Showing papers on "Transducer published in 2004"

Energy harvesting using a piezoelectric "cymbal" transducer in dynamic environment

Abstract: In this study, we investigated the capability of harvesting the electrical energy from mechanical vibrations in a dynamic environment through a "cymbal" piezoelectric transducer. Targeted mechanical vibrations lie in the range of 50–150 Hz with force amplitude in the order of 1 kN (automobile engine vibration level). It was found that under such severe stress conditions the metal–ceramic composite transducer "cymbal" is a promising structure. The metal cap enhances the endurance of the ceramic to sustain high loads along with stress amplification. In this preliminary study, the experiments were performed at the frequency of 100 Hz on a cymbal with 29 mm diameter and 1 mm thickness under a force of 7.8 N. At this frequency and force level, 39 mW power was generated from a cymbal measured across a 400 kΩ resistor. A DC–DC converter was designed which allowed the transfer of 30 mW power to a low impedance load of 5 kΩ with a 2% duty cycle and at a switching frequency of 1 kHz.

Reliability and validity of a linear position transducer for measuring jump performance.

Abstract: This study determined the reliability and validity of a linear position transducer to measure jump performance by comparing the mean force, peak force, and time-to-peak force measurements with data obtained simultaneously with a force platform. Twenty-five men performed squat, countermovement, and drop jumps with the linear transducer connected from a waist belt and base, which were placed upon a force platform. The Pearson correlation coefficients across the 3 jumps for the mean force (r = 0.952-0.962), peak force (r = 0.861-0.934), and time-to-peak force (r = 0.924-0.995) were high, providing evidence that the linear-transducer and force-platform measurements were similar. The trial-to-trial reliability of the jumps measured by the linear position transducer gave an intraclass correlation coefficient of 0.924-0.975 for mean force, 0.977-0.982 for peak force, and 0.721-0.964 for time-to-peak force. The coefficients of variation were 2.1-4.5% for mean force, 2.5-8.4% for peak force, and 4.1-11.8% for time-to-peak force. Our findings showed that the calculations derived from the linear transducer were very similar to those of the force platform and hence provided evidence of the validity of this method. The data from the linear transducer were also shown to be reliable. Therefore, this method of calculating force may provide a cost-effective alternative to the force platform for measuring this variable.

Structural health monitoring using scanning laser vibrometry: II. Lamb waves for damage detection

Abstract: Guided ultrasonic waves have shown great potential for structural health monitoring. Various types of transducer can be used for actuating and sensing of these waves. This includes non-contact approaches such as optical/laser techniques. Classical laser methods usually involve high energy interferometers. The paper demonstrates that a commercial laser vibrometer, designed for vibration/modal analysis, can be used for crack detection in metallic structures. The study involves a simple fatigue test in order to initiate and grow a crack. Lamb waves generated by one bonded piezoceramic transducer were sensed using a multi-point scanning laser vibrometer. The results demonstrate the potential of laser vibrometry for simple, rapid and robust detection of fatigue cracks in metallic structures.

Multiple-bandwidth photoacoustic tomography

Abstract: Photoacoustic tomography, also referred to as optoacoustic tomography, employs short laser pulses to generate ultrasonic waves in biological tissues. The reconstructed images can be characterized by the convolution of the structure of samples, the laser pulse and the impulse response of the ultrasonic transducer used for detection. Although the laser-induced ultrasonic waves cover a wide spectral range, a single transducer can receive only part of the spectrum because of its limited bandwidth. To systematically analyse this problem, we constructed a photoacoustic tomographic system that uses multiple ultrasonic transducers simultaneously, each at a different central frequency. The photoacoustic images associated with the different transducers were compared and analysed. The system was tested by imaging both mouse brains and phantom samples. The vascular vessels in the brain were revealed by all of the transducers, but the image resolutions differed. The higher frequency detectors provided better image resolution while the lower frequency detectors delineated the major structural traits with a higher signal–noise ratio.

Component ultrasound transducer

Abstract: An ultrasound transducer having multiple focal zones is described. In one embodiment there is an ultrasound transducer manufactured as a single piece but having two or more focal zones. In a second embodiment there is a transducer assembly combining a high frequency and low frequency transducer. In a third embodiment there is an interchangeable assembly allowing for different ultrasound transducers to be used based on procedural needs. Variations of each embodiment are also disclosed.

Photoacoustic imaging with deconvolution algorithm

Abstract: The impulse response of the ultrasonic transducer used for detection is crucial for photoacoustic imaging with high resolution. We demonstrate a reconstruction method that allows the optical absorption distribution of a sample to be reconstructed without knowing the impulse response of the ultrasonic transducer. A convolution relationship between photoacoustic signals measured by an ultrasound transducer and optical absorption distribution is developed. Based on this theory, the projection of the optical absorption distribution of a sample can be obtained directly by deconvolving the recorded PA signal originating from a point source out of that from the sample. And a modified filtered back projection algorithm is used to reconstruct the optical absorption distribution. We constructed a photoacoustic imaging system to validate the reconstruction method and the experimental results demonstrated that the reconstructed images agreed well with the original phantom samples. The spatial resolution of the system reaches 0.3 mm.

Borehole telemetry system

Abstract: A telemetry apparatus and method for communicating data from a down-hole location through a borehole to the surface is described including a light source, an optical fiber being placed along the length of the wellbore and receiving light from the light source, a transducer located such as to produce a force field (eg a magnetic field) across the optical fiber and its protective hull without mechanical penetration of the hull at the down-hole location, one or more sensors for measuring down-hole conditions and/or parameters, a controller to provide a modulated signal to the magnetic field generator, said modulated signal being under operating conditions representative of measurements by the one or more sensors, and an optical detector adapted to detect changes in the light intensity or polarization of light passing through the fiber

Ultrasonic orthopedic surgical device with compound ultrasound vibration

Abstract: An orthopedic surgical device with compound ultrasound vibration that comprises a handpiece, a surgical cutter fixed on the anterior top of the handpiece, and an ultrasound signal generator. Inside the outer casing of said handpiece, there are provided: an ultrasound transducer for transforming the ultrasound signals from said ultrasound signal generator into ultrasound mechanical waves; a horn (or amplitude transformer) for amplifying vibration amplitude of ultrasound mechanical waves generated from said transducer and then transmitting the amplified ultrasound mechanical waves to said surgical cutter to lead to longitudinal vibration of the surgical cutter; a driving motor fixed in the back end of said handpiece for driving said ultrasound transducer and horn to accomplish the movement of swing and rotation; an adapter provided between said driving motor and said transducer for supplying ultrasonic electrical signals generated by said ultrasound signal generator to said ultrasound transducer.

Focused ultrasound system with adaptive anatomical aperture shaping

Abstract: A method of treating tissue within a body includes directing an ultrasound transducer having a plurality of transducer elements towards target body tissue, and delivering ultrasound energy towards the target tissue from the transducer elements such that an energy intensity at the target tissue is at or above a prescribed treatment level, while an energy intensity at tissue to be protected in the ultrasound energy path of the transducer elements is at or below a prescribed safety level.

Disposable transducer seal

Abstract: A transducer seal designed to seal an open aperture of a transducer housing for a therapeutic ultrasound procedure. The seal has a membrane, a retainer and a mating device for locking in place with the transducer housing. The membrane is essentially transparent to ultrasound energy while being stretched taut about the retainer. The transducer seal may be made in a disposable or re-usable form.

Fast photoacoustic imaging system based on 320-element linear transducer array

Abstract: A fast photoacoustic (PA) imaging system, based on a 320-transducer linear array, was developed and tested on a tissue phantom. To reconstruct a test tomographic image, 64 time-domain PA signals were acquired from a tissue phantom with embedded light-absorption targets. A signal acquisition was accomplished by utilizing 11 phase-controlled sub-arrays, each consisting of four transducers. The results show that the system can rapidly map the optical absorption of a tissue phantom and effectively detect the embedded light-absorbing target. By utilizing the multi-element linear transducer array and phase-controlled imaging algorithm, we thus can acquire PA tomography more efficiently, compared to other existing technology and algorithms. The methodology and equipment thus provide a rapid and reliable approach to PA imaging that may have potential applications in noninvasive imaging and clinic diagnosis.

Controlled inflation of voids in cellular polymer ferroelectrets: Optimizing electromechanical transducer properties

Abstract: When exposed to sufficiently high electric fields, polymer-foam electret materials with closed cells exhibit ferroelectric-like behavior and may therefore be called ferroelectrets. In cellular ferroelectrets, the influence of the cell size and shape distributions on the application-relevant properties is not yet understood. Therefore, controlled inflation experiments were carried out on cellular polypropylene films, and the resulting elastical and electromechanical parameters were determined. The elastic modulus in the thickness direction shows a minimum with a corresponding maximum in the electromechanical transducer coefficient. The resonance frequency shifts as a function of the elastic modulus and the relative density of the inflated cellular films. Therefore, the transducer properties of cellular ferroelectrets can be optimized by means of controlled inflation.

Electrical sensing apparatus and method utilizing an array of transducer elements

Abstract: Many electrical sensing devices include an array of transducer elements for converting external stimuli to electrical indications. Novel technologies to realize improvements in low power consumption, low noise, and analog output path which occupies minimal die area while maintaining certain data rates are disclosed. A two stage pipeline architecture of the invention in the analog output path maintains fast pixel rates with minimal ADC (analog digital converter) arrangement. A novel power supply and the use of differential amplifiers in connection with a black signal level as a reference voltage are also described.

Transducer for heat assisted magnetic recording

Abstract: An apparatus for concentrating electromagnetic energy comprises a metallic transducer including a first section and a second section, wherein the first section is wider than the second section and has a width to length aspect ratio greater than or equal to a width to length aspect ratio of the second section, and a condenser for directing electromagnetic radiation onto the transducer. A magnetic storage device that includes the apparatus is also provided.

Ultrasonic treatment device and ultrasonic treatment system

Abstract: An ultrasonic transducer unit that generates ultrasonic vibration for treating living tissues has an ultrasonic transducer and a cover member that covers the ultrasonic transducer. A flexible sheath is coupled at one end to the cover member. A signal cable extends through the sheath and is connected at one end to the ultrasonic transducer. A transducer drive unit is connected to the other end of the signal cable. An operation unit is provided at the other end of the flexible sheath.

Ultrasound catheter calibration system

Abstract: Apparatus is provided for calibrating a probe having a position sensor and an ultrasonic transducer. The apparatus includes a test fixture, which includes an ultrasonic target disposed therein at a known position. A computer is adapted to receive a position signal generated by the position sensor while the transducer is in alignment with the ultrasonic target, determine an orientation of the probe in a frame of reference of the test fixture, and determine calibration data for the probe responsive to the orientation of the probe.

Method and apparatus of acoustic communication for implantable medical device

Abstract: An implantable medical device includes an acoustic transducer for intra-body communication with another medical device via an acoustic couple. The acoustic transducer includes one or more piezoelectric transducers. In one embodiment, an implantable medical device housing contains a cardiac rhythm management (CRM) device and an acoustic communication circuit. The acoustic transducer is electrically connected to the acoustic communication circuit to function as an acoustic coupler and physically fastened to a wall of the implantable housing, directly or via a supporting structure.

Single proof mass, 3 axis mems transducer

Abstract: A transducer is provided herein which comprises an unbalanced proof mass (51), and which is adapted to sense acceleration in at least two mutually orthogonal directions. The proof mass (51) has first (65) and second (67) opposing sides that are of unequal mass.

Passive damping of beam vibrations through distributed electric networks and piezoelectric transducers: prototype design and experimental validation

Abstract: The aim of this work is two-fold: to design devices for passive electric damping of structural vibrations by distributed piezoelectric transducers and electric networks, and to experimentally validate the effectiveness of such a damping concept. Two different electric networks are employed, namely a purely resistive network and an inductive–resistive one. The presented devices can be considered as distributed versions of the well-known resistive and resonant shunt of a single piezoelectric transducer. The technical feasibility and damping effectiveness of the proposed novel devices are assessed through the construction of an experimental prototype. Experimental results are shown to be in very good agreement with theoretical predictions. It is proved that the presented technique allows for a substantial reduction in the inductances used when compared with those required by the single resonant shunted transducer. In particular, it is shown that the required inductance decreases when the number of piezoelectric elements is increased. The electric networks are optimized in order to reduce forced vibrations close to the first resonance frequency. Nevertheless, the damping effectiveness for higher modes is experimentally proved. As well as specific results, fundamental theoretical and experimental considerations for passive distributed vibration control are provided.

Systems and methods for determining intracranial pressure non-invasively and acoustic transducer assemblies for use in such systems

Abstract: Systems and methods for determining ICP based on parameters that can be measured using non-invasive or minimally invasive techniques are provided, wherein a non-linear relationship is used to determine ICP based on one or more variable inputs. The first variable input relates to one or more properties of a cranial blood vessel and/or blood flow, such as acoustic backscatter from an acoustic transducer having a focus trained on a cranial blood vessel, flow velocity in a cranial blood vessel, and the like. Additional variables, such as arterial blood pressure (ABP), may be used in combination with a first variable input relating to one or more properties of a cranial blood vessel, such as flow velocity of the middle cerebral artery (MCA) to derive ICP using a non-linear relationship. Methods and systems for locating target areas based on their acoustic properties and for acoustic scanning of an area, identification of a target area of interest based on acoustic properties, and automated focusing of an acoustic source and/or detector on a desired target area are also provided. Acoustic transducer assemblies are described.

Touch sensitive device employing bending wave vibration sensing and excitation transducers

Abstract: A touch sensitive apparatus includes a touch plate to which several pickup sensors and at least one excitation transducer are coupled. Each of the sensors is configured to sense bending waves in the touch plate, and the excitation transducer is configured to induce bending waves in the touch plate. The apparatus may further include active buffer circuits, wherein each of the active buffer circuits is coupled to one of the sensors. A controller is coupled to the sensors via the active buffer circuits and to the excitation transducer via a non-actively buffered connection. The controller is configured to compute a location of a contact on the touch plate responsive to sense signals received from the sensors. The apparatus may be used to perform a variety of calibrations, including touch plate and sensor calibrations. Changes in touch sensing apparatus calibration and performance may be detected and tracked over time.

Method and system for ultrasound treatment with a multi-directional transducer

Abstract: A method and system for ultrasound treatment utilizing a multi-directional transducer to facilitate treatment, such as therapy and/or imaging or other tissue parameter monitoring, in two or more directions. In accordance with an exemplary embodiment, a multi-directional transducer comprises at least two transduction elements configured to provide for ultrasound energy, such as radiation, acoustical energy, heat energy, imaging, positional information and/or tissue parameter monitoring signals in two or more directions. The transduction elements can comprise various materials for providing ultrasound energy or radiation, such as piezoelectric materials, with and without matching layers. In addition, the transduction elements can be configured for substantially uniform, focused and/or defocused radiation patterns, as well as for single, multiple-element and/or multiple-element array configurations. In addition, an exemplary multi-directional transducer can comprise multiple elements, either side by side, stacked or in an array.

Externally-applied high intensity focused ultrasound (HIFU) for pulmonary vein isolation

Abstract: Apparatus is provided for performing ablation of cardiac tissue using ultrasound. The apparatus includes a beacon, adapted to be placed at a cardiac site in a body of a subject. The apparatus further includes a set of ultrasound transducers, each transducer adapted to detect a respective ultrasound signal coming from the beacon. Each transducer is adapted to output a time-reversed ultrasound signal, reversed in time with respect to a property of at least one of the beacon signals, and configured to ablate the cardiac tissue.

Adaptive multi-mode resonant piezoelectric shunt damping

Abstract: Multiple-modes of structural vibration can be suppressed through the connection of an electrical impedance to the terminals of a bonded piezoelectric transducer. The so-called resonant shunts, one commonly used class of shunt impedances, provide good nominal damping performance but they are highly sensitive to variations in transducer capacitance and structural resonance frequencies. This paper introduces a new technique for the online adaptation of multi-mode resonant shunts. By minimizing the relative phase difference between a vibration reference signal and the shunt current, circuit component values can be optimally tuned online. Experiments on a cantilever beam validate the proposed technique and demonstrate the simplicity of implementation. The adaptive law converges quickly and maintains optimal performance in the presence of environmental uncertainties.

Knitted transducer devices

Abstract: There is disclosed a knitted transducer device (10) comprising a knitted structure having at least one transduction zone, in which the transduction zone is knitted with electrically conductive fibres so that deformation of the knitted structure results in a variation of an electrical property of the transduction zone. Disclosed is also a garment such a unitted transducer.

Acoustic wave touch detection circuit and method

Abstract: A circuit for an acoustic wave switch or sensor having a resonant acoustic wave cavity detects a touch or sensed event using a time domain approach. The circuit includes a controller that drives an acoustic wave transducer to generate a resonant acoustic wave in the acoustic wave cavity during a first portion of a sampling cycle. In a second portion of the sampling cycle, the controller monitors the time that it takes for the acoustic wave signal from the transducer to decay to a predetermined level. Based on the decay time, the controller detects a sensed event, such as a touch on the acoustic wave switch/sensor.

Optoacoustic imaging with synthetic aperture focusing and coherence weighting.

Abstract: Optoacoustic imaging takes advantage of high optical contrast and low acoustic scattering and has found several biomedical applications. In the common backward mode a laser beam illuminates the image object, and an acoustic transducer located on the same side as the laser beam detects the optoacoustic signal produced by thermoelastic effects. A cross-sectional image is formed by laterally scanning the laser beam and the transducer. Although the laser beam width is generally narrow to provide good lateral resolution, strong optical scattering in tissue broadens the optical illumination pattern and thus degrades the lateral resolution. To solve this problem, a combination of the synthetic aperture focusing technique with coherence weighting is proposed. This method synthesizes a large aperture by summing properly delayed signals received at different positions. The focusing quality is further improved by using the signal coherence as an image quality index. A phantom comprising hair threads in a 1% milk solution was imaged with an optoacoustic imaging system. The results show that the proposed technique improved lateral resolution by 400-800% and the signal-to-noise ratio by 7-23 dB over conventional techniques.

Endo-cavity focused ultrasound transducer

Abstract: An apparatus for delivering acoustic energy to a target site adjacent a body passage includes first and second elongate members, each carrying one or more transducer elements on their distal ends. The first and/or second elongate members include connectors for securing the first and second elongate members together such that the transducer elements together define a transducer array. The first and second elongate members are introduced sequentially into a body passage until the transducer elements are disposed adjacent a target site. Acoustic energy is delivered from the transducer elements to the target site to treat tissue therein. In another embodiment, the apparatus includes a tubular member and an expandable structure carrying a plurality of transducer elements. The structure is expanded between a contracted configuration during delivery and an enlarged configuration when deployed for delivering acoustic energy to a target site adjacent the body passage.

Wave energy converters utilizing pressure differences

Abstract: An elongated cylinder is fully submerged, in vertical orientation, just below the mean water level of, e.g., and ocean, and of a length, dependent upon surface waves of preselected wavelength, such that the top of the cylinder experiences relatively large pressure variations in response to over passing waves while the bottom of the cylinder experiences an almost steady pressure substantially independent of the over passing waves. The pressure differential over the length of the cylinder is used for causing relative movements between the cylinder and adjoining water, and such relative movements are used for driving a piston of an energy converter. The cylinder can be hollow and in fixed location for causing water movements through the cylinder, or the cylinder can move through the water relative to a fixed transducer. In one version of the movable cylinder, the transducer is fixedly mounted on a fixed in place float disposed within the movable cylinder. In a second version, the transducer is fixedly mounted beneath the movable cylinder on the ocean floor, and the cylinder is coupled to the transducer.