Near-infrared spectrometers optical-filter spectrometer

A typical IR spectrometer consists of the following components radiation source, sampling area, monochromator (in a dispersive instrument), an interference filter or interferometer (in a non-dispersive instrument), a detector, and a recorder or data-handling system. The instrumentation requirements for the mid-infrared, the far-infrared, and the near-infrared regions are different. Most commercial dispersive infrared spectrometers are designed to operate in the mid-infrared region (4000-400 cm ). An FTIR spectrometer with proper radiation sources and detectors can cover the entire IR region. In this section, the types of radiation sources, optical systems, and detectors used in the IR spectrometer are discussed. 

For economic recycling of plastics, various types of polymeric materials have to be separated in a short period of time. The near-infrared spectral range allows the monitoring of structural or molecular properties of the plastic under investigation. The spectrometer system described is based on optical fibres for absorption and reflexion measurements, an acousto-optic tunable filter and a transputer system. It is able to detect 1,000 spectra/ s and to identify 20 pieces/second. 10 refs. 

The basic parts of Raman spectrometer are (i) excitation source, a laser beam, (ii) sample illumination system (usually an intense, polarized and coherent laser beam in the UV, visible, or near-infrared range) and light collection optics (collected with a lens and is sent through interference filter or spectrophotometer), (iii) wave length selector i.e. filter spectrophotometer and (iv) detector system. 

For Raman microscopy, the most common spectrometer system consists of a visible laser coupled to a polychromator and a CCD detector, although near-infrared Fourier transform spectrometers cffe also used. The CCD detector can be used in a variation of Raman microscopy known as Raman imaging a special optical filter allows only one Stokes fine to reach the two-dimensional detector, which then contains a map of the distribution of the intensity of that line in the illuminated area. 

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