variable area of the chromaticity diagram). Luminous Flux (the BIN defines the amount
of luminous flux emitted). Vf (the BIN specifies the maximum and minimum values of
the voltage drop applied across the LED terminals)
Black body
It is an ideal object absorbing all incident electromagnetic radiations. Being black, it is
neither reflecting nor transmitting any energy. The black body produces electromag-
netic radiation as a consequence of its temperature.
C
Candela
SI unit of luminous intensity: the candela (cd) is the luminous intensity, in a given
direction, of a light source that emits monochromatic radiation at a frequency of 540
THz and whose energy intensity in that direction is equal to 1/683 W per steradian.
Candela per square metre (m-2)
SI unit of luminance.
Catadiottric optic
Optical system usually mixed (refractive + reflective) on which reflection takes place,
both because of the TIR principle and because of the use of mirrors.
CCT
Acronym of Correlated Color Temperature. It is expressed by the colour temperature
in Kelvin degrees of a specific colour while in proximity of the black body curve in the
different cromatic diagrams.
Cd/klm
Measurement unit of the luminous intensity. It is expressed in candles and is referred
to the luminous flux installed, expressed in Kilo lumens.
Chromatic Rendering Index
Index evaluated by the ability to render a series of 14 colours, chosen using Munsell
chromatic system, compared to a reference source depending on the colour temper-
ature. If the colour temperature is below 5,000K, the reference source is the black
body spectrum with the same colour temperature. If the CRI is higher, then the chosen
reference source is a series D illuminant with colour temperature similar to the one of
the source chosen.
Chromaticity diagram
Plane diagram in which the points, defined by the respective trichromatic coordinates,
represent the chromaticity of colour stimuli.
