Method and apparatus for selective processing of captured images

• US 20040126036A1
• Filed: 02/11/2003
• Published: 07/01/2004
• 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.
• Granted Patent: US 7,417,774 B2
• Time in Patent Office: Days
• US Class Current: 382/287
• 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 identifying intended response marks in an optically scanned image of a response sheet having key marks and response targets printed in the same color. Pixel darkness values assigned by a digital imaging scanner are used to locate key marks and response targets and to identify response marks. Areas of the sheet may be selectively filtered to mask the response targets. Alternatively, a color imaging scanner may be used to produce a set of color values, such as RBG values, for each pixel. Software can act as a virtual filter by using the RBG values to detect or to mask a color in the image.

Claims

1. A method of identifying intended response marks in an optically scanned image of a response sheet having response targets printed in areas of the sheet apart from a section of the sheet containing key marks, the key marks and response targets being printed in the same color, the method comprising the steps of:

(a) providing a digital imaging scanner having a light source and sensor for detecting light reflected off the sheet, the scanner being capable of assigning pixel darkness values so that each pixel is assigned a gray scale value;

(b) providing a color filter in the color of the key marks and response targets,

(c) arranging the filter in relation to the sheet as it passes through the scanner such that light reflected from the section containing key marks is not filtered and light reflected from the response targets is filtered,

(d) scanning the sheet with the digital imaging scanner;

(e) using the gray scale values to locate key marks in the captured image,

(f) calculating from the location of the key marks in the image an expected location of response targets in the image,

(g) using the gray scale values to identify an intended response mark at the expected location of a target.

2. A digital imaging scanner for performing optical mark recognition (OMR) of a response sheet having response targets printed in areas of the sheet apart from a section of the sheet containing key marks, the response targets and key marks being printed in the same color, the scanner comprising:

a) a light source;

b) a sensor for detecting light reflected off the sheet; and

c) a filter disposed between the sensor and the light source so that the light reflected off the key marks is not filtered and light reflected off the response targets is filtered.

3. A method of identifying intended response marks in an optically scanned image of a response sheet having key marks and response targets printed in the same color, comprising the steps of:

(a) providing a digital imaging scanner capable of capturing an image of a response sheet with RGB values assigned to each pixel corresponding to the color of that pixel,

(b) providing a response sheet having key marks and response targets printed in the same color,

(c) capturing with the scanner a digital image of the sheet with each pixel having RGB values assigned thereto,

(d) locating key marks in the captured image by processing pixels having RGB values that correspond to the color of the key marks,

(e) calculating from the location of the key marks in the image an expected location of response targets in the image,

(f) processing pixels having RGB values corresponding to any color other than the color of the target to determine whether an intended response mark was made at a response target.

4. A method as in claim 3, wherein the response sheet has key marks and response targets printed in red.

5. A method of performing optical mark recognition (OMR) with a digital scanner, said method comprising the steps of:

(a) providing a digital imaging scanner capable of capturing an image of a response sheet with RGB values assigned to each pixel corresponding to the color of that pixel,

(b) providing a response sheet having a plurality of response targets printed in the same color,

(c) capturing with the scanner a digital image of the sheet with each pixel having a RGB value assigned thereto,

(d) using RGB values that corresponds to the color of the targets to locate response targets in the captured image,

(e) using RGB values that corresponds to any color other than the color of the target to determine whether an intended response mark was made at a response target.

6. A method as in claim 5, wherein the response sheet has response targets printed in red.

7. A system for identifying intended response marks in an optically scanned image of a response sheet having key marks and response targets printed in the same color, comprising:

(a) a digital imaging scanner capable of capturing an image of a response sheet with RGB values assigned to each pixel corresponding to the color of that pixel,

(b) computer software capable of processing the RGB values that correspond to the color of the key marks to locate key marks in the captured image,

(c) computer software capable of calculating from the location of the key marks in the image an expected location of response targets in the image,

(d) computer software capable of processing the RGB values that correspond to any color other than the color of the target to identify an intended response mark at the expected location of the target.

8. A system as in claim 7, wherein the response sheet has key marks and response targets printed in red.

9. A system for performing optical mark recognition (OMR), comprising:

(a) a digital imaging scanner capable of capturing an image of a response sheet with RGB values assigned to each pixel corresponding to the color of that pixel,

(b) computer software capable of using RGB values that correspond to the color of response targets on the sheet to locate response targets in the captured image;

(c) computer software capable of using RGB values that correspond to any color other than the color of the target to determine whether an intended response mark was made at a response target.

10. A system as in claim 9, wherein the response targets are printed in red.