Thermal light emitting device

A thermal emitter device, comprising:

• a thermal emitting membrane comprising a surface, wherein the thermal emitting membrane is arranged to be heated to a thermal emission temperature so that the surface radiates IR or visible light,
• wherein the emissivity of the surface is lower than 0.7,
• a lens, comprising a lens surface, the lens surface facing the surface of the thermal emitting membrane, and having a reflectivity normal to the lens surface comprised in the range 4% to 40%, so as to partially reflect the radiated IR or visible light,
• wherein the distance between the lens surface and the surface is equal or lower than L/4, where L is a major length of the thermal emitting membrane,
• so that a part of the IR or visible light reflected by the lens is reabsorbed by the thermal emitting membrane, and another part of the IR or visible light reflected by the lens is reflected by the thermal emitting membrane toward the lens, having therefore another chance to go through the lens, thereby increasing the efficiency of the thermal emitter device.