Three-dimensional displacement measurement by a holospeckle interferometry method

The three-dimensional displacement of a structure may be measured by holographic interferometry and speckle interferometry. Under the general heading of holographic interferometry a number of distinct techniques are possible. These include the zero-fringe method, which uses three separate holographic plates, the fringe-localization method, and the fringe-counting method, all of which require a complicated recording and analysis system and high stability. These requirements make the techniques unsuitable for use in most industrial settings. In this paper we present a holospeckle interferometry method that couples objective speckle and reflective holographic interferometry and that is capable of obtaining the three-dimensional displacement of an opaque object with good visibility and resolution by a single holographic plate. Being inexpensive and portable, the recording and analysis system can readily be adapted to industrial use.