Utilisation des franges d'interference en lumiere diffuse pour l'etude de l'etat de surface d'un diffuseur

Abstract A diffuser, illuminated successively by light of two neighbouring wavelengths, produces on a photographic plate placed in a parallel plane two intensity distributions which are homothetic except for certain decorrelation terms. This homothecy (scale variation) can be compensated by a longitudinal displacement of the photographic plate between the two exposures and consequently, the decorrelation depends only on the structure of the diffuser. Under these conditions, if the photographic plate is given an additional displacement in its own plane between the two exposures, the contrast of Young's fringes obtained in the Fourier plane characterises the roughness of the diffuser.