Method and apparatus for reducing speckle in optical coherence tomography images

• US 20040100631A1
• Filed: 11/27/2002
• Published: 05/27/2004
• Est. Priority Date: 11/27/2002
• Status: Active Grant

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Bashkansky, Mark, Reintjes, John F.
• Granted Patent: US 6,847,449 B2
• Time in Patent Office: Days
• US Class Current: 356/342
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B

Abstract

A method and apparatus for reducing speckle due to MSL, without any loss of resolution, by averaging over different angles of the incident light at low input resolution, while collecting the backscattered light at a full resolution of a lens is described. The present invention allows discrimination against the speckle due to coherent MSL.

Claims

1. A method of improving quality of optical coherence tomography (OCT) images and detectability of sub-surface structures of a sample, comprising:

focusing incident light on the sample via a lens;

reducing speckle due to detected multiply scattered light (MSL) by performing an average of the detected MSL over different angles of incident light while maintaining a constant optical path length; and

collecting backscattered light from the sample at a full resolution of the lens along an output optical path which is different from optical path of the incident light.

2. The method as in claim 1, further comprising:

detecting the collected backscattered light.

3. The method as in claim 2, wherein the detected backscattered light collected at a full resolution of the lens is a high resolution output beam.

4. The method as in claim 1, further comprising:

disposing a prism in the optical path of the incident light; and

translating a prism along a hypotenuse thereof to vary the angle of incident light focused on the sample.

5. The method as in claim 1, further comprising:

disposing a mirror in the optical path of the incident light; and

causing a mirror to tilt in different directions to vary the angle of incident light focused on the sample.

6. The method as in claim 1, further comprising:

disposing a phase plate in the optical path of the incident light; and

rotating the phase plate between images to produce different MSL speckle for averaging.

7. The method as in claim 1, wherein the step of collecting the backscattered light is performed by disposing a beamsplitter in a path of the backscattered light from the sample.

8. The method as in claim 2, wherein collection of backscattered light along the output optical path allows discrimination against the speckle due to coherent MSL that reaches the detector within similar coherence length as light from a region of interest of the sample.

9. In an optical coherence tomography (OCT) system, a method of improving quality of OCT images and detectability of sub-surface structures of a sample, comprising:

focusing incident light on the sample;

reducing speckled noise due to detected multiply scattered light (MSL) by performing an average of the detected MSL over different angles of incident light; and

collecting backscattered light from the sample at a full resolution of a lens, focusing the incident light on the sample, along an output optical path which is different from optical path of the incident light.

10. The method as in claim 9, further comprising:

detecting the collected backscattered light.

11. The method as in claim 10, wherein the detected backscattered light collected at a full resolution of the lens is a high resolution output beam.

12. An apparatus for improving quality of optical coherence tomography (OCT) images and detectability of sub-surface structures of a sample, comprising:

means for focusing incident light on the sample;

means for reducing speckled noise due to detected multiply scattered light (MSL) by performing an average of the detected MSL over different angles of incident light while maintaining a constant optical path length; and

means for collecting backscattered light from the sample at a full resolution of the means focusing the incident light on the sample, wherein the backscattered light is collected along an output optical path which is different from optical path of the incident light.

13. The apparatus as in claim 12, further comprising:

means for detecting the collected backscattered light.

14. The apparatus as in claim 13, wherein the detected backscattered light collected at a full resolution of the lens is a high resolution output beam.

15. An apparatus for improving quality of optical coherence tomography (OCT) images and detectability of sub-surface structures of a sample, comprising:

a lens for focusing incident light on the sample;

a processor for reducing speckled noise due to detected multiply scattered light (MSL) by performing an average of the detected MSL over different angles of incident light while maintaining a constant optical path length; and

an optical device for collecting backscattered light from the sample at a full resolution of the lens along an output optical path which is different from optical path of the incident light.

16. The apparatus as in claim 15, further comprising:

a detector for detecting the collected backscattered light.

17. The apparatus as in claim 15, wherein the detected backscattered light collected at a full resolution of the lens is a high resolution output beam.

18. The apparatus as in claim 16, wherein the detector is a photodetector.

19. The apparatus as in claim 15, wherein the optical device is a beamsplitter.

20. The apparatus as in claim 15, wherein the different angles of incident light to performing averaging is obtained by translating a prism along its hypotenuse.

21. The apparatus as in claim 15, wherein the different angles of incident light to performing averaging is obtained by a combination of a tilting mirror and a lens.

22. The apparatus as in claim 15, wherein the different angles of incident light to performing averaging is obtained by a phase plate disposed in an optical path of the incident light.