Analysis of sensitivity of the speckle interferometer to transversal or longitudinal displacements of plate surface, diffusively scattering light, is presented, when the Galilean telescope is used to record the specklogram. It is shown that the sensitivity of the interferometer to transversal displacement is defined by the radius of curvature of the spherical wave of radiation, illuminating the surface. The sensitivity of the interferometer to longitudinal displacement is defined by the scale of Fourier-transfer function characterized the complex amplitude of the reflection or the transmission of the surface scattering light. The experimental results are in agreement with theoretical arguments.
diffraction; interference; speckle; specklogram; spatial filter