| 摘要 |
PROBLEM TO BE SOLVED: To measure a speed normally even when reflected waves received by a part of a plurality of acoustic receivers are less than a signal level required for a normal signal processing operation when the speed of an object to be measured is measured. SOLUTION: Ultrasonic waves are sent toward an impact point on a ball, reflected waves from a heat part passing the impact point are received by three acoustic receivers 21, and relative speeds of the head part with reference to the acoustic receivers 21 are calculated respectively. On the basis of their calculated results and on the basis of position-coordinate data which uses impact point of each acoustic receiver as the origin, the speed vector of the head part in the impact point is found. Two each of acoustic receivers 21A1 , 21A2 are installed at three ultrasonic-wave reception parts 20, signal levels of two received reflected waves are compared by a comparator 32, and only a reflected- wave signal whose signal level is larger is selected by a switching circuit 33. In a speed-vector calculating and processing operation, a Doppler signal component based on the selected reflected-wave signal is used.
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