1. The process of exposing a photosensitive target surface to ultraviolet light, that comprises: collecting light emitted from an arc source and bringing it to a focus in the plane of the first lenticule matrix of a double lenticule matrix light integrator, forming by the lenticules of the second matrix multiple, magnified and superimposed images of the illuminated lenticules of the first matrix on said target surface, establishing a secondary light source by forming an aperture for the light going through said integrator at a plane in proximity to the latter, collimating the light from said source and which forms said images by passing said light through a collimating lens, regulating the angle of collimation of said light by selectively adjusting the area of said light source, and positioning a mask with a geometric pattern of diffraction slits immediately in front of said target surface.