US5933525A
Expired / Lapsed
US
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Language-independent and segmentation-free optical character recognition system and method
Assignee: RTX BBN Technologies Corp
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Filing: 1996-04-10
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Granted: 1999-08-03
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Expires: 2016-04-10
Abstract
Abstract A language-independent and segment free OCR system and method comprises a unique feature extraction approach which represents two dimensional data relating to OCR as one independent variable (specifically the position within a line of text in the direction of the line) so that the same CSR technology based on HMMs can be adapted in a straightforward manner to recognize optical characters. After a line finding stage, followed by a simple feature-extraction stage, the system can utilize a commercially available CSR system, with little or no modification, to perform the recognition of text by and training of the system. The whole system, including the feature extraction, training, and recognition components, are designed to be independent of the script or language of the text being recognized. The language-dependent parts of the system are confined to the lexicon and training data. Furthermore, the method of recognition does not require pre-segmentation of the data at the character and/or word levels, neither for training nor for recognition. In addition, a language model can be used to enhance system performance as an integral part of the recognition process and not as a post-process, as is commonly done with spell checking, for example.
Inventors
- 👤 John I. Makhoul
- 👤 Richard M. Schwartz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 23:56
CPC Classifications
G; G06; G06V; G06V30/00; G06V30/10; G06V30/22; G06V30/226; G06V30/2268; G06V30/2276
Claims Analysis
Total Claims: 42
Claim 1
Independent Claim
132 words
An optical character recognition system for recognizing each character of a text, comprising: means for (a) determining the position of each line of characters of the text, (b) scanning each line of text by scanning said text in successive frames of a predetermined height and width independent of the script and language of said text, and (c) generating data representing all of the optically scanned characters of the text as a function of a single independent variable in one direction, said variable being a function of a feature vector representing a plurality of elements, each element being a function of the percentile height below which a prespecified percentage of black pixels lies; means for providing a probabilistic paradigm so as to determine each of said characters of said text from said data.
Claim 2
Dependent Claim
132 words
An optical character recognition system for recognizing each character of a text, comprising: means for (a) determining the position of each line of characters of the text, (b) scanning each line of text by scanning said text in successive frames of a predetermined height and width independent of the script and language of said text, and (c) generating data representing all of the optically scanned characters of the text as a function of a single independent variable in one direction, said variable being a function of a feature vector representing a plurality of elements, each element being a function of the percentile height below which a prespecified percentage of black pixels lies; means for providing a probabilistic paradigm so as to determine each of said characters of said text from said data.
Claim 3
Dependent Claim
42 words
The optical character recognition system of claim 1, wherein: said means for generating data representing optically scanned text as a function of a single independent variable comprises means for scanning said text line by line in the same direction as said line.
Claim 4
Dependent Claim
59 words
The optical character recognition system of claim 2 wherein: said means for scanning said text line by line in the same direction as said line includes means for scanning said text in successive frames of a predetermined height and width independent of the script and language of said text, but a function of the font size of the characters.
Claim 5
Dependent Claim
44 words
The optical character recognition system of claim 3, wherein: said means for scanning said text in successive frames of a predetermined height and width independent of the script and language of said text includes means for scanning said text so that said frames overlap.
Claim 6
Dependent Claim
48 words
The optical character recognition system of claim 4, wherein: said means for scanning said text in successive frames of a predetermined height and width independent of the size, shape and width of the font of said text includes means for dividing said frame into a plurality of cells.
Claim 7
Dependent Claim
37 words
The optical character recognition system of claim 5, further including: means for dividing said frame into a plurality of cells so that said cells are aligned along an axis perpendicular to the direction of scanning said text.
Claim 8
Dependent Claim
29 words
The optical character recognition system of claim 6, wherein: said means for dividing said frame into a plurality of cells divides said cells so that said cells are overlapping.
Claim 9
Dependent Claim
63 words
The optical character recognition system of claim 3, further including: means for dividing each of said frames into an array of pixels, and wherein said means for generating data representing optically scanned text as a function of a single independent variable includes means for generating the data as a function of the intensity in each of said pixels in each of said frames.
Claim 10
Dependent Claim
69 words
The optical character recognition system of claim 8, further including means for dividing said frame into a plurality of cells so that said cells are aligned along an axis perpendicular to the direction of scanning said text; and means for determining the percentage of said pixels below a predetermined threshold within each of said cells relative to the total number of pixels below a predetermined threshold within said frame.
Claim 11
Dependent Claim
76 words
The optical character recognition system of claim 9, wherein said means for determining the percentage of said pixels below a predetermined threshold within each of said cells relative to the total number of cells below a predetermined threshold within said frame includes means for determining the percentile of said pixels below a predetermined threshold within each of said cells relative to the total number of pixels between said cell and one referenced end of said frame.
Claim 12
Dependent Claim
46 words
The optical character recognition system of claim 5, wherein said means for generating data representing optically scanned text as a function of a single independent variable also includes means for generating the data as a function of the derivative across the dimensions of a feature vector.
Claim 13
Dependent Claim
45 words
The optical character recognition system of claim 5, wherein said means for generating data representing optically scanned text as a function of a single independent variable also includes means for generating the data as a function of the derivative of each feature across adjacent frames.
Claim 14
Dependent Claim
51 words
The optical character recognition system of claim 6, wherein said means for generating data representing optically scanned text as a function of a single independent variable also includes means for generating the data as a function of the local slope and correlation across a window comprising a plurality of said cells.
Claim 15
Dependent Claim
42 words
The optical character recognition system of claim 1, wherein said means for providing a probabilistic paradigm so as to determine said text from said data includes means for providing a 1D hidden Markov model for each of the characters to be recognized.
Claim 16
Dependent Claim
22 words
The optical character recognition system of claim 14, wherein each of said hidden Markov models is defined by a plurality of states.
Claim 17
Dependent Claim
23 words
The optical character recognition system of claim 15, wherein the number of states for each of said hidden Markov models is the same.
Claim 18
Dependent Claim
24 words
The optical character recognition system of claim 15, wherein the parameters for each of said states of each hidden Markov model is context dependent.
Claim 19
Dependent Claim
24 words
The optical character recognition system of claim 14, further including means for defining a context-dependent character model for each possible character of said text.
Claim 20
Dependent Claim
29 words
The optical character recognition system of claim 1, wherein said means for providing a probabilistic paradigm so as to determine said text from said data includes a language model.
Claim 21
Dependent Claim
16 words
The optical character recognition system of claim 19, wherein said language model is an n-gram model.
Claim 22
Dependent Claim
16 words
The optical character recognition system of claim 20, wherein said language model is a bigram model.
Claim 23
Dependent Claim
16 words
The optical character recognition system of claim 20, wherein said language model is a trigram model.
Claim 24
Dependent Claim
43 words
An optical character recognition system according to claim 1, wherein each of said frames is divided into a plurality of cells, and said means for generating data includes means for determining the vertical derivative of intensity in the vertical direction across said cells.
Claim 25
Dependent Claim
65 words
An optical character recognition system according to claim 23, wherein each of said frames is divided into a plurality of cells, and said means for generating data includes means for determining the vertical derivative of intensity in the vertical direction across said cells, wherein said horizontal and vertical derivatives of intensity provide a measure of boundaries between the light and dark portions of the text.
Claim 26
Dependent Claim
36 words
An optical character recognition system according to claim 1, wherein said frames are overlapping, and said means for generating data includes means for determining the horizontal derivative of intensity in the horizontal direction across overlapping frames.
Claim 27
Dependent Claim
57 words
An optical character recognition system according to claim 1, wherein each of said frames is divided into a plurality of cells, and said means for generating data includes means for determining the local slope and correlation of any line within a window of a plurality of such cells so as to determine the angle of said line.
Claim 28
Dependent Claim
18 words
An optical character recognition system according to claim 1, wherein each of said characters is an Arabic character.
Claim 29
Dependent Claim
18 words
An optical character recognition system according to claim 1, wherein each of said characters is a Chinese character.
Claim 30
Independent Claim
131 words
A method of recognizing text regardless of the script or language of the text and without segmenting the text by character or word, said method comprising: scanning successive frames of a predetermined height and width of each line of the text in the direction of each line so as to generate data relating to all of the characters of the text independent of the script or language of the text, wherein the data is a function of a single independent variable in one direction, said variable being a function of a feature vector representing a plurality of elements, each element being a function of the percentile height below which a prespecified percentage of black pixels lies; and determining from the data each character of text based upon a predetermined probabilistic paradigm.
Claim 31
Independent Claim
131 words
A method of recognizing text regardless of the script or language of the text and without segmenting the text by character or word, said method comprising: scanning successive frames of a predetermined height and width of each line of the text in the direction of each line so as to generate data relating to all of the characters of the text independent of the script or language of the text, wherein the data is a function of a single independent variable in one direction, said variable being a function of a feature vector representing a plurality of elements, each element being a function of the percentile height below which a prespecified percentage of black pixels lies; and determining from the data each character of text based upon a predetermined probabilistic paradigm.
Claim 32
Dependent Claim
15 words
A method according to claim 29, wherein each of said characters is an Arabic character.
Claim 33
Dependent Claim
15 words
A method according to claim 29, wherein each of said characters is a Chinese character.
Claim 34
Dependent Claim
231 words
An optical character recognition system for recognizing each character of a text, comprising: means for (a) determining the position of each line of characters of the text and (b) scanning each line of text; data generating means for generating data representing all of the optically scanned characters of the text as a function of a single independent variable in one direction, said data generating means comprising scanning means for scanning said text (a) line by line in the same direction as said line and (b) in successive frames of a predetermined height and width independent of the script and language of said text, but a function of the font size of the characters; means for dividing each of said frames into an array of pixels; means for dividing said frame into a plurality of cells so that said cells are aligned along an axis perpendicular to the direction of scanning said text; means for determining the percentage of said pixels below a predetermined threshold within each of said cells relative to the total number of pixels below a predetermined threshold within said frame; and means for providing a probabilistic paradigm so as to determine each of said characters of said text from said data; wherein said data generating means includes means for generating the data as a function of the intensity in each of said pixels in each of said frames.
Claim 35
Dependent Claim
231 words
An optical character recognition system for recognizing each character of a text, comprising: means for (a) determining the position of each line of characters of the text and (b) scanning each line of text; data generating means for generating data representing all of the optically scanned characters of the text as a function of a single independent variable in one direction, said data generating means comprising scanning means for scanning said text (a) line by line in the same direction as said line and (b) in successive frames of a predetermined height and width independent of the script and language of said text, but a function of the font size of the characters; means for dividing each of said frames into an array of pixels; means for dividing said frame into a plurality of cells so that said cells are aligned along an axis perpendicular to the direction of scanning said text; means for determining the percentage of said pixels below a predetermined threshold within each of said cells relative to the total number of pixels below a predetermined threshold within said frame; and means for providing a probabilistic paradigm so as to determine each of said characters of said text from said data; wherein said data generating means includes means for generating the data as a function of the intensity in each of said pixels in each of said frames.
Claim 36
Dependent Claim
190 words
An optical character recognition system for recognizing each character of a text, comprising: means for (a) determining the position of each line of characters of the text and (b) scanning each line of text; data generating means for generating data representing all of the optically scanned characters of the text as a function of a single independent variable in one direction, said data generating means comprising scanning means for scanning said text (a) line by line in the same direction as said line, (b) in successive frames of a predetermined height and width independent of the script and language of said text, but a function of the font size of the characters, (c) so that the frames overlap and (d) each of said frames is divided into a plurality of cells; and means for providing a probabilistic paradigm so as to determine each of said characters of said text from said data, wherein said means for generating data representing optically scanned text as a function of a single independent variable also includes means for generating the data as a function of the derivative across the dimensions of a feature vector.
Claim 37
Dependent Claim
190 words
An optical character recognition system for recognizing each character of a text, comprising: means for (a) determining the position of each line of characters of the text and (b) scanning each line of text; data generating means for generating data representing all of the optically scanned characters of the text as a function of a single independent variable in one direction, said data generating means comprising scanning means for scanning said text (a) line by line in the same direction as said line, (b) in successive frames of a predetermined height and width independent of the script and language of said text, but a function of the font size of the characters, (c) so that the frames overlap and (d) each of said frames is divided into a plurality of cells; and means for providing a probabilistic paradigm so as to determine each of said characters of said text from said data, wherein said means for generating data representing optically scanned text as a function of a single independent variable also includes means for generating the data as a function of the derivative across the dimensions of a feature vector.
Claim 38
Dependent Claim
26 words
An optical character recognition system according to claim 33, further including said scanning means including means for dividing each said frame into a plurality of cells.
Claim 39
Dependent Claim
163 words
An optical character recognition system for recognizing each character of a text, comprising: means for (a) determining the position of each line of characters of the text and (b) scanning each line of text; data generating means for generating data representing all of the optically scanned characters of the text as a function of a single independent variable in one direction, said data generating means comprising scanning means for scanning said text (a) line by line in the same direction as said line, (b) in successive frames of a predetermined height and width independent of the script and language of said text, but a function of the font size of the characters, and (c) so that the frames overlap; and means for providing a probabilistic paradigm so as to determine each of said characters of said text from said data, wherein said data generating means includes means for generating the data as a function of the derivative of each feature across adjacent frames.
Claim 40
Dependent Claim
163 words
An optical character recognition system for recognizing each character of a text, comprising: means for (a) determining the position of each line of characters of the text and (b) scanning each line of text; data generating means for generating data representing all of the optically scanned characters of the text as a function of a single independent variable in one direction, said data generating means comprising scanning means for scanning said text (a) line by line in the same direction as said line, (b) in successive frames of a predetermined height and width independent of the script and language of said text, but a function of the font size of the characters, and (c) so that the frames overlap; and means for providing a probabilistic paradigm so as to determine each of said characters of said text from said data, wherein said data generating means includes means for generating the data as a function of the derivative of each feature across adjacent frames.
Claim 41
Dependent Claim
198 words
An optical character recognition system for recognizing each character of a text, comprising: means for (a) determining the position of each line of characters of the text and (b) scanning each line of text; data generating means for generating data representing all of the optically scanned characters of the text as a function of a single independent variable in one direction, said data generating means comprising scanning means for scanning said text (a) line by line in the same direction as said line, (b) in successive frames of a predetermined height and width independent of the script and language of said text, but a function of the font size of the characters, (c) so that the frames overlap, and (d) so that each frame is divided into a plurality of cells so that said cells are aligned along an axis perpendicular to the direction of scanning said text; and means for providing a probabilistic paradigm so as to determine each of said characters of said text from said data; wherein said data generating means includes means for generating the data as a function of the local slope and correlation across a window comprising a plurality of said cells.
Claim 42
Dependent Claim
198 words
An optical character recognition system for recognizing each character of a text, comprising: means for (a) determining the position of each line of characters of the text and (b) scanning each line of text; data generating means for generating data representing all of the optically scanned characters of the text as a function of a single independent variable in one direction, said data generating means comprising scanning means for scanning said text (a) line by line in the same direction as said line, (b) in successive frames of a predetermined height and width independent of the script and language of said text, but a function of the font size of the characters, (c) so that the frames overlap, and (d) so that each frame is divided into a plurality of cells so that said cells are aligned along an axis perpendicular to the direction of scanning said text; and means for providing a probabilistic paradigm so as to determine each of said characters of said text from said data; wherein said data generating means includes means for generating the data as a function of the local slope and correlation across a window comprising a plurality of said cells.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2002-08-02 | 2003-02-01 | 2003-08-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2006-08-02 | 2007-02-01 | 2007-08-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2010-08-02 | 2011-02-01 | 2011-08-03 | $7700.00 | Window Closed / Lapsed |