RETROREFLECTIVE MARKER-TRACKING SYSTEMS

Abstract

A marker-tracking system includes an object, a marker illuminating device, a marker sensing device, and a computing device. The object includes a first retroreflective marker having a shape that is substantially defined by two spherical caps of different radii that are disposed substantially concentric in relation to one another. The marker illuminating device substantially illuminates the first retroreflective marker, the marker sensing device detects the illuminated first retroreflective marker and generates first data indicative of the location of the illuminated first retroreflective marker in space, and the computing device processes the first data generated by the marker sensing device to determine a position and/or orientation of the object in space.

Description

DESCRIPTION OF DRAWINGS

FIG. 1 shows a marker-tracking system in a medical application context.

FIGS. 2 a, 2b, 2c, and 2d each shows a cross-sectional view of an enhanced retroreflective marker.

FIGS. 3 a and 3b show cross-sectional views of five enhanced retroreflective markers, each formed by a sphere and a spherical cavity.

FIG. 4 shows cross-sectional views of three enhanced retroreflective markers, each formed by two spherical caps.

FIG. 5 shows cross-sectional views of three enhanced retroreflective markers, each formed by an integral unit defined by two spherical cap components.

FIG. 6 a shows a path of light with respect to an enhanced retroreflective marker having a high split line and a fully-reflectorized rear surface.

FIG. 6 b shows a path of light with respect to an enhanced retroreflective marker having a low split line and a fully-reflectorized rear surface.

FIG. 6 c shows paths of light with respect to an enhanced retroreflective marker having a high split line and a partially-reflectorized rear surface.

FIG. 7 a shows a device with respect to an observation point of a marker-tracking system, the device including five multi-lens high refractive index markers.

FIG. 7 b shows a view of a proximal marker and a distal marker from the observation point of FIG. 7a.

FIG. 7 c shows a device with respect to an observation point of a marker-tracking system, the device including five enhanced retroreflective markers.

FIG. 7 d shows a view of a proximal marker from the observation point of FIG. 7c.

FIG. 8 a shows a retroreflective marker-tracking system in which multi-lens high refractive index retroreflective markers are deployed.

FIG. 8 b shows a retroreflective marker-tracking system in which enhanced retroreflective markers are deployed.

FIG. 8 c shows a side view of a light path with respect to a partially-occluded enhanced retroreflective marker of FIG. 8b.

FIG. 8 d shows a front view of the partially-occluded enhanced retroreflective marker of FIG. 8b.

FIG. 9 shows tiny glass beads embedded in a substrate.

Claims

1. A system comprising: an object including a first retroreflective marker having a shape that is substantially defined by two spherical caps of different radii that are disposed substantially concentric in relation to one another;a marker illuminating device for substantially illuminating the first retroreflective marker;a marker sensing device for detecting the illuminated first retroreflective marker and for generating first data indicative of the location of the illuminated first retroreflective marker in space; anda computing device for processing the first data generated by the marker sensing device to determine a position and/or orientation of the object in space.

2. The system of claim 1, wherein the shape of the first retroreflective marker is further defined by one or more flanges.

3. The system of claim 1, wherein the first retroreflective marker has a uniform refractive index.

4. The system of claim 1, wherein the first retroreflective marker retroreflects light when light rays emanating from the marker illuminating device enter the first retroreflective marker within entrance angles ranging between 0° and ±β°.

5. The system of claim 1, wherein the shape that defines the first retroreflective marker is formed by a sphere and a spherical cavity that are separated by a medium.

6. The system of claim 5, wherein: the sphere is defined by a radius R1; andthe spherical cavity is defined by an inner radius R2, an outer radius R3, a height h, and a base radius a.

7. The system of claim 5, wherein the outer radius R3 of the spherical cavity is substantially equal to the height h of the spherical cavity.

8. The system of claim 5, wherein the outer radius R3 of the spherical cavity is greater than the height h of the spherical cavity.

9. The system of claim 5, wherein the outer radius R3 of the spherical cavity is less than the height h of the spherical cavity.

10. The system of claim 5, wherein the inner radius R2 of the spherical cavity is substantially equal to the radius R1 of the sphere.

11. The system of claim 5, wherein the inner radius R2 of the spherical cavity is greater than the radius R1 of the sphere.

12. The system of claim 11, wherein a reflective material is applied directly on a cavity-side surface of the spherical cavity.

13. The system of claim 11, wherein a reflective material is applied directly on a non-cavity-side surface of the spherical cavity.

14. The system of claim 5, wherein a reflective material is applied directly on a surface of the sphere.

15. The system of claim 5, wherein a reflective material is applied directly on a non-cavity side surface of the spherical cavity.

16. The system of claim 1, wherein the shape that defines the first retroreflective marker is formed by a first spherical cap and a second spherical cap.

17. The system of claim 16, wherein: the first spherical cap is defined by a radius R4, a height h1, and a base radius a1; andthe second spherical cap is defined by a radius R5, a height h2, and a base radius a2.

18. The system of claim 17, wherein the height h1 is greater than the radius R4.

19. The system of claim 17, wherein the height h2 is greater than the radius R5.

20. The system of claim 17, wherein the height h1 is substantially equal to the radius R4 and the height h2 is substantially equal to the radius R5.

21. The system of claim 16, wherein a reflective material is applied directly on a surface of the first spherical cap.

22. The system of claim 16, wherein a reflective material is applied directly on a surface of the second spherical cap.

23. The system of claim 1, wherein the shape that defines the first retroreflective marker is formed by a first spherical cap component and a second spherical cap component, the first and the second spherical cap components being constructed as an integral unit.

24. The system of claim 23, wherein: the first spherical cap component is defined by a radius R6, a height h3, and a base radius a3; andthe second spherical cap component is defined by a radius R7, a height h4, and a base radius a4.

25. The system of claim 24, wherein the height h3 is greater than the radius R6.

26. The system of claim 24, wherein the height h4 is greater than the radius R7.

27. The system of claim 24, wherein the height h3 is substantially equal to the radius R6 and the height h4 is substantially equal to the radius R7.

28. The system of claim 23, wherein a reflective material is applied directly on a surface of the first spherical cap component.

29. The system of claim 23, wherein a reflective material is applied directly on a surface of the second spherical cap component.

30. The system of claim 1, wherein the first retroreflective marker is formed of a shatter-resistant material.

31. The system of claim 1, wherein the first retroreflective marker is formed of a material having a relatively low refractive index.

32. The system of claim 1, wherein the first retroreflective marker is formed of a material having a relatively high refractive index.

33. The system of claim 1, wherein a reflective material is applied directly on a rear surface of the first retroreflective marker.

34. The system of claim 1, wherein a reflective material is applied directly on one or more portions of a rear surface of the first retroreflective marker.

35. The system of claim 34, wherein the one or more portions of the rear surface of the retroreflective marker upon which the reflective material is applied comprises less than an entirety of the rear surface.

36. The system of claim 1, wherein the first retroreflective marker is configured to diffusely retroreflect light.

37. The system of claim 1, wherein the object further includes at least one other retroreflective marker having a shape that is substantially defined by two spherical caps of different radii that are disposed substantially concentric in relation to one another.

38. The system of claim 37, wherein the first retroreflective marker and the at least one other retroreflective marker are disposed on the object relative to one another such that only one of the retroreflective markers retroreflects light at a time when the retroreflective markers are simultaneously illuminated by the marker illuminating device.

39. The system of claim 37, wherein the first retroreflective marker and the at least one other retroreflective marker are disposed on the object relative to one another such that at least two retroreflective markers retroreflect light when the retroreflective markers are simultaneously illuminated by the marker illuminating device.

40. The system of claim 39, wherein the marker sensing device: detects the at least one other illuminated retroreflective marker, and for each detected marker, generates data indicative of the location of the respective illuminated marker in space.

41. The system of claim 40, wherein the computing device processes the data generated by the marker sensing device to determine the position and/or orientation of the object in space.

42. The system of claim 37, wherein the retroreflective markers are sized and dimensioned such that the marker sensing device detects a single discrete source of reflected light when the marker illuminating device illuminates the retroreflective markers simultaneously.

43. The system of claim 37, wherein the retroreflective markers are sized and dimensioned such that the marker sensing device detects multiple discrete sources of reflected light when the marker illuminating device illuminates the retroreflective markers simultaneously.

44. The system of claim 43, wherein at least one of the multiple discrete sources of reflected light is formed when the marker illuminating device illuminates at least two retroreflective markers simultaneously.

45. The system of claim 1, wherein the radii of the spherical caps that substantially define the shape of the first retroreflective marker are selected so that an intensity of a reflected light image that is detected when the first retroreflective marker is illuminated remains relatively constant even as an observation angle between the marker illuminating device and the marker sensing device varies