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LED Technology Glossary

LED Technology Glossary

              

A


Adobe RGB - The RGB (Red, Green, Blue) colors created by Adobe Systems providing a large gamut of colors that is well suited for printing CMYK (Cyan, Magenta, Yellow, Black) documents.
AllnGaP - The preferred LED (Light Emitting Diode) chip technology containing Aluminum, Indium, Gallium, and Phosphorous to produce red, orange and amber-colors.
Ampere (Amp) - The unit for measuring rate of flow of electrical current: Current (Amps) = Power (Watts) / Voltage (Volts)


B

Bin - The systematic dividing of distribution of performance parameters (Flux, Color or CCT, and Vf) in to smaller groups that meet aesthetic requirements of the assembly. Although the word "bin" is the preferred term, sometimes one will find the word "rank" in use.
Binning - Subdivision of the manufactured distribution into bins common operating parts (color, flux, forward voltage)


C

Candela (cd) - The luminous intensity as defined by the international metric standard (SI). The term, retained from the early days of lighting, defines a standard candle of a fixed size and composition as a basis for evaluating the intensity of other light sources.
CCFL - Cold Cathode Fluorescent Lighting: Often used as a backlight for LCD displays and usually containing Mercury (Hg) or other regulated heavy metals.
CIE Chromaticity Diagram - A horseshoe shaped line connecting the chromaticities of the spectrum of colors. (See Color Definition, Chroma)
Color Definition - The color of uniformly illuminated objects described using three terms:
Hue: Describes the situation when the appearance of different colors is similar (e.g. matching blues and pinks).
Lightness: Describes a range of grayness between black and white.
Chroma: Describes the degree of departure from gray of the same lightness and increasing color (e.g. red, redder, pure red).
Color gamut - The range of colors within the CIE Chromaticity Diagram included when combining different sources.
Color spectrum - All wavelengths perceived by human sight, usually measured in nanometers (nm).
Color temperature - The description used to describe the effect of heating an object until it glows incandescently, the emitted radiation, and apparent color, changes proportional to the temperature; easily envisioned when considering hot metal in a forge that glows red, then orange, and then white as the temperature increases.
Cool White - A description of light with a correlated color temperature between 5000K and 7500K, usually perceived a slightly blue.
Correlated Color Temperature (CCT) - The phrase use to describe the temperature at which a Planckian Black Body Radiator and an illumination source's appear to match, usually specified in Kelvin (K).
CRI or Color Rendering Index - The calculated rendered color of an object. The higher the CRI (based upon a 0-100 scale), the more natural the colors appear. Natural outdoor light has a CRI of 100. Common lighting sources have a large range of CRI.
For example:
Cool White CRI = 62
Luxeon CRI = 70
Vita-Lite CRI = 91


D

Die - chip: heart of the LED
Diffuser - An optical element used to mix light rays to improve uniformity.
Driver - Electronics used to power illumination sources. Ballast.

E
 
Efficacy - (Luminous Efficacy) - The light output of a light source divided by the total electrical power input to that source, expressed in lumens per watt (lm/W).
Epoxy - Organic polymer frequently used for a dome or lens, often prone to optical decay over time, resulting in poor lumen maintenance. Luxeon power light sources contain no epoxy and deliver superior lumen maintenance.
 
F

Flux - The sum of all the lumens (lm) emitted by a source (see lumen).

I

InGaN LED - The preferred LED (Light Emitting Diode) semiconductor technology containing Indium, Gallium, and Nitrogen to produce green, blue and white-colored LED light sources.

K

Kelvin Temperature - Term and symbol (K) used to indicate the comparative color appearance of a light source when compared to a theoretical blackbody. Yellowish incandescent lamps are 3000K. Fluorescent light sources range from 3000K to 7500K and higher.

L

LED - A Light Emitting Diode (LED) is a solid-state semiconductor device that converts electrical energy directly into light. On its most basic level, the semiconductor is comprised of two regions. The p-region contains positive electrical charges while the n-region contains negative electrical charges. When voltage is applied and current begins to flow, the electrons move across the n region into the p region. The process of an electron moving through the p-n junction releases energy. The dispersion of this energy produces photons with visible wavelengths.
Levels:
Level 1 - The chip or die
Level 2 - The LED component
Level 3 - LED array; may include optics, heat sink and/or power supply
Level 4 - LED luminaire
Lumen (lm) - The international (SI) unit of luminous flux or quantity of light and equals the amount of light that is spread over a square foot of surface by one candle power when all parts of the surface are exactly one foot from the light source. For example, a dinner candle provides about 12 lumens. A 60-Watt Soft White incandescent lamp provides 840 lumens.
Lumen maintenance - The remaining flux percentage at the rated life of a light source.
Lumen Maintenance Curve - A graph comparing the loss of light output against the time the light source is used.
Luminaire - A lighting fixture complete with installed lamps and other accessories.
Lux (lx) - The SI (International) unit of illuminance, or luminous flux incident on a unit area, frequently defined as one lumen per square meter (lm/m2).

M

Metameric - The term used to describe the visual perception phenomenon where spectrally different sources blend into a third chroma. For example, Sir Isaac Newton discovered that people perceive white when observing mixed blue and yellow light.
 
N

Nits - Measurement of display screen brightness. 1 nit = 1 cd/m2. The more nits, the brighter the picture.
NTSC color space - The range of colors within the CIE Chromaticity Diagram included when combining phosphor based RGB sources in CRTs such a televisions and computer monitors.

O

Optic - A device that changes the direction of a ray of visible light, usually by reflection, such as a mirror, or refraction by a lens.

P

P-N Junction - Area on an LED chip where the positively and negatively charged regions meet. When voltage is applied and current begins to flow, the electrons move across the n region into the p region. The process of an electron moving through the p-n junction releases energy. The dispersion of this energy produces photons with visible wavelengths. In short, the area on a chip where light is produced.
Planckian Black Body Locus - The line on the CIE Chromaticity Diagram that describes the color temperature of an object when heated from approximately 1,000K to more than 10,000K.

S

Solid-state lighting - A description of the devices that do not contain moving parts or parts that can break, rupture, shatter, leak or contaminate the environment.
sRGB - A Standard Default Color Space for the Internet created by Hewlett-Packard and Microsoft to support a standard color space within the Microsoft operating systems, HP products, and others.

T

Thermal management - Controlling the operating temperature of the product through design, examples includes heat sinks and improved airflow.
Thermal resistance (C/W) - A measure of the heat transfer capacity of the LED. Lower resistance is preferred.

V

Volt - The term used to describe the electrical potential difference between oppositely charged conductors, for example there is a 1.5V potential between the top and bottom of a battery.

W

Warm White - A description of light with a correlated color temperature between 3000K and 3500K, usually perceived a slightly yellow.
Watt - The unit of electrical power as used by an electrical device during its operation. Many lamps come with rating in watts to indicate their power consumption. A light source with a higher lumen per watt value is more efficient.
White point - The Coordinated Color Temperature (CCT) defined by a line perpendicular to the Planckian Black Body Curve and intersecting the measured chromaticity.

 

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