Molecular Spectroscopy Workbench: Raman Images from Raman Maps - Spatial Resolution, Mapping Speed, and Multivariate Techniques for Constructing the Image

摘要

At the end of my second column, in which I discussed the development of Raman imaging, I said that my next column would discuss the physical determinants of spatial resolution as well as developing methods to improve the mapping speeds. I know that I got sidetracked, but I have not forgotten what I promised, so this column will address these issues. The spatial resolution of any imaging tool is determined by diffraction theory. In an optical microscope, it is assumed that a microscope objective is illuminated uniformly by light and the focal area is described by the Airy disk as (omega)_(o) velence 1.22 (lambda/NA) where NA stands for the numerical aperture of the objective. When the same objective is used to focus a laser beam, the beam profile is not uniform (it is very often Gaussian), nor does it fill the objective aperture. However, the minimum beam spot is described by a similar expression: (omega)_(o) velence K (lambda/NA) with the constant K not very different from 1.