DEVICE FOR OPTICALLY MEASURING THE HEIGHT OF A SURFACE

The height of a surface (21) is determined by measuring the position of a radiation spot (11) located on the surface (21). The radiation spot (11) is formed by a narrow incident beam (10). Radiation reflected in the radiation spot (11) is projected on two position-sensitive radiation detection systems (41, 42). The detection systems (41, 42) are arranged at a different optical distance from the radiation spot (11). With the aid of a partially transparent mirror (3), or in a different manner, it is ensured that the intensity distribution on the detection systems (41, 42) is uniform. A line (G) through the radiation spot (11) is constructed by determining the same characteristic point (G.sub.I, G.sub.II), for example, the point of gravity in the intensity distributions at different optical distances from the radiation spot (11). The height of the spot (11) and hence of the surface (21) is determined by means of this line.