Two-Dimensional Raman Imaging

Several methods for constructing a two-dimensional Raman image from point or line spectra have already been described, and several examples are presented here. A wide variety of reconstruction methods have been reported and the examples below are certainly not comprehensive. In particular, those techniques available in commercial instruments are emphasized. Furthermore, the case of image reconstruction from an Jc-by-y array of single-point spectra is conceptually trivial and is not presented here. 

In this case, a particularly sensitive spectrometer and an intensified CCD were used, so the images were obtained quite rapidly (8 sec to 2 min). 

Both optical and mechanical line scans generate large data sets when used to construct a two-dimensional Raman image, but computer power and storage is inexpensive in the post-PC world. An advantage of such large data sets is the retention of complete spectra for each spatial element, with often high spectral 

Hadamard transform spectroscopy existed long before Raman imaging, as a form of multiplex spectroscopy. A Hadamard mask is an array of clear and 

Single point spectra of prostate biopsy specimen 

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The addition of a second spatial dimension to the line imaging experiment yields the technique most commonly referred to simply as Raman imaging (1,2). Although several approaches to the problem are available commercially, they share a common objective of providing Raman intensities as a function of Av, x, y, and sometimes depth (z). To illustrate an example of two-dimensional Raman imaging. Figure 11.17 shows both a Raman image... 

With a special optical system at the sample chamber, combined with an imagir system at the detector end, it is possible to construct two-dimensional images of the sample displayed in the emission of a selected Raman line. By imaging from their characteristic Raman lines, it is possible to map individual phases in the multiphase sample however, Raman images, unlike SEM and electron microprobe images, have not proved sufficiently useful to justify the substantial cost of imaging optical systems. 

Fig. 12.15. Pseudocolor-scaled, three-dimensional macular pigment resonance Raman images of two volunteer subjects, along with related line plot profiles, derived for each distribution along nasal-temporal (solid line) and inferior-superior meridians (dashed line), both running through the center of the macula. Distribution...

Thus far, we have reviewed basic theories and experimental techniques of Raman spectroscopy. In this chapter we shall discuss the principles, experimental design and typical applications of Raman spectroscopy that require special treatments. These include high pressure Raman spectroscopy, Raman microscopy, surface-enhanced Raman spectroscopy, Raman spectroelectro-chemistry, time-resolved Raman spectroscopy, matrix-isolation Raman spectroscopy, two-dimensional correlation Raman spectroscopy, Raman imaging spectrometry and non-linear Raman spectroscopy. The applications of Raman spectroscopy discussed in this chapter are brief in nature and are shown to illustrate the various techniques. Later chapters are devoted to a more extensive discussion of Raman applications to indicate the breadth and usefulness of the Raman technique. 

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