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
... [Show full abstract] 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.