Simple system for endoscopic non-contact three-dimentional measurement

• US 6,459,481 B1
• Filed: 05/05/2000
• Issued: 10/01/2002
• Est. Priority Date: 05/06/1999
• Status: Expired due to Fees

• Current Assignee: Schaack, David F.
• Original Assignee: Schaack, David F.
• Inventors: Schaack, David F.
• Primary Examiner(s): STAFIRA, MICHAEL PATRICK
• Application Number:
  US09/565,441
• Time in Patent Office: 879 Days
• Field of Search: 356/241.1, 356/241.3, 356/241.4, 356/241.5, 356/241.6, 356/139.03, 356/376, 702/95, 702/153, 700/69, 700/174
• US Class Current: 356/241.1
• CPC Class Codes: A61B 1/04 combined with photographic or television appliances
• CPC Class Codes: A61B 5/1076 for measuring dimensions inside body cavities, e.g. using catheters A61B3/1005 takes precedence
• CPC Class Codes: G01S 11/12 using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 5/16 using electromagnetic waves other than radio waves

Abstract

Three-dimensional endoscopic measurements are made by adding an array of reference target points to the scene viewed by an endoscopic camera and characterizing the image formed by the camera when it views the scene from two or more viewing positions. Methods and apparatus are taught which allow one to make accurate measurements with any endoscope, without requiring any modification to the endoscope. Under certain circumstances, the measurements can be made without any pre-calibration of the endoscopic camera.

A general measurement reference apparatus comprises a reference target array which is placed near to and fixed with respect to an object of interest inside an enclosure by means of a reference array holding apparatus and a reference array insertion apparatus. This measurement reference apparatus can be used to make either perspective dimensional measurements or to make conventional photogrammetric measurements of the object of interest.

A general measurement apparatus to be used with the new methods comprises a reference target array which is placed near to and fixed with respect to an object of interest inside an enclosure by means of a reference array holding apparatus and a reference array insertion apparatus. In a version of this apparatus the reference array holding apparatus may attach the reference array directly to the object of interest and the combination may be inserted into the enclosure by the insertion apparatus. The general measurement apparatus also comprises an endoscopic camera located inside the enclosure. The camera is moved with respect to the object by a camera moving apparatus. Images formed by the camera are measured with an image measurement apparatus. These measurements are supplied to a computing apparatus which computes the desired three-dimensional distances. The measurement results are displayed to the user by a display apparatus.

Claims

1. An apparatus for measuring three-dimensional distances between individual points on an object, said object being located inside an enclosure, said enclosure having an interior and an exterior and having a wall located therebetween, said wall having at least one opening therein through which the interior of the enclosure can be accessed, comprising:

(a) a camera for forming an image, said camera being located inside the enclosure;

(b) means for moving the camera in a spatial relationship with respect to the object;

(c) an array of reference target points having at least three non-colinear target points, said target points having locations characterized in a reference coordinate system;

(d) means for inserting said array of reference target points through one of said at least one opening from the exterior to the interior of the enclosure;

(e) means for holding said array in a fixed spatial relationship with respect to the object, said means for holding being cooperatively engaged with said means for inserting and with the array whereby said array is disposed at a position near to and fixed with respect to said object;

(f) means for measuring the positions of points in an image formed by the camera;

(g) means for computing, said means for computing receiving measurements from said means for measuring, said means for computing being further adapted to compute the three dimensional distances between said individual points on said object; and

(h) means for displaying the results of the measurement computations.

2. The apparatus of claim 1 wherein the camera is incorporated into an endoscope, said endoscope having a distal portion that is inserted through an access port in said wall.

3. The apparatus of claim 2 wherein the endoscope is flexible and wherein said means for moving comprises means for variably bending a section of said endoscope.

4. The apparatus of claim 3 wherein said means for variably bending comprises an endoscope guide tube having an articulation means.

5. The apparatus of claim 3 wherein said means for variably bending comprises an internal articulation means of said endoscope.

6. The apparatus of claim 2 wherein the endoscope has a length and wherein said means for moving comprises means to translate the endoscope in a direction substantially oriented along its length.

7. The apparatus of claim 2 wherein the endoscope is rigid and has a length and wherein said means for moving comprises means to rotate the endoscope about an axis, said axis being located near said access port and said axis being oriented substantially perpendicular to said length.

8. The apparatus of claim 2 wherein said means for holding is adapted to hold both the endoscope and said means for inserting and wherein said means for holding is attached to said wall.

9. The apparatus of claim 2 wherein said means for holding comprises an endoscope guide tube.

10. The apparatus of claim 1 wherein said means for inserting comprises a wire.

11. The apparatus of claim 10 wherein said wire is coated with a dissipative polymer.

12. The apparatus of claim 10 wherein said means for holding comprises means for clamping said wire to the wall of the enclosure.

13. The apparatus of claim 10 wherein said means for holding comprises an endoscope guide tube.

14. The apparatus of claim 1 wherein said means for holding comprises an endoscope being held fixed with respect to the object.

15. The apparatus of claim 1 wherein said array of reference target points is rotatably attached to said means for inserting and wherein said means for inserting further comprises means for disposing the array at a selectable angular orientation with respect to said means for inserting.

16. The apparatus of claim 15 further comprising means for selecting the angular orientation of the array from the exterior of the enclosure.

17. The apparatus of claim 1 further comprising array collapsing means and array expanding means, said array being collapsed to a small cross-section for insertion and expanded to an operating configuration after insertion.

18. The apparatus of claim 17 wherein said array collapsing means comprises an auxiliary insertion tool.

19. The apparatus of claim 17 wherein said means for inserting comprises both said array collapsing means and said array expanding means.

20. The apparatus of claim 17 wherein said reference target points are marked on an outer surface of an inflatable bladder.

21. The apparatus of claim 20 further comprising a temperature sensor for measurement of a temperature of said bladder.

22. The apparatus of claim 1 wherein said reference target points are marked on a plane surface.

23. The apparatus of claim 22 wherein the plane surface is a surface of a rigid body.

24. The apparatus of claim 22 further comprising at least one indicium marked on said array of reference target points, said indicium being adapted to provide a-priori information about the spatial location of said camera with respect to said array when said indicium appears in said image.

25. The apparatus of claim 22 wherein the plane surface is a flexible membrane being stretched to conform to a plane.

26. The apparatus of claim 1 wherein said array of reference target points contains at least four target points and wherein at least one target point lies outside of a plane defined by three other target points.

27. The apparatus of claim 26 further comprising two parallel planes spaced apart along their mutual perpendicular, both of the planes having reference target points marked thereupon, and at least one of the planes being adapted to allow target points marked on the other plane to be visible when target points marked upon itself are visible.

28. The apparatus of claim 26 wherein said reference target points are marked on at least two of three planar adjacent sides of a three-dimensional surface, said three planar adjacent sides meeting in a corner.

29. The apparatus of claim 26 further comprising a plane surface marked with at least three reference target points, and a post having a visible end, said post being mounted substantially perpendicular to the plane surface, and said post being marked with a reference target point at said visible end.

30. The apparatus of claim 26 further comprising an inflatable bladder, said reference target points being marked on an outer surface of said bladder.

31. The apparatus of claim 1 wherein said array of reference target points comprises a plurality of sets of reference target points, at least two of the sets being spaced apart by a distance approximately equal to a distance of interest on the object, whereby a mode 2 perspective dimensional measurement can be made of the distance of interest.

32. A reference apparatus for providing reference information in making three-dimensional distance measurements on an object located inside of an enclosure, said enclosure having an interior and an exterior and having a wall located therebetween, said wall having at least one opening therein through which the interior of the enclosure can be accessed, comprising:

(a) an array of reference target points having at least three non-colinear target points, said target points having locations characterized in a reference coordinate system;

(b) array insertion apparatus cooperatively engaged with said array of target reference points, whereby the array of target reference points is inserted through one of said at least one opening from the exterior to the interior of the enclosure; and

(c) array holding apparatus adapted to being fixed in position with respect to the object, said array holding apparatus being cooperatively engaged with the insertion apparatus and with the array of target reference points, whereby said array of target reference points is disposed at a position near to and fixed with respect to said object.

33. The apparatus of claim 32 wherein said array insertion apparatus comprises a wire.

34. The apparatus of claim 33 wherein said array holding apparatus comprises means for clamping said wire to the wall of the enclosure.

35. The apparatus of claim 32 wherein said array of reference target points is rotatably attached to said array insertion apparatus and wherein said insertion apparatus further comprises means for disposing the array at a selectable angular orientation with respect to said insertion apparatus.

36. The apparatus of claim 32 further comprising array collapsing means and array expanding means, said array being collapsed to a small cross-section for insertion and expanded to an operating configuration after insertion.

37. The apparatus of claim 32 wherein said array of reference target points contains at least four target points and wherein at least one target point lies outside of a plane defined by three other target points.

38. A method for determining three-dimensional coordinates for at least one object point on an object, thereby determining a location vector for each of said at least one object point, said object being located inside an enclosure, said enclosure having an interior, said enclosure also having at least one opening through which its interior can be accessed, comprising the steps of:

(a) inserting a camera for forming and acquiring images through an opening in the enclosure;

(b) inserting a reference target array through an opening in the enclosure;

(c) disposing the reference target array at a position sufficiently near to said at least one object point that said at least one object point and at least a portion of said reference target array can both be contained in a single image formed by the camera;

(d) holding the reference target array fixed in position with respect to said object;

(e) moving the camera successively to at least two viewing positions with respect to said object, at least two of said at least two viewing positions being separated sufficiently so that an angle subtended by these positions at each of said at least one point on the object is substantially different from zero;

(f) acquiring images containing said at least one object point and at least a portion of said reference target array at each of said at least two viewing positions; and

(g) determining, from the images, the three-dimensional coordinates of said at least one object point in a reference coordinate system defined by the reference target array.

39. The method of claim 38 wherein the step of inserting a reference target array comprises the steps of collapsing the reference target array to a small cross-section, inserting it through an opening while it is in the collapsed configuration, and expanding the array to an operating configuration once it is inserted.

40. The method of claim 38 wherein the camera is an endoscope and wherein the step of moving the camera comprises the step of bending a distal portion of the endoscope.

41. The method of claim 38 wherein the camera is an endoscope having a length and wherein the step of moving the camera comprises the step of translating the endoscope along its length.

42. The method of claim 38 wherein the camera is a rigid endoscope having a length and wherein the step of moving the camera comprises the step of rotating the endoscope about an axis substantially perpendicular to its length.

43. The method of claim 38 wherein the step of holding the reference target array comprises the step of clamping or securing the reference target array to the enclosure.

44. The method of claim 38 wherein two viewing positions are used and wherein the step of determining comprises a perspective dimensional measurement process.

45. The method of claim 38 wherein the step of determining comprises a photogrammetric process.

46. The method of claim 38 for determining the three-dimensional distances between the points of each pair of any set of pairs of points in a plurality of points on an object, comprising the steps of:

(h) performing steps (a) through (g) of claim 38 for said plurality of points;

(i) determining a difference vector between the location vectors of a first pair of said set of pairs of points by subtracting the location vector of a first point of said pair from the location vector of the second point of said pair;

(j) determining the length of the difference vector by calculating the square root of the sum of the squares of the components of the difference vector; and

(k) repeating steps (i) and (j) as necessary to determine the distances between the points of all remaining pairs in said set of pairs of points.

47. The method of claim 38 for determining the three-dimensional distance between a pair of object points on an object, comprising the steps of:

(h) performing steps (a) through (g) of claim 38 for a first point of said pair of object points;

(i) transforming the three-dimensional coordinates for said first point to said reference coordinate system;

(j) performing steps (e) through (g) of claim 38 for a second point of said pair of object points;

(k) transforming the three-dimensional coordinates for said second point to said reference coordinate system; and

(l) calculating the length of the difference vector between the three-dimensional coordinates of said first point and said second point.