Light-Emitting Diodes (LEDs)
LED diagram compliments of Lumileds Lighting LLC. An LED (the acronym for Light-Emitting Diode) is a semiconductor chip that converts electrical energy directly into light. An LED is called a solid-state light source because it has no gas or liquid components, as do other light sources. The LEDs in SureFire flashlights consists of the emitter chip mounted on a solid base; the chip is attached to electrical leads (wires) that conduct power to it, and it is encased in a clear polymer that is shaped to either focus or disperse the LED's light in the desired manner.
LEDs generally emit light within a narrow spectral band. In order to produce white light, which consists of the entire visible spectrum combined (or nearly so, as far as the human eye can discern), we use LEDs that emit near-ultraviolet blue light that strikes an upper layer of phosphors. These phosphors absorb the blue light and re-emit white light, in much the same manner that fluorescent light tubes produce white light.
LEDs possess some tremendous advantages over incandescent lamps. First, LEDs can last thousands of hours versus less than fifty hours for high-output incandescent lamps. Second, Photo showing flat surface of high-output LED and surrounding micro-textured reflector because LEDs are very robust in construction, and have no mechanically delicate parts such as glass bulbs, filaments, or filament supports, they are extremely resistant to vibration and shock, making them well-suited for the combat environment or for mounting on firearms. Third, LEDs produce virtually no invisible infrared radiation, as opposed to incandescent lamps, which emit over 85% of their output as infrared, and therefore LEDs are much more efficient in producing light than incandescent lamps — an important factor for battery-operated flashlights. And fourth, they will emit light over a wide range of power input making LEDs the natural choice for adjustable-output light sources.
As noted above, there are currently some disadvantages to LED light sources. First, most LEDs emit forward from a flat surface, necessitating more complex reflectors and lenses to produce desirable beam characteristics. Second, because LEDs are susceptible to damage from overheating they have certain thermal design requirements. Therefore, continuous-use LED sources currently have a practical limit of less than 150 lumens. Third, LEDs are difficult to manufacture without some variance in lumen output and color. For this reason, they are tested and sorted by the manufacturer into different bins according to output and color. SureFire minimizes such product variability by purchasing LEDs only from the highest-quality bins.
Electronic Power Regulation — SureFire's LED illumination tools contain a rugged, sealed electronic power regulator that supervises the operation of the LED (with the exception of the A2 Aviator, in which the xenon lamp is regulated). This circuitry assesses battery output, monitors system performance, and controls power supplied to the LED. Power regulation provides a more consistent light output for the useable life of the batteries. Although any LED may continue to produce negligible light output for up to several hundred hours, the amount of useful light produced is of a shorter duration. Power regulation circuitry reduces the amount of negligible output and increases the overall duration of useful light output.
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