In 2000, a photogoniometer was designed to determine retro reflective properties of traffic signs and verify whether they satisfy the regulations. Soon, this setup was modified to allow characterization of traffic lights and light sources in general as well. The test object is mounted in the goniometer which can rotate the object in all directions. At a distance of 9 m from the object, the TOP100 luminance probe detects the emitted (or reflected in the case of retro reflective measurements) light in one direction. The luminance probe is connected with a spectrometer with CCD to allow spectral analysis. This allows the determination of the spectral radiant intensity pattern of light sources.


  • Measurement of the spectral radiance (W/sr.m².nm) or radiant intensity (W/sr.nm) of a light source
  • Determination of the spectrum, luminance (Cd/m²) and luminous intensity (Cd) of a light source
  • Determination of the  intensity pattern in 4 planes (C0, C90, C180 and C270) with y-interval of 2.5°
  • Determination of retro reflection of films and traffic signs

Calibration source

  • Bentham SRS8 calibration source: calibrated for spectral radiance and radiant intensity (by NPL) for the visible wavelength range (380 to 780 nm).


  • European norm for traffic lights (EN12368)
  • European norm for variable message signs (prEN12966)
  • CIE 121-1996 The Photometry and Goniophotometry of Luminaires
  • CIE 15-2004 Photometry
The photogoniometer
Topcom 100 camera
Spectrometer with CCD connected to the Topcom 100 camera