View showing Cardiff E.T.T. Angular Photometer being set up for use. Its purpose as an Angular Photometer (Photogoniometer) is to provide directional light emission data concerning glazing materials and light fittings (luminaires). This particular model also gives spectral (ie colour) information. The detection system consists of a movable telescope head feeding an optical fibre. The fibre carries the light sample to a spectrometer. The movement and the spectrometer are under computer control, with microcontrollers performing the local instructions for all the hardware. The microcontroller systems are custom built by Cardiff ETT.

A typical output graph is shown here (tilted to match the photo), in this case representing the angular and intensity data. The software can be customised for the user.

Manufacturers of vehicle lights, room lights and windows make use of photogoniometer data, as do those involved in architectural design.

(Photos with kind permission of   Jean LJ Rosenfeld, , Jan Breitenbach)