Flashlights that use light-emitting diodes (LEDs) instead of conventional lightbulbs have become available. LEDs have existed for decades, mainly as low-power indicator lights. LED flashlights with power and running time better than some incandescent lights. LEDs can be significantly more efficient at lower power levels and so use less battery energy than ordinary lightbulbs. Resulting in a longer battery life, in some cases hundreds of hours, although the LED efficiency advantage diminishes at higher power levels. LEDs also survive sharp blows that often break conventional lightbulbs.LED flashlights are often electronically regulated to maintain constant light output as the batteries fade. By contrast a non-regulated flashlight becomes progressively dimmer, sometimes spending much of the total running time below 50 percent brightness level.The first Luxeon LED flashlight was the Arc LS in 2001.
Today various led flashlights are produced, such as aluminium led flashlights, which have aluminum bodies; Plastic led flashlights, which use plastic bodies; Led pen light, which shape of appearance is a pen; Led keychain light, which has a keychain together with flashlight; Compacted Led Light, which shape of appearance is round and so on. For example, compacted led light is a kind of cabinet led flashlight. It can be folded flat for easy storage and super brought compact light. Because very few high-output LED flashlights, compacted Led Light can use a plastic body. Sometimes it also uses aluminum bodies or glass bodies. Compacted led lights can be fixed a place, so easy focus lighthead. Their lights can be designed different colors and has a lower price, so they are used to decorate usually.
References
http://en.wikipedia.org/wiki/Flashlight#LED
http://www.led-flashlite.com/product/compacted-led-light/index.htm