Abstract: Method and apparatus for determining the precise location of a drill bit tip relative to specified locations on a workpiece in precision automatic machining operations. Elastic waves are induced in a drill shank, guided through the shank to the drill bit tip and couple to the surrounding workpiece material in contact with the tip of the drill bit. Elastic wave sensors are disposed in elastic wave transmitting relation with the workpiece to detect the induced elastic waves. The precise location of the drill bit tip is determined by computing the propagation time of elastic waves from the drill bit tip to each of the respective sensors. In one embodiment, elastic waves are induced with contactless electromagnetic coupling via a magnetostrictive transduction technique. Other techniques for inducing elastic waves in a drill bit are described.

Abstract: A laser diode assembly and associated heat sink and excitation leads constructed to avoid the electromagnetic or magnetostrictive generation of stress or elastic wave disturbances in the diode, heat sink or associated components so as to maintain spectral purity in the diode laser emission. An improved laser diode assembly avoids the generation of elastic waves or vibrations within the leads, heat sink or associated structure of a laser diode by running excitation leads in a magnetic field cancellation arrangement to prevent magnetostrictively induced elastic waves in structure connected to the laser diode and to avoid vibration induced by coupling between the lead currents and external magnetic fields. The heat sink, electrical input and return leads and associated structure may be fabricated of a nonmagnetostrictive material to avoid magnetostrictively induced acoustic disturbances created by other magnetic field sources in the use environment of the laser diodes.

Abstract: Apparatus for precise location of surface defects in a conductive material with a very high probability of detection of minute surface cracks. The invention comprises a first wire adapted to be disposed in parallel fixed spatial relation with the conductive surface and a second wire adapted to be disposed perpendicular to or angularly with respect to and intersecting the first wire and also in parallel fixed spatial relation with the conductive surface. The first wire is electrically energized to induce eddy currents in the conductive material opposite in direction and parallel to the first wire. The presence of a defect or flaw in the conductive surface induces transverse eddy currents which couple to the second wire. In the absence of a defect, there is minimal eddy current coupling to the second wire. The eddy current in the second wire is amplified or otherwise processed to provide an output signal indicative of the presence of a defect.

Abstract: A heat sink for optical elements such as semiconductor laser diodes which avoids focussed reflection back to the optical element of stress waves generated within the heat sink by excitation of the elements. The avoidance of this focussed reflection enhances optical performance of such elements and in particular improves the purity of the lasing spectra of semiconductor laser diodes. The heat sink is dimensioned and provided with surface contours to reflect elastic waves in a pattern to avoid focussing the waves at the optical element thus minimizing the disturbance in operation of the element induced by the concentration of focussed stress waves. The element may be mounted off center on the heat sink at a position which avoids concentrations of stress waves. A coating is optionally applied to appropriate heat sink surfaces to dampen the stress waves incident at those surfaces and thus attenuate reflection with the result of reduced disturbance of the optical element.

Abstract: Method and apparatus for nondestructive inspection and detection of flaws in a workpiece according to four techniques is disclosed. Elastic waves are thermoelastically or electrodynamically induced in a workpiece by electric current energization of an elastic wave inducing source adapted to be disposed in contact with the workpiece remote from a defect. An acoustic sensor is disposed in elastic wave transmitting contact with the workpiece remote from the source and produces an output signal having an amplitude representative of received elastic waves. The presence of a crack, flaw or defect in the workpiece is detectable as a variation in the amplitude or other characteristics of the acoustic sensor output signal.

Abstract: An optoacoustic hydrophone for detection of acoustic waves in a fluid such as sea water. The hydrophone includes an optical waveguide comprising a fiber optic input lead, a fiber optic sensor, and a fiber optic exit lead, an optical subassembly and a signal processor. A coherent light beam generated by the optical subassembly is transmitted through the input lead and the sensor which is disposed in the fluid. Acoustic waves in the fluid modulate the index of refraction of the fiber optic sensor thereby modulating the transmitted light beam. The modulated light beam is directed through the fiber optic exit lead to a focus on one of two photodetectors. The other photodetector is oriented for receipt of light reflected from a partially reflective mirror disposed between the input fiber optic lead and the fiber optic sensor. The two light beams impinging on respective photodetector are combined with unmodulated light beams of slightly different frequencies to produce an interference pattern at each photodetector.

Abstract: An extendable probe that permits nondestructive ultrasonic inspection of a workpiece for flaws is disclosed which provides information indicative of flaw presence and location. The probe includes a pair of waveguides capable of elastic wave transmission. A first waveguide is excited to produce elastic waves which travel along the waveguide to an end of the waveguide in elastic wave transmitting contact with the surface of the workpiece under inspection. A second waveguide is maintained in contact with the workpiece a selected distance from the first waveguide and a sensor is disposed on the second waveguide for reception of elastic waves. In the absence of workpiece defects intermediate the contact points of the first and second waveguides, elastic waves are transmitted from the first waveguide to the second waveguide through the workpiece to the sensor and an output signal representative of transmitted elastic waves is produced by the sensor.

Abstract: A dark-field magneto-elastic non-destructive testing technique for detection of defects in a conductive material by inducing eddy currents or applying an electric current to the material along a path in such manner that the current will be diverted from the path in the vicinity of any material defect, causing the generation of acoustic waves locally from the interaction of the diverted current with a local magnetic field. The resulting acoustic waves are detected as an indication of the presence and location of a material defect. In typical application, a current is induced in the conductive material by the generation of eddy currents in the material along a substantially linear path by coupling from a current excited wire insulated from and applied near the surface of the material. The eddy current will tend to follow substantially the direction opposite of the current excited wire.

Abstract: A contactless self-scanning electro-elastic nondestructive testing technique is described for determining in real time the presence, location, number and size of defects present on the surface of a material under test. In one embodiment the apparatus includes means for inducing eddy currents or current flow in the surface of the conductive material. A magnetostrictive delay line is disposed parallel to the direction of current flow and equidistant and in fixed spatial relation with the surface. The presence of a crack or defect in the surface proximate to the delay line creates transverse eddy currents or transverse currents in the material which interact locally with the magnetostrictive delay line to induce elastic waves in the delay line. The elastic waves are generated in the delay line only at locations corresponding to the edges of the defects. An ultrasonic sensor coupled to the delay line is used to detect the elastic waves travelling in the delay line.

Abstract: A system for the detection of wing icing by monitoring variations in flexural waves transmitted through the outer plate material of an aircraft airfoil. The flexural waves in the plate of the wing airfoil are more subject to variation from the accumulation of ice on the wing than the compressional waves. The flexural waves are detected apart from the compressional waves, which tend to remain relatively constant, to provide an indication of icing. Changes in amplitude, phase or dispersion characteristics of the flexural waves are detected to indicate ice buildup, and, in one embodiment, these values are ratioed to the corresponding levels in the compressional wave in order to provide compensation for variations other than ice buildup. The ultrasonic waves may be coupled directly from a transducer to the airfoil plate or via an ultrasonic waveguide interposed between the transducer and the plate.

Abstract: A positioning determining system using a delay element and driver transducer for producing a traveling wave in the delay element, the presence of a traveling wave being detectable by a receiver transducer for determining the relative positions of the driver and receiving transducers. In accordance with the invention, a driver transducer, the delay element, and a second transducer form a self-excited feedback loop oscillator, the frequency of oscillation of which is determined by the spatial filtering provided by the second transducer so as to generate a traveling wave having a selected wavelength. The system includes automatic frequency selection to compensate for position sensing errors due to changes in the velocity of propagation of elastic waves arising because of temperature effects on the delay medium.

Abstract: A system for determining X and Y coordinate positions on a surface wherein a first transducer generates plane waves having electromagnetic fields associated therewith, which plane waves travel along the direction of the X-coordinate and a second transducer generates plane waves having electromagnetic fields associated therewith, which plane waves travel along the direction of the Y-coordinate. A receiver transducer at the position to be determined detects the presence of the electromagnetic fields associated with the plane waves as they travel past the receiver transducer and the distances traveled by the plane waves are appropriately calculated either by determining the times of travel using pulse wave signals or by determining phase relationships using continuous wave signals.

Abstract: Apparatus for determining linear or angular measurements or measurements of positions on a planar or curved surface, which apparatus uses at least one delay element, such as a magnetostrictive element, for example, which is capable of supporting an acoustic wave signal. The one or more delay elements may be in the form of bands, rods, wires, planar or spherical structures, and the like, and can be arranged in various embodiments to provide linear or angular position information for single, dual, and multiaxis geometry. They can be used, for example, to provide single or multispeed resolver operation and three-axis attitude read-out. In preferred embodiments the apparatus uses phase measurement techniques so that high accuracy can be achieved.

Abstract: A position determining device having a distributed sensing element, such as a delay element, positioned at a selected angle greater than 0.degree. with respect to at least one selected direction along which a position is to be measured. Means for determining the position along the distributed element are provided, e.g., a driver transducer and a receiver transducer relatively movable along the delay element by which the delay of a signal travelling along the delay element and, hence, the position therealong is determined. Means responsive to such position determination are further included for calculating from such position determination the position along the at least one selected direction. The invention is especially useful for multi-axis position determination wherein, for example, a single delay element can be positioned at a selected angle with respect to each of two axes, so that linear or angular position determination can be made with respect to each axis.

Abstract: A position determining system in which a delay element has at least one driver transducer at at least one position and at least one receiver transducer at at least one other position, the transducers being arranged so that a traveling wave signal at the driver transducer travels along the delay element from the first said at least one position to said at least one other position so that a distance which is to be measured is traversed more than once. Certain embodiments accomplish such operation by providing a "folded" or U-shaped delay element, the driver and receiver being located on separate legs thereof so that the traveling wave traverses both legs of the delay element so that the distance which is to be measured is traversed twice, thereby increasing the resolution of the overall device.

Abstract: Apparatus for determining linear or angular measurements or measurements of positions on a planar or curved surface, which apparatus uses at least one delay element, such as a magnetostrictive element, for example, which is capable of supporting an accoustic wave signal. The one or more delay elements may be in the form of bands, rods, wires, planar or spherical structures, and the like, and can be arranged in various embodiments to provide linear or angular position information for single, dual, and multiaxis geometry. They can be used, for example, to provide single or multispeed resolver operation and three-axis attitude read-out. In preferred embodiments the apparatus uses phase measurement techniques so that high accuracy can be achieved.