Estimation of the 2D measurement error introduced by in-plane and out-of-plane electronic speckle pattern interferometry instruments

Optical interferometric metrology techniques are being increasingly used in industry. These techniques assure a greater accuracy in measuring displace ments caused by deformations. One such technique, electronic speckle patter n interferometry (ESPI), has been used successfully to measure in-plane and out-of-plane deformations. The usual model describing ESPI instruments beh aviour is only valid in or near the centre of the illuminated surface. In g eneral, this model is used as such for all the points on the surface creati ng thus an approximate figure of the reality. This study has led to an impr oved 3D vectorial model, allowing us to assess qualitatively and quantitati vely what is actually measured throughout all the inspected surface. Calcul ations with practical parameters taken from real ESPI instruments designed in the Joint Research Centre of Ispra (Italy) were carried out. The results showing three-dimensional diagrams of the measurement errors are presented and discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.