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Spectrometer configured to provide simultaneous multiple intensity spectra from independent light sources

  • US 6,184,985 B1
  • Filed: 12/11/1998
  • Issued: 02/06/2001
  • Est. Priority Date: 12/11/1998
  • Status: Expired due to Term
First Claim
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1. A compact spectrometer comprising:

  • first and second slits each generally arranged linearly along an axis in a plane of dispersion, and configured to simultaneously receive light reflected from respectively first and second portions of a film, the light having a plurality of diverse constituent wavelengths over a wavelength region of interest;

    a diffraction grating;

    at least one optical element for directing the reflected light from the first slit along an optical path to the diffraction grating, and for directing the reflected light from the second slit along an optical path to the diffraction grating, whereupon the light from the first slit impinges upon the grating and forms a first intensity spectrum in the place of dispersion, and the light from the second slit impinges upon the grating and forms a second intensity spectrum in the plane of dispersion;

    a detector;

    at least one optical element for directing the first intensity spectra along an optical path to a first portion of the detector, and the second intensity spectra along an optical path to a second portion of the detector, wherein the first and second intensity spectra at the detector are generally arranged side-by-side along an axis in the plane of dispersion and are substantially non-overlapping;

    whereupon the detector produces a plurality of first signals, one for each wavelength of interest within the first intensity spectrum, and a plurality of second signals, one for each wavelength of interest within the second intensity spectrum;

    a processor for estimating, responsive to the plurality of first signals, the thickness of the first portion of the film, and, responsive to the plurality of second signals, the thickness of the second portion of the film.

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