US 5,694,494 AGranted

Electronic retrieval of information from form documents

AssigneeRicoh Company, Ltd.

InventorsPeter Hart, Mark Peairs, Mitsutoshi Mizutani

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Abstract

A method for retrieving user-supplied information from a scanned version of a completed document is described. The method includes the steps of obtaining a first image of the document having information printed thereon in its blank format before other information has been added to it by the user. A second image of the document is obtained after information has been added to it by the user. The two images are aligned, and for each pixel in the first image which corresponds to information on the document, those pixels are deleted from the second image to create an image which corresponds to subtraction of the first image from the second image. Finally, a step is performed to electronically restore the information added by the user which was deleted during the subtraction operation.

Claims25

Dependent claims

A method of electronically distinguishing information added to a form document from the form document itself, and of retrieving the information from said form document, the method comprising the steps of:

obtaining a first digital image of a form document to produce a first array of pixels representing printed areas of said form document, wherein each pixel of said first array of pixels has a pixel location and a pixel value;
obtaining a second digital image of said form document having information added thereto to produce a second array of pixels representing printed areas of said form document and added information, wherein each pixel in said second array of pixels has a pixel location and a pixel value;
identifying a subset of pixels in said second array which correspond to said first array of pixels by aligning the pixel locations of said first array of pixels with said second array of pixels;
deleting the pixel value of each pixel in said subset of pixels, irrespective of whether any of said subset of pixels also correspond to said added information;
designating as "unknown" the pixel value of those pixels whose pixel values were deleted in said deleting step, thereby producing a set of dropout pixels;
and
estimating a pixel value for one or more pixels in said set of dropout pixels to produce a third digital image representing said added information apart from said form document itself.

4 more elements

A computing system for restoring pixels in an image represented by pixels having known pixel values and pixels to be restored having unknown pixel values, the system comprising:

(a) means for obtaining, external to the image, an indication of which pixels have unknown pixel values;
(b) means for specifying a threshold value, a neighborhood configuration and a desired quantity of unrestored pixels, wherein the neighborhood configuration defines a window;
(c) means, coupled to said means for obtaining and said means for specifying, for restoring each pixel having an unknown pixel value, including:
(1) means for positioning the window relative to the pixel to be restored;
(2) means for counting a number of pixels having known values in the window to obtain a known pixel count;
(3) means for comparing the known pixel count to said threshold value;
(4) means, coupled to the means for comparing the known pixel count, for calculating a restored pixel value when the known pixel value exceeds said threshold value, wherein the restored pixel value is calculated as a function of the pixel values of the pixels in the window having known pixel values;
(4) means, coupled to the means for comparing, assigning the restored pixel value to the pixel to be restored when the known pixel count exceeds the threshold value;
and
(5) means for determining when no pixels having unknown values whose known pixel count exceeds the threshold value remain;
(6) means, coupled to said means for determining, for repeating the operation of the means for positioning, the means for counting, the means for comparing, the means for calculating, the means for assigning, and the means for determining, until no pixels having unknown values whose known pixel count exceeds the threshold value remain;
(d) means for comparing a number of unrestored pixels having an unknown value to the desired quantity of unrestored pixels;
and
(e) means, coupled to the means for comparing a number of unrestored pixels and the means for restoring, for selectively adjusting the threshold value, and for repeating the operation of the means for restoring until the number of pixels having unknown values is less than the desired quantity of unrestored pixels.

11 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/712,663Filed 13 Sep 1996 · continuation
Priority: 12 Apr 1993
Granted: 2 Dec 1997
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

G06T 5/20
Image enhancement or restoration: using local operators
G06V 30/155
Segmentation of character regions: removing patterns interfering with the pattern to be recognised, such as ruled lines or underlines
G06V 30/10
Character recognition; Recognising digital ink; Document-oriented image-based pattern recognition: character recognition
G06T
Image data processing or generation, in general