With the exception of our HellFighter® WeaponLights, all current SureFire illumination tools use an LED (Light Emitting Diode) light source. An LED is a semiconductor chip that converts electrical energy directly into light. An LED is classified as a solid-state light source because it has no gas or liquid components, as do other light sources. The LED's in SureFire flashlights consists of an emitter chip mounted on a solid base; the chip is attached to electrical leads that conduct power to it, and it’s encased in a clear polymer that is shaped to focus or disperse the LED's light in the desired manner.
LED's generally emit light within a narrow spectral band. In order to produce white light, which consists of nearly the entire visible spectrum combined, we use LED's 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.
LED's possess tremendous advantages over incandescent lamps. First, LED's can last thousands of hours versus less than fifty hours for high-output incandescent lamps. Second, because LED's are very robust in construction, and have no delicate parts such as glass bulbs or filaments, they are extremely resistant to vibration and shock, making them well suited for the combat environment or for mounting on firearms. Third, white-light LED's produce virtually no invisible infrared radiation, as opposed to incandescent lamps, which emit over 85% of their output as infrared, and therefore LED's 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 LED's the natural choice for variable-output light sources.
Most LED's emit from a flat surface, necessitating complex reflectors and lenses to produce desirable beam characteristics. Because LED's are susceptible to potential damage from overheating, they have certain thermal design requirements that dictate the maximum output possible from a given LED, and affect the overall configuration of the specific illumination tool. LED's 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 LED's only from the highest-quality bins.
Most SureFire's LED illumination tools contain a durable, sealed electronic power regulator that supervises the operation of the LED. 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 usable life of the batteries. Although an 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 reduces the period of negligible output and increases the duration of useful light output.
Previously the only downside to white-light LED's was that they produced only negligible amounts of infrared radiation; therefore they could not be fitted with an infrared filter and then used with night vision devices (NVD's). However, in 2009 SureFire introduced its V-Series WeaponLights, which use a multi-spectrum LED that encapsulates both white light and infrared radiation in a single compact package capable of changing spectrum with the twist of a bezel, with no need for an IR filter.