In this work, a fast imaging method based on sub-dark-field illumination in white-light interferometry is presented. Applying this method, we successfully resolved the surface profile of test structures even for a smooth surface with a roughness of the order of a few angstroms. The true-colour sequence band is presented, which provides the relationship between the surface colours and the optical path difference. Several characteristics (e.g., basic colour, image contrast, thickness variations, and so on) for the white-light interference images are discussed in detail. Pair images with sub-dark-field illumination in the principal interference fringe were also observed and analysed.
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