Ophthalmic instrument with adaptive optic subsystem that measures aberrations (including higher order aberrations) of a human eye and that provides a view of compensation of such aberrations to the human eye

• US 20030071969A1
• Filed: 08/31/2001
• Published: 04/17/2003
• Est. Priority Date: 08/31/2001
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: AOA Xinetics (Northrop Grumman Corporation)
• Inventors: Knowles, C. Harry, Wirth, Allan, Levine, Bruce M.
• Granted Patent: US 6,709,108 B2
• Time in Patent Office: Days
• US Class Current: 351/221
• CPC Class Codes: A61B 3/1015 for wavefront analysis
• CPC Class Codes: A61B 3/103 for determining refraction, e.g. refractometers, skiascopes
• CPC Class Codes: A61L 31/048 obtained by reactions only involving carbon-to-carbon unsaturated bonds A61L31/041 takes precedence
• CPC Class Codes: C08L 27/16 Homopolymers or copolymers or vinylidene fluoride

Abstract

An improved ophthalmic instrument for in-vivo examination of a human eye including a wavefront sensor that estimates aberrations in reflections of the light formed as an image on the retina of the human eye and a phase compensator that spatially modulates the phase of incident light to compensate for the aberrations estimated by the wavefront sensor Optical elements create an image of a fixation target at the phase compensator, which produces a compensated image of the fixation target that compensates for aberrations estimated by the wavefront sensor. The compensated image of the fixation target produced by the phase compensator is recreated at the human eye to thereby provide the human eye with a view of compensation of the aberrations the human eye as estimated by the wavefront sensor. The phase compensator preferably comprises a variable focus lens that compensates for focusing errors and a deformable mirror that compensates for higher order aberrations. The optical elements preferably comprise a plurality of beam splitters and a plurality of lens groups each functioning as an afocal telescope. In addition, instruments and systems are provided that exploit these capabilities to enable efficient prescription and/or dispensing of corrective optics (e.g., contact lens and glasses).

Claims

1. An ophthalmic instrument for in-vivo examination of a human eye comprising:

a wavefront sensor that estimates aberrations in reflections of the light formed as an image on the retina of the human eye;

a phase compensator, operably coupled to the wavefront sensor, that spatially modulates the phase of incident light to compensate for said aberrations estimated by the wavefront sensor;

a fixation target; and

optical elements that create an image of the fixation target at the phase compensator, which produces a compensated image of the fixation target that compensates for aberrations estimated by the wavefront sensor, and that recreate at the human eye the compensated image of the fixation target produced by the phase compensator, to thereby provide the human eye with a view of compensation of the aberrations the human eye as estimated by the wavefront sensor.

2. The ophthalmic instrument of claim 1, wherein said phase compensator comprises an element selected from the group of:

a variable focus lens that compensates for focusing errors in said aberrations estimated by the wavefront sensor, and deformable mirror that compensates for higher order aberrations in said aberrations estimated by the wavefront sensor.

3. The ophthalmic instrument of claim 1, wherein said phase compensator comprises a variable focus lens that compensates for focusing errors in said aberrations estimated by the a wavefront sensor, and a deformable mirror that compensates for higher order aberrations in said aberrations estimated by the wavefront sensor.

4. The ophthalmic instrument of claim 1, wherein said phase compensator comprises a liquid crystal device that compensates for said aberrations estimated by the wavefront sensor.

5. The ophthalmic instrument of claim 1, wherein said optical elements comprise a plurality of beam splitters.

6. The ophthalmic instrument of claim 5, wherein said plurality of beam splitters comprises a plurality of polarizing beam splitters and corresponding quarter-wave plates.

7. The ophthalmic instrument of claim 1, wherein said optical elements comprise a first beam splitter and first lens group disposed along an optical path between the wavefront sensing source and the human eye.

8. The ophthalmic instrument of claim 7, wherein said first lens group functions as an afocal telescope.

9. The ophthalmic instrument of claim 7, wherein said optical elements further comprise a second beam splitter disposed along an optical path between said first beam splitter and the phase compensator.

10. The ophthalmic instrument of claim 9, wherein said optical elements further comprise a second lens group disposed along an optical path between said second beam splitter and the wavefront sensor.

11. The ophthalmic instrument of claim 10, wherein said second lens group functions as an afocal telescope.

12. The ophthalmic instrument of claim 9, wherein said second beam splitter is disposed along an optical path between said fixation target and said phase compensator.

13. The ophthalmic instrument of claim 12, wherein said optical elements further comprise a third lens group disposed along an optical path between said second beam splitter and said fixation target.

14. The ophthalmic instrument of claim 13, wherein said third lens group functions as an afocal telescope.

15. The ophthalmic instrument of claim 1, wherein said wavefront sensing illumination source and fixation target produce different non-overlapping bands of electromagnetic radiation.

16. The ophthalmic instrument of claim 15, wherein said wavefront sensing illumination source produces infrared laser light and said fixation target produces visible light.

17. The ophthalmic instrument of claim 1, further comprising an imaging illumination source that produced light that is directed to the human eye and reflected there from, wherein said reflected light is directed to said phase compensator to thereby create a compensated image of the human eye, and wherein said compensated image of the human eye is recreated at an imaging device for capture.

18. The ophthalmic instrument of claim 17, wherein said optical elements comprise a first beam splitter and first lens group disposed along an optical path between the imaging illumination source and the human eye, and second beam splitter and second lens group disposed along an optical path between said phase compensator and said imaging device.

19. The ophthalmic instrument of claim 18, wherein said first lens group and said second lens group each function as an afocal telescope.

20. The ophthalmic instrument of claim 1, wherein said wavefront sensor comprises a Hartmann wavefront sensor.

21. The ophthalmic instrument of claim 20, wherein said wavefront sensor includes a lenslet array that forms a Hartmann spot pattern, an imaging device that captures an image of said Hartmann spot pattern, and an image processor that analyzes said image to track movement of spots to thereby estimate phase errors in incident wavefronts.

22. The ophthalmic instrument of claim 1, wherein the wavefront sensor comprises a beam splitter operably disposed between a lenslet array and multiple imaging devices, said lenslet array forming a first array of spots, and said multiple imaging devices capturing multiple images of said first array of spots for use in estimating said aberrations.

23. The ophthalmic instrument of claim 22, wherein said beam splitter comprises a prismatic beam splitter that splits light incident thereto into multiple arms.

24. The ophthalmic instrument of claim 22, wherein said multiple image devices capture at least a first image of said first array of spots at best focus and a second image of said first array of spots near best focus.

25. The ophthalmic instrument of claim 24, further comprising an image processor that:

i) analyzes said first image to identify positions of spots in the first image plane;

ii) identifies a test pixel subaperture corresponding to spots in the first image based upon said positions of such spots;

iii) analyzes said second image to identify positions of spots in the second image plane;

iv) for a plurality of pairs of corresponding spots in the first and second image plane, if a ray passing through positions of a given pair intersects the plane of the lenslet array within a predetermine tolerance from center for a given lenslet, associating the given lenslet with the test pixel aperture corresponding to the first image spot of the given pair; and

v) identifying the lenslets that are associated with a unique test pixel subaperture.

26. The ophthalmic instrument of claim 25, further comprising a reference source distinct from said wavefront sensing illumination source, said reference source producing light that is directed to the lenslet array, which forms a second array of spots, and wherein said multiple imaging devices capture at least a first image of said second array of spots at best focus and a second image of said second array of spots near best focus.

27. The ophthalmic instrument of claim 26, wherein said image processor:

vi) analyzes said first image of said second array of spots to identify positions of spots in the first image plane;

vii) identifies a reference pixel subaperture corresponding to spots in the first image of said second array of spots based upon said positions of such spots;

viii) analyzes said second image of said second array of spots to identify positions of spots in the second image plane;

ix) for a plurality of pairs of corresponding spots in the first and second image plane, if a ray passing through positions of a given pair intersects the plane of the lenslet array within a predetermine tolerance from center for a given lenslet, associating the given lenslet with the reference pixel aperture corresponding to the first image spot of the given pair; and

x) identifying the lenslets that are associated with a unique reference test pixel subaperture.

28. The ophthalmic instrument of claim 27, said image processor generates a list of items comprising one of the following:

lenslets, reference spot locations, fiducial point locations, lenslet centers;

wherein each item is uniquely associated with a given test pixel subaperture and reference pixel subaperture.

29. The ophthalmic instrument of claim 28, wherein subapertures of at least one of said imaging devices used during such wavefront sensing operations to track spot motion is limited to subapertures corresponding to said list.

30. The ophthalmic instrument of claim 22, further comprising an additional imaging device that is operably coupled to said beam splitter to capture at least one image of the pupil image plane of said lenslet array.

31. The ophthalmic instrument of claim 30, wherein each lenslet of said lenslet array comprises a fiducial point, and wherein said additional imaging device captures an image of the pupil image plane of said lenslet array for use in identifying said fiducial points therein.

32. The ophthalmic instrument of claim 30, wherein said additional imaging device captures multiples images of said pupil image plane of said lenslet array for use in automatically identifying lenslet centers therein.

33. The ophthalmic instrument of claim 32, wherein said multiple images are produced via illumination of said lenslet array with a reference source.

34. The ophthalmic instrument of claim 33, wherein said multiple images include at least one first image that shows edges of the lenslets as a dark grid and at least one second image that shows edges of said lenslets as bright grid.

35. The ophthalmic instrument of claim 34, further comprising an image processor that generates a third composite image representing said grid by subtracting the first and second images, thereby removing the average signal of the first and second images.

36. The ophthalmic instrument of claim 35, wherein said image processor utilizes Fourier transform techniques to determine the location and period of said grid.

37. The ophthalmic instrument of claim 36, wherein location of lenslet centers of said lenslet array are derived from location and period of said grid.

38. The ophthalmic instrument of claim 30, said additional imaging device captures at least one image of the pupil image plane of said lenslet array for use in automatically locating position of the pupil of the eye under examination.

39. The ophthalmic instrument of claim 38, further comprising an image processor that processes said at least one image to locate a rough centroid of the at least one image.

40. The ophthalmic instrument of claim 39, wherein said image processor, for a plurality of slices from said rough centroid to periphery of said at least one image, calculates gradient of the intensity along each slice and determines and the pixel location of maximum of the intensity gradient along each slice.

41. The ophthalmic instrument of claim 40, wherein said image processor fits a predetermined shape to said pixel locations of the maximums of the intensity gradient along said slices, and derives the location position of the pupil of the eye under examination from location of the fitted shape.

42. An ophthalmic instrument comprising:

a wavefront sensing mechanism that estimates the aberrations of the eyes of the patient; and

a phase compensating mechanism that operates, for each given prescription in a set of prescriptions that correspond to said aberrations, to generate a compensated image of a fixation target based upon the given prescription, to enable the eyes to view the correction specified by the given prescription.

43. The ophthalmic instrument of claim 42, wherein each given prescription in the set of prescriptions matches said aberrations with a tolerance interval.

44. The ophthalmic instrument of claim 42, wherein feedback is collected from patient to determine the best prescription within the set.

45. An ophthalmic instrument comprising:

a wavefront sensing mechanism that estimates the aberrations of the eyes of the patient; and

a phase compensating mechanism that operates, for each given corrective optic in a set of corrective optic that correspond to said aberrations, to generate a compensated image of a fixation target based upon the given corrective optic, to enable the eyes to view the correction provided by the given corrective optic.

46. The ophthalmic instrument of claim 45, wherein each given corrective optic in the set of corrective optic matches said aberrations with a tolerance interval.

47. The ophthalmic instrument of claim 45, wherein the patient selects one of corrective optics in the set.

48. The ophthalmic instrument of claim 47, wherein the patient is provided with the selected corrective optic.