Raman Microspectroscopy:  A Comparison of Point, Line, and Wide-Field Imaging Methodologies

Three different Raman microspectroscopic imaging methodologies using a single experimental configuration are compared; namely, point and line mapping, as representatives of serial imaging approaches, and direct or wide-field Raman imaging employing liquid-crystalline tunable filters are surveyed. Raman imaging data acquired with equivalent low-power 514.5-nm laser excitation and a cooled CCD camera are analyzed with respect to acquisition times, image quality, spatial resolution, intensity profiles along spatial coordinates, and spectral signal-to-noise ratios (SNRs). Point and line mapping techniques provide similar SNRs and reconstructed Raman images at spatial resolutions of ∼1.1 μm. In contrast, higher spatial resolution is obtained by direct, global imaging (∼313 nm), allowing subtle morphological features on test samples to be resolved.