Showing papers on "Transducer published in 1977"

Rejection of flow noise using a coherence function method

Abstract: A method has been developed for rejecting transducer flow‐noise interference. The method makes use of coherence‐function relations between simultaneous pressure measurements at three transducers in the signal field and extracts from the flow‐noise background the power spectrum of the signal as received at each transducer. The signal in question can be periodic or stationary random. The coherence function relations are derived on the basis of a multivariate, random‐process model. The theory indicates that for a single source or for a group of completely coherent sources, the three transducers can be placed at arbitrary locations in the signal field. For a group of sources that are not completely coherent, the transducers must be located close together relative to the distance from the group. In any case, however, the flow noises at the transducers must be mutually independent. Successful results were obtained in laboratory tests of the method. In these tests a 10–15‐dB reduction in flow‐noise interference was attained. The method can also be used to reduce other types of noise such as instrument electronic noise.

Photoacoustic technique for determining optical absorption coefficients in solids.

Abstract: An investigation was made of a photoacoustic technique for determining the optical absorption coefficient in solids. A train of laser pulses was passed through the solid, and a piezoelectric transducer attached directly to the sample measured the amplitude of the elastic wave generated by the absorbed radiation. Calibration was performed at a wavelength of known absorption. The sensitivity of the technique was found to be limited to about 1 × 10−5 cm−1 in our samples due to radiation scattered onto the transducer, but the technique is capable of measuring absorption coefficients in the 10−6 cm−1 range using laser powers of about 1 W.

Ultrasonic multi-sector scanner

Abstract: A steered beam B-scan ultrasonic imaging system has a linear transducer array divisible into multiple sub-arrays of transducer elements each operable to perform a sector scan, with the origin points displaced longitudinally along the array between sector scans. The system performs overlapping sector scans and is capable of imaging randomly oriented specularly reflecting targets. Time delays in the transmitting and receiving channels to steer the transmitted beam and to focus the received echoes are provided by digital techniques, by reversible digital shift registers, or by charge coupled device delay lines. The multiple sector image is displayed in real time in an intensity versus displacement format on a cathode ray tube.

Coupled surface-acoustic-wave resonators

Abstract: Coupled Surface-Acoustic-Wave (saw) grating resonators are investigated analytically with a transmission-matrix technique, and the measured frequency responses at ∼145 MHz of devices on YZ-LiNbO 3 with Ti-diffused gratings are compared with the theoretical results. Coupled-mode theory is applied to derive the two-by-two transmission matrix relating the acoustic wave amplitudes at the input and output of a surface wave grating. Using the transmission matrices, the external transmission through a saw resonator is found by matrix multiplication. Some fundamental aspects of resonator passband synthesis are introduced by considering the transmission through several acoustically cascaded resonators. Resonator filters where the transducers couple directly to the resonant cavities are treated by developing a description of the transducer that is compatible with the transmission matrix of the grating. The analysis technique is then applied to the familiar two-port resonator-filter. Next, coupled resonator-pairs with a transducer in each cavity are considered in detail for: (i) collinear acoustic coupling, (ii) multistrip coupling, and (iii) transducer coupling. Experimental results are presented for each configuration considered and good agreement with the analytical description is found in each case.

Two wheel ultrasonic rail testing system and method

Abstract: A system and method for performing ultrasonic inspection of a length of test material with ultrasonic transducing means emitting a beam of ultrasonic energy from within sealed wheel means containing a coupling fluid therein and having a flexible cylindrical surface member transparent to the ultrasonic beam and arranged for rolling contact along the test material. The system and method are characterized by spaced leading and trailing wheel means arranged for rolling contact along the length of test material. Ultrasonic transducer means in each of the leading and trailing wheel means are oriented so that a beam of ultrasonic energy emitted from the transducer means in one wheel means will enter the test material, be reflected from the bottom surface thereof, and be directed to and received by the transducer mean in the other wheel means. Each wheel means further includes ultrasonic transducers emitting ultrasonic energy longitudinally in front of and behind the two wheels, and side-looking transducer means for emitting ultrasonic energy into the test material transversely to the direction of travel. Additional transducers emit radiation perpendicularly through the test material. Accordingly, the test material is fully probed and many different kinds of defects can be detected. The transducers are positioned away from the test material by a distance which is substantially the near field distance of the ultrasonic beam. Means are provided for adjusting the spacing between two wheels, to allow different thicknesses of test material to be tested by interwheel transmission of the ultrasonic beam.

Catheter head-type transducer

Abstract: A catheter having a transducer that comprises an organic high polymer filmlike piezoelectric element or elements. The catheter has the capacity of converting, safely and with accurate wave shapes, pressure in the living body, for example blood pressure, pressure in a thorax, or intrauterine pressure, into an electric signal. By means of this catheter, pressure in the living body can be measured.

Transducer assembly for megasonic cleaning

Abstract: A transducer assembly adapted to oscillate at an ultrasonic frequency comprises a metallic foil having a back surface, at least one transducer having one face thereof mounted adjacent to the back surface by conductive means disposed therebetween, and insulating means disposed in the area adjacent to the back surface and surrounding the edges of the transducer for supporting the foil and transducer in relatively fixed relationship.

Two axes controller

Abstract: A two axis controller for controlling a tanker aircraft in-flight refueling boom while maneuvering prior to engagement with the receiver aircraft and including a boom load alleviation system after engagement Movement of the control stick is transmitted mechanically to a position transducer The transducer provides a signal to an actuator to effect boom control The transducer output is also transmitted to a servo motor which is mechanically connected to the control stick During the free flight mode, when the operator is manually controlling the boom, the servo motor provides a resisting force to stick movement that varies as a function of the transducer signal Following coupling of the two airplanes, which initiates the automatic load alleviation system, the same servo motor back drives the control stick in response to boom force and position signals to alleviate boom forces Manual override of the automatic system is possible at any time

Ultrasonic scanning apparatus

Abstract: An ultrasonic scanner having a housing, an ultrasonic transducer disposed within the housing and mounted for movement in a predetermined path therewithin Magnetic means are provided for effecting movement of the transducer in a predetermined path, and electrical means are provided for energizing the transducer and receiving signals therefrom The scanner may be servo-controlled and be provided with position sensing means for determining the position of the transducer within the predetermined path, and signal processing means for receiving feedback signals from said position sensing means and adjusting said transducer position responsive to said feedback signals indicating the existence of a departure from the desired transducer position

Transducer probe for pulse-echo ultrasonic exploration

Abstract: A pulse-echo ultrasonic transducer probe includes a substantially centrally disposed axial bore running therethrough and a radial slot extending from the bore to the periphery of its housing. A slotted cap dimensioned to rotatably fit over the top of the housing is provided with a hollow semi-circular stem extending into the bore, the slot of the cap being aligned with the longitudinal opening of the stem. The slot of the cap and that of the transducer, when passing a surgical instrument through the bore into an opaque body, are rotatably adjusted so that they are out of registry with one another for supporting the surgical instrument and for maintaining the instrument in the center of an ultrasonic search beam. Subsequently, after the instrument has reached the desired position in the body the slots are brought into registry for providing removal of the transducer probe from around the instrument.

Square and rectangular electroacoustic bender bar transducer

Abstract: The transducer's active elements are a plurality of thin, narrow, piezoelric bars bonded side-by-side to a flexible plate. Electrically, a circuit is coupled across the thickness of each bar or strip to include the bars as a plurality of parallel capacitors. The plate has a fixed length that is maintained during operation. Consequently, piezoelectric length expansions and contractions of the bars are translated into an oscillating bending motion of the bars and the plate for transducing purposes.

Dynamically variable electronic delay lines for real time ultrasonic imaging systems

Abstract: A dynamically variable electronic delay line for real time ultrasonic imaging systems is disclosed so as to controllably phase the signals associated with an array of electro-mechanical transducer elements and thereby enable the selective scanning and dynamic focusing of a target. A controllable variable electronic time delay apparatus is coupled to each of the electromechanical transducer elements of the array and in one embodiment thereof constitutes an electronic memory having separate write-in and read-out addressing capabilities. The signals associated with a respective ultrasonic transducer element are fed in at selected write-in addresses and subsequently read-out and extracted after an initial time delay interval. The write-in and read-out address pointers of the memory are continuously sequenced during operation of the device and the time delay interval is a function of the difference between the addresses, as well as the clock rate. The initial delay can be varied by instantaneously modifying either the write-in or the read-out address pointer during the sequencing thereof, such modification being defined as an "edit-splice" technique. In other embodiments of the invention, the time delay apparatus could comprise a multiple cell memory or register in which a plurality of signals from an associated transducer element are stored and subsequently read-out after an initial time delay, which delay can be changed either by varying the effective length of the shift register or by varying the clock rate at which the shift register advances the signals stored therein, or through an "edit-splice" technique as above-described.

Corrosion resistant thin film head assembly and method for making

Abstract: A slider element includes a thin film transducer deposited onto a slider along at least one of the rails forming the flying air bearing surface with a magnetic media. A portion of the end tips of the pole pieces and gap of the thin film inductive transducer and a portion of the slider rail adjacent to the transducer is etched by a sputter etching process. A layer of a passivation material such as chromium is sputter deposited into the etched portion such that the leading portion of the rail protects the passivation material from wear. The passivation material over the pole tips of the transducer prevents the corrosion of the iron-nickel alloy comprising the pole tips.

Magnetic recording device for double sided media

Abstract: In a data storage system using a non-rigid magnetic storage surface, such as a floppy disc, and in which recording and reproduction are to be effected on both sides of the element by contact transducers, significant improvements over prior art devices are realized by employing a fixed transducer on one side of the element, and a movable transducer element on the opposite side. The movable transducer may be gimbal mounted on a pivoted spring-loaded arm of low mass and high stiffness to urge the magnetic storage surface against the fixed transducer with a light force. The force is adequate, together with a slight penetration of the fixed transducer into the plane of the disc, to correct deflections of the storage surface in directions transverse to its principal plane in the region between the transducers. Thus the transducers are maintained in operative relation for maximum flux interchange, but without introducing undue wear or requiring a long head settling time.

Geometrical Spectrum Broadening in Ultrasonic Doppler Systems

Abstract: The bandwidth of the output spectrum of blood flow meters may prove of value in estimating flow parameters such as the degree of turbulence. It is therefore important to determine the various factors which affect this bandwidth. It is shown that scatterers moving in the near field of the sound beam generated by a single transducer ultrasound Doppler system produce a spectrum whose breadth is primarily determined by the range of angles over which backscattered ultrasound is received by the transducer. An empirical method of calculating the bandwidth of the output spectrum is described, and the results are compared with direct Doppler measurements. Since the spectrum broadening depends on the angle between the target path and the ultrasound beam, it is suggested that the phenomenon may be usable to provide an independent measure of this angle.

Hand held ultrasonic nebulizer

Abstract: An improved ultrasonic nebulizer for administering a medicament aerosol to a patient. Output from an oscillator is connected through a series inductor to a transducer adjacent a reservoir which generates aerosol from the medicament. The inductor is tuned for series resonance with the bulk capacitance of the transducer. An impedance change in the transducer when liquid is removed or consumed from the reservoir reduces the power delivered to the transducer and prevents transducer damage.

Semiconductor transducer packaged assembly

Abstract: A semiconductor transducer chip is flip-chip bonded to a semiconductor interface chip, which is mounted on the ceramic package. Thermal coupling between the package and the transducer chip is minimized by the small contact area between the transducer chip and interface chip. Micron size spacing between the spring membrane in the transducer chip and the interface chip produces squeeze film damping of the spring membrane.

Device for examination by means of ultrasonic vibrations

Abstract: A device for ultrasonic examination, comprising a flat mosaic of a row of transmission transducers and a number of rows of receive transducers which are symmetrically arranged with respect thereto. The device furthermore comprises means for applying actuation pulses to one transmission transducer at a time, and means for enabling receive transducers in the time interval following each actuation pulse, and for at the same time displaying on an image display device an image of a section of the examined body in a plane perpendicular to the plane of the mosaic and through the line of transmission transducers.

Noninvasive blood pressure monitoring transducer

Abstract: Intra-arterial blood pressure is noninvasively measured and monitored by an electromechanical force sensor which is made up of an array of individual force sensing elements, each of which has at least one dimension smaller than the lumen of the underlying artery wherein blood pressure is to be measured, and the individual force sensitive element which generates the waveform of maximum amplitude is used to monitor blood pressure.

Ultrasonic body scanner and method

Abstract: Non-destructive testing with ultrasonic energy is performed by scanning a focused ultrasound beam until a region of interest is detected and rescanning this region with the beam focused at a plurality of depths. Apparatus for ultrasonic body scanning for medical purposes may include an actively driven transducer crystal which may be dynamically focused. A beam of energy produced by the transducer will be coupled to the patient by a liquid path and a movable mirror may be interposed along the liquid path to cause scanning of the beam.

Piezoelectric transducer with multiple electrode areas

Abstract: An electro-acoustic transducer comprising a flexible film of piezoelectric material, at least one electrode provided on one side of said film amd a plurality of electrodes provided on the other side of said film to form a piezoelectric diaphragm and said piezoelectric diaphragm is imparted with a locally differing resiliency and/or tension, is provided. By using this piezoelectric electro-acoustic transducer in a loudspeaker, it is possible to improve acoustic characteristics thereof particularly in a high frequency range, to obtain a variety of acoustic characteristics and to effect motional feed back to minimize distortion of reproduced sound without involving any difficulty in manufacturing or affecting proper performance of the transducer.

Sightless bubble detector

Abstract: A detector comprises a pair of electromechanical transducers for disposition on a fluid-filled conduit in an acoustically coupled relationship, an adjustable gain driving amplifier responsive to the electrical output of one transducer for driving the other transducer, an automatic gain control circuit for automatically adjusting the gain of the driving amplifier maintaining the system on the margin of oscillation, and an indicating circuit for detecting modulation of the driving signal. Bubbles passing through the conduit increase the gain required to maintain the system on the margin of oscillation, and are detected as modulations of the driving signal. In a preferred embodiment, this bubble detector is utilized as a refrigerating system test instrument.

Single transducer liquid level detector

Abstract: The presence or absence of liquid at a particular location of a tank or pipe is sensed through the wall of the container by a single ultrasonic transducer which may be secured to the outer surface of the container by hand pressure, by clamping, or by cementing. Detection is obtained through the damping effect of either liquid or air within the container on multiple interface reflections of a longitudinal sonic beam in the container wall. The first return signal amplitude adjusts the gain of the monitoring circuit and allows the measurement of the percentage decay of the return signal and the comparison of the decay to the known decay rate if the container was either empty or full at the point of measurement. Output circuits are provided to give a full or empty output signal, or to provide output control signals in response to the fluid level measurement. A fault alarm signal is also produced to indicate that the transducer is not properly coupled to the container or that the circuit is working improperly.

Combination geophone-hydrophone

Abstract: A method and apparatus for measuring and identifying up- and down-traveling waves wherein both a velocity-sensitive and pressure-sensitive transducer are disposed at a point below the earth's surface, as for example in a borehole that is refilled The pressure transducer is designed to provide intimate contact with the formation surrounding the borehole, and in addition, is the electrical equivalent of the velocity transducer

Acoustooptic modulator for optical fiber waveguides

Abstract: An acoustooptic modulator is disclosed in which light may be modulated while propagating through an optical fiber waveguide through the use of focussed acoustic waves. The modulator is formed by encircling a portion of the optical fiber waveguide in an optical communications system with an acoustic transducer. Due to the encircling of a portion of the waveguide by the transducer, the acoustic waves which are generated in the optical fiber waveguide material are focussed inwardly to the center so that the energy densities where acoustooptic modulation occurs are high. Therefore, the acoustic driving powers and modulation efficiencies are highly favorable.

Liquid-level sensor

Abstract: A method and apparatus for indicating the level of liquid in a tank or the like whereby a transducer is mounted on a pipe above the liquid for producing, in response to a trigger signal, an ultrasonic pulse which is transmitted toward and reflected to the transducer first from a calibration target in the pipe above the liquid and then from the liquid so that the transducer produces echo pulses in response to receipt thereof. In one embodiment the calibration echo signal is applied to a logic circuit together with the output of a counter which is incremented to a predetermined count following the trigger signal by pulses from a voltage controlled oscillator so that the logic produces a control signal indicating the difference in time between when the calibration echo is received and when the counter reaches its predetermined count and which event occurs first. The logic then varies the frequency of the oscillator to reduce the difference. A further counter is enabled upon receipt of the calibration echo signal to accumulate a count of pulses from the oscillator and disabled upon receipt of the liquid echo signal so that the count indicates the liquid level.

Apparatus for ultrasonic scanning

Abstract: In an illustrated embodiment an array of ultrasonic transducer elements is combined into a first transmitting surface to emit a first transmit signal, and then in alternation with blanking intervals is combined into receiving surfaces of progressively increased size for the reception of echo signals and for constructing a first image line of a first partial image. A second transmitting surface of lesser size then emits a transmit signal and further combinations of transducer elements are activated during time intervals thereafter which correspond to the blanking intervals of the first image line. Such sequential lines may form a composite line on a visual display. A planar array of transducer elements may have its successive receiving surfaces of varying size electronically focused either in the scan direction or in the layer thickness direction, or the array can have mechanical curvature to provide a desired focus in the layer direction. A circuit arrangement is preferred which simplifies the control of switching and minimizes the number of electronic focusing channels while still achieving a relatively high image frequency.

Acoustic surface wave device

Abstract: A sidestepping acoustic surface wave filter device employing a 3 dB multistrip coupler between the input transducer and the offset output transducer. A reflector is located across the track associated with the input transducer in the region adjacent to the output transducer. The 3 dB coupler causes the output transducer and the reflector to receive equal acoustic surface wave energy. The reflector is designed so that the energy reflected by it is equal to the energy returned by the output transducer. Phase shifts produced in the returning acoustic surface waves by the coupler cause the returning acoustic surface waves to be suppressed in the track associated with the input transducer. Thus, triple transit signals are avoided.

High fidelity pressure transducer

Abstract: The capacitive fluid pressure transducers described herein comprise quartz bodies and diaphragms having suitable electrodes deposited thereon to form both sensing and reference capacitors in appropriate configurations for high fidelity measurement of relative blood pressure, said transducers being substantially unaffected by temperature and other environment factors.