Method and apparatus for decoding handwritten characters

• US 20050175241A1
• Filed: 10/15/2002
• Published: 08/11/2005
• Est. Priority Date: 10/15/2001
• Status: Active Grant

• Current Assignee: Silverbrook Research Pty Limited
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Napper, Jonathon Leigh
• Granted Patent: US 7,359,551 B2
• Time in Patent Office: Days
• US Class Current: 382/186
• CPC Class Codes: G06V 30/1423 the instrument generating sequences of position coordinates corresponding to handwriting preprocessing or recognising digital ink G06V30/32
• CPC Class Codes: G06V 30/244 using graphical properties, e.g. alphabet type or font

Abstract

Disclosed is a method of performing written character recognition, including sequentially comparing a given input character with one of a series of stored character models. The step of comparing further includes the steps of: decomposing the given input character into one or more segments in accordance with a segmentation scheme associated with the present character model; evaluating the segment or segments against a segment model associated with the present character model, such that the evaluation produces a score which measures the degree of conformity with the model; repeating said step of comparing for a plurality of character models in the series of character models; and selecting the character model which is assigned the highest score and classifying the input character as the character associated with that character model.

Claims

1. A method of performing written character recognition, including sequentially comparing a given input character with one of a series of stored character models, wherein the step of comparing further includes the steps of:

decomposing the given input character into one or more segments in accordance with a segmentation scheme associated with the present character model;

evaluating said segment or segments against a segment model associated with the present character model, such that the evaluation produces a score which measures the degree of conformity with the model;

repeating said step of comparing for a plurality of character models in the series of character models; and

selecting the character model which is assigned the highest score and classifying the input character as the character associated with that character model.

2. A method as claimed in claim 1 wherein the character for recognition is one of a letter, a number or a punctuation mark.

3. A method as claimed in claim 1 or claim 2 wherein the step of decomposing the input character into one or more segments is performed such that each segment has a minimum length according to the following equation:

$l_{\text{\hspace{1em}<br><br>}<br><br>\min }=\mathrm{\lambda <br><br>}<br><br>\underset{i=2}{\overset{n}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br><br><br>p_i-p_{i-1}<br><br>$

where

l_min=minimum length of segment

p_i=coordinates of point i

n=number of points in the stroke

λ

=minimum length threshold

4. A method as claimed in any one of the preceding claims wherein if the given input character can not be segmented according to the segmentation scheme associated with the present character model, then the present character model is rejected as a possible match for the given input character.

5. A method as claimed in any one of the preceding claims wherein the evaluation procedure assigns a score which rewards closer conformance to an ideal.

6. A method as claimed in claim 5 wherein the evaluation procedure uses fuzzy logic rules.

7. A method as claimed in any one of the preceding claims wherein each character model may have associated with it a plurality of segmentation schemes to facilitate recognition of different forms of the same character.

8. A method as claimed in any one of the preceding claims wherein different rules for decomposing the input character into one or more segments may be defined for different character models.

9. Apparatus for performing handwritten character recognition, the apparatus including:

an input surface responsive to the movement of a stylus thereupon for producing an input stimulus;

a memory;

a processor for receiving said input stimulus and processing said input stimulus, wherein said processor is adapted to perform the method in accordance with any one of claims 1 to 8.