DEVICE FOR OPTICALLY SCANNING AND MEASURING AN ENVIRONMENT

• US 20140168370A1
• Filed: 02/14/2013
• Published: 06/19/2014
• Est. Priority Date: 12/14/2012
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Ossig, Martin, Heidemann, Rolf, Debitsch, Rasmus, Hillebrand, Gerrit
• Granted Patent: US 9,217,637 B2
• Time in Patent Office: Days
• US Class Current: 348/46
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01B 11/25 by projecting a pattern, e.g. one or more lines, moiré fringes on the object G01B11/255 takes precedence ; image analysis for depth or shape recovery G06T7/50
• 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: G01C 11/00 Photogrammetry or videogrammetry, e.g. stereogrammetry; Photographic surveying
• CPC Class Codes: G01C 11/02 Picture taking arrangements specially adapted for photogrammetry or photographic surveying, e.g. controlling overlapping of pictures
• CPC Class Codes: G06T 2200/04 involving 3D image data
• CPC Class Codes: G06T 2207/10021 Stereoscopic video; Stereoscopic image sequence
• CPC Class Codes: G06T 2207/10028 Range image; Depth image; 3D point clouds
• CPC Class Codes: G06T 2207/20016 Hierarchical, coarse-to-fine, multiscale or multiresolution image processing; Pyramid transform
• CPC Class Codes: G06T 7/33 using feature-based methods

Abstract

A method for optically scanning and measuring an environment by means of a hand-held scanner for producing 3D-scans is provided. The method including providing a hand-held scanner having at least one projector and at least one camera. At least one pattern is projected onto an object in the environment with the at least one projector. At least one camera images of the object which has the pattern projected thereon is recorded with a plurality of frames. Three-dimensional coordinates of points on the surface of the object are determined from each frame in the plurality of frames. A ring closure is determined in the plurality of frames. The determination comprising the steps of forming a frustum for each frame, comparing a last frustum of the last frame with a plurality of frusta to form an intersection, and selecting a frustum having the largest intersection.

Claims

1. A method for optically scanning and measuring an environment by means of a hand-held scanner (100) for producing 3D-scans, the method comprising:

providing a hand-held scanner having at least one projector and at least one camera;

projecting at least one pattern onto an object in the environment with the at least one projector;

recording with the at least one camera images of the object which has the pattern projected thereon with a plurality of frames;

determining three-dimensional coordinates of points on the surface of the object from each frame in the plurality of frames; and

determining a ring closure in the plurality of frames, the determination comprising the steps of;

forming a frustum for each frame;

comparing a last frustum of the last frame with a plurality of frusta to form an intersection;

selecting a frustum having the largest intersection.

2. The method according to claim 1, wherein:

each of the images includes geometric features of the object; and

the step of selecting the frustum with the largest intersection includes comparing geometric features in the last frustum of the last frame with the selected frustum.

3. The method according to claim 2, further comprising:

comparing the geometric features in the last frustum of the last frame with the selected frustum; and

identifying coinciding geometric features in the last frustum of the last frame with the selected frustum.

4. The method according to claim 3, further comprising determining a ring closure based at least in part on the degree of correspondence between geometric features in the last frustum of the last frame with the selected frustum.

5. The method according to claim 4, further comprising:

determining an error of measurement from the correspondence of the geometric features in the last frustum of the last frame with the selected frustum; and

correcting the error of measurement in the last frustum of the last frame with the selected frustum to a predetermined penetration depth.

6. The method according to claim 5, further comprising generating a quality measurement metric when the error of measurement cannot be corrected.

7. The method according to claim 1, wherein each of the plurality of frusta contains at least approximately 80% of the three-dimensional coordinates from the plurality of frames.

8. The method according to the term of claim 1 further comprising performing an averaging via adjacent frames.

9. The method according to claim 8, wherein the step of averaging includes a first averaging step wherein the frames are divided into groups and are saved within each group as a vector in a common two-dimensional data structure.

10. The method according to claim 9, wherein the step of averaging further includes a second averaging, the second averaging being performed within each group via a defined share of the vector.

11. The method according to claim 10 wherein the second averaging for each vector takes place with regard to the gray tones or colors.

12. The method according to claim 10 wherein the second averaging for each vector takes place with regard to the distances.