An image processing system for the analysis of speckle photographs

A fully automatic electro-optical system for measuring the displacement field from a double exposure speckle photograph is described. The optical processing section projects the power spectrum of a small region of the photograph onto a high quality image digitiser, based on a mechanically scanned photodiode array. The image is processed by microcomputer by transformation to the 2D frequency domain, where the displacement components are easily extracted. The accuracy and reliability achieved by these techniques are illustrated by typical experimental results.