ωz using the configured first or second provisional impact time as reference; and

determining impact time in accordance with a predetermined determination criterion from the three candidates for impact time.

3. The method for extracting impact time in a golf swing according to claim 2 , wherein the first provisional impact time is set to a time at which over range has occurred in the chronological waveform of the angular velocity ωz.

4. The method for extracting impact time in a golf swing according to claim 3 , wherein, when a minimum value has occurred in the chronological waveform of the angular velocity ωz in a first predetermined time before a time at which a maximum value has occurred, the second provisional impact time is set as a time at which a maximum value has occurred in a second predetermined time before the time at which the minimum value has occurred.

5. The method for extracting impact time in a golf swing according to claim 4 , wherein the laser light is disposed, when a flight direction of the ball is used as reference, 1 mm to 10 mm behind a back end of a ball.

6. The method for extracting impact time in a golf swing according to claim 3 , wherein the laser light is disposed, when a flight direction of the ball is used as reference, 1 mm to 10 mm behind a back end of a ball.

7. The method for extracting impact time in a golf swing according to claim 2 , wherein, when a minimum value has occurred in the chronological waveform of the angular velocity ωz in a first predetermined time before a time at which a maximum value has occurred, the second provisional impact time is set as a time at which a maximum value has occurred in a second predetermined time before the time at which the minimum value has occurred.

8. The method for extracting impact time in a golf swing according to claim 7 , wherein the laser light is disposed, when a flight direction of the ball is used as reference, 1 mm to 10 mm behind a back end of a ball.

9. The method for extracting impact time in a golf swing according to claim 2 , wherein the laser light is disposed, when a flight direction of the ball is used as reference, 1 mm to 10 mm behind a back end of a ball.

10. The method for extracting impact time in a golf swing according to claim 1 , wherein the laser light is disposed, when a flight direction of the ball is used as reference, 1 mm to 10 mm behind a back end of a ball.