1J6-1 合成開口ソーナーによる堆積層内埋没物の画像化(水中音響)

概要

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We investigate the use of Synthetic Aperture SONAR (SAS) for the buried object imaging. In the sediment, the sound wave is strongly refracted because the sound speed is distributed by layer. The refraction causes the time shift Δt in the received acoustic signal, then the SAS image is distorted. First, we examined the effects of Δt on SAS image. We calculated sound wave in the sediment layer using Biot-Stoll model. The Δt calculated is applied to the ping signal of the receiver. After the synthetic aperture process, the resolution of the image is quantified for different types of sediment porosity β. Second, a compensation technique is proposed. The technique enhances the contrast of buried object in SAS image by giving error amount Δt as time delay in the SAS process. The results of the application of the technique reveals that the improved SNR (Signal to Noise Ratio) is more than 20dB.
2009-11-18