Abstract: The invention concerns an ultrasonic transducer for the determination of the acoustic power of an ultrasonic field (1) focused at a point (F). According to the invention, an ultrasonic transducer 2 contains a support structure (4) which has the shape of a spherical cup and whose center coincides with the focus (F) of the focused ultrasonic field (1), and a piezoelectric polymer foil (6) equipped on its respective surfaces (62, 64) with a conductive layer (8) is attached to said support structure. These measures ensure that the acoustic charge vibrations within the area formed by the piezoelectric polymer foil (6) are at least approximately in phase and that the respective surface charge vibrations can be measured with the aid of a single, continuous electrode without partial mutual cancellation.

Abstract: The invention concerns a method for surveying the focal point (F, F') of a focussed ultrasonic field (8, 14) and an apparatus for carrying out the method. According to the invention an ultrasonic field (4, 12) produced by an ultrasonic transmitter (2) is measured at several sites in a plane in the path of the waves at the site of the imaging device (6). The values determined at these sites are compared with given reference values for which the position of the focus is known. In an advantageous device, one surface of the imaging device (6) is equipped with several piezoelectric transducers.

Abstract: An apparatus for introducing vibrations into the ground including a container having electrodes mounted therein with electrical connections leading from a source of electric potential to said electrodes, salt water substantially filling the container, and means for placing the container on the ground in position to transmit vibrations to the ground.

Abstract: A sound transmitter for generation of transient acoustic pulses, comprising a spatially curved focussing emitter surface which is represented by the area of a single active or passive emitter or by the areas of several emitters matched in respect of their period of operation and amplitude. The pulses occurring in the region of the focus are generated by a substantially unipolar and chronologically limited pressure and/or velocity evolution at the emitter surface.

Abstract: A frequency independent constant beamwidth lens antenna concept is descri. The device may be configured in various ways such as with a cylindrical lens with a retina. The essential feature is that a twisted planar or hyperbolic paraboloidal phase or wave front is formed by the antenna which then in turn produces a frequency independent constant beamwidth beam in the far field of the antenna. Moreover, the frequency independent constant beamwidth beam may be steered or scanned in azimuth without moving the lens.

Abstract: Navigation systems which position one or more mobile platforms in real time with appropriate accuracy in reference to a known system of coordinates by the emission of signals into a propagation medium and processing them after detection are disclosed. Broad-band, broad-beam signals are employed. All received signals convey phase encoded angular coordinate information which characterizes the particular signal path. Phase encoding of angular information is effected by suitably configured "lenses" of dispersive materials or by post-critical angle reflection from a suitably configured reflector and shield combination. When the angular coordinate information is used in conjuction with range determinations from detected signals, an especially useful navigation system is provided which can operate from a single reference station.

Abstract: A compact apparatus for transmitting and receiving multiple sonar beams utilizes an acoustic lens to direct plane waves incident in desired directions to collimating lenses for presentation in phase to electroacoustic transducers having planar surfaces. The electroacoustic transducers emit sound waves which are transformed by the lenses into plane waves emergent in the desired directions.

Abstract: A frequency independent acoustic antenna has an acoustic filter plate located between a lens and sensor/transmitter. When used as a receiver this arrangement of components enables the lens to receive plane waves emanating from a source. This results in materially enhanced beam forming characteristics and performance. The arrangement is also suitable for use in the transmitting mode.

Abstract: A frequency independent log periodic acoustic device is utilized for the transmission or reception of underwater sound. A key element of the device is a particularly shaped plate or diaphragm, called a filter plate, made of stainless steel or other material having suitable acoustic properties. The filter plate on being placed in front of any plane wave receiving or transmitting transducer acts automatically to make the beamwidth of the diffraction pattern of the combined device constant, regardless of frequency. This is achieved by automatically making the effective aperture diameter of the filter plate-transducer combination a constant multiple of the acoustic wavelength of the sound in the underwater medium. When used in conjunction with a scannable transducer such as an acoustic lens and the retina device the filter plate produces a directional, scannable, substantially constant beamwidth diffraction pattern for radiation or reception of underwater acoustic signals.

Abstract: An ultrasonic imaging system comprises a transducer array including a plurality of elongated piezoelectric transducers successively arranged along a curved surface for emission of diverging beams of acoustic energy and an acoustic diverging lens affixed to the curved surface for increasing the angle of divergence of the emitted acoustic energy. The system includes a source for successively generating burst energy and means for selectively establishing a connection from the energy source to a subarray of the transducers to transmit a beam of acoustic energy therefrom and shifting the connection to the next subarray by at least one transducer in response to the generation of subsequent acoustic energy to cause the emitted acoustic energy to be angulated in an arc scan format. Means are provided for compensating for differences in energy level resulting from the differences in the path-length of the acoustic lens.

Abstract: A compact apparatus for transmitting and receiving multiple sonar beams utilizes an acoustic lens to direct plane waves incident in desired directions to electroacoustic transducers positioned on spherical shell segments centered in the focal regions of the lens associated with the incident beams. The electroacoustic transducers transmit spherical waves that are transformed by the acoustic lens to plane waves emergent in the desired directions.

Abstract: An ultrasound imaging apparatus and transducer means which produces a converging beam pattern focused along the axis of the transducer with increasing beam concentration towards the furthest point of convergence of the beam pattern.

Abstract: A frequency independent log periodic acoustic device is utilized for the transmission or reception of underwater sound. The acoustic device when used in conjunction with any substantially plane wave receiving or transmitting transducer produces a directional, substantially constant beamwidth diffraction pattern for radiation or reception of underwater sound signals. A key element of the device is a particularly shaped plate or diaphragm, called a filter plate, made of stainless steel or other material having suitable acoustic properties. The filter plate on being placed in front of any plane wave receiving or transmitting transducer acts automatically to make the beamwidth of the diffraction pattern of the combined device constant, regardless of frequency. This is achieved by automatically making the effective aperture diameter of the filter plate-transducer combination a constant multiple of the acoustic wavelength of the sound in the underwater medium.

Abstract: An ultrasonic transducer array for arc scan imaging systems comprises a plurality of elongated piezoelectric transducers arranged successively to define a convexed energy radiating surface. A plano-concave acoustic diverging lens is attached to the convexed surface to diverge the acoustic energy transmitted from the transducers in an increased steering angle. The transducers are assembled on an impedance matching layer which defines the convexed radiating surface. The acoustic impedance of the diverging lens is substantially equal to the acoustic impedance of the human body, while the acoustic impedance of the impedance matching layer is greater than that of the human body.

Abstract: An ultrasonic transducer element includes a polymer piezoelectric film having a plurality of sections. The sections are defined by wave planes of ultrasonic waves having substantially .lambda./2 phase difference emanated from an imaginary focal point or line located in front of the piezoelectric film. .lambda. is the wave length of the ultrasonic waves within an acoustic transmission medium located between the piezoelectric film and the imaginary focal point or line. The sections are arranged so that ultrasonic waves emanated from adjacent sections have substantially no phase difference at the imaginary focal point or line. Front and rear electrodes are deposited on opposite surfaces of the piezoelectric film.

Abstract: The invention provides a highly focussed ultrasonic wave throughout a large depth of field without any mechanical motion. One embodiment of the invention providing two focussed fields includes a front to back arrangement of a converging lens, a transducer without any backing material to dissipate ultrasound, a converging lens, and a transducer. To focus in the far field, the front transducer transmits and receives via the front lens. To focus in the near field, the rear transducer transmits and receives via both lenses which collectively focus in the near field.

Abstract: A probe primarily applicable to medical echography for achieving a variable compromise between depth of field and lateral resolution incorporates a main piezoelectric transducer, a plano-convex lens having an elastic diaphragm, an auxiliary transducer for measuring the deflection of the lens and means for controlling the deflection in dependence on a reference value by modifying the pressure exerted on the diaphragm by the fluid contained within the lens.

Abstract: A wide band, substantially constant beamwidth, frequency independent, scable acoustic array uses a mosaic pattern acoustic lens arrangement of fully directive acoustic lens antennas as the primary array antenna elements. The lenses at the center of the array pass signals at all frequencies, the lenses near but not at the center pass all signals except those at the highest frequencies and the lenses on the outer periphery pass only those signals at the lowest frequencies. When used as a transmitter, a wide band source supplies a broad band frequency signal to a plurality of filters, time delays, amplifiers, switches and acoustic retinas for applying predetermined signals to the acoustic lenses. When used as a receiver the same plurality of filters, time delays, amplifiers, switches and acoustic retinas act in a complimentary reciprocal fashion in the recovery of signals.

Abstract: A conical acoustic lens in conjunction with a ring of transducer elements located on a circle disposed above the lens is utilized to form a plurality of radial beams for imaging a target area beneath the apparatus. The transducers may occupy the fully 360.degree. of the circle or a sector less than 360.degree. in which the case the apparatus may be rotated to give full 360.degree. coverage.

Abstract: Parametric array Doppler sonar apparatus includes an acoustic lens containing a flat disk-like central portion and an annular outer portion serving as a convergent lens. Multiple transducers are positioned between the lens and the focal plane so as to launch collimated acoustic beams in specified directions through the central portion of the lens and to receive reflected energy propagating principally through the annular portion of the lens.

Abstract: A probe for an ultrasonic diagnostic apparatus is provided which has a supporting plate and a plurality of electro-acoustic transducers arranged in a line on the supporting plate. A thin film with flexibility and watertightness is attached to the electro-acoustic transducers so that the spaces between the adjacent electro-acoustic transducers are hermetically sealed. The result is a reduction in the acoustic coupling between the adjacent transducers.

Abstract: The fabrication of ultrasonic-wave lenses and prisms using low-surface tension (poor adhesion) polyalkene sheet (such as polyethylene) as an impedance-matching quarter-wave anti-reflective layer is made possible by the use of certain very low surface-tension cements.

Abstract: The present invention relates to refractive stigmatic systems designed to deflect or focus elastic surface waves which can propagate at the surface of a substrate. The object of the invention is a lens or prism comprising an array of elementary refractive zones formed by deposition or ion implantation and intended to produce uniform attenuation of refracted vibrational radiation.

Abstract: A single acoustic filter plate-lens unit for providing directional, frequy independent beam-forming. The unit comprises a liquid container having a curved and radially tapered stainless steel plate on one side and thin metallic shell on the other. An acoustically slow liquid fills the space between the plates. The unit can be used in conjunction with a retina transducer system for conversion of acoustic signals into electrical signals and vice versa.

Abstract: The invention provides a highly focussed ultrasonic wave throughout a large depth of field without any mechanical motion. One embodiment of the invention providing two focussed fields includes a front to back arrangement of a converging lens, a transducer without any backing material to dissipate ultrasound, a converging lens, and a transducer. To focus in the far field, the front transducer transmits and receives via the front lens. To focus in the near field, the rear transducer transmits and receives via both lenses which collectively focus in the near field.