IMPROVEMENTS IN OR RELATING TO ULTRASONIC DETECTION APPARATUS MORE PARTICULARLY FOR DIAGNOSTIC APPLICATION

摘要

1,212,349. Ultrasonic inspection devices; diode gating circuits. T. G. BROWN. 16 April, 1968 [14 April, 1967], No. 17304/67. Headings H3P and H4D. In a pulse-echo system for the ultrasonic examination of an object a transducer probe capable of translational movements along three co-ordinate axes and of rotation about two axes is scanned over the object and echo signals are gated so that only those arising from reflection at a particular internal plane section of the object are displayed on a cathode-ray tube. In the Fig. 3 embodiment probe 10 is mounted for translational movement along axes X, Y, Z and rotational movement about two mutually orthogonal axes (one of which is parallel to a translational axis). Signals representing the X, Y and Z eo-ordinates of the probe are derived from translational X, Y and Z resolvers 35, 31, 33 and rotational resolvers (sine/cosine potentiometers) 36, 37, and are applied to timebase generators 51, 52, 53 respectively. For displaying a cross-section of the object parallel to the XY plane the signals representing the X and Y co-ordinates of the probe control the sweep amplitudes for the X and Y deflections of cathode-ray tube (C.R.T.) 58, and the Z signal is compared in coincidence detector 59 with a preset signal V from 60 representing a predetermined range z from which echoes are to be displayed. If the z signal lies between V and V + #V coincidence detector 59 opens gate 55 to pass echo signals to the beam intensity control circuit of C.R.T. 58. Cross-sections parallel to the XZ or YZ planes may be displayed by supplying coincidence detector 59 with the Y or X signal instead of the Z signal, the C.R.T. sweeps being controlled by the X and Z or Y and Z signals. Two or more crosssections in parallel or non-parallel planes may be displayed simultaneously by providing a different C.R.T. and associated coincidence detector for each cross-section. Co-ordinate transformation circuits may be connected between time base generators 51, 52, 53 and deflection amplifiers and coincidence circuit 56, 57, 59 for displaying cross-sections in skew planes. Prior art scanning and display systems, including a stereoscopic display system, are discussed. Gating circuits (Fig. 5).-An AND gate comprising diodes 77, 78, 79 passes echo signals from buffer amplifier 79a to C.R.T. 58 only when the outputs of both differential amplifiers 75, 76 are negative. Each differentiated amplifier is arranged to provide a negative output when the voltage at its upper input is more positive than the voltage at its lower input. Potentiometer 60 provides a voltage V for the lower input of amplifier 76. Network 71, 72, 73 provides a voltage #V so that the voltage on the upper input of amplifier 75 is V + #V. The other inputs of the differential amplifiers are supplied with the Z signal, so that both amplifier outputs will be negative only when the Z signal lies between V and V + #V.