Light source types

The transformation of electrical energy into visible radiation (light generation) takes place in light sources. Basically, there are three different types of such energy transformation, namely light generation

  • by temperature increase (thermal radiator),

  • by gas discharge (discharge lamps) and

  • by electronic procedures in solid state bodies, electroluminescence (LED).

Traditional light sources such as thermal radiators and discharge lamps were always provided in the form of lamps with sockets for replaceable operation. For the most part, this no longer applies to LED light sources. Especially nowadays, luminaires with permanently integrated LED light sources are used for many applications.

In industrial nations, the quantity percentage of incandescent and halogen lamps was about 3/4 of all utilised lamps in the past, especially due to their wide distribution in residential lighting. Gas discharge lamps with a quantity percentage of about 1/4 were used predominantly for technical indoor and outdoor lighting in order to cover the great light requirements in this sector. Their main advantage is their luminous efficacy, which is 6 to 8 times that of general-use incandescent lamps.

Figure 2.98: Overview of the most common light sources

Currently, both types are increasingly replaced by LED light sources. Regarding residential lighting, this happens mainly due to the incremental prohibition of incandescent lamps. Regarding technical lighting, the reason is also the increased energy efficiency, high light quality and long service life of LED products compared to discharge lamps. Altogether, LED lamps represent the most economic lighting solution for almost any application. 

In the following, different types of light sources and their typical applications will be explained. In addition to these light source types, there are specific light sources for medical, therapeutic and other purposes as well as for projector technology and photographic technology.