List of LED applications
Status indicators on all sorts of equipment
Traffic lights and signals
Light source for machine vision systems, requiring bright, focused, homogeneous and possibly strobed illumination.
Motorcycle and Bicycle lights
Toys and recreational sporting goods, such as the Flashflight
Railroad crossing signals
Flashlights, including some mechanically powered models.
Light bars on emergency vehicles.
Elevator Push Button Lighting
Thin, lightweight message displays at airports and railway stations and as destination displays for trains, buses, trams and ferries.
Red or yellow LEDs are used in indicator and alphanumeric displays in environments where night vision must be retained: aircraft cockpits, submarine and ship bridges, astronomy observatories, and in the field, e.g. night time animal watching and military field use.
Red, yellow, green, and blue LEDs can be used for model railroading applications
Remote controls, such as for TVs and VCRs, often use infrared LEDs.
In optical fiber and Free Space Optics communications.
In dot matrix arrangements for displaying messages.
Glowlights, as a more expensive but longer lasting and reusable alternative to Glowsticks.
Grow lights composed of LEDs are more efficient, both because LEDs produce more lumens per watt than other alternatives, and also because they can be tuned to the specific wavelengths plants can make the most use of.
Movement sensors, for example in optical computer mice
Because of their long life and fast switching times, LEDs have been used for automotive high-mounted brake lights and truck and bus brake lights and turn signals for some time, but many high-end vehicles are now starting to use LEDs for their entire rear light clusters. Besides the gain in reliability, this has styling advantages because LEDs are capable of forming much thinner lights than incandescent lamps with parabolic reflectors. The significant improvement in the time taken to light up (perhaps 0.5s faster than an incandescent bulb) improves safety by giving drivers more time to react. It has been reported that at normal highway speeds this equals 1 car length increased reaction time for the car behind.
Backlighting for LCD televisions and displays. The availability of LEDs in specific colors (RGB) enables a full-spectrum light source which expands the color gamut by as much as 45%.
New stage lighting equipment is being developed with LED sources in primary red-green-blue arrangements.
Lumalive, a photonic textile
LED-based Christmas lights have been available since 2002, but are only now beginning to gain in popularity and acceptance due to their higher initial purchase cost when compared to similar incandescent-based Christmas lights. For example, as of 2006, a set of 50 incandescent lights might cost $2.00 USD, while a similar set of 50 LED lights might cost $10.00 USD. The purchase cost can be even higher for single-color sets of LED lights with rare or recently-introduced colors, such as purple, pink or white. Regardless of the higher initial purchase price, the total cost of ownership for LED Christmas lights would eventually be lower than the TCO for similar incandescent Christmas lights since an LED requires much less power to output the same amount of light as a similar incandescent bulb.
LED phototherapy for acne using blue or red LEDs has been proven to significantly reduce acne over a 3 month period.
As a medium quality voltage reference in electronic circuits. The forward voltage drop (e.g. about 1.7 V for a normal red LED) can be used instead of a Zener diode in low-voltage regulators. Although LED forward voltage is much more current-dependent than a good Zener, Zener diodes are not available below voltages of about 3 V.
Computers, for hard drive activity and power on. Some custom computers feature LED accent lighting to draw attention to a given component. Many computer manufactuers use LEDs to tell the user its current state. One example would be the Mac, which tells its user when it is asleep by fading the LED activity lights in and out, in and out.
LEDs used as a replacement for incandescent light bulbs and fluorescent lamps are known as solid-state lighting (SSL) - packaged as a cluster of white LEDs grouped together to form a light source. LEDs are moderately efficient; the average commercial SSL currently outputs 32 lumens per watt (lm/W), and new technologies promise to deliver up to 80 lm/W. The long lifetime of LEDs make SSL very attractive. They are also more mechanically robust than incandescent light bulbs and fluorescent tubes. Currently, solid state lighting is becoming more available for household use but is relatively expensive, although costs are decreasing. LED flashlights, however, already have become widely available.
One 6 watt LED light bulb can potentially last up to 58,500 or more hours than a 60 watt incandescent bulb, and potentially 50,000 more hours than a CFL. The cost difference between 40 incandescent light bulbs and 1 LED light bulb is only a few dollars, however, the kWh usage is significantly smaller with an LED light. Over this period of time, a significant amount of money can be saved. LEDs will also contribute by producing less waste.
A number of manufacturers have started marketing ultra-compact LCD video projectors that use high-powered white LEDs for the light source. Another alternative design is to use red, green, and blue LEDs in a sequential DLP design.
Incandescent bulbs are much less expensive but also less efficient, generating from about 16 lm/W for a domestic tungsten bulb to 22 lm/W for a halogen bulb. Fluorescent tubes are more efficient, providing 50 to 100 lm/W for domestic tubes (average 60 lm/W), but are bulky and fragile and require starter or ballast circuits. Compact fluorescent lamps, which include a quiet integrated ballast, are relatively robust and efficient and fit in standard light bulb sockets. They are currently the best choice for efficient household lighting if one overlooks the poisonous mercury they contain.
LEDs are now well established in applications such as traffic signals and indicator lamps for trucks and automobiles. High output LED fixtures suitable for general architectural lighting applications are beginning to appear on the market with system efficacies of up to 56 lumens per watt, which is comparable to fluorescent systems. Proponents of LEDs expect that technological advances will reduce costs such that SSL will replace incandescent and fluorescent lighting in most commercial and residential applications.
LED downlights in NYC advertising agency officeDue to their monochromatic nature, LED lights have great power advantages over white lights when a specific color is required. Unlike traditional white lights, the LED does not need a coating or diffuser that can absorb much of the emitted light. LED lights are inherently colored, and are available in a wide range of colors. One of the most recently introduced colors is the emerald green (bluish green, about 500 nm) that meets the legal requirements for traffic signals and navigation lights.
There are applications that specifically require light without any blue component. Examples are photographic darkroom safe lights, illumination in laboratories where certain photo-sensitive chemicals are used, and situations where dark adaptation (night vision) must be preserved, such as cockpit and bridge illumination, observatories, etc. Yellow LED lights are a good choice to meet these special requirements because the human eye is more sensitive to yellow light (about 500 lm/watt emitted) than that emitted by the other LEDs.
The first residence lit solely by LEDs was the "Vos Pad" in London. The entire flat is lit by a combination of white and RGB (color changing) LEDs.
Light sources for machine vision systems
Machine vision systems often require bright and homogeneous illumination, so
features of interest are easier to process. LEDs are often used to this purpose,
and this field of application is likely to remain one of the major application
areas until price drops low enough to make signalling and illumination
applications more widespread. LEDs constitute a nearly ideal light source for
machine vision systems for several main reasons:
Size of illuminated field is usually comparatively small and Vision systems or smart camera are quite expensive, so cost of LEDs is usually a minor concern, compared to signaling applications.
LED elements tend to be small and can be placed with high density over flat or even shaped substrates (PCBs etc) so that bright and homogeneous sources can be designed which direct light from tightly controlled directions on inspected parts.
LEDs often have or can be used with small, inexpensive lenses and diffusers, helping to achieve high light densities and very good lighting control and homogeneity.
LEDs can be easily strobed (in the microsecond range and below) and synchronized; their power also has reached high enough levels that sufficiently high intensity can be obtained, allowing well lit images even with very short light pulses: this is often used in order to obtain crisp and sharp "still" images of fast moving parts.
LEDs come in several different colors and wavelengths, easily allowing to use the best color for each application, where different color may provide better visibility of features of interest. Having a precisely known spectrum allows tightly matched filters to be used to separate informative bandwidth or to reduce disturbing effect of ambient light.
LEDs usually operate at comparatively low working temperatures, simplifying heat management and dissipation, therefore allowing plastic lenses, filters and diffusers to be used. Waterproof units can also easily be designed, allowing for use in harsh or wet environments (food, beverage, oil industries).
LED sources can be shaped in several main configurations (spot lights for reflective illumination; ring lights for coaxial illumination; backlights for contour illumination; linear assemblies; flat, large format panels; dome sources for diffused, omnidirectional illumination).
Very compact designs are possible, allowing for small LED illuminators to be integrated within smart cameras and vision sensors.
Considerations in use