The combination of IR spectroscopy with visible microscopy has been used in a wide range of analytical applications for more than 20 years. More recently, however, IR microspectroscopy has benefited from developments in IR detector arrays leading to a marked growth in FT-IR imaging technologies and applications. It is now a fairly simple task to obtain a high-quality IR spectrum from a sample region of around 20 mm in matter of seconds, and the ability to collect full IR images containing hundreds of thousands of pixels, where every image pixel contains a full range IR spectrum, is now available in many hundreds of laboratories worldwide. IR imaging hardware is not yet mature, but despite this, with today's state-of-the-art FT-IR imaging systems, the analysis time for many applications is limited not by the speed at which quality images are obtained, but by the data analysis or sample preparation techniques at the disposal of the operator.Progress in commercial FT-IR imaging hardware development comes from various drivers, but two are particularly relevant: (a) the high popularity of single point IR microscopy systems that has fuelled the interest in technology and applications utilizing more rapid methods of data acquisition and (b) the development of multichannel array detectors that operate in the mid-infrared region for nonspectroscopic applications. These are fundamental to both the understanding of current FT-IR imaging technologies and probable developments in the near future.
Developments in IR Microscopy and Imaging SystemsInterest in obtaining IR spectra from small samples goes back to over 60 years; for example, a reported study of the structure of penicillin by Thomson [1] in the late 1940s used a prismbased dispersive spectrometer coupled with a beam condenser/microscope system. A commercial IR microscope system described in 1953 by Coates et al. [2] demonstrated quite respectable IR spectra from single fiber samples of less than 20 mm in diameter, recorded with 15 min scan times, and contained some design attributes that are still present in today's systems. However, it was not until early 1980s when the rapid uptake of commercial FT-IR systems and applications such as semiconductor microanalysis provided both the applications and technology interest to spur the growth in IR microspectroscopy. Today, all major manufacturers of laboratory FT-IR spectrometers include IR microscopes, some with automated point mapping systems, as well as imaging systems in their product portfolios.Early (1980s) FT-IR microscope systems were mostly bolt-on accessories derived from optical microscope frames that were modified to support the collection of IR spectra from selected regions of interest (ROI). Later, systems were Raman, Infrared, and Near-Infrared Chemical Imaging Edited by Slobodan Š ašić and Yukihiro Ozaki