Family of novel compact and very simple electronic speckle pattern interferometers for out-of-plane and in-plane deformation measurements

Abstract

Electronic speckle pattern interferometry (ESPI) is a powerful tool for nondestructive testing of materials and products. Like holographic interferometry it allows to measure deformations and vibrations in the micrometer and submicrometer range. However current speckle pattern interferometers have rather complicated and expensive optical setups whose elements are aligned with difficulty. Moreover commercial ESPI devices lack flexibility in their optical setups. We present a family of flexible electronic speckle pattern interferometers for out-of-plane and in- plane deformation and vibration analysis which were quite recently developed at Laboratory of Technical Optics, Laser Techniques und Optoelectronics of Fachhochschule Ulm. Their common properties are: extreme simplicity and compactness of the optical setups due to the use of transmission or reflection HOEs or other very small, simple diffusers and a compact laser; very effective usage of laser radiation; no need of sophisticated vibration insulation; alignment easily performed without requiring high accuracy; simple intensity matching of ESPI object and reference waves; optically skulled personnel is not required for ESPI operation and device maintenance; and very low costs of the optical setups. Due to simplicity, compactness and low costs the introduced devices are ideally suited for industrial automated inspections. Extensive experimental results are given which were obtained with the novel ESPI devices.