Method and apparatus for recognition of symbols in images of three-dimensional scenes

• US 20050180632A1
• Filed: 12/30/2004
• Published: 08/18/2005
• Est. Priority Date: 09/22/2000
• Status: Active Grant

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International, Inc.
• Inventors: Aradhye, Hrishikesh, Myers, Gregory K.
• Granted Patent: US 7,738,706 B2
• Time in Patent Office: Days
• US Class Current: 382/182
• CPC Class Codes: G06V 20/63 Scene text, e.g. street names
• CPC Class Codes: G06V 30/1478 of characters or characters lines

Abstract

An apparatus and a concomitant method for rectification and recognition of symbols (e.g., to correct for the effects of perspective distortion, rotation and/or scale) in images of three-dimensional scenes is provided. The present method locates a reference region lying in a common plane with a symbol to be recognized, where the reference region represents an image of a planar object having assumed (e.g., known or standard) geometry and dimensions, along with at least four easily detectable correspondence points within that geometry. An image of the common plane is then rectified in three dimensions in accordance with the assumed dimensions of the reference region in order to produce a transformed (e.g., rectified) image of the symbol, which is significantly easier to recognize than the original imaged appearance of the symbol using existing recognition methods.

Claims

1. Method for rectifying at least one target object in a captured imagery, said method comprising the steps of:

locating a reference region lying in a common plane with an image of said at least one target object, said reference region representing an image of a reference object having assumed geometry and dimensions; and

rectifying an image of said common plane in accordance with said assumed dimensions.

2. The method of claim 1, wherein said rectifying is performed in three dimensions.

3. The method of claim 2, wherein said rectifying comprises:

applying a projective transformation to said image of said common plane.

4. The method of claim 1, further comprising:

recognizing said at least one target object in said rectified image of said common plane.

5. The method of claim 4, wherein said recognizing comprises:

applying image recognition processing to said rectified image to recognize said at least one target object in the captured imagery

6. The method of claim 1, wherein said reference object is substantially quadrilateral in shape.

7. The method of claim 6, wherein said reference object is an automobile license plate.

8. The method of claim 6, wherein said reference object is a business card.

9. The method of claim 6, wherein said reference object is an identification card.

10. A computer readable medium containing an executable program for rectifying at least one target object in a captured imagery, where the program performs the steps of:

locating a reference region lying in a common plane with an image of said at least one target object, said reference region representing an image of a reference object having assumed geometry and dimensions; and

rectifying an image of said common plane in accordance with said assumed dimensions.

11. The computer readable medium of claim 10, wherein said rectifying is performed in three dimensions.

12. The computer readable medium of claim 11, wherein said rectifying comprises:

applying a projective transformation to said image of said common plane.

13. The computer readable medium of claim 10, further comprising:

recognizing said at least one target object in said rectified image of said common plane.

14. The computer readable medium of claim 13, wherein said recognizing comprises:

applying image recognition processing to said rectified image to recognize said at least one target object in the captured imagery

15. The computer readable medium of claim 10, wherein said reference object is substantially quadrilateral in shape.

16. The computer readable medium of claim 15, wherein said reference object is an automobile license plate.

17. The computer readable medium of claim 15, wherein said reference object is a business card.

18. The computer readable medium of claim 15, wherein said reference object is an identification card.

19. Apparatus for rectifying at least one target object in a captured imagery, said apparatus comprising:

means for locating a reference region lying in a common plane with an image of said at least one target object, said reference region representing an image of a reference object having assumed geometry and dimensions; and

means for rectifying an image of said common plane in accordance with said assumed dimensions.

20. The apparatus of claim 19, wherein said means for rectifying rectifies said image of said common plane in three dimensions.