A method for detecting cracks in planar semiconductor substrates which have two opposite faces (30, 31) and a circumferential edge surface; wherein - electromagnetic radiation is introduced into the edge surface of the semiconductor substrate; wherein - the electromagnetic radiation has a wavelength that is at least partially transmitted through the material of the semiconductor substrate, so that - the electromagnetic radiation is directed from its point of incidence at the edge surface over at least half the distance to the opposite point of the edge surface by reflection at the faces (30, 31); and wherein - by means of an imaging optical detector in the form of a line sensor which is sensitive to the introduced electromagnetic radiation, radiation is detected which has been scattered at a crack and exits from one of the faces (30, 31) at the location of the crack; and wherein an image of the scattered intensity of at least a portion of the face that is viewed by the optical detector is generated from the signals captured by the optical detector; wherein the semiconductor substrate is irradiated with a laser beam which has a dimension on the edge surface in a direction perpendicular to the faces (30, 31) of the semiconductor substrate that is larger than the thickness d of the semiconductor substrate, in order to ensure injection of light into the semiconductor substrate even if the semiconductor substrate is displaced in a direction perpendicular to the faces; and wherein - during irradiation of the semiconductor substrate by the laser beam, the semiconductor substrate and the light source are translated relative to each other in a direction along the faces and transversely to the direction of incidence of the light, by advancement means, so that the point of incidence of the light beam moves along the edge of the semiconductor substrate; and wherein the apparatus comprises a computing device which generates an image of the face of the semiconductor substrate that is viewed by the optical detector on the basis of the detector signals captured along the area of the semiconductor substrate passed by the laser beam during the advancement of the semiconductor substrate; wherein the light source is arranged in fixed relationship to the optical detector, so that the area of the semiconductor substrate passed by the laser beam during the advancement remains stationary within the area covered by the optical detector; and wherein the advancement means moves the semiconductor substrate relative to the arrangement of light source and detector; and wherein the computing device successively records detector signals and to combine them into a surface image. - electromagnetic radiation is introduced into the edge surface of the semiconductor substrate; wherein - the electromagnetic radiation has a wavelength that is at least partially transmitted through the material of the semiconductor substrate, so that - the electromagnetic radiation is directed from its point of incidence at the edge surface over at least half the distance to the opposite point of the edge surface by reflection at the faces (30, 31); and - by means of an imaging optical detector in the form of a line sensor which is sensitive to the introduced electromagnetic radiation, radiation is detected which has been scattered at a crack and exits from one of the faces (30, 31) at the location of the crack; and wherein an image of the scattered intensity of at least a portion of the face that is viewed by the optical detector is generated from the signals captured by the optical detector; wherein the semiconductor substrate is irradiated with a laser beam which has a dimension on the edge surface in a direction perpendicular to the faces (30, 31) of the semiconductor substrate that is larger than the thickness d of the semiconductor substrate, in order to ensure injection of light into the semiconductor substrate even if the semiconductor substrate is displaced in a direction perpendicular to the faces; and wherein - during irradiation of the semiconductor substrate by the laser beam, the semiconductor substrate and the light source are translated relative to each other in a direction along the faces and transversely to the direction of incidence of the light, by advancement means, so that the point of incidence of the light beam moves along the edge of the semiconductor substrate; and