Terry L. Henderson
Appl. Res. Labs., Univ. of Texas at Austin, Austin, TX 78713-8029
It is well known that the three-dimensional shell geometry of the visible portion of a distant hard-skinned sonar target can be scanned in xy coordinates by beamforming a planar array, with the associated z coordinates being provided by time gating the acoustic return. However, a simple line array running along the x axis can provide a projection view of the target, with its upper and lower surfaces being projected semi-transparently onto the xz plane, giving a picture analogous to that of a paramecium viewed with a slide microscope. If the line array is now tumbled in the xy plane, it will appear that the target is revolving around the z axis. When this tumbling view is presented 14(degrees) out of phase to the left and right eyes, a stereoscopic view of the tumbling target is obtained, thus revealing its three-dimensional form (with the aid of the brain's innate tomographic signal processing powers). Further simplifications of the array structure and processing are possible, with some limitations and weaknesses. A videotape of results for several targets has been prepared for presentation.