In a mechanically scanned ultrasonic probe, an ultrasonic transducer is swingably mounted on a drive shaft which is given a swinging transversal movement and a reciprocating longitudinal movement. The transducer emits an acoustic beam which is steered in a raster format in response to the swing and reciprocating...http://www.google.com/patents/US4637256?utm_source=gb-gplus-sharePatent US4637256 - Ultrasonic probe having dual-motion transducer
