System and method for creating a stable optical interface

• US 20070219437A1
• Filed: 03/17/2006
• Published: 09/20/2007
• Est. Priority Date: 03/17/2006
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: GlucoLight Corporation
• Inventors: Shakespeare, Walter, Schurman, Matthew, Bennett, William, Wallace, Phillip, Apple, Howard
• Granted Patent: US 8,219,172 B2
• Time in Patent Office: Days
• US Class Current: 600/316
• CPC Class Codes: A61B 2562/146 for optical coupling
• CPC Class Codes: A61B 5/0066 Optical coherence imaging
• 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 5/6832 using adhesives A61B5/259 takes precedence
• CPC Class Codes: A61B 5/6833 Adhesive patches

Abstract

A system and a method for creating a stable and reproducible interface of an optical sensor system for measuring blood glucose levels in biological tissue include a dual wedge prism sensor attached to a disposable optic that comprises a focusing lens and an optical window. The disposable optic adheres to the skin to allow a patient to take multiple readings or scans at the same location. The disposable optic includes a Petzval surface placed flush against the skin to maintain the focal point of the optical beam on the surface of the skin. Additionally, the integrity of the sensor signal is maximized by varying the rotation rates of the dual wedge prisms over time in relation to the depth scan rate of the sensor. Optimally, a medium may be injected between the disposable and the skin to match the respective refractive indices and optimize the signal collection of the sensor.

Claims

1. A system for creating a stable and reproducible optical interface in an optical sensor system for measuring blood glucose levels in biological tissue comprises:

an optical interferometer sensor utilizing a beam of light;

an interferometer connected to the optical sensor;

a computer connected to an optical receiver associated with the interferometer; and

a disposable optical lens apparatus connected to the optical sensor, wherein the disposable apparatus comprises;

a focusing lens; and

an optical window connected to the focusing lens;

wherein the disposable apparatus is attachable to a surface area of biological tissue by an adhesive.

2. The system of claim 1, wherein the optical sensor utilizes at least one rotating wedge prism to deviate an angle of the beam of light from an optical axis of the system.

3. The system of claim 1, wherein the optical sensor utilizes at least one oscillating angled mirror to deviate an angle of the beam of light from an optical axis of the system.

4. The system of claim 1, wherein the optical window includes a Petzval surface to interface with the surface area of the biological tissue.

5. The system of claim 4, wherein the Petzval surface is in the shape of a dome.

6. The system of claim 1, wherein the optical window is in the shape of a pedestal.

7. A method of using an optical system with an optical interferometer sensor and a disposable optical apparatus for measuring blood glucose levels in biological tissue comprises the steps of:

attaching the disposable apparatus to a surface area of biological tissue using an adhesive;

coupling the optical sensor to the disposable apparatus; and

taking a blood glucose reading using the optical sensor.

8. The method of claim 7, further comprising the steps of:

removing the optical sensor from the disposable apparatus; and

leaving the disposable apparatus on the surface area of biological tissue for later use.

9. The method of claim 7, further comprising the step of placing an index matching medium between the disposable apparatus and the surface area of the biological tissue.

10. A method for resolving variations in an optical path length of an optical sensor system having at least one wedge prism for measuring blood glucose levels in biological tissue comprises the following steps:

taking a plurality of scans using the optical sensor system;

locating a first peak in a first scan of the plurality of scans;

locating a first peak in each subsequent scan of the plurality of scans;

normalizing each first peak in each subsequent scan against the first peak in the first scan; and

averaging the normalized scans to produce a resulting averaged scan.

11. The method of claim 10, further comprising the step of using a peak locating algorithm to locate each first peak.

12. A method for resolving variations in an optical path length of an optical sensor system having at least one wedge prism for measuring blood glucose levels in biological tissue comprises the following steps:

determining a threshold trigger; and

setting the optical sensor system to begin acquiring data once the threshold trigger is reached.

13. The method of claim 12, further comprising the step of setting the threshold trigger to a signal intensity value of at least 10 decibels below a first peak intensity value associated with a signal produced by the optical sensor system, wherein the first peak intensity value corresponds to an optical interface between the optical sensor system and the biological tissue.

14. The method of claim 13, further comprising the step of setting the peak threshold trigger to a signal intensity value above a highest noise peak associated with the signal.

15. The method of claim 12, wherein the step of determining further comprises setting the threshold trigger to a signal intensity value that relates to a specific structural feature.

16. The method of claim 15, wherein the specific feature corresponds to an optical interface between the optical sensor system and the biological tissue.

17. The method of claim 12, further comprising the step of setting an angular velocity of at least one wedge prism to a value such that a lateral position of a beam of light utilized by the optical sensor system on the biological tissue moves a distance that is less than a value equal to a diameter of the beam of light multiplied by a factor of ten, during a single depth scan.

18. A method for minimizing distortion of a depth scale of an optical sensor system having at least one wedge prism for measuring blood glucose levels in biological tissue comprises the step of setting an angular velocity of at least one wedge prism to a value such that a lateral position of a beam of light utilized by the optical sensor system on the biological tissue moves a distance that is less than a value equal to a diameter of the beam of light multiplied by a factor of ten, during a single depth scan.

19. A method for stabilizing a scan pattern of an optical sensor system having at least one wedge prism for measuring blood glucose levels in biological tissue comprises the step of setting an angular velocity of the at least one wedge prism to a non-integral value of a depth scan rate associated with the optical sensor system.

20. The method of claim 19, further comprising the step of varying the angular velocity of the at least one wedge prism while the optical sensor system is in use.

21. The method of claim 19, further comprising the step of varying the angular velocity of the at least one wedge prism with respect to a second angular velocity associated with a second wedge prism during a total time of use of the optical sensor system, wherein the angular velocity is a non-integral value of the second angular velocity.

22. A method for stabilizing a scan pattern of an optical sensor system having a plurality of wedge prisms for measuring blood glucose levels in biological tissue comprises the steps of:

setting a first angular velocity associated with a first wedge prism to a harmonic integral of a second angular velocity associated with a second wedge prism, wherein the first angular velocity is at least one order of magnitude greater than the first angular velocity; and

setting the first angular velocity and the second angular velocity to non-harmonic integrals of a depth scan rate associated with the optical sensor system.

23. A method for optimizing an amount of light entering and exiting an area of biological tissue, wherein the amount of light is associated with an optical sensor system placed on the area of biological tissue in order to measure blood glucose levels, comprising the steps of:

coupling a Petzval surface to a bottom surface of the optical sensor system;

placing the optical sensor system on the surface area of biological tissue, such that the tissue wraps around the Petzval surface;

directing a beam of light through a focusing lens and the optical window, into the Petzval surface; and

maintaining a focal point of the beam of light at an interface of the Petzval surface and the area of biological tissue.

24. The method of claim 23, further comprising the step of injecting an index matching medium into the interface of the Petzval surface and the area of biological tissue, wherein the medium automatically matches a refractive index of the area of biological tissue with a refractive index of the Petzval surface.