The design and implementation of a high-fidelity Raman imaging microscope.

Abstract

We describe a Raman imaging microscope that produces high-fidelity, large format Raman images and Raman spectra from samples as small as 1 micron in size. Laser illumination is delivered to the object by means of an infinity corrected microscope objective, either by a galvanometer scanning system or a widefield fibre optic. Wavelength selection of Raman scattered emission is achieved by an acousto-optic tunable filter (AOTF), which maintains image fidelity and provides either continuous or random wavelength selection. The collimated AOTF output is imaged first by a tube lens and then by a projection lens onto a cooled silicon CCD array. Instrument features, including factors that determine the system's spatial and spectral resolution, and design considerations are discussed in detail. Images and spectra of test objects and samples that demonstrate the capability of this imaging spectrometer are presented. The potential of intrinsic chemical imaging is discussed in terms of its use in the analyses of a variety of chemical and biological samples.