ULTRASONIC DETECTOR CELL AND SYSTEM

• Main Author: SANDHU, JASWINDER S
• Format: Patent
• Language: English; French
• Published: 06.12.1988
• Edition: 4
• Subjects: DEVICES OR ARRANGEMENTS, THE OPTICAL OPERATION OF WHICH ISMODIFIED BY CHANGING THE OPTICAL PROPERTIES OF THE MEDIUM OF THEDEVICES OR ARRANGEMENTS FOR THE CONTROL OF THE INTENSITY,COLOUR, PHASE, POLARISATION OR DIRECTION OF LIGHT, e.g.SWITCHING, GATING, MODULATING OR DEMODULATING; DIAGNOSIS; FREQUENCY-CHANGING; HUMAN NECESSITIES; HYGIENE; IDENTIFICATION; MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC ORINFRASONIC WAVES; MEASURING; MEDICAL OR VETERINARY SCIENCE; NON-LINEAR OPTICS; OPTICAL ANALOGUE/DIGITAL CONVERTERS; OPTICAL LOGIC ELEMENTS; OPTICS; PHYSICS; SURGERY; TECHNIQUES OR PROCEDURES FOR THE OPERATION THEREOF; TESTING

There is disclosed herein an orthoscopic ultrasonic imaging system which includes an acoustic transducer for insonifying an object to be inspected and an improved liquid crystal detector cell for receiving an imaging beam from the insonified object and for displaying a visible image. An electric, magnetic or acoustic biasing field is applied to the liquid crystal cell for raising the cell to an acousto-optic threshold which permits detection and display of low intensity imaging signals. The cell surfaces which contact the liquid crystal material are treated so as to preferentially align the liquid crystal molecules for situations where electric or magnetic field biasing is used. Preferential alignment means that the longitudinal axis of the molecules are on average parallel to each other as indicated by the bulk director. Furthermore, when an electric biasing field is employed, the surface treatment to be used is selected in relation to the dielectric properties of the chosen liquid crystal material. The operation of the system described herein is based upon the effect of liquid crystal/contact surface interaction; liquid crystal/biasing field interaction; and liquid crystal/imaging beam interaction on the orientation of the sample director. Using the improved liquid crystal system, low intensity, acoustic fields ¢e.g. less than 10-3 w/cm2 (watts per square centimeter)! can be detected and displayed, and the object being examined can be insonified with low intensity ultrasonic beams.