IR provides the structural information of the fibre. A typical IR microscope is all-reflecting, with visible illumination for visual examination of the sample and with a dedicated on-axis small area mercury-cadmium telluride (MCT) detector. The sampling size can vary from less than 50 × 50 μm in linear dimensions to the dimensions of the detector element. The sample is placed on a standard microscope X–Y stage and can be visually examined under a variety of magnifications. The sample area of interest is isolated by placing a variable aperture on an intermediate image of the sample within the barrel of the microscope.
Recently, IR micro-spectroscopy has been used to develop two-dimensional functional group images of polymer samples. A two-dimensional computer-restored step-scan was performed on the sample in order to obtain a compositional map. A 250 × 250 μm aperture was used in 250-μm steps in the x and y directions with the aid of a computer-controlled moving stage.
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