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Questionnaire scanning system employing expandable answer mark areas for efficient scanning and mark detection

  • US 5,229,589 A
  • Filed: 11/21/1991
  • Issued: 07/20/1993
  • Est. Priority Date: 11/21/1991
  • Status: Expired due to Fees
First Claim
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1. A system for scanning a questionnaire for answer marks written thereon, said questionnaire comprised of at least one page having preprinted data thereon, comprising:

  • image scanning means for initializing an unmarked questionnaire by scanning each unmarked page to create a pixel map thereof;

    selecting means for defining selecting alignment points at one or more locations on each said page and detectible on said pixel map;

    means for defining, on each said unmarked page, at least one area of interest within which is located an answer mark area location;

    means for storing alignment point identifying data and area of interest location data;

    said image scanning means including means for scanning a marked, completed questionnaire page for answer marks thereon and creating a pixel map of said completed page;

    location means for locating the alignment points on said completed page pixel map;

    comparator means for comparing the locations of said alignment points of said completed page pixel map with the locations of corresponding alignment points of said unmarked page pixel map to determine an alignment point shift required to correct for positional offset of the completed page from the unmarked page and true positions of the stored alignment points;

    location adjustment means for correcting said area of interest location data by applying said alignment point shift to thereby provide a coarse adjustment of the stored locations of areas of interest to their new positions on the scanned completed pages; and

    image differencing means, employing said adjusted stored locations of said areas of interest, for subtracting data of the stored areas of interest of the unmarked page pixel map from the data of the areas of interest of the scanned completed page pixel map to remove the common preprinted areas from the scanned completed page to detect any new answer marks.

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