Index identification method and apparatus

• US 20050069196A1
• Filed: 09/29/2004
• Published: 03/31/2005
• Est. Priority Date: 09/30/2003
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Satoh, Kiyohide, Uchiyama, Shinji
• Granted Patent: US 7,676,079 B2
• Time in Patent Office: Days
• US Class Current: 382/154
• CPC Class Codes: G06T 2207/30244 Camera pose
• CPC Class Codes: G06T 7/70 Determining position or orientation of objects or cameras camera calibration G06T7/80
• CPC Class Codes: G06V 10/245 by locating a pattern; Special marks for positioning

Abstract

An index arranged on a real space is detected from an image sensed by a camera, and the position of the index in the image is calculated (S405). The index is projected onto the image sensing plane of the camera on the basis of the position and orientation information of the camera, the position information of the index, and the like (S403). A corresponding index is identified based on the distance between the detected and projected indices on the image plane, and geometric information of the index (e.g., directionality) (S408). With this method, an index can be accurately identified by a simple method.

Claims

1. An index identification method for detecting and identifying an index from an acquired image using position information and geometric information of the index, which are held in advance, comprising:

an image acquisition step of acquiring an image obtained by sensing a real space including an index having a predetermined shape by an image sensing device;

a position and orientation information acquisition step of acquiring measurement results of a three-dimensional position and orientation of at least one of the image sensing device and the real object; and

an index identification step of detecting and identifying the index from the acquired image on the basis of the three-dimensional position and orientation measurement results, and the position information and the geometric information of the index.

2. The method according to claim 1, wherein,

said geometric information is information associated with directionality of the index,

the index identification step includes an estimated position calculation step of calculating an estimated position of the index on an image sensing plane of the image sensing device on the basis of the three-dimensional position and orientation measurement results of at least one of the image sensing device and the real object acquired in the position and orientation information acquisition step, and the position information of the index, and

the index identification step includes a step of identifying correspondence between an index detected in the image and the index on the basis of a position of the index in the image, the estimated position of the index calculated in the estimated position calculation step, and the information associated with the directionality of the index.

3. The method according to claim 2, wherein the index identification step includes a step of identifying on the basis of directionality of the index detected in the image, and information associated with directionality, which is recorded in association with an index having the estimated position close to the index in advance.

4. The method according to claim 2, wherein the index is formed by a basic shape having no directionality, and a directionality giving shape that gives directionality to the basic shape, and a direction of the index is recognized using a positional relationship between the basic shape and the directionality giving shape of the index identified in the image in the index identification step.

5. The method according to claim 2, wherein the index identification step includes:

a step of calculating a barycentric position of an image of the index in the image;

a step of determining a plurality of representative point positions of the index using the barycentric position; and

a determination step of determining a direction of the index using image information of the barycentric positions and image information of the plurality of representative point positions.

6. The method according to claim 2, wherein the information associated with directionality of the index is three-dimensional position information of a specific vertex of the index.

10. The method according to claim 1, wherein,

said geometric information is information associated with an area of the index,

the index identification step includes a projected index calculation step of calculating information associated with a position and area of a projected index formed by projecting the index onto an image sensing plane of the image sensing device on the basis of the three-dimensional position and orientation measurement result of at least one of the image sensing device and the real object acquired in the position and orientation information acquisition step, and information associated with a position and area of the index, and

the index identification step includes a step of identifying correspondence between an index detected in the image and the index on the basis of the information associated with the position and area of the index detected in the image and the information associated with the position and area of the projected index.

11. The method according to claim 10, wherein the index identification step includes a step of identifying a region which has a small distance and a small area difference from the projected index of those detected in the image as an index corresponding to the projected index.

12. The method according to claim 10, wherein the region detection step includes a step of detecting a continuous region having a specific color or a lightness difference from a surrounding portion as the index.

13. The method according to claim 10, wherein the information associated with the index is information associated with a three-dimensional coordinate position of a central point of the index and an outer shape of the index.

14. The method according to claim 13, wherein the index has a circular shape, and the information associated with the outer shape indicates a radius or diameter.

15. The method according to claim 13, wherein the index has a regular polygonal shape, and the information associated with the outer shape is information indicating three-dimensional coordinate positions of vertices.

18. A computer program for making a computer execute an index identification method of claim 1.

19. A computer-readable recording medium storing a computer program of claim 18.

7. An index which is arranged on a real space and is used as an absolute position reference on a predetermined coordinate system, characterized by having an outer appearance formed by a combination of a basic shape having no directionality, and one directionality giving shape that gives directionality to the basic shape.

8. The index according to claim 7, wherein the directionality giving shape has a feature in terms of image identification different from the basic shape, and is formed at an offset position inside the basic shape.

9. The index according to claim 7, wherein the directionality giving shape is set to contact or to be separated from the basic shape.

16. An index identification apparatus for detecting and identifying an index from an acquired image using position information and geometric information of the index, which are held in advance, comprising:

image acquisition unit adapted to acquire an image obtained by sensing a real space including an index having a predetermined shape by an image sensing device;

position and orientation information acquisition unit adapted to acquire measurement results of a three-dimensional position and orientation of at least one of the image sensing device and the real object; and

index identification unit adapted to detect and identify the index from the acquired image on the basis of the three-dimensional position and orientation measurement results, and the position information and the geometric information of the index.

17. The apparatus according to claim 16, further comprising:

the image sensing device; and

three-dimensional position and orientation measurement unit adapted to measure a three-dimensional position and orientation of at least one of the image sensing device and the real object.