Patent ID: 7980746

Claim:
A hollow type planar illuminating device, comprising: a reflecting surface member disposed on a bottom surface of a hollow unit case and having a reflecting surface inclined with respect to the bottom surface; a light emitting surface member disposed at a position within the unit case facing the reflecting surface member in parallel to the bottom surface of the unit case; an LED light source unit including a plurality of LEDs arranged to be adjacent to each other on at least one side of a hollow light guide space extending between the light emitting surface member and the reflecting surface member and emitting light to the hollow light guide space; and a light collecting lens disposed along the LED light source unit to reduce a directivity angle of the light emitted from the LED light source unit, wherein the reflecting surface of the reflecting surface member is arranged to increase the height thereof according to a distance from the LED light source unit, and has a roughness Ra of 1 μm<Ra<10 μm.