A combination optical method of lateral shearing interferometry and caustics

S. Prabhu, J. Lambros

Research output: Contribution to journalArticlepeer-review


A novel experimental technique is presented that combines the optical method of caustics and the full-field lateral shearing interferometer of coherent gradient sensing (CGS) in one setup. Collimated light transmitted through a deformed specimen is separated into two legs. One is processed by the lateral shearing interferometer and is recombined with the other on a single image plane. By adjusting the optical path length of each leg, a combination lateral shearing interferogram/caustic image is generated. When this technique is applied to a fracture specimen, information about the stress intensity factor can be obtained from the caustic and the CGS interference fringes for exactly the same deformation field. This allows for a direct comparison between the two methods when investigating phenomena such as K-dominance, three-dimensional deformation and so on. In this paper, the technique is presented in detail, and its feasibility is tested by application to mode I and mixed-mode crack tip deformation fields.

Original languageEnglish (US)
Pages (from-to)376-383
Number of pages8
JournalExperimental Mechanics
Issue number4
StatePublished - 2000
Externally publishedYes


  • Bifocal caustics
  • Combination optics
  • Fracture
  • Interferometry
  • Lateral shearing

ASJC Scopus subject areas

  • Aerospace Engineering
  • Mechanics of Materials
  • Mechanical Engineering


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