Curvature correction and image processing

• US 8,233,200 B2
• Filed: 11/26/2008
• Issued: 07/31/2012
• Est. Priority Date: 03/14/2005
• Status: Active Grant

• Current Assignee: GTECH Corporation (GTECH SpA)
• Original Assignee: GTECH Corporation (GTECH SpA)
• Inventors: Metayer, Frank J., Toral, Carlos Cervantes, Xue, Duncan D.
• Primary Examiner(s): Worku, Negussie
• Application Number:
  US12/323,701
• Publication Number:
  US 20090074327A1
• Time in Patent Office: 1,343 Days
• Field of Search: 358/471, 358/474, 358/1.15, 358/488, 358/482, 358/483, 348/208.14, 348/222.1, 348/234, 382/103, 382/199, 382/294
• US Class Current: 358/474
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06T 3/06 Topological mapping of higher dimensional structures onto lower dimensional surfaces
• CPC Class Codes: G06T 5/80 Geometric correction
• CPC Class Codes: G07F 17/3288 Betting, e.g. on live events, bookmaking
• CPC Class Codes: G07F 17/329 Regular and instant lottery, e.g. electronic scratch cards

Abstract

A system and process for reading forms using a curvature distortion correction scheme is disclosed. A model image of a known form is partitioned into sectors defined by at least three alignment marks, and a transfer or correction function for each sector is generated by comparing the locations of alignment marks on a captured unread image of a form to those on a model image. The transfer function is then applied to the other marks within the sector to calculate a correct location of the marks. Each sector is sized to reasonably ensure curvature distortions are handled such that all the marks on a form are properly found and interpreted. Errors may be checked and, if they persist, smaller sectors may be defined and employed, if available.

Claims

1. A process for reading information on an unread form, the process comprising the steps of:

storing a model image of a model of the unread form in a computer system, the model image containing alignment marks;

storing an unread image of the unread form in the computer system, the unread image containing alignment marks that correspond to the alignment marks on the model image;

partitioning the model image into a group of sectors, wherein each sector is defined by the locations of at least three alignment marks;

detecting the sectors on the unread image that correspond to the sectors on the model image by comparing the alignment marks on the model image to the corresponding alignment marks on the unread image;

generating a transfer function for each sector of the unread image from the locations of corresponding alignment marks of the model image and the unread image;

applying each sector'"'"'s transfer function to the locations of marks on the corresponding sector of the unread image to generate a corrected unread image with corrected locations of the marks; and

reading information on the corrected unread image of the unread form.

2. The process of claim 1, further comprising the steps of:

forming a coordinate system for each sector of the unread image, wherein the transfer function for each sector compensated for distortions in the unread image, and

determining the meanings of the corrected locations of the marks within each sector of the unread image by reference to corresponding locations within each sector of the model image.

3. The process of claim 2, wherein the sector is defined by the location of three alignment marks and the process further comprises the step of:

applying a three point transfer function equation to each sector defined by three alignment marks.

4. The process of claim 3, further comprising the steps of:

constructing an x, y coordinate system for the location of marks in the model image and an x′

, y′

coordinate system for marks in the unread image, wherein the three mark transfer function is;

x′

=A′

x+B′

y+C′

and y′

=D′

x+E′

y=F′

.

5. The process of claim 2, wherein the sector is defined by the location of four alignment marks and the process further comprises the step of:

applying a four point transfer function equation to each sector defined by four alignment marks.

6. The process of claim 5, further comprising the steps of:

constructing an x, y coordinate system for the location of marks in the model form image and x′

, y′

coordinate system for marks in the unread form image, wherein the four mark transfer function is;

7. The process of claim 2, further comprising the steps of applying a multi-mark transfer function to each sector of the unread form image defined by eight alignment marks, wherein the transfer function is

8. The process of claim 1, further comprising the steps of:

generating corrected locations of specific marks on the unread image, wherein the locations of the specific marks on the model image are known;

calculating a difference between the corrected locations of the specific marks on the unread image to the corresponding known locations of the specific marks on the model image;

establishing an error threshold; and

comparing the difference to the threshold, and rejecting the form if the difference exceeds the threshold.

9. The process of claim 1, wherein the unread form is selected from the group consisting of a printed document, a play slip, a lottery scratch ticket and a lottery instant ticket.

10. A system for processing and correcting markings on a known form, the system comprising:

a light source that illuminates a form that reflects some of the light;

a camera arranged to receive the reflected light from the form and capture an unread image of the form;

camera electronics to extract the unread image of the form from the camera, the unread image having alignment marks at locations;

a computer processing system in communication with the camera electronics, the computer processing system comprising;

at least one memory configured to store;

the unread image of the form;

a model image of the form having alignment marks;

sectors defined by the locations of the alignment marks; and

a transfer functions for each sector from the locations of corresponding alignment marks of the stored unread and model images; and

at least one processor configured to execute an application that generates corrected locations of the alignment marks within each sector of the stored unread image by application of the transfer function to the alignment marks within each sector of the stored unread image.

11. The system of claim 10, further comprising:

a coordinate system for locations on the stored unread and the model images; and

an application that determines the meanings of marks with corrected location by reference to the corresponding locations on the model image.

12. The system of claim 11, further comprising:

specific marks with corrected locations on the stored unread image and corresponding specific marks on the model image, wherein the locations of the specific marks on the model image are known;

a calculator for calculating a difference between the corrected locations of the specific marks on the unread image to the corresponding known locations of the specific marks on the model image;

an error threshold; and

a comparator that compares the difference to the error threshold and rejects the form if the difference exceeds the threshold.

13. The system of claim 10, wherein the known form is selected from the group consisting of a printed document, a play slip, a lottery scratch ticket and a lottery instant ticket.

14. A computer readable medium encoded with computer executable program instructions for determining the location of marks on a known type of form, the computer executable program instructions comprising one or more program instructions for performing the steps of:

storing a model image of a model of the unread form in a computer system, the model image containing alignment marks;

storing an unread image of the unread form in the computer system, the unread image containing alignment marks that correspond to the alignment marks on the model image;

partitioning the model image into a group of sectors, wherein each sector is defined by the locations of at least three alignment marks;

detecting the sectors on the unread image that correspond to the sectors on the model image by comparing the alignment marks on the model image to the corresponding alignment marks on the unread image;

generating a transfer function for each sector of the unread image from the locations of corresponding alignment marks of the model image and the unread image; and

applying each sector'"'"'s transfer function to the locations of marks on the corresponding sector of the unread image to generate corrected locations of the marks, thereby enabling the reading of the unread form.

15. The computer readable medium of claim 14, further comprising program instructions for performing the steps of:

forming a coordinate system for each sector, wherein the transfer function for each sector compensates for distortions,

determining the meanings of the corrected locations of the marks within each sector of the unread image by reference to corresponding locations of marks within each sectors of the model image; and

applying a three mark transfer function to each sector defined by three alignment marks.

16. The computer readable medium of claim 15, wherein the three mark transfer function is:

x′

=A′

x+B′

y+C′

and y′

=D′

x+E′

y=F′

.

17. The computer readable medium of claim 14, further comprising program instructions for performing the steps of:

forming a coordinate system for each sector, wherein the transfer function for each sector compensates for distortions,

determining the meanings of the corrected locations of the marks within each sector of the unread image by reference to corresponding locations of marks within each sector of the model image; and

applying a four mark transfer function to each sector defined by four alignment marks.

18. The computer readable medium of claim 17, wherein the four mark transfer function is:

19. The computer readable medium of claim 14, further comprising program instructions for performing the steps of:

forming a coordinate system for each sector, wherein the transfer function for each sector compensates for distortions,

determining the meanings of the corrected locations of the marks within each sector of the unread image by reference to corresponding locations of marks within each sector of the model image; and

applying a multi-mark transfer function to each sector defined by eight alignment marks, wherein the transfer function is

20. The computer readable medium of claim 14, further comprising program instructions for performing the step of:

determining the meanings of the corrected locations of the marks within each sector of the unread image by reference to corresponding locations of marks within each sector of the model image.