A method for detecting the surface structure and composition of a sample by means of a scanning unit, in particular for detecting traces, which are induced by contact of the skin of the human body on the surface of an object or absorbed by means of a trace carrier. The sample and the scanning unit are moved in relation to one another. The sample surface is irradiated line-by-line using a light beam or laser beam emitted from the scanning unit. The light beam or laser beam reflected from the sample surface is detected, and a digital image of the topography of the sample surface and the intensity of the reflected light beam or laser beam is generated from deviations of the reflected light beam or laser beam from the emitted light beam or laser beam to illustrate the composition of the sample surface.
