ABSTRACT
All articial light sources on the market are based on three technologies, two of which (incandescence-and plasma-based sources, otherwise known as discharges) have reached a plateau with regard to efcacy but nevertheless there is still ongoing research and fascinating developments. The third technology, although its development and marketing started much later than these other two (and perhaps for that very reason), is now showing such fast progress that not only can it compete with the other technologies, but in some cases it is the preference.
