| 摘要 |
PROBLEM TO BE SOLVED: To set a same rotation reference position at all times and to prevent a time lag in obtaining three-dimensional data of an ultrasonic image. SOLUTION: An ultrasonic transducer 21 transmitting and receiving the ultrasonic wave is held by a pulley 22 so as to freely rotate in a same plane, the pulley is reciprocatingly rotated via a wire 24, its rotation angle is detective by a magnetic body 25 and a magnetic resistance element 26, the setting of the rotation reference position and the regulation of the rotation quantity of the pulley are implemented by notches 22a, 22b engaged with a projection 36, and the pulley is reversely rotated in a prescribed direction after rotating it by a prescribed angle exceeding the initial rotation position so as to be set in an initial rotation position. This constitution can set the same rotation reference position at all times so as to start the scanning of the ultrasonic beam from the initial rotation position without any time lag.
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