METHOD AND SYSTEM FOR DETECTION-BASED SEGMENTATION-FREE LICENSE PLATE RECOGNITION

• US 20170249524A1
• Filed: 02/25/2016
• Published: 08/31/2017
• Est. Priority Date: 02/25/2016
• Status: Active Grant

• Current Assignee: Conduent Business Services, LLC (Conduent, Inc.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Bulan, Orhan, Ramesh, Palghat, Kozitsky, Vladimir
• Granted Patent: US 10,068,146 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 18/2193 based on specific statistical tests
• CPC Class Codes: G06F 18/295 Markov models or related models, e.g. semi-Markov models; Markov random fields; Networks embedding Markov models
• CPC Class Codes: G06V 10/85 Markov-related models; Markov random fields
• CPC Class Codes: G06V 20/52 Surveillance or monitoring of activities, e.g. for recognising suspicious objects recognising microscopic objects G06V20/69
• CPC Class Codes: G06V 20/62 Text, e.g. of license plates, overlay texts or captions on TV images
• CPC Class Codes: G06V 20/625 License plates
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/1463 Orientation detection or correction, e.g. rotation of multiples of 90 degrees

Abstract

A detection-based segmentation-free method and system for license plate recognition. An image of a vehicle is initially captured utilizing an image-capturing unit. A license plate region is located in the image of the vehicle. A set of characters can then be detected in the license plate region and a geometry correction performed based on a location of the set of characters detected in the license plate region. An operation for sweeping an OCR across the license plate region can be performed to infer characters with respect to the set of characters and locations of the characters utilizing a hidden Markov model and leveraging anchored digit/character locations.

Claims

1. A detection-based segmentation-free method for license plate recognition, said method comprising:

detecting a discrete set of characters in a license plate region in an image of a vehicle;

performing a geometry correction based on a location of said set of characters detected in said license plate region;

sweeping an OCR across said license plate region to infer detected and undetected characters in said license plate region in said image with respect to said set of characters and detected locations of said characters; and

incorporating detected character types with respect to said characters and said detected locations of said characters as a part of said sweeping said OCR.

2. The method of claim 1 further comprising initially locating said license plate region in said image of said vehicle.

3. The method of claim 1 further comprising utilizing a hidden Markov model to infer said characters.

4. The method of claim 1 further comprising capturing said image of said vehicle with an image-capturing unit.

5. The method of claim 1 wherein at least one character among said set of characters comprises a digit.

6. The method of claim 3 wherein said OCR comprises a segmentation-free OCR utilizing said hidden Markov model.

7. The method of claim 1 wherein said performing said geometry correction based on said location of said set of characters detected in said license plate region, further comprises:

performing a vertical cropping operation with respect to said set of characters detected in said license plate region.

8. A detection-based segmentation-free system for license plate recognition, said system comprising:

at least one processor; and

a computer-usable medium embodying computer program code, said computer-usable medium capable of communicating with said at least one processor, said computer program code comprising instructions executable by said at least one processor and configured for;

detecting a discrete set of characters in a license plate region in an image of a vehicle;

performing a geometry correction based on a location of said set of characters detected in said license plate region;

sweeping an OCR across said license plate region to infer detected and undetected characters in said license plate region in said image with respect to said set of characters and detected locations of said characters; and

incorporating detected character types with respect to said characters and said detected locations of said characters as a part of said sweeping said OCR.

9. The system of claim 8 wherein said instructions are further configured for initially locating said license plate region in said image of said vehicle.

10. The system of claim 8 wherein said instructions are further configured for utilizing a hidden Markov model to infer said characters.

11. The system of claim 8 wherein said instructions are further configured for capturing said image of said vehicle with an image-capturing unit.

12. The system of claim 8 wherein at least one character among said set of characters comprises a digit.

13. The system of claim 10 wherein said OCR comprises a segmentation-free OCR utilizing said hidden Markov model.

14. The system of claim 8 wherein said instructions for performing said geometry correction based on said location of said set of characters detected in said license plate region are further configured for:

performing a vertical cropping operation with respect to said set of characters detected in said license plate region.

15. A non-transitory processor-readable medium storing computer code representing instructions to cause a process for detection-based segmentation-free license plate recognition, said computer code comprising code to:

detect a discrete set of characters in a license plate region in an image of a vehicle;

perform a geometry correction based on a location of said set of characters detected in said license plate region;

sweep an OCR across said license plate region to infer detected and undetected characters in said license plate region in said image with respect to said set of characters and detected locations of said characters; and

incorporate detected character types with respect to said characters and said detected locations of said characters as a part of said sweeping said OCR.

16. The processor-readable medium of claim 15 wherein said code further includes code to initially locate said license plate region in said image of said vehicle.

17. The processor-readable medium of claim 15 wherein said code further includes code to utilize a hidden Markov model to infer said characters.

18. The processor-readable medium of claim 15 wherein said code further includes code to capture said image of said vehicle with an image-capturing unit.

19. The processor-readable medium of claim 15 wherein at least one character among said set of characters comprises a digit.

20. The processor-readable medium of claim 17 wherein said OCR comprises a segmentation-free OCR utilizing said hidden Markov model.