Patent ID: 8246188

Claim:
An illuminating device comprising: a plurality of linear light sources arranged so that respective central axes are in parallel with each other and are included in one plane; a reflecting plate arranged oppositely to the respective linear light sources; a diffusion member arranged on a side opposite to the reflecting plate with respect to one face; and an optical member arranged between the respective linear light sources and the diffusion member, wherein the optical member has a light incident surface in parallel with the one face, and a light emission surface that has a first three dimensional structure in a first region opposed to the respective linear light sources in a normal line direction of the one face and a second three dimensional structure in a second region opposed to an intermediate region between one linear light source and another linear light source adjacent to the one linear light source in the normal line direction of the one face, and wherein where an occupancy ratio of a first section in which light from the respective linear light sources vertically entering the light incident surface is entirely reflected by the first three dimensional structure and return light oriented toward the reflecting plate is generated out of the first region when the optical member is viewed from the normal line direction of the one face is K 1 ; and where an occupancy ratio of a second section in which light from the respective linear light sources vertically entering the light incident surface is entirely reflected by the second three dimensional structure and return light oriented toward the reflecting plate is generated out of the second region when the optical member is viewed from the normal line direction of the one face is K 2 , K 1 and K 2 satisfy the following formula, K 1− K 2>0.