Patent ID: 9200777
Filing Date: 2015-12-01
Classification: F21V,F21Y,G02B,G02F,H01L

Abstract:
1. An illumination device comprising a planar light source and an optical element including a light receiving surface for receiving light from the planar light source and a light exiting surface, wherein a shape of the planar light source in a plane is symmetric with respect to x-axis and y-axis and length of the shape in x-axis direction is shorter than length of the shape in y-axis direction where the center of the planar light source is set as the origin and two axes orthogonal to each other are selected as x-axis and y-axis, and wherein the maximum value of x-coordinate of the planar light source is a, the maximum value of y-coordinate of the planar light source is b, the following relationship holds: wherein the axis which passes through the origin and is perpendicular to the plane is selected as an optical axis, the x-axis and the y-axis being orthogonal to the optical axis, and the light receiving surface has a concaved shape, the top of the concaved shape being at the point of intersection between the light receiving surface and the optical axis and any cross section of the top of the concaved shape containing the optical axis being symmetric with respect to the optical axis, and wherein, in a cross section which contains the optical axis and the x-axis a distance between the light receiving surface and the plane at a point having x-coordinate of a or −a is h