Non-Invasive Polarimetric Apparatus and Method for Analyte Sensing in Birefringent Media

• US 20100234704A1
• Filed: 11/07/2008
• Published: 09/16/2010
• Est. Priority Date: 11/07/2007
• Status: Active Grant

• Current Assignee: University of Toledo
• Original Assignee: University of Toledo
• Inventors: Cameron, Brent D.
• Granted Patent: US 8,718,734 B2
• Time in Patent Office: Days
• US Class Current: 600/319
• CPC Class Codes: A61B 5/00 Measuring for diagnostic purposes radiation diagnosis A61B6/00; diagnosis by ultrasonic, sonic or infrasonic waves A61B8/00; Identification of persons
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/14555 specially adapted for the eye fundus
• CPC Class Codes: A61B 5/14558 by polarisation
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: G01N 21/21 Polarisation-affecting properties G01N21/19 takes precedence
• CPC Class Codes: G01N 21/23 Bi-refringence

Abstract

A noninvasive polarimetric apparatus used to measure levels of a substance in a sample in the presence of dynamically changing sample birefringence is provided. A polarization system generates multiple states of polarized light which interact with the sample. An analyzer system receives a signal from the sample and generates a secondary signal. This signal is detected and then processed to measure levels of a substance in a sample that may be have time varying birefringent components.

Claims

1. A noninvasive polarimetric apparatus used to measure levels of a substance in a sample, in which the sample may exhibit dynamically changing birefringence comprising:

a polarization system configured to generate multiple states of polarized light which interact with a given sample; and

,

an analyzer system configured to receive the resulting signal and generate a secondary signal which can be further processed to measure levels of a substance in the sample.

2. The apparatus of claim 1, wherein one or more of the polarization system and the analyzer system are configured to generate an oscillating birefringence.

3. The apparatus of claim 1, wherein one or more of the polarization system and the analyzer system comprise a variable retarder.

4. The apparatus of claim 1, wherein one or more of the polarization system and the analyzer system comprise one or more variable retardance modulator systems.

5. The apparatus of claim 1, wherein the polarization system comprises a first variable retarder modulator, a second variable retarder modulator, and a third variable retarder modulator, and the analyzer system comprises a fourth variable retarder modulator, a fifth variable retarder modulator, and a sixth variable retarder modulator.

6. The apparatus of claim 1, wherein the polarization system comprises:

a first variable retarder modulator having its fast axis oriented at an angle of −

45°

with respect to an initial vertical linear polarizer,

a second variable retarder modulator having its fast axis oriented at 45°

with respect to the vertical position, and

a third variable retarder modulator having its fast axis oriented at an angle of 0°

with respect to the vertical position; and

,

wherein the analyzer system comprises;

a fourth variable retarder modulator having its fast axis oriented at an angle of 0°

with respect to a vertical position,

a fifth variable retarder modulator having its fast axis oriented at 45°

with respect to the vertical position, and

a sixth variable retarder modulator having its fast axis oriented at an angle of −

45°

with respect to the vertical position, and

a horizontal linear polarizer.

7. The apparatus of claim 1, wherein the polarization system comprises:

a first variable retarder modulator having its fast axis oriented at a 1^st angle with respect to an initial linear polarizer,

a second variable retarder modulator having its fast axis oriented at a 2^nd angle with respect to the first modulator, and

a third variable retarder modulator having its fast axis oriented at a 3^rd angle with respect to the second modulator, and,

wherein the analyzer system comprises;

a fourth variable retarder modulator having its fast axis oriented at 4^th angle with respect to the vertical position,

a fifth variable retarder modulator having its fast axis oriented at a 5^th angle with respect to the fourth modulator, and

a sixth variable retarder modulator having its fast axis oriented at a 6^th angle with respect to the fifth modulator, and

a linear polarizer.

8. The apparatus of claim 1, wherein the light generated has peak retardation that corresponds to a quarter of the wavelength of the light being used.

10. The apparatus of claim 1, wherein the frequency of polarization modulation is at the modulator frequency (ω

₁).

11. The apparatus of claim 1, wherein the magnitude and direction of the induced birefringence determines the polarization state of the light exiting the polarization apparatus.

12. The apparatus of claim 1, wherein the polarization system is configured to continuously change the retardance of the polarized light, thus producing continuously changing polarization states.

14. The apparatus of claim 1, wherein the polarimetric apparatus is configured to apply a partial least square (PLS) analysis to the signal.

15. The apparatus of claim 1, wherein the analyzer system is configured to generate a secondary signal that provides predictive information about the sample.

16. The apparatus of claim 1, wherein the analyzer system is configured to receive the signal from the sample in an at least partially transmissive mode.

17. The apparatus of claim 1, wherein the analyzer system is configured to receive the signal from the sample in an at least partially reflectance mode.

18. The apparatus of claim 1, wherein the analyzer system is configured to receive the signal from the sample in an at least partially absorptive mode.

19. The apparatus of claim 1, wherein the substance in the sample is an optically active substance.

20. The apparatus of claim 1, wherein the substance in the sample causes a refractive index to be measured in the substance.

21. The apparatus of claim 1, wherein the substance in the sample causes absorption data to be measured in the substance.

22. The apparatus of claim 1, wherein the sample comprises a birefringent medium.

23. The apparatus of claim 1, wherein the sample is substantially transparent.

24. The apparatus of claim 1, wherein the sample is substantially translucent.

25. The apparatus of claim 1, wherein the sample is substantially reflective.

26. The apparatus of claim 1, wherein the sample is substantially opaque.

27. The apparatus of claim 1, wherein the sample is substantially adjacent to at least one birefringent material.

28. The apparatus of claim 1, wherein the sample is substantially positioned between birefringent materials.

29. The apparatus of claim 1, wherein the sample is a patient'"'"'s eye or other associated tissue.

30. The apparatus of claim 1, wherein the sample is aqueous humor of a patient'"'"'s eye.

31. The apparatus of claim 1, wherein the sample is tissue from a skin area of a patient.

32. The apparatus of claim 1, wherein the sample is tissue from a thin-skin area of a patient.

33. The apparatus of claim 1, wherein the sample is tissue from a patient'"'"'s ear, nose or thin skin between fingers or toes.

34. The apparatus of claim 1, wherein the sample comprises a thin film material.

35. The apparatus of claim 1, wherein the sample comprises a gaseous, liquid or solid material.

36. The apparatus of claim 1, wherein the sample comprises one or more or of soil, air, and water.

37. The apparatus of claim 1, wherein the substance in the sample comprises glucose in an animal'"'"'s eye.

38. The apparatus of claim 1, wherein the substance in the sample comprises a cancer cell in an animal.

39. The apparatus of claim 1, wherein the substance in the sample comprises a cancer cell in an animal'"'"'s skin.

40. The apparatus of claim 1, wherein the substance in the sample comprises a protein or a fragment thereof.

9. A polarimeter according to, wherein the polarized light oscillates between left and right circularly polarized light, with elliptically polarized light between the left and right circularly polarized light.

13. A noninvasive polarimetric apparatus used to measure levels of a substance in a sample, which may be birefringent in nature, dynamically changing sample birefringence comprising:

at least one light source,

at least one vertical polarizer,

a polarization system configured to generate multiple states of polarized light which interact with a given sample, and

an analyzer system configured to receive a signal obtained by the sample and generate a secondary signal which may be processed to measure levels of a substance in a sample, and

at least one horizontal polarizer.

41. A noninvasive method for measuring levels of a substance in a sample in the presence of dynamically changing birefringence comprising:

generating states of polarized light wherein phase delays are introduced in the polarized light,

at least partially interacting with the sample with the generated polarized light signal(s), and

receiving a signal obtained by the sample and generating a secondary signal through an analyzer system.

42. A non-invasive in vivo method for sensing a concentration of an optically active substance in an animal'"'"'s eye wherein the method comprises the steps of:

generating states of polarized light wherein phase delays are introduced in the polarized light,

at least partially interacting with the sample with the generated polarized light, receiving a signal obtained by the sample and generating a secondary signal through an analyzer system.