US Patent 8469552 Street lighting device

A lighting device for streets, paths, and the like, includes a lighting unit containing a lighting element and a lens arranged in front of the lighting element in the main emission direction to produce a specified light distribution characteristic. The lens includes a light entrance surface on a light entrance side facing the lighting element and a light exit surface on a light exit side facing away from the lighting element, at which surfaces the light is refracted. The light entrance surface and/or the light exit surface of the lens is shaped in a direction transverse to the optical axis of the lighting element in such a way that the luminous intensity of the coupled out light, starting from a center plane that intersects with the optical axis, rises with an increasing emission angle from the optical axis at least partially according to a tangent function.