Michelson interferometer based spatial phase shift shearography

Abstract

This paper presents a simple spatial phase shift shearography based on the Michelson interferometer. The Michelson interferometer based shearographic system has been widely utilized in industry as a practical nondestructive test tool. In the system, the Michelson interferometer is used as a shearing device to generate a shearing distance by tilting a small angle in one of the two mirrors. In fact, tilting the mirror in the Michelson interferometer also generates spatial frequency shift. Based on this feature, we introduce a simple Michelson interferometer based spatial phase shift shearography. The Fourier transform (FT) method is applied to separate the spectrum on the spatial frequency domain. The phase change due to the loading can be evaluated using a properly selected windowed inverse-FT. This system can generate a phase map of shearography by using only a single image. The effects of shearing angle, spatial resolution of couple charge device camera, and filter methods are discussed in detail. The theory and the experimental results are presented.

Digital Shearography for NDT: Phase Measurement Technique and Recent Developments

“…Both the Mach-Zehnder-based SPS-DS system and double-aperture SPS-DS system have the disadvantage of limited measurement area. A Michelson-based SPS-DS system also exists, which can be used to obtain a larger measurement area by embedding the 4f system [33,34]. The SPS-DS system with a 4f system is shown in Figure 8a.…”

EXTREME shearography: development of a high-speed shearography instrument for measurements of the surface strain components during an impact event

“…Temporal phase shifting and the shear are performed using a three coordinate piezo-electric actuator PSH 4z by Piezosystem Jena which is used in the shearing arm of the interferometer. The spatial phase shifting is based on a 4f system (two 50 mm Xenoplan lenses by Schneider) with a 0.4 mm slit in front of the imaging lens to achieve a better quality of the phase maps in comparison with a circular aperture 42 .…”

Review of recent developments of spatial phase-shift digital shearography

“…To increase the stability of SPS-DS system and overcome the small measurement size limitation, X. Xie et al introduced a single aperture Michelson Interferometer based spatial phase-shift Shearography in 2013 [8]. Fig.…”

“…This system provide a much better phase map quality, however, the measurement size is still limited and the system is not convenient for universal applications, because for each specific test object, the mask has to be designed specifically to avoid spatial frequency aliasing. In 2013, Xin Xie et al introduced a single aperture spatial phase-shift shearography system based on Michelson interferometer [8,9]. In this setup, a 4f system is introduced to enlarge the field of view, and free the measurement field size of shearography system from the limitation of the beam splitter size.…”