Patent ID: 8743315

Claim:
A surface light source, comprising a light source section including a plurality of light emitting elements, each of the light emitting elements including a light emitting diode (LED) and a lens and having an optical axis extending from the LED through a center of the lens, wherein: the lens has a light incident surface on which light from the LED is incident, and a light exit surface that expands the incident light, the light incident surface has a continued depressed surface, and the light exit surface has a continued projected surface, a height of the lens has a maximum value at the center of the lens and decreases from the maximum value away from the center of the lens, an angle θ is defined as an angle formed by the optical axis and a line connecting the LED and a point of the light exit surface, and the light exit surface is configured such that in an area where θ is 2 degrees or more, a curvature of the light exit surface has a minimum at a first point having a corresponding angle θmin and a maximum at a second point, the first point exists at a first area of the light exit surface that satisfies 10 degrees <θ<30 degrees, and the curvature changes from decreasing to increasing within the first area.