Character input apparatus/method and computer-readable storage medium

• US 6,694,056 B1
• Filed: 10/12/2000
• Issued: 02/17/2004
• Est. Priority Date: 10/15/1999
• Status: Expired due to Term

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Ito, Yoshikatsu, Nakao, Ichiro
• Primary Examiner(s): CHANG, JON CARLTON
• Application Number:
  US09/686,968
• Time in Patent Office: 1,223 Days
• Field of Search: 382/185, 382/186, 382/187, 382/188, 382/189, 382/209, 382/217, 382/218
• 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

Abstract

A character input apparatus accurately recognizes handwritten characters drawn one after another in a single input frame. A stroke matching unit obtains stroke information for each stroke in the inputted handwritten characters from the start/end area of the stroke in the input frame and the direction of the stroke, and detects stroke candidates for the stroke by comparing the stroke information with each set of stroke information in the stroke dictionary. An interval-based character detecting unit detects character candidates from detected stroke candidates by referring to the character dictionary that stores an stroke order for each character. With this construction, the apparatus is capable of accurately recognizing a plurality of characters drawn one after another in a single input frame.

Claims

1. A character input apparatus comprising:

a stroke dictionary in which sets of standard stroke information for a plurality of strokes are registered, each of the sets of standard stroke information corresponding to a different stroke;

a character dictionary in which stroke orders for a plurality of characters are registered, each of the stroke orders corresponding to a different character;

a coordinate output unit operable to output, when a user inputs handwritten characters, a coordinate string comprising sets of coordinates of points for each handwritten stroke comprising the handwritten characters;

a stroke matching unit operable to obtain stroke information for each of the handwritten strokes from the outputted coordinate string of the handwritten strokes, compare the stroke information with each of the sets of standard stroke information registered in said stroke dictionary, and output a plurality of stroke candidates; and

a character detecting unit operable to search said character dictionary using an order of a group of the stroke candidates obtained in inputted order by said stroke matching unit as a key and detect a character whose stroke order matches the order of the stroke candidates.

2. The character input apparatus of claim 1,

wherein the standard stroke information includes a start position, an end position, each direction, and a number of directions for each stroke, and

wherein said stroke matching unit comprises:

a stroke information obtaining unit operable to obtain the stroke information which includes a start position, an end position, each direction, and a number of directions for a stroke from the outputted coordinate string of the handwritten strokes;

a stroke candidate output unit operable to compare the obtained stroke information with each of the sets of standard stroke information and output the plurality of stroke candidates; and

an evaluation value adding unit operable to add an evaluation value to each of the plurality of stroke candidates according to a degree of matching between the obtained stroke information and the standard stroke information of each of the plurality of stroke candidates, and

wherein said character detecting unit comprises;

a character candidate detecting unit operable to ignore stroke candidates with the evaluation value showing a poor match and detect character candidates using remaining stroke candidates; and

a correct character detecting unit operable to detect a correct character out of the detected character candidates.

3. The character input apparatus of claim 2, further comprising

a coordinate string detecting unit operable to detect coordinate strings, out of the coordinate strings outputted by said coordinate output unit, that are inputted at least a predetermined time after an immediately preceding coordinate string,

wherein said character candidate detecting unit detects the character candidates by setting the stroke candidates corresponding to the coordinate strings detected by said coordinate string detecting unit as first strokes of characters.

4. The character input apparatus of claim 3, wherein said correct character detecting unit comprises:

a word dictionary in which character orders for a plurality of words are registered, each of the character orders corresponding to a different word; and

a word detecting unit operable to detect, when either one of the character candidates detected by said character candidate detecting unit or a combination of the character candidates is registered in said word dictionary, a corresponding word as the inputted handwritten characters.

5. The character input apparatus of claim 2, further comprising:

a word dictionary in which character orders for a plurality of words are registered, each of the character orders corresponding to a different word; and

a word detecting unit operable to detect, when either one of the character candidates detected by said character candidate detecting unit or a combination of the character candidates is registered in said word dictionary, a corresponding word as the inputted handwritten characters.

6. The character input apparatus of claim 2, wherein said correct character detecting unit comprises:

a probability dictionary for showing a numeric value of a probability of each pair of adjacent characters appearing in a character string;

a high probability character detecting unit operable to generate character strings by combining the character candidates detected by said character candidate detecting unit without changing an order of the character candidates, calculate a value for each of the character strings by summing up the numeric values of the probability for pairs of adjacent characters that constitute a character string and dividing the sum by a number of characters that constitute the character string, and detect a character string with a highest value as the inputted handwritten characters.

7. The character input apparatus of claim 1, further comprising

a coordinate string detecting unit operable to detect coordinate strings, out of the coordinate strings outputted by said coordinate output unit, that are inputted at least a predetermined time after an immediately preceding coordinate string,

wherein said character detecting unit comprises:

a character candidate detecting unit operable to detect a plurality of character candidates by setting the plurality of stroke candidates corresponding to the coordinate strings detected by said coordinate string detecting unit as first strokes of characters; and

a correct character detecting unit operable to detect the character as a correct character out of the plurality of detected character candidates.

8. The character input apparatus of claim 1, wherein said character detecting unit comprises:

a character candidate detecting unit operable to detect a plurality of character candidates;

a word dictionary in which character orders for a plurality of words are registered, each of the character orders corresponding to a different word; and

a word detecting unit operable to detect, when either one of the character candidates detected by said character candidate detecting unit or a combination of the character candidates is registered in said word dictionary, a corresponding word as the inputted handwritten characters.

9. The character input apparatus of claim 1, wherein said character input apparatus is operable to be set to a learning mode for learning handwritten characters,

wherein when said character input apparatus is in learning mode, said stroke matching unit adds an evaluation value to each stroke candidate according to a degree of matching between the obtained stroke information and the standard stroke information of the stroke candidate registered in said stroke dictionary, and

wherein said character input apparatus further comprises:

a stroke dictionary additional register unit operable to additionally register, when the evaluation value for a stroke candidate is smaller than a predetermined evaluation value which shows a poor match, the stroke information for the stroke candidate as the standard stroke information in said stroke dictionary; and

a character dictionary additional register unit operable to additionally register a stroke order that includes the stroke candidate for a character to be learned in said character dictionary.

10. The character input apparatus of claim 1, wherein

said stroke dictionary stores each of the sets of standard stroke information together with a flag that indicates whether each of the plurality of strokes has a possibility of being a first stroke of a character, and

said stroke matching unit compares the stroke information obtained from a first coordinate string outputted by said coordinate output unit only with the stroke information having the flag that indicates a first stroke in said stroke dictionary.

11. The character input apparatus of claim 1, further comprising

a coordinate string detecting unit operable to detect coordinate strings, out of the coordinate strings outputted by said coordinate output unit, that are inputted at least a predetermined time after an immediately preceding coordinate string,

wherein said stroke dictionary stores each of the sets of standard stroke information together with a flag that indicates whether each of the plurality of strokes has a possibility of being a first stroke of a character, and

said stroke matching unit compares stroke information obtained from a first coordinate string outputted by said coordinate output unit only with stroke information having the flag that indicates a first stroke in said stroke dictionary.

12. The character input apparatus of claim 1, wherein

said stroke matching unit comprises:

an overlap detecting unit operable to detect from the coordinate string outputted by said coordinate output unit whether a stroke has a line segment that partially or completely overlaps another stroke preceding the stroke, and

if said overlap detecting unit detects overlapping strokes, said character detecting unit treats the latter of the overlapping strokes as belonging to a different character than the former stroke.

13. The character input apparatus of claim 1, further comprising,

an off-stroke information detecting unit operable to detect off-stroke information from an end point of one coordinate string and a start point of a following coordinate string outputted by said coordinate output unit,

wherein said character dictionary further stores, when a character is composed of a plurality of strokes, off-stroke information that shows a relationship between an end point of one stroke and a start point of a following stroke, and

wherein when said character detecting unit detects characters from the plurality of stroke candidates outputted by said stroke matching unit, if the off-stroke information detected by said off-stroke information detecting unit differs from the corresponding off-stroke information of a character of the plurality of characters registered in said character dictionary by at least a predetermined amount, said character detecting unit does not detect the character.

14. The character input apparatus of claim 1, wherein said character detecting unit comprises:

a character candidate detecting unit operable to detect a plurality of character candidates; and

a shortest character string detecting unit operable to generate character strings by combining the plurality of character candidates detected by said character candidate detecting unit without changing an order of the plurality of character candidates and detect a character string which has a smallest number of characters as the inputted handwritten characters.

15. A character input method comprising:

a coordinate output operation for outputting, when a user inputs handwritten characters, a coordinate string comprising sets of coordinates of points for each handwritten stroke comprising the handwritten characters;

a stroke matching operation for obtaining stroke information for each handwritten stroke from the outputted coordinate string of the handwritten stroke, comparing the stroke information with each set of standard stroke information registered in a stroke dictionary, and outputting stroke candidates; and

a character detecting operation for browsing orders of strokes for characters registered in a character dictionary using an order of a group of the stroke candidates obtained in inputted order in said stroke matching operation as a key and detecting a character whose stroke order matches the order of the stroke candidates.

16. A program stored on a computer-readable storage medium for use with a computer, the computer-readable storage medium also having a stroke dictionary in which sets of standard stroke information for a plurality of strokes are registered, each of the sets of standard stroke information corresponding to a different stroke, and a character dictionary in which stroke orders for a plurality of characters are registered, each of the plurality of stroke orders corresponding to a different character, stored thereon, said program comprising:

coordinate output program code operable to output, when a user inputs handwritten characters, a coordinate string comprising sets of coordinates of points for each handwritten stroke comprising the handwritten characters;

stroke matching program code operable to obtain stroke information for each handwritten stroke from the outputted coordinate string of the handwritten stroke, compare the stroke information with each of the sets of stroke information registered in the stroke dictionary, and output stroke candidates; and

character detecting program code operable to search the character dictionary using an order of a group of the stroke candidates obtained in inputted order by said stroke matching program code as a key, and detect a character whose stroke order matches the order of the stroke candidates.