Measurement device for non-invasively determining the concentration of polarising substances

• US 5,687,721 A
• Filed: 06/15/1995
• Issued: 11/18/1997
• Est. Priority Date: 12/15/1992
• Status: Expired due to Fees

• Current Assignee: Kuhls, Burkhard
• Original Assignee: Kuhls, Burkhard
• Inventors: Kuhls, Burkhard
• Primary Examiner(s): Bahr, Jennifer
• Assistant Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US08/464,657
• Time in Patent Office: 887 Days
• Field of Search: 128/633, 128/634, 128/664, 128/665, 356/364, 356/367, 356/368, 356/369
• US Class Current: 600/316
• CPC Class Codes: A61B 5/14558 by polarisation
• CPC Class Codes: G01N 21/21 Polarisation-affecting properties G01N21/19 takes precedence

Abstract

A device and method are disclosed for noninvasively measuring the concentration of sugar in the blood of a human subject. The method includes generating a beam of monochromatic light, confining the light beam to a predetermined optical path to impinge on a preselected portion of the body of the subject, polarizing the light beam, and performing both a static extinction measurement using the monochromatic light and a dynamic polarization measurement using the polarized light to obtain a measurement of the concentration of sugar in the blood in the preselected body portion. The dynamic polarization measurement is performed by analyzing the polarized light beam after impingement on the body portion while rotating the beam to produce a measurement signal indicative of the angle of polarization thereof, generating a reference signal indicative of influence of rotation of the beam on the angle of polarization thereof in the absence of blood in the optical path, and comparing the measurement signal and the reference signal to determine the angle of deflection of the light beam attributable to the presence of blood sugar in the optical path as a measure of the concentration of sugar in the blood flowing through the body portion.

Claims

1. A measurement device for noninvasively determining the concentration of polarizing substances in the human body, comprising:

a source of monochromatic light; and

means responsive to light from said source for performing both a static extinction measurement and a dynamic polarization measurement to obtain a measurement of the concentration of a predetermined polarizing substance in a selected member of the body;

said performing means including a detector responsive to light from said source to generate a static excitation measurement signal, a polarizer for receiving monochromatic light from the light source and polarizing the received light, an analyzer responsive to polarized light from the polarizer for producing a dynamic polarization measurement signal indicative of the angle of polarization thereof, at least one of said polarizer and said analyzer being rotatable, means for rotating at least one of the polarizer and analyzer, means for confining light from said polarizer to said analyzer to a distinct light path, means for positioning said selected body member containing said predetermined substance in said light path between the polarizer and the analyzer, angle sensor means for generating a reference signal indicative of influence of the rotating means on angle of polarization without influence of said body member being positioned between the polarizer and the analyzer, means responsive to the dynamic polarization measurement signal and the reference signal for determining the angle of deflection of the polarized signal, and means for determining the concentration from said static excitation measurement signal and said angle of deflection.

2. The measurement device according to claim 1, wherein said source of monochromatic light comprises a light-emitting semiconductor component.

3. The measurement device according to claim 1, wherein said source of monochromatic light comprises a light-emitting laser component.

4. The measurement device according to claim 1, wherein said means for confining light to a distinct path comprises an optical waveguide.

5. The measurement device according to claim 4, wherein said means for confining light to a distinct path comprises an optical waveguide between each of said polarizer and said analyzer and the positioning means for said body member.

6. The measurement device according to claim 1, wherein said analyzer includes a polarizing disk having a track for generating said reference signal.

7. The measurement device according to claim 6, wherein said track comprises a layer of material selected to be responsive to said means for rotating, to generate said reference signal according to whether said rotating means is electrical, mechanical, or magnetic.

8. The measurement device according to claim 1, further including means for shielding the polarizer and the analyzer from light sources other than said source of monochromatic light.

9. The measurement device according to claim 1, wherein said rotating means modulates polarized light impinging on said body member to produce a periodic polarization rotation of one of said analyzer and said polarizer.

10. The measurement device according to claim 1, wherein said means for positioning comprises a wristband.

11. The measurement device according to claim 1, wherein said means for positioning comprises a finger cuff.

12. The measurement device according to claim 1, further including means for suppressing interfering frequencies to enhance sensitivity of the device to said measurement signal.

13. A device-implemented method for noninvasively measuring the concentration of sugar in blood by a device adapted to be wearable by a human subject whose blood sugar is to be measured, said method comprising the steps of generating a beam of monochromatic light, confining the light beam to a predetermined optical path to impinge on a preselected portion of the body of the subject when said device is being worn, polarizing the light beam, and performing both a static extinction measurement using the monochromatic light and a dynamic polarization measurement using the polarized light to obtain a measurement of the concentration of sugar in the blood in said preselected body portion;

said step of performing a dynamic polarization measurement including analyzing the polarized light beam after impingement on said body portion while rotating the beam to produce a measurement signal indicative of the angle of polarization thereof, generating a reference signal indicative of influence of rotation of the beam on the angle of polarization thereof in the absence of blood in said optical path, and comparing the measurement signal and the reference signal to determine the angle of deflection of the light beam attributable to the presence of blood sugar in the optical path.

14. The method according to claim 13, wherein the step of confining the light beam to a preselected optical path includes directing the beam through an optical waveguide.

15. The method according to claim 13, wherein the step of rotating the light beam includes using one of an electrical, mechanical, or magnetic means of said device for the rotation.

16. The method according to claim 13, further including the step of shielding the light beam from contribution by other sources of light during generation and along said optical path thereof.

17. The method according to claim 13, further including the step of providing a receptacle in the optical path to enable positioning the preselected body portion therein.

18. The method according to claim 17, wherein said receptacle comprises one of an armband, a wristband, and a finger cuff.

19. The method according to claim 13, wherein the optical path directs the light beam through the preselected body portion to provide a transmission measurement.

20. The method according to claim 13, wherein the optical path directs the light beam obliquely on the preselected body portion for shallow reflection therefrom to provide a reflectance measurement.

21. The method according to claim 13, including:

a) determining the time derivative Δ

α

/Δ

t of the rotation of the polarization plane caused by the concentration of sugar in the blood,

b) determining the light intensity I at the end of the optical path and the time derivative Δ

I/Δ

t thereof, and

c) determining the concentration C of blood sugar as;

space="preserve" listing-type="equation">C=(A)(I) (Δ

α

/Δ

t)(Δ

I/Δ

t)!,

where A is a constant which is experimentally determined.