 Raman microscope

A Raman microscope combines an optical microscope with Raman spectroscopy to measure a spectrum from a localized specimen region. A microscope objective focuses a laser and collects scattered light; rejection filters suppress the intense excitation line, and a spectrometer separates the remaining wavelengths for detection. A facility instrument at the National University of Singapore supports both single-point measurements and Raman mapping.^[ref]

In a common backscattering arrangement, the same objective supplies excitation and collection. Moving the specimen or focus associates each Raman spectrum with a position, so a chosen spectral band can map chemical or structural variation. Confocal microscopy can additionally reject some out-of-focus light; a small map step by itself does not establish correspondingly fine spatial resolution.

For an original wavelength calculation, illuminate at ${\lambda }_0=532\mathrm{nm}$ and observe a Stokes Raman shift of $1000\mathrm{c}{\mathrm{m}}^{-1}$. The scattered wavelength satisfiesBoth reciprocal wavelengths must use the same length unit. The spectrometer measures the shifted light, while a filter suppresses the much brighter Rayleigh scattering near $532\mathrm{nm}$. Spectral resolution determines how nearby spectral features separate; objective focusing and the detection geometry determine spatial discrimination.

A concrete coupled apparatus placed a hydrated mouse bone in a mechanical tester mounted on a Raman microprobe stage. It followed mineral-band changes during elastic loading, connecting local molecular response with specimen mechanics.^[ref] Interpreting such a measurement requires the specimen position, loading conditions and laser exposure to be controlled. Local heating, fluorescence and instrumental response can change a recorded spectrum; focused illumination is not automatically non-destructive.