全息干涉与散斑干涉综述

全息干涉与散斑干涉技术综述报告

全息干涉无损检测技术是无损检测技术中的一个新分支，它是20世纪60年代末期发展起来的，是全息干

涉计量技术的重要应用。

我们知道结构在外力的作用下，将产生表面变形。若结构存在缺陷，则对应缺陷表面部位的表面变形与

结构无缺陷部位的表面变形是不同的。这是因为缺陷的存在，使得缺陷部位的结构的刚度、强度、热传导系

数等物理量均发生变化的结果。因而缺陷部位的局部变形与结构的整体变形就不一样。应用全息干涉计量技

术就可以把这种不同表面的变形转换为光强表示的干涉条纹由感光介质记录下来。

而激光散斑技术是在激光全息实验中，我们观察被激光所照射的试件表面，就可以看到上面有无数的小

斑点，因而观察不到条纹，因此在前期，散斑是被看作是噪声来对待的，直到随着人们对全息干涉技术的进

一步了解，才发现虽然这些斑点的大小位置都是随机分布的，但所有的斑点综合是符合统计规律的，在同样

的照射和记录条件下，一个漫反射表面对应着一个确定的散斑场，即散斑与形成散斑的物体表面是一一对应的。在一定范围内，散斑场的运动是和物体表面上各点的运动一一对应的，这就启发人们根据散斑运动检测，来获得物体表面运动的信息，从而计算位移、应变和应力等一些力学量。

因此全息和激光散斑方法由于其固有的高灵敏度，在非破坏性测试领域发现了越来越多的应用。可探测

到表面及地下的裂缝、空洞、脱层和分层等缺陷。由于这些方法测量了在外部加载或其他条件的影响下，在

这三个维度下研究对象的变形，它们也可以用于质量控制，也可以用于设计阶段。激光散斑的方法，还利用

了电子检测和处理的发展(称为电视全息术)，并可用于实时定量评价。本综述报告主要介绍利用光纤光刻技术，对全息和激光散斑测量方法进行了全面的研究，这两种方法都适用于焊接、复合材料的检验。

Introduction

Holography is a two step process of recording a wavefront

and then reconstructing the wave. While Holography is often

used to obtain the recreations of beautiful 3-dimensional scenes,

there are several engineering applications, the most common and

important one being Holographic Non-Destructive Testing . This

is accomplished with holographic interferometry, wherein

interferometry is carried out with holographically generated

wavefronts .

A speckle pattern is generated when an object with a rough

surface is illuminated with a highly coherent source of light

such as laser. Initially this speckle noise was considered as

the bane of holographers, until it was realized that these speckles

carry information about the surface that produce them. Again,

as in the case of holography, the combination of interferometric concepts with speckle pattern correlation gave rise to speckle interferometry . The developments in electronic detection and processing further added wings to laser speckle methods giving rise to Electronic Speckle Pattern Interferometry (ESPI), or “TV Holography”. This paper describes a brief outline of holographic and speckle methods for Non-Destructive Testing applications, wherein the deformations of an object under load are measured in a non-contact way. Measurement of surface shapes using contouring and derivatives of displacement using Shearography are also presented.

1.Holography

The schematic for recording a hologram is shown in Fig.1. The light from a laser is split into two beams. One beam illuminates the object and the other beam is used as a reference. At the recording plane, an interference of the

Fig. 1 : Experimental arrangement for recording a hologram. wavefront scattered by the object with the reference wavefront takes place. A recording is made on a high resolution photographic plate. The developed plate, now called a “Hologram”, when illuminated by the reference wave, reconstructs the object wave. There are several recording geometries such as in-line, off-axis, image plane, Fourier Transform, reflection and rainbow holograms. The theory behind the recording and reconstruction of object wavefront is well documented .

1.1Holographic Interferometry (HI)

While holography is used to obtain recreations of beautiful 3-D scenes, most engineering applications of holography make use of its ability to record slightly different scenes and display the minute differences between them. This technique is called Holographic Interferometry (HI). Here