Lighting measurements

LED and Solid state lighting [SSL] is often referred to as the light of the future: combining low energy consumption, efficient technology and long product life times. An inherent challenge to the production process of LEDs and Solid State Lighting products are driver related  variations in their optical characteristics such as brightness, colour and flicker, even in the same production batches. In order to assure a high-end lighting product, it is necessary to measure these optical characteristics during the development of LEDs and perform a 100% inspection during the production processes. Typical LED – SSL measurements include:

  • Spectral power distribution to determine a light source’s total emitted power for each individual wavelength revealing information like for example colour, CRI, CCT and many more.
  • Radiance, irradiance & radiant intensity measurements to measure the amount of radiant power in W/m²/sr, W/m² and W/sr and parameters such as PAR.
  • Luminance, illuminance & luminous intensity measurements to determine the light output in candela per square meter, lux and candela respectively.
  • Flicker measurements to determine and adjust for flickering of light sources. Currently supported: flicker %, index and IEEE 1789 recommendation.
  • 2D luminous surfaces meto determine aspects such as uniformity of large luminous panels or surfaces.
Geometry & optical configurations
Optical configuration Radiometric Spectroradiometric Photometric
Integrating sphere

Radiant power

Watt [W]

Spectral radiant power

[W/nm]

Luminous power

[lm]

Cosine corrector*

Irradiance

[W/m²]

Spectral irradiance

[W/m²/nm]

Illuminance

[lm/m² = lux]

Cosine corrector*

Radiant intensity

[W/sr]

Spectral radiant intensity

[W/sr/nm]

Luminous intensity

[lm/sr = cd]

Lens

Radiance

[W/m²/sr]

Spectral radiance

[W/m²/sr/nm]

Luminance

[lm/m²/sr = cd/m² = nit]

Flicker measurements can be carried out in combination with any of the optical configurations mentioned in the table above.

*Instead of cosine correctors, integrating spheres can also be used to determine [spectral] irradiance and radiant intensity / illuminance and luminous intensity.