Cold light source: cold light source is the use of chemical energy, energy, bio-energized light source (firefly, neon, LED, etc.). Has a very good optical, flashing characteristics. When the object emits light, its temperature is not higher than the ambient temperature, this light is called cold light source, such as LED is the use of electronic holes on the composite luminescence. In the strict sense, the LED light-emitting diodes is the electroluminescence also has heat, but relatively low point for incandescent light source. LED electro-optical conversion efficiency of about 30%, of which the internal quantum efficiency of about 70% (close to the theoretical limit), the external quantum efficiency of about 50%. (This is just experimental data, not the exact value)
Hot light source: The use of thermal energy to stimulate the light source, such as incandescent lamp at 3,000-4,000K temperature when the heat radiation. Incandescent 80-90% of the energy conversion can heat, about 10% of the energy into light energy. So the luminous efficiency is low. We are not based on the temperature of the lamp shell is defined as cold light source, or hot light source. Lamps around the temperature level, can only judge the advantages and disadvantages of the lamp cooling measures.
The distinction between cold light and hot light sources, we can not only distinguish from the definition. In fact, we say that the cold light source does not mean that the process of light does not produce heat, but refers to the way the light is not converted from thermal energy to light energy. Incandescent lamp is a typical process from converting electrical energy into heat energy and converting heat energy into light energy. Heat loss is high, low luminous efficiency, according to the current development trend of LED white light cold light source to replace the era of hot light is not far away. So we can see the LED as a cold light source
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