Game ball monitoring method and apparatus
First Claim
1. A method of monitoring in a ball game the position, relative to a reference line extending linearly between near and far ends thereof, of the first contact of a game ball with a playing surface carrying said reference line, which method includes the following steps:
- (a) from said near end of the reference line directing a collimated radiation along and parallel with the reference line to irradiate a predetermined field at said far end of the reference line and lying adjacent the reference line, said field being such as will be materially but not wholly shaded by the passage of a game ball through the radiation when in play near the reference line;
(b) at said far end of the reference line sensing the game ball'"'"'s presence in the radiation by detecting the shadow cast at that end by the game ball;
(c) when the game ball is in flight through said field detecting from said shadow the passage of the front of the game ball through successive closely-spaced positions in the direction of flight of the game ball;
(d) for each such closely-spaced position, determining the height of the top of the game ball at a position spaced one half the diameter of the game ball rearwardly of the front of the game ball;
(e) for each such closely-spaced position, comparing the detected height of the top of the game ball with a stored game ball diameter reference height stored in a storage means; and
(f) determining as the position of first contact of the game ball with the playing surface the game ball position at which the reducing height of the top of the game ball has become equal to the stored game ball diameter reference height.
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Abstract
A method and apparatus for determining in a ball game (for example, tennis) the position, relative to a service reference lines (12), of the first contact of the ball (14) with the playing surface. In play, the ball passes through a collimated light beam to intercept light directed at a light sensing array, which comprises many closely spaced sensors (46) arranged in column and row formation. A signal storage means includes one storage device for each of the sensors, so that the position of the ball may be tracked in the storage means as it passes through the light beam. The said position is determined by tracking in the storage means the front of the ball (14F), and for each sensed position of the ball front determining the then height (H) of the top of the ball, at a position displaced rearwardly one half the ball diameter. The detected height of the top of the ball is compared for each position of the ball front with a ball reference height to ascertain the said ball position at the moment the height of the top of the ball equates with the ball reference height. Alternatively, real-time comparisons of detected and reference ball heights may be made by a computer operating on the interrupt principle, thus obviating the need for the storage devices in the making of comparisons.
26 Citations
24 Claims
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1. A method of monitoring in a ball game the position, relative to a reference line extending linearly between near and far ends thereof, of the first contact of a game ball with a playing surface carrying said reference line, which method includes the following steps:
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(a) from said near end of the reference line directing a collimated radiation along and parallel with the reference line to irradiate a predetermined field at said far end of the reference line and lying adjacent the reference line, said field being such as will be materially but not wholly shaded by the passage of a game ball through the radiation when in play near the reference line;
(b) at said far end of the reference line sensing the game ball'"'"'s presence in the radiation by detecting the shadow cast at that end by the game ball;
(c) when the game ball is in flight through said field detecting from said shadow the passage of the front of the game ball through successive closely-spaced positions in the direction of flight of the game ball;
(d) for each such closely-spaced position, determining the height of the top of the game ball at a position spaced one half the diameter of the game ball rearwardly of the front of the game ball;
(e) for each such closely-spaced position, comparing the detected height of the top of the game ball with a stored game ball diameter reference height stored in a storage means; and
(f) determining as the position of first contact of the game ball with the playing surface the game ball position at which the reducing height of the top of the game ball has become equal to the stored game ball diameter reference height. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 23)
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13. Apparatus for monitoring in a ball game the position, relative to a reference line extending linearly between near and far ends thereof, of the first contact of a game ball with a playing surface carrying the reference line, which apparatus comprises:
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(a) at said near end of the reference line, radiation emitting means for directing a collimated radiation along and parallel with the reference line to irradiate a predetermined field at said far end of the reference line and lying adjacent the reference line, said field being such as will be materially but not wholly shaded by the passage of the game ball through the radiation when in play near the reference line;
(b) at said far end of the reference line, radiation receiving means comprising a plurality of radiation sensors for receiving at closely spaced locations in said field respective elements of said radiation, which locations are disposed uniformly in vertical column and horizontal row formation, which radiation receiving means is arranged to sense the game ball'"'"'s presence in the radiation by the shadow cast at said far end by the game ball;
(c) means for detecting when the game ball is in flight through said field the passage of the front of the game ball through successive closely-spaced positions in the direction of flight of the game ball; and
(d) means for determining, each such closely-spaced position, the height of the top of the game ball at a position spaced one half the diameter of the game ball rearwardly of the front of the game ball;
(e) means for comparing, for each such closely-spaced position, the detected height of the top of the game ball with a stored game ball diameter reference height; and
(f) means for determining as the position of first contact of the game ball with the playing surface the game ball position at which the reducing detected height of the top of the game ball has become equal to the stored game ball diameter reference height. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 24)
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Specification