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Three-dimensional representation of the topographical surface. (a,b) Images of the surface, viewed by reflection microscopy, at two focal planes, 8.5 µm apart. In (a), the focus is on the bottom of the rounded pit; in (b), the focus is on the surrounding ‘rim’. The areas focused on are marked with asterisks. (c) Reflection image of a surface, (d) represented in three dimensions. For easier reference, the same spot is marked with arrows in (c) and in (d).
