Ostec 4434-801-59962935-08, Руководство по эксплуатации, Страница: 7 / 33

3
Spectrometer operating principles and exterior
Operating principles
In terms of its operating principles, spectrometer IROS 05 is classified as a modulation
spectrometric device. Instead of using optical dispersing elements (prisms, diffraction
gratings, etc.) to split the radiation into spectral components, devices of this class use an
optical moving element to modulate the radiation flow and then perform electro-
mathematical processing of the signal from the optical detector that records this modulated
radiation as an interferogram.
The modulator in spectrometer IROS 05 is a double beam misalignment resistant
scanning interferometer Double Cat’s Eye (Russian Patent No. 1552791 dd 1993). See the
spectrometer optical scheme in Fig.1.
Figure 1. Spectrometer optical scheme
The inlet optical system (2) converts the IR source (1) radiant energy into a convergent
annular beam and makes it focus on the inlet port of the interferometer (3) consisting on
spherical mirrors and a moving beam splitter.
The beam splitter is a zinc selenide plate with a special coating that partially transmits
and partially reflects incident light. After a series of reflections, each beam falls on the beam
splitter again. The beams interfere, return to the mirrors, which this time act as a converging
optical system, and leave the interferometer through the mirror center ports.
The mirror system (4) converts the light escaping from the interferometer into a parallel
beam that passes through the cell holder (5) and is focused on the photodetector (7) by the
parabolic mirror (6).
Each monochromatic spectral component of amplitude B
i
and wavenumber
σ
i
at the
interferometer inlet has a corresponding photodetector signal: