Whole Field Out-of-plane Vibration Analysis with a HOE-based ESPI System

Emilia Mihaylova, Dublin Institute of Technology
Viswanath Bavigadda, Dublin Institute of Technology
Raghavendra Jallapuram, Dublin Institute of Technology
Vincent Toal, Dublin Institute of Technology

Document Type Conference Paper

Proceedings of SPIE 7098 (2008) - Eighth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, Ed. E. P. Tomasini


Electronic speckle pattern interferometry (ESPI) is a full-field measurement technique, capable of displaying vibrational mode shapes. A simple optical set-up for an ESPI system using a holographic optical element (HOE) is presented. The HOE is designed to create a speckled reference beam in the interferometer. A partially reflective glass plate provides illumination of the object along the normal to its surface, ensuring that the system is sensitive only to out-of-plane displacement of the object. It is demonstrated that the HOE-based system can be used for vibration measurements. Phase shifting can be implemented for fringe analysis. A big advantage of the system is its simplicity. It requires a small number of components: a coherent light source, a holographic optical element, a glass plate and a CCD camera. Introducing holographic optical elements in ESPI gives the advantage of large aperture optical elements at relatively low cost.