CALIBRATION PLATE AND METHOD FOR CALIBRATING A 3D MEASUREMENT DEVICE

• US 20170188015A1
• Filed: 12/22/2016
• Published: 06/29/2017
• Est. Priority Date: 12/27/2015
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Heidemann, Rolf, Hillebrand, Gerrit
• Granted Patent: US 10,841,562 B2
• Time in Patent Office: Days
• CPC Class Codes: G01B 11/2504 Calibration devices
• CPC Class Codes: G01B 21/042 Calibration or calibration artifacts G01B3/30, G01B9/02072 take precedence
• CPC Class Codes: G01B 3/30 Bars, blocks, or strips in which the distance between a pair of faces is fixed, although it may be preadjustable, e.g. end measure, feeler strip
• CPC Class Codes: G06T 2200/04 involving 3D image data
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light
• CPC Class Codes: G06T 7/593 from stereo images
• CPC Class Codes: G06T 7/85 Stereo camera calibration
• 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 13/246 Calibration of cameras
• CPC Class Codes: H04N 13/257 Colour aspects

Abstract

A calibration plate and a method of calibrating a 3D measurement device is provided. The calibration plate includes a planar body having a surface. A plurality of marks are arranged on the surface. The plurality of marks being configured to be recorded by the camera and can be identified in the resulting recorded images during operation of the 3D measurement device. A mirror is positioned on the surface that reflects incident beams from the 3D measurement device.

Claims

1. A calibration plate for calibrating a 3D measurement device that emits beams and has at least one camera, the calibration plate comprising:

a planar body having a surface;

a plurality of marks arranged on the surface, the plurality of marks configured to be recorded by the camera and can be identified in the resulting recorded images during operation of the 3D measurement device; and

a mirror is positioned on the surface that reflects incident beams from the 3D measurement device.

2. The calibration plate of claim 1, further comprising a gray scale element positioned on the surface and configured to be recorded by the camera and can be identified in the resulting recorded images during operation of the 3D measurement device.

3. The calibration plate of claim 1, further comprising a color palette element positioned on the surface and configured to be recorded by the camera and can be identified in the resulting recorded images during operation of the 3D measurement device.

4. The calibration plate of claim 1, wherein at least one mark of the plurality of marks is positioned on the mirror (408).

5. The calibration plate of claim 1, further comprising an information code element positioned on the surface, wherein the information code element is a machine readable symbol.

6. The calibration plate of claim 5, wherein the information code element is configured to be recorded by the camera and can be identified in the resulting recorded images during operation of the 3D measurement device.

7. The calibration plate of claim 6, further comprising a recording device having a second camera and operable to record an image of the information code element.

8. The calibration plate of claim 6, wherein the information code element includes information relating to the calibration plate or storage location of particulars for the information.

9. The calibration plate of claim 8, wherein the information includes to the positions of each of the plurality of marks, the information code element, the gray scale element, the color palette element on the surface.

10. The calibration plate of claim 9 wherein the information includes information about any irregularities or other characteristics of the calibration plate.

11. A method for calibrating a 3D measurement device using a calibration plate, the method comprising:

positioning the calibration plate in an environment of the 3D measurement device, the 3D measurement device having at least one camera and a projector;

recording the calibration plate with the at least one camera;

determining the position and alignment of the calibration plate relative to the 3D measurement device using at least one of a plurality of marks formed on a surface of the calibration plate;

emitting with the projector at least one beam of light onto a mirror positioned on the surface;

reflecting the at least one beam of light with the mirror into the at least one camera; and

and recording with the at least one camera at least one of a gray scale element or a color palette.

12. The method of claim 11, further comprising generating at least one pattern on the calibration plate with the projector and recording images of the at least one pattern on the calibration plate with the at least one camera.

13. The method of claim 12, further comprising determining calibration parameters for the 3D measurement device from the images of the at least one pattern on the calibration plate.

14. The method of claim 13, wherein the at least one camera includes a first camera and a second camera

15. The method of claim 14, wherein:

the first camera and the second camera record images, in their respective image planes of the pattern (X) on the calibration plate;

the at least one pattern is an uncoded pattern and is generated by the projector that defines a projector plane;

the projector, the first camera, and the second camera are arranged in a triangular configuration relative to one another; and

the projector, the first camera, and second camera define different epipolar lines in the projector plane and in the two image planes with points of the pattern.

16. The method of claim 15, further comprising:

defining between the first camera, second camera and projector two stereo geometries;

generating a three-part relationships of points and epipolar lines, from which the correspondences of the images of the pattern in the two image planes can be determined; and

determining three-dimensional coordinates of the points on the surface of the calibration plate by triangulation based on the determined correspondences of the images of the at least one pattern.

17. The method of claim 11, further comprising:

recording an information code element positioned on the surface with the at least one camera; and

retrieving information relating to the calibration plate based at least in part on the information code element.