Method for optically measuring three-dimensional coordinates and calibration of a three-dimensional measuring device

Patent metadata

Field	Value
Publication number	US-9693040-B2
Application number	US-201514844691-A
Country	US
Kind code	B2
Filing date	Sep 3, 2015
Priority date	Sep 10, 2014
Publication date	Jun 27, 2017
Grant date	Jun 27, 2017

Abstract

A method for scanning and obtaining three-dimensional (3D)l coordinates is provided. The method includes providing a 3D measuring device having a projector, a first camera and a second camera. The method records images of a light pattern emitted by the projector onto an object. A deviation in a measured parameter from an expected parameter is determined. The calibration of the 3D measuring device may be changed when the deviation is outside of a predetermined threshold.

First claim

The invention claimed is:

1. Method for optically scanning and measuring an environment, the method comprising:
providing a three-dimensional (3D) measurement device having a first camera, a second camera and a projector, the 3D measurement device further having a control and evaluation device operably coupled to the at least one camera and the projector, the control and evaluation device having memory;
emitting a light pattern onto an object with the projector; recording a first image of the light pattern with the first camera at a first time;
recording a second image of the light pattern with the second camera at the first time;
producing a 3D scan of the object based at least in part on the first image and the second image;
selecting at least one point in the first image and the second image;
determining a first 3D coordinates of the at least one point in the first image based at least in part on a first set of calibration parameters;
determining a second 3D coordinates of the at least one point in the second image based at least in part on the first set of calibration parameters;
determining a deviation based at least in part on the first 3D coordinates and the second 3D coordinates;
determining a second set of calibration parameters based at least in part on the deviation;
comparing the deviation to a predetermined threshold and replacing the first set calibration parameters with the second set of calibration parameters when the deviation exceeds the predetermined threshold; and
storing the second set of calibration parameters in memory.

2. The method of claim 1 wherein the step of determining the deviation includes determining a difference in position between the first 3D coordinates and the second 3D coordinates.

3. The method of claim 1 wherein:
the projector includes a projector plane;
the first camera includes a first image plane;
the second camera includes a second image plane;
the at least one point is selected to have correspondences on at least two planes selected from the first image plane, the second image plane and the projector plane; and
the step of determining the deviation includes determining that the position of the at least one point on one of the at least two planes is different than an expected position.

4. The method of claim 3 wherein the determined deviation is inserted into a field of error.

5. The method according to claim 4 wherein the step of determining the second calibration parameters is based on the type of error field and the size of the deviations.

6. The method of claim 1 wherein the at least one point includes a first point and a second point, the first point and second point being selected to be positioned at different distances from the 3D measuring device.

7. The method of claim 1 wherein the projector, the first camera and the second camera are positioned in a triangular arrangement.

8. A method for optically scanning and measuring an environment, the method comprising:
providing a three-dimensional (3D) measurement device having a first camera, a second camera and a projector, the 3D measurement device further having a control and evaluation device operably coupled to the at least one camera and the projector, the control and evaluation device having memory the 3D measuring device further includes a two-dimensional (2D) camera;
emitting a light pattern onto an object with the projector;
recording a first image of the light pattern with the first camera at a first time;
recording a second image of the light pattern with the second camera at the first time;
producing a 3D scan of the object based at least in part on the first image and the second image;
selecting at least one point in the first image and the second image, the at least one point corresponds to a feature on the object;
determining a first 3D coordinates of the at least one point in the first image based at least in part on a first set of calibration parameters;
determining a second 3D coordinates of the at least on point in the second image based at least in part on the first set of calibration parameters;
determining a deviation based at least in part on the first 3D coordinates and the second 3D coordinates;
determining a second set of calibration parameters based at least in part on the deviation; and
storing the second set of calibration parameters in memory.

9. The method of claim 8 further comprising recording a third image with the 2D camera, the third image including the feature.

10. The method of claim 9 wherein the step of determining the deviation includes comparing the first image of the at least one point and the second image of the at least one point with the feature in the third image.

11. The method of claim 10 wherein the first image, the second image and the third image are recorded simultaneously.

12. The method of claim 10 wherein the third image is acquired at second time, the second time being different than the first time.

13. The method of claim 11 wherein the 3D measuring device further includes a filter arranged to block a wavelength of light, the projector being configured to emit the light pattern at the wavelength of light.

14. The method of claim 12 wherein the step of emitting the light pattern is a pulsed pattern, the pattern being emitted during the first time and not emitted during the second time.

15. The method of claim 13 wherein the wavelength of light is an infrared wavelength or an ultraviolet wavelength.

16. A method for optically scanning and measuring an environment, the method comprising:
providing a three-dimensional (3D) measurement device having a first camera, a second camera and a projector, the 3D measurement device further having a control and evaluation device operably coupled to the at least one camera and the projector, the control and evaluation device having memory, wherein the projector further includes a diffractive optical element;
emitting at a first wavelength a light pattern onto an object with the projector;
recording a first image of the light pattern with the first camera at a first time;
recording a second image of the light pattern with the second camera at the first time;
producing a 3D scan of the object based at least in part on the first image and the second image;
selecting a first point in the center of the light pattern, the first point being in the first image and the second image, wherein the first point is positioned at a zeroth order of diffraction and the second point is located at a position of a higher order of the diffraction;
selecting a second point in the light pattern, the second point being positioned away from the second of the light pattern;
determining a deviation in the first wavelength based on the first point and the second point; and
storing the deviation in memory.

17. The method of claim 16 wherein the projector, the first camera and the second camera are positioned in a triangular arrangement.

18. A method for optically scanning and measuring an environment, the method comprising:
providing a three-dimensional (3D) measurement device having a first camera, a second camera and a projector, the 3D measurement device further having a control and evaluation device operably coupled to the at least one camera and the projector, the control and evaluation device having memory;
emitting at a first wavelength a light pattern onto an object with the projector;
recording a first image of the light pattern with the first camera at a first time;
producing a 3D scan of the object based at least in part

Assignees

• Faro Tech Inc

Inventors

• Hillebrand Gerrit
• Heidemann Rolf
• Ossig Martin

Classifications

• H04N23/73

  by influencing the exposure time · CPC title

• G01B11/002 Primary

  for measuring two or more coordinates · CPC title

• H04N13/254

  in combination with electromagnetic radiation sources for illuminating objects · CPC title

• H04N13/275

  from three-dimensional [3D] object models, e.g. computer-generated stereoscopic image signals · CPC title

• H04N13/246

  Calibration of cameras · CPC title