An illumination mean for the inspection of flat substrates is disclosed. The flat substrate includes an upper edge area, a lower edge area and a front area. The illumination means is formed as an annular segment and comprises an opening into which at least the edge area of the flat substrate extends. A plurality of light sources are arranged on an annular segment in a housing. Inside the housing, a reflective element is provided so that the light from the light sources does not impinge perpendicularly on the upper edge area, the lower edge area and the front area of the flat substrate.