Measurement of Absolute Three-dimensional Displace-ment Gradients Using Tri-color Quad-beam Digital Shearography

Abstract:

A tri-color quad-beam digital shearography is proposed to achieve the measurement of absolute three-dimensional dis-placement gradients. Four laser beams with three different center wavelengths are symmetrically irradiated to the object surface from the upper and lower left and right directions. Four phase maps are then extracted from the two inter-ferograms obtained from two shots. Based on these four phase maps, the absolute three-dimensional displacement gra-dients are determined. This means of absolute three-dimensional displacement gradient measurement effectively improves the measurement capability of digital shearography and expands its application range.

Key words:Digital shearography; displacement gradient; absolute phase; spatial carrier; speckle interferometry