System and method for reading license plates

• US 7,339,495 B2
• Filed: 09/20/2005
• Issued: 03/04/2008
• Est. Priority Date: 01/26/2001
• Status: Expired due to Term

• Current Assignee: Vertex Aerospace, LLC
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Kavner, Douglas M.
• Primary Examiner(s): Lee; Benjamin C.
• Assistant Examiner(s): PHAM, LAM P
• Application Number:
  US11/231,102
• Publication Number:
  US 20060056658A1
• Time in Patent Office: 896 Days
• Field of Search: 340/903, 340/928, 340/933, 340/937, 348/143, 348/148, 348/161, 382/105, 701/117, 705/13
• US Class Current: 340/933
• CPC Class Codes: G07B 15/06 Arrangements for road pricing or congestion charging of vehicles or vehicle users, e.g. automatic toll systems
• CPC Class Codes: G07B 15/063 using wireless information transmission between the vehicle and a fixed station identification of vehicles G08G
• CPC Class Codes: G08G 1/017 identifying vehicles G08G1/015, G08G1/054 take precedence

Abstract

A method for reading a license plate disposed on a vehicle includes determining whether a license plate image is required, automatically processing the license plate image in response to determining that the license plate image is required, providing at least one verified image, and determining whether to manually read the license plate image by matching the license plate image with the at least one verified image.

Claims

1. A method for reading a license plate disposed on a vehicle, the method comprising:

determining whether a license plate image is required in response to an attempt to read a vehicle transponder, wherein the vehicle transponder is at least one of absent, indicative of a vehicle class mismatch or on an exception list;

capturing the license plate image;

retrieving at least one verified image associated with the license plate image;

automatically processing the license plate image, wherein the automatically processing comprises comparing the license plate image with the at least one verified image; and

determining whether to manually read the license plate image in response to the comparing.

2. The method of claim 1 further comprising manually reading the license plate image.

3. The method of claim 2 wherein manually reading the license plate image comprises providing a sub-image for reducing license plate image storage.

4. The method of claim 3 wherein providing a sub-image comprises zooming in on the license plate in the license plate image.

5. The method of claim 2 wherein manually reading the license plate image comprises:

displaying the license plate image to at least three different operators;

entering at least three license plate numbers as determined by the at least three different operators; and

determining if at least two of the at least three determined license plate numbers are identical.

6. The method of claim 1 wherein comparing the license plate image comprises correlating the license plate image with the at least one verified image.

7. The method of claim 6 further comprising:

generating feature data derived from the license plate image; and

generating feature data derived from the at least one verified image, wherein the correlating comprises correlating the feature data derived from the license plate image with the feature data derived from the at least one verified image.

8. The method of claim 6 further comprising:

providing a match confidence measure; and

determining whether the license plate image should be read manually in response to comparing a match confidence measure to a predetermined match threshold.

9. The method of claim 8 further comprising:

manually reading the license plate image in response to the match confidence measure being less than the predetermined match threshold.

10. The method of claim 1 wherein automatically processing the license plate image comprises using optical character recognition for recognizing a license plate number.

11. The method of claim 10 further comprising:

providing a read confidence measure in response to recognizing the license plate number;

comparing the read confidence measure to a predetermined read threshold; and

determining in response to the read confidence measure being less than the predetermined read threshold that the license plate image should be read manually.

12. The method of claim 1 further comprising detecting the vehicle, wherein detecting the vehicle comprises at least one of:

reading the transponder disposed on the vehicle;

scanning the vehicle with a laser beam;

or

sensing the vehicle with an induction loop.

13. The method of claim 1 wherein the comparing the license plate image comprises matching the license plate image with the at least one verified image.

14. The method of claim 13 further comprising:

generating feature data derived from the license plate image; and

generating feature data derived from the at least one verified image, wherein the matching comprises matching the feature data derived from the license plate image with the feature data derived from the at least one verified image.

15. The method of claim 1 further comprising updating the at least one verified image.

16. The method of claim 1 further comprising:

determining whether the license plate number associated with the license plate image is a registered plate number; and

bypassing manually rereading the license plate image in response to determining that the license plate number associated with the license plate image is a registered plate number.

17. The method of claim 1 further comprising:

manually reading the license plate image for providing a manually read license plate number;

automatically reading the license plate image for providing an automatically read license plate number;

comparing the manually read license plate number and the automatically read license plate number; and

bypassing manually rereading the license plate image in response to determining that the manually read license plate number and the automatically read license plate number are identical.

18. The method of claim 1 further comprising:

providing an automatically read license plate number in response to automatically processing the license plate image;

associating a transponder reading with a transponder registered license plate number;

comparing the automatically read license plate number and the transponder registered license plate number; and

determining whether to manually read the license plate image in response to determining that the automatically read license plate number and the transponder registered license plate number are identical.

19. The method of claim 1 further comprising:

determining if the license plate image should be discarded; and

discarding the license plate image in response to determining the license plate image should be discarded.

20. The method of claim 1 wherein retrieving at least one verified image comprises:

providing at least one stored image of the license plate and a corresponding license plate number;

verifying the at least one stored image for providing the at least one verified image.

21. The method of claim 20 wherein verifying the at least one stored image comprises:

manually reading the license plate image for providing a manually read license plate number;

associating a transponder reading with a transponder registered license plate number; and

determining that the manually read license plate number and the transponder registered license plate number are identical.

22. The method of claim 20 wherein verifying the at least one stored image comprises:

manually reading the license plate image for providing a manually read license plate number;

automatically reading the license plate image for providing an automatically read license plate number; and

determining that the manually read license plate number and the automatically read license plate number are identical.

23. The method of claim 20 further comprising adding a new license plate image to a set of verified images in response to verifying the at least one stored image and in response to the set having fewer than a maximum number of images for the corresponding license plate number.

24. The method of claim 20 further comprising updating one of the at least one verified image if the one of the at least one verified image is replaceable.

25. The method of claim 24 further comprising determining that the one of the at least one verified image is replaceable in response to determining that an image quality ratio of the one of the at least one verified image is less than a predetermined threshold and determining that a number of correlation matches associated with the image quality ratio is greater than a predetermined sample size.

26. The method of claim 25 wherein the image quality ratio comprises a ratio of a hit count divided by a sum of the hit count and a strike count.

27. The method of claim 26 wherein the hit count includes the number of correlation matches having a match confidence measure greater than or equal to a predetermined match threshold and the license plate image is readable and manual reads of the license plate image are consistent.

28. The method of claim 26 wherein the strike count includes a number of correlation matches having a match confidence measure less than a predetermined match threshold and the license plate image being processed is readable and all manual reads of the license plate image are consistent.

29. The method of claim 1 further comprising:

arranging a plurality of roadside toll collectors at intervals along a roadway, each roadside toll collector coupled to at least one of;

a traffic probe reader, a toll gateway or an enforcement gateway, for reading a transponder disposed on a vehicle;

determining a license plate number corresponding to the transponder reading from the vehicle;

comparing the license plate number corresponding to the transponder to the license plate number recognized from the license plate image; and

determining in response to the plate number corresponding to the transponder being the same as the license plate number recognized from the license plate image that further identification of the license plate is not required.

30. The method of claim 1 further comprising:

combining a plurality of transactions to form a trip; and

associating a license plate identification from a first transaction of the trip with a different second transaction for minimizing the number of manual reads.

31. The method of claim 1, wherein the determining whether a license plate image is required further comprises determining whether a license plate image is required in response to at least one of, a customer audit, a system audit, or a system maintenance.