Additive-subtractive phase-modulated shearography with synchronized acoustic stressing

T. C. Chatters*, B. F. Pouet, S. Krishnaswamy

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


A robust electronic shearography technique is described that is immune to ambinet noise. In this technique, additive speckle-interference images containing information about the same two states of deformation of a test object undergoing acoustic stressing are acquired in each video frame. When a spatially nonuniform phase modulation is introduced in every other frame during the video sequence (using a tilting mirror) and the additive interference images are subtracted sequentially using a real-time image processor, the self-interference component of sheared-speckle interference pattern is removed. The susceptibility of this method to environmental noise caused by induced thermal noise and low frequency vibration is demonstrated to be lower than that of conventional substractive shearography methods; fringe visibility and contrast are significantly improved as well. The ability of this technique to work in a turbulent environment is demonstrated, and application to detection of structural defects in adhesively bonded structures, a problem of interest in nondestructive evaluation of structures, is shown.

Original languageEnglish (US)
Pages (from-to)159-165
Number of pages7
JournalExperimental Mechanics
Issue number2
StatePublished - Jun 1 1995


  • additive interferometry
  • nondestructive evaluation
  • phase modulation
  • shearography
  • subtractive interferometry

ASJC Scopus subject areas

  • Aerospace Engineering
  • Mechanics of Materials
  • Mechanical Engineering


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