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High accuracy full field three dimensional (3D) deformation measurements have always been an essential problem for the manufacturing, instrument, and aerospace industry. 3D deformations, which can be translated further into 3D strain and stress, are the key parameter for design, manufacturing and quality control. Due to the fast development of the manufacturing industry, especially in the automobile and airspace industry, rapid design and optimization concepts have already widely accepted. These concepts all require the support of rapid, high sensitive and accuracy 3D deformation measurement.
Advanced optical methods are gaining widely acceptance for deformation and stain measurement by industry due to the advantages of non-contact, full-field and high measurement sensitivity. Of these methods, Electronic Speckle Pattern Interferometry (ESPI) is the most sensitive and accurate method for 3D deformation measurement in micro and sub micro-level. ESPI measures deformation by evaluating the phase difference of two recorded speckle interferograms under different loading conditions. Combined with a phase shift technique, ESPI systems can measure the 3D deformation with dozens of nanometer level sensitivity. Cataloged by phase calculation methods, ESPI systems can be divided into temporal phase shift ESPI systems and spatial phase shift ESPI system.
This article provides a review and a comparison of temporal and spatial phase shift speckle pattern interferometry for 3D deformation measurement. After an overview of the fundamentals of ESPI theory, temporal phase-shift and spatial phase-shift techniques, 3D deformation measurements by the temporal phase-shift ESPI which is suited well for static measurement and by the spatial phase-shift ESPI which is particularly useful for dynamic measurement will be discussed in detail. Basic theory, brief derivation and different optical layouts for the two systems will be presented. The potentials and limitations of the both ESPI systems will be demonstrated by examples of precise and simultaneous measurement of 3D deformations under either static or dynamic loadings.
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