Method and apparatus for three-dimensional non-contact shape sensing

• US 5,198,877 A
• Filed: 10/15/1990
• Issued: 03/30/1993
• Est. Priority Date: 10/15/1990
• Status: Expired

• Current Assignee: Northern Digital Inc. (Roper Technologies, Inc.)
• Original Assignee: Image Guided Technologies, Inc. (Stryker Corporation)
• Inventors: Schulz, Waldean A.
• Primary Examiner(s): Rosenberger, Richard A.
• Assistant Examiner(s): Pham, Hoa Q.
• Application Number:
  US07/597,505
• Time in Patent Office: 897 Days
• Field of Search: 356/375, 356/376, 356/152, 356/141, 356/1, 356/4, 250/561, 250/231 R
• US Class Current: 356/614
• CPC Class Codes: A61B 2034/2055 Optical tracking systems
• CPC Class Codes: A61B 2034/2068 using pointers, e.g. pointers having reference marks for determining coordinates of body points
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01S 17/46 Indirect determination of position data
• CPC Class Codes: G01S 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 5/163 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49
• CPC Class Codes: G01S 7/481 Constructional features, e.g. arrangements of optical elements
• CPC Class Codes: G01S 7/4813 Housing arrangements
• CPC Class Codes: G01S 7/4817 relating to scanning

Abstract

This method and apparatus optically samples numerous points on the surface of an object to remotely sense its shape utilizing two stages. The first stage employs a moveable non-contact scanner, which in normal operation sweeps a narrow beam of light across the object, illuminating a single point of the object at any given instant in time. The location of that point relative to the scanner is sensed by multiple linear photodetector arrays behind lenses in the scanner. These sense the location by measuring the relative angular parallax of the point. The second stage employs multiple fixed but widely separated photoelectronic sensors, similar to those in the scanner, to detect the locations of several light sources affixed to the scanner, thereby defining the absolute spatial positions and orientations of the scanner. Individual light sources are distinguished by time-multiplexing their on-off states. A coordinate computer calculates the absolute spatial positions where the scanner light beam is incident on the object at a given instant and continuously on a real time basis to generate a computer model of the object.

Claims

1. Optical mensuration apparatus for mapping and recording the location of points on a surface of a three-dimensional object, comprising:

a mounting structure, and object being positioned in immoveable relation to said mounting structure, and a three-dimensional coordinate system defined in fixed relation to said mounting structure;

scanning means for projecting a scanning beam onto the surface of the object to illuminate a plurality of spots on the surface of the object;

said scanning means being hand-holdable and freely moveable by hand in relation to both said mounting structure and said object and not connected mechanically or structurally to either said mounting structure and said object;

spot detector means mounted to said scanning means for detecting the positions of the illuminated spots on the surface of the object in relation to said scanning means;

position detecting means mounted on said mounting structure and remotely located from both said object and said scanning means for detecting the position of said scanning means in relation to the coordinate system; and

computing means connected to said scanning means and to said position detecting means for determining the recording the positions of said illuminated spots on the surface of the object in relation to the coordinate system by correlating the positions of said illuminated spots in relation to said scanning means with the respective positions of said scanning means in relation to the coordinate system when each respective spot is illuminated.

2. The optical mensuration apparatus of claim 1, wherein said spot detector means comprises a plurality of one-dimensional spot sensing means in spaced apart relation for sensing the position of the illuminated spot on the surface of the object.

3. The optical mensuration apparatus of claim 2, wherein each said one-dimensional spot sensing means comprises:

a linear photodetector; and

a lens positioned between said linear photodetector and said illuminated spot on the object for focusing light from said illuminated spot onto said linear photodetector.

4. The optical mensuration apparatus of claim 3, wherein said position detecting means comprises:

a plurality of pilot light source means mounted on said scanning means for projecting a plurality of pilot light rays; and

a plurality of one-dimensional pilot light sensing means in spaced apart relation remotely located from said scanning means for sensing the positions of each of said plurality of pilot light source means.

5. The optical mensuration apparatus of claim 4, wherein each said one-dimensional pilot light sensing means comprises:

a linear photodetector; and

a lens positioned between said linear photodetector and said plurality of pilot light source means for focusing light from said plurality of pilot light source means onto said linear photodetector.

6. The optical mensuration apparatus of claim 5, wherein each of said plurality of light source means is strobed off and on in a predetermined manner.

7. The optical mensuration apparatus of claim 5, wherein said scanning means comprises:

light source means for producing said scanning beam; and

scanning beam direction means for directing said scanning beam over the surface of the object.

8. The optical mensuration apparatus of claim 7, wherein said light source means for producing said scanning beam is a laser.

9. The optical mensuration apparatus of claim 7, wherein said scanning beam direction means is a rotating mirror having at least three sides.

10. The optical mensuration apparatus of claim 9, wherein each said lens of each said one-dimensional spot sensing means is a cylindrical lens.

11. The optical mensuration apparatus of claim 9, wherein each said lens of each said one-dimensional pilot light sensing means is a cylindrical lens.

12. A method for determining and mapping the location of surface points on an object in relation to a mounting structure, comprising the steps of:

defining a three-dimensional coordinate system in fixed relation to said mounting structure;

positioning said object in a fixed, spatial relation to said mounting structure;

projecting a scanning beam from a beam projector mounted in a hand-holdable and freely moveable scanning device that is not connected mechanically or structurally to either said mounting structure or the object, and moving the scanning device by hand in relation to said object in such a manner as to illuminate a plurality of spots on the surface of the object;

detecting the positions of the respective illuminated spots on the surface of the object in relation to the respective positions of the scanning device when each respective spot is illuminated;

projecting a plurality of pilot light rays from a plurality of pilot light sources positioned in fixed spatial relation to each other on said scanning device simultaneously with the steps of projecting said scanning beam and detecting the positions of the illuminated spots;

detecting the plurality of pilot rays with a plurality of detectors mounted on said mounting structure in fixed relation to said coordinate system and in fixed, spaced apart relation to each other simultaneously with the step of detecting the positions of said illuminated spots on said object in relation to said scanning device to determine the positions of the plurality of pilot light sources and the scanning device in relation to the coordinate system; and

computing the positions of the illuminated spots on the surface of the object in relation to the coordinate system by correlating the positions of said illuminated spots in relation to the scanning device with the positions of the scanning device in relation to said coordinate system.