Linear variable optical filters can now be manufactured at a lower cost, making them more attractive to instrument designers and manufacturers
Barr Associates has recently made significant developments in the manufacture of infrared linear variable filters (LVF).
These advances have enabled the company to produce infrared LVFs at a significantly reduced cost, making their inclusion in detector systems more attractive to instrument designers and manufacturers.
Traditionally, optical gas analysis and optical sensor systems use singular optical detectors in conjunction with a variety of optical filters.
These filters are often held in a wheel assembly, as the wheel turns a different filter is positioned to intersect the beam path and the analysis made. These require a filter for each gas under investigation, a motor, and positioning sensors in addition to the associated support hardware and software.
Recent developments in detector arrays have brought about a revolution in the design of these instruments, however the difficulty has been in the filtering of light to the elements of these arrays.
This is usually done using costly diffraction gratings that require precision alignment and mounting.
The LVF offers a simpler and more cost-effective solution.
It can be bonded directly to the detector array reducing size and eliminating any alignment issues.
A single pixel in the detector array can be addressed behind the linear variable filter to identify specific wavelength.
If one or more pixels are addressed along the length of the detector array different gas species can be determined.
The number of applications where linear variable optical filters could replace existing hardware has yet to be fully realised.
Today optical filters are used in may types of instrumentation in a variety of applications ranging from spectrophotometers, colour correction systems, microscopy, florescence and Raman spectroscopy applications, most recently biotechnology instrumentation is becoming a bigger user of optical filters.
What is a linear variable optical filter? A linear variable filter is one where the centre wavelength of the filter changes linearly along its length.
That is to say at any point along its length could be a bandpass filter, or any other customer specified filter shape, as you move along it's length; the centre wavelength changes linearly but the band-shape and transmission remain.
