The contrast variation of polychromatic speckle patterns at the far-field diffraction plane

Abstract

The contrast variation of polychromatic speckle patterns at an arbitrary point of the far-field diffraction plane is studied theoretically and experimentally. Gaussian statistics are assumed for the formation of speckles. The average contrast of speckle patterns at the far-field diffraction plane is actually theoretically evaluated and experimentally measured for diffuse objects having a wide range of surface roughnesses under illumination of the polychromatic Gaussian laser beam. This contrast is found to depend strongly on the surface roughness of objects, the number of scattering cells within an illuminated area over the object, and a radial distance from the center of the far-field diffraction plane. Good agreement between the theoretical and experimental results is confirmed.