  Wide field Raman imaging using the integral field spectroscopy approach was
used as a fast, one shot imaging method for the simultaneous collection of all
spectra composing a Raman image. For the suppression of autofluorescence and
background signals such as room light, shifted excitation Raman difference
spectroscopy (SERDS) was applied to remove background artifacts in Raman
spectra. To reduce acquisition times in wide field SERDS imaging, we adapted
the nod and shuffle technique from astrophysics and implemented it into a wide
field SERDS imaging setup. In our adapted version, the nod corresponds to the
change in excitation wavelength, whereas the shuffle corresponds to the
shifting of charges up and down on a Charge-Coupled Device (CCD) chip
synchronous to the change in excitation wavelength. We coupled this improved
wide field SERDS imaging setup to diode lasers with 784.4/785.5 and 457.7/458.9
nm excitation and applied it to samples such as paracetamol and aspirin
tablets, polystyrene and polymethyl methacrylate beads, as well as pork meat
using multiple accumulations with acquisition times in the range of 50 to 200
ms. The results tackle two main challenges of SERDS imaging: gradual
photobleaching changes the autofluorescence background, and multiple readouts
of CCD detector prolong the acquisition time.
