A new technique for rapid Raman imaging and chemical analysis of micro-composites and biomaterials, with potential applications in real-time robotic vision, automated manufacturing, and medical imaging, is described and demonstrated. The key feature of this new instrument is a fiber-optic bundle used to compress two-dimensional images onto a one-dimensional fiber stack, which serves as the entrance slit of an imaging optical spectrograph. Thus a complete Raman spectrum is simultaneously collected from every point within a sample in a single scan of a charge-coupled-device (CCD) detector. The method is demonstrated by using Raman imaging of a microscopic mixed-salt sample. Its efficiency relative to alternative Raman imaging methods is quantitatively evaluated, and potential applications in other spectral imaging measurements are discussed. Index Headings: Raman spectroscopy; Spectral imaging; Chemical imaging; Fiber optics; Chemical sensor.
The design and performance of a near-infrared Raman imaging microscope (NIRIM) is described. This new instrument utilizes fiber-bundle image compression (FIC) to collect simultaneously a 3-D Raman spectral imaging data cube. Key NIRIM design features are discussed, including the FIC fiber-bundle, excitation laser, optical coupling to the microscope and fiber-bundle, holographic filtering, spectrograph imaging requirements, CCD parameters and chemical image processing. The theoretical collection efficiency and image quality of the NIRIM instrument are compared with those of tunable filter and line scanning Raman imaging methods. The performance of the NIRIM is demonstrated using a white light image of a bar-target and Raman chemical images of samples containing fructose-sucrose and Pb(NO 3 ) 2 -K 2 SO 4 microcrystalline mixtures. A Raman image collection time as fast as 1 s (total detector integration time) is demonstrated, for a 3-D data cube containing 322 image resolution elements and 900 Raman shift wavelengths.
Optical absorption and fluorescence spectral imaging is performed by using the recently developed fiber-bundle image compression (FIC) technique in which an entire spectral image is collected in a single scan of a charged-coupled device (CCD) detector. Absorption imaging is demonstrated by mapping the optical absorbance of a stained microscopic lily plant stem section. Fluorescence imaging is demonstrated by mapping shifts in the ruby R1 fluorescence line to determine the pressure distribution in a microcrystalline ruby powder squeezed between two diamond surfaces. The advantages and limitations of the FIC method, relative to tunable filter and line imaging techniques, are discussed.
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