Technology Glossary

Sources of term definitions: National Lighting Product Information Program (NLPIP), Lighting Research Center’s Lighting Education Online, the IEEE Standard Dictionary of Electrical and Electronics Terms (IEEE Std 100-1996).

A
A-lamp - The incandescent lamp most commonly used in North American households. The "A" designation refers to the lamp's bulbous shape.

Adobe RGB - This Red, Green and Blue (RGB) color management profile created by Adobe Systems Incorporated has been widely adopted as a working space because it provides a relatively large and balanced color gamut that can be easily repurposed for reproduction on a variety of devices. Find out more about the Adobe RGB (1998) color image encoding (PDF: 551k) used for the Adobe RGB (1998) color space.

Absorptance - The dissipation of light (radiation) within a surface or medium, caused by the conversion of radiant (luminous) energy to a different form of energy, usually heat, by interaction with matter. The absorption is the "missing piece", when comparing the total reflected and transmitted energy with the incident energy. The ratio of the total absorbed radiant or luminous flux to the incident flux is called absorptance. The standard unit of absorptance is percent (%) or a factor between 0 an 1. Absorptance can also be inferred from the transmission through a medium. If the %transmission of a certain wavelength is 70% then the material has a 30% Absorptance.

Actinic - The characteristic of radiation that indicates its capability to produce chemical change. In our industry the term is usually used with reference to UV radiation and its effects on biological systems. Actinic strips are used in UV processing to monitor the intensity of sources. The color or optical density of the strip changes with the exposure.

AllnGaP - The preferred LED (Light Emitting Diode) chip technology containing Aluminum, Indium, Gallium, and Phosphorous to produce red, orange and amber-colors.

Ambient Light - Ambient light is the light diffused in the environment surrounding a detector measuring the optical radiation from another source. This light contributes to the signal measured from the source. To make valid measurements, the contribution from the ambient light or background must be subtracted from each measurement.

Ampere (Amp) - The unit for measuring rate of flow of electrical current: Current (Amps) = Power (Watts) / Voltage (Volts)

Aperture - A hole through which radiant energy can pass. Angular aperture is the angle through which the most divergent rays can pass through a hole or lens. The aperture of a lens is often expressed in terms of an f/#. The f/# is the ratio of the focal length of the lens to its diameter. A lens with a focal length of 100mm and a diameter of 25mm would have an aperture of f/4.

Attenuator - A device which reduces the amount of energy reaching a sensor. Attenuators are typically used when the radiant energy would saturate a detector. The QNDS,QNDS2 and QNDS3 filters are attenuators that reduce flux density at the detector by factors of 10, 100 and 1000, respectively.

B
Bandwidth - Bandwidth describes the size of a spectral segment. A bandwidth of 10nm indicates a range of 10nm of radiation. This can be, for example, between 500nm and 510nm, 1000nm and 1010nm or an equal size segment anywhere in the spectrum.

Band Eliminator Filter - A band eliminator filter allows the wavelengths above and below the filter cutoff to pass while suppressing the wavelengths within the band. These filters are also called notch filters. A 500nm band eliminator filter with a band pass of 10 nm would suppress the wavelengths between 495nm and 505nm.

Beamwidth - The angular width of a cone of light whose apex is at the source. Beamwidth is usually defined as the angle subtended by a cone encompassing 90% of the energy.

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)

Black Body - A black body is an object that absorbs all radiant energy that hits it. When heated a black body emits a well defined characteristic spectrum which can be used in the characterizing the spectral responsivity of detectors. As there is no such thing as a perfect black body, black body simulators are used for this purpose.

C
Calibration - The process of normalizing the signal output from a detector to that of a detector defined as a standard (usually defined by National Institute of Standards and Technology (NIST) under identical illumination conditions). Calibration can also be accomplished by the use of a standard source (lamp) whose output energy at specific wavelengths and measurement distances are traceable to the standard lamp defined by the governing standards body (NIST).

Candela (cd) - The current SI unit of luminous intensity. One candela is equivalent to 1 lumen/steradian. Used to express both Beam Intensity (Beam Candela) and Mean Spherical Intensity (Mean Spherical Candela). Also referred to as Candlepower (cp).

Candela, beam (cd or eff cd) photometric intensity measurement - Sampling a very narrow angle of the input beam, beam candela is only representative of the lumens per steradian at the peak intensity of the beam. The sampling angle need not be defined. Can be measured in Candela (cd) for steady sources or Effective Candela (eff cd) for flashing sources.

Candela, effective (eff cd) - Unit of luminous beam intensity that has been weighted to the human eye's increased sensitivity to a flashing source.

Candela, Mean Spherical (cd) photometric intensity measurement - The luminous intensity of a source expressed in candelas. Measured in an integrating sphere, Mean Spherical Candela is the total output of the source in lumens divided by 4pi steradians in a sphere.

Candlepower (cp) - Old definition of luminous intensity. One candlepower (cp) was the luminous intensity of a standard candle made of whale wax, weighing 1/6 lb, 7/8 in. in diameter, and burning 120 grains per hour. The current SI unit for luminous intensity is the candela (cd). One candela (cd) is the same as one candlepower thus a source with a luminous intensity of 10 candelas could be referred to as a 10 candlepower source.

CCD - A CCD (charge coupled device) is a light detector with high sensitivity primarily in the visible spectrum. CCDs are typically made in either linear or two-dimensional arrays consisting of up to millions of individual detector elements. The 2D versions are used for image recording and are found in most digital camera used in both scientific and consumer applications.

CCFL - Cold Cathode Fluorescent Lighting: Often used as a backlight for LCD displays and usually containing Mercury (Hg) or other regulated heavy metals.

Chromaticity - The aspects of color associated with hue and saturation without reference to brightness.

Chromaticity (CIE) Coordinates - The proportion of the standard tristimulus values used in color matching. Colors are compared by their CIE X, Y, and Z coordinates.

CIE - The C