Method of determining a surface illuminated by incident light. First the
intensity (I.sub.1 (x,y)) of light reflected from the surface is recorded
in a first image of the surface. After this, the intensity (I.sub.2 (x,y))
of light reflected from the surface is recorded in a second image of the
surface, taken at a different angle of illumination. Only the diffusely
reflected light is recorded. The difference between the recorded
intensities of the first and the second images is determined to obtain a
representation that emphasizes variations in gradient of the surface. This
representation is further processed by signal-adapted integration to a
topographic description, that is, a height function of the surface.
