US 2001/0033688 A1Published application

Method of optical mark recognition

AssigneeTms Co., Ltd.

InventorGarland S. Taylor

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Abstract

There is provided herein a new method of identifying when a particular hand-drawn selection has been made on, for example, a standardized test form. This method does not require the use of any particular form nor does it use registration marks. It is robust enough to be used when the form is somewhat misaligned on the scanning device. This method utilizes a scanned “blank” form which is then compared with a form containing user markings thereon. As a first step, the user's form is mathematically iteratively aligned with the scanned blank form. As a next step, a fine-scale refinement is applied to each individual “bubble” (i.e., response field) of the user's form to bring that feature into near exact alignment with the same bubble on the blank form. Finally, a quantitative measure of the similarity between the blank and user forms is used to determine whether or not the user has made a mark on the form within that response region.

Claims37

Dependent claims

A method of aligning a user-marked document for optical mark recognition, wherein is provided a reference document and at least one target document, comprising the steps of:

(a) selecting one of said at least one target documents;
(b) obtaining a digital representation of said selected target document, thereby obtaining a digital target document;
(c) obtaining a digital representation of said reference document at a predetermined digital resolution, thereby obtaining a digital reference document;
(d) selecting a reference region within said digital reference document, said reference region
(d1) corresponding to a predetermined portion of said reference document,
(d2) having a predetermined location within said digital reference document, and,
(d3) containing a plurality of reference pixels therein;
(e) selecting a target region of said digital target document, said target region
(e1) having a location at least approximately corresponding to said predetermined location within said digital reference document, and,
(e2) having a plurality of target pixels contained therein;
(f) determining from said reference pixels and said target pixels an offset between said reference region and said target region;
(g) performing steps (c) through (f) at least once;
(h) calculating an image adjustment rule from any offsets so calculated;
(i) applying said image adjustment rule, thereby at least approximately aligning said digital reference document and said selected digital target document;
(j) performing steps (c) through (i) at least twice using at least two different digital resolutions;
and,
(k) determining from said digital target document, said digital reference document, and from any adjustment rules so calculated whether said user-marked document contains a user mark within a predetermined region of said user-marked document.

14 more elements

A method of aligning a user-marked document for optical mark recognition, wherein is provided a reference document and at least one target document, comprising the steps of:

(a) selecting one of said at least one target documents;
(b) obtaining a digital representation of said selected target document, thereby obtaining a digital target document;
(c) obtaining a digital representation of said reference document, thereby obtaining a digital reference document;
(d) selecting a reference region within said digital reference document, said reference region
(d1) corresponding to a predetermined portion of said reference document,
(d2) having a predetermined location within said digital reference document, and,
(d3) containing a plurality of reference pixels therein;
(e) selecting a target region of said digital target document, said target region
(e1) having a location at least approximately corresponding to said predetermined location within said digital reference document, and,
(e2) having a plurality of target pixels contained therein;
(f) selecting a trial offset;
(g) calculating a numerical distance between a plurality of said reference pixels and a corresponding plurality of said target pixels using said trial offset;
(h) performing steps (f) and (g) a plurality of times, using at least two different trial offsets;
(i) determining from any numerical distances so calculated an offset between said reference pixels and said target pixels;
(j) performing steps (e) through (i) at least once,
(k) calculating an image adjustment rule from any offsets so determined;
and,
(l) determining from said digital target document, said digital reference document, and from any adjustment rules so calculated whether said user-marked document contains a user mark within a predetermined region of said user-marked document.

15 more elements

A method of optical mark recognition wherein is provided

a reference document containing at least one reference bubble, and
at least one user-marked target document, each of said at least one user-marked target documents containing a target bubble corresponding to said reference bubble therein, and each of said user-marked target documents containing at least one marked target bubble marked by a user therein,
comprising the steps of:
(a) selecting one of said at least one target documents, said selected target document containing a selected target bubble therein;
(b) obtaining a digital representation of a region containing substantially all of said selected target bubble, thereby obtaining a digital target region, said digital target region containing target pixels therein;
(c) obtaining a digital representation of a region containing said reference bubble, thereby obtaining a digital reference bubble, said digital reference bubble containing reference pixels therein;
(d) selecting a pixel from among said reference pixels, said selected reference pixel having a particular location within said digital reference bubble;
(e) selecting a region within said digital target region and said target pixels therein, thereby producing a plurality of selected target pixels, said selected region corresponding at least approximately to said particular location within said digital reference bubble;
(f) calculating a numerical difference between said selected reference pixel and each of said selected target pixels, thereby producing a plurality of difference pixels;
(g) determining from said plurality of difference pixels a similarity value;
(h) performing steps (d) through (g) at least twice for at least two different selected reference pixels, thereby producing a plurality of similarity values;
and,
(i) determining from said plurality of similarity values whether said selected target bubble is a user-marked target bubble.

10 more elements

A method of normalizing the relative intensity levels of one document with respect to another for use in OMR, wherein is provided

a reference document containing a plurality of reference regions therein, and
a target document, said target documents containing a corresponding plurality of target regions therein, each of said target regions corresponding to one of said reference regions,
comprising the steps of:
(a) selecting a reference region in said reference document;
(b) selecting a target region in said target document corresponding to said selected reference region, said target region having a target location within said target document;
(c) obtaining a digital representation of said reference region, thereby obtaining a digital reference region, said digital reference region containing reference pixels therein, and said reference region having a reference location within said reference document;
(d) obtaining a digital representation of said target region, thereby obtaining a digital reference region, said digital reference region containing reference pixels therein;
(e) determining an intensity level of said digital target region;
(f) determining an intensity level of said digital reference region;
(g) calculating an intensity differential between said intensity level of said digital target region and said intensity level of said digital reference region;
(h) performing steps (a) though (g) at least twice, thereby producing a plurality of intensity differentials;
(i) calculating a difference map using at least said plurality of intensity differentials together with any of said reference locations or said target locations;
(j) obtaining a digital representation of said reference document, thereby producing a digital reference document;
(k) obtaining a digital representation of said target document, thereby producing a digital target document;
and,
(l) modifying at least a portion of said digital target document according to said difference map, thereby at least approximately normalizing said digital target document relative to said digital reference document.

13 more elements

Dependencies are inferred from the claim text.