4G Continuously Variable Filters launched by Delta Optical Thin Film A/S

24 Jan 2020

Delta Optical Thin Film has utilised its decades of experience to develop the 4th generation Continuously Variable Short Wave Pass and Continuously Variable Long Wave Pass Filters.

A continuously variable filter is a wedged filter that has spectral properties that vary continuously along one dimension of the filter. Just one of these filters can be used as an alternative to several fixed filters in an instrument, and the centre or edge wavelength can be adjusted by sliding the optical filter.

All continuously variable filters from Delta Optical Thin Film are coated with ultra-hard surface coatings, which are produced with an advanced plasma process that builds layers with a much higher packing density than traditional hard coatings. These optical filters set new standards in edge steepness and transmission level, and also provide improved blocking. Coated on a single fused silica substrate, these Continuously Variable Filters exhibit minimal auto-fluorescence and a high threshold to laser damage.

The combination of continuously variable long wave pass filters (CVLWP) and continuously variable short wave pass filters (CVSWP) enables the construction of bandpass filters, which can be tuned continuously between 410 nm and 895 nm. These filters also have the advantage of tunable bandwidth. The total wavelength range is split into two sets of CVFs: two CVLWP and two corresponding CVSWP. The physical length is longer than for the 3G CVF. This yields a higher spectral resolution with the same light spot. The blocking level (OD value) has increased, and the blocking range of the CVLWPs has been extended to 1025 nm. This removes the needs for additional blocking filters.

The four new filters are: