CHEMICAL IMAGING WITH A CONFOCAL SCANNING FOURIER-TRANSFORM - RAMAN MICROSCOPE

Traditional approaches in confocal microscopy have focused on techniqu es to generate volumetric intensity or phase images of an object. In t hese different imaging modes the scattered optical-field properties de pend on local refractive index and absorption, properties not unique t o a given material. We report here on a confocal microscope that uses Raman scattered light to generate volumetric chemical images of a mate rial. We designed and built a prototype instrument, called a confocal scanning laser Raman microscope, that combines a confocal scanning las er microscope with a Fourier-transform-Raman spectrometer. The high de pth and lateral spatial resolution of the confocal optics design defin e a volume element from which the Raman scattered light is collected, and the spectrometer analyzes its spectral content. The sample is scan ned through the microscope probe volume, and a chemical image is gener ated based on the content of the Raman spectrum extracted from each sc an position in the sample. The results include instrument characteriza tion measurements and examples of confocal chemical imaging.