Solid state light sources—illumination or display

Devices for generating light by the passage of an electric current through a solid are now available in types having luminances ranging from 20-20 000 cd/m2. They are sufficiently adaptable and efficient to meet the requirements of many special applications, particularly those where space is limited. The paper discusses such applications, found mostly in the field of electronic display, in relation to device characteristics. Compared with conventional lamps, solid state sources are essentially low power devices. The development of sources which are sufficiently powerful for normal lighting purposes is not foreseen, but there is likely to be further evolution of special purpose devices and the paper concludes by indicating possible lines of development.