Abstract: A new method of Acoustic Holography permits moving 3-D scenes by replacing a fixed film record of an interference pattern with a "live interference pattern" which is continuously altered by the information on a rotating CD.

Abstract: There is disclosed an omnipresent sound system for use by a listener in an artificial reality system which operates to couple sound with the presented objects such that as the sound moves with respect to the user, the user will have the perception of the changing sound both in pitch and in volume. The sound system is comprised of a series of piezoelectric elements spaced apart around a user's head. The system is designed to program each element individually so as to create the illusion of omnipresent three-dimensional sound in conjunction with images presented to the listener, which images define an artificial environment.

Abstract: A preferred embodiment of this invention is illustrated in FIG. 4 showing an offset and tilted object transducer 50 being rotated about a system axis 51 to sequentially insonify the object from various acute incident angles .theta. to the system axis to provide images of the out-of-focus structures at spaced locations at the hologram detection surface 18 at different spaced times. If the pulse rate of the object transducer is greater than the fusion of the eye, the eye is able to average two or more images into a single perceived image. Likewise, video equipment that receives images at a rate greater than 30 Hertz will average two or more images and display the image at a rate of approximately 30 Hertz. Additionally, external video processing may be utilized to electronically average two or more images electronically to obtain an averaged image at any time constant desired by the operator.

Abstract: The preferred embodiment of this invention is illustrated in FIG. 2 showing an ultrasonic holographic imaging apparatus 50 having a multiple lens system 52 that is capable of providing both zoom and focus capability. The system 52 includes lens 54 and 56 that are independently mounted on lead screws 62 and 64 for movement relative to each other along an optical axis 57. The movement of the system is controlled by drive system 66 and 68 that have encoders 72 and 74 for accurately positioning the lens 54 and 56 relative to each other in response to signals from a microcontroller 76. The microcontroller 76 is operator controlled through control device 78 and 80 to provide both zoom capability and a focus capability.

Abstract: A preferred embodiment of the optical reconstruction assembly 50 in which the assembly 50 includes an assembly housing 52 that is a unitary unit for supporting a spatial filter 72 and a light source 74 in a single plane at the optical length "L" from a collimating lens 86. A liquid container 88 is mounted to the assembly housing 52 containing the holographic liquid 90. The light source 74 and the spatial filter 72 are spaced a fixed distance "A" which is less than the optical diameter "D" of the collimating lens 86.

Abstract: A system for radiation imaging of an object in response to echo signals from a target area of the object, such as a region of the anatomy of a body. Data is obtained by time domain measurements at monostatic transducers which can be disposed in different locations. The data is processed by two-dimensional Fourier transformations reconstructed using a mapping function and which compensates for variation in the radiation pattern at the various detector locations by using a phase correction function which avoids the need for Fresnel or plane wave approximations.

Abstract: A three-dimensional object imaging method is implemented on a computer for imaging an object. The three-dimensional object imaging method includes the steps of irradiating ultrasonic waves having two mutually different frequencies on the object which is to be imaged, measuring sound pressures of scattering waves from the object so as to obtain two acoustical holography images thereof, and obtaining a three-dimensional shape of the object based on a phase error between the two acoustical holography images.

Abstract: An acoustic imaging system which employs a liquid crystal cell for detecting acoustic energy and displaying an image. The cell includes a layer of liquid crystal material which is disposed between and encapsulated by a pair of cover members. At least one of the cover members is a laminated structure having at least two plies. The plies are of different materials and the thickness of each ply is governed by the expression n .lambda./2, where n is an integer, and .lambda. is the wavelength of the acoustic energy in the cover materials. This structure enhances cell rigidity and the uniform of thickness of the liquid crystal layer in larger sized cells, while maintaining good transmission for energy angularly incident on the cell.

Abstract: An apparatus for observing a sound field of an ultrasonic wave, including a first unit which determines characteristic values of a medium at each point of a predetermined region by an ultrasonic wave having a sound field of an arbitrary form and a second unit which displays an output of the first unit as two-dimensional or three-dimensional distribution in the predetermined region, and allows control of the form of the sound field of the ultrasonic wave.

Abstract: There is disclosed herein an apparatus and method for producing a substantially uniform acoustic field for use with a liquid crystal cell to produce a substantially artifact-free image of an object. The apparatus and method include moving an ultrasonic transducer toward and away from an object, a distance effective to cause adjacent constructive and destructive zone patterns to in effect overlie each other. The period of reciprocation is less than the time for onset of image decay, but greater than the image rise time so as to assure image formation. In addition, the frequency and/or phase of the acoustic energy can be varied so as to further enhance the image.Electro-mechanical and piston driven embodiments are disclosed for reciprocating the transducer.

Abstract: There is disclosed herein an ultrasonic imaging system using a liquid crystal detector cell and a source of non-coherent acoustic energy to produce substantially artifact-free images. The ultrasound source and cell are matched with one another, and the source is caused to operate over a range of frequencies or phases so as to produce the non-coherent ultrasonic energy. The frequency response of the cell and its response time are matched to the operating characteristics of the transducer. The transducer may be mounted in a pendulum-like sector scanning apparatus so as to assure a uniform insonification of the object, a uniform beam and a substantially uniform non-coherent insonification of the cell. The movement of the scanning apparatus is also matched to the cell and the transducer characteristics.

Abstract: In an ultrasonic computed tomography system including an image signal-processing apparatus for reconstructing an image signal of an object on the basis of a synthetic aperture technique, a probe includes a transducer unit. The transducer unit emits an ultrasonic beam to the object and detects the corresponding echo wave. Hologram data is produced in response to the echo wave and then digitized to have a predetermined number of bits by A/D converters. The digital hologram data is temporarily stored in buffer memories and read out under the control of a computer unit. The computer unit has a ROM assembled therein to prestore digital kernel function data, the number of whose bits is smaller than that of the digital hologram signals. The computer unit executes a convolution on the digital hologram data and the kernel function data, thus increasing the speed of a computation needed for image reconstruction.

Abstract: The fault-containing area to be inspected is insonified by means of an ultrasonic transducer with a space-limited beam which is displaced in stepwise manner, the signals coming from the successively insonified areas being detected by several receivers, the phases and amplitudes of the signals being determined and the reconstitution of the area to be inspected performed. There is a main image of the fault and also parasitic images thereof. The number of receivers is chosen in such a way that the distance between the parasitic images and the main image exceeds the width of the area insonified by the transmitter and the reconstitution is only carried out in the insonified areas having given rise to a signal in order to eliminate the parasitic images. Application to the non-destructive inspection of mechanical parts.

Abstract: An apparatus for reconstructing an image signal of a foreground subject wherein a probe having a plurality of transducers for scanning a foreground subject by radiation, such as an ultrasonic beam, is connected to a phase detector through a receiver. An electrical signal corresponding to a wave reflected from the foreground subject is phase-detected by a phase detector. At least one resultant hologram signal is subjected to the A/D conversion to be stored in a buffer memory. A processing unit causes the hologram signal to be read out of the buffer memory, carries out the convolution integration of the hologram signal and the corresponding kernel function data by the synthetic aperture technique, thereby producing a reconstructed image signal. The processing unit further carries out the nonlinear compression of the amplitude of the hologram signal before the convolution integration and performs the nonlinear expansion of the amplitude of an image signal after the convolution integration.

Abstract: The surface acoustic waves are generated by laser beam that is focussed onto a surface to irradiate it in an arcuate pattern as a partial annulus or as a still or moving fringe pattern. The arcuate pattern may be formed by a transmitting or a reflecting axicon, while the fringe pattern may be formed by splitting the laser beam into two beams and directing the two beams to the surface. In addition, a lens or a frequency shifting device may be placed in the path of one of the split beams to form a circular fringe or a moving fringe, respectively.

Abstract: Defects in a structure are imaged as they propagate, using their emitted acoustic energy as a monitored source. Short bursts of acoustic energy propagate through the structure to a discrete element receiver array. A reference timing transducer located between the array and the inspection zone initiates a series of time-of-flight measurements. A resulting series of time-of-flight measurements are then treated as aperture data and are transferred to a computer for reconstruction of a synthetic linear holographic image. The images can be displayed and stored as a record of defect growth.

Abstract: In a method of and an apparatus for detecting flaws inside articles, the flaw area for detection being subjected to ultrasonic pulses on which, after reaction with the flaw, a reference beam is superimposed, whereupon the resulting interference field is holographically detected, reconstructed and evaluated. This method can be applied to thin and sound-scattering materials with improved resolution and a description of the flaw configuration and detection of the deformation behavior of flaws. In the method, a load is applied to the flaw area under investigation and this area is subjected to ultrasonic pulses at least at two different times each corresponding to an extreme value of the loading, the ultrasonic pulses being short with respect to the load period and, after reaction with the flaw, reference pulses are superimposed on the ultrasonic pulses, whereupon the holograms of these ultrasonic applications are superimposed to give an interferogram which can be evaluated.

Abstract: There is disclosed herein a movable, ultrasonic transducer array for use in an ultrasonic inspection system that employs a signal detector and display of the liquid crystal cell type. The movable array uniformly insonifies the object to be inspected and is particularly suitable for inspecting large objects or large areas of an object. The array may include a plurality of sending or emitting transducers which are held in substantially parallel alignment so that their transmission or radiation axes are parallel. The array is part of an assembly which includes a support for holding the transducers and a drive system for moving the array and support along a predetermined path.In a first specific embodiment, the array is mounted on a support which moves along a circular path while maintaining the relative horizontal and vertical positions of the transducers. That movement is accomplished by use of a drive and linkage system which provides for an eccentric-like movement.

Abstract: A series of pulses are transmitted to a first laser and the same series of ulses through a time delay network to a second laser. Each laser provides pulses of light through separate diagonal mirrors and through respective transparent holograms. Each light beam is then brought into convergence by respective sides of a wedge shaped reflector and brought into spacially coincident focus by an imaging lens onto the surface of a sample under test. The two hologram transparencies are imaged spacially coincident but separated in time on the face of the sample. Thermal elastic waves produced by laser heating at the sample surface transform into a desired acoustic beam pattern determined by the nature of the wavefronts which the hologram transparency represents. The position of the coincident image on the sample may be moved by varying the time between the two pulses.

Abstract: In the disclosed method and structure a pulse of a sound filed to be mapped is illuminated at at least two extremes values at different moments with a laser beam of short duration compared to the period of the illuminated sound pulse and interference produced between the resulting reflected beam and a reference beam. A holographic image is formed. The relative phase of the laser pulse and the reference is changed between the individual illuminations by a preselectable amount which deviates from .pi. and which suppresses the optical and/or acoustical noise. Specifically, a time delay initiates the first illumination process when an extreme value is reached at the beginning of the sound pulse to be mapped. A counter is started by this time delay and counts the half and quarter waves of the sound pulse. The counter initiates an additional illumination process after a preselectable odd number has been reached. A phase shifter changes the relative phase between the object beam and the reference beam.

Abstract: There is disclosed herein an ultrasonic imaging system for use in non-destructively testing objects, which system includes a source of ultrasonic energy, a liquid crystal detector cell and an optical viewing system. The liquid crystal detector cell includes a pair of acoustically transmissive covers which encase a nematic liquid crystal material. The material exhibits an acousto-optic effect, and in particular, exhibits birefringence in response to ultrasonic energy. The cell construction, geometry, and material are acoustically matched to the frequencies of the insonifying ultrasonic transducer so as to optimize the performance of the cell. The covers are substantially acoustically transparent to ultrasonic energy incident on the cover at both normal and oblique attitudes. The acoustic impedance of the covers match as closely as possible to that of the coupling medium.

Abstract: There is disclosed herein an acoustic or ultrasonic power meter which includes a liquid crystal cell for detecting acoustic energy and a control circuit for applying an electric field to said cell. The liquid crystal cell includes a liquid crystal material having elongated molecules. The preferred liquid crystal is in the form of a layer of the nematic type which is homeotropically aligned. The elongated liquid crystal molecules exhibit positive dielectric anisotropy wherein the dielectric constant parallel to the molecule's axis is greater than the dielectric constant perpendicular to the molecule's axis. In the unexcited condition, the nematic layer is dark. In the ultrasonically excited condition, the nematic layer exhibits birefringence. A restoring electric force can be applied to the liquid crystal material to suppress the acoustically-induced birefringence condition of the cell to the dark appearance associated with the unexcited condition.

Abstract: There is disclosed herein a portable device for inspecting bodies for internal flaws or other internal features. The device is constructed so as to be mounted on the surface of the body, emit and receive ultrasonic energy, and display the same on a liquid crystal display. The device includes a first housing member for supporting a transducer in relation to the surface being inspected. The device also includes a second housing member for supporting and positioning the liquid crystal display in relation to the surface and in relation to the transducer. Interconnecting means are provided for adjustably interconnecting the two members and fixing their positions in a reflection-receiving relation. The liquid crystal support housing is a substantially hollow tubular member having a viewing end and a surface contacting end. The liquid crystal display is positioned intermediate the ends.

Abstract: There is disclosed herein an ultrasonic system for detecting internal discontinuities in a body. The system includes: an ultrasonic transducer for directing sonic energy toward a body; a liquid crystal, acousto-optical detector cell for detecting ultrasonic energy passing through said body; an optical system for illuminating said liquid crystal cell; and a liquid medium for coupling the transducer body and cell.The acousto-optical cell includes a pair of substantially rigid covers, a liquid crystal material positioned between said covers and a peripheral spacer and sealing member surrounding said liquid crystal and sealingly engaging said covers. Each of the covers is substantially acoustically transparent and at least one of said covers is optically transparent. The optically transparent cover is a laminate having at least three layers, with each of said layers of said laminate having a thickness much much less than 1/4 of the wave length of the ultrasonic energy propagating through said layer.

Abstract: A digital type ultrasonic holography apparatus includes a clock generator for generating a clock pulse signal having a fixed period, a transducer for transmitting spike-like ultrasonic pulses toward an object in synchronism with trigger pulses derived through the frequency division of the clock pulse signal and receiving the reflected wave from the object, a waveform shaping circuit for shaping the received wave into a digital pulse signal, a coincidence detecting circuit for narrowing the pulse width of the digital pulse signal to a magnitude shorter than the period of the clock pulse signal and judging whether or not the pulse width-narrowed digital pulse is present at the level-changing time of the clock pulse signal, thereby to generate a coincidence signal, a scanner for scanning the transducer, and a device for displaying a hologram of the object in accordance with the value of the coincidence signal and the scanning of the transducer.

Abstract: The invention is related to an acousto-optical liquid crystal cell and the ways of using it in acoustical holography and imaging systems. The molecules of the liquid crystal layer can be reoriented in a direction perpendicular to the direction of an ultrasonic wave propagating in the medium. The cell has multi-layered walls providing high acoustical transparency for waves incident at various angles, such that multiple reflexions and parasitic effects in the liquid crystal are reduced. This results in a wide acoustic imaging field and high resolving power for details of an acoustic object. This cell makes possible the direct and real-time conversion of an acoustical hologram into a visible image representing at will the intensity on the phase variations of ultrasonic waves coming from the internal structures of a body.

Abstract: A new halographic method for converting one wave into another wave by means of a hologram is disclosed. This method comprises mixing an object wave with a reference wave whose wave front in the hologram plane is different from that of the actual reconstruction wave in the same plane. The phases and possibly also the amplitudes of these two wave fronts are combined in such a way that compensation is obtained for imaging errors caused by mutual inconsistencies between the wavelength ratio, the hologram scaling and the object scaling, and a displacement of the reconstructed object relative to the hologram. The reference wave and the reconstruction wave are chosen so that the converted object wave field becomes "as equal as possible" to a wave field coming from another but geometrically similar object at a different wavelength. In an example concerning seismic holography a formular for choosing a proper synthetic reference wave is given.

Abstract: The work is scanned by acoustic energy from a focused-arc transducer and from an acoustic-lens transducer. An echo-ranging subassembly energizes the focused-arc transducer and processes the echo trains relfected from the lines or pencils in the work along which the acoustic energy is focused. A holographic echo-processing subassembly is connected to energize the acoustic-lens transducer and to process the echoes reflected from the work where the energy from the acoustic lens impinges. The echo-ranging subassembly and the holographic echo-processing subassembly are enabled alternately and the acoustic energy from the focused-arc transducer and from the acoustic-lens transducer impinge on, and is reflected by, each of a succession of elemental areas of the work. The outputs of the echo-ranging subassembly and of the holographic echo-processing subassembly are supplied to an elastic store which may include one or more shift registers.

Abstract: The invention relates to the acousto-optical imagery of objects transmitting ultrasonic waves; an optical image diffracted by the action of an ultrasonic wave is detected by coherent detection in an electro-optical and photoconductive holographic recording material under an applied field by holographic recording of the interferences between the diffracted order to be imaged formed by the optical wave of pulsation .omega..sub.o +.omega..sub.s (or .omega..sub.o -.omega..sub.S) and an optical reference wave having the same pulsations. Imagery is effected in real time by restoration of the object wave by a reading wave having the same pulsation as the reference wave.

Abstract: A method and apparatus employing zero order Raman-Nath diffraction information to visualize the longitudinal character of an acoustic field. The method includes the steps of directing a first portion of a beam of coherent light at normal incidence to a reflective mirror, propogating an acoustic field within a medium to interact with the first portion of the beam, detecting signals derived from the acousto-optical interaction from which phase change and amplitude change information in the reflected zero order diffraction component of the laser beam can be derived after its return pass through the acoustic field and then generating a two-dimensional raster scan representation of the acoustic field from the detected light signals.

Abstract: Echo ranging flaw detecting, characterizing and studying apparatus in which the work is scanned simultaneously by acoustic energy focused at a point from an acoustic-lens transducer and by acoustic energy focused along a line along which it is propagated from a focused-arc transducer. The acoustical echos from the lens transducer are combined with an electrical analog of an acoustical reference wave to produce an acoustical interference pattern which is reconstructed into a holographic display or hologram by a laser beam. The echos from the focused-arc transducer produce a cathode-ray tube display or are stored in a memory.

Abstract: To provide an improved holographic operation, a digital type ultrasonic holography apparatus is provided utilizing a clock pulse generator having a predetermined periodicity, an ultrasonic pulse beam generator for directing an ultrasonic beam to an object for measurement in synchronism with said clock pulse, a reflected wave conversion unit for converting reflected ultrasonic pulse beams from said object for measurement into digital pulses, a time coincidence detector for detecting time coincidence between said clock pulse and said digital pulses contained in a predetermined gate period and producing as output a coincidence signal when they coincide with each other, a unit for moving an ultrasonic generating and receiving transducer included in said ultrasonic pulse beam generator to a desired position, and a display device for displaying the hologram of said object for measurement using said coincidence signal as a luminance signal and a position signal of said ultrasonic generating and receiving transducer

Abstract: An underwater apparatus is described for acoustically inspecting a submerged object at considerable depths such as the lower structural portion of an off-shore drilling rig to determine if the structure has internal defect which cannot be optically detected. The apparatus is intended to operate in depths of up to 500 meters. The apparatus includes an underwater craft for transporting both humans and equipment to the submerged object. The apparatus includes a hand held acoustical and optical probe that is movable by a diver over the surface of the submerged object. The probe includes an array of acoustical transducers that are sequentially activated to acoustically scan the interior of the object. The acoustical transducers are mounted in a flexible support material to accommodate the array to the contour of the surface. The probe additionally includes a real-time display of the acoustical information to assist the diver in effectively inspecting the object.

Abstract: A linear transducer array for transmitting and receiving acoustic waves in both pulse-echo and holographic modes of operation. For pulse-echo acoustic imaging the array includes a linear subarray of transmitting transducer elements disposed in a plane along a longitudinal axis. Each transmitting element has an elongate shape and a principal axis that is perpendicular to the longitudinal axis of the array. For holographic imaging the apparatus further includes a removable mechanical shutter for blocking a predetermined portion of the principal axis of each of the transmitting elements so that a dispersive acoustic beam can be generated. The array also includes a linear subarray of receiving transducer elements coplanar with the transmitting subarray and disposed parallel to the longitudinal axis. The subarray of receiving elements is used to detect the reflected acoustic waves for both holographic and pulse-echo imaging.

Abstract: A scan acoustical holographic apparatus and method is described for sequentially acoustically scanning the interior of an optically opaque volume. The apparatus includes an array of acoustical transducers that are coupled to the volume. A plurality of frequency divider means receive high frequency clock pulses and generate transmit electrical pulse signals to the transducers having a frequency that is a fraction of the clock pulse frequency. The phases of the transmit signals are controlled by programmable read-only-memories in accordance with the distances between the transducers and selected focal points within the volume to effectively focus the transducers on the focal point. Receive signals are mixed with the phase adjusted transmit signals to effectively focus the transducers during a receive mode and to generate high amplitude holographic signals when the receive signals are in phase with the phase altered transmit signals.

Abstract: A method and apparatus for directly obtaining displacement-amplitude information from a quadrature-dual interferometer. The system uses a "mini-wiggler" to introduce phase shift into the reference beam, as by oscillating a reference mirror with a piezo-electric crystal. The mini-wiggler produces relatively small phase perturbations of the order of 0.001.lambda. at a frequency at either edge or in the middle of the signal frequency band. The system uses a signal-processing circuit to obtain displacement amplitude directly. The purpose of the mini-wiggler is to produce a "pilot" signal of known amplitude and phase from which the correction terms needed to compensate for variations in the interferometer state, such as those caused by vibration, large variation, drift, and the like, are derived and can be applied by means of another signal processing circuit.

Abstract: An automatic hybrid holograhic non-destructive testing (HNDT) method and system capable of detecting flaws or debonds contained within certain materials. This system incorporates the techniques of optical holography, acoustical/optical holography and holographic correlation in determining the structural integrity of a test object. An automatic processing system including a detector and automatic data processor is used in conjunction with the three holographic techniques for correlating and interpreting the information supplied by the non-destructive systems. The automatic system also includes a sensor which directly translates an optical data format produced by the holographic techniques into electrical signals and then transmits this information to a digital computer for indicating the structural properties of the test object. The computer interprets the data gathered and determining whether further testing is necessary, as well as the format of this new testing procedure.

Abstract: A system employing ultrasound for the reconstruction of the absorptivity and refractivity properties of ultrasonic radiation internal to a solid, liquid or partly solid and liquid object, air vacuoles being excluded, in the vase that this radiation is highly scattered (reflected or refracted). The reconstruction consists of a three-dimensional simulation of these acoustic properties in a powder mixture which allows access to absorptivity and refractivity information without disturbance either to itself or to the object which it simulates. The reconstruction method is a multi-stage process in which the absorptivity and refractivity of the object are sampled layer-by-layer and recorded in mirror-image layers in the reconstruction.