Study on the correspondence between random surface topography and its interface speckle field

Abstract

Extracting the information of a random surface based on its speckle field is an important part of non-destructive measurement. To the best of our knowledge, few have emphasised the correspondence between the topography of a random surface and its speckle field. In this paper, Finite Difference Time Domain (FDTD) Solutions software is used to calculate the speckle field at the position of the maximum height of a random surface, called the interface speckle field. An interface speckle field is also extracted experimentally. The results are consistent with the theoretical calculations. The correspondence between the physical quantities of the interface speckle field and the topography of the random surface and the influence of various factors on the correspondence are discussed in detail. Studies indicate that when the lateral correlation length of random surfaces or the wavelength of incident light increases and the roughness or the refractive index of the random surfaces decreases, the correspondence improves. The topography of a random surface is almost identical to the phase distribution of its interface speckle field when its refractive index is small or its roughness is on the order of nanometres.