Method and device for determining three-dimensional coordinates of an object

Patent metadata

Field	Value
Publication number	US-10041788-B2
Application number	US-201314440642-A
Country	US
Kind code	B2
Filing date	Oct 31, 2013
Priority date	Nov 5, 2012
Publication date	Aug 7, 2018
Grant date	Aug 7, 2018

Abstract

Some embodiments of the invention relate to an optical measuring device for determining 3D coordinates of an object. The optical measuring device may include a projector device for illuminating the object with at least one predefined pattern; at least one PSA camera for capturing a 2D image of the pattern as reflected from the object; computing means for measuring a sequence of brightness values of at least one 2D image point from the 2D images, and calculating a 3D coordinate of an object point which is correlated with the measured sequence of brightness values of the 2D image point. The optical measuring device may also include a TOF camera for capturing at least one range image of the object, the range image including distance information of the object for the dissolution of ambiguity in calculating the 3D coordinate.

First claim

What is claimed is:

1. Method for determining 3D coordinates of an object by an optical measuring device, the method comprising:
a structured-light 3D measurement of 3D coordinates of the object with:
illuminating the object with a temporal sequence of varying predefined patterns;
capturing a temporal sequence of 2D images of the sequence of varying predefined patterns as reflected from the object;
measuring a temporal sequence of brightness values of at least one 2D image point from the temporal sequence of 2D images;
capturing with a time-of-flight (TOF) camera at least one range image of the object, the range image comprising distance information of a plurality of points of the object; and
calculating the 3D coordinates of the object point which is correlated with the measured temporal sequence of brightness values of the 2D image point according to a distortion of the 2D images of the reflected sequence of varying predefined patterns relative to a reference of the illuminating sequence of varying predefined patterns, which distortion is caused by the 3D shape representation of the object;
considering the range image in the calculation of the 3D coordinate; and
using the range image for dissolving an ambiguity in the calculation of the 3D coordinate of the structured-light 3D measurement.

2. The method according to claim 1 , wherein the method further comprises:
determining, whether a temporal sequence of brightness values of a 2D image point comprises the ambiguity; and
in case of the ambiguity, using the distance information of at least one point of the plurality of points of the object for dissolving the ambiguity.

3. The method according to claim 1 , further comprising:
capturing an amplitude image of the object, the amplitude image comprising a brightness information for each of the plurality of points, wherein for dissolving the ambiguity in the calculation of the 3D coordinate the range image and the amplitude image are combined to a 3D image of the object.

4. The method according to claim 1 , further comprising:
determining, whether a temporal sequence of brightness values of a particular 2D image point comprises the ambiguity; and
in case of the ambiguity:
linking the particular 2D image point with a particular 3D image point of a particular correlated object point in the range image; and
extracting a 3D coordinate of the particular correlated object point from the linked particular 3D image point of the range image to resolve the ambiguity.

5. The method according to claim 1 , further comprising wherein:
capturing a temporal sequence of 2D images of the patterns from a first point of view;
capturing the same temporal sequence of 2D images of the patterns simultaneously from a second point of view;
measuring a temporal sequence of brightness values of a 2D image point from 2D images from the first point of view;
measuring a temporal sequence of brightness values of a 2D image point from 2D images from the second point of view;
determining whether the temporal sequence of brightness values from the first point of view is similar to the temporal sequence of brightness values from the second point of view; and
in case of similarity, calculating a 3D coordinate of a correlated object point from the measured temporal sequences of brightness values of the 2D image point; or
in case of lacking similarity:
linking the particular 2D image point for which the temporal sequences of brightness values from the first and second point of view lack similarity with a particular 3D image point of a particular correlated object point, and
extracting a 3D coordinate of the particular correlated object point from the linked particular 3D image point.

6. The method according to claim 5 , further comprising:
measuring a temporal sequence of brightness values for a plurality of 2D image points from 2D images from the first and second point of view;
determining for at least one of the plurality of 2D image points, whether the temporal sequence of brightness values from the first point of view is similar to the temporal sequence of brightness values from the second point of view;
in case of similarity, calculating at least one 3D coordinate of a correlated object point from the temporal measured sequence of brightness values for at least one of the plurality of 2D image points;
in case of lacking similarity:
linking at least one particular 2D image point for which the temporal sequences of brightness values from the first and second point of view of lacking similarity with a particular 3D image point of a particular correlated object point, and
extracting at least one 3D coordinate of the particular correlated object point from the linked particular 3D image point; and

determining a 3D shape representation of the object from the plurality of 3D coordinates of correlated object points and of particular correlated object point.

7. The method according to claim 6 , further comprising:
repeating the steps of claim 6 ; and
displaying:
the latest determined 3D shape representation of the object; and/or

the latest 3D image representation of the object.

8. The method according to claim 1 , wherein: a triangulation of the 3D coordinate of the correlated object point by the predefined patterns is comprised in the structured-light 3D measurement.

9. The method according to claim 8 , wherein: the triangulation comprises a device distance and a illumination angle enclosed by the projected and the captured patterns.

10. An optical measuring device for determining 3D coordinates of an object, the optical measuring device comprising:
a projector device for illuminating the object with a temporal sequence of varying predefined patterns;
at least one photosensor array (PSA) camera for capturing a temporal sequence of 2D images of the temporal sequence of varying predefined patterns as reflected from the object;
a time-of-flight (TOF) camera for capturing at least one range image of the object, the range image including distance information of a plurality of range image points of the object; and
a computing device for:
measuring a temporal sequence of brightness values of at least one 2D image point from the temporal sequence of 2D images; and
calculating a 3D coordinate of an object point which is correlated with the temporal sequence of measured brightness value of the 2D image point by a structured-light 3D measurement of 3D coordinates of the object according to a distortion of the 2D images of the reflected sequence of varying predefined patterns relative to a reference of the predefined patterns, which distortion to the predefined patterns is caused by the 3D shape representation of the object, with a triangulation of the 3D coordinate of the correlated object point in the structured-light 3D measurement; and
using range image is used for dissolving an ambiguity in the calculating of the 3D coordinate by the structured-light 3D measurement.

11. The optical measuring device according to claim 10 , wherein:
the projector device, the PSA camera and the TOF camera are rigidly mounted in a housing of the optical measuring device.

12. The optical measuring device according to claim 10 , wherein:
the computing device is configured for determining whether a temporal sequence of brightness values of a particular 2D image point comprises an ambiguity;
in case of the ambiguity:
the computing device is configured for linking the particular 2D image point with a particular 3D image point of a particular correlated object point; and
the computing device is configured for extracting a 3D coordinate of the particular correlated object point from

Assignees

• Hexagon Technology Ct Gmbh

Inventors

• Pettersson Bo
• Siercks Knut
• Voit Eugen
• Hinderling Jürg
• Schneider Klaus
• Zebhauser Benedikt

Classifications

• G01S17/894

  Three-dimensional [3D] imaging with simultaneous measurement of time-of-flight at a two-dimensional [2D] array of receiver pixels, e.g. time-of-flight cameras or flash lidar · CPC title

• G01B11/2545 Primary

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

• G01C15/00

  Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00 · CPC title

• G01B11/002

  for measuring two or more coordinates · CPC title

• G01C15/002

  Active optical surveying means (optical plumbing G01C15/105) · CPC title