A radial in-plane interferometer for ESPI measurement

This paper presents a new kind of double illumination interferometer used for true radial in-plane displacement measurement with electronic speckle pattern interferometry (ESPI). The basic principles, some characteristics and implementation details are discussed. Basic algorithms for displacement and strain measurements are presented and implementation details are given. A very robust and portable device was built using this new kind of interferometer to measure outside the optical bench This device has been successfully used for residual stress measurements in a very efficient way where the blind hole drilling technique is used in combination with the radial displacement field. Early results show a potential measurement performance comparable to the conventional blind hole method using strain gages. Measurement time is almost one order less than the strain gage based measurement system.