Real-time strain measurements by optical correlation.
Two optical correlation techniques for determining strain in materials are discussed. With the first method, strain is evaluated by measuring longitudinal variations in the separation between the object and the holographic filter. With the second method, a more direct determination of strain is made by simply measuring accurately the lateral displacement of two correlated areas. Experiments indicated that both methods have a sensitivity of about 10 ppm, with the potential of a slight further improvement.
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