P1 - Combined ESPI and Digital Speckle Correlation Techniques for 3D Displacement Field Measurement

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings OPTO 2011
OP - Poster Session
O. Sakharuk, L. Muravsky, A. Kmet, T. Voronyak, O. Maksymenko - Karpenko Physico-Mechanical, Lviv (Ukraine)
106 - 110


We have created the setup for determination 3D surface displacements and deformations by combined technique when out-of-plane deformations were measured by the phase shifting speckle interferometer and in-plane deformations - by using the interferometer object wave the digital speckle correlator (DSC) using only the interferometer object wave. The phase-shifting interferometer is based on scheme for z-component
determination by one step phase shift of reference wave on arbitrary unknown angle. The procedure for out-of-plane deformation determination consists in the next: two speckle interferograms and two speckle images
are recorded before specimen deformation and two speckle interferograms and one speckleimage after and further processed by algorithm. During experiment we have studied the metal specimen surface area of 14,7x11 mm² near stress concentrator. Recorded speckle-patterns were 800x600 pixels. Though the sensitivity of interferometer for z-displacement measurements was 0,32 µm. To realize Digital Speckle Correlation algorithm, we record speckle-images of specimen surface in the initial state and loaded state after shut down of reference wave by electromechanic shutter. Received images were divided into subimages with dimensions 16x16 or 32x32 pixels and correlation of appropriate pairs of subimages was performed. In order to harmonize calculated z (received by phase shifting interferometer) and xy displacement (received by correlator) we have performed interpolation of xy displacement results.
We have shown advantages of ESPI and DSC combined use as the Digital Speckle Correlation algorithm allow us to widen range of measured displacements by phase correction in ESPI. From the other side, use of ESPI for determination of out-of-plane displacements is very effective as DSC sensitivity for out-of-plane displacements is very low.