Abstract: The present invention is directed to a method/system of for monitoring tissue properties in real time during treatment using optoacoustic imaging system. Optoacoustic monitoring provides a control of the extent of abnormal tissue damage and assures minimal damage to surrounding normal tissues. Such technique can be applied for monitoring and controlling during surgical, therapeutic, and cosmetic procedures performed in various tissues and organs.

Abstract: A multi-dimensional beamforming device that performs consecutive one-dimensional operations. For example, beamsteering for a two-dimensional array can be include a projection of a beam onto each of the respective axes of the array. In such a device, a first beamforming processing element is used to form multiple beams for each array output along a given row. In a preferred embodiment, sequential output vectors from the first processing element are then applied to a transposing or corner turning memory and the data are reformatted such that all elements on a given column of the array are applied to a second beam forming processing element.

Abstract: A system for detecting an object of interest through a medium such as the atmosphere or ocean employs a reference object from which a reference signal emanates. A detector detects and transforms the reference signal into a transformed reference signal and further detects and transforms an object signal emanating from an object of interest into a transformed object signal. The object signal may be radiated, re-radiated, or scattered from the object of interest. An image processor generates a corrected image signal by applying an image transfer function to convolve the transformed object signal. Then a display presents a corrected image of the object of interest in response to receiving the corrected image signal.

Abstract: A method for imaging a target includes the steps of transmitting ultrasonic energy at a fundamental frequency and receiving reflected ultrasonic energy at a harmonic of the fundamental frequency. The ultrasonic energy is transmitted in power bursts, each having a respective envelope shape, wherein the envelope shapes rise gradually to a respective maximum value and fall gradually from the respective maximum value. Ultrasonic energy in the transmit beam is focused in an elongated high power region, as for example by means of a line focus.

Abstract: An ATM is provided with a loudspeaker and a microphone. The loudspeaker generates white noise which is picked up by the microphone. The detected signal constitutes an acoustic signature which changes if the ATM is tampered with, for example by inserting some fraudulent mechanism into the ATM to intercept banknotes before they reach the output slot of the ATM. If any such change is detected then an alarm can be raised.

Abstract: A method for imaging a target includes the steps of transmitting ultrasonic energy at a fundamental frequency and receiving reflected ultrasonic energy at a harmonic of the fundamental frequency. The ultrasonic energy is transmitted in power bursts, each having a respective envelope shape, wherein the envelope shapes rise gradually to a respective maximum value and fall gradually from the respective maximum value. Ultrasonic energy in the transmit beam is focused in an elongated high power region, as for example by means of a line focus.

Abstract: New apodization functions providing an effective rejection of side lobe amplitude level within wide range of beam steering angles are described in this invention. A central amplitude apodization function (13) reduces amplitudes for the central section of transmit and receive array individual elements. A time apodization function (14) changes a duration of transmit pulses. A duration of transmit pulses is short for central section of transmit array and increases for outlying transmit individual elements. A frequency apodization function (15) changes frequency of transmit pulses for different transmit individual elements. The use of new apodization function allows realization of portable acoustic scanners. Some versions of a portable acoustic scanner design and a version with time compression of echo signals are described.

Abstract: An apparatus and method for imaging uses a transducer array which receives a scattered signal from a region of interest. The method analyses the scattered signal on the basis of a model which assumes several independent point scatterers at each range. The method determines the amplitudes and angles of arrival for the several scatterers. The method provides much higher resolution than is possible with conventional beam formed sonar arrays of practical size. The method is capable of resolving features which cannot be resolved by conventional sidescan sonar or interferometric side scan sonar. The method may be used with electromagnetic or acoustic scattering signals.

Abstract: A transmit beamformer includes multiple transducers, each responsive to a respective transmit waveform to produce a respective transducer waveform. A transmit waveform generator generates the transmit waveforms, and the transmit waveforms each include multiple frequency components. Progressively higher frequency components of the transmit waveforms are timed to cause corresponding progressively higher frequency components of the transducer waveforms to focus along a line at progressively shorter ranges. In this way, a frequency dependent line focus is achieved.

Abstract: A multi-dimensional beamforming device that performs consecutive one-dimensional operations. For example, beamsteering for a two-dimensional array can be include a projection of a beam onto each of the respective axes of the array. In such a device, a first beamforming processing element is used to form multiple beams for each array output along a given row. In a preferred embodiment, sequential output vectors from the first processing element are then applied to a transposing or corner turning memory and the data are reformatted such that all elements on a given column of the array are applied to a second beam forming processing element.

Abstract: A transmit beamformer includes multiple transducers, each responsive to a respective transmit waveform to produce a respective transducer waveform. A transmit waveform generator generates the transmit waveforms, and the transmit waveform each include multiple frequency components. Progressively higher frequency components of the transmit waveform are timed to cause corresponding progressively higher frequency components of the transducer waveforms to focus along a line at progressively shorter ranges. In this way, a frequency dependent line focus is achieved.

Abstract: A method and system for ultrasonically imaging a target with energy spreading transmissions is provided. Simultaneous and sequential compound point, line and combination point and line focusing is used with harmonic receive processing. Ultrasonic energy focused at multiple depths is transmitted at the target. The target may or may not include contrast agents. In either case, echoes of the transmissions at one or more fundamental center frequencies are received at harmonics of the fundamental frequencies.

Abstract: A digital transmit beamformer system with multiple beam transmit capability has a plurality of multi-channel transmitters, each channel with a source of sampled, complex-valued initial waveform information representative of the ultimate desired waveform to be applied to one or more corresponding transducer elements for each beam. Each multi-channel transmitter applies beamformation delays and apodization to each channel's respective initial waveform information digitally, digitally modulates the information by a carrier frequency, and interpolates the information to the DAC sample rate for conversion to an analog signal and application to the associated transducer element(s). The beamformer transmitters can be programmed per channel and per beam with carrier frequency, delay, apodization and calibration values. For pulsed wave operation, pulse waveform parameters can be specified to the beamformer transmitters on a per firing basis, without degrading the scan frame rate to non-useful diagnostic levels.

Abstract: A feature imaging and adaptive focusing synthetic aperture processing met provides improved sharpness and easier classification of images derived from radar and sonar echo data by applying adaptive focusing and feature imaging to a sequence of echo data.

Abstract: A process for selective graphic representation and/or evaluation of the Doppler spectrum of objects limitedly resistant to sonic intensity, for example biological organs and tissues, by an ultrasonic process wherein a material is introduced in the examination area to be acoustically irradiated, nonlinear oscillations are produced in the examination area by irradiated ultrasonic waves and the signal is evaluated by an ultrasonic converter. Also, a circuit for carrying out the above process is disclosed.

Abstract: To achieve a high resolution, by modifying a delay time distribution of received waves with correlation computations between signals from adjacent elements and by removing influences of inhomogeneities in a living body with a simple computing circuit for correlation factors.

Abstract: Method and apparatus for the conversion of sound waves to electromagnetic wave forms, preferably light, whereby sound waves are converted to an electrical signal and processed by a number of filters, the distribution between the filters being a result of the frequency of the sound wave and in which the filters are subsequently connected to their respective color display and where the individual color display's activation is directly proportional to their filter's amount of signal processing and where the color display visualization in a display means is in the form of a single color or a mixture of two or more color displays.

Abstract: Automatic focusing of radar or sonar imaging systems, for example, synthetic aperture radar (SAR) or synthetic aperture sonar (SAS) systems, is accomplished by using high order measurements, such as the quadruple product of the range compressed signal g(x). The phase error is estimated by a recursive or non-recursive algorithm from the phase of the quadruple product. The estimated phase error is applied to the range-compressed SAR or SAS image data which is then azimuth compressed to obtain the focused image data.

Abstract: A process for selective graphic representation and/or evaluation of the Doppler spectrum of objects limitedly resistant to sonic intensity, for example biological organs and tissues, by an ultrasonic process wherein a material is introduced in the examination area to be acoustically irradiated, nonlinear oscillations are produced in the examination area by irradiated ultrasonic waves and the signal is evaluated by an ultrasonic converter. Also, a circuit for carrying out the above process is disclosed.

Abstract: A Petragrid method and apparatus generates grid cell property information that is adapted for use by a computer simulation apparatus which simulates properties of an earth formation located near one or more wellbores. An interpretation workstation includes at least two software programs stored therein: a first program called "Petragrid" and a second simulation program which is responsive to output data produced from the first "Petragrid" program for generating a set of simulation results. The set of simulation results are displayed on a workstation display monitor of the workstation. The first Petragrid software program will: receive well log and seismic data which indicates the location of each layer of a formation near a wellbore, and then grid each layer of the formation, the grid being comprised of a plurality of cells. The first Petragrid software will then generate more accurate data associated with each cell, such as the transmissibility of well fluid through each cell.

Abstract: A method for imaging a target includes the steps of transmitting ultrasonic energy at a fundamental frequency and receiving reflected ultrasonic energy at a harmonic of the fundamental frequency. The ultrasonic energy is transmitted in power bursts, each having a respective envelope shape, wherein the envelope shapes rise gradually to a respective maximum value and fall gradually from the respective maximum value. Ultrasonic energy in the transmit beam is focused in an elongated high power region, as for example by means of a line focus.

Abstract: A digital transmit beamformer system with multiple beam transmit capability has a plurality of multi-channel transmitters, each channel with a source of sampled, complex-valued initial waveform information representative of the ultimate desired waveform to be applied to one or more corresponding transducer elements for each beam. Each multi-channel transmitter applies beamformation delays and apodization to each channel's respective initial waveform information digitally, digitally modulates the information by a carrier frequency, and interpolates the information to the DAC sample rate for conversion to an analog signal and application to the associated transducer element(s). The beamformer transmitters can be programmed per channel and per beam with carrier frequency, delay, apodization and calibration values. For pulsed wave operation, pulse waveform parameters can be specified to the beamformer transmitters on a per firing basis, without degrading the scan frame rate to non-useful diagnostic levels.

Abstract: An optoacoustic system comprises an optoacoustic transducer including a first array of acoustic transducers and a second array of optical fibers; an acoustic subsystem for controllably exciting at least a first subset of the acoustic transducers to generate acoustic pulses with a prescribed pulse width, and for forming a first image based on return acoustic pulses reflected from a patient; an optical subsystem for controllably generating optical pulses to be transmitted through at least a first subset of the optical fibers toward the patient, and for forming a second image based on light reflected from the patient; and image correlation means for correlating the first and second images. The first and second arrays may take various forms, including the form of an annular array in which the acoustic transducers are arranged coaxially and the optical fibers are disposed around an outer periphery of the first array. The first and second arrays may also take the form of linear arrays.

Abstract: An apparatus is provided in which a phased transmitting array (21) is arranged to irradiate a selected voxel within a search volume. Energy reflected from the voxel is received by a further antenna and the signals received from a plurality of voxels are analysed to search for reflectors or discontinuities within the search space.

Abstract: A transmit beamformer includes multiple transducers, each responsive to a respective transmit waveform to produce a respective transducer waveform. A transmit waveform generator generates the transmit waveforms, and the transmit waveforms each include multiple frequency components. Progressively higher frequency components of the transmit waveforms are timed to cause corresponding progressively higher frequency components of the transducer waveforms to focus along a line at progressively shorter ranges. In this way, a frequency dependent line focus is achieved.

Abstract: A digital transmit beamformer system with multiple beam transmit capability has a plurality of multi-channel transmitters, each channel with a source of sampled, complex-valued initial waveform information representative of the ultimate desired waveform to be applied to one or more corresponding transducer elements for each beam. Each multi-channel transmitter applies beamformation delays and apodization to each channel's respective initial waveform information digitally, digitally modulates the information by a carrier frequency, and interpolates the information to the DAC sample rate for conversion to an analog signal and application to the associated transducer element(s). The beamformer transmitters can be programmed per channel and per beam with carrier frequency, delay, apodization and calibration values. For pulsed wave operation, pulse waveform parameters can be specified to the beamformer transmitters on a per firing basis, without degrading the scan frame rate to non-useful diagnostic levels.

Abstract: The laser optoacoustic imaging system described herein utilizes time-resolved measurement of profiles of laser-induced transient pressure (acoustic) waves. The pressure waves are emitted by acoustic sources preferentially generated in absorbing tissues of diagnostic interest. This technique allows visualization of absorbed light distribution in turbid, layered and heterogeneous tissues irradiated by laser pulses in vivo. The laser optoacoustic tomography can be used for the characterization of structure and properties of normal tissue, and for the detection of tissue pathological changes. The optical heterogeneities that can be imaged with the laser optoacoustic imaging system include abnormal tissues such as tumors, injured tissues, blood vessels and other layered tissues. Further, three dimensional images of organs and portions of organs can be obtained.

Abstract: An ultrasound or electromagnetic imaging system characterized by a two-dimensional phased array of ultrawideband, ultrasparse transducers. Ultrasparse is defined as an average inter-transducer spacing' which is greater than a .lambda./2 Nyquist spacing for the transducers and which is greater than a pulse length cT, where c is the speed of propagation of a pulse from a transducer in the imaging medium and T is a duration of the pulse. An ultrawideband low Q transient pulse is emitted by each of the transducers during a transmit mode, and the resulting ultrasound image signals are received from the transducers during a receive mode, processed, and displayed. Preferably, the transducers are uniformly weighted and excited and periodically spaced by distance and/or angle within the coordinate system of the two-dimensional phased array such that projections of the transducers onto a coordinate axis of the coordinate system minimally overlap.

Abstract: A method and apparatus are provided for imaging an object using a transducer array for transmitting one or more beams that are steered and/or translated to transmit scan lines for multiple excitation events so as to scan a field of view of the object, for sensing received signals reflected from the object after each excitation event on one or more receive beams on receive scan lines, and for transducing those sensed received signals into corresponding electrical signals.

Abstract: This invention relates to improvements in or relating to digital time-delay acoustic imaging. According to the invention there is provided an acoustic imaging method for marine survey and other purposes comprising the steps of: insonifying a target area by periodic acoustic pulses; detecting reflections of said pulses by an array of at least two receiver transducers, which transducers generate respective output signals in response thereto, wherein further the signals are: sampled in time at a predetermined rate during an interval between said pulses; converted from analog to digital form; processed so as to generate a composite acoustic signal for each pixel in the insonified target area required to be imaged; and match-filtered with optimised filters in the frequency domain with an estimated source pulse signature.

Abstract: In echo-location and imaging systems, interference suppression is accomplished by shaping the transmitted signal waveform. Interference suppression permits more accurate range estimates or image formation, respectively. These specially shaped waveforms can also be used in communication systems to secure more accurate message transmission in the presence of interference. Shaping of the transmitted signal may be accomplished in two ways: (1) by convolving an elemental waveform with a multi-level pseudorandom sequence (i.e., binary, ternary, Poisson, etc.); or (2) by transforming nonlinearly the amplitude of the elemental waveform to give it high skewness. Interference suppression in the former case is achieved through matched filtering (replica correlation or pulse compression), and in the latter case it is accomplished by bispectrum-bicoherence processing.

Abstract: An acoustic imaging apparatus and method that achieves desired delays with coded signals. Linear, curved linear and sector scanning is provided in 1-D arrays and planar, curved planar and sector scanning is provided in 2-D arrays. Composite and non-linear implementations are presented. Dynamic and discrete dynamic focusing is disclosed for the relevant arrays. The 2-D array makes possible 3-D imaging.

Abstract: A signal demodulation apparatus using a multi-ary sampling for beam formation of a received signal reduces a difference between a sampling point of time of an in-phase signal and a sampling point of time of a quadrature signal due to an existing secondary sampling method. Each of a plurality of analog-to-digital converters produces a first in-phase signal and at least two first quadrature signals adjacent to the first in-phase by sampling each input signal input via a plurality of channels at a sampling point of time having a sampling period of the input signal and other sampling points of time having a sampling interval smaller than the sampling period of the input signal. A quadrature component calculator of each channel produces second quadrature signals in which an error due to a difference between the sampling point of time of the first in-phase signal and the sampling points of time of the first quadrature signal is reduced.

Abstract: A method for imaging a target including a nonlinear contrast agent includes the steps of transmitting ultrasonic energy at a fundamental frequency and receiving reflected ultrasonic energy at a harmonic of the fundamental frequency. The ultrasonic energy is transmitted in power bursts, each having a respective envelope shape, wherein the envelope shapes rise gradually to a respective maximum value and fall gradually from the respective maximum value. Ultrasonic energy in the transmit beam is focused in an elongated high power region, as for example by means of a line focus.

Abstract: A transmit beamformer includes multiple transducers, each responsive to a respective transmit waveform to produce a respective transducer waveform. A transmit waveform generator generates the transmit waveforms, and the transmit waveforms each include multiple frequency components. Progressively higher frequency components of the transmit waveforms are timed to cause corresponding progressively higher frequency components of the transducer waveforms to focus along a line at progressively shorter ranges. In this way, a frequency dependent line focus is achieved.

Abstract: A system for radiation imaging of objects within a target area utilizing echo signals from a target area such as a patch of seafloor or the anatomy of a body. Data is obtained by time domain measurements received at a plurality of transducers in either monostatic or bistatic mode. Using multidimensional interferometry and multidimensional Fourier transforms, the data is reconstructed in multiple temporal and spatial frequency domains with a unique reduced wavenumber characteristic that retains the resolution potential of a traditional synthetic aperture approach. The system is inherently robust in applications with significant transceiver motion and/or variations in the propagation characteristics of the surrounding medium.

Abstract: A digital transmit beamformer system with multiple beam transmit capability has a plurality of multi-channel transmitters, each channel with a source of sampled, complex-valued initial waveform information representative of the ultimate desired waveform to be applied to one or more corresponding transducer elements for each beam. Each multi-channel transmitter applies beamformation delays and apodization to each channel's respective initial waveform information digitally, digitally modulates the information by a carrier frequency, and interpolates the information to the DAC sample rate for conversion to an analog signal and application to the associated transducer element(s). The beamformer transmitters can be programmed per channel and per beam with carrier frequency, delay, apodization and calibration values. For pulsed wave operation, pulse waveform parameters can be specified to the beamformer transmitters on a per firing basis, without degrading the scan frame rate to non-useful diagnostic levels.

Abstract: A transmit beamformer includes multiple transducers, each responsive to a respective transmit waveform to produce a respective transducer waveform. A transmit waveform generator generates the transmit waveforms, and the transmit waveforms each include multiple frequency components. Progressively higher frequency components of the transmit waveforms are timed to cause corresponding progressively higher frequency components of the transducer waveforms to focus along a line at progressively shorter ranges. In this way, a frequency dependent line focus is achieved.

Abstract: An ultrasonic imaging system which utilizes two summation channels to provide increased bandwidth employs two demodulation stages in each receive channel. The first demodulator receives digital signals from an analog-to-digital converter and demodulates those signals to baseband, thereby producing an in-phase component and a quadrature component. The in-phase and quadrature components are demodulated by the second demodulator, forming a total of four signals which are filtered and combined to form two sets of complex signals. One set corresponds to the upper or high frequencies and the other set corresponds to the lower frequencies. Each band is treated separately in a subsequent phase rotation. The phase changes reflect those required by the center frequency of each of the subbands. The upper band signals are coherently summed in one summation channel, while the lower band signals are coherently summed in another summation channel.

Abstract: An ultrasound/vibration detector array includes an electrically pumped vertical cavity surface emitting laser (VCSEL) array. The cavity length of each laser or pixel of the array is modulated by the acoustic field at the point where the acoustic field contacts the pixels. The resulting laser output is frequency modulated by the acoustic field. This modulation is converted to amplitude modulation at the detector head and then either detected with a charge-coupled-device (CCD) array with the information being electrically communicated to the signal processing assembly or sent directly by optical fiber to the signal processing assembly for processing. This ultrasound/vibration detector array provides high frequency bandwidth detection, fine spatial resolution, and minimal electric cabling.

Abstract: A beamformer control system includes a primary control and secondary controls so that delay and apodization beamformation profiles can be generated on a dynamic and distributed basis with sparsely sampled base delay and apodization data sets first expanded to the final values by the primary control and then further expanded in the secondary controls associated with multi-processing channels of the beamformer systems. The beamformer control system coordinates the transmit and receive beamformer systems preferably using data sets common to all beamformer systems, and by advantageously specifying to all beamformer systems, processing mode trade-offs among the signal nominal center frequency, the range spatial resolution, and the number of beams. The beamformer control system supports multiple simultaneous beam operation, as well as beam-to-beam adjustable frequency and synthetic aperture operations.

Abstract: An ultrasound acoustic scan conversion device includes an accumulator, an error correction logic unit, and a walk controller. The error correction logic unit is responsive to the accumulator and contains an error correction circuit. The walk controller is responsive to the accumulator and generates a display memory address and selects increment values for the accumulator. A method of performing scan conversion in an ultrasound system is also provided. The method includes the steps of loading at least one register within an accumulator, producing an acoustic coordinate responsive to the accumulator, producing a natural grid acoustic range value, offsetting the acoustic coordinate to produce a natural grid acoustic range value, addressing the acoustic data memory with an acoustic data memory address responsive to the natural grid range value, generating a display memory address corresponding to the acoustic data memory address, and addressing the display memory with the generated display memory address.

Abstract: A vertical acoustic array system and method for acoustically imaging the tents of a partially or completely buried tank which can contain radioactive solids and may not be entirely filled. The transducer array is placed proximate a side of a tank in a vessel such as a tube filled with water. Dirt or other filler material located between the tube and the tank is saturated with water, allowing the acoustic signal to propagate through the side of the tank and into the tank. The vertical array consists of one or more transmitting units and receiving units set in a vertical array including dipole receiving elements which allow horizontal directionality. The signals are analyzed by a field unit which includes a portable self-powered trailer providing signal transmitting and analysis devices. The field unit can transmit signals to a second unit which provides further signal analysis.

Abstract: A method and apparatus for imaging underwater targets utilizing sidelooking onar. A sonar pulse consisting of a concatenated series of subpulses is transmitted. The echo return is match filtered against each of the subpulses to produce a series of range-doppler maps, each providing information in a different direction. The range-doppler maps are normalized, thresholded, and intersected, thereby yielding data points which describe the target outline. Information as to the target length, width and orientation can be computed from the target outline data.

Abstract: An ultrasonic receive system includes two receive beamformers. A first receive beamformer is optimized for imaging modes such as B-mode and color Doppler flow imaging, and therefore has high spatial resolution and wide bandwidth, while the accompanying second receive beamformer has a wide dynamic range and is dedicated for use in acquiring spectral Doppler information, which is typically narrowband compared to imaging information. The second receive beamformer achieves the sensitivity and low-noise performance of a dedicated single-channel pencil probe instrument yet it also performs electronic beam steering. Both receive beamformers can operate through a common transducer array, thereby increasing exam efficiency and permitting registration of spectral Doppler information with a B-mode or color Doppler flow image.

Abstract: In a digital ultrasound imaging system, artifacts due to spurious ultrasound reflections from a highly reflective object outside the region of interest are reduced in magnitude by apparatus included in the beamforming system of the digital imaging system. A null is formed in a specified direction in the ultrasound beam patterns by perturbing the time delay on each receive channel. After estimating the direction of the highly reflective, interfering object and computing a time delay perturbation using a very fast algorithm, a null approximately 10 dB deep is introduced into each beam in the direction of the interfering object. This null reduces the magnitude of artifacts in the image, thereby providing image enhancement.

Abstract: An ultrasonic imaging system provides dynamic focusing by using dynamic group delay in addition to dynamic phase focus. FIFO memory storage capacity in the beamforming circuit is increased to provide improved resolution of the data samples stored therein. These samples are selected by an address counter in response to both the advance of time and the accumulation of a phase advance clock count. After a Read Start signal, indicating the start of a beam, is supplied to the FIFO memory, the FIFO memory address is advanced, on each read instruction, by the number of address locations corresponding to the period of a pipeline channel. In addition, the address is incremented whenever the accumulated count of a phase advance clock exceeds an amount corresponding to the smallest increment of the data stored in the FIFO memory.

Abstract: An acoustic wave imaging system comprises a prism for mounting to the back surface of a piezoelectric substrate of an acoustic wave device. The piezoelectric substrate comprises a front surface on which metallic interdigitated input and output transducers mount for generating acoustic waves on or below the front surface. An electric signal source connects to the input transducer while a load connects to the output transducer. The device may also include spaced metallic reflectors. A large laser beam propagates through an entrance face of the prism, passes through the back surface of the piezoelectric crystal and internally reflects off the front surface of the piezoelectric crystal. The laser beam diffracts into a number of components due to the creation of periodic surface corrugations and or periodic refractive index perturbations beneath the surface, which are caused by the acoustic waves. The beam components exit the prism and are focused by a lens onto its image plane.

Abstract: An ultrasonic transducer for measuring a property of a material within a defined space has a function of a velocity at which ultrasonic signals travel through the defined space includes a controller. The controller is adapted for coupling to a plurality of ultrasonic transducers. The controller include a multiplexer for selecting one of the plurality of ultrasonic transducers, signal processing means for processing an output of the selected ultrasonic transducer and controller means for providing parameters to the signal processing means based upon the selected ultrasonic transducer. The controller couples to a two wire 4-20 mA communication loop. The controller periodically excites the ultrasonic transducer to obtain a measurement. The controller stores power received from the two wire communication loop and excites the transducer using stored power. The controller is capable of providing power which exceeds that available directly from the two wire communication loop for a brief period of time.

Abstract: A viewing screen apparatus for helmets or face masks of the type having a viewing area covered by a face plate is disclosed. The apparatus includes an enclosure adapted to be mounted on a helmet or face mask adjacent the face plate, a solid-state flat panel display screen and associated circuitry contained within the sealed enclosure for displaying visual images on the screen responsive to electronic signals, and a signal receiver connected with the screen for enabling the screen to receive electronic signals from an electronic signal transmission source. In one embodiment the enclosure is selectively movable between a viewing position adjacent the face plate and a position out of the wearer's field of vision to allow an unobstructed field of vision through the face plate.