Abstract: A device for generating, detecting, and characterizing a raster image of the contour of an object, wherein a narrow concentrated light beam (1) is emitted towards a light beam deflector means (3) causing said light beam (1) to sweep repeatedly across a plane (19) through which the object is guilded, and where the light beams not screened by said object are received, and are opto-electrically transformed into electrical signals, e.g. pulse trains which are characteristic of the incremental portions of a raster image of said object, said signals being processed to yield a characteristic expression of the contour of said object. A retro-reflector (5;32) is placed in such a manner that light beams (10) not screened by said object are reflected back across said plane (19) at a second angle of scattering which is equal to or larger than said first angle of scattering, and a detector (11) receives the reflected light beams (10) and transforms them into said signals, preferably for forming a successive pulse train.