Spectrometers Based on Two-Dimensional Array Detectors

A short time later, Levin s group modified step-scan FT-IR spectrometer to operate with a mid-IR MCT FPA detector. Unlike most MCT detectors used in FT-IR spectrometers, which operate in the photoconductive (PC) mode, the pixels of MCT FPA detectors operate in the photovoltaic (PV) mode. As noted in Section 1.2.2, the cut-off wavenumber of narrow-band PC MCT detectors is about 750 cm . The PV detector elements used in MCT FPA detectors have the same high sensitivity as narrow-band PC MCT detectors, but the cut-off wavenumber is higher, at about 850 cm . 

Rad sold the company to a group of private investors, who renamed the company Digilab LLC. The group sold Digilab to Varian in 

During each of these manifestations, this organization made many of the innovations that have led to the remarkable popularity of FT-IR spectroscopy today. In this chapter, the name of the company will be given as it was when the work was reported. 

Another major Hmitation arose from the need to employ a step-scan interferometer. This necessity arose from the relatively slow read-out rates of these first-generation FPAs, which were of the order of only a few hundred Hertz. The read-out rate (or frame rate) of a FPA detector determines the type of interferometer that must be used for FT-IR imaging, as the FPA cannot be triggered (for data transfer) any faster than its maximum read-out (frame rate) speed. As the first-generation FPAs were only capable of frame rates in the hundreds of Hz, and rapid-scanning interferometers required a faster frame rate, the use of step-scan 

Generally speaking, the larger the array, the slower the read-out frame rates of the FPA. The frame rates of today s second-generation FPAs range from several kHz for the smaller 16 x 16 and 32 x 32 FPAs, to just over 1 kHz for the largest 

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