Showing papers on "Transducer published in 1979"

Electronic damping of vibrations in optical structures.

Abstract: We have carried out a preliminary experimental demonstration of the feasibility of using external electronic circuits to damp mechanical vibrations in optical systems. The significance of the feasibility demonstration is that substantial levels of vibrational amplitude reduction were obtained with very small transducers in nonoptimal positions on noncritical portions of the optical structure. The prototype optical structure used in the experiment consisted of a membrane mirror stretched over a 25-cm diam glass frame with complex cross section. Five small piezoelectric transducers (19.05 x 3.18 x 0.28 mm) were applied with Duco cement at arbitrary positions on the glass frame. Acoustic excitation was then used to excite the resonances in the optical structure. These vibrational responses were measured, and one particular mode was chosen for the feasibility test. The structure was driven by external vibrations at the resonant frequency of the chosen mode until the membrane response was visible. One transducer as used to sense the vibrations in the frame, and this output was used to drive a negative feedback amplifier that drove one of the other transducers on the frame. With the feedback circuit active between two points on the frame, the vibrational response of the membrane to the external excitation was substantially reduced (7:1).

Fiber optic lever displacement transducer.

Abstract: Intrinsic performance limits of noncontacting fiber lever displacement measuring systems are quantitatively described. Generalized relationships linking displacement detection limit, frequency response, dynamic range, linearity, and working distance to fiber diameter, illumination irradiance and coupling angle, photo-detector characteristics, and reflection and transmission losses were obtained by analysis and confirmed by measurement. Both procedures showed performance limits to be functions of the square root of the flux density coupled into the target-illuminating fiber(s) by the electroluminescent source. Displacement detection and bandwidth limits achievable with tungsten or LED sources were in the 2 × 10−11 to 2×10-12m/Hz and MHz, range respectively. A basis for optimizing levers for different applications and determination of intrinsic performance limits is provided.

Subcutaneous neural stimulation or local tissue destruction

Abstract: A method of generating a high energy density at any point in the body, noninvasively, by two high frequency sonic beams creating a low frequency beating pattern at their intersection locus. One method provides for two transducers at different angular positions. Each transducer produces a beam pattern of high frequency. One transducer produces a high frequency which is higher by a predetermined quantity than the other. At their point of intersection, the sonic oscillations add and subtract, producing a low frequency beat equal to the predetermined quantity. This high energy low frequency beat can be used to stimulate neural points in the skull or other parts of the body or for tissue destruction. In a related method, the high frequency beams are set in axial alignment so that the frequency generating output is fixed between the transducers. A master modulator can then be used to electronically vary the position of the intersecting locus along the axial line connecting the transducers.

Guided-wave acoustooptic Bragg modulators for wide-band integrated optic communications and signal processing (Invited Paper)

Abstract: This paper presents a selective review of planar guided-wave acoustooptics, including some of the most recent results. The emphasis is on those aspects which relate to wide-band multichannel optical communications and real-time signal processing. First to be discussed are the analytical and numerical techniques required for the treatment of a Bragg modulator which uses a single aperture SAW transducer. The frequency responses generated for Y -cut LiNbO_3 waveguides using a digital computer serve as the basic data for the design of such a basic modulator. Next the key device parameters relevant to modulation and signal processing are discussed. The design parameters and procedures for wide-band Bragg modulators and deflectors are then established. Finally, some potential applications of such wide-band modulators and deflectors in optical communications and RF signal processing together with the best measured performance figures are described.

Method for detecting air emboli in the blood in an intracorporeal blood vessel

Abstract: A system for detecting and quantifying air emboli in blood vessels which uses either an intravascular catheter 22 or an esophageal catheter 50. In a preferred embodiment, the intravascular catheter includes an elongated cylindrical tube of flexible material, the tube having a tip 22A and having formed therein an axial aspiration lumen 26 and a second axial lumen 28. An ultrasonic transducer 24, comprising an annular, cylindrical ring of piezoelectric material, is fitted over and secured to the tube adjacent its tip. A microcoaxial cable passes through lumen 28 and is electrically interconnected with the ultrasonic transducer. In a preferred embodiment, the esophageal catheter includes a substantially cylindrical member 54 on which is fitted an ultrasonic transducer 52 comprising an annular, cylindrical ring of piezoelectric material. An elongated tube 58 is secured to the substantially cylindrical member, and a microcoaxial cable 62 passes through tube 58 and the substantially cylindrical member and is electrically connected to the ultrasonic transducer. In use, the intravascular catheter is positioned within a desired blood vessel after percutaneous insertion, and the esophageal catheter is positioned within the esophagus below the bifurcation of the trachea. A pulsed Doppler circuit (FIG. 9) energizes the transducer and provides a Doppler signal from return signals generated by the transducer as a result of returns of transmitted ultrasonic energy. A circuit (FIGS. 10 and 11) processes the Doppler signal to obtain various information useful in the diagnosis of air emboli.

Ultrasound needle tip localization system

Abstract: A B-scan pulse echo ultrasound system produces a real time image of a body area under inquiry, and an aspiration needle is inserted directly into that area. The needle carries a small, omni-directional ultrasound transducer, electrically connected through the needle to transponder electronics. Incident pulses from the imaging transducer to the omni-directional transducer are sensed at the latter, and the position thereof is inserted into the image either by generation of a return signal from the needle point, or through delay logic and subsequent production of a composite.

Welding helmet lens assembly

Abstract: A protective welding lens assembly for use as the eyepiece of a welding helmet in which the lens assembly can be changed from a light-transmitting condition to an essentially opaque condition of very small light transmission, and vice versa, in response to an electrical signal and wherein the electrical signal for changing the light-transmitting characteristics of the lens assembly is controlled by energy emanating from the mouth of the user of the welding helmet. Preferably, the lens assembly comprises a liquid crystal light shutter; however any lens assembly can be used which can be electrically actuated to change its light-transmitting characteristics. A transducer is disposed within the welding helmet so as to be in front of the mouth of the welder when the helmet is positioned over his face. The transducer can comprise either a microphone responsive to sound from the welder's mouth or a pressure transducer responsive to blowing from the welder's mouth. An electrical signal generated by the transducer is then used to control the light-transmitting characteristics of the lens assembly.

Focusing piezoelectric ultrasonic medical diagnostic system

Abstract: There is disclosed an ultrasonic piezoelectric transducer consisting of two separate transducer elements bonded together. The individual elements may be similar or different in size, thickness, and/or material. The material which bonds the two elements together may serve as one electrode, and two other electrodes coat the outer surfaces of the two individual elements. By switching the electrodes which are connected to the transmit and receive circuits of an ultrasonic medical scanning apparatus, the single transducer may be used for imaging with high resolution at one frequency, and for pulse Doppler velocity measurements at a different frequency. The two elements may be driven individually or in combination, in order to achieve different operating frequencies and focusings.

Implantable calibration means and calibration method for an implantable body transducer

Abstract: An implantable body transducer having a self-contained calibration means. An exemplary embodiment comprises an implantable body pressure measuring transducer utilizing an L-C oscillator having a resonant circuit comprising a fixed L and a variable C, the variable C having a fixed capacitive electrode and a movable capacitive electrode in the form of a stiff pressure responsive diaphragm, the output frequency of the oscillator being a function of the pressure sensed by the diaphragm. The transducer incorporates a self-contained calibration means which contains predetermined calibration data with respect to the variable C. The predetermined calibration data is stored in a plurality of PROM storage elements which are sequentially addressed in accordance with the output of a counter, the PROM storage elements providing a serial bit stream which can be used to pulse-code modulate the L-C resonant circuit output. Specific calibration parameters for the variable C are determined during manufacture of the pressure measuring transducer. These parameters are programmed into the digital storage elements of the PROM, burned in, and then utilized to modulate the resonant circuit output subsequent to implantation in a body. In addition, a means is disclosed whereby other parameter measuring transducer outputs, such as a temperature, can be utilized through appropriate circuitry to modulate the output of the implantable body transducer.

Broadband Integrated Backscatter: An Approach to Spatially Localized Tissue Characterization in Vivo

Abstract: interest. The backscattered echo train is detected by the same transducer that launcheo the interrogating pulse. The received signal is electronically gated, with the result that the v olumeofthe sample under investigation is defined by the duration of ;:Ei$:: ~:dm~~~u~~3~:~ni ~h~e~~t~~~t~fa~h ~h~ate is then Fourier transformed to examine the frequency domain characteristics of the s cattered signal. The result of this analysis is given by the expression As an approach to quantitative u ltrasonic backscatter measurements for regional tissue characterization in vivo, we investigatedthefrequency average of the backscatter transfer function over the bandwidth of the insonifying transducer, denoted the i ntegrated backscatter. The results of measurements conducted on excised dog myocardium indicate that the frequency averaging properties of the integrated backscatter substantially reduce spatial variation in the measured scattering sample. The potential of this index for tissue characterization in vivo was tested using an where V(f) is the output of the transducer, P(f) is open-chest dog model. Myocardial ischemia was the transfer function associated with the transducer induced in 7 dogs by coronary artery occlusion. characteristics at the measurement position and the

Excitation of horizontally polarized shear elastic waves by electromagnetic transducers with periodic permanent magnets

Abstract: Theoretical and experimental results obtained with a new type of noncontact electromagnetic transducer are presented. The transducer differs from previous configurations in that a periodic permanent magnet and an axially wound coil are combined to produce a transversely directed periodic surface stress. It is demonstrated that this configuration can be used to generate horizontally polarized shear waves traveling along, or at a predetermined angle to, the surface of a thick metal object, horizontally polarized shear modes of a thin plate, or torsional waves in a tube. A model is presented for the radiation resistance of the transducer in semi‐infinite samples and plates and supporting experiments are reported. Some advantages of this transducer in ultrasonic nondestructive evaluation of structural materials are summarized.

Constant amplitude controller and method

Abstract: There is disclosed a constant amplitude controller with feedback control for a vibratory feeder apparatus wherein a controlled rectifier is used to rectify the A.C. line voltage applied to the feeder solenoid and to control the voltage to the feeder solenoid. Triggering of the controlled rectifier is accomplished by a bias control signal which is composed of an A.C. phase shift voltage superpositioned by a variable D.C. bias voltage. Mechanical coupling is provided between the solenoid and a transducer which provides feedback to control logic circuitry. In the control logic circuitry, the signal received from the transducer is compared with a signal received from an operator adjusted potentiometer. In this manner, the desired amplitude of the vibrator apparatus is compared with the actual amplitude of the vibrator apparatus and, if there is a discrepancy, the control logic circuitry modifies the amount of control voltage being transferred by the controlled rectifier.

A system for evaluating auditory function from 8000–20 000 Hz

Abstract: A system for the measurement of auditory function from 8000–20 000 Hz is described. This system introduces advances in: (a) maximum power output, (b) signal fidelity, and (c) transducer characteristics. Two case studies are presented to illustrate the clinical information gained from the measurement of high‐frequency auditory sensitivity, which is not readily apparent in conventional threshold assessment.

Integrated silicon-PVF 2 acoustic transducer arrays

Abstract: A new type of transducer array has been designed which employs a piezoelectric polymer, polyvinylidene fluoride (PVF 2 ), as the sensing material. Acoustic properties possessed by this piezoelectric polymer provide a reasonable match to those of the human body making it very attractive for medical ultrasonic imaging systems. Using planar integrated-circuit (IC) technology, an array of MOSFET input amplifiers is fabricated on a silicon wafer. A single sheet of PVF 2 is bonded to the surface of the wafer. Spatially varying acoustic signals detected by the PVF 2 are converted to corresponding charge distributions on the underlying array of amplifiers. A linear 34-element receiving transducer array has been built and evaulated. Array transverse dimensions are 14.7 × 9 mm, so that the silicon die area is approximately 1.32 cm2. Individual transducers are 0.42 × 9 mm corresponding to the requirements of a particular system. Associated with each of the 34 transducers is a DMOS-bipolar cascode amplifier. Experimentally measured transducer impulse response decays 20 dB in two cycles. Using silicon technology, arrays of almost arbitrary size and complexity appear feasible.

Media compatible pressure transducer

Abstract: There is disclosed an absolute pressure transducer which is adaptable for use in various deleterious mediums. A single wafer contains a gage sensor configuration on one portion and an absolute sensor configuration on another adjacent portion. An active diaphragm area is defined for each sensor configuration by forming a depression beneath the sensor locations. A base member is bonded or secured to the wafer at the side containing the depressions. An aperture is directed through the base member to communicate with the depression associated with the gage sensor configuration and is employed as an external pressure port. The top surface of the wafer which contains the sensors is exposed to a relatively clean source of pressure to thereby enable the absolute sensor section to monitor this pressure, while the gage sensor section responds to both pressures.

A technique for measuring frequency response of pressure, volume, and flow transducers

Abstract: A device and methodology is presented for testing the frequency response of pressure, volume, or flow transducers. Also reported are responses of selected transducers of all three types over the range of 2--120 Hz. Several pressure transducers tested had good frequency response when connected to the test system with a minimum of interconnecting fittings; others did not. Use of additional connectors degraded the response as did the addition of air-filled catheters. The frequency response of the pneumotachometers tested were influenced largely by the response characteristics of the associated pressure transducer and interconnecting fittings. These results emphasize the need to test the response characteristics of any transducer with specific connectors and fittings that are to be used to make the actual measurements of pressure, volume, or flow.

Endoscopic method & apparatus including ultrasonic B-scan imaging

Abstract: Endoscopic method and apparatus are provided for the simultaneous visual and ultrasonic imaging of internal body parts through use of a probe insertable into a body cavity. The probe includes a rectilinear transducer array acoustically coupled to the body through a cylindrical focusing lens having an outer face which conforms to the probe contour. The transducer array is included in a pulsed ultrasonic imaging system of the B-scan type. A tube, which includes a flexible portion adjacent the probe, connects the probe to a control housing containing manually operated control mechanism for bending the flexible tube portion. A control handle extends from the side of the housing for control of bending by the operator. The pulsed ultrasonic imaging system includes pulse generator and pulse receiver means connected to individual elements of the transducer array by coaxial cables extending through the tube. Electronic beam focusing and scanning means for rectilinear B-scan operation are provided for imaging of objects at close distances adjacent the probe. Visual display means are provided for visual display of the ultrasonic image from the B-scan receiver. An optical illuminating and viewing system is provided for optically viewing internal body parts through the probe, which system includes an objective lens and illuminating means adjacent the distal ends of the probe and transducer array. A removable eyepiece at the housing is used for direct viewing by the operator while guiding the probe into desired position in the body cavity. Means also are provided for viewing the optical image by a video camera having an output connected to a monitor adjacent the ultrasonic image display. Consequently, both the optical and ultrasonic images are simultaneously displayable and viewable by the operator.

Image recording system

Abstract: An image recording system in which an object image is caused to be formed on a solid state image transducer such as CCD each time a release is actuated, and the image signal stored on said image transducer is recorded as a video signal, thus a single frame image being recorded for each release. By controlling the storing operation of the image signal and the like, the exposure level for the image signal is adjusted to make it possible to record and reproduce the image always with regard to an optimum exposure state.

Miniature quartz resonator force transducer

Abstract: The invention relates to a piezoelectric quartz force transducer having the shape of a double-ended tuning fork.

Low tire warning system

Abstract: An abnormal tire profile indicating system comprising a telemetry unit mounted on each wheel of a vehicle and a central receiver. Each telemetry unit comprises a piezoelectric transducer which is deflected with each wheel revolution when the tire profile is low. Deflecting the transducer produces an electric pulse. The transducer pulses are accumulated on a charge storage capacitor to provide a power supply. When the level of charge on the capacitor reaches a predetermined level, a counter commences counting the transducer pulses. When a predetermined number of pulses are counted, the counter renders a transistor conductive, which transistor connects the power supply capacitor to an encoder and a transmitter. The encoder produces encoded signals and resets the counter after a predetermined number of encoder signals are produced. The central receiver receives the modulated radio signals from each of the telemetry units. The counter limits the transmitter to transmitting only after a sufficient number of low profiles are detected to assure reliable operation and only after a sufficient number of wheel revolutions to meet FCC periodicity of transmission requirements. The reset counter limits the duration of transmissions to meet FCC requirements.

Optical sensor system

Abstract: An optical transducer with an optical waveguide having two paths for the propagation of light is deformed in response to acoustical pressure variations or other parameters to be sensed to modulate the amplitude of the light propagated along the two paths in opposite polarities. The light outputs of the two paths are sensed by photodetectors and applied to an electrical differencing circuit. The mean values of the photodetector outputs are balanced as by mechanically providing a predetermined bias deformation of the fiber, or by electrically matching outputs of the detectors such that, on the average, the output of the differencing circuit is zero. Dynamic deformation of the fiber in the transducer results in unbalanced outputs of the photodetectors which unbalance is sensed by the differencing circuit. This differential detection method minimizes optical and mechanical sources of noise in the light source and waveguide and leads to increased signal-to-noise and enhanced dynamic range of the transducer.

Curved array of sequenced ultrasound transducers

Abstract: An array of ultrasound transducers for pulsed sector-scan operation includes a plurality of transducer elements disposed on an arc of a circle and oriented to emit and receive ultrasound radiation in the direction of the center of the arc. A group of adjacent transducers within the array is active for each ultrasound pulse. The position of the group in the array is incrementally shifted along the arc, one transducer at a time, to effect scanning. The inherent focussing effect of a curved group of transducers is compensated with time delays or a negative lens to provide a parallel, sector-scanned radiation beam.

Frequency adaptive, power-energy re-scheduler

Abstract: A frequency adaptive, power-energy re-scheduler (FAPER) that includes a frequency transducer that notes frequency or frequency deviations of an electrical system and logic means which controls and re-schedules power flow to a load unit in part on the basis of the deviations in frequency from a nominal frequency and in part on the needs to the load unit as expressed by an external sensor signal obtained from the physical system affected by the load unit

Electronically focused ultrasonic transmitter

Abstract: An array of transducer segments is arranged in columns, each of which has a multiplicity of segments. The segments are wired to permit excitation by one or the other of two opposite phases of high-frequency signal, and groups of segments can be excited with the same phase to approximate the shape of an annular-ring phase-reversal zone plate. By changing the groupings of the elements that are similarly excited, the position of the focal region produced by the zone plate is translated in lateral position. A ferrite-core transformer is conveniently employed for both phase splitting and addition of the echo signals received by the device.

Electrical power generating system

Abstract: An electrical power generating system is disclosed which utilizes as a source of energy the otherwise wasted energy expended by motor vehicles moving along a roadway The system includes a vibrational transducer which is mounted in the roadway and which is constructed for producing electrical energy directly from the vibrational energy imparted to the transducer from the motor vehicles passing thereacross The electrical energy thus produced may be used to charge a storage battery for powering various devices, such as traffic signals, warning devices, and the like

Semiconductor device for the reproduction of acoustic signals

Abstract: A microphone, for receiving an acoustic signal, is connected to a transducer which changes the analog signal delivered by the microphone into a sufficiently dense series of storable pulses in such a manner that the series contains the information necessary for the reproduction of the analog signal. The pulses delivered by the transducer can be pulse amplitude modulated (PAM) signals. The transducer must be connected to an analog memory. In the case where the signals are digital, such as pulse code modulated (PCM) signals, a digital memory is used. For reproduction, the pulses recalled from memory, in the first case, are fed via a low pass filter to an amplifier and a loud speaker. In the second case, the pulses are first converted into an analog form in a digital/analog converter. Stacked-gate injection metal-oxide-semiconductor (SIMOS) memories may be considered as the analog memories and, as digital memories, electrically alterable read-only memories (EAROM) may be utilized.

High speed capacitance apparatus for classifying pharmaceutical capsules

Abstract: A dielectric tube, such as glass or plastic, having a square cross section extends between the two plates of a capacitance-sensing transducer. The opposite sides of the tube have a spacing only slightly greater than the diameter of the capsules to be checked. The capsules to be classified are oriented prior to their introduction into the tube so that they enter in an end-to-end relationship. The requisite spacing between the capsules is accomplished by an air jet device that rapidly accelerates the leading capsule as it enters the tube to such a velocity that it leaves the transducer before the next capsule enters, thereby assuring that only one capsule is in the transducer at any given moment. The capacitance-sensing transducer is repeatedly charged and discharged by means of a high frequency oscillator circuit. Capacitance variations from capsule to capsule are measured on a continuous analog basis and logic signals derived from such analog signals are used to determine whether a given capsule should be accepted or rejected. A reject mechanism diverts each bad capsule from the stream of acceptable or good capsules.