Abstract:
Disclosed is a seabed surveying apparatus wherein a first acoustic fan beam is transmitted to seabed to provide a two-dimensional topographic representation of echoes from successively greater ranges. A second acoustic fan beam is transmitted to seabed to provide a two-dimensional bathymetric representation of echoes returning from equal profiles of the varying topography. The topographic and bathymetric representations are superimposed on a common X-Y coordinate display field.
Abstract:
The present invention provides a method and device for determining the positioning of an element or target using at least one acoustic emitting-receiving sensor. In this method only the signal received by said sensor and due to the diffraction of the signal emitted by said sensor is taken into account.
Abstract:
A device for electronic focusing of ultrasonic waves in which the focusing means comprise a hierarchized assembly of elementary circuits each provided with a delay line connected in parallel with a direct line to a centralizing unit and in which the time-delay of the delay line in a circuit is a function of the relative time-delay which must exist between the two cells or the two circuits connected to said circuit. It is shown that, in the invention, a technological advance is achieved by thus minimizing the maximum time-delays to be established in the case of each delay line.
Abstract:
An ultrasound apparatus permitting dynamic variation of the position of the reception focus of a prescribable number of ultrasound transducer elements has a reception channel including a time-delay circuit for the received ultrasound echo signal following every ultrasound transducer element. For switching between different, prescribed time-delay values (T.sub.1, T.sub.2, . . . T.sub.n), the time-delay circuit is connected to a control device. A part of the time-delay circuit is redundantly designed, so that first and a second sub-circuits for forming the time-delayed ultrasound echo signal are present. A dissolve circuit is provided which causes the second sub-circuit to be faded in the reception channel when the first sub-circuit, in a blanked condition, is switched to a different time-delay value (T.sub.1, T.sub.2, . . . T.sub.n), and vice versa, by a control device. Significant time is thus saved when switching between the different focus positions of the ultrasound apparatus. Transmission of switching clicks onto the respectively activated sub-circuit is prevented by the use of isolating amplifiers.
Abstract:
An apparatus for displaying ultrasonic images picked-up by an ultrasonic microscope including a digital scan converter having three image memories for storing successively picked-up three ultrasonic images. The digital scan converter functions to reconstruct a color image from the three ultrasonic images by simultaneously reading ultrasonic image signals out of the image memories as red, green and blue color signals.
Abstract:
A bistatic sonar employing LMS adaptive spatial prediction is used to process against surface reverberation from the convergence zone (CZ). Hydrophones spatially separated from the primary array are used as references. The critical behavior exploited by the invention is that since the reverberation may be viewed as an extended source for the reverberation, the correlation drops off with separation between the reference and primary sensors, while it stays a constant for the plane wave target return. The reverberation is non-stationary, functionally dependent on the signal (even though the back scatter is statistically uncorrelated with the signal), and spatially extended over the sector of the CZ annulus cut out by the transmitter azimuth beamwidth. The detection of the target is based on the sudden appearance of one strong target point source within a densely packed region of weak point sources that have been constantly present and whose sum is much larger than the target. The use of more than a single reference leads to a minimal improvement in detection performance and may actually degrade performance due to increased algorithm noise. Detection performance tends to increase with increasing separation distance between the primary and the reference hydrophone. For signal, reverberation, and algorithm parameters consistent with modern active sonars operating in the CZ mode, the spatial prediction approach to detection of the plane wave signal will allow detection of targets not possible using conventional active processing, provided the reference hydrophone can be placed to give a correlation of less than 0.05. Such values may be obtained with very reasonable spacing between primary and reference, allowing the reference to be positioned, for example, along the hull aft of the primary array.
Abstract:
The invention concerns acoustic under-water measurement apparatus for determining the location with respect to a surface vessel of objects such as submersible vessels, pipe-riders, mining apparatus, or the like, including tethered submersible vessels. A receiver hydrophone set located on the tethered vehicle receives acoustic reply pulses from sea bottom transponders, telemetering the times of reception to a surface support ship via conductors in the tether cable. Signals obtained at the surface ship directly from the transponders and indirectly via the tether cable conductors are combined aboard the surface ship for computing the positions of both vessels with respect to a base line established by the sea bottom transponders. The system is self-calibrating, so that an expensive survey to determine the actual locations of the bottom transponders is no longer required.
Abstract:
In an apparatus for guiding or controlling a vessel over the center of an unmarked channel, a pair of ultrasonic transducers are mounted athwartship on the hull of the vessel and directed downwardly to transmit ultrasonic pulses and to receive corresponding pulses reflected from the floor of the body of water. Time durations between transmitted and corresponding received pulses are measured to determine floor or channel depth below the port and starboard sides of the vessel. The depths are digitally encoded and supplied to a comparator which generates a signal indicating whether deeper water is port or starboard of the vessel. The comparator signal is supplied to a display to instruct the navigator whether to steer port, starboard or to maintain course to guide the vessel over the center of the channel. The comparator signal may be also supplied to a rudder servo to automatically steer over the channel center. A digital filter is provided to eliminate any spurious readings obtained by the transducers.
Abstract:
A cylindrical array radiator that reduces the intensity of energy radiatedn undesirable directions. The radiator is constructed so that vertical staves placed on the face of a cylinder are staggered in the vertical direction by a predetermined distance to cancel energy in the undesirable directions.
Abstract:
The welding seam of a pipe is located by means of ultrasonic transducers and echo pulses responding particularly to rather minute distance differences on account of the convex contour of the seam and its elevation above the continued contour of the unmodified parts being welded together. A two or a three transducer configuration is used.