Apparatuses and methods of ocular surface interferometry (OSI) employing polarization and subtraction for imaging, processing, and/or displaying an ocular tear film

• US 8,915,592 B2
• Filed: 04/25/2013
• Issued: 12/23/2014
• Est. Priority Date: 04/01/2009
• Status: Active Grant

• Current Assignee: TearScience Inc. (Johnson & Johnson)
• Original Assignee: TearScience Inc. (Johnson & Johnson)
• Inventors: Korb, Donald R., Weber, William L., Chinnock, Randal B., Gravely, Benjamin T., Grenon, Stephen M.
• Primary Examiner(s): PINKNEY, DAWAYNE
• Application Number:
  US13/870,054
• Publication Number:
  US 20130308095A1
• Time in Patent Office: 607 Days
• Field of Search: 351/206, 351/200, 351/205, 351209-210, 351221-223, 351245-246, 351/212, 351/208, 351/160.R, 351/159, 351/247, 600/356, 600/346, 600/476, 600/425
• US Class Current: 351/206
• CPC Class Codes: A61B 3/0025 characterised by electronic signal processing, e.g. eye models
• CPC Class Codes: A61B 3/101 for examining the tear film
• CPC Class Codes: G01B 11/0675 using interferometry
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/20224 Image subtraction
• CPC Class Codes: G06T 2207/30041 Eye; Retina; Ophthalmic
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: G06T 7/0012 Biomedical image inspection

Abstract

Apparatuses and methods employing ocular surface interferometry (OSI) employing polarization and subtraction for imaging, processing, and/or displaying an ocular tear film are disclosed. The apparatuses and methods can be employed for measuring tear film layer thickness (TFLT) of the ocular tear film, which includes lipid layer thickness (LLT) and/or aqueous layer thickness (ALT). An imaging device is focused on the lipid layer of the tear film to capture optical wave interference interactions of specularly reflected light from the tear film combined with a background signal(s) in a first image. The imaging device is focused on the lipid layer of the tear film to capture a second image containing background signal(s) in the first image. The second image can be subtracted from the first image to reduce and/or eliminate background signal(s) in the first image to produce a resulting image that can be analyzed to measure tear film layer thickness (TFLT).

Claims

1. An apparatus for imaging an ocular tear film, comprising:

a control system configured to;

(a) receive at least one first image containing optical wave interference of specularly reflected light in a first polarization plane along with a background signal from a region of interest (ROI) of an ocular tear film captured by an imaging device while illuminated by a multi-wavelength light source;

(b) receive at least one second image containing only the background signal in a second polarization plane perpendicular or substantially perpendicular to the first polarization plane from the ROI of the ocular tear film captured by an imaging device;

(c) subtract the at least one second image from the at least one first image to generate at least one resulting image containing the optical wave interference of specularly reflected light from the ROI of the ocular tear film with the background signal removed or reduced.

2. The apparatus of claim 1, further comprising an imaging device configured to capture the at least one first image and capture the at least one second image.

3. The apparatus of claim 2, further comprising a polarizer disposed in an imaging path of the imaging device,

wherein the polarizer has a center axis and is selectively rotatable about the center axis to provide a first polarization axis relative to the first polarization plane of the specularly reflected light from the ROI of the ocular tear film during a capture of the at least one first image, and

wherein the polarizer is selectively rotatable to provide a second polarization axis that is perpendicular or substantially perpendicular relative to the first polarization axis during the capture of the at least one second image.

4. The apparatus of claim 2, further comprising a rotatable wheel having a first polarizer and second polarizer, the rotatable wheel selectively rotatable such that the first polarizer is disposed in an imaging path of the imaging device during the capture of the at least one first image, and wherein the second polarizer is alternately disposed in the imaging path of the imaging device during the capture of the at least one second image.

5. The apparatus of claim 4, wherein the first polarizer has a first polarization axis that is parallel or substantially parallel to the first polarization plane of the specularly reflected light from the ROI of the ocular tear film to pass or substantially pass the specularly reflected light to the imaging device while reducing the background signal.

6. The apparatus of claim 4, wherein the second polarizer has a second polarization axis that is perpendicular or substantially perpendicular to the second polarization plane of the specularly reflected light from the ROI of the ocular tear film to reduce or eliminate the specularly reflected light while passing a portion of the background signal to the imaging device.

7. The apparatus of claim 4, wherein the first polarizer has a first polarization axis that is parallel or substantially parallel to the polarization plane of the specularly reflected light from the ROI of the ocular tear film to pass or substantially pass the specularly reflected light to the imaging device while reducing the background signal, and

wherein the second polarizer has a second polarization axis that is perpendicular or substantially perpendicular to the polarization plane of the specularly reflected light from the ROI of the ocular tear film to eliminate or substantially eliminate the specularly reflected light while passing a portion of background signal to the imaging device.

8. The apparatus of claim 2, further comprising:

a first polarizer selectively disposable in an imaging path of the imaging device during a capture of the at least one first image; and

a second polarizer selectively disposable in the imaging path of the imaging device during the capture of the at least one second image.

9. The apparatus of claim 8, wherein the first polarizer has a first polarization axis that is parallel or substantially parallel to the first polarization plane of the specularly reflected light from the ROI of the ocular tear film to pass or substantially pass the specularly reflected light to the imaging device while reducing the background signal before the background signal reaches the imaging device.

10. The apparatus of claim 8, wherein the second polarizer has a second polarization axis that is perpendicular or substantially perpendicular to the second polarization plane of the specularly reflected light from the ROI of the ocular tear film to reduce or eliminate the specularly reflected light before the specularly reflected light reaches the imaging device while passing a portion of the background signal.

11. The apparatus of claim 8, further comprising:

a first polarizer selectively disposed in the imaging path of the imaging device,

wherein the first polarizer has a polarization axis that is parallel or substantially parallel to the first polarization plane of the specularly reflected light from the ROI of the ocular tear film to pass or substantially pass the specularly reflected light to the imaging device while reducing the background signal before the background signal reaches the imaging device; and

a second polarizer alternately disposed in the imaging path of the imaging device,

wherein the second polarizer has a polarization axis that is perpendicular or substantially perpendicular to the second polarization plane of the specularly reflected light from the ROI of the ocular tear film to reduce or eliminate the specularly reflected light while passing a portion of background signal to the imaging device.

12. The apparatus of claim 8, wherein the first polarizer and the second polarizer are alternately translatable into the imaging path of the imaging device.

13. The apparatus of claim 8, wherein the first polarizer and the second polarizer are alternately rotatable into the imaging path of the imaging device.

14. The apparatus of claim 1, further comprising a first imaging device configured to capture the at least one first image, and a second imaging device configured to capture the at least one second image.

15. The apparatus of claim 14, further comprising a non-polarizing beam splitter configured to direct a first portion of the specularly reflected light including the background signal to the first imaging device while simultaneously directing a second portion of the specularly reflected light including the background signal to the second imaging device.

16. The apparatus of claim 15, further comprising a first polarizer disposed in an imaging path of the first imaging device during a capture of the at least one first image.

17. The apparatus of claim 16, wherein the first polarizer has a first polarization axis parallel or substantially parallel to the first polarization plane of the specularly reflected light directed to the imaging device from the ROI of the ocular tear film to pass or substantially pass the specularly reflected light to the first imaging device while reducing the background signal before the background signal reaches the first imaging device.

18. The apparatus of claim 15, further comprising a second polarizer disposed in an imaging path of the second imaging device during a capture of the at least one second image.

19. The apparatus of claim 18, wherein the second polarizer has a second polarization axis perpendicular or substantially perpendicular to the second polarization plane of the specularly reflected light from the ROI of the ocular tear film to reduce or eliminate the specularly reflected light before the specularly reflected light reaches the second imaging device while passing a portion of the background signal to the second imaging device.

20. The apparatus of claim 15, further comprising:

a first polarizer disposed in an imaging path of the first imaging device,

wherein the first polarizer has a first polarization axis that is parallel or substantially parallel to the first polarization plane of the specularly reflected light from the ROI of the ocular tear film to pass or substantially pass the specularly reflected light to the first imaging device while reducing the background signal; and

a second polarizer disposed in the imaging path of the second imaging device,

wherein the second polarizer has a second polarization axis that is perpendicular or substantially perpendicular to the polarization plane of the specularly reflected light from the ROI of the ocular tear film to reduce or eliminate the specularly reflected light while passing a portion of background signal to the second imaging device.

21. The apparatus of claim 14, further comprising a polarizing beam splitter configured to direct a portion of the specularly reflected light and the background signal to the first imaging device while simultaneously directing the background signal to the second imaging device reducing or eliminating the specularly reflected light.

22. The apparatus of claim 1, further comprising a polarizer disposed in an illumination path of the multi-wavelength light source and configured to polarize light emitted from the multi-wavelength light source illuminating the ROI of the ocular tear film.

23. The apparatus of claim 22, wherein the polarizer is a circular polarizer.

24. The apparatus of claim 1, wherein the background signal includes at least one of stray light and ambient light.

25. The apparatus of claim 1, wherein the imaging device is configured to capture the at least one second image when the multi-wavelength light source is illuminating the ROI of the ocular tear film.

26. The apparatus of claim 25, wherein the background signal includes diffusely reflected light resulting from illumination of the ocular tear film.

27. The apparatus of claim 26, wherein the background signal includes diffusely reflected light from an iris of an eye.

28. The apparatus of claim 1, wherein the control system is further configured to sequentially control an imaging device to capture the optical wave interference of specularly reflected light and the background signal in the at least one first image to provide a plurality of first images, and capture the background signal in the at least one second image to provide a plurality of second images interleaved with the plurality of first images to provide a plurality of first and second image pairs.

29. The apparatus of claim 28, wherein the control system is configured to subtract the at least one second images from the plurality of first and second image pairs from the corresponding at least one first images from the plurality of first and second image pairs to generate a plurality of resulting images each containing the optical wave interference of specularly reflected light from the ROI of the ocular tear film with the background signal removed or reduced.

30. The apparatus of claim 1, wherein the multi-wavelength light source is comprised of a multi-wavelength Lambertian light source configured to uniformly or substantially uniformly illuminate the ROI of the ocular tear film.

31. The apparatus of claim 1, wherein the control system is further configured to display at least one of the at least one first image, the at least one second image, or the at least one resulting image on a visual display.

32. A method of imaging an ocular tear film, comprising:

illuminating a region of interest (ROI) of an ocular tear film with a multi-wavelength light source;

capturing optical wave interference of specularly reflected light in a first polarization plane including a background signal from the ROI of the ocular tear film while illuminated by the multi-wavelength light source in at least one first image by an imaging device;

capturing only the background signal in a second polarizing plane perpendicular or substantially perpendicular to the first polarization plane from the ROI of the ocular tear film in at least one second image by an imaging device; and

subtracting the at least one second image from the at least one first image to generate at least one resulting image containing the optical wave interference of specularly reflected light from the ROI of the ocular tear film with the background signal removed or reduced.