Linear Variable NIR Band Pass Filter

Delta has introduced a new type of linear variable filter (LVF). The linear variable NIR band pass filter extends the wavelength range into the NIR up to 1000nm.

A linear variable filter band pass (LVFBP) is a wedged filter, whose spectral properties vary linearly along the long side of the filter. It is possible to adjust the centre wavelength by sliding the filter with respect to the incident light.

A single LVF can replace a number of dedicated filters in an instrument and thereby decrease complexity and cost. This opens up new design possibilities for analytical and diagnostic instruments such as spectrometers.

By combining linear variable short and long pass filters, band pass filters can be constructed that can be tuned continuously with centre wavelengths from 320nm to 850nm, with the added benefit of tunable bandwidth.

The filters offer blocking levels better than OD 3 over the complete reflection range or even OD 5 by placing two filters in series.

The filters are coated on single quartz substrates for minimal auto-fluorescence and high laser damage threshold. All of DELTA's LVF are coated with ultra-hard surface coatings (UHC) that offers much higher packing density than traditional hard coatings.

The benefits of UHC are better spectral stability (no spectral drift), increased lifetime, mechanical stability, and minimal water uptake. This brings use of advanced filter technology out of the laboratory and into the field.