Light unit with an extended light emission surface

A light unit includes a light source, and a flat light distribution body having a first principal surface and a second principal surface disposed on opposite sides of the flat light distribution body, wherein the light source is positioned outside of the flat light distribution body, with light emitted by the light source being coupled into the flat light distribution body and being propagated within the flat light distribution body via total internal reflection at the first and second principal surfaces, wherein the first principal surface has a plurality of surface irregularities, wherein light arriving at a surface irregularity at an angle of incidence is reflected at an angle of reflection that is different from the angle of incidence with respect to the first principal surface, with the angle of reflection allowing for the light to be coupled out of the flat light distribution body, and wherein a total irregularity ratio of the first principal surface is defined as a combined area of the plurality of sur