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

• US 9,686,532 B2
• Filed: 10/02/2013
• Issued: 06/20/2017
• 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:
  US14/044,311
• Publication Number:
  US 20140028805A1
• Time in Patent Office: 1,357 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, and a processor. The projector and cameras are positioned in a non-collinear arrangement. The projector is configured to project a first pattern onto the surface. The method also includes providing the tracker which emits a beam of light onto the retroreflector. The tracker receives a reflected beam of light. The first location is measured with the tracker. The first 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 based in part on epipolar constraints of the cameras and projector.

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 first projector, and a processor, the first camera, the second camera, and the first projector coupled to the body, the first camera having a first camera perspective center at a first camera position, the second camera having a second camera perspective center at a second camera position, and the first projector having a first projector perspective center at a first projector position, respectively, in a scanner frame of reference, the first projector position being non-collinear with respect to the first camera position and the second camera position, the first projector configured to produce a first projector pattern of light within the projector and to project the first projector pattern onto the surface as a first surface pattern, the first projector pattern of light being a pattern of light having uniformly spaced elements in each of two dimensions of two-dimensional space, the scanner further having a first retroreflector coupled to the body;

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, each of the first location and the first orientation being defined by three degrees of freedom;

locking 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, a first angle, and a second angle, the first distance being a distance from the tracker to the retroreflector, the first distance measured with a distance meter, a first angle measured with a first angle measuring device, and a second angle measured with a second angle measuring device;

measuring with the tracker the first orientation;

projecting onto the surface the first surface pattern;

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

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

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 location, the first orientation, the first projector pattern, the first image, the second image, the first camera position, the second camera position, and the first projector position, the determining based at least in part on the use of epipolar constraints among the first camera, the second camera, and the first projector; and

storing 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;

locking 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;

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, the fourth image, and the first projector position.

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 shared 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 with respect 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.