Acoustical Camera with Interferometer Mode. A number P of image planes 25 defining a first layer of the volume of interest in the vicinity of the target area are range-gated from this single pulse return, processed, stored and multiplexed out from the array 21 to the image-rendering engine On the next pulse, the range gates are delayed to provide the next P planes of data, thereby defining a second layer just beyond and adjacent to the first layer.
The image discriminator module 26 can then analyze the three dimensional volumetric images for evidence of buried objects based on detectable relative movements e. Thus, with a x receiver array and only 10 pings, an entire xx80 volume of information is received, corresponding to the volume of interest in the target area.
Processing of the volume of information will enable a determination of the presence of a buried object in the volume of interest, indicated in Figure 3 by the three dimensional volumetric image The acoustic lens 27 is approximately seven inches in diameter, and ' forms images on the x receiver array, which can be comprised of, for example, piezocomposite, acoustical transducer elements. For example, acoustic transducer elements other than piezocomposite, such as electrostrictive or magnetostrictive, can be used here as well. Also, the array 21 may be configured as a receive array only.
In such an embodiment, the transmitted pulses can be provided by an external transducer or other acoustical source. The array 21 and lens 27 sizes will vary depending on factors such as desired resolution, range of the imaging system, and the FOV 7 size. For example, the engine 23 may generate two-dimensional images, which are provided to a 3- D image formation module e.
Table 1 provides the characteristics of an acoustical camera 1 in accordance with one embodiment of the present invention. At a 13 foot range, for example, a 3x3x2. Table 1. Note that other camera configurations can be used here as well, and the present invention is not intended to be limited to any one such embodiment.
For example, the upper end of the range may be lower e. Likewise, the frame rate may be lower e. Similarly, the xy resolution, pixel count, number of range planes, and lens diameter can all be varied depending on the application and the desired performance. As can be seen in this example, the received echo waveform from the target area including any objects within the FOV 7 is sampled at four times per cycle i. The in-phase I and -I samples 35 and 39 and quadrature Q and -Q samples 37 and 41 are separately and simultaneously sampled, averaged, and recorded for each of the pixels in the array 21 by the array 21 16, pixels, assuming a x array.
Acoustical Near-Field Imaging
Three-dimensional information is preserved from the range planes of which there are 80 for the example camera configuration of Table 1 by detecting the first plane in which there is an echo from the exterior surface of the object. The magnitude of the signal together with the plane in which it occurred is used by the image-rendering engine 23 to form a pseudo-three dimensional volumetric image. The formed three dimensional images can the be displayed or otherwise analyzed e.
Here, surface objects 60 and 62, as well as contour lines of the underwater floor, are present in the image. The waveforms 50a and 50b indicate displacement associated with application of an acoustic vibratory pulse e. The interferometer mode of the acoustical camera 1 uses waveform sampling to differentially measure displacement of objects by comparing the phase of the echo signal at each of the pixels e. The image-rendering engine 23 can be configured to make this comparison. Alternatively, the controller 17, can be configured to make the comparison based on sampled data provided by the camera 1.
Note that this displacement is measured simultaneously and independently for each pixel. The frequency of sampling may be adjusted as needed.
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For instance, higher order sampling be used in alternate embodiments to improve the accuracy of the phase measurements. The acoustical frequency and intensity are selected to provide displacement of the floor 9 sufficient for the imaging interferometer camera 1 to detect the motion. The frequency and intensity of the low frequency vibratory energy may be varied according to the materials of the underwater floor and the resolution capabilities of the imaging interferometer.
With reference to Figure 6, comparison of pixels from a first image 50a and second image 50b show pixels that have had little or no displacement, such as objects 60 and Larger displacements are attributed to the mobility of the water-saturated silt or sand floor materials Intermediate displacement occurs in the region surrounding buried object 68, as well as the regions surrounding partially buried objects.
However, man-made objects of interest generally have geometrical shapes, which will be apparent in the images. As such, an operator viewing the images on a display, for example, could discern man-made objects from natural objects. Alternatively, there may be an algorithm programmed to comparing the first and second images for evidence of movement of floor materials relative to the non-movement of objects detected between the first and second images. Numerous conventional pattern recognition schemes or other comparative algorithms can be employed here, thereby enabling differences between the images to be resolved.
It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.
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Techniques for underwater detection of fully or partially buried objects such as sea mines and underwater cables are disclosed. An acoustical camera produces three dimensional volumetric images of a target area volume of an underwater floor. One or more first images are produced of the target area volume.
An acoustical transducer pulse is then directed to the target area volume so as to disturb the loose particulate or elastic matter included in the target area. One or more second images are then produced while the pulse is present in the target area volume. The images can be compared for evidence of buried objects, or to otherwise evaluate objects included in the target area.
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The camera can be configured with an interferometer mode so as to produce volumetric images at a real time frame rate. Figure 1 provides a diagrammatic presentation of the relative turbidity versus resolution potential of conventional sonar, acoustical and optical imaging systems,  Many sea mines are designed to progressively bury themselves through the scouring action of water movement on the seafloor. Acoustical Imaging Interferometer System  Figure 2 is a diagrammatic depiction of a system for detecting buried underwater objects configured in accordance with one embodiment of the present invention.
Acoustical Camera with Interferometer Mode  Figure 3 is a perspective view of an array and lens component of an acoustical camera for use in the system of Figure 2, and configured in accordance with an embodiment of the present invention. Acoustical imaging has become an indispensable tool in a variety of fields. Since its introduction, the applications have grown and cover a variety of techniques, producing significant results in fields as disparate as medicine and seismology.
Cutting-edge trends continue to be discussed worldwide. The Symposium belongs to a conference series in existence since During two well-attended workshops the applications of quantitative acoustical imaging in biology and medical applications, and in near-field imaging of materials, were discussed.
Based on its cross-disciplinary aspects, the authors of the papers of AI27 present experiments, theory and construction of new instruments. Du kanske gillar.lorestloundeckheart.tk
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