Method and apparatus for the non-invasive measurement of blood glucose levels in humans
First Claim
1. A method for determining a diagnostic glucose level for a person, the method comprising:
- reflecting light off an ocular lens at a Brewster'"'"'s angle to produce an initial linear polarization of reflected light;
measuring a polarization rotation of the reflected light after exiting the eye, the polarization rotation being measured with respect to the initial linear polarization; and
determining a glucose concentration based on the measured polarization rotation.
1 Assignment
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Accused Products
Abstract
An apparatus (10) for determining a diagnostic glucose level in a human subject includes a light source (30) that produces collimated light at a selected wavelength. The collimated light is arranged such that it passes through a portion of an eye (12) of the subject and reflects off an eye lens (16) at a selected angle (θB) as reflected light. A polarization analyzer (70) measures a polarization of the reflected light that exits the eye (12). A path length processor (68) determines an optical path length (Lλ) of the reflected light within an aqueous humor (22) of the eye (12). A glucose level processor (90) computes a glucose concentration based on the measured polarization and the determined optical path length (Lλ).
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Citations
21 Claims
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1. A method for determining a diagnostic glucose level for a person, the method comprising:
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reflecting light off an ocular lens at a Brewster'"'"'s angle to produce an initial linear polarization of reflected light;
measuring a polarization rotation of the reflected light after exiting the eye, the polarization rotation being measured with respect to the initial linear polarization; and
determining a glucose concentration based on the measured polarization rotation. - View Dependent Claims (2, 3, 4, 5, 6)
adjusting a light source incident angle to maximize a signal-to-noise ratio.
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3. The method as set forth in claim 1, wherein the reflecting step includes:
reflecting circularly polarized light off the ocular lens at the Brewster'"'"'s angle of an aqueous humor/lens interface.
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4. The method as set forth in claim 1, wherein the measuring step includes:
interferometrically measuring an optical path length through an ocular aqueous humor, the measured optical path length being used in the determining of a glucose concentration.
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5. The method as set forth in claim 1, wherein the measuring step includes:
determining a major axis of an elliptical polarization of the reflected light after exiting the eye, the polarization rotation corresponding to a rotation of major axis.
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6. The method as set forth in claim 1, wherein the steps of reflecting light and measuring a polarization rotation are repeated for a plurality of wavelengths, and the step of determining the glucose level based on the measured polarization rotation includes:
determining levels for a plurality of optically active substances including glucose in the aqueous humor based on the measured polarization rotations at the plurality of wavelengths.
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7. A method for determining a diagnostic glucose level, the method comprising:
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reflecting light from an internal ocular interface at an incident angle that has a selected reflection polarization characteristic;
measuring an elliptical polarization of the reflected light; and
computing a glucose concentration based on a polarimetric rotation parameter derived from the measured elliptical polarization of the reflected light and the selected reflection polarization characteristic. - View Dependent Claims (8, 9, 10, 11, 12)
measuring a polarization of the reflected light;
correcting the measured polarization for refractive polarization changes occurring at selected ocular interfaces; and
determining a polarization rotation computed based on the corrected measured polarization and the selected reflection polarization characteristic.
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12. The method as set forth in claim 7, further including:
adjusting a plane of incidence of the reflecting from the internal ocular interface to minimize an ellipticity produced by an ocular birefringence.
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13. A method for determining a diagnostic glucose level, the method comprising:
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reflecting light from a lens/vitreous humor interface at a critical angle for total reflection at the lens/vitreous humor interface;
measuring a polarimetric parameter of the reflected light; and
computing a glucose concentration based on the polarimetric parameter.
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14. A method for determining at least a diagnostic glucose level, the method comprising:
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reflecting light from an internal ocular interface at an incident angle that has a selected reflection polarization characteristic;
measuring a polarimetric parameter of the reflected light;
repeating the reflecting and measuring steps for light at a plurality of wavelengths to obtain a plurality of polarimetric parameters;
computing polarization rotation values at each of the plurality of wavelengths; and
determining compositions of a plurality of optically active substances including glucose based on the plurality of polarization rotation values.
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15. An apparatus for determining a diagnostic glucose level in a human subject, the apparatus comprising:
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a light source that produces collimated light at a selected wavelength, the collimated light arranged such that the collimated light passes through a portion of an eye of the subject and reflects off an eye lens at a selected angle as reflected light;
a polarization analyzer that measures a polarization of the reflected light that exits the eye;
a path length processor that determines an optical path length of the reflected light within an aqueous humor of the eye; and
a glucose level processor that computes a glucose concentration based on the measured polarization and the determined optical path length. - View Dependent Claims (16, 17, 18, 19, 20, 21)
a white light source with one or more filter elements that spectrally filter light produced by the white light source, an arc discharge lamp, one or more light emitting diodes, and a multiple-wavelength laser.
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18. The apparatus as set forth in claim 15, further including:
a polarizer that polarizes light produced by the light source prior to entering the eye.
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19. The apparatus as set forth in claim 15, wherein the path length processor includes:
an interferometric detector that measures a difference in optical path length between the collimated light after reflection from the eye lens and a reference beam derived from the light source.
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20. The apparatus as set forth in claim 15, further including:
a head mount that fastens to a head of the subject and supports at least the polarization analyzer and the path length detector.
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21. The apparatus as set forth in claim 15, further including:
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a substrate on which the collimated light, the polarization analyzer, and the path length detector are arranged;
an actuator that operates on the substrate to adjust a substrate orientation with respect to the eye; and
a feedback circuit incorporating an output of the polarization analyzer, the feedback circuit driving the actuator to arrange the substrate at a selected substrate orientation that minimizes an ocular birefringence.
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Specification