A new method to reduce the measuring uncertainty and the number of outliers in white-light interferometry

In white-light interferometry on rough surfaces (“Coherence Radar”) the physically-limited measuring uncertainty is determined by the arbitrary phase of the individual speckle interferograms. As a consequence, the standard deviation of the measured shape data is given by the roughness of the given surface. The statistical error in each measuring point depends on the brightness of the corresponding speckle; a dark speckle yields a more uncertain measurement than a bright one. If the brightness is below the noise threshold of the camera, the measurement fails completely and an outlier occurs. We present a new method to reduce the measuring uncertainty and the number of outliers. In our method, we generate two or more statistically independent speckle patterns and evaluate these speckle patterns by assigning brighter speckles more weight.