| 摘要 |
PROBLEM TO BE SOLVED: To provide an ultrasonic probe including a small encoder to be rapidly recovered to an origin when a power source is turned on. SOLUTION: An ultrasonic probe comprises an acoustic element 1; a driving part 2 for rocking the acoustic element; and the encoder 3 for detecting the rotation angle of the acoustic element. The encoder has a magnetic drum; a magnetic field detecting part for the rotation angle which detects the rotation angle, based on a magnetic field formed by the magnetic drum; and a magnetic field detecting part for the origin which detects the origin. The magnetic drum has three magnetic areas which are arranged in a circumferential direction. North polar and south polar magnetic bodies are alternately arranged in the circumferential direction in the first magnetic area. The north polar and south polar magnetic bodies are arranged in a layer shape in the rotation axial direction of the encoder in the second magnetic area. No magnetic bodies are arranged or the north polar and south polar bodies are arranged so that the bodies have reverse polarity to the second magnetic area in the third magnetic area. The magnetic field detecting part for the origin is arranged to detect a boundary between the second and the third magnetic areas in a state where the acoustic element is positioned at the origin. COPYRIGHT: (C)2006,JPO&NCIPI
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