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Raman spectroscopy apparatus and method for continuous chemical analysis of fluid streams

  • US 5,751,415 A
  • Filed: 05/13/1996
  • Issued: 05/12/1998
  • Est. Priority Date: 05/13/1996
  • Status: Expired due to Fees
First Claim
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1. A method for continuously analyzing the composition of a fluid stream using Raman spectroscopy comprising the steps of:

  • (a) introducing the fluid stream into a tubular Raman enhancement cell comprising;

    a fluid stream inlet and a fluid stream outlet located adjacent the ends of the enhancement cell for continuous fluid flow through the enhancement cell;

    an optical connector located at one end of the enhancement cell for connecting a bundle of optical fibers to the enhancement cell, wherein said bundle of optical fibers includes at least one excitation optical fiber and one or more collection optical fibers; and

    a transparent fluid barrier located between the bundle of optical fibers and the enhancement cell;

    (b) introducing light having an excitation wavelength into the Raman enhancement cell through the excitation optical fiber;

    (c) collecting backscattered Raman light from the enhancement cell with the one or more collection optical fibers;

    (d) measuring the backscattered light with a Raman spectrometer comprising;

    a linear array of the one or more collection optical fibers for generating an optical signal of the scattered light from the enhancement cell;

    a filter for rejecting portions of the optical signal having the excitation wavelength;

    a volume holographic transmission grating to disperse the light;

    a transmissive aberration correction element for correcting optical aberrations introduced into optical signal by the volume holographic transmission grating, said aberration correction element comprising at least one optically transparent wedge or prism; and

    a charge coupled device array for converting the optical signal into a corresponding electronic signal; and

    (e) converting the electronic signal into a representation of the chemical analysis of the fluid stream.

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