DELTA Light & Optics Extends Wavelength Range of Linear Variable Filters

DELTA’s innovative family of linear variable filters is becoming more versatile by the introduction of solutions for an extended wavelength range

Press Release
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DELTA Filter
The continuously changing spectral properties of a LVF can clearly be recognised in this back light photograph.




January 19, 2012

By Dr.-Ing. Oliver Pust, Business Development Manager Optical Thin Film Filters – January 19, 2012

DELTA's linear variable filters are very well received in the market and provide flexible possibilities in designing tunable excitation and emission filters to manufactures of fluorescence systems and end users as well. A common wish reported back to us is an extended wavelength range of our linear variable filters into the near infrared spectrum. This wish is now accommodated in two different ways.

When using our linear variable short wave pass filter (LVSWP) at 340 nm, blocking is only provided up to 700 nm. In some applications this is not sufficient. In these cases DELTA is now able to provide a solution that provides strong blocking from 365 nm all the way up to 930 nm, which makes the filters much for versatile, for example together with a LVLWP in wavelength selectors for supercontinuum light sources.

The latest development in linear filter technology now enables DELTA to offer linear variable short and long wave pass filters that have a useable wavelength range from 410 nm up to 1000 nm. Now you can, by combining an LVSWP and an LVLWP with our new blocking solution, construct a linear variable band pass filter with tunable center wave length and bandwidth - without compromising the blocking in the complete wavelength range of 410 nm to 1000 nm.



A complete range of linear variable filters
An LVF is a wedged filter, whose spectral properties vary linearly along the long side of the filter. It is possible to adjust the position of the edge 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 for new design possibilities of analytical and diagnostic instruments such as spectrometers.

By combining linear variable short- and longpass filters, bandpass filters can be constructed that can be tuned continuously with center wavelengths from 320 nm to 850 nm or from 410 nm to 1000 nm, with the added benefit of tunable bandwidth.



Superior UHC production technology
Besides setting new standards in transmission level and edge steepness, the filters offer blocking levels better than OD 3 over the complete reflection range or even OD 5 by placing to 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 best spectral stability (no spectral drift), increased lifetime, optimal mechanical stability and minimal water uptake. This brings use of advanced filter technology out of the laboratory and into the field.

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