The range of speckle metrology

The range of four methods of speckle metrology as applied to in-plane displacement analysis is studied, in terms of the number of fringes that can be generated. Both quality and quantity of fringes are treated insofar as they affect the range and precision of the method. Some 20 variables are seen to influence the fringe range. A number of these are analyzed parametrically. The most serious restriction on the range seems to be the strain in the plane of analysis. This restriction severely limits application of the method.