NON-CONTACT MULTIAXIAL INTERFEROMETRIC STRAIN GAGE

AN EFFORT DIRECTED TOWARDS THE DEMONSTRATION OF AN OPTICAL NON-CONTACT INTERFEROMETRIC STRAIN GAGE IS PROPOSED. THE CONCEPT IS BASED ON DETECTING THE MOTION OF A DIFFUSELY REFLECTING SURFACE BY IMAGING A MOVING FRINGE PATTERN ON THE SURFACE, AND THEN INFERRING THE MOTION OF THE SURFACE (IN A DIRECTION PERPENDICULAR TO THE FRINGES) FROM THE MODULATION OF THE DIFFUSELY REFLECTED RADIATION. THE PROPOSED INSTRUMENT RELIES ON THE USE OF OPTRA'S RECENTLY DEVELOPED STABILIZED 2-FREQUENCY LASER. THE DETECTED SIGNAL IS PROCESSED BY SUITABLE ELECTRONICS TO GIVE THE DISPLACEMENT OF THE SURFACE. THE TRANSDUCER HEAD CAN BE MADE SMALL AND, THROUGH THE USE OF OPTICAL FIBERS, CAN ALSO BE REMOTE FROM THE LIGHT SOURCE AND ELECTRONICS. RESOLUTION CAPABILITY WOULD BE AT THE SUBMICRON LEVEL WITH ALMOST UNLIMITED DISPLACEMENT RANGE CAPABILITY AND THE ABILITY TO HANDLE VELOCITIES FROM ZERO TO MANY CENTIMETERS PER SECOND. THROUGH THE USE OF THREE OR MORE TRANSDUCER HEADS, STRAINS IN MORE THAN ONE DIMENSION CAN BE MEASURED.