Ellipsometry measures a change in polarization as light reflects or transmits from a material structure.  The measured response is dependent on optical properties and thickness of each material.  Hence, ellipsometry determines film thickness and optical constants. It can additionally be applied to characterise composition, crystallinity, roughness, doping concentration, and other material properties associated with a change in optical response.

Film thickness
Optical constants (n,k)
Thin film porosity

Metal films
Organic Films
Photoresist
Anti-reflective coatings
Thin dielectric layers
Flat panel display thin films