Goniospectrometry – Article from Instrument Systems

Goniophotometers are normally used for the determination of illuminance and luminous

intensity distributions. They are also applied for measurements of the total luminous

flux by appropriate numerical integration of these distributions. Although determining the luminous flux with a goniophotometer is much more timeconsuming by comparison with measurement in an integrating sphere, it is significantly more accurate.

This method adds up the measured values for illuminance in all the angle positions around a light source, as shown in the diagram in Fig. 1. This approach is preferred by leading national laboratories which provide reference values for other measurement procedures.

A goniophotometer is absolutely essential if parameters like partial luminous flux or beam angle are to be determined for light sources, as is the case in characterization for energy efficiency.
The goniophotometer unit can be used with both a conventional photometer and a spectroradiometer depending on the test objective.