Electro-optical read-out system for analysis of speckle photographs (A)

An electro-optical read-out system for measuring displacement and strain fields from a double exposure speckle photograph is described. The optical system uses a cylindrical element to project the 1-D Fourier transform cylindrical element to project the 1-D Fourier transform from a point on the photograph on to a self-scanning linear photodiode array, with minimal distortion of the spacing of the fringe pattern. The output from the array is processed electronically and fed to a computer which calculates displacements and strains. Experimental results obtained with a partially automated system show the accuracy and reliability achieved.