9 December 1999 Dedicated monolithic infrared spectrometer for process monitoring
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Abstract
Foster-Miller has leveraged its innovations in IR fiber- optic probes and the recent development of a miniature spectrometer to build a novel IR sensor system for process applications. The developed sensor systems is a low-cost alternative to process FTIR and filter based systems. A monolithic wedge-grating optic provides the spectral dispersion with low cost thermopile point or array detectors picking off the diffracted wavelengths from the optic. The integrated optic provides spectral discrimination between 3- 12 micrometers with resolution at 8 cm-1 or better and high overall optical throughput. The device has a fixed cylindrical grating uniquely bonded to the edge of a ZnSe conditioning 'wedge'. The conditioning optic overcomes limitations of concave gratings as it accepts high angle light at the narrow end of the wedge and progressively conditions it to be near normal to the grating. On return, the diffracted wavelengths are concentrated on the discrete or array detector elements by the wedge, providing throughput comparable to that of an FTIR. The miniature spectrometer coupled to flow through liquid cells or multipass gas cells provides significant cost advantage over conventional sampling methodologies. Currently, we are investigating process applications for the petroleum and dairy markets. The sensor system eliminates the cost, complexity, reliability and bandwidth/resolution problems associated with either Fabry Perot or Michelson Interferometer based approaches for low-cost process applications.
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Suneet Chadha, Suneet Chadha, William Kyle, William Kyle, Roy A. Bolduc, Roy A. Bolduc, Lawrence E. Curtiss, Lawrence E. Curtiss, } "Dedicated monolithic infrared spectrometer for process monitoring", Proc. SPIE 3859, Optical Online Industrial Process Monitoring, (9 December 1999); doi: 10.1117/12.372940; https://doi.org/10.1117/12.372940
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