Accessories

Accessories

Translucent, colored plastic cones slipped over the lens of a flashlight increase the visibility when looking at the side of the light. Such marshalling wands are frequently used for directing automobiles or aircraft at night.

Colored lenses placed over the end of the flashlight are used for signalling, for example, in railway yards. Colored light is occasionally useful for hunters tracking wounded game after dusk, or for forensic examination of an area.

Other designs

A penlight

A penlight is a small, pen-sized flashlight, usually containing two AA batteries or AAA batteries. In some an incandescent light bulb has an integral lensthat focuses the light, thus no reflector is built into the penlight. Others use incandescent bulbs mounted in reflectors, while LED lamps are becoming increasingly common. Low-cost units may be disposable with no provision for the user to replace batteries or bulbs, and are sometimes imprinted with advertising for promotional purposes.

An LED headlamp

A headlamp is a flashlight designed to be worn on the head. A headlamp usually consists of the light emitter at the front, with a battery pack also attached to the front or back. The battery pack may be attached to the back of the head or in a pocket to improve balance. Headlamps leave the user's hands free, making them popular for recreational and occupational activities.

Sometimes a tactical light is mounted to a handgun or rifle.Such lamps are designed to withstand the impact of recoil, and to be easily controlled while holding the weapon.

Most flashlights are cylindrical in design, with the lamp assembly attached to one end. However, early designs came in a variety of shapes. Many resembled modern day lanterns, consisting largely of a box with a handle and the lamp attached to the front. Some others were made to have a similar appearance to candles. Hand-held lanterns using larger batteries give greater running time, and, with large reflectors, can produce more concentrated beams better adapted to long-distance use.

Although most flashlights are designed for user replacement of the batteries and the bulb as needed, fully sealed disposable flashlights, such as inexpensive keyring lights, are made. When the batteries are depleted or the bulb fails, the entire product usually is thrown away or recycled and a new one purchased to replace it.

A diver's lamp.

Diving lamps must be watertight under pressure and are used for night diving and supplemental illumination where surface light cannot reach.

People working in areas with significant concentrations of flammable gases or dusts, such as mines, engine rooms of ships, chemical plants or grain elevators, use so-called "non-incendive", or "explosion proof" flashlights. These are constructed so that any gas or dust that leaks into the flashlight is not likely to set off an explosion outside the light. The flashlight may require approval by an authority for the particular service and particular gases expected. The external temperature rise of the flashlight must not exceed the autoignition point of the gas, so substitution of more powerful lamps or batteries may void the approval.

Non-incendive flashlight for use when inspecting areas full of flammable gas.

Portable hand-held electric lanterns can provide larger reflectors, lamps, and batteries than tubular flashlightsmeant to fit in a pocket. They are often designed for lighting the broad area immediately around the lantern, as opposed to forming a narrow beam; they can be set down on a level surface or attached to supports. Some electric lanterns use miniature fluorescent lamps for higher efficacy than incandesent bulbs.

Power sources

The most common power source for flashlights is the battery. Many types of batteries are suitable for use inflashlights, such as button cells, carbon-zinc batteries in both regular and heavy duty types, alkaline , lithium andrechargeable lead acid batteries, NiMH, NiCd batteries and lithium ion batteries. The choice of batteries will depend on the light source used, and will usually play a determining role in the size and shape of the flashlight. Flashlightsadapted for use with secondary batteries may include features to allow charging without removing the batteries from the light, for example, a light kept in a vehicle may be trickle-charged and always ready when needed. At least one manufacturer makes a rechargeable flashlight that uses a supercapacitor to store energy.

Some flashlights are solar powered, using the energy generated from a solar cell to charge an on-board battery for later use.

Incandescent

Incandescent

The flashlight on the left uses anincandescent bulb, while the one on the right uses LEDs to give white, red, blue, andinfrared light

Incandescent flashlights use incandescent light bulbs which consists of a glass bulb and a tungsten filament. The bulbs are under vacuum or filled with argon,krypton or xenon. Some high-power incandescent flashlight use a halogen lamp where the bulb contains trace of halogen such as iodine or bromine to improve the life and efficacy of the bulb.

The light output of an incandescent lamp in a flashlight varies widely depending on the type of lamp. A miniature keychain lamp produces one or two lumens. A two D-cell flashlight using a common prefocus-style miniature lamp will produce on the order of 15 to 20 lumens of light ^[7] and a beam of about 200candlepower. One popular make of rechargeable focusing flashlight uses a halogen lamp and produces 218 lumens. By comparison, a 60-watt household incandescent lamp will produce about 900 lumens.

Miniature incandescent bulbs for use inflashlights. The tungsten filament bulb was essential to turn the flashlight from a novelty to a useful tool.

LED

Two LED flashlight extremes: Olight SR90 2.200 lumen (left), 4sevens Quark Mini CR2 180 lumen (right), AA battery for size recognition

Developments in light-emitting diodes (LED)s have made practical flashlights that use LEDs instead of conventional light bulbs. LEDs have existed for decades, mainly used as low-power indicator lights. In 1999, Lumileds Corporation of San Jose, California United States, introduced the Luxeon LED, a high-power white-light emitter. This made possible LED flashlights with power and running time better than incandescent lights. The first LuxeonLED flashlight was the Arc LS, designed in 2001^{[citation needed]}.

LEDs can be significantly more efficient and use less energy than incandescent lamps. LED flashlights have longer battery lifetimes than incandescent lamps of comparable light output. LEDs are also less fragile than conventional glass lamps.

Some LED flashlights electronically regulate the voltage supplied to the LEDs to stabilize light output as the batteries discharge. By contrast, the light output of non-regulated flashlights declines as battery voltage declines. LEDs also have the advantage of maintaining nearly constant color temperature regardless of input voltage or current, while the color temperature of an incandescent bulb rapidly declines as the battery discharges. Regulated LED flashlights may also have user-selectable levels of output appropriate to a task, for example, low light for reading a map and high output for checking a road sign. This would be difficult to do in an incandescent flashlight since efficacy of the lamp drops rapidly at low output.

LED flashlights may consume 1 watt or more from the battery, producing heat as well as light. Heat dissipation for the LED often dictates that LED flashlightshave aluminum bodies to dissipate heat; they can become warm during use.

Light output from LED flashlights varies even more widely than for incandescent lights. "Keychain" type lamps operating on button batteries, or lights using a single 5 mm LED, may only produce a couple of lumens. Even a small LED flashlight operating on an AA cell but equipped with a power LED can emit 100 lumens. The most powerful LED flashlights produce more than one thousand lumens and may use multiple power LEDs.

LEDs are highly efficient at producing colored light compared with incandescent lamps and filters. Colored LED flashlights are used for signalling, special inspection tasks, forensic examination, or to track the blood trail of wounded game animals. A flashlight may have a red LED intended to preserve dark adaption of vision. Ultraviolet LEDs may be used for inspection lights, for example, detecting fluorescent dyes added to air conditioning systems to detect leakage. Infrared LEDs can be used for illuminators for night vision systems.

HID

Another less common type of flashlight uses a High Intensity Discharge (HID) lamp as the light source. HID is a type of gas discharge lamp that uses a mixture of metal halide salts and argon as a filler.

HID lamps produce more light than an incandescent flashlight using the same amount of electricity. The lamp will last longer and is more shock resistant than a regular incandescent bulb, since it lacks the relatively fragile electrical filament found in incandescent bulbs. However, they are much more expensive, due to the ballast circuitry required to start and operate the lamp.

A typical HID flashlight would have a 35 watt lamp and produce more than 3000 lumens.