Enhanced shape characterization device and method

• US 7,623,250 B2
• Filed: 02/04/2005
• Issued: 11/24/2009
• Est. Priority Date: 02/04/2005
• Status: Active Grant

• Current Assignee: Stryker European Operations Holdings, LLC (Stryker Corporation)
• Original Assignee: Stryker Leibinger GmbH & Co. KG (Stryker Corporation)
• Inventors: Moctezuma de la Barrera, José Luis, Schulz, Waldean A., Malackowski, Donald W.
• Primary Examiner(s): Winakur; Eric F
• Assistant Examiner(s): Laryea; Lawrence N
• Application Number:
  US11/050,920
• Publication Number:
  US 20060241404A1
• Time in Patent Office: 1,754 Days
• Field of Search: 600407-427, 600/429, 600437-440, 600/485, 250/229, 378/197, 345/7, 345/6, 345/156, 345/425, 345/473, 382/118, 382/103, 382/199, 382/128, 382/154, 356600-640, 3561411-14131, 356/375, 356/376, 606/130, 702/85, 702/60, 702/6, 702/127, 702/152, 702/45
• US Class Current: 356/604
• CPC Class Codes: G01B 11/245 using a plurality of fixed, simultaneously operating transducers G01B11/2408 - G01B11/2425, G01B11/255 take precedence
• CPC Class Codes: G01S 5/163 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49

Abstract

The shape and orientation of rigid or nearly rigid moveable bodies are determined using a shape characterization. Sensors capture a plurality of representations of different perspectives of the body that are analyzed to determine a bounding volume of the body. The shape of the body is determined from the bounding volume. The position of the body is determined using tracking devices that sense the position of the body. The bounding volume and position information are combined to define the shape and orientation in space of the body, and in particular the position of a point of interest on the body.

Claims

1. A system for calibrating a tracked shape and orientation of a body comprising:

a computer navigation system;

a sensing device adapted to generate a series of representations of a shape of the body;

a tracking device associated with the body in a fixed relation to the body, the tracking device adapted to be detected by the computer navigation system to locate the body relative to the computer navigation system; and

the computer navigation system having a central processing unit that is adapted to process the series of representations and a relative location of the body to the computer navigation system to determine the shape and orientation of the body relative to the tracking device, whereby the shape and orientation of the body is calibrated to the tracking device.

2. The system of claim 1, wherein the sensing device includes multiple digital cameras and each representation is an image captured by the camera.

3. The system of claim 2, wherein the sensing device is a video camera and the representation is a frame of video captured by the video camera.

4. The system of claim 2, wherein the system also includes a fixed background that increases the contrast between portions of the representation that represent the background and portions that represent the body to aid in identifying edges of the body in the representation.

5. The system of claim 1, wherein the sensing device senses the shadow cast by the body and the representation is an image of the shadow.

6. The system of claim 5, wherein the sensing device is an array of charge coupled devices that senses the movement of the shadow cast by the body as the body is moved relative to the sensing device.

7. The system of claim 5, wherein the sensing device includes at least one light source positioned with respect to at least one two-dimensional sensor that is adapted to distinguish regions that are in the shadow from regions that are not in the shadow.

8. The system of claim 1, wherein the tracking device is an optical tracking system.

9. The system of claim 8, wherein the tracking device includes an active emitter associated with the body.

10. The system of claim 8, wherein the tracking device includes light emitting diodes.

11. The system of claim 1, wherein the tracking device is a non-optical tracking device.

12. The system of claim 11, wherein the tracking device is a magnetic tracking device.

13. The system of claim 1, wherein the tracking device is fixedly attached to the body.

14. The system of claim 1, wherein the tracking device is integral with the body.

15. The system of claim 1, wherein the sensing device is a single camera that captures multiple images as the body is moved relative to the camera and each representations is an image captured by the camera.

16. The system of claim 1, wherein the computer navigation system tracks the position of a landmark point on the body based on the determined shape and orientation of the body.

17. The system of claim 1, wherein the computer navigation system compares an estimate of the shape of the body with a model of the body selected from a plurality of models stored in the computer navigation system.

18. The system of claim 1, further comprising means for generating edge information from at least one of the representations, wherein the central processing unit can use the edge information to determine the shape and orientation of the body.

19. The system of claim 18, further comprising means for estimating a bounding pyramid of the body from the edge information, wherein the central processing unit can use the bounding pyramid to determine the shape and orientation of the body.

20. The system of claim 19, further comprising means for estimating a bounding volume of the body from the bounding pyramid, wherein the central processing unit can use the bounding volume to determine the shape and orientation of the body.

21. A system for calibrating a tracked shape and orientation of a body comprising:

a computer navigation system;

a sensing device adapted to generate a series of representations of a shape of the body based on relative movement between the body and the sensing device;

an emitter associated with the body in a fixed relation to the body, the emitter adapted to be detected by the computer navigation system to locate the body relative to the computer navigation system; and

the computer navigation system having a central processing unit that is adapted to process the series of representations and a relative location of the body to the computer navigation system to determine the shape and orientation of the body relative to the emitter, whereby the shape and orientation of the body is calibrated to the emitter.

22. The system of claim 21, wherein the sensing device includes multiple digital video cameras.

23. The system of claim 22, wherein the system also includes a fixed background that increases the contrast between portions of the representation that represent the background and portions that represent the body to aid in identifying edges of the body in the representation.

24. The system of claim 21, wherein the tracking device is an optical tracking system.

25. The system of claim 24, wherein the tracking device includes an active emitter associated with the body.

26. The system of claim 24, wherein the tracking device includes light emitting diodes.

27. The system of claim 21, wherein the tracking device is a non-optical tracking device.

28. The system of claim 27, wherein the tracking device is a magnetic tracking device.

29. The system of claim 21, wherein the tracking device is fixedly attached to the body.

30. The system of claim 21, wherein the tracking device is integral with the body.

31. The system of claim 21, wherein the sensing device is a single camera and each representation is an image of the body captured by the camera.

32. The system of claim 21, wherein the sensing device senses a shadow cast by the body.

33. The system of claim 21, wherein the computer navigation system tracks the position of a landmark point on the body based on the determined shape and orientation of the body.

34. The system of claim 21, wherein the computer navigation system compares an estimate of the shape of the body with a model of the body selected from a plurality of models stored in the computer navigation system.

35. A method of determining the shape of a body using a computer navigation system, the method comprising the steps of:

generating a series of representations of the body;

generating edge information from at least one of the representations;

estimating one or more bounding pyramids from the edge information;

determining a composite bounding volume of the body from the one or more bounding pyramids;

determining the shape of the body from the composite bounding volume; and

determining a position and an orientation of the body using a tracking device associated with the body that communicates with the computer navigation system.

36. The method of claim 35, wherein the method includes calibrating the body to the computer navigation system so that the computer navigation system can track both the position and orientation of the body.

37. The method of claim 35, wherein the generating step is done using a video camera and each representation is a frame of video from a video camera.

38. The method of claim 35, wherein the generating step is done by sensing the shadow cast by the body and each representation is an image of the shadow.

39. The method of claim 35, wherein the generating step is done by a single camera that captures multiple images as the body is moved relative to the camera.

40. The system of claim 35, wherein the computer navigation system tracks the position of a landmark point on the body based on the determined shape and orientation of the body.

41. The system of claim 35, wherein the determining step includes comparing an estimate of the shape of the body with a model of the body selected from a plurality of models stored in the computer navigation system.

42. The method of claim 35, wherein the step of generating a series of representations of the body comprises the steps of capturing a series of images of the body and isolating the representations of the body from representations of a background in the series of images.

43. The method of claim 35, further comprising the step of calibrating a sensing device to estimate a position and orientation of the sensing device relative to the computer navigation system, wherein the sensing device is used to generate the series of representations of the body.

44. The method of claim 43, wherein the step of calibrating the sensing device further includes the steps of generating a series of representations of a calibration body with a known shape, wherein each representation is a known perspective view of the calibration body, identifying edges of the calibration body from the series of representations, estimating a position and orientation of each sensing device, comparing the identified edges with known edge information of the calibration body, and correcting the estimated position and orientation of each sensing device based on the comparing step.

45. The method of claim 35, wherein the step of determining the composite bounding volume includes the step of intersecting multiple bounding pyramids with one another.

46. A method of determining the shape and orientation of a body using a computer navigation system, the method comprising the steps of:

generating a series of representations of the body from at least two perspectives;

determining a composite bounding volume of the body from the series of representations;

estimating the shape of the body from the composite bounding volume;

comparing the estimated shape of the body to stored shape information using comparison metrics;

refining the estimated shape based on the comparison; and

determining the position and orientation of the body from the shape of the body and the series of representations of the body.

47. The method of claim 46, wherein the generating step is done using at least two video cameras and each representation is a frame of video from each video camera.

48. The method of claim 46, wherein the generating step is done by sensing at least two shadows cast by the body and each representation is an image of the shadow.