Patent ID: 7422347

Claim:
A planar light source comprising at least one point light source disposed on a supporting substrate, and a cylindrical lens covering the point light source, wherein the cylindrical lens has a concave lens portion having a first inner surface and a first outer surface with a distance between the first inner surface and the first outer surface at a center region of the concave lens portion being smaller than a distance between the first inner surface and the first outer surface at a peripheral region of the concave lens portion in a cross sectional plane (x-y plane) taken along the direction (x direction) parallel to the supporting substrate and the direction (y direction) perpendicular to the supporting substrate to achieve a concave lens function with respect to a first group of light rays emitted from the point light source generally in the direction (y direction) perpendicular to the supporting substrate when the first group of light rays passes through the first inner surface and the first outer surface, and a convex lens portion having a second inner surface and a second outer surface with a distance between the second inner surface and the second outer surface at a center region of the convex lens portion being larger than a distance between the second inner surface and the second outer surface at a peripheral region of the convex lens portion in the cross sectional plane (x-y plane) to achieve a convex lens function with respect to a second group of light rays emitted from the point light source generally in the direction (x direction) parallel to the supporting substrate when the second group of light rays passes through the second inner surface and the second outer surface, and the point light source is disposed between the convex lens portion of the cylindrical lens and the focal point of the convex lens portion of the cylindrical lens.