Light unit with an extended light emission surface

A light unit with an extended light emission surface, comprising

• 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 flat light distribution body has a substantially cuboid shape and wherein the light source is arranged in a corner region of the flat light distribution body, with light from the light source being coupled into the flat light distribution body via a light entry surface,
• wherein the light entry surface has a concave shape, when seen from the light source, in a cross-sectional plane parallel to the first principal surface and wherein the light entry surface has a convex shape, when seen from the light source, in a cross-sectional plane orthogonal to the first principal surface,
• 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,
• wherein a total irregularity ratio of the first principal surface is defined as a combined area of the plurality of surface irregularities on the first principal surface divided by a total area of the first principal surface and wherein a regional irregularity ratio is defined as a combined area of a subset of the plurality of surface irregularities in a sub-region of the first principal surface divided by a total area of said sub-region of the first principal surface, wherein the first principal surface has at least one square sub-region whose area is 10% of the total area of the first principal surface and whose regional irregularity ratio is at least 50% higher than the total irregularity ratio, and
• wherein the first principal surface is the extended light emission surface and wherein the light unit comprises an extended reflector arranged outside of the flat light distribution body alongside the second principal surface, with the light being coupled out of the flat light distribution body at the first principal surface after being reflected at the plurality of surface irregularities on the first principal surface, travelling through the flat light distribution body, leaving the flat light distribution body at the second principal surface, being reflected at the extended reflector, entering the flat light distribution body via the second principal surface, and travelling through the flat light distribution body.