Skip to main content
Article thumbnail
Location of Repository

Single-axis combined shearography and digital speckle photography instrument for full surface strain characterization

By Roger M. Groves, S. Fu, Stephen W. James and Ralph P. Tatam

Abstract

Full characterization of the surface strain requires the measurement of six displacement gradient components of the surface strain tensor. The out-of-plane displacement gradient component may be directly measured using the full-field speckle interferometry technique of shearography, but to fully characterize the surface strain using shearography, a minimum of three illumination, or viewing, directions are required. The image processing technique of digital speckle photography (DSP) is sensitive to in-plane displacement for normal collinear illumination and viewing, with the displacement gradient components obtained by differentiation. A combination of shearography and digital speckle photography is used to perform full characterization of the surface strain using a single illumination and viewing direction. The increase in complexity compared with a standard single-channel shearography system lies predominantly in the additional image processing requirements. Digital speckle photography image processing is performed using the optical flow field technique and the advantages of this technique compared with correlation are discussed. The design of the instrument is described and full surface strain measurements made with the system are presented

Topics: strain measurement limited optical access shearography digital speckle photography field-measurements image-correlation displacement interferometry algorithm
Publisher: Spie -- the Int Soc for Optical Engineering
Year: 2005
DOI identifier: 10.1117/1.1842779
OAI identifier: oai:dspace.lib.cranfield.ac.uk:1826/5720
Provided by: Cranfield CERES
Journal:

Suggested articles

Citations

  1. (1973). An image-shearing speckle pattern interferometer for measuring bending moments,’’ doi
  2. (1983). Determination of displacements using an improved digital correlation method,’’ doi
  3. (1992). Optimal sampling and range of measurement in displacement-only laser-speckle correlation,’’ doi
  4. Shearography: a new optical method for strain measurement and nondestructive testing,’’ doi

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.