SureFire pioneered the design and manufacture of the compact, high-intensity illumination tool. In the beginning, SureFire used custom-engineered incandescent lamps as light emitters. These state-of-the-art devices featured custom filaments, high-pressure xenon fill gas, and halogen additives to maximize operating life, light output, and power efficiency. We still make several models to support older products.
But at this point in the technological evolution of illumination tools there is no reason to use incandescent emitters, and many powerful reasons not to use one. The fact is, all tungsten filaments eventually break, either from excessive recoil or impact shock or from unavoidable and normal filament erosion. The state-of-the-art light emitter for portable illumination tools is the light emitting diode, or LED, the subject of our next section.
Light Emitting Diodes (LEDs)
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 LEDs 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.
LEDs 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 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 tremendous advantages over incandescent lamps. First, LEDs can last thousands of hours versus less than fifty hours for high-output incandescent lamps. Second, because LEDs 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 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 variable-output light sources.
Most LEDs emit from a flat surface, necessitating complex reflectors and lenses to produce desirable beam characteristics. Because LEDs 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. 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.
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 LEDs 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 (NVDs). 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.
SureFire’s HellFighter® WeaponLights use High Intensity Discharge (HID) lamps. HID lamps do not use a tungsten filament, but instead use a clear quartz capsule (an "arc tube") fitted with electrodes at either end and containing high-pressure xenon gas and additional chemical components. When sufficient voltage is applied to the electrodes the gas inside the tube is heated and ionized, enabling it to conduct electricity in the form of an "arc" (basically a sustained electrical spark), and causing it to emit light. When functioning, pressure inside the arc tube rises to above atmospheric pressure.
HID lamps are extremely bright and extremely efficient and, with equal power input, they produce more than twice the lumens of an incandescent lamp with a longer operating life than comparable incandescent lamps. Since they have no filament to break or burn out, they are extremely resistant to shock and vibration. However, they are comparatively large, require a substantial power source, and their lumen output level is effectively non-adjustable.