Near-infrared Raman imaging microscope based on fiber-bundle image compression

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(NO3)2–K2SO4 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.