Studies in speckle interferometry

Abstract

Initial studies were undertaken concerning laser speckle photography (sometimes called single-beam speckle interferometry) to obtain information about the technique and determine methods to enable specklegrams of high contrast and definition to be produced. This required extensive studies regarding the production, recording and processing of doubly exposed specklegrams corresponding to lateral surface displacements and investigation of the generation and measurement of the interference fringes from these specklegrams. It was discovered that marked improvements in fringe contrast and definition could be achieved using the measures and novel techniques which were devised. Information and evidence regarding the photography of these fringes was also obtained. The main studies built upon these findings and were concerned with the exploration and formulation of precise means of measuring fringes generated from doubly exposed specklegrams. Three possible techniques were identified and systems based on these were developed. One was based on the use of a self-scanning linear photodiode a ray, another on a computer controlled microdensitorneter system with digitized readout and computerized fringe analysis, and the third on a moire pattern technique. These techn­iques had not previously been explored in this connection, and valuable comparative information was also acquired.