SURFACE ILLUMINATION SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide an illumination system which has high efficiency and high luminance, less consumes electric power and features high mass productivity. SOLUTION: Plural pieces of grooves 6 having a triangular shape in section are formed on the rear surface of a parallel flat planar light transmission body 1. A wire-shaped light source 4 is arranged in parallel with these grooves 6 on the one flank of the light transmission body 1 and a reflector 5 is so disposed as to cover the wire-shaped light source 4. The angle ϕ1 of the slope on the wire-shaped light source 4 side of the grooves 6 is set like the equation, where the refractive index of the light transmission body 1 is defined as (n) and the central angle of a radiation luminance distribution as α. ϕ1 =53 deg.-sin<-1> (1/n)sin α}A light diffusion plate 2 is arranged atop the light transmission body 1 and a reflection plate 3 is arranged to cover the rear surface and the other flank of the light transmission body 1.