Method for calibrating a camera-laser-unit in respect to a calibration-object

• US 7,564,571 B2
• Filed: 09/04/2004
• Issued: 07/21/2009
• Est. Priority Date: 10/17/2003
• Status: Active Grant

• Current Assignee: inos Automationssoftware GmbH
• Original Assignee: inos Automationssoftware GmbH
• Inventors: Voliotis, Konstantinos, Karanastasis, Nikolaos, Karabassi, Evaggelia-Aggeliki
• Primary Examiner(s): NGUYEN, SANG H
• Application Number:
  US10/550,107
• Publication Number:
  US 20060268285A1
• Time in Patent Office: 1,781 Days
• Field of Search: 356601-625, 356/3.01, 356/3.1, 382/154, 382/100, 382/276, 382/285, 345/419, 345/427, 700/259, 700/245, 700/247, 700251-252, 702 94- 95, 702/150, 702/152, 702/245
• US Class Current: 356/623
• CPC Class Codes: G01B 11/2504 Calibration devices

Abstract

The invention refers to a method for calibrating a camera-laser-unit (1) with respect to at least one calibration-object (12) disposed at a given position and orientation in a three-dimensional space (13). The camera-laser-unit (1) comprises a laser (4) and a camera (3), wherein the laser (4) and the camera (3) are disposed at a given distance with respect to each other. An optical axis (9) of the laser (4) and an optical axis (8) of the camera (3) subtend a given angle (α). The camera-laser-unit (1) is adapted to record the location, form and/or dimensions of a measurement-object (5). The method has the advantage that the same calibration-object (12) can be used for the calibration of the camera (3) and of the laser (4), wherein the camera (3) is first calibrated using a Tsai-algorithm and then the laser (4) is calibrated with respect to, and by making use of, the already calibrated camera (3).

Claims

1. A method for calibrating a camera-laser-unit with respect to at least one calibration-object disposed at a given position and orientation in three-dimensional space, the camera-laser-unit having at least one laser and at least one camera, wherein the laser and the camera are disposed at a given distance with respect to one another, and an optical axis of the laser and an optical axis of the camera subtend a given angle (α

), the camera-laser-unit being adapted to record a location, shape and/or dimensions of a measurement-object, the method comprising the steps of;

a) selecting a calibration-object having at least two planes disposed at a given angle (β

) with respect to each other, each plane having a given, non-coplanar calibration-pattern;

b) disposing the calibration-object at a given position and orientation in three-dimensional space with respect to the camera-laser-unit, wherein an orientation of the calibration-object is such that light emitted by the laser is visible to the camera on the at least two planes of the calibration-object;

c) determining a location of the camera with respect to the calibration-object using a Tsai algorithm;

d) calibrating the camera in three-dimensional space using the results of steps b) and c);

e) activating the laser to emit light visible on the at least two planes of the calibration-object;

f) the light on the two planes with the camera;

g) determining the laser-properties from the light recorded by the camera;

h) determining a location of the laser relative to the camera; and

i) calibrating the laser in three-dimensional space using the results of steps d) and h).

2. The method of claim 1, wherein step g) comprises the step of defining a relative position and orientation of the laser with respect to a coordinate frame associated with the calibration-object, wherein the coordinate frame has a given position and orientation in three-dimensional space.

3. The method of claim 1, wherein light emitted by the laser is visible on the two planes of the calibration-object as a line on each plane, the lines intersecting at a contact line of the two planes, wherein the laser-properties are determined from the lines recorded by the camera using a line detection algorithm.

4. The method of claim 1, wherein light emitted by the laser is visible on the two planes of the calibration-object as a line on each plane, the lines intersecting at a contact line of the two planes, wherein a laser-plane is defined by an optical axis of the laser and the lines visible on the two planes of the calibration-object object, wherein, a position and orientation of the laser-plane with respect to a coordinate frame associated with the calibration-object is defined to calibrate the laser according to determined laser-properties.

5. The method of claim 1, wherein step c) comprises the step of defining a relative position and orientation of the camera with respect to a coordinate frame associated with the calibration-object, said coordinate frame having a given position and orientation in three-dimensional space.

6. The method of claim 1, further comprising defining a transformation matrix in dependence on a relative position and orientation of the camera with respect to a coordinate frame associated with the calibration-object, a relative position and orientation of the laser with respect to the coordinate frame, and/or on internal camera parameters.

7. The method of claim 1, further comprising grasping the camera-laser-unit with an industrial robot and disposing the unit relative to the calibration-object in a given position and orientation in three-dimensional space, wherein an orientation of the camera-laser-unit is such that light emitted by the laser is visible to the camera on the at least two planes of the calibration-object.

8. A device for calibrating a camera-laser-unit with respect to at least one calibration-object disposed at a given position and orientation in three-dimensional space, the camera-laser-unit having at least one laser and at least one camera, wherein the laser and the camera are disposed at a given distance with respect to one another, and an optical axis of the laser and an optical axis of the camera subtend a given angle (α

), the camera-laser-unit being adapted to record a location, shape and/or dimensions of a measurement-object, the device comprising;

means for selecting a calibration-object having at least two planes disposed at a given angle (β

) with respect to each other, each plane having a given, non-coplanar calibration-pattern;

means for disposing the calibration-object at a given position and orientation in three-dimensional space with respect to the camera-laser-unit, wherein an orientation of the calibration-object is such that light emitted by the laser is visible to the camera on the at least two planes of the calibration-object;

means for determining a location of the camera with respect to the calibration-object using a Tsai algorithm;

means for calibrating the camera in three-dimensional space using results generated by the means for disposing the calibration object and by the means for determining a location of the camera with respect to the calibration-object;

means for activating the laser to emit light visible on the at least two planes of the calibration-object;

means for recording the light on the two planes with the camera;

means for determining the laser-properties from the light recorded by the camera;

means for determining a location of the laser relative to the camera;

and

means for calibrating the laser in three-dimensional space using results generated by the means for calibrating the camera in three-dimensional space and the means for determining the location of the laser relative to the camera.

9. The device of claim 8, wherein said non-coplanar calibration-pattern has an array of features, said calibration-object being structured and dimensioned for calibration of the camera as well as for calibration of the laser.

10. The device of claim 9, wherein said angle between said two planes of the calibration-object is a right angle.

11. The device of claim 9, wherein features of said calibration-pattern are designed as recesses or as cavities having a circular cross section.

12. The device of claim 9, wherein features of said calibration-pattern comprise prints on said two planes.