Optical topometry of surfaces with locally changing materials, layers, and contaminations. Part 1: Topographic methods, based on two-beam interferometry

Abstract

Conventional topometry, applied to surfaces with locally changing materials can result in significant errors in the measured heights. A new theoretical approach is developed for the case of two-beam interferometry. Applied to some surface structures—gold on glass, oil on steel and SiO₂ on Si—important effects of contrast and phase variations are brought to attention. They are explained by a new theory using the complex contrast. Ways for surface correction procedures are outlined.