Méthode de traitement des interférogrammes á deux ondes pour accroître leur sensibilit&eacute

A process for increasing the sensitivity of two-beam interferometry to wave surface deformations on a scale less than half the wavelength is presented. The method consists of comparing a signal proportional to the intensity of the interferogram at each point with a series of discrete reference signals varying according to the illumination of the interferogram as a function of phase, allowing the inclusion of several intermediate fringes varying linearly in terms of phase between the brightness extrema of a fringe. The resulting interferogram can then be analyzed optoelectronically by an image dissector tube or a flying-spot scanner. Examples of the use of these techniques at resolutions of 1/50 and 1/16 wavelength are presented. Applications of the method, which is simple to employ and provides fast visual results, in the study of material homogeneity defects and elasticimetry as well as interference strioscopy, microinterferometry and polarimetry are pointed out.