1. Holography

1.1 Principle of optical holography

To fully grasp the concept of holographic interferometry, we first need to understand the process of recording and reproducing a light wave from an object, i.e. the process of holography. Here, we'll mainly be considering the case of three-dimensional solid objects that scatter the light they receive (relief objects most often encountered in industrial applications). But the case of transparent objects (used in fluid mechanics, for example) will also be addressed.

We'll see that recording the relief of an object involves recording the phase of the light wave that encounters the object. And recording the phase of a wave is done by interferometry, i.e. by superimposing a reference light wave on the wave coming from the object....