Fehérfényinterferometria

Fehérfényinterferometria, or white light interferometry, is an optical technique used to measure surface topography and to determine the refractive index of transparent materials. It relies on the phenomenon of interference, where waves of light combine and either reinforce or cancel each other out. In white light interferometry, a broadband light source, which contains a wide spectrum of wavelengths, is split into two beams. One beam, the reference beam, is reflected off a known surface or a mirror. The other beam, the object beam, is reflected off or transmitted through the surface or material being investigated.

These two beams are then recombined. When the optical path difference between the two beams is very small, interference fringes can be observed. Unlike monochromatic light interferometry, where interference patterns are stable and distinct over large path differences, white light interferometry produces interference only when the path difference is close to zero. This is because white light comprises many different wavelengths, and constructive or destructive interference for all wavelengths simultaneously only occurs at a zero path difference, creating a unique, bright fringe at this specific point.

By scanning the position of one of the mirrors or the sample and recording the interference intensity, a profile of the surface height can be constructed. The position of the central bright fringe corresponds to the zero path difference, and deviations from this position indicate variations in the surface height. This method offers high vertical resolution, often in the nanometer range, making it suitable for precision metrology in fields like semiconductor manufacturing, optical component testing, and microelectromechanical systems (MEMS) characterization. It can also be used to measure the thickness and refractive index of thin films and transparent materials.