A line of light reflected from the
sample enters the imaging optic (usually a microscope lens)
and is separated into its component wavelengths by diffraction
optics contained in the spectral encoder, which is usually
a spectrometer in point mapping systems and a
spectrograph in line mapping systems; a two-dimensional
image (spatial dimension · wavelength dimension) is then
formed on the detector. The sample is moved past the
objective lens on a motorised stage and point or line images
acquired at adjacent points on the object are stored on a
PC for further analysis. Charge Coupled Device (CCD)
detectors (sensitive between 400 and 1000 nm) are typically
used as detectors in Raman imaging, while Fourier Trans-form (FT) Raman imaging systems require more expensive
longer-wavelength focal-plane array (FPA) detectors [22].