Thermopile detectors: spatial non-uniformity measurements and correction methods

The spatial non-uniformity of a newly developed electrically calibrated rad iometer system is characterized. The detector is a thin-film thermopile wit h an integral electrical heater. This paper shows that the local responsivi ties of these detectors have a rotational symmetry and a quadratic dependen ce on the distance to the centre of the detector. Typical measurement error s, which can be caused by applying different beam sizes, different power di stributions of the beams, and different beam positions impinging on the det ector, are investigated. A significant reduction of measurement uncertainti es is achieved using specific corrections. The influence of spatial non-uni formity on responsivity measurements is experimentally checked with various types of beam.