Citation:
Roger M. Groves, Stephen W. James and Ralph P. Tatam. Multi-component shearography using optical fibre imaging-bundles. Proceedings of the SPIE Optical Measurement Systems for Industrial Inspection III. Monday 23 June 2003,
Munich, Germany. Volume 5144, 513. Eds. Wolfgang Osten, Malgorzata Kujawinska, Katherine Creath
Abstract:
Shearography is a full-field non-contact optical technique usually used for the
investigation of defects in nondestructive testing. In shearography
interferometric speckle patterns recorded before and after object deformation
are correlated, often by subtraction, to yield correlation fringes sensitive to
displacement gradient, a parameter closely related to surface strain.
Shearography is sensitive to the component of displacement gradient that is
determined by the direction of the illumination and viewing directions, the
optical wavelength and by the magnitude and direction of the applied shear. To
perform a multi-component measurement requires illumination, or viewing, from a
minimum of three directions, followed by a coordinate transformation to obtain
the in-plane and out-of-plane displacement gradient components. This would
normally require the use of either multiple optical sources or multiple
interferometer heads and multiple cameras. In this paper the authors use a
single laser source, a single interferometer head and camera, with four views of
the object ported from the camera lenses to the interferometer using a four-leg
optical fibre imaging bundle. This approach allows four components of
displacement gradient to be recorded simultaneously. Experimental results from
the multi-component shearography instrument are presented.