Xenon/Halogen Incandescent Lamps
Identical non-SureFire miniature lamps. Left lamp is unused, right lamp shows tungsten deposits after several hours of use. Incandescent lamps produce light by using electricity to heat a small coiled tungsten metal wire, which is enclosed within a glass "bulb" filled with special gases, to a high temperature — around 2,500 to 3,000 degrees Celsius — at which point the wire glows white-hot. The miniature incandescent lamps that SureFire uses in its WeaponLights and flashlights are not typical off-the-shelf products. They are state-of-the-art devices with the following features:
Custom Filaments — The incandescent lamps ("light bulbs") used in our WeaponLights and flashlights are designed around a specific power supply, light output, and runtime. Filament performance varies according to wire diameter, filament length, filament coil diameter, total coils, and coil-to-coil proximity. Finally, the finished filament must withstand the vibration and G-forces produced by firearms.
SureFire MN21 lamp, showing heavy duty high-output filament. Xenon Gas — The high temperature of the lamp filament causes tungsten atoms to "boil off" and migrate to the cooler glass wall of a lamp, where they condense to form a dark light-blocking layer. Adding a high-pressure inert gas inhibits tungsten boil-off, which reduces the rate of tungsten atom deposition and lengthens the operating life of the lamp. The gas also permits increased filament operating temperature, which in turn increases light output for a given power consumption rate. Argon and krypton are often used as the inert fill gases, but they don't work as well as xenon. Although xenon is much more expensive, SureFire uses it exclusively to provide optimum lamp performance.
Halogens — To maximize their operating life and light output, some SureFire lamps contain a proprietary mix of halogens, a family of elements that includes fluorine, chlorine, bromine, and iodine. Inside a functioning incandescent lamp, tungsten atoms boil off the filament, migrate toward the cooler areas near the lamp wall, and combine with halogen atoms to form a tungsten halide vapor. This vapor migrates back to the lamp filament, where high temperature breaks it down again into tungsten and halogen atoms. The tungsten atoms are re-deposited on the filament and the oxygen and halogen migrate back toward the bulb wall to re-combine with new boiled-off tungsten atoms. This continuous process, called the halogen cycle, keeps the lamp's glass walls comparatively clean of light-blocking tungsten deposits.
Incandescent lamps produce a broad spectrum of light (including infrared) and can be made to have a high maximum lumen output, but they are comparatively inefficient users of power, and their lumen output level is effectively non-adjustable.
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.
HID Lamps
High Intensity Discharge (HID) lamps do not use a tungsten filament, as do incandescent lamps. Instead they use a clear quartz capsule (an "arc tube") having electrodes at either end 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 several times atmospheric pressure.
HID lamps are both extremely bright and extremely efficient — for an equal power input they produce more than twice the lumens of a tungsten incandescent lamp — and their operating life is also several times that of comparable incandescent lamps. An additional benefit: since they have no filament to break or burn out they are extremely resistant to mechanical shock and vibration. However, they are comparatively large, requires a substantial power source to operate, and their lumen output level is effectively non-adjustable.
