Calibration device, calibration method, optical device, image-capturing device, projection device, measuring system, and measuring method

Patent metadata

Field	Value
Publication number	US-10127687-B2
Application number	US-201715590175-A
Country	US
Kind code	B2
Filing date	May 9, 2017
Priority date	Nov 13, 2014
Publication date	Nov 13, 2018
Grant date	Nov 13, 2018

Abstract

A calibration device for an optical device including a two-dimensional image conversion element having a plurality of pixels and an optical system that forms an image-formation relationship between the image conversion element and the three-dimensional world coordinate space. The calibration device includes: a calibration-data acquisition unit that acquires calibration data representing the correspondence between two-dimensional pixel coordinates in the image conversion element and three-dimensional world coordinates in the world coordinate space; and a parameter calculating unit that calculates parameters of a camera model by applying, to the calibration data acquired by the calibration-data acquisition unit, a camera model in which two coordinate values of the three-dimensional world coordinates are expressed as functions of the other one coordinate value of the world coordinates and the two coordinate values of the two-dimensional pixel coordinates.

First claim

The invention claimed is:

1. A calibration device for an optical device provided with a two-dimensional image conversion element having a plurality of pixels, and an optical system that forms an image-formation relationship between the image conversion element and the three-dimensional world coordinate space, the calibration device comprising:
a calibration-data acquisition unit that acquires calibration data representing the correspondence between two-dimensional pixel coordinates in the image conversion element and three-dimensional world coordinates in the world coordinate space; and
a parameter calculating unit that calculates parameters of a camera model by applying, to the calibration data acquired by the calibration-data acquisition unit, a camera model that expresses two coordinate values of the three-dimensional world coordinates as functions of the other one coordinate value of the world coordinates and the two coordinate values of the two-dimensional pixel coordinates.

2. The calibration device according to claim 1 , wherein the camera model expresses a straight line in the world coordinate space by a linear sum of multiple two-dimensional vector functions whose elements are functions of the other one coordinate value of the world coordinates and the two coordinate values of the two-dimensional pixel coordinates.

3. The calibration device according to claim 2 , wherein the camera model is expressed by an expression in which the respective coefficients in a linear image-forming model representing the image-formation relationship between the two pixel coordinate values of a point on a two-dimensional pixel coordinate plane and two world coordinate values of a point on a plane that is made to be optically conjugate with the pixel coordinate plane by the optical system are replaced with a linear equation of the other one world coordinate.

4. The calibration device according to claim 1 , wherein the calibration-data acquisition unit acquires a plurality of pieces of calibration data representing the correspondence between the three coordinate values of a point on each of two planes in the world coordinate space and the two coordinate values of the two-dimensional pixel coordinates corresponding to each point.

5. The calibration device according to claim 1 , wherein the parameter calculating unit applies the camera model to a plurality of pieces of calibration data representing the correspondence between the three coordinate values of a point on each of two planes in the world coordinate space and the two coordinate values of the two-dimensional pixel coordinates corresponding to each point.

6. The calibration device according to claim 1 , wherein the calibration-data acquisition unit acquires a plurality of pieces of calibration data representing the correspondence between the two coordinate values of the two-dimensional pixel coordinates and the slope and intercept of a straight line in the world coordinates.

7. The calibration device according to claim 1 , wherein the parameter calculating unit applies the camera model to the calibration data by a linear least-squares method.

8. The calibration device according to claim 1 , wherein the parameter calculating unit obtains one or more rotation angles with which the residual error of the camera model is minimum by applying the camera model to calibration data, in the calibration data acquired by the calibration-data acquisition unit, in which the three-dimensional world coordinates have been converted into world coordinates obtained by being rotated by one or more of three rotation angles representing the rotation of the world coordinates.

9. The calibration device according to claim 1 , wherein the parameter calculating unit obtains one or more translation components with which the residual error of the camera model is minimum by applying the camera model to calibration data, in the calibration data acquired by the calibration-data acquisition unit, in which the three-dimensional world coordinates have been converted into world coordinates obtained by being translated by one or more of three translation components representing the translation of the world coordinates.

10. The calibration device according to claim 1 , wherein
the optical device includes a plurality of image conversion elements and an optical system that forms the image-formation relationship between the image conversion elements and the three-dimensional world coordinate space,
the calibration-data acquisition unit acquires calibration data for the respective image conversion elements and the optical system, and
the parameter calculating unit applies, to the calibration data for the respective image conversion elements and the optical system, a camera model expressed as a function of the two-dimensional pixel coordinates of the respective image conversion elements.

11. The calibration device according to claim 1 , wherein
the optical device is an image-acquisition device,
the image conversion element is an image-acquisition element, and
the optical system is an image-acquisition optical system.

12. The calibration device according to claim 1 , wherein
the optical device is a projection device,
the image conversion element is an image forming element, and
the optical system is a projection optical system.

13. A calibration method for an optical device provided with a two-dimensional image conversion element having a plurality of pixels, and an optical system that forms an image-formation relationship between the image conversion element and the three-dimensional world coordinate space, the calibration method comprising:
a step of acquiring calibration data representing the correspondence between two-dimensional pixel coordinates in the image conversion element and three-dimensional world coordinates in the world coordinate space; and
a step of calculating parameters of a camera model by applying, to the acquired calibration data, a camera model that expresses two coordinate values of the three-dimensional world coordinates as functions of the other one coordinate value of the world coordinates and the two coordinate values of the two-dimensional pixel coordinates.

14. The calibration method according to claim 13 , wherein the camera model expresses a straight line in the world coordinate space by a linear sum of multiple two-dimensional vector functions whose elements are functions of the other one coordinate value of the world coordinates and the two coordinate values of the two-dimensional pixel coordinates.

15. The calibration method according to claim 14 , wherein the camera model is expressed by an expression in which the respective coefficients in a linear image-forming model representing the image-formation relationship between the two pixel coordinate values of a point on a two-dimensional pixel coordinate plane and two world coordinate values of a point on a plane that is made to be optically conjugate with the pixel coordinate plane by the optical system are replaced with a linear equation of the other one world coordinate.

16. The calibration method according to claim 13 , wherein, in the step of acquiring calibration data, a plurality of pieces of calibration data representing the correspondence between two coordinate values on two planes in the world coordinate space and the two coordinate values of the two-dimensional pixel coordinates are acquired.

17. The calibration method according to claim 13 , wherein, in the step of calculating parameters, the camera model is applied to a plurality of pieces of calibration data representing the corresp

Assignees

• Olympus Corp

Inventors

• Matsuzawa Toshiaki

Classifications

• H04N25/61 Primary

  the noise originating only from the lens unit, e.g. flare, shading, vignetting or "cos4" · CPC title

• G06T7/80 Primary

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

• H04N17/002

  for television cameras · CPC title

• G01B11/00

  Measuring arrangements characterised by the use of optical techniques · CPC title

• G06T5/006

  Physics · mapped topic