Liquid Crystal Tunable Filter Raman Chemical Imaging

Abstract

A Lyot-type liquid crystal tunable filter (LCTF) suitable for high-definition Raman chemical imaging has been developed. The LCTF has been incorporated into an efficient Raman imaging system that provides significant performance advantages relative to any previous approach to Raman microscopy. The LCTF and associated optical path is physically compact, which accommodates integration of the LCTF within an infinity-corrected optical microscope. The LCTF simultaneously provides diffraction-limited spatial resolution and 7.6-cm-1 spectral bandpass across the full free spectral range of the imaging spectrometer. The LCTF Raman microscope successfully integrates, in a facile manner, the utility of optical microscopy and the analytical capabilities of Raman spectroscopy. In this paper the LCTF Raman imaging system is described in detail, as well as results of initial studies of polymer and corrosion product model systems.

Localizing and Quantifying Carotenoids in Intact Cells and Tissues

“…Spatial resolution available with Raman microscopy is dependent on the wavelength of the excitation light and in theory is the same as other optical microscopies, such as luorescence (e.g., ∼250 nm lateral and ∼500 nm axial, for blue/green excitation). The addition of spatial resolution can be accomplished in several diferent ways: confocal point-scanning Raman microscopy [12,13], wide-ield Raman imaging [14], or Raman line scanning [15,16]. The relative advantages and disadvantages of each of these approaches have been reviewed elsewhere and will not be covered here [17].…”

Advanced Optical Imaging of Endocytosis

“…Though Raman spectral signatures are much weaker than fluorescence emission spectra, it is possible to perform Raman spectral imaging at the single cell level with modern detection technologies. Hyperspectral Raman microscopy can be implemented in a variety of formats similar to those described for hyperspectral fluorescence microscopy (Christensen & Morris, 1998;Govil, et al, 1993;Morris, et al, 1996), however the most commonly utilized for visualizing endocytosis in living cells has been the confocal pointscanning method, due to its availability, high sensitivity, optical sectioning capability, and speed.…”

Analysis of Stained Objects in Histological Sections by Spectral Imaging and Differential Absorption

“…The filter is based on the Lyot birefringent interferometer and provided continuous, random access wavelength selection from 400 to 720 nm with a stated wavelength-dependent bandwidth of 0.125 times the central wavelength (Morris et al 1994(Morris et al ,1996. Images collected over this wavelength range were free of distortion and wavelength-dependent translations or shifts.…”