Calibration device, calibration method, and computer readable medium for visual sensor

1. A calibration device that associates at least one of position information in an image coordinate system at a first camera of a stereo camera and position information in an image coordinate system at a second camera of the stereo camera with position information in a robot coordinate system at a robot, the calibration device comprising:

a model pattern generation unit that generates a model pattern about a target mark attached to the robot;

a first parameter setting unit that sets a first parameter for detecting the target mark using the model pattern from data about an image captured by the first camera;

a second parameter setting unit that sets a second parameter for detecting the target mark using the model pattern from data about an image captured by the second camera based on the first parameter set by the first parameter setting unit;

an image capture control unit that makes the first camera and the second camera capture images of the target mark attached to the robot and moved by the robot at each of multiple destinations;

a first detection unit that detects the target mark by using a value of the first parameter from the data about the image captured by the first camera, and measures the coordinate position of the detected target mark in the image coordinate system at the first camera;

a second detection unit that detects the target mark by using a value of the second parameter from the data about the image captured by the second camera, and measures the coordinate position or the detected target mark in the image coordinate system at the second camera; and

a calibration unit that calibrates the first camera and the second camera based on the coordinate position of the target mark in the image coordinate system at the first camera measured by the first detection unit, the coordinate position of the target mark in the image coordinate system at the second camera measured by the second detection unit, and the coordinate position of the target mark in the robot coordinate system while the images of the target mark are captured by the first camera and the second camera.

2. The calibration device according to claim 1 , wherein the target mark is attached to an end of an arm of the robot, and has a three-dimensional position and a three-dimensional posture determined in advance in an end point coordinate system at the robot.

3. The calibration device according to claim 1 , wherein each of the first parameter and the second parameter includes a single numerical value, an on/off value, or a parameter having a range.

4. The calibration device according to claim 1 , wherein the second parameter initially set by the second parameter setting unit is set so as to allow detection of the target mark without fail from the image captured by the second camera that is detectable from the data about the image captured by the first camera by using the first parameter set by the first parameter setting unit.

5. The calibration device according to claim 4 , wherein, if the first parameter has a predetermined range, the second parameter setting unit determines a range for the second parameter in such a manner that the range for the second parameter has a size determined by a deviation from a center value of the first parameter with respect to a value of the second parameter as a center with which the target mark has been detected successfully from the data about the image captured by the second camera.

6. The calibration device according to claim 1 , wherein each of the first parameter and the second parameter includes parameters about a model pattern, a size, and deformation about the target mark.

7. The calibration device according to claim 4 , wherein each of the first parameter and the second parameter is a parameter applied to the model pattern about the target mark,

the first detection unit detects the target mark from the data about the image captured by the first camera by using the model pattern to which the first parameter is applied, and

the second detection unit detects the target mark from the data about the image captured by the second camera by using the model pattern to which the second parameter is applied.

8. The calibration device according to claim 1 , wherein the first parameter and the second parameter are parameters applied to the data about the image captured by the first camera and to the data about the image captured by the second camera respectively,

the first detection unit detects the target mark from image data generated by applying the first parameter to the data about the image captured by the first camera, and

the second detection unit detects the target mark from image data generated by applying the second parameter to the data about the image captured by the second camera.

9. A calibration method implemented by a calibration device that associates position information in an image coordinate system at a first camera of a stereo camera, position information in an image coordinate system at a second camera of the stereo camera, and position information in a robot coordinate system at a robot,

the calibration method comprising the following steps executed by the calibration device:

a model pattern generation step of generating a model pattern about a target mark attached to the robot;

a first parameter setting step of setting a first parameter for detecting the target mark using the model pattern from data about an image captured by the first camera;

a second parameter setting step of setting a second parameter for detecting the target mark using the model pattern from data about an image captured by the second camera based on the first parameter set by the first parameter setting step;

an image capture control step of making the first camera and the second camera capture images of the target mark attached to the robot and moved by the robot at each of multiple destinations;

a first detection step of detecting the target mark by using a value of the first parameter from the data about the image captured by the first camera, and measuring the coordinate position of the detected target mark in the image coordinate system at the first camera;

a second detection step of detecting the target mark by using a value of the second parameter from the data about the image captured by the second camera, and measuring the coordinate position of the detected target mark in the image coordinate system at the second camera; and

a calibration step of calibrating the first camera and the second camera based on the coordinate position of the target mark in the image coordinate system at the first camera measured by the first detection step, the coordinate position of the target mark in the image coordinate system at the second camera measured by the second detection step, and the coordinate position of the target mark in the robot coordinate system while the images of the target mark are captured by the first camera and the second camera.

10. A non-transitory computer-readable medium encoded with a program for causing a computer to execute: a model pattern generation step of generating a model pattern about a target mark attached to a robot;

a first parameter setting step of setting a first parameter for detecting the target mark using the model pattern from data about an image captured by the first camera;

a second parameter getting step of setting a second parameter for detecting the target mark using the model pattern from data about an image captured by the second camera based on the first parameter set by the first parameter setting step;

an image capture control step of making the first camera and the second camera capture images of the target mark attached to the robot and moved by the robot at each of multiple destinations;

a first detection step of detecting the target mark by using a value of the first parameter from the data about the image captured by the first camera, and measuring the coordinate position of the detected target mark in an image coordinate system at the first camera by using a value of the first parameter;

a second detection step of detecting the target mark by using a value of the second parameter from the data about the image captured by the second camera, and measuring the coordinate position of the detected target mark in the image coordinate system at the second camera; and

a calibration step of calibrating the first camera and the second camera based on the coordinate position of the target mark in the image coordinate system at the first camera measured by the first detection step, the coordinate position of the target mark is the image coordinate system at the second camera measured by the second detection step, and the coordinate position of the target mark in a robot coordinate system while the images of the target mark are captured by the first camera and the second camera.