Position sensing sensor, method and system

• US 20040188616A1
• Filed: 03/28/2003
• Published: 09/30/2004
• Est. Priority Date: 03/28/2003
• Status: Active Grant

• Current Assignee: Stryker Corporation
• Original Assignee: Howmedica Leibinger Inc. (Stryker Corporation)
• Inventors: Schulz, Waldean A., Wu, Chunwu
• Granted Patent: US 7,049,594 B2
• Time in Patent Office: Days
• US Class Current: 250/338.1
• CPC Class Codes: A61B 2034/2055 Optical tracking systems
• CPC Class Codes: A61B 2034/2065 Tracking using image or pattern recognition
• CPC Class Codes: A61B 2090/3983 Reference marker arrangements for use with image guided surgery
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: G01S 3/7835 using coding masks
• CPC Class Codes: G01S 5/16 using electromagnetic waves other than radio waves

Abstract

A sensor for determining a component of a location of a radiation source within a three dimensional volume includes a mask having a series of openings that has a predetermined mathematical relationship among the openings within the series of openings and defines a mask reference line; a detector surface spaced from the mask where radiation passing through the mask creates a mask image on the detector surface having a series of peaks and an image reference line within the mask image that can be located and where at least 50% of the mask image is projected onto the detection surface; and a calculating unit to determine a location of the image reference line within the mask image and the component of the location of the radiation source from the calculated location of the image reference line within the mask image. A method and system for using this sensor are also disclosed.

Claims

1. A method of determining a component of a location of a radiation source within a three dimensional volume, the method comprising the steps of:

passing radiation from the radiation source through a mask having a series of openings onto a detector surface, wherein the series of openings has a predetermined mathematical relationship among the openings within the series of openings and wherein the series of openings define a mask reference line, to create a mask image having a series of peaks, and having an image reference line within the mask image that can be located and wherein at least 50% of the mask image is projected onto the detector surface;

calculating a location of the mask image on the detector surface;

calculating a location of the image reference line within the mask image; and

calculating the component of the location of the radiation source from the calculated location of the image reference line within the mask image.

2. The method of claim 1 wherein the location of the mask image on the detector surface is calculated using substantially all of the mask image.

3. The method of claim 1 wherein the predetermined mathematical relationship among the openings is a series of equally spaced slits on either side of a central opaque section wider than the spacing between adjacent slits.

4. The method of claim 1 wherein the predetermined mathematical relationship among the openings is a series of equally spaced slits on either side of a central opaque section narrower than the spacing between adjacent slits.

5. The method of claim 1 wherein the predetermined mathematical relationship among the openings is a series of equally spaced slits on either side of a central slit that is wider than the other slits.

6. The method of claim 1 wherein the predetermined mathematical relationship among the openings is a series of equally spaced slits on either side of a central slit that is narrower than the other slits.

7. The method of claim 1 wherein there are two or more series of slits.

8. The method of claim 1 wherein the predetermined mathematical relationship among the openings is a transparency pattern variable in the direction parallel to the longitudinal direction of the detector surface and is constant in the direction perpendicular to the longitudinal direction of the detector surface.

9. The method of claim 8 wherein the transparency pattern is a mathematical function.

10. The method of claim 9 wherein the mathematical function is a sine function.

11. The method of claim 10 wherein the sine function has a different period on either side of the mask reference line.

12. The method of claim 1 wherein the calculating of the location of the image reference line includes the steps of:

identifying a characteristic of the image reference line; and

locating a portion of the image that corresponds to the characteristic of the image reference line.

13. The method of claim 1 wherein the calculation of the location of the image reference line includes the steps of:

locating each peak of the image first on a first portion of the mask image and second on a second portion of the mask image; and

calculating the location of the image reference line from the location of each valid peak in the image.

14. The method of claim 12 that includes the step of compensating in the calculation for missing or invalid peaks.

15. The method of claim 1 wherein the calculation of the location of the image reference line includes the step of convolving of the image with a kernel based on the predetermined mathematical relationship among the openings.

16. The method of claim 15 wherein the calculation of the location of the image reference line includes the step of fitting the image to a function based on the predetermined mathematical relationship among the openings using an iterative data fitting algorithm.

17. The method of claim 1 wherein the calculation of the location of the image reference line includes the step of filtering the image to minimize background noise.

18. The method of claim 1 wherein the calculation of the location of the image reference line includes the step of estimating an estimated location of the image reference line within the mask image;

and calculating an actual location of the image reference line within the mask image from the estimated location of the image reference line within the mask image.

19. The method of claim 1 that includes the step of reporting if the image is at either extreme of the image detector.

20. The method of claim 1 wherein the mask reference line is not offset from a middle of the mask.

21. The method of claim 1 wherein the mask reference line is offset from a middle of the mask by a predetermined value.

22. The method of claim 1 wherein the image detector is a charge coupled device one pixel wide and a length longer than a width of the series of slits in the mask.

23. The method of claim 1 wherein the source of radiation is a light emitting diode.

24. The method of claim 22 wherein the light emitting diode emits infrared radiation.

25. The method of claim 1 wherein the mask creates a second image reference line perpendicular to the image reference line and wherein the image reference line and the second image reference line intersect to form an image reference point.

26. A system for determining a component of a location of a radiation source within a three dimensional volume comprising:

a mask having a series of openings wherein the series of openings has a predetermined mathematical relationship among the openings within the series of openings, wherein the series of openings define a mask reference line;

a detector surface spaced from the mask wherein the mask creates a mask image on the detector surface having a series of peaks and having an image reference line within the mask image that can be located and wherein at least 50% of the mask image is projected onto the detector surface;

a first circuit to calculate a location of the image reference line within the mask image; and

a second circuit to calculate the component of the location of the radiation source from the calculated location of the image reference line within the mask image.

27. The system of claim 26 wherein the location of the mask image on the detector surface is calculated using substantially all of the mask image.

28. The system of claim 26 wherein the predetermined mathematical relationship among the openings is a series of equally spaced slits on either side of a central opaque section wider than the spacing between adjacent slits.

29. The system of claim 26 wherein the predetermined mathematical relationship among the openings is a series of equally spaced slits on either side of a central opaque section narrower than the spacing between adjacent slits.

30. The system of claim 26 wherein the predetermined mathematical relationship among the openings is a series of equally spaced slits on either side of a central slit that is wider than the other slits.

31. The system of claim 26 wherein the predetermined mathematical relationship among the openings is a series of equally spaced slits on either side of a central slit that is narrower than the other slits.

32. The system of claim 26 wherein there are two or more series of slits.

33. The system of claim 26 wherein the predetermined mathematical relationship among the openings is a transparency pattern variable in the direction parallel to the longitudinal direction of the detector surface and is constant in the direction perpendicular to the direction of the detector surface.

34. The system of claim 33 wherein the transparency pattern is a mathematical function.

35. The system of claim 34 wherein the mathematical relationship is a sine function.

36. The system of claim 35 wherein the sine function has a different period on either side of the mask reference line.

37. The system of claim 26 wherein the first circuit includes a third circuit to estimate of the location of the image reference line by identifying a characteristic of the image reference line of the mask;

and locating a portion of the image that corresponds to the characteristic of the image reference line.

38. The system of claim 26 wherein the first circuit locates each peak of the image first on a first portion of the mask image and second on a second portion of the mask image;

and calculates the location of the image reference line from the location of each valid peak in the mask image.

39. The system of claim 38 that includes a fourth circuit to compensate in the calculation for missing or invalid peaks.

40. The system of claim 26 wherein the first circuit also convolves of the mask image with a kernel based on the predetermined mathematical relationship among the openings.

41. The system of claim 40 wherein the first circuit fits the mask image to a function based on the predetermined mathematical relationship among the openings using an iterative data fitting algorithm.

42. The system of claim 26 wherein the first circuit also filters the mask image to minimize background noise.

43. The system of claim 26 wherein the first circuit also estimates an estimated location of the image reference line within the mask image;

and calculates an actual location of the image reference line within the mask image from the estimated location of the image reference line within the mask image.

44. The system of claim 26 that includes a fifth circuit to report if the image is at either extreme of the image detector.

45. The system of claim 26 wherein the mask reference line is not offset from a middle of the mask.

46. The system of claim 26 wherein the mask reference line is offset from a middle of the mask by a predetermined value.

47. The system of claim 26 wherein the image detector is a charge coupled device one pixel wide and has a length longer than a width of the series of slits in the mask.

48. The system of claim 26 wherein the source of radiation is a light emitting diode.

49. The system of claim 48 wherein the light emitting diode emits infrared radiation.

50. The system of claim 26 wherein the mask creates a second image reference line perpendicular to the image reference line and wherein the image reference line and the second image reference line intersect to form an image reference point.

51. A sensor for determining a component of a location of a radiation source within a three dimensional volume comprising:

a mask having a series of openings wherein the series of openings has a predetermined mathematical relationship among the openings within the series of openings and wherein the series of opening defines a mask reference line;

a detector surface spaced from the mask wherein the series of openings in the mask creates a mask image on the detector surface having a series of peaks and an image reference line within the mask image that can be located and wherein at least 50% of the mask image is projected onto the detection surface; and

a calculating unit to determine a location of the image reference line within the mask image and the component of the location of the radiation source from the calculated location of the image reference line within the mask image.

52. The sensor of claim 51 wherein the calculating unit calculates the location of the mask reference line on the detector surface using substantially all of the mask image.

53. The sensor of claim 51 wherein the fixed relationship of the openings is a series of equally spaced slits on either side of a central opaque section wider than the spacing between adjacent slits.

54. The sensor of claim 51 wherein the fixed relationship of the openings is a series of equally spaced slits on either side of a central opaque section narrower than the spacing between adjacent slits.

55. The sensor of claim 51 wherein the fixed relationship of the openings is a series of equally spaced slits on either side of a central slit that is wider than the other slits.

56. The sensor of claim 51 wherein the fixed relationship of the openings is a series of equally spaced slits on either side of a central slit that is narrower than the other slits.

57. The sensor of claim 51 wherein there are two or more series of slits.

58. The sensor of claim 51 wherein the fixed relationship of the openings is a transparency pattern variable in the direction parallel to the longitudinal direction of the detector surface and is constant in a direction perpendicular to the longitudinal direction of the detector surface.

59. The sensor of claim 58 wherein the transparency pattern is a mathematical function.

60. The sensor of claim 59 wherein the mathematical function is a sine function.

61. The sensor of claim 60 wherein the sine function has a different period on either side of the mask reference line.

62. The sensor of claim 51 wherein the mask reference line is not offset from a middle of the mask.

63. The sensor of claim 51 wherein the mask reference line is offset from a middle of the mask by a predetermined value.

64. The sensor of claim 51 wherein the image detector is a charge coupled device one pixel wide and has a length longer than a width of the series of slits in the mask.

65. The sensor of claim 51 wherein the image detector detects infrared radiation.

66. The sensor of claim 51 wherein the mask creates a second image reference line perpendicular to the image reference line and wherein the image reference line and the second image reference line intersect to form an image reference point.