Characterisation of optical detectors using high-accuracy instruments

The facilities of the Metrology Research Institute at the Helsinki Universi ty of Technology, and methods for characterisation of optical detectors for spectral radiant intensity and irradiance responsivity, are described. The instrumentation for such characterisations includes a reference spectromet er with a number of auxiliary set-ups, and equipment for the spectral irrad iance measurements with a filter radiometer based on a trap detector. The m ethods of realising the spectral responsivity scales based on an absolute c ryogenic radiometer in house are addressed. The procedures and results of c haracterisation of a multipoint measuring system of photosynthetically acti ve radiation, by employing the available facilities, are briefly described. The absolute irradiance responsivity of the device is determined by using a photometric lamp, whose spectral irradiance has been measured with the fi lter radiometer. The combined standard uncertainty of this set of calibrati ons is 3.6% at the 1 sigma level. The uncertainty is caused almost complete ly by the multipoint measuring system. (C) 1999 Elsevier Science B.V. All r ights reserved.