Recent Developments on Speckle Pattern Correlation by Photographical Means

Abstract

Correlation Techniques between a speckle pattern and its photographic negative are useful for measuring in real time displacements⁽¹⁾, vibrations⁽²⁾ and the state of deformation of rigid objects during fatigue testing^{(3) (1)}. A similar technique is to use the photographic record of the process to analyze the fringe visibility of the diffraction pattern. One aditional system is necessary in this case and some errors are introduced due to the halo effect. The capability of real-time observation is, however, lost; sometimes requiring the making of many photographic frames. The photodetection and subsequent electronic processing of the signal is in current use, although it does not achive the resolution and simplicity of the photographic systems.