Calibrating method and calibration apparatus

Patent metadata

Field	Value
Publication number	US-10873739-B2
Application number	US-201816224817-A
Country	US
Kind code	B2
Filing date	Dec 19, 2018
Priority date	Dec 21, 2017
Publication date	Dec 22, 2020
Grant date	Dec 22, 2020

Abstract

A calibrating method includes controlling a laser radiator to radiate calibration laser light to an object such that a pattern is projected in a laser coordinate system with respect to the laser radiator; controlling a camera to obtain a first image of first light points of the calibration laser light projected on a surface of the object when the object is in a first position; and controlling the camera to obtain a second image of second light points of the calibration laser light projected on the surface of the object when the object is in the second position. A positional relationship between the laser coordinate system and the camera coordinate system is calculated based on the three-dimensional positions of the first light points and the three-dimensional positions of the second light points.

First claim

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A calibrating method comprising:
controlling a laser radiator to radiate calibration laser light to an object such that a pattern is projected in a laser coordinate system with respect to the laser radiator;
controlling a camera to obtain a first image of first light points of the calibration laser light projected on a surface of the object when the object is in a first position;
calculating, based on the first image, three-dimensional positions of the first light points in a camera coordinate system with respect to the camera;
changing a position of the object from the first position to a second position;
controlling the camera to obtain a second image of second light points of the calibration laser light projected on the surface of the object when the object is in the second position;
calculating, based on the second image, three-dimensional positions of the second light points in the camera coordinate system; and
calculating a positional relationship between the laser coordinate system and the camera coordinate system based on the three-dimensional positions of the first light points and the three-dimensional positions of the second light points,
wherein the step of calculating the positional relationship comprises
calculating regression lines based on the three-dimensional positions of the first light points and the second light points, and
calculating a control origin of the calibration laser light based on an intersection of the regression lines.

2. The calibrating method according to claim 1 , wherein the step of calculating the positional relationship comprises calculating, based on the regression lines, a base vector of the laser coordinate system with the control origin serving as an origin of the laser coordinate system.

3. The calibrating method according to claim 1 , wherein the pattern comprises a rectangular pattern on a surface perpendicular to a Z axis of the laser coordinate system.

4. The calibrating method according to claim 1 , further comprising, after calculating the positional relationship between the laser coordinate system and the camera coordinate system, specifying a radiation position in the camera coordinate system and radiating the calibration laser light to the radiation position to determine, based on the three-dimensional positions of the first light points and the second light points, whether the laser coordinate system and the camera coordinate system have been calibrated relative to each other normally.

5. The calibrating method according to claim 4 , further comprising, when a determination has been made that the laser coordinate system and the camera coordinate system have been calibrated relative to each other normally, calibrating the calibrated camera coordinate system of the camera and a camera coordinate system of another camera relative to each other, the camera and the another camera having overlapping fields of vision.

6. The calibrating method according to claim 1 ,
wherein the camera comprises a monocular camera, and
wherein the object comprises a plate having a surface which has markers arranged in a pattern and on which the calibration laser light is radiated.

7. The calibrating method according to claim 1 , wherein the laser radiator is configured to switchably radiate the calibration laser light and machining laser light coaxial to the calibration laser light.

8. The calibrating method according to claim 1 , wherein the predetermined pattern comprises a rectangular pattern on a surface perpendicular to a Z axis of the laser coordinate system.

9. The calibrating method according to claim 1 , wherein the pattern has a substantially constant pattern in the laser coordinate system when the object is in the first position and the second position.

10. The calibrating method according to claim 1 , further comprising, after calculating the positional relationship between the laser coordinate system and the camera coordinate system, specifying a predetermined radiation position in the camera coordinate system and radiating the calibration laser light to the predetermined radiation position to determine, based on the three-dimensional positions of the light points, whether the laser coordinate system and the camera coordinate system have been calibrated relative to each other normally.

11. A calibration apparatus comprising:
circuitry configured to:
control a laser radiator to radiate calibration laser light to an object such that a pattern is projected in a laser coordinate system with respect to the laser radiator;
control a camera to obtain a first image of first light points of the calibration laser light projected on a surface of the object when the object is in a first position;
calculate, based on the first image, three-dimensional positions of the first light points in a camera coordinate system with respect to the camera;
change a position of the object from the first position to a second position;
control the camera to obtain a second image of second light points of the calibration laser light projected on the surface of the object when the object is in the second position;
calculate, based on the second image, three-dimensional positions of the second light points in the camera coordinate system; and
calculate a positional relationship between the laser coordinate system and the camera coordinate system based on the three-dimensional positions of the first light points and the three-dimensional positions of the second light points,

wherein the circuitry is configured to calculate regression lines based on the three-dimensional positions of the first light points and the second light points, and configured to calculate a control origin of the calibration laser light based on an intersection of the regression lines.

12. The calibration apparatus according to claim 11 , wherein the circuitry is configured to calculate, based on the regression lines, a base vector of the laser coordinate system with the control origin serving as an origin of the laser coordinate system.

13. The calibration apparatus according to claim 11 , wherein the pattern comprises a rectangular pattern on a surface perpendicular to a Z axis of the laser coordinate system.

14. The calibration apparatus according to claim 11 , wherein the circuitry is configured to, after calculating the positional relationship between the laser coordinate system and the camera coordinate system, specifying a radiation position in the camera coordinate system and radiating the calibration laser light to the radiation position to determine, based on the three-dimensional positions of the first light points and the second light points, whether the laser coordinate system and the camera coordinate system have been calibrated relative to each other normally.

15. The calibration apparatus according to claim 14 , wherein the circuitry is configured to, when the circuitry has determined that the laser coordinate system and the camera coordinate system have been calibrated relative to each other normally, calibrate the calibrated camera coordinate system of the camera and a camera coordinate system of another camera relative to each other, the camera and the another camera having overlapping fields of vision.

16. The calibration apparatus according to claim 11 ,
wherein the camera comprises a monocular camera, and
wherein the object comprises a plate having a surface which has markers arranged in a pattern and on which the calibration laser light is radiated.

17. The c

Assignees

• Yaskawa Electric Corp

Inventors

• Kumagai Hiroshi
• Motoyoshi Takashi
• Fukushima Seiichiro

Classifications

• B23K26/032 Primary

  using optical means · CPC title

• B23K26/707

  for monitoring laser beam transmission optics · CPC title

• B23K26/0884

  in at least three axial directions, e.g. manipulators, robots · CPC title

• B23K26/21

  by welding · CPC title

• G06T7/80

  Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration · CPC title