Information Efficient White-Light Interferometry

White light interferometry (WLI) is a precise and versatile tool to measure smooth and rough surfaces. However, WLI requires a big amount of raw data (often hundreds of camera frames). Increasing demands on measurement speed and camera resolution urge us to reduce the necessary number of camera frames. We introduce three novel methods to achieve this goal: We first demonstrate that it is principally possible to reconstruct the correlogram envelope from only 10 exposures, nearly independent from the object depth. Another method to improve the information efficiency is to adapt the illuminating wave to the object shape. As an example, we demonstrate the measurement of cylinders and cones. We use a properly adapted conical mirror in the object arm of the interferometer. Light rays are directed perpendicular to the measured cylindrical or conical surface. The alignment of the object is uncritical and sub-lambda-accuracy can be achieved. The third method is to adapt the reference wave to the object shape. A simple solution is to put an (optically rough!) master object in the reference arm. This enables an extremely fast quantitative comparison of master and test object.