Method and apparatus for multi-spectral analysis in noninvasive NIR spectroscopy
First Claim
1. An apparatus for determining the concentration of an analyte in a sample, comprising:
- (a) means for irradiating the sample with incident radiation containing a plurality of distinct, nonoverlapping spectral regions of wavelengths in the near-infrared spectrum;
(b) means for collecting reflected radiation emerging from the sample and directing said reflected radiation into first and second light paths, wherein the first light path comprises radiation from a first spectral region of wavelengths;
(c) first filter means disposed in the first light path, wherein the first filter means is capable of selectively passing radiation having substantially no correlation with the concentration of the analyte;
(d) first detection means for receiving selectively passed radiation emerging from the first filter means and for converting the same into a signal representative of the intensity of said radiation;
(e) adjustable filter means disposed in the second light path, wherein the adjustable filter means attenuates the intensity of radiation in the second light path;
(f) principal analyte filter means capable of receiving attenuated radiation emerging from the adjustable filter means, and selectively passing one or more independent wavelengths therefrom, wherein the one or more independent wavelengths are specifically correlated with the concentration of the analyte;
(g) second filter means capable of receiving the one or more independent wavelengths emerging from the principal analyte filter means and attenuating the intensity of each independent wavelength;
(h) second detection means for receiving the attenuated independent wavelengths emerging from the second filter means and converting the detected wavelengths into a signal representative of the intensity of said wavelengths; and
(i) means for converting the detected wavelengths into a signal representative of the intensity of said wavelengths.
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Abstract
An apparatus is provided for determining the concentration of an analyte present in a sample using multi-spectral analysis in the near-infrared (NIR) range. Incident radiation containing a plurality of distinct, nonoverlapping spectral regions of wavelengths in the near-infrared range is used to irradiate the sample. Diffusively reflected radiation emerging from the sample is detected, and a value indicative of the concentration of the analyte is obtained therefrom, preferably using an application of chemometrics techniques. Information obtained from each of the nonoverlapping spectral regions of wavelengths can be cross-correlated to remove background interference.
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Citations
35 Claims
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1. An apparatus for determining the concentration of an analyte in a sample, comprising:
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(a) means for irradiating the sample with incident radiation containing a plurality of distinct, nonoverlapping spectral regions of wavelengths in the near-infrared spectrum; (b) means for collecting reflected radiation emerging from the sample and directing said reflected radiation into first and second light paths, wherein the first light path comprises radiation from a first spectral region of wavelengths; (c) first filter means disposed in the first light path, wherein the first filter means is capable of selectively passing radiation having substantially no correlation with the concentration of the analyte; (d) first detection means for receiving selectively passed radiation emerging from the first filter means and for converting the same into a signal representative of the intensity of said radiation; (e) adjustable filter means disposed in the second light path, wherein the adjustable filter means attenuates the intensity of radiation in the second light path; (f) principal analyte filter means capable of receiving attenuated radiation emerging from the adjustable filter means, and selectively passing one or more independent wavelengths therefrom, wherein the one or more independent wavelengths are specifically correlated with the concentration of the analyte; (g) second filter means capable of receiving the one or more independent wavelengths emerging from the principal analyte filter means and attenuating the intensity of each independent wavelength; (h) second detection means for receiving the attenuated independent wavelengths emerging from the second filter means and converting the detected wavelengths into a signal representative of the intensity of said wavelengths; and (i) means for converting the detected wavelengths into a signal representative of the intensity of said wavelengths. - View Dependent Claims (2, 3, 4, 5, 6, 16, 17, 18)
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7. An apparatus for determining the concentration of an analyte in a sample, comprising:
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(a) a source capable of emitting radiation containing a plurality of distinct, nonoverlapping spectral regions in the near-infrared spectrum; (b) means for dividing radiation emitted by the source of part (a) into first and second beam paths; (c) means for irradiating the sample with the radiation in the first beam path, thereby providing reflected radiationl; (d) means for collecting the reflected radiation emerging from the sample and directing said reflected radiation into a reflected light path; (e) a first optical transfer cell disposed in the reflected light path, said first cell comprising first positive correlation filter means having absorption characteristics adapted to accept the reflected radiation and emphasize one or more wavelengths from the reflected radiation, wherein said one or more wavelengths have high correlation with the concentration of the analyte in the sample; (f) means for receiving the one or more emphasized wavelengths from the first optical transfer cell and for converting the same into signals representative of the intensity of said emphasized wavelengths; (g) a second optical transfer cell disposed in the second beam path, said second cell comprising neutral density filter means having absorption characteristics sufficient to attenuate the intensity of the radiation from the second beam path equally over a selected range of near-infrared wavelengths; (h) means for receiving attenuated radiation from the second optical transfer cell and for converting the same into signals representative of the intensity thereof; and (i) means for calculating the concentration of the analyte in the sample using the signals generated by means (f) and (h). - View Dependent Claims (8, 9, 10)
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11. An apparatus for determining the concentration of an analyte in a sample, comprising:
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(a) a source capable of emitting radiation containing a plurality of distinct, nonoverlapping spectral regions of wavelength in the near-infrared spectrum; (b) a means for dividing radiation emitted by the source into first and second beam paths; (c) means for irradiating the sample with the radiation in the first beam path, thereby providing reflected radiation; (d) means for collecting the reflected radiation emerging from the sample and directing said reflected radiation into a reflected light path; (e) a first optical transfer cell disposed in the reflected light path, said first cell comprising first positive correlation filter means having absorption characteristics adapted to accept the reflected radiation and emphasize one or more wavelengths from the reflected radiation, wherein said one or more wavelengths have high correlation with the concentration of the analyte in the sample; (f) means for receiving the one or more emphasized wavelengths from the first optical transfer cell and for converting the same into signals representative of the intensity of said emphasized wavelengths; (g) a second optical transfer cell disposed in the second beam path, said second cell comprising a second positive correlation filter means having absorption characteristics identical to those of the first positive correlation filter means; (h) means for receiving attenuated radiation from the second optical transfer cell and for converting the same into signals representative of the intensity thereof; and (i) means for calculating the concentration of the analyte in the sample using the signals generated by means (f) and (h). - View Dependent Claims (12)
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- 13. The apparatus of 12, wherein the absorption characteristics of at least one layer from the first and second positive correlation filter means are established using weighting factors.
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19. A method for determining the concentration of an analyte in a sample, comprising the steps of:
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(a) irradiating the sample with incident radiation containing a plurality of distinct, nonoverlapping spectral regions of wavelengths in the near-infrared spectrum; (b) directing the resulting reflected radiation emerging into first and second light paths, wherein the first light path comprises radiation from a first spectral region of wavelengths; (c) filtering said reflected radiation in the first light path with a first filter means capable of selectively passing radiation having substantially no correlation with the concentration of the analyte; (d) detecting the selectively passed radiation in step (c) and converting said radiation into a signal representative of the intensity of said radiation; (e) filtering said reflected radiation in the second light path with an adjustable filter means disposed therein and effective to attenuate the intensity of radiation in the second light path; (f) receiving said attenuated radiation provided in step (e) with a principal analyte filter means capable of selectively passing one or more independent wavelengths emerging from the adjustable filter means, wherein the one or more independent wavelengths are specifically correlated with the concentration of the analyte; (g) filtering said one or more independent wavelengths passed through the principal analyte filter means in step (f) using a second filter means capable of attenuating the intensity of each independent wavelength; (h) detecting the attenuated radiation passed by the second filter means in step (g) and converting the detected radiation into a signal representative of the intensity of said radiation; and (i) calculating the concentration of the analyte in the sample using the signals generated by steps (d) and (h). - View Dependent Claims (20, 21, 22, 23, 24, 33, 34, 35)
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25. A method for determining the concentration of an analyte in a sample, comprising:
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(a) generating radiation containing a plurality of distinct, nonoverlapping spectral regions in the near-infrared spectrum, and dividing the radiation into a first beam path and a second beam path; (b) directing the first beam path into the sample, thereby giving rise to reflected radiation therefrom; (c) directing said reflected radiation into a reflected light path having a first optical transfer cell disposed therein, said first cell comprising first positive correlation filter means having absorption characteristics adapted to accept the reflected radiation and emphasize one or more wavelengths therein, said one or more wavelengths having high correlation with the concentration of the analyte in the sample; (d) converting the one or more emphasized wavelengths into signals representative of the intensity of thereof; (e) directing the second beam path into a second optical transfer cell comprising neutral density filter means having absorption characteristics sufficient to attenuate the intensity of the radiation from the second beam path equally over a selected range of near-infrared wavelengths; (f) converting the attenuated radiation from the second optical transfer cell into signals representative of the intensity thereof; and (g) calculating the concentration of the analyte in the sample using the signals generated by means (d) and (f). - View Dependent Claims (26, 27, 28, 29, 30, 31)
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32. A method for determining the concentration of an analyte in a sample, comprising:
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(a) generating radiation containing a plurality of distinct, nonoverlapping spectral regions in the near-infrared spectrum, and dividing the radiation into a first beam path and a second beam path; (b) directing the first beam path into the sample, thereby giving rise to reflected radiation therefrom; (c) directing said reflected radiation into a reflected light path having a first optical transfer cell disposed therein, said first cell comprising first positive correlation filter means having absorption characteristics adapted to accept the reflected radiation and emphasize one or more wavelengths therein, said one or more wavelengths having high correlation with the concentration of the analyte in the sample; (d) converting the one or more emphasized wavelengths into signals representative of the intensity of thereof; (e) directing the second beam path into a second optical transfer cell comprising a second positive correlation filter means having absorption characteristics identical to those of the first positive correlation filter means; (f) converting the attenuated radiation from the second optical transfer cell into signals representative of the intensity thereof; and (g) calculating the concentration of the analyte in the sample using the signals generated by means (d) and (f).
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Specification