Technical

Electro-Optic Specifications (LED chips and packaged parts)

Visible Wavelengths (420 ~ 680 nm)

Term
units
  Description

Dominant

Wavelength

nm
nanometre Sometimes called the hue, the dominant wavelength is calculated from the CIE graph. It is the best specification to ensure colour repeatability between orders. Depending on the wavelength, tolerances of +- 2.5 nm and better can be guaranteed on low and high volume deliveries.
Intensity

mcd

cd

millicandella

1 candella = 1 lm/sr.

Sometimes called the brightness, the intensity refers to the amount of visible power (lumens) emitted by an LED, into a given solid angle (steradian, sr). NB: 1 sr is equal to a solid angle of 65.5 degrees, a hemisphere has a solid angle of 2 π sr.

Intensity values are the normal specification for comparing LED chip grades. However, for packaged LEDs, the beam angle has to be considered when comparing intensity. Eg, a LED chip producing an intensity of 100 mcd, can be packaged as a 300 mcd LED with a 5 degree beam angle, or packaged as a 50 mcd LED with a 100 degree beam angle.

Luminous Flux
lm
lumen This is the total amount of visible power emitted by the LED. This value is becoming more important for LEDs as they are used as alternatives to incandescent and other traditional lights.

Non-Visible Wavelengths (350 ~ 400 and > 680 nm)

Term
units
  Description
Peak Wavelength
nm
nanometre  
Radiant Intensity
mW/sr
milliwatts per steradian A useful measure of how much radiation is being emitted in a particular direction. Particularly important for packaged LEDs, where the application needs a certain amount of radiation in a target area.
Radiant Flux

mW

W

milliwatt

watt

Also called the radiant power, this is the total amount of radiant power emitted by the LED. This can be measured in an integrating sphere, or with a calibrated photometer.

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