A relatively inexpensive micro-Raman system featuring confocal imaging, holographic optics, and CCD detection is described in detail. The construction of a confocal filter is discussed, along with the depth of field and spatial rejection expected. Limitations of the system such as low-frequency signal rejection by the holographic optics and wavelength calibration are also discussed. Spectra are shown giving examples of the capabilities of the system and the signal-to-noise ratio expected for typical liquid and solid samples.
Previous work has shown the potential of the Stokes/anti-Stokes intensity ratio from Raman spectroscopy for optically probing the temperature of materials. This paper uses the statistics of photon counting to set theoretical limits on the temperature accuracy of the technique, as well as developing an expression whereby the theoretical temperature uncertainty for any Raman band at a given temperature can be predicted. Comparison of the theory to experimental data is shown, and experimental limitations are discussed.
The sections in this article are
Introduction
The Technology and Rationale for Chemical Images
Sample‐Preparation Considerations for Chemical Mapping and Imaging
Chemical Mapping and Imaging Applications
Polymorph Analysis
Product Design and Development
Product Performance and Support
Chemical Image Production Using Chemometric Analysis
The Hyperspectral Cube and Chemical Images
Image Data Analysis
Data Preprocessing
Principal Component Analysis (
PCA
)
Ordinary Least Squares (
OLS
)
Partial Least Squares (
PLS
)
PLS
Quantitative Analysis
PLS
Classification
Analysis of Chemical Images
Conclusion
Acknowledgments
We present a straightforward procedure for frequency domain modeling of reradiation in a highly scattering medium with an arbitrary, finite three-dimensional geometry. We use a finite difference numerical solver to determine the fluence distribution at the excitation wavelength, which is then coupled to the emission wavelength with an array of equivalent reradiating sources. We then calculate the fluence distribution at the emission wavelength with a second, independent numerical simulation with new optical parameters appropriate to the emission wavelength, using the distributed reradiating sources as the excitation. We compare three-dimensional simulations of a fluorophore distributed in a scattering medium with experimental data. We also compare simulations of the Raman reradiation of small diamonds in a scattering medium with experiment.
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