The Filmetrics F20 thin film system can be used for rapid determination of thickness and optical constants of thin films. Thickness and optical constants (n and k) of dielectric and semiconductor thin films can be measured in typically less than a second. Measured films must be optically smooth and within the thickness range of ~15 nm to 70 μm. Commonly measured films include semiconductor process films such as oxides, nitrides, resists, and polysilicon, optical coatings such as hardness and anti-reflection coatings, flat panel display films such as polyimides, resist, and cell gaps, and the various coatings used in CD and DVD manufacture.