<title>Real Time Two-Dimensional Mechanical Ultrasonic Sector Scanner with Electronic Control of Sector Width</title>

Abstract

An ultrasonic scanning system for echocardiography or the like, the system including a pivoted transducer in a manually-held housing containing a reversible low-inertia servo motor drivingly connected to the transducer via reduction gearing for oscillating the transducer, and a photoelectric system for generating sine and cosine voltages representing the real time positions of the transducer. An electronic position control circuit controls the motor, and thus controls the position of the transducer, by feedback signals derived from the difference between the sine function generated in the photoelectric system and a triangular wave generated in the control circuit. This difference is used to determine the magnitude and polarity of the voltage applied to the servo motor. This makes it possible to program the sector position of the transducer as a function of time. The photoelectric system may consist of a slotted disc mounted on the motor shaft between light sources and arrays of photocells. The disc has respective slots arranged to permit light proportionate to the sine and cosine of the sector position angle of the transducer to pass through the disc to the photocell arrays. The generated sine and cosine voltages are used to derive X and Y sweep voltages for an associated cathode ray tube display.