Ultrasonic scanner

摘要

The rotation of a motor is converted into a swinging movement of an ultrasonic transducer by a conversion mechanism. The relationship between a rotation angle theta of the motor and a swinging angle eta of the ultrasonic transducer can be expressed by eta =tan-1 (sin theta ). The rotation of the motor is detected by a rotation detector of a reluctance type having an eccentric rotor. A signal having a nonlinear relationship with respect to an actual rotation angle theta of the motor, which can be expressed by the following equation, is supplied to a motor driver from the rotation detector: theta D= theta +K sin 2 theta . A dummy rotation angular velocity omega D which is a rate of change with respect to a time of a dummy rotation angle theta D is obtained by the driver. The motor is servo-driven with reference to a deviation value between the dummy rotation angular velocity omega D and a velocity setting value omega M. Therefore, the motor is rotated so that the rotation angle theta has the nonlinear relationship with respect to time t, as expressed in the following equation: theta = omega Mt-K sin 2 omega Mt. A scanning velocity V of an ultrasonic beam is substantially constant.