COHERENCE MODULATED ACOUSTIC SPECKLE INTERFEROMETRY

埋在海岸线海床上的精密水雷对附近的任何船只都构成了威胁。它们的危险主要来自于它们的伪装，因为它们在沙子中的存在很容易被误认为是岩石、珊瑚甚至人造材料。尽管有着雄辩的海底测绘技术，要探测这样的地雷而不出现高概率的假阳性是很困难的。散斑干涉法是一种分析物体粗糙度的光学方法。该技术涉及将物体暴露在激光下，如果其反射散射和干涉自身，则可以对其表面纹理进行表征。然而，由于介质的不均匀性，光学识别方法在海洋环境中是不可靠的，例如，小颗粒，密度和盐度的波动，或者海洋生物。然后，这项技术被应用到声学领域，这样的不均匀性就不会成为障碍。其原理是从水下探测器向目标物体发送声波，并使用传感器的线性阵列记录其反射。阵列上的振幅变化，特别是由于信号的部分相干性引起的干扰，应该允许对反射表面的结构进行分类。在这项技术的设计中面临的一个挑战是，最重要的是确定用于区分给定表面所需的源信号。对于物体表面上的较细细节的分类，具有成形频谱的信号可能是必要的，其参数需要调查和确定。除此之外，还存在开发声表面反射的软件模型的问题，特别是当太阳本文介绍了该项目的研究计划，包括目前的工作，从中可以绘制。这包括之前在该主题上所做的工作，作为博士学位的直接前任该计划概述了开发的软件工具，这将是重要的研究，并设计的算法来确定表面粗糙度的干涉图的基础上类似的技术用于映射。

Sophisticated mines buried in the sea bed on littoralcoast lines pose a threat to any vessel in the vicinity.Their danger comes largely with their camouflage, astheir presence in the sand could easily be mistaken fora rock, coral or even man made material.Despite elo-quent seabed mapping techniques, it is difficult to detectsuch a mine without having a high probability of falsepositives.A method of characterising these objects inorder for detection to be made possible is devised anddetailed in this report.Speckle interferometry is an optical process that al-lows the analysis of an object's roughness.The tech-nique involves exposing the object to a laser, and if its re-flection scatters and interferes with itself, a characterisa-tion can be made on its surface texture.However, opticalmethods of identification are unreliable in ocean envi-ronments due to inhomogeneities in the medium.For ex-ample, small particles, fluctuations in density and salin-ity, or sea life.The technique is then translated into anacoustic context, where such inhomogeneities are lessof an obstacle.The idea is to send a sound wave froman underwater sounder to a target object and record itsreflection using a linear array of sensors.The variationin amplitude over the array, particularly the interferencepatterns due to the partial coherence of the signal, shouldallow a classification of the structure of the reflectingsurface.A challenge which is faced in the design of this tech-nique is determining the source signal required for thedistinction of given surfaces.For the classification offiner details on the object surface, a signal with a shapedspectrum may be necessary, for which the parametersneed to be investigated and determined.Further to this,there is the problem of developing a software model foracoustic surface reflections, particularly when the sur-face is irregular and the source has a complex spectralstructure.This document describes the plan of research for thisproject including the current work from which can bedrawn.This includes previous work done on the topicas a direct predecessor to the Ph.D. The plans are out-lined for developing the software tool, which will beimportant for much of the research, and designing thealgorithms for determining surface roughness from theinterferograms based on similar technologies used formapping.