Speckle interferometry with temporal phase evaluation: Optimization of imaging apertures for in-plane displacement

Recently a new method to measure object shape and deformation using tempora l evolution of speckles in speckle interferometry was reported. The princip le, behind the method is that certain parameter sensitive to shape or defor mation is changed continuously and the fluctuations in the intensity of the speckles are recorded in a large number of frames. The phase data for the whole object deformation is then retrieved by inverse Fourier transformatio n of a filtered spectrum obtained by Fourier transformation of the signal. In this paper a theoretical evaluation of the amplitude of the signal for i nplane sensitive interferometer that uses dual beam illumination is present ed. It is shown that signal to noise ratio is better when the speckle size is smaller than the pixel size contrary to the normal assumption that the s peckle size be matched to the pixel size.