Book Description

The aim of the work reported in this thesis is to develop a simple electronic speckle pattern interferometry (ESPI) system by combining holographic optical element technology with speckly interferometry. A holographic optical element is used in an ESPI system instead of the lenses, mirrors, beam splitters and beam combiners which are usually required in a conventional system. The final ESPI system consists only of a single holographic element, laser and CCD camera. Many currently available systems are complicated and consist of expensive optics that can be difficult to align. Even the simplest require several conventional optical elements to manipulate the laser light and provide the necessary object and reference beams. In this thesis holographic optical element technology is combined with speckle interferometry in order to make a simple, compact and low cost ESPI system. A compact ESPI system is built by incorporating a single holographic optical element, which generates a specked reference beam and combines this with the object wavefront as it approaches the camera. In addition, a dual interferometer was constructed with a facility to test an object using both ESPI and holographic interferometry. In this way the advantages of high quality interference fringes in holographic interferometry, speed and convencience of ESPI can be exploited. Firstly, the use of a self developing holographic recording material allowed live holographic interferometry to be carried out, and viewed with a CCD camera. It was then shown that the recorded hologram could be used, with no further adjustment, to provide a speckle reference beam to the camera, so that ESPI could be performed in the same optical set up. The out of plane deformation of the object was studied with the two techniques in one interferometer and results were presented. The self developing acrylamide based photopolymer used was a holographic recording material formulated and prepared at the Centre for Industrial and En.