Patent ID: 8016450
Filing Date: 2011-09-13
Classification: G02B,G02F

Abstract:
1. An illuminating apparatus comprising: a plurality of point light sources in one plane, wherein the point light sources are light emitting diodes (LEDs); and two optical sheets overlapped in a region facing the plurality of point light sources, wherein the plurality of point light sources are arranged in a first direction and also arranged in a second direction orthogonal to the first direction, the optical sheet on a side of the point light sources has a plurality of first three-dimensional structures extending in a direction parallel to the first direction and arranged in a direction parallel to the second direction, the optical sheet on a side opposite to the point light sources has a plurality of second three-dimensional structures extending in a direction parallel to the second direction and arranged in a direction parallel to the first direction, and each of the second three-dimensional structures has a shape which generates a larger amount of return light from normal incident light as compared with the first three-dimensional structures, wherein the first and the second three-dimensional structures satisfy the following expressions of where P P H is the distance between the point light sources and the optical sheet on the side of the point light sources, Tt Tt