Headlamp (outdoor)

A headlamp, headlight, or head torch (UK) is a light source affixed to the head typically for outdoor activities at night or in dark conditions such as caving, orienteering, hiking, skiing, backpacking, camping, mountaineering or mountain biking. Headlamps may also be used in adventure races. Headlamps are often used by workers in underground mining, search and rescue, surgeons, and by other workers who need hands-free directed lighting. Headlamps are usually powered by three or four AA or AAA batteries, or rechargeable batteries. Systems with heavier batteries (4xAA or more) are usually designed so that the light emitter is positioned near the front of the head, with the battery compartment at the rear of the head. The headlamp is strapped to the head or helmet with an elasticized strap. Some headlamps have a separate battery pack connected by a cable, to be carried on a belt or in a pocket. Headlamps may be held in place by a single band around the head or (particularly heavier ones) have an additional band over the top of the head. Incandescent bulbs were used in headlamps until the introduction of white LEDs of sufficient brightness, with much lower power consumption and lifespan. Power LEDs rated at 1 watt or more displaced incandescent bulbs in many models of headlamps. To avoid damage to electronic parts, a heatsink is usually required for headlamps that use LEDs that dissipate more than 1W. To regulate power fed to the LEDs, DC-DC converters are often used, sometimes controlled by microprocessors. This allows the LED(s) to maintain constant brightness until battery voltage becomes too low to operate the lamp, and allows selectable brightness. Following the introduction of LEDs for headlamps, sometimes combinations of LED and halogen lamps were used, allowing the user to select between the types for various tasks. Carbide lamps were developed around 1900, and continued to be used after the introduction of battery lamps, which initially had poor battery life.