IMPROVED SPECTRAL RESPONSIVITY SCALES AT THE NPL, 400-NM TO 20-MU-M

Two spectral responsivity scales have been established at the National Physical Laboratory, UK. High quantum efficiency silicon photodiodes have been used to establish a continuous spectral responsivity scale for the spectral region 400 nm to 920 nm. The scale can be disseminated by the NPL with an uncertainty of +/- 0,1%. Pyroelectric detectors fitted with a reflecting hemispherical cavity have been used to establish a spectral responsivity scale for the spectral region 1 mum to 20 mum. This scale has an uncertainty of less than +/- 1,6%.