Optometrics’ long pass cut-on filters are cored from selected color glasses which transmit radiation above and block radiation below a specified wavelength. The wavelength interval (transition interval) from blocking to maximum transmission is sharp, typically 25 to 35 nm. Long pass cut-on filters are identified by a cut-on wavelength, i.e. the wavelength at 50% of maximum transmission.
CUT-ON FILTER TERMINOLOGY
Long pass cut-on filters have an average high transmission of 85% from 15 to 20 nm above their cut-on wavelength to 2000 nm. Attenuation of radiation below the cut-on wavelength is due to absorption of the colorants in the glass and the thickness of the glass.
Superior blocking in Optometrics filters (0.001%) is due to the use of 3 mm thick color glass. Long pass cut-on filters are widely used for additional blocking of UV radiation and for high transmission of a broad spectral region above a specified wavelength.
Optometrics’ long pass cut-on filters are all epoxied in a black metal ring for easy mounting and handling and are 25.4 mm dia. x 9.65 mm thick. The cut-on wavelength is marked on all filters.
