Wittelichtsinterferometrie

Wittelichtsinterferometrie, also known as white light interferometry (WLI), is an optical measuring technique used for precise surface characterization. It relies on the interference of light waves from a broadband source, typically white light, to measure surface topography and height differences. Unlike monochromatic interferometry, which uses a single wavelength of light, WLI exploits the fact that white light contains a spectrum of wavelengths.

The principle behind WLI involves splitting a beam of white light into two paths. One path is directed towards the surface being measured, and the other path serves as a reference. When the light beams are recombined, they interfere. The key feature of WLI is that constructive and destructive interference only occur over a very narrow range of optical path difference due to the broadband nature of the light. This limited range of interference allows for the determination of the exact position where the two light paths have equal optical path length.

By scanning either the sample or the reference mirror through this interference region, a detector can record the intensity variations. The point of maximum fringe contrast, or the white fringe, corresponds to zero optical path difference. By analyzing the position of this white fringe relative to the reference path, the height or profile of the measured surface can be accurately determined with sub-nanometer resolution. WLI is a non-contact method and is widely used in fields such as semiconductor manufacturing, optical metrology, and materials science for defect detection, surface roughness measurement, and dimensional analysis.