Scan-control apparatus for pulse-echo ultrasonic imaging system incorporating oscillated transducer

Claim 1

In a pulse-echo ultrasonic wave energy imaging system comprising (1) a mechanically-oscillated electro-acoustic transducer responsive to the energization thereof for generating a scanning beam of pulsed ultrasonic wave energy that is propagated through a given liquid toward a remotely-located given structure to be insonified, said structure returning ultrasonic wave energy echoes propagated through said liquid to said transducer for detection and display on a display device of an image of said insonified structure, wherein said transducer is completely immersed in said liquid and is mounted for angular movement about a given axis; (2) an angle sensor for deriving an output signal which is a predetermined function of the angular position of said mechanically-oscillated transducer, and (3) electronic means responsive to said output signal from said angle sensor for energizing said transducer at each of a group of specified angular positions of said transducer during each cycle of oscillation thereof; the improvement therein: wherein said angle sensor comprises an analog angle sensor immersed in said propagation liquid and directly coupled to said transducer for deriving a continuous output signal having a value which is substantially proportional to the then-existing angular position of said oscillated transducer, and wherein said electronic means comprises an analog-to-digital converter for producing a multi-bit digital output of the angular position of said oscillated transducer in which the least significant bit corresponds with a predetermined angular incremental change in the angular position of said oscillated transducer, first means for periodically applying a sample of said analog sensor output signal to the input of said analog-to-digital converter at a rate sufficiently high that said analog angle sensor output signal is sampled at least once during each successive angular incremental change of said oscillated transducer, and second means operative during the occurrence of a certain one of the two half-cycles of each oscillation of said transducer for energizing said transducer in response to the occurrence of each successive odd value of the least significant bit of the digital output of said analog-to-digital converter and operative during the occurrence of the other one of the two half-cycles of each oscillation of said transducer for energizing said transducer in response to the occurrence of each successive even value of the least significant bit of the digital output of said analog-to-digital converter.