Light can be produced and/or controlled electronically in a number of ways. In light emitting diodes (LEDs), light is produced by a solid state process called electroluminescence. Under specific conditions, solid state light sources can produce coherent light, as in laser diodes. Other devices such as liquid crystal devices (LCDs) control externally supplied light to form display units. Liquid crystal projectors have made a major impact on public presentation of information, making inroads on the venerable cathode ray tubes. Other technologies such as the Texas Instruments' micromirror devices, called "digital light processors" as well as varieties of plasma displays are beginning to enter the market for displays.

Craford, et al. make the case that LED lighting is making great strides in power and efficiency and will play a more major role in general lighting. Some types last 100,000 hours, compared to about 1000 hours for an incandescent bulb. Now that blue LEDs have become a reality, white light LEDs can be produced by combining the red, green and blue chips in a single device.

One way to constuct an LED is to deposit three semiconductor layers on a substrate. Between p-type and n-type semiconductor layers, an active region emits light when an electron and hole recombine. Considering the p-n combination to be a diode,then when the diode is forward biased, holes from the p-type material and electrons from the n-type material are both driven into the active region. The light is produced by a solid state process called electroluminescence.

In this particular design, the layers of the LED emit light all the way around the layered structure, and the LED structure is placed in a tiny reflective cup so that the light from the active layer will be reflected toward the desired exit direction.

An LED is a directional light source, with the maximum emitted power in the direction perpendicular to the emitting surface. The typical radiation pattern shows that most of the energy is emitted within 20° of the direction of maximum light. Some packages for LEDs include plastic lenses to spread the light for a greater angle of visibility.