The light unit (SL) has an elongate reflector (LS) positioned on either side of the fluorescent light tube (L) and a raster lamella element (KL) with a double parabolic cross-section at either side of the light exit opening. Each raster lamella element has the foot side of its cross-section facing towards the light tube (L) and covered by a reflective cover, to reduce light losses. Pref. each raster lamella element is formed of sheet metal, the concave curvature of the reflective cover having a flat central section, enclosed on either side by a 4 sides pyramid formation (H).
