Nano-roughness measurements with a modified Linnik microscope and the uses of full-field heterodyne interferometry

Abstract

A collimated heterodyne light enters a modified Linnik microscope, and the full-field interference signals are taken by a fast CMOS camera. The sampling intensities recorded at each pixel are fitted to derive a sinusoidal signal, and its phase can be obtained. Next, the 2-D phase unwrapping technique is applied to derive the 2-D phase distribution. Then, Ingelstam's formula is used to calculate the height distribution. Last, the height distribution is filtered with the Gaussian filter, the roughness topography and its average roughness can be obtained and its validity is demonstrated. (c) 2008 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3050357]