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

• US 9,693,040 B2
• Filed: 09/03/2015
• Issued: 06/27/2017
• Est. Priority Date: 09/10/2014
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Hillebrand, Gerrit, Heidemann, Rolf, Ossig, Martin
• Primary Examiner(s): Safaipour, Houshang
• Application Number:
  US14/844,691
• Publication Number:
  US 20160073091A1
• Time in Patent Office: 663 Days
• Field of Search: 358 115, 358 13, 358 11, 358 19
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• 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 11/2504 Calibration devices
• CPC Class Codes: G01B 11/2545 with one projection direction and several detection directions, e.g. stereo
• CPC Class Codes: G01B 21/042 Calibration or calibration artifacts G01B3/30, G01B9/02072 take precedence
• CPC Class Codes: G01C 11/06 by comparison of two or more pictures of the same area
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 2207/10028 Range image; Depth image; 3D point clouds
• CPC Class Codes: G06T 2207/30244 Camera pose
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light
• CPC Class Codes: G06T 7/62 of area, perimeter, diameter or volume
• CPC Class Codes: G06T 7/74 involving reference images or patches
• CPC Class Codes: H04N 13/239 using two 2D image sensors having a relative position equal to or related to the interocular distance H04N13/243 takes precedence
• CPC Class Codes: H04N 13/243 using three or more 2D image sensors
• CPC Class Codes: H04N 13/246 Calibration of cameras
• CPC Class Codes: H04N 13/254 in combination with electromagnetic radiation sources for illuminating objects
• CPC Class Codes: H04N 13/257 Colour aspects
• CPC Class Codes: H04N 13/275 from 3D object models, e.g. computer-generated stereoscopic image signals
• CPC Class Codes: H04N 23/73 by influencing the exposure time

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.

Claims

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 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;

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;

determining a second wavelength of light based at least in part on the deviation;

emitting at the second wavelength of light the light pattern onto the object; and

storing the deviation in memory.