Triangulation scanner having flat geometry and projecting uncoded spots

Patent metadata

Field	Value
Publication number	US-11022692-B2
Application number	US-201715784437-A
Country	US
Kind code	B2
Filing date	Oct 16, 2017
Priority date	May 5, 2017
Publication date	Jun 1, 2021
Grant date	Jun 1, 2021

Abstract

A projector projects an uncoded pattern of uncoded spots onto an object, which is imaged by a first camera and a second camera, 3D coordinates of the spots on the object being determined by a processor based on triangulation, the processor further determining correspondence among the projected and imaged spots based at least in part on a nearness of intersection of lines drawn from the projector and image spots through their respective perspective centers.

First claim

What is claimed is:

1. A method comprising:
providing in a scanner including a body, a projector, a first camera, a second camera, and a processing system, the projector;
at a first time, projecting from a reference plane of the projector an uncoded pattern of uncoded spots, the uncoded spots having no internal structure, the uncoded spots being projected onto an object;
at the first time, capturing the uncoded spots on the object with the first camera to obtain a first image;
at the first time, capturing the uncoded spots on the object with the second camera to obtain a second image;
with the processing system, determining three-dimensional (3D) coordinates of a first point on the object based on the uncoded spots in the reference plane, the uncoded spots in the first image and the uncoded spots in the second image, the determining not based on images obtained at times before or after the first time; and
storing the determined 3D coordinates of the first point on the object.

2. The method of claim 1 wherein:
the processing system further determines the 3D coordinates of the first point based on matching of a first uncoded spot from the first image with a second uncoded spot from the second image and a third uncoded spot from the reference plane, the first spot, the second spot, and the third spot being selected based at least in part on a nearness of intersection of a first line, a second line, and a third line, the first line being a line drawn from the selected first spot through a perspective center of the first camera, the second line being a line drawn from the selected second spot through a perspective center of the second camera, the third line being a line drawn from the selected third spot through a perspective center of the projector.

3. The method of claim 1 further comprising:
with the processing system, determining 3D coordinates of a first set of points including the first point on the object and additional points on the object, the 3D coordinates of the additional points based on the uncoded spots in the reference plane, the uncoded spots in the first image, and the uncoded spots in the second image, wherein the determining is not based on images obtained at times before or after the first time.

4. The method of claim 3 further comprising:
at a second time, projecting from the reference plane the uncoded pattern of uncoded spots, the uncoded spots being projected onto the object;
at the second time, capturing the uncoded spots on the object with the first camera to obtain a third image;
at the second time, capturing the uncoded spots on the object with the second camera to obtain a fourth image; and
with the processing system, determining 3D coordinates of a second set of points on the object based on the uncoded spots in the reference plane, the uncoded spots in the third image, and the uncoded spots in the fourth image, the determining not based on images obtained at times before or after the second time.

5. The method of claim 4 further comprising:
with the processing system, registering the first set of points and the second set of points in a common frame of reference based at least in part on the determined 3D coordinates of the first set of points and the determined 3D coordinates of the second set of points.

6. The method of claim 5 further comprising:
coupling a retroreflector to the scanner system;
with a laser tracker, measuring 3D coordinates of the retroreflector at the first time and the second time; and
with the processing system, registering the first set of points and the second set of points in a common frame of reference based at least in part on the measured 3D coordinates of the retroreflector at the first time and the measured 3D coordinates of the retroreflector at the second time.

7. The method of claim 4 further comprising:
determining with the processing system a change in pose of the scanner based at least in part on the 3D coordinates of the first set of points and the 3D coordinates of the second set of points.

8. The method of claim 7 further comprising:
coupling a retroreflector to the scanner;
measuring 3D coordinates of a retroreflector with a laser tracker at the first time and the second time; and
with the processing system, determining the change in pose of the scanner further based on the measured 3D coordinates of the retroreflector at the first time and the second time.

9. The method of claim 8 further comprising:
measuring 3D coordinates of a reference artifact with the scanner; and
with the processing system, determining the change in pose of the scanner from the first pose to the second pose further based on the measured 3D coordinates of the reference artifact.

10. The method of claim 7 further comprising:
coupling a robotic mechanism to the scanner system;
with the processing system, determining a desired change in pose of the robotic mechanism based at least in part on the determined change in pose from the first pose to the second pose; and
adjusting the robotic mechanism to obtain the desired change in pose.

11. The method of claim 10 further comprising:
changing a speed or a direction of the robotic mechanism to avoid contact with a human operator.

12. The method of claim 10 further comprising:
coupling a retroreflector to the scanner;
at the first time, measuring first 3D coordinates of the retroreflector with a laser tracker;
at the second time, measuring second 3D coordinates of the retroreflector with the laser tracker; and
with the processing system, determining a desired change in pose of the robotic mechanism further based on the measured first 3D coordinates of the retroreflector and the measured second 3D coordinates of the retroreflector.

13. The method of claim 4 further comprising:
coupling a line scanner device to the scanner, the line scanner device having a line projector and a two-dimensional (2D) line-scanner camera;
at the first time, projecting a first line of light from the line projector onto the object and capturing with the line-scanner camera a first line-scanner image of the first line of light on the object;
at the second time, projecting a second line of light from the line projector onto the object and capturing with the line-scanner camera a second line-scanner image of the second line of light on the object;
with the processing system, registering the first line of light on the object to the second line of light on the object based at least in part on the 3D coordinates of the first set of points, the 3D coordinates of the second set of points, the projected first line of light, the projected second line of light, the captured first line-scanner image, and the captured second line-scanner image.

14. The method of claim 1 further comprising:
with the projector, projecting light from a light source to a pattern generator, the pattern generator selected from the group consisting of: a diffractive optical element (DOE), a transparent or reflective slide having a pattern, a digital micromirror device (DMD), and a lenslet array.

15. The method of claim 1 further comprising:
with a beam-steering mechanism, steering the uncoded pattern of uncoded spots, the beam-steering mechanism including a solid-state deflector or a reflective element, wherein the reflective element is actuated by a mechanism selected from the group consisting of: a piezo actuator, a microelectromechanical system (MEMS) device, and a magnetic coil.

16. The set of claim 5 wherein:
the first set of points is obtained at the first time for the object on a moving conveyor be

Assignees

• Faro Tech Inc

Inventors

• Heidemann Rolf
• Brenner Mark
• Raab Simon

Classifications

• G01B11/2545

  with one projection direction and several detection directions, e.g. stereo · CPC title

• G01B11/2513

  with several lines being projected in more than one direction, e.g. grids, patterns · CPC title

• G01S17/89

  for mapping or imaging · CPC title

• G01S17/87

  Combinations of systems using electromagnetic waves other than radio waves · CPC title

• G06T7/521

  from laser ranging, e.g. using interferometry; from the projection of structured light · CPC title