Sheareography - a Practical Optical Testing and Measuring Method

Shearography is a laser optical method which is suited for either nondestructive testing or for strain analysis. Contrary to holography which measures surfach displacements, shearography measures derivatives of surface displacements. Since strains are functions of displacement derivatives, shearography allows strains to be determined without numerical differentiating displacement data. Defects in object normally create strain concentrations; it is easier using shearography to correlate defects with strain anomalies rather than displacement anomalies applying holography. Furthermore, rigid body motions do not produce strain, thus shearography is insensitive against such motions and does not need adopting any particular device for vibration isolation. It is an industrial tool suited very well for the following ares:

1. strain measurement and strain analysis
2. nondestructive testing and quality assurance system
3. optimization ofmachine parts and structures of any material