Patent ID: 8585254

Claim:
A lens for diffusing light emitted from a light source, the lens comprising: a concave light-incident surface including a plane portion opposed to the light source and an optical function portion that is formed on the plane portion and scatters and/or diffuses the light, and which the light emitted from the light source enters, wherein the lens is elongated in a first direction, wherein a cross-sectional shape of the concave light-incident surface in a plane perpendicular to the first direction is substantially constant along the first direction; a light guide portion through which the light that has entered the light-incident surface passes, the light guide portion comprising a first substance; a light-emitting surface to emit the light that has passed through the light guide portion; and a heat flow path extending from the light-incident surface to the light-emitting surface and discharges heat radiated from the light source, the heat flow path consisting of a second substance different from the first substance.