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 approximately 1.1 microm. In contrast, higher spatial resolution is obtained by direct, global imaging (approximately 313 nm), allowing subtle morphological features on test samples to be resolved.