What is the difference between cold light source and thermal light source?

 

The cold light source we often say does not actually refer to those light sources that do not generate heat during the light-emitting process, but refers to the light-emitting method that is not like the traditional light source that converts heat energy into light energy. In fact, it refers to a cold light source that uses chemical energy and electrical energy to excite the light source, and has the characteristics of variable flicker. The thermal light source we are talking about is a light source excited by thermal energy. During the light-emitting process, most of its energy needs to be converted into thermal energy, and then converted from thermal energy into light energy. Therefore, the thermal energy loss is relatively high, and the luminous efficiency is not cold light source. high. However, there are also advantages. Hot light sources can be directly connected to the circuit, and the maximum brightness can be achieved at the moment of power-on, but cold light sources cannot.

The cold light source is a light source excited by chemical energy, electrical energy, and biological energy (fireflies, neon lights, LEDs, etc.). It has very good optical and variable flicker characteristics. When an object emits light, its temperature is not higher than the ambient temperature. This type of light emission is called a cold light source. For example, LED lights used in mingtai LED operating light, which use electron-hole pairs to recombine light. Strictly speaking, LED light-emitting diodes are electroluminescence and also generate heat, but they are lower than light sources such as incandescent lamps. The LED electro-optical conversion efficiency is about 30%, of which the internal quantum efficiency is about 70% (close to the theoretical limit), and the external quantum efficiency is about 50%.

Thermal light source: a light source excited by thermal energy, such as an incandescent lamp that emits light from thermal radiation at a temperature of 3,000 to 4,000 K. Incandescent lamps have 80-90% of energy converted into heat energy, and about 10% of energy converted into light energy. Therefore, the luminous efficiency is low. We do not define it as a cold light source or a hot light source based on the temperature of the lamp housing. The temperature around the lamp can only judge the heat dissipation measures of the lamp.