Optical methods in experimental mechanics - Part 27: Speckle size estimates

Speckle patterns are created when coherent light is scattered by an object and made to fall directly or through a lens onto a sensing medium. The article deals with simple estimates of the size of the individual speckles as well as being of use in designing optical systems that uses speckle measurement which include a calculation that is based on oblique interference. All calculations of speckle size are approximations. The size of the speckles will vary over the field because of the variation of convergence angles for the waves coming from the extremes of the field. The difference of 22% between the Rayleigh criterion and the oblique incidence result is not important given the other indeterminacies present. And the recorded speckles can never be smaller that the resolution limit of the recording medium.