Filmetrics Optical Profilometer measures thin film properties using the Spectral Reflectance technique. Spectral reflectance measures the amount of light reflected from a thin film over a range of wavelengths, with the incident light perpendicular to the sample surface. It can measure the thickness, roughness, and optical constants of a film by measuring how the films interact with light. Optical constants describe how light propagates through and reflects from a material. Once the optical constants are measured they may be related to other material parameters, such as composition and band gap. This method is nondestructive, and require little or no sample preparation but has a limitation of measuring only less complex structures. For more detailed measurements Ellipsometry is the most suitable method.