Enhanced data capture from imaged documents

• US 7,573,616 B2
• Filed: 05/25/2001
• Issued: 08/11/2009
• Est. Priority Date: 08/11/2000
• Status: Active Grant

• Current Assignee: McGraw Hill LLC
• Original Assignee: CTB/McGraw Hill LLC
• Inventors: Poor, David D. S.
• Primary Examiner(s): Worku; Negussie
• Application Number:
  US10/344,377
• Publication Number:
  US 20040131279A1
• Time in Patent Office: 3,000 Days
• Field of Search: 358/474, 358/1.9, 358/518, 358/501, 358/1.2, 358/1.14, 382/197, 382/188, 382/203, 382/113, 235/456, 235/495, 250/556, 250/557
• US Class Current: 358/474
• CPC Class Codes: G06K 17/0032 Apparatus for automatic testing and analysing marked record carriers, used for examinations of the multiple choice answer type teaching apparatus working with questions and answers G09B7/00
• CPC Class Codes: G06K 7/12 using a selected wavelength, e.g. to sense red marks and ignore blue marks
• CPC Class Codes: G06K 7/1447 extracting optical codes from image or text carrying said optical code
• CPC Class Codes: G06V 10/143 Sensing or illuminating at different wavelengths
• CPC Class Codes: G06V 10/22 by selection of a specific region containing or referencing a pattern; Locating or processing of specific regions to guide the detection or recognition
• CPC Class Codes: G06V 10/242 by image rotation, e.g. by 90 degrees
• CPC Class Codes: G06V 10/25 Determination of region of interest [ROI] or a volume of interest [VOI]

Abstract

Methods and apparatus are disclosed for locating an area of interest within a digital image of a form captured by an imaging scanner. Specific examples include methods and apparatus for optical mark reading with a digital imaging scanner. In many of the methods, an image of a response form is captured by a scanner, and target areas for possible responses are located within the image based upon an expected location being adjusted as necessary for certain error-inducing defects in the forms or scanning process. Also disclosed are steps to normalize the darkness values of pixels captured from an optically scanned form.

Claims

1. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:

a) locating edges of the captured image of the form within a total pixel scan captured by the scanner;

b) determining a sheet position parameter related to the location of the edges;

c) defining an expected location of the area of interest; and

d) adjusting the expected location based upon the sheet position parameter.

2. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:

a) defining expected locations of preprinted key marks in the image;

b) interrogating pixels within a proscribed area around key mark expected locations to locate key marks in the image;

c) determining a key mark parameter related to the location of the key marks;

d) defining an expected location of the area of interest; and

e) adjusting the expected location of the area of interest based upon the key mark parameter.

3. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:

a) locating edges of the captured image of the form within a total pixel scan captured by the scanner;

b) determining a sheet position parameter related to the location of the edges;

c) defining expected locations of preprinted key marks in the image;

d) adjusting the key mark expected locations based upon the sheet position parameter;

e) interrogating the pixels within a proscribed area around each adjusted key mark expected location to locate the key marks in the image;

f) determining key mark parameters related to the location of the key marks;

g) defining an expected location of the area of interest; and

h) adjusting the expected location of the area of interest based upon a key mark parameter.

4. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:

a) defining expected locations of preprinted speed marks in the image;

b) interrogating the pixels within a proscribed area around expected speed mark locations to locate the speed marks in the image;

c) determining a scanning speed parameter related to spacings between the speed marks;

d) defining an expected location of the area of interest; and

e) adjusting the expected location of the area of interest based upon the scanning speed parameter.

5. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:

a) locating edges of the captured image of the form within a total pixel scan captured by the scanner;

b) determining a sheet position parameter related to the location of the edges;

c) defining expected locations of preprinted speed marks in the image;

d) adjusting the speed mark expected locations based upon the sheet position parameter;

e) interrogating pixels within a proscribed area around adjusted speed mark expected locations to locate the speed marks in the image;

f) determining a scanning speed parameter related to spacings between the speed marks;

g) defining an expected location of the area of interest; and

h) adjusting the expected location of the area of interest based upon the scanning speed parameter.

6. The method of claim 5, comprising the additional step of adjusting the expected location of the area of interest based upon the sheet position parameter.

7. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:

a) locating edges of the captured image of the form within a total pixel scan captured by the scanner;

b) determining a sheet position parameter related to the location of the edges;

c) defining expected locations of preprinted speed marks in the image;

d) adjusting the speed mark expected locations based upon the sheet position parameter;

e) interrogating pixels within a proscribed area around adjusted speed mark expected locations to locate the speed marks in the image;

f) determining a scanning speed parameter related to spacings between the speed marks;

g) defining expected locations of preprinted key marks in the image;

h) adjusting the key mark expected locations based upon the scanning speed parameter;

i) interrogating pixels within a proscribed area around each adjusted key mark expected location to locate the key marks in the image;

j) determining a key mark parameter related to the location of the key marks;

k) defining an expected location of the area of interest; and

l) adjusting the expected location of the area of interest based upon a key mark parameter.

8. The method of claim 7 comprising the additional step of adjusting the expected location of the area of interest based upon the scanning speed parameter.

9. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:

a) defining an expected location for the area of interest based upon an idealized captured image of the form;

b) locating the digital image of the form within a total pixel scan captured by the scanner;

c) calculating a sheet position parameter related to the location of the digital image of the form; and

d) adjusting the expected location for the area of interest based upon the sheet position parameter.

10. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:

a) defining an expected location for the area of interest based upon an idealized captured image of the form;

b) defining an expected location of preprinted key marks based upon an idealized captured image of the form;

c) interrogating pixels within a proscribed area around the expected locations of a plurality of key marks to locate those key marks in the captured image of the form;

d) determining a key mark parameter related to the location of the key marks in the captured image; and

e) adjusting the expected location of the area of interest based upon the key mark parameter.

11. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:

a) defining an expected location for the area of interest based upon an idealized captured image of the form;

b) defining an expected location of preprinted speed marks based upon an idealized captured image of the form;

c) interrogating pixels within a proscribed area around the expected locations of the speed marks to locate those speed marks in the captured image;

d) determining a scanning speed parameter related to the spacing of the speed marks in the captured image; and

e) adjusting the expected location of the area of interest based upon the scanning speed parameter.

12. A method of optical mark reading (OMR) with a digital imaging scanner, said method comprising the steps of:

a) scanning with a digital imaging scanner a sheet with a plurality of OMR response targets to capture an image of the sheet and any OMR response marks made thereon;

b) locating edges of the captured image of the sheet within a total pixel scan captured by the scanner;

c) determining a sheet position parameter related to the location of the edges;

d) defining an expected location of an OMR response target based upon an idealized captured image of the sheet;

e) adjusting the expected location of the OMR response target based upon the sheet position parameter;

f) interrogating the darkness value of a plurality of pixels within a proscribed area determined from the adjusted expected location of the OMR response target; and

g) making a goodness of mark determination based upon the darkness values.

13. A method of optical mark reading (OMR) with a digital imaging scanner, said method comprising the steps of:

a) scanning with a digital imaging scanner a sheet with a plurality of OMR response targets and preprinted key marks to capture an image of the sheet and any OMR response marks made thereon;

b) locating key marks in the captured image of the sheet;

c) determining a key mark parameter based upon the location of the key marks in the captured image;

d) defining an expected location of an OMR response target based upon an idealized captured image of the sheet;

e) adjusting the expected location of the OMR response target based upon the key mark parameter;

f) interrogating the darkness value of a plurality of pixels within a proscribed area determined from the adjusted expected location of the OMR response target; and

g) making a goodness of mark determination based upon the darkness values.

14. A method of optical mark reading (OMR) with a digital imaging scanner, said method comprising the steps of:

a) scanning with a digital imaging scanner a sheet with a plurality of OMR response targets and speed marks to capture an image of the sheet and any OMR response marks made thereon;

b) locating speed marks in the captured image of the sheet;

c) determining a scanning speed parameter based upon the location of the speed marks in the captured image;

d) defining an expected location of an OMR response target based upon an idealized captured image of the sheet;

e) adjusting the expected location of the OMR response target based upon the scanning speed parameter;

f) interrogating the darkness value of a plurality of pixels within a proscribed area determined from the adjusted expected location of the OMR response target; and

g) making a goodness of mark determination based upon the darkness values.