Technology

FOSS produces two types of infrared instruments, one based on filter technology called IR (InfraRed) instruments, the other based on the interferometer technology called FTIR (Fourier Transform InfraRed) instruments.

Both types of instruments work in the mid-infrared region of the spectrum from 3 - 10 µm corresponding to 1000 – 5000 cm^-1. See figure "The electromagnetic spectrum ".

Interferometer-based FTIR instruments (ProcesScan™ FT)

The FTIR interferometer scans the full infrared spectrum, bringing new potential to milk analysis. The simultaneous collection of data from the entire spectrum allows measurement of new parameters even in complex dairy products. Analysis of an additional parameter simply becomes a matter of calibration.

The infrared beam hits the beam splitter, which sends half of the light to a fixed mirror and the other half to a moveable mirror. From the mirrors, the IR beams reflect and combine before they reach the detector. All of the IR frequencies travel through the interferometer at the same time, and rapid small movements of the mirror enables simultaneous generation of the entire IR spectrum. Figure shows the Interferometer.
The laser sends out light at only one wavelength, and is used to determine the actual wavelength based on the position of the mirror.

Standardisation

The fact that FTIR instruments are standardised offers a great advantage. A calibration developed on one instrument may be transferred to other instruments, which due to the standardisation will provide identical readings. Standardisation is achieved by comparing spectra of a specially developed FTIR equalizer sample, collected on a newly installed instrument (slave) to the spectra of a similar sample using a master instrument at FOSS.

First the frequencies axis is standardised by multiplying on all frequencies in the IR spectrum. Secondly the absorbency axis is standardised in a similar way.