System and method of acquiring three-dimensional coordinates using multiple coordinate measurment devices

• US 9,967,545 B2
• Filed: 06/13/2017
• Issued: 05/08/2018
• Est. Priority Date: 04/15/2011
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Tohme, Yazid
• Primary Examiner(s): PHAM, NAM D
• Application Number:
  US15/621,368
• Publication Number:
  US 20170280132A1
• Time in Patent Office: 329 Days
• 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: G01B 11/2513 with several lines being projected in more than one direction, e.g. grids, patterns
• CPC Class Codes: G01B 11/2518 Projection by scanning of the object
• CPC Class Codes: G01B 11/2545 with one projection direction and several detection directions, e.g. stereo
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/66 Tracking systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4808 Evaluating distance, position or velocity data
• CPC Class Codes: G01S 7/4813 Housing arrangements
• CPC Class Codes: G01S 7/4818 using optical fibres
• CPC Class Codes: G01S 7/491 Details of non-pulse systems
• CPC Class Codes: H04N 13/204 using stereoscopic image cameras stereoscopic photography G03B35/00
• CPC Class Codes: H04N 13/246 Calibration of cameras
• CPC Class Codes: H04N 13/25 using two or more image sensors with different characteristics other than in their location or field of view, e.g. having different resolutions or colour pickup characteristics; using image signals from one sensor to control the characteristics of another sensor
• CPC Class Codes: H04N 13/254 in combination with electromagnetic radiation sources for illuminating objects

Abstract

A method is provided of determining three-dimensional coordinates of an object surface with a laser tracker and structured light scanner. The method includes providing the scanner having a body, a pair of cameras, a projector, a retroreflector and a processor. The projector and cameras are positioned in a non-collinear arrangement. The projector is configured to project a pattern onto the surface. The method also includes providing the tracker which emits a beam of light onto the retroreflector and receives a reflected beam of light. The first location and orientation is measured with the tracker. The first surface pattern is projected onto the surface. A pair of images of the surface pattern is acquired with cameras. The processor determines the 3D coordinates of a first plurality of points in the tracker frame of reference.

Claims

1. A method of determining three-dimensional (3D) coordinates of an object surface with a six degree-of-freedom (DOF) laser tracker and a portable structured light scanner, the method comprising:

providing the scanner having a body, a first camera, a second camera, a projector, a first retroreflector, and a processor, the first camera, the second camera, first retroreflector and the projector coupled to the body, the projector position being non-collinear with respect to the first camera and the second camera, the projector projecting in operation a first surface pattern of light onto the surface, the first surface pattern of light having uniformly spaced elements in each of two dimensions of two-dimensional space;

providing the tracker having a tracker frame of reference, the scanner having a first pose in the tracker frame of reference, the first pose including a first location and a first orientation, the first location and the first orientation each being defined by three degrees of freedom;

projecting an emitted beam of light from the tracker onto the first retroreflector;

receiving by the tracker a reflected portion of the emitted beam of light;

measuring with the tracker the first location, the location based at least in part on a first distance measured with a distance meter, the first distance being a distance from the tracker to the retroreflector;

measuring with the tracker the first orientation based at least in part on the received reflected portion of the emitted beam of light;

projecting onto the surface the first surface pattern of light with the projector;

acquiring a first image of the first surface pattern of light with the first camera;

acquiring a second image of the first surface pattern of light with the second camera;

determining with the processor the 3D coordinates of a first plurality of points in the tracker frame of reference based at least in part on the first orientation, the first image, the second image, and the use of epipolar constraints among the first camera, the second camera, and the projector; and

storing with the processor the 3D coordinates.

2. The method of claim 1, further comprising:

moving the scanner to a second pose that includes a second location and a second orientation;

projecting the emitted beam of light from the tracker onto the first retroreflector;

receiving by the tracker the reflected portion of the emitted beam of light;

measuring with the tracker the second location;

measuring with the tracker the second orientation;

projecting onto the surface a second surface pattern of light with the projector;

imaging the second surface pattern with the first camera to obtain a third image;

imaging the second surface pattern with the second camera to obtain a fourth image; and

determining with the processor the 3D coordinates of a second plurality of points in the tracker frame of reference based at least in part on the second location, the second orientation, the third image, and the fourth image.

3. The method of claim 1, further comprising synchronizing acquiring of the first image, the acquiring of the second image, the acquiring of the first location, and the acquiring of the first orientation, the synchronizing based at least in part on a trigger signal transmitted between by the scanner and the tracker.

4. The method of claim 1, wherein, in the step of providing the scanner, the scanner further has a second retroreflector coupled the body, the second retroreflector being oriented in a different direction than the first retroreflector.

5. The method of claim 1, wherein, in the step of providing the scanner, the first retroreflector is configured to be rotated relative to the body.

6. The method of claim 5, wherein, in the step of providing the scanner, the first retroreflector is further configured to be rotated within a magnetic nest.

7. The method of claim 5, wherein, in the step of providing the scanner, the first retroreflector is a spherically mounted retroreflector.

8. The method of claim 1, wherein, in the step of projecting the first surface pattern onto the surface, the first surface pattern is a first pattern of dots.

9. The method of claim 1, wherein the first surface pattern of light includes at least three non-collinear pattern elements.

10. A method of determining three-dimensional (3D) coordinates of an object surface with a six degree-of-freedom (DOF) laser tracker and a portable structured light scanner, the method comprising:

emitting a first beam of light with the laser tracker onto a first retroreflector, the first retroreflector being coupled to the portable structured light scanner;

receiving with the laser tracker a reflected portion of the first beam of light that is reflected by the first retroreflector;

measuring with the laser tracker a first position and first orientation of the portable structured light scanner based at least in part on receiving the reflected portion;

projecting with a projector coupled to the portable structured light scanner a first pattern of structured light, the portable structured light scanner being arranged in a first pose relative to the laser tracker in a first position and first orientation, the first pattern of structured light having uniformly spaced elements in each of two dimensions of two-dimensional space;

acquiring with a first camera coupled to the portable structured light scanner a first image of the first pattern of structured light;

acquiring with a second camera coupled to the portable structured light scanner a second image of the first pattern of structured light, the projector, first camera and second camera being arranged in a predetermined geometric arrangement;

determining with a processor the 3D coordinates of at least one point on a surface in a laser tracker frame of reference based at least in part on the first position, the first orientation, the first image, the second image and the predetermined geometric arrangement; and

storing with the processor the 3D coordinates.

11. The method of claim 10, further comprising:

moving the portable structured light scanner to a second pose that includes a second location and a second orientation;

emitting a second beam of light from the laser tracker onto the first retroreflector;

receiving with the laser tracker a second reflected portion of the second beam of light reflected by the first retroreflector;

measuring with the laser tracker the second location and second orientation;

projecting with the portable structured light scanner a second pattern of structured light with the first projector;

acquiring a third image of the second pattern of structured light with the first camera;

acquiring a fourth image of the second pattern of structured light with the second camera; and

determining with the processor the 3D coordinates of at least one second point in the tracker frame of reference based at least in part on the second location, the second orientation, the third image, and the fourth image.

12. The method of claim 10, further comprising synchronizing acquiring of the first image, the acquiring of the second image, the acquiring of the first location, and the acquiring of the first orientation, the synchronizing based at least in part on a trigger signal transmitted between by the scanner and the tracker.

13. The method of claim 10, further comprising rotating the first retroreflector relative to the body prior to emitting the beam of light.

14. The method of claim 13, wherein, the first retroreflector is rotatably coupled to a body of the portable structured light scanner by a magnetic nest.

15. The method of claim 14, wherein the first retroreflector is a spherically mounted retroreflector.

16. The method of claim 10, the first pattern of structured lights includes a first pattern of dots.

17. The method of claim 10, wherein the first pattern of structured light includes at least three non-collinear pattern elements.

18. The method of claim 10, wherein the projector includes a light source that defines a projector plane.

19. The method of claim 18, further comprising generating the first pattern of structured light on the projector plane.