Abstract: For testing substantially two-dimensional relief-structured patterns, in particular circuit boards, an optical scanning head is used which directs a light band according to the light sectioning principle at an angle .alpha. to the printed circuit board (10) and in which a linear scanning diode array (17a) is positioned in such a manner that it receives only such light as is reflected by the circuit boards whose surfaces have the nominal height h from the base plate (10). For continuously controlling the operating distance (1) between the linear diode array (17a) and the base plate (10), a pair of linear diode arrays (17b) is arranged parallel to the diode array between which the light reflected at the base plate (10) is incident if the nominal operating distance (1) has been kept and on which this light impinges if deviations of the operating distance have occurred.