Blocking improved narrow-band filters for the UV-B region

Monitoring stratospheric ozone depletion with filter radiometers requires n arrow-band filters with outstanding parameters. First, depending on custome r specifications, the filter's central wavelength must meet an extremely pr ecise value between 290 and 320 nm. Second, this central wavelength must be unusually stable over long periods of time and under changing environmenta l conditions due to the very small shifts that must be detected in the stee p cutoff of the solar irradiance spectra. Third, the filter passband must h ave a very narrow bandwidth with steep cutoffs. Last, but not least, a stro ng attenuation of fight for longer wavelengths is essential while retaining high transmittance at the central wavelength. Data of improved UV-B narrow -band filters and a detailed description of attenuation of longer wavelengt hs in solar UV-B radiometers are presented. (C) 2001 Society of Photo-Optic al Instrumentation Engineers.