A planar light source apparatus includes a plurality of elongated lighting elements disposed in a common plane, and a plurality of mirror reflectors arranged perpendicular to the common plane and facing the lighting elements. The lighting elements are equidistantly spaced from each other. The lighting elements face a same direction. The mirror reflectors frame the lighting elements. The mirror reflectors each have a reflecting surface facing the lighting elements. The reflecting surfaces are perpendicular to the common plane. A distance between one of the reflectors and its nearest lighting element is maximum of half the distance between two adjacent lighting elements.