Electronic speckle pattern interference (ESPI) experimental system makes use of speckle, which is the carrier of rough surface information, to study a substance. It is a modern optical measuring technique that covers image processing, laser technology, and holographic interference techniques. Thanks to the splendid coherence of lasers, the speckle is so obvious that it can be easily and clearly taken by a CCD camera, and then the data and image attained can be processed by a computer.