Cold light source:

    Cold light source is the use of chemical energy, electrical energy, bio-energy excitation light (fireflies, neon, LED, etc.). Has a very excellent optical, variable flash features. Luminous object, its temperature is not higher than the ambient temperature is high, this luminescence is called as cold light source, such as LED is the use of electron-hole pair recombination.

   Strictly speaking, LED light-emitting electroluminescent aurora is also heat generation, only relatively incandescent light source is a low point. LED optical conversion efficiency of 30%, and wherein the internal quantum efficiency of about 70% (close to the theoretical limit), the external quantum efficiency of about 50% (this is the experimental data, is not the exact value).

Heat source:

    Use of heat excitation light sources such as incandescent lamps at 3,000-4,000 K temperature thermal radiation emission. Incandescent lamps 80 to 90% of the energy is converted to heat, about 10% of the energy is converted to light energy. Therefore, the luminous efficiency is low. We are not under the lamp housing is defined as the temperature of cold light, or heat sources. Lighting around the high and low temperature, can only judge the merits of the lamp cooling measures.

Difference:

    Cold light and heat source, we can not come only from the definition of distinction. In fact we are talking about does not mean cold light source emitting the process does not generate heat, but not by way of the luminous energy is converted to light energy. Is typical of the incandescent electric energy into heat energy, and then the process of thermal energy into light energy. Heat loss is higher, low luminous efficiency, according to the current development trend of white LED cold light alternative heat source era whom far away. So we can put LED as a cold source.