Light Scattering from Manufactured Surfaces

We present an evaluation of light scattering theories and experimental techniques for measuring the roughness of manufactured surfaces. Our goal was to define the ultimate capabilities and regions of validity of these methods for deducing surface microtopography. Available theories are evaluated in terms of a heuristic interpretation of direct electromagnetic scattering from surfaces. Experimental methods using specular reflectance, total integrated scatter, angular scattering distribution, and speckle are reviewed in terms of their spatial-bandwidth sampling of surface wavelengths and their roughness amplitude sensitivity and accuracy. Graphs in a slope/relative-wavelength space are used to intercompare the regions of validity of theories, regions of applicability for experimental methods and regions occupied by typical manufactured surfaces. A relatively unknown theory, valid for light scattering from many typical manufactured surfaces but previously unused for this purpose, is briefly described.