A study of fringe clarity in laser interferometry and holography

Abstract

Many laser interferometers and holometers incorporate diffusing elements. The fringes obtained may have varying visibility and are accompanied by the speckle effect. The paper shows that fringe visibility may be re-defined so as to permit application of the same type of analysis as for incoherent light. The subjective clarity of the fringes, however, also depends largely on the speckle size relative to fringe spacing. The intermittency of the fringes is examined as an alternative criterion of clarity. Finally, an analysis is given of the fringe visibility and speckle size ratio likely to be obtained in three-dimensional holography of phase objects. The necessary limitations on the path variations within the object are examined, and the results confirm and extend those obtained previously by the author.