Glossary

Additive Colour Model
A type of RGB Colour model that describes how different proportions of red, green, and blue light combine to create Colours. In the additive Colour model, combining red, green, and blue light produces white light.
AlGaAs
One of the material systems for manufacturing LEDs that produce light in the red and amber portions of the visible light spectrum.
AllnGaP
The preferred LED (Light Emitting Diode) chip technology containing Aluminum, Indium, Gallium, and Phosphorous to produce red, orange and amber-Colours.
Ambient Temperature (Ta)
The air temperature surrounding the device.
American National Standards Institute (ANSI)
A non-profit organization that develops voluntary consensus standards and conformity assessment systems for products, services, processes, systems, and personnel in the United States.
Ampere (Amp)
The unit for measuring rate of flow of electrical current: Current (Amps) = Power (Watts) / Voltage (Volts)
ANSI Binning
The system defined by the American National Standards Institute for the binning specifications for light emitting diodes.

B

Bin (Binning)
The systematic dividing of distribution of performance parameters (Flux, Wavelength or CCT, and Vf) in to small finite groupings that may be selected to optimize assembly performance.
Black Body / Black Body Radiator
An object that absorbs all electromagnetic radiation falling on it. Because it reflects no light, a black body appears black. As a black body is heated to incandescence, it radiates light in a sequence of Colours, from red to orange to yellow to white to blue, depending on its temperature. This Colour sequence describes a curve within a Colour space, known as the black-body curve.
Black Body Curve
A curve within a Colour space describing the sequence of Colours emitted by a black-body radiator at different temperatures.
Brightness
Often used incorrectly with respect to illumination as a synonym for luminous flux, an objective measurement of the visible power of a light source. The term is correctly used when describing screen brightness in a display or television. (see Nits).

C

Case Temperature
The temperature measured at the LED package or case.
CCT – See Correlated Colour Temperature.
Chip – See LED chip.
Chromaticity
An objective specification of the quality of a Colour, independent of its luminance, and as determined by its or saturation and hue.
CIE – See International Commission on Illumination.
CIE 1931 Colour Space
A Colour space created by the International Commission on Illumination (CIE) in 1931 to define the entire gamut of Colours visible to the average viewer.
CIE Chromaticity Diagram
A horseshoe shaped line connecting the chromaticities of the spectrum of Colours. (See Colour Definition, Chroma).
Colour Definition
The Colour of uniformly illuminated objects described using three terms:

Hue: Describes the situation when the appearance of different Colours 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 Colour (e.g. red, redder, pure red).

Colour Gamut
The range of Colours within the CIE Chromaticity Diagram included when combining different sources.
Colour Model
An abstract mathematical model describing the way Colours can be represented as groups of values or Colour components. RGB (Red-Green-Blue) is a Colour model with three Colour components, and CMYK (Cyan-Magenta-Yellow and Key (Black)) is a Colour model with four Colour components.
Colour Rendering
A general expression for the effect of a light source on the Colour appearance of objects.
Colour Rendering Index (CRI)
A measure of the degree of Colour shift objects undergo when illuminated by the light source as compared with those same objects when illuminated by a reference source of comparable Colour temperature. The reference source has a CRI of 100.
Colour Spectrum / Visible Spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye, typically between 390nm and 750nm.
Colour temperature
The description used to describe the effect of heating an object until it glows incandescently, the emitted radiation, and apparent Colour, 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.
Conformal Phosphor Coating
Phosphor application process that uniformly coats the LED chip with phosphor.
Controller
A device that controls the output of Colour-changing and tunable white lighting fixtures. Controllers typically have software components for configuring fixtures and designing and editing light shows, and hardware components for sending control data to fixtures.
Cool White
A description of a range of correlated Colour temperatures.
Correlated Colour Temperature (CCT)
The absolute temperature of a blackbody whose chromaticity most nearly resembles that of the light source. Usually specified in Kelvin (K). The lower the Kelvin temperature, the warmer the light feels, or appears.
CRI – See Colour Rendering Index.

D

DALI – See Digital Addressable Lighting Interface
Delivered Light
The amount of light a lighting fixture or lighting installation delivers to a target area or task surface, measured in footcandles (fc) or lux (lx).
Die
Chip: light emitting semiconductor.
Diffuser
An object with irregularities on a surface causing scattered reflections.
Digital Addressable Lighting Interface (DALI)
A digital communications protocol for controlling and dimming lighting fixtures, originally developed in Europe.
Direct-View Lighting Fixtures
Lighting fixtures intended for viewing, rather than for illumination. For example, arrays of direct-view fixtures or nodes are used in large-scale video displays, traffic signals, and signage applications.
Directional Light Source
A light source that emits light only in the direction it is pointed or oriented.
DMX
A digital communications protocol for controlling lighting fixtures, originally developed to control stage lighting.
Driver
Electronics used to power illumination sources.

E

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).
Efficiency – See Luminous efficiency.
ELV-type Dimmer
An electronic low voltage dimmer, used to dim LED lighting fixtures with electronic transformers.
Epoxy
Organic polymer frequently used for a dome or lens, often prone to optical decay over time, resulting in poor lumen maintenance. High quality LEDs such as LUXEON contain no epoxy in the optical system and deliver superior lumen maintenance.
Eye-sensitivity Curve – See spectral luminous efficiency function.

F

Flux / Luminous Flux
Luminous flux is the measure of the perceived power of light, adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light
Forward voltage
LEDs are current driven devices. If an external current is passed through the device, a forward voltage will be developed across the diode.
FR4
A widely accepted printed circuit board (PCB) material which is fiberglass reinforced epoxy laminates that are flame retardant.
Freedom From Binning
Describes the case where the entire production of white LEDs can be described by a single CCT and within a declared number of MacAdam ellipses. No subdivision or Colour binning of the LEDs is required for use in the intended application.

G

Ghosting
An effect that occurs when lighting fixtures in the OFF state faintly glow as a result of residual voltage in the circuit.
Goniophotometer
A photometric device for testing the luminous intensity distribution, efficiency, and luminous flux of luminaires.

H

Heat Sink
A part of the thermal system that conducts or convects heat away from sensitive components, such as LEDs and electronics.
High Power LED
A high power LED, sometimes referred to as a power LED, is one that is driven at a current of 350 mA or higher.
High-brightness
High-brightness is a term that is often applied to an LED but has no measured meaning and does not indicate any level of performance.
Hot / Cold Factor
The relative light output performance at a temperature compared to the light output at a nominal or test temperature. For LUXEON products this is the relative light output at 100C Tj compared to 25C Tj. For “Hot Tested” products like LUXEON A it is the relative light output at 100C Tj compared to 85C Tj.
Hot Testing
LED performance testing and specification at an elevated temperature of 85°C.

I

IES / IESNA – See Illuminating Engineering Society.
Illuminance
The intensity of light falling on a surface area. If the area is measured in square feet, the unit of illuminance is footcandles (fc). If measured in square meters, the unit of illuminance is lux (lx).
Illuminating Engineering Society of North America (IES)
The recognized technical authority on illumination, communicating information on all aspects of good lighting practice to its members, to the lighting community, and to consumers through a variety of programs, publications, and services.
Inboard Power Integration
An approach to power management that integrates the power supply directly into a fixture’s circuitry, creating an efficient power stage that consolidates line voltage conversion and LED current regulation.
Infrared (Near)
Electromagnetic radiation with wavelength range from 700 nm – 3000 nm.
InGaN LED
The preferred LED (Light Emitting Diode) semiconductor material system containing Indium, Gallium, and Nitrogen to produce green, blue and white-Coloured LED light sources.
Integrating Sphere
A device used for a variety of optical, photometric, or radiometric measurements.

J

Junction Temperature
Junction temperature, noted as Tj, is the temperature of the LED’s active region.

K

Kelvin Temperature
Term and symbol (K) used to indicate the comparative Colour 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

Leading Edge Dimmer
A type of dimmer that regulates power to lamps by delaying the leading edge of each half-cycle of AC power. Compatible with many LED fixtures.
LED – See Light Emitting Diode.
LED Array
An assembly of LED packages or dies on a printed circuit board or substrate, possibly with optical elements and additional thermal, mechanical, and electrical interfaces that are intended to connect to the load side of an LED driver.
LED Chip (Chip)
The light producing semiconductor device that may or may not be incorporated into an LED.
LED Driver
An electronic circuit that converts input power into a current source — a source in which current remains constant despite fluctuations in voltage. An LED driver protects LEDs from normal voltage fluctuations, overvoltages, and voltage spikes.
LED Light Engine
An integrated assembly comprised of LEDs or LED arrays, LED driver, and other optical, thermal, mechanical, and electrical components.
LED Luminaire
A complete lighting unit consisting of LED-based light emitting elements and a matched driver together with parts to distribut light, to position and protect the light emitting elements, and to connect the unit to a branch circuit. The LED based light emitting elements may take the form of LED packages, (components), LED arrays (modules) LED Light Engine, or LED lamps. The LED luminaire is intended to connect directly to a branch circuit.
LED Module – See LED array.
Light Emitting Diode (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.
Light output – See luminous flux.
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
Lumen Depreciation
Describes the percentage of light lost relative to the initial lumen output. See lumen maintenance for more information.
Lumen Maintenance
The luminous flux at a give time in the life of the LED. This is expressed as a percentage of the intial luminous flux. [example L70, 50,000hours, leds will loose 30% brightness @ 50,000hours operation]
Lumen Maintenance Curve
A graph illustrating the predicted average light output behavior over time of a single LED or solution.
Lumen Output
The total lumens emitted of a light source, system, or solution.
Luminaire
A lighting fixture complete with installed lamps and other accessories.
Luminous Efficiency
The percentage of total lamp lumens that a lighting fixture, luminaire, or system emits, minus any blocked or wasted light.
Luminous Flux – See Flux.
Lumiramic
This Philips proprietary phosphor system embeds phosphor in a ceramic platelet that can be mass manufactured with very high degrees of uniformity and consistency.
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

MacAdam Ellipse
A MacAdam ellipse is the region on a chromaticity diagram which contains all Colours which are indistinguishable, to the average human eye, from the Colour at the center of the ellipse.
Material System
The material, such as aluminum indium gallium phosphide (AlInGaP) and indium gallium nitride (InGaN), used within an LED to produce light of a specific Colour.
MCPCB
A widely accepted Printed Circuit Board (PCB) material with a Metal Core (MC) for better thermal performance.

N

Nits
Measurement of display screen brightness. 1 nit = 1 cd/m2.
NTSC Colour Space
The range of Colours within the CIE Chromaticity Diagram included when combining phosphor based RGB sources in CRTs such a televisions and computer monitors.

O

Onboard Power Integration
An approach to power management that integrates the power supply into a fixture’s housing, eliminating the need for an external power supply.
Organic Light-emitting Diodes (OLED)
Organic light-emitting diodes (OLEDs) are based on organic (carbon based) materials. In contrast to LEDs, which are small point sources, OLEDs are made in sheets which provide a diffuse area light source. OLED technology is developing rapidly and is increasingly used in display applications such as cell phones and PDA screens. However, OLEDs are still some years away from becoming a practical general illumination source. Additional advancements are needed in light output, Colour, efficiency, cost, and lifetime.

P

P-N Junction
Area on an LED chip where the positively and negatively charged regions meet. When current is applied, 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.
P-type Material
In a diode’s p-n semiconductor junction, p-type material is positively charged. Atoms in the p-type material have electron holes — electrons missing from their outer rings.
PC Amber (Phosphor Converted)
PC amber is a method of making amber Coloured LEDs from royal blue LED chips. It requires the use of special phosphors and results in a more reliable, less temperature sensitive, and more consistent amber LED.
Phosphor
A coating of phosphorescent material which photons from a royal blue LED pass through causing those photons to exit with a different Colour property.
Phosphor Conversion
This is the process by which photons from an LED chip are converted to a different Colour. White LEDs and some Coloured LEDs are made using phosphor conversion.
Planckian Black Body Locus
The line on the CIE Chromaticity Diagram that describes the Colour temperature of an object when heated from approximately 1,000K to more than 10,000K.
Power Factor
The active power divided by the apparent power (i.e., product of the rms input voltage and rms input current of a driver).
Power Factor Correction
In an electronic device, such as an LED lighting fixture, a system of inductors, capacitors, or voltage converters to adjust the power factor of electronic devices toward the ideal power factor of 1.0.
Pulse Width Modulation (PWM)
A method, used by LED drivers, to regulate the amount of energy to the LEDs. PWM turns LEDs on and off at high frequency, reducing total ON time to achieve a desired dimming level.

R

Radiant Flux
The total energy emitted by a light source across all wavelengths, measured in watts.
Radiometry
The measurement of radiant energy (including light) in terms of absolute power. Compare photometry.
Remote Phosphor
A phosphor conversion technique in which photons from a royal blue LED pass through a phosphor material that is not attached to the LED chip.
RGB Colour Model
An additive Colour model in which red, green, and blue light are added together in different proportions to produce a broad range of Colours, including white.
RGB White
A method of producing white light by combining the output from red, green, and blue LEDs.

S

SDCM – See standard deviation of Colour matching.
SMDs
Surface-mount LEDs.
Solder Point Temperature (Ts)
Solder point temperature as specified by ENERGY STAR® and Philips Lumileds Application Brief 33.
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.
Spectral Luminous Efficiency Function
A bell-shaped curve describing the sensitivity of a human eye with normal vision to the spectrum of visible light. Also known as the eye-sensitivity curve.
sRGB
A Standard Default Colour Space for the Internet created by Hewlett-Packard and Microsoft to support a standard Colour space within the Microsoft operating systems, HP products, and others.
Standard deviation of Colour matching (SDCM)
Describes the difference between two Colours. A difference of one to three SDCM “steps” is virtually imperceptible, a difference of four SDCM steps is just noticeable, and a difference of more than four SDCM steps is readily visible.
Steradian
The standard unit of solid angle. Describes two-dimensional angular spans in three-dimensional space.
Subtractive Colour Model
A Colour model that applies to reflective surfaces such as paints, dyes, and inks. Combining red, green, and blue in equal amounts produces black.

T

Ta – See Ambient Temperature
Tc – See Case Temperature
Thermal management
Controlling the operating temperature of the product through design, examples includes heat sinks and improved airflow.
Thermal Pad Temperature
The measured temperature of the thermal pad during tesing. The thermal pad aides in the conduction of heat away from the component being cooled and into the heatsink. For more information refer to LUXEON® Rebel and LUXEON® Rebel ES Assemby and Handling Guide application brief 32.
Thermal Resistance (K/W)
The property of a material’s ability to conduct heat.
Tj – See Junction Temperature
Tp – See Thermal Pad Temperature
Trailing Edge Dimmer
A type of dimmer that regulates power to lamps by delaying the end of each half-cycle of AC power. Compatible with many LED fixtures.
Ts – See Solder Point Temperature.
Tunable White Light
White-light LED fixtures that combine channels of warm white and cool white LEDs to produce a range of Colour temperatures.

U

Ultraviolet (UV)
Electromagnetic radiation with wavelength shorter than that of visible light.
Useful Life
The amount of light a lighting fixture delivers in an application, minus any wasted light.

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 an AAA battery.

W

Wall Plug Efficiency
This typically refers to the effectiveness of converting electrical power to light output. It is defined as the ratio of the radiant flux to the input electrical power.
Warm White
A description of light with a correlated Colour 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.
White Point
The Coordinated Colour Temperature (CCT) defined by a line perpendicular to the Planckian Black Body Curve and intersecting the measured chromaticity. 

 

MEGALED Glossary/Terminology

  • Edge Lit Signage
    MegaLED’s complete selection of edge lit signs covers, two main types:

    Edge Lit Glass Signage

    • Brite-Fix – Original Edge Lighting Signage system by MegaLED, award winning, developed 2002 based on original design concept based on minamalist module placements (not full width profiles).
    • NANO – Wall and slot mounted edge lit sign system, seamless picture frame concept inspired by “IMAC”.
    • Edge-Line – Latest super slimline glass edge lit signage system for wall mounted signage.

    Edge Lit Acrylic Signage

    • ABlade – Where the Brite-Fix design reality is transposed onto acrylic signs and MegaLED get super creative with their original sign panel decorations.
  • Edge Lit Signs
    Custom signage consisting; planar panel in glass or acrylic decorated with logo or customer artwork by suitable decoration method and illuminated with LEDs on any of the edges or inside edges of the panel.
  • LED Controllers
    A device used to dim or animate leds, to set lighting levels or to a sequence.
  • Light Guide
    A light guide is a device designed to transport light from a light source to a point at some distance with minimal loss.
  • Voltage Controller Drivers
    A led controller for ultra-bright and medium power leds driven at constant voltage.
  • Power LED Controller Drivers
    A led controller for power leds that are typically driven at constant current e.g. 350,500,700mA or more.
  • Modular Mixed LED System
    A hybrid led control system takes input signals from DMX, 0-10V or other means
    (such as usb, rs232) and drives leds at constant voltage or constant current depending
    on the output card used.
  • PC-DMX Light Control
    Computer connected programming devices which can be programmed then disconnected
    and used to output DMX signals in stand alone mode.
  • DMX LED CONTROLLERS
    LED controllers which take the DMX signal and output constant voltage or constant current.
  •  DMX Splitter
    A very useful interface product for simplifying DMX -Terminations or “daisy chain” return wiring associated with DMX.  DMX splitters are an ideal solution simplifying wiring in multi-room or multi-location LED Installations and, a must-have when more than 31 DMX devices need to be connected in the DMX wiring chain.
  • SignLED Illuminated Letters & Shapes
    Specialist sign lighting system developed by MegaLED over 7 years.