A Continuously Variable Filter (CVF) is a wedged filter, whose spectral properties vary continuously along one dimension.
A single CVF for example can replace a number of fixed filters in an instrument. It is possible to adjust the centre or edge wavelength by sliding the filter. Used in combination, continuously variable thin film optical filters from Delta Optical Thin Films allow simultaneous tuning of bandwidth and transmission peak wavelength. View the above video for a full explanation; there is a pdf of this available here
Delta Optical Thin Film has lifted the quality of variable filters to new levels by introducing a new powerful combination of continuously variable filters. Delta Optical Thin Film offers a Linear Variable Long Wave Pass filter (LVLWP), the corresponding Linear Variable Short Wave Pass filter (LVSWP) together with a Linear Variable Dichroic. Each of the filters can be used separately. Combining LVLWP and LVSWP enables the construction of band-pass filters that can be tuned continuously with center wavelengths from 320 nm to 850 nm, with the added benefit of tunable bandwidth. As LVF monochromator the filters are used in fluorescence microplate readers.
Besides setting new standards in transmission level and edge steepness, the filters offer blocking better than OD3 over the complete reflection range. It is possible to increase the blocking to beyond OD5 by placing another continuously variable filter in series.
The filters are coated on single quartz substrates for minimal auto-fluorescence and high laser damage threshold. All of Delta Optical Thin Film’s Continuously Variable Filters are coated with ultra-hard surface coatings (UHC) that are also used by Delta Optical Thin Film in traditional fluorescence filters.