Extraction Of Parameters Of Anisoropic Random Surfaces From The Scattering Profiles Of Light Intensity Using Fourier Transformation

The random surfaces as important parts make up of nature and random surfaces as well as their scattering light measurements are of great importance in many scientific and technological fields such as material growth, precision machining and medicine diagnosis etc. The study of optical fields scattered from random surfaces is the main content of statistical optics, so many people have payed attention to studying about random surfaces for a long time. The surface model of the self-affine fractal is demonstrated to be more adequate for the comprehensive description of a wide category of random surfaces at present. Besides the traditional parameters of root-mean-square roughness w and correlation lengthξ, a new parameter of the roughness exponentαis introduced in this model to characterize the short-range fractal properties of the surfaces.The paper calculate the curve of the scattered light and lay out a new way to measure scattered profiles according to Kirchhoff's diffration theory. We also measured the light intensity scattered from Si(100) wafer by The average technique with gated integration and then analyze the scattering profiles of light intensity quantificationally using self—affine fractal surface model and inverse Fourier transformation ,and determinate there parameters of anisotropy surface, compare with the data obtained from AFM and verify that parameters are correct. We can determine the anisotropic random surfaces using Fourier transformation. The main contents and results of this thesis can be summarized as follows.Chapter 1 gives a summary and review of the description of random surfaces and its measurements.In chapter 2 We introduce the theory of self—affine fractal surface model, discuss the approximate calculation of the scattering light intensity and how to attain the parameters of random surfaces.In chapter3,We discuss the scattered light properties of self—affine fractal surface model. In the experiment to measure the light scattering from the reflection-mode random surface, we adopt the roughness backside of Si(110) wafer as the sample of self-affine fractal random surface. CCD detects the light intensities scattered from the sample surface at the incidence angles of the 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 83°and 85°. The scattering light intensity profiles at different incident angles are calculated by the symmetric decline function in mathematics.In chapter4,the scattering profiles of light intensity quantificationaly using self—affine fractal surface model and inverse Fourier transformation and parameters of anisotropy surface are determined. Comparing with the data obtained from AFM, We verify that parameters are correct.In chapter 5,we give the summary of this paper and put forward the further goal.