Mid-infrared hyperspectral imaging

The Raman microscope sold by Renishaw, Inc. may also be used in the imaging mode, by holding the monochromator at a certain wavelength for each time increment. However, the Renishaw instruments are mainly used in the Raman microscopy and mapping modes. 

The epi-illumination scheme preserves the linear polarization of the incident laser beam. Because the AOTF is polarization sensitive, a half-wave plate is used to rotate the plane of polarization by 180 in order to preserve the AOTF output. The collimated output from the AOTF was first imaged by a tube lens and then by a projection lens onto a liquid-nitrogen-cooled silicon CCD array. One or, occasionally, two holographic notch filters were placed in front of the detector to eliminate stray radiation from the Rayleigh line. These filters transmitted between 75% and 80% of the Raman emission beyond 75 cm of the Rayleigh line. 

To minimize data acquisition time, the overall magnification of this system was made as small as possible, consistent with the spatial resolution desired. Since the image is sampled by the discrete pixels of the CCD camera, the Nyquist sampling criterion must be obeyed to avoid the generation of artifacts. There is an explicit relationship describing how the number of counts per pixel depends on the optical design. We know from Equation (1.2) that the radius of the Airy disk r is equal to 0.61A/NA (since 2r). If the size of the CCD pixel is p, then the Nyquist sam- 

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In addition to pioneering the developments in FPA detectors designed specifically for fast mid-infrared hyperspectral imaging, Digilab redesigned their microscope to launch the first microscope designed specifically to cater for the unique requirements of FPA-based imaging. Such improvements included a wider and... 

Powerful instruments for mapping and hyperspectral imaging in the near-, mid-, and far-infrared regions and by Raman spectroscopy are now commercially... 

This is not to imply that molecular structure of simple organic molecules cannot be determined by infrared spectroscopy. In fact, the information that can be deduced from an infrared spectrum is complementary to that of other methods, and infrared spectroscopy provides valuable information that is unattainable by other methods, as is shown in the remainder of the book. More important, however, a plethora of other applications became available with the advent in 1969 of the first commercial mid-infrared Fourier transform spectrometer with better than 2cm resolution. These include quantitative analysis of complex mixtures, the investigation of dynamic systems, biological and biomedical spectroscopy, microspectroscopy and hyperspectral imaging, and the study of many types of interfacial phenomena. All of these applications (and many more) are described in this book. Furthermore, because of the development of such sampling techniques... 

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