Method and apparatus for measuring motion of a subject using a series of partial images from an imaging system

• US 7,805,009 B2
• Filed: 03/24/2006
• Issued: 09/28/2010
• Est. Priority Date: 04/06/2005
• Status: Active Grant

• Current Assignee: Carl Zeiss Meditec Incorporated (Carl-Zeiss-Stiftung)
• Original Assignee: Carl Zeiss Meditec Incorporated (Carl-Zeiss-Stiftung)
• Inventors: O'Hara, Keith E., Hacker, Martin, Meyer, Scott A., Everett, Matthew J., Flachenecker, Claus, Williams, Rick A.
• Primary Examiner(s): Mariam; Daniel G
• Application Number:
  US11/389,351
• Publication Number:
  US 20060228011A1
• Time in Patent Office: 1,649 Days
• Field of Search: 382/128, 382131-132, 382/181, 382/209, 382/218, 382/151, 382/309
• US Class Current: 382/218
• CPC Class Codes: A61B 3/102 for optical coherence tomography [OCT]
• CPC Class Codes: A61B 3/113 for determining or recording eye movement

Abstract

A line scan imager is used to determine the motion of a subject. Each line of image data from the line scan imager is compared with a reference image. The location of a matching line in the reference image reveals the displacement of the subject. The current subject displacement can be determined based on each line of image data. The resulting displacement information can be used to correctly place other optical beams on the subject. The method can be applied to tracking the human eye to facilitate measurement, imaging, or treatment with a beam of optical radiation.

Claims

1. A method of monitoring the movement of an eye of a patient in order to facilitate the alignment of a beam of radiation with respect to the eye, said beam being generated by a light source and directed to the eye via a scanner, said method comprising the steps of:

generating a two dimensional reference image of the eye;

scanning a line of imaging light across the eye and collecting reflected image data to generate a second two dimensional image;

during a scanning step, comparing a portion of the second image to the reference image to identify a substantially matching image portion, wherein the comparison step is performed by selecting portions of the reference image which have scan coordinates that are displaced in the plane of the image relative to the selected portion of the second image;

determining a displacement between the scan coordinates associated with the matched image portions, said displacement corresponding to the motion of the eye; and

correcting the alignment of the beam of radiation with respect to the eye using the scanner based on the determined displacement.

2. A method as recited in claim 1, wherein the beam of radiation is used to measure the eye.

3. A method as recited in claim 2, wherein the measurement beam is part of an optical coherence tomography system.

4. A method as recited in claim 1, wherein the beam of radiation is used to treat the eye.

5. A method as recited in claim 1, wherein the portion of the second image selected during the comparison step corresponds substantially to a line scan.

6. A method as recited in claim 1, wherein the portion of the second image selected during the comparison step corresponds substantially to less than a line scan.

7. A method as recited in claim 1, wherein the portion of the second image selected during the comparison step corresponds to a plurality of line scans.

8. A method as recited in claim 1, wherein the second two dimensional image is generated by scanning a spot across the eye in a raster pattern.

9. A method as recited in claim 1, wherein the comparison step includes the computation of the cross-correlation between the selected portion of the second image and selected portions of the reference image.

10. A method as recited in claim 9, wherein the match corresponds to the portion of the reference image which yields the largest computed cross-correlation with respect to the selected portion of the second image.

11. A method as recited in claim 9, further including the step of computing the centroid of the computed cross-correlation values and wherein the match corresponds to the portion of the reference image associated with the computed centroid.

12. A method as recited in claim 1, wherein the comparison step is performed by selecting portions of the reference image which have scan coordinates that are displaced and rotated in the plane of the image relative to the selected portion of the second image.

13. A method as recited in claim 1, wherein portions of the reference image which are selected for the comparison step are chosen based in part on previous estimates of eye motion.

14. A method as recited in claim 1, wherein said comparing step and said determining step are repeated for different portions of the second scanned image and wherein the motion of the eye is determined by an analysis of a plurality of determined displacements.

15. A method as recited in claim 14, wherein said analysis includes fitting a curve through the plurality of determined displacements, said curve representing motion of the eye over time.

16. A method as recited in claim 15, wherein the curve fitting step uses information on the uncertainty of the eye motion derived from the determined displacements.

17. A method as recited in claim 1, wherein the step of generating a second two dimensional image is performed by scanning selected regions of the eye that include more detail than other regions.

18. A method as recited in claim 1, wherein the second two dimensional image scan is created using a line-scan ophthalmoscope.

19. A method as recited in claim 1, wherein the second two dimensional image scan is created using a spot-scanning confocal imager.

20. A method of monitoring the movement of an eye of a patient in order to calibrate the position of a beam of measurement radiation on the eye, comprising the steps of:

generating a two dimensional reference image of the eye;

scanning imaging light across the eye and collecting the reflected light to produce image data corresponding to a second two dimensional image;

simultaneously scanning the measurement beam of radiation across the eye;

recording data associated with the measurement beam in a way that maintains the association between measurement data and image data acquired at substantially the same time;

comparing a portion of the second image to the reference image to identify a substantially matching image portion;

determining a displacement between the scan coordinates associated with the matched portions, said displacement corresponding to the motion of the eye, said comparing and determining steps being performed with a plurality of different image portions selected from different locations within the second two dimensional image;

correcting the scan coordinates associated with the measurement data acquired substantially simultaneously with the portion of image data, the correction being based on a combination of the determined displacements;

generating a corrected measurement data set using the corrected scan coordinates with the recorded measurement data; and

storing the corrected measurement data set.

21. A method as recited in claim 20, wherein the measurement beam is part of an optical coherence tomography system.

22. A method as recited in claim 20, wherein the step of repeatedly scanning the imaging light across the eye is performed by a line-scan ophthalmoscope.

23. A method of monitoring the movement of an eye of a patient in order to facilitate the alignment of a beam of radiation with respect to the eye, said beam being generated by a light source and directed to the eye via a scanner, said method comprising the steps of:

generating a two dimensional reference image of the eye;

scanning imaging light across the eye and collecting reflected image data to generate a second two dimensional image;

during a scanning step, comparing a portion of the second image to the reference image to identify a substantially matching image portion, wherein the comparison step includes the computation of the cross-correlation between the selected portion of the second image and selected portions of the reference image;

determining a displacement between the scan coordinates associated with the matched image portions, said displacement corresponding to the motion of the eye;

correcting the alignment of the beam of radiation with respect to the eye using the scanner based on the determined displacement; and

further including the step of computing the centroid of the computed cross-correlation values and wherein the match corresponds to the portion of the reference image associated with the computed centroid.

24. A method of monitoring the movement of an eye of a patient in order to facilitate the alignment of a beam of radiation with respect to the eye, said beam being generated by a light source and directed to the eye via a scanner, said method comprising the steps of:

generating a two dimensional reference image of the eye;

scanning imaging light across the eye and collecting reflected image data to generate a second two dimensional image;

during a scanning step, comparing a portion of the second image to the reference image to identify a substantially matching image portion, wherein the comparison step is performed by selecting portions of the reference image which have scan coordinates that are displaced and rotated in the plane of the image relative to the selected portion of the second image;

determining a displacement between the scan coordinates associated with the matched image portions, said displacement corresponding to the motion of the eye; and

correcting the alignment of the beam of radiation with respect to the eye using the scanner based on the determined displacement.

25. A method of monitoring the movement of an eye of a patient in order to facilitate the alignment of a beam of radiation with respect to the eye, said beam being generated by a light source and directed to the eye via a scanner, said method comprising the steps of:

generating a two dimensional reference image of the eye;

scanning imaging light across the eye and collecting reflected image data to generate a second two dimensional image;

during a scanning step, comparing a portion of the second image to the reference image to identify a substantially matching image portion, wherein portions of the reference image which are selected for the comparison step are chosen based in part on previous estimates of eye motion;

determining a displacement between the scan coordinates associated with the matched image portions, said displacement corresponding to the motion of the eye; and

correcting the alignment of the beam of radiation with respect to the eye using the scanner based on the determined displacement.

26. A method of monitoring the movement of an eye of a patient in order to facilitate the alignment of a beam of radiation with respect to the eye, said beam being generated by a light source and directed to the eye via a scanner, said method comprising the steps of:

generating a two dimensional reference image of the eye;

scanning imaging light across the eye and collecting reflected image data to generate a second two dimensional image;

during a scanning step, comparing a portion of the second image to the reference image to identify a substantially matching image portion;

determining a displacement between the scan coordinates associated with the matched image portions, said displacement corresponding to the motion of the eye;

correcting the alignment of the beam of radiation with respect to the eye using the scanner based on the determined displacement and wherein said comparing step and said determining step are repeated for different portions of the second scanned image and wherein the motion of the eye is determined by an analysis of a plurality of determined displacements.

27. A method as recited in claim 26, wherein said analysis includes fitting a curve through the plurality of determined displacements, said curve representing motion of the eye over time.

28. A method as recited in claim 27, wherein the curve fitting step uses information on the uncertainty of the eye motion derived from the determined displacements.