It is a high-precision optical measurement technique based on wave interference. It is used to detect and analyze microscopic displacements, surface variations, or changes in optical path length.
The method works by splitting a light beam into two paths: a measurement beam that interacts with the sample and a reference beam.
When recombined, the beams create an interference pattern of light and dark fringes, whose position and contrast reveal information about the sample’s topography, flatness, roughness, or thickness.
HOW DOES INTERFEROMETRY WORK?
The operating principle of interferometry follows these steps:
Beam splitting: A light source (monochromatic for phase-shifting interferometry or broadband for coherence-scanning interferometry) is split into measurement and reference beams by a beam splitter.
Optical paths: The two beams travel along different paths; one is reflected by the sample surface, while the other follows a reference path.
Recombination: When the beams are brought back together, they overlap and interfere, producing an interference pattern.
Fringe analysis: Variations in the position, contrast, and shape of the fringes correspond to changes in the optical path length.
Data extraction: Advanced algorithms translate these phase shifts into precise surface or displacement measurements, often with sub-nanometric resolution.
APPLICATIONS
Interferometry is applied across multiple domains requiring extremely high precision:
Semiconductor industry: Inspection of wafers, multilayer coatings, and MEMS structures.
Materials science: Characterization of surface roughness, thin-film thickness, and layered materials, including transparent and semi-transparent samples.
Engineering and manufacturing: Quality control of optical components, lenses, and precision surfaces.
Optics and photonics: Measurement of lenses, including form and surface irregularities.
Surface engineering and tribology: Analysis of wear, friction-related textures, and surface functionalization.
