| 摘要 |
A pulse-echo method of ultrasonic scanning to investigate the interior of a body involves contacting the body with an ultrasonic transducer at a fixed point having a first axis therethrough which is fixed relative to the body, projecting a pulsed ultrasonic beam through the fixed point along a second axis which is fixed relative to the transducer, and rotating the transducer about the first axis while progressively varying the angular inclination of the second axis to the first axis. The beam path then describes a spirally wrapped conical surface with its apex at the fixed point, which means that the transducer does not track across the body, but simply rolls on it at the fixed point, and this alleviates the transducer/body coupling problems which otherwise arise. Apparatus for this purposes comprises a support structure to define the first axis, a circular arcuate carriageway rotatable about this axis to produce the wrapping motion and to define by its centre of curvature the fixed point, a carriage extending transversely from the carriageway to define the second axis and movable along the carriageway to produce the progressive angular variation or spiral effect, and a transducer with its periphery at the fixed point, its beam path along the second axis, and rotatably mounted in the carriage to effect a rolling action on the body.
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