COHERENCE MODULATED ACOUSTIC SPECKLE INTERFEROMETRY

埋在海底岸边的复杂水雷对附近的任何船只都构成了威胁。它们的危险很大程度上来自于它们的伪装，因为它们存在于沙子中很容易被误认为岩石、珊瑚甚至人造物质。尽管现有的海底测绘技术很难探测到这样的水雷，但如果不发生错误的可能性很高。本报告设计并详细描述了一种表征这些物体的方法，以使探测成为可能。散斑干涉是一种光学过程，它允许分析物体的粗糙度。技术包括将物体暴露在激光下，然而，在海洋环境中，由于介质的不均匀性，光学识别方法是不可靠的。例如，小颗粒，密度和盐度的波动，或海洋生物。然后将该技术转换到声学环境中，在那里这种不均匀性障碍较小。其思想是从水下探测仪向目标物体发射声波，并使用传感器的线性阵列来记录其反射。阵列上的幅度变化，特别是由于信号的部分相干性引起的干扰特征，在阵列上的幅度变化，特别是由于信号的部分相干性而引起的干扰应该允许对反射表面的结构进行分类。在这种技术的设计中面临的一个挑战是确定区分给定表面所需的源信号。对于物体表面细节的分类，可能需要具有形状频谱的信号，其参数需要研究和确定。此外，还存在开发用于声表面反射的软件模型的问题，特别是当表面不规则并且源具有复杂的光谱结构时。本文件描述了该项目的研究计划，包括可以从中提取的当前工作。这包括作为博士学位的直接前身在该主题上所做的先前工作。这些计划对于开发软件工具和设计根据干涉图确定表面粗糙度的算法是过时的，该软件工具将对大部分研究具有重要意义，该算法基于类似的成图技术。

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.