Apparatus and method for determining relative positional and rotational offsets between a first and second imaging device

• US 20030151720A1
• Filed: 02/11/2003
• Published: 08/14/2003
• Est. Priority Date: 02/11/2002
• Status: Active Grant

• Current Assignee: Amo Manufacturing Usa, Llc (Johnson & Johnson)
• Original Assignee: VISX Incorporated
• Inventors: Persoff, Jeffrey J., Chernyak, Dimitri
• Granted Patent: US 7,040,759 B2
• Time in Patent Office: Days
• US Class Current: 351/206
• CPC Class Codes: A61B 3/1015 for wavefront analysis
• CPC Class Codes: A61B 3/14 Arrangements specially adapted for eye photography apparatus or arrangements for taking photographs per se G03B
• CPC Class Codes: A61B 3/152 for aligning
• CPC Class Codes: G06V 40/19 Sensors therefor

Abstract

The present invention provides an apparatus and method for determining a relative positional and rotational offsets between a first and second imaging device. In exemplary embodiments, the present invention may be used to determine the relative offsets between a Hartmann-Shack wavefront sensor and a pupil camera.

Claims

1. An apparatus for determining a relative positional and rotational offset between a Hartmann-Shack camera and a pupil camera of a wavefront system, the apparatus comprising:

a body; and

a shaped aperture that allows light to be directed to the Hartmann-Shack camera and pupil camera.

2. The apparatus of claim 1 comprising means for positioning the body in an optical axis of the Hartmann-Shack camera and the pupil camera.

3. The apparatus of claim 1 wherein the aperture is rotationally asymmetric.

4. The apparatus of claim 3 wherein the rotationally asymmetrical aperture is substantially cross-shaped.

5. The apparatus of claim 1 wherein the body comprises reflection prevention means.

6. The apparatus of claim 1 wherein a portion of the body is rotatable and moveable in at least two degrees of motion.

7. A method for measuring a rotational and positional offset between a first imaging device and a second imaging device, the method comprising:

obtaining an image of a fixture with the first and second imaging device;

superimposing a marker in a nominal position over the images of the fixture taken with the first and second imaging device;

moving the marker from the nominal position in the image obtained with the first imaging device to a position that is substantially aligned with the images of the fixture;

moving the marker from the nominal position in the image obtained with the second imaging device to a position that is substantially aligned with the images of the fixture; and

comparing movement information of the marker in the first image with movement information of the marker in the second image to determine the rotational and positional offset between the first and second imaging devices.

8. The method of claim 7 wherein the movement information comprise at least one of a translation along an x-axis, a translation along a y axis, and a rotation about a z-axis.

9. The method of claim 7 wherein the fixture comprises a rotationally asymmetric aperture.

10. The method of claim 9 wherein a shape of the marker substantially corresponds to the shape of the rotationally asymmetric aperture in the fixture.

11. The method of claim 7 wherein the first imaging device comprises a Hartmann-Shack camera.

12. The method of claim 7 wherein the nominal positions in the images are a center of the images.

13. A system comprising:

an imaging system comprising a Hartmann-Shack camera and a pupil camera;

a calibration apparatus comprising an aperture that is positionable in an optical path of the Hartmann-Shack camera and pupil camera; and

a control system coupled to the imaging system, wherein the control system is configured to have a first mode and a second mode, wherein the control system in the first mode superimposes a marker in a nominal position over an image of the calibration apparatus taken with the Hartmann-Shack camera and an image taken with the pupil camera and allows the marker to be moved into substantial alignment with the image of the asymmetric aperture,

wherein the control system in the second mode compares the type of movement of the marker in the image taken with the Hartmann-Shack camera with the type of movement of the marker in the image taken with the pupil camera so as to determine the positional and rotational offset between the Hartmann-Shack camera and the pupil camera.

14. The system of claim 13 wherein the aperture is rotationally asymmetric.

15. The system of claim 13 wherein the asymmetric aperture is approximately cross shaped.

16. The system of claim 13 wherein the imaging system is a wavefront system.

17. The system of claim 13 wherein the fixture comprises a non-reflective central portion to prevent reflections.

18. The system of claim 13 comprising a target disposed in the optical axis of the imaging system, wherein the calibration apparatus is positioned between the target and the imaging system.

19. A method for determining relative positional and rotational offsets between a first imaging device and a second imaging device of a system, the method comprising:

providing a body comprising a rotationally asymmetric aperture in an optical path of the first imaging device and a second imaging device;

directing light through the rotationally asymmetric aperture to the first imaging device and second imaging device;

imaging the aperture with the first imaging device and the second imaging device; and

comparing the rotational and positional offsets of the images of the aperture to determine a relative positional and rotational offset between the first and second imaging devices.

20. The method of claim 19 wherein directing comprises reflecting light off of a reflective surface of a target.

21. The method of claim 19 wherein comparing comprises:

superimposing a marker over the image obtained with the first imaging device, wherein the marker substantially corresponds with a shape of the aperture;

moving the marker from a nominal position into substantial alignment with the aperture;

calculating the movement of the marker along the x-axis, y-axis, and rotation about the z-axis;

superimposing a marker over the image obtained with the second imaging device, wherein the marker substantially corresponds with a shape of the aperture;

moving the marker from a nominal position into substantial alignment with the aperture;

calculating the movement of the marker along the x-axis, y-axis, and rotation about the z-axis; and

subtracting the calculated movement of the marker in the image obtained with the first imaging device with the movement of the marker in the image obtained with the second imaging device.

22. A computer program product stored on a computer readable storage medium for registering a first imaging device with a second imaging device, the computer program product comprising:

code for obtaining images with the first imaging device and second imaging device;

code for superimposing a marker over the images of the fixture taken with the first and second imaging device;

code for moving the marker in the image obtained with the first imaging device to substantially align the marker with the fixture;

code for moving the marker in the image obtained with the second imaging device to substantially align the marker with the fixture;

code for comparing the movement information of the marker in the first image with the movement information of the marker in the second image to determine the rotational and positional offset between the first and second imaging devices.

23. A method of registering a first imaging device with a second imaging device, the method comprising:

positioning a fixture so that the fixture is imaged by the first imaging device and second imaging device; and

analyzing the images of the fixture obtained by the first imaging device and the second imaging device to determine a misalignment between the first imaging device and the second imaging device.

24. The method of claim 23 comprising adjusting the position of the fixture so that the fixture is positioned in a desired position in the image obtained by the first imaging device.

25. The method of claim 24 wherein adjusting the position comprises changing at least one of an angular orientation and translational position of the fixture within an optical axis of the first imaging device.

26. The method of claim 24 wherein the desired position is substantially a center of the image obtained by the first imaging device.

27. The method of claim 26 wherein analyzing the images comprises calculating a translational and angular offset of the fixture from a center of the image obtained by the second imaging device.

28. The method of claim 27 wherein calculating comprises:

moving a marker from a center of the image obtained by the second imaging device until the marker is substantially aligned with the fixture; and

measuring an amount of translational movement and angular movement needed to substantially align the marker with the fixture.

29. The method of claim 23 wherein the first imaging device is a Hartmann-Shack camera.

30. The method of claim 29 wherein the fixture comprises a body comprising an aperture, wherein the image obtained by the first imaging device is a spot pattern that corresponds to a shape of the aperture.

31. The method of claim 30 comprising adjusting at least one of a position and angular orientation of the aperture until an intensity in selected portions of the spot pattern are substantially evenly balanced.

32. The method of claim 30 wherein the aperture is asymmetrically shaped, wherein the asymmetrically shaped aperture of the fixture and the marker comprise substantially same shapes.

33. The method of claim 32 wherein the shaped aperture is cross shaped.