Method and apparatus to correct distortion of document copies

• US 6,954,290 B1
• Filed: 11/09/2000
• Issued: 10/11/2005
• Est. Priority Date: 11/09/2000
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Wu, Chai Wah, Tresser, Charles P., Braudaway, Gordon W., Martens, Marco, Micchelli, Charles A., Giordano, Frank P.
• Primary Examiner(s): Lee, Thomas D.
• Application Number:
  US09/708,517
• Time in Patent Office: 1,797 Days
• Field of Search: 358/452, 358/474, 358/488, 358/493, 358/3.26
• US Class Current: 358/3.26
• CPC Class Codes: G06V 30/1478 of characters or characters lines
• CPC Class Codes: H04N 1/00002 Diagnosis, testing or measuring; Detecting, analysing or monitoring not otherwise provided for error detection, error correction or monitoring in digital computers or digital computer components G06F11/00
• CPC Class Codes: H04N 1/00045 using a reference pattern designed for the purpose, e.g. a test chart
• CPC Class Codes: H04N 1/0005 in service, i.e. during normal operation
• CPC Class Codes: H04N 1/00082 Adjusting or controlling interrupting an operation H04N1/00915; inhibiting an operation H04N1/00925
• CPC Class Codes: H04N 1/00087 Setting or calibrating picture signal circuits H04N1/40
• CPC Class Codes: H04N 1/00092 relating to the original or to the reproducing medium, e.g. imperfections or dirt detecting properties of a sheet H04N1/00681
• CPC Class Codes: H04N 2201/0434 specially adapted for scanning pages of a book

Abstract

Pages of books are copied without distortion due to curvature of the page near the book binding or the distortion in a copied page is corrected using the spacing of equidistant bars on tape strips applied to the top and bottom edges of a page before copying. The tape is preferably transparent and rather narrow and easily attached to a page to be copied. The first step in the distortion correction procedure is to locate the bars at the top and bottom of the page. The distortion of the spacing between the imaged bars is computed based on the known distance between the equidistant bars. The computed distortion of the spacing is then input to a distortion correction algorithm. The output of the distortion correction algorithm generates a corrected image. This image may also optionally delete the bars so that they are not printed in the copy. The corrected image is then copied.

Claims

1. A method for correcting distortion in an image of a scanned document, comprising:

placing a reference pattern on a page;

obtaining an image of said page containing printed information at least a portion of which is distorted;

detecting said reference pattern in the image indicative of the distortion;

computing an amount of the distortion in said image by analyzing the detected reference pattern; and

correcting the distortion in said image based on the amount of distortion computed in said computing step,

wherein said placing step includes;

attaching a strip of material containing said reference pattern at a predetermined location and predetermined orientation to said page, said obtaining step including scanning said page containing said strip of material into a memory.

2. A method for correcting distortion in an image of a scanned document, comprising:

placing a reference pattern on a page;

obtaining an image of said page containing printed information at least a portion of which is distorted;

detecting said reference pattern in the image indicative of the distortion;

computing an amount of the distortion in said image by analyzing the detected reference pattern; and

correcting the distortion in said image based on the amount of distortion computed in said computing step,

wherein said placing step includes;

attaching a plurality of strips of material at predetermined locations and predetermined orientations to said page, one of said strips of material containing said reference pattern and another of said strips containing a second reference pattern, said obtaining step including scanning said page containing said plurality of strips of material into a memory.

3. The method of claim 2, wherein said detecting step includes detecting said second reference pattern,

wherein said computing step includes computing an amount of distortion in said image by analyzing said reference pattern and said second reference pattern, and

wherein said correcting step includes correcting distortion in said image based on the amount of distortion computed in said computing step.

4. A distortion correction processor adapted for use with a digital imaging device, said distortion correction processor comprising:

an optical recognition unit which locates a reference pattern on a page in the form of a strip of material having a predetermined location and predetermined orientation in a document image;

a distortion computation unit which determines an amount of the distortion in said image by analyzing said reference pattern; and

a bitmap processor which corrects the distortion in said image based on the amount of distortion computed by the distortion computation unit.

5. The distortion correction processor of claim 4, wherein reference pattern is located at a predetermined position within said image.

6. The distortion correction processor of claim 4, wherein said reference pattern includes a series of markings having a predetermined spatial relationship.

7. The distortion correction processor of claim 6, wherein said series of markings are a series of equidistantly spaced bars.

8. The distortion correction processor of claim 4, wherein said optical recognition unit locates a second reference pattern in said document image at a second location within said image,

wherein said distortion computation unit computes an amount of the distortion in said image by analyzing said reference pattern and said second reference pattern, and

wherein said bitmap processor corrects distortion in said image based on the amount of distortion computed by said distortion computation unit.

9. A digital imaging system, comprising:

a document having a strip of material containing a reference pattern at a predetermined location and predetermined orientation on a page of said document;

an optical scanner which scans said document to obtain an image, said image containing distortion resulting from curvature of said document on a support surface of said optical scanner;

a distortion correction processor which receives said image from said optical scanner, said distortion correction processor including;

(a) an optical recognition unit which locates said reference pattern in said image,

(b) a distortion computation unit which determines an amount of the distortion in said image by analyzing said reference pattern,

(c) a bitmap processor which corrects the distortion in said image based on the amount of distortion computed by the distortion computation unit; and

an output unit for outputting the corrected image to an output device.