A model for diffraction halo in a speckle photographic record

A simple mathematical model for speckles, which are produced by a diffuse s urface and intercepted by the plane of a photographic plate, is proposed. I n this model, ail the speckles have the same form but are randomly distribu ted. The transmittance that would be produced when the plate is exposed is calculated. The reason for this model is that with only one postulate, repr oduces the basic speckle photography results and also allows to investigate the influence of the scanning beam in the diffraction halo. It is assumed that the plate is illuminated circular read-out beam and a formula is obtai ned for the intensity of the diffracted light in which a new expression app ears for the diffraction halo. The angular extent of the halo based on the dot size and the diameter of the laser beam is analyzed. Light and secondar y speckle (speckle noise) existence :inside and outside the classical halo cone is demonstrated. Tl-le theory is applied to the cases of an interrogat ion beam which is much larger or smaller than the speckle size, and to the case in which the beam is smaller but illuminates a sufficiently large numb er of speckles (intermediate case). The theory is verified with laboratory experiments.