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Linear Variable Filters for Spectroscopy from Delta Optical Thin Film

Linear Variable Filters for Spectroscopy from Delta Optical Thin Film

A linear variable filter (LVF) is a wedged filter with linearly varying spectral properties. A single LVF is capable of substituting a number of dedicated filters in a device. The position of the edge can be adjusted by sliding the filter.

DELTA offers a suite of robust linear variable filters, including linear variable long wave pass filters (LVLWPs), and the corresponding linear variable short wave pass filters (LVSWPs) with a linear variable dichroic. These filters can be utilized separately.

The combination of LVLWP and LVSWP allows for creating band-pass filters which can be constantly tuned with center wavelengths between 320 nm and 850 nm, with the added advantage of tunable bandwidth.

Besides setting new benchmark in transmission level and edge steepness, the powerful filters provide better blocking when compared to OD3 over the entire reflection range. The blocking can be increased to beyond OD5 by introducing another linear variable filter in series.

Ultra-hard surface coatings are applied over all LVFs offered by DELTA. The filters are coated on single quartz substrates for high laser damage threshold and minimal auto-fluorescence. The LVFs from DELTA are specially designed for spectroscopy applications.

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Key Features

The following are the key features of LVFs offered by DELTA:

  • Ultra-Hard-Coated filters
  • Standard dimension for LVDichroic is a plate of 60 mm x 15 mm x 3 mm.
  • Standard dimension for LVVISBP is a plate of 60 mm x 12 mm x 2.5 mm
  • Standard dimension for LVOSF is a plate of 40 mm x 9 mm x 0,75 mm
  • Standard dimension for LVSWP, LVLWP, and LVUVBP is a plate of 60 mm x 15 mm x 3 mm
  • Scratch/dig optical surface specifications 60/40
  • The wavelengths λ1 and λ2 given within the specification are the wavelengths of the filter edge at the highest spectral point (maximum thickness of the wedge) and the lowest spectral point (minimum thickness of the wedge)
  • The data sheets illustrate typical transmission curves for unpolarized light with an AOI=0° at various wedge positions


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