Apparatus for recognizing input character strings by inference

• US 6,097,841 A
• Filed: 05/20/1997
• Issued: 08/01/2000
• Est. Priority Date: 05/21/1996
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Miura, Masaki, Yokota, Toshimi, Katsura, Koyo, Kuzunuki, Soshiro, Gunji, Keiko
• Primary Examiner(s): MEHTA, BHAVESH M
• Application Number:
  US08/859,410
• Time in Patent Office: 1,169 Days
• Field of Search: 382/228, 382/229, 382/230, 382/231
• US Class Current: 382/229
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/262 using context analysis, e.g. lexical, syntactic or semantic context
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99933 Query processing, i.e. searching

Abstract

A character recognition apparatus for inferring the entire character string solely from a user-input handwritten keyword and displaying the inferred result as a candidate character string. The apparatus of the invention comprises: a word dictionary storing word identification information and hierarchy information for layering a plurality of words into a hierarchy and for recognizing each of the words within the hierarchy; a character transition probability table a4 storing probabilities of transitions from any one character to another, and those pieces of the word identification information which correspond to combinations of characters resulting from the transitions; and an optimization unit for using the character transition probability table in optimizing candidate character strings obtained by a recognition unit. The word dictionary is searched for a word defined by the word identification information which corresponds to the optimized candidate character string, whereby the searched word is retrieved which applies to the hierarchy information and which has yet to be input.

Claims

1. A character recognition apparatus having recognition means for recognizing input character strings and display means for displaying recognized results, said character recognition apparatus comprising:

a word dictionary storing word identification information and hierarchy information for layering a plurality of words into a hierarchy and for recognizing each of said words within said hierarchy;

a character transition probability table storing at least probabilities of transitions from any one character to another, and those pieces of said word identification information which correspond to combinations of characters resulting from said transitions;

optimization means for using said character transition probability table in optimizing candidate character strings obtained by said recognition means; and

retrieval means for searching through said word dictionary for words defined by those pieces of said word identification information which correspond to the optimized candidate character string, thereby retrieving the searched words which are identified by the applicable pieces of said hierarchy information and which have yet to be input.

2. A character recognition apparatus according to claim 1, wherein said hierarchy information is constituted by word identification information about the words higher in hierarchy than each of the words in said word dictionary.

3. A character recognition apparatus according to claim 2, wherein said retrieval means retrieves, as yet-to-be input words, words higher in hierarchy than those of said optimized character string from said word dictionary.

5. A character recognition apparatus according to claim 1 or 4, wherein said recognition means selects, from among a plurality of candidate character strings obtained by said recognition means, the candidate character string in which the probabilities of transitions from one character to another are higher than any other candidate character strings, whereby the optimized candidate character string is determined.

6. A character recognition apparatus according to claim 1 or 4, said character strings are handwritten for input.

7. A character recognition apparatus according to claim 1 or 4, said character strings are input by voice.

4. A character recognition apparatus having recognition means for recognizing input character strings and display means for displaying recognized results, said character recognition apparatus comprising:

a dictionary having each of a plurality of character strings stored beforehand at a specific address;

a character transition probability table storing at least probabilities of transitions from any one character to another, said probabilities being stored in correspondence with the addresses of those of said character strings which include combined characters involved in said transitions; and

optimization means for using said character transition probability table in optimizing candidate character strings obtained by said recognition means;

wherein said dictionary is accessed for the addresses of the character strings corresponding to the optimized candidate character string, and wherein the character strings at said addresses in said dictionary are displayed as recognized results.

8. A pattern recognition apparatus having input means for inputting character patterns, recognition means for recognizing input character patterns, and display means for displaying recognized results, said pattern recognition apparatus comprising:

a word dictionary having a plurality of words stored beforehand;

a character transition probability table describing previously learned probabilities of transitions from any one character to another, and pointers to those words in said word dictionary which include said transitions;

pointer determination means for optimizing recognized candidate character strings based on said probabilities of said transitions and for detecting pointers to those words in said word dictionary which include the character-to-character transitions of said recognized candidate character strings; and

inference means for matching the optimized candidate character string with those words in said word dictionary which are referenced by the corresponding pointers, and for inferring information about the referenced words from within said word dictionary.

9. A pattern recognition apparatus according to claim 8, wherein the words in said word dictionary are constituted by hierarchical data.

10. A pattern recognition apparatus according to claim 8, wherein said character patterns are handwritten for input, and wherein the candidate character strings inferred by said inference means are displayed in the vicinity of the handwritten input character patterns.

11. A pattern recognition apparatus according to claim 10, wherein, of the candidate character strings, those corresponding to said handwritten input character patterns are displayed either in reverse video or in a different font.

12. A pattern recognition method for recognizing input character patterns and displaying recognized results, said pattern recognition method comprising the steps of:

extracting candidate character strings from an input character pattern recognized;

optimizing the extracted candidate character strings by use of a character transition probability table describing previously learned probabilities of transitions from any one character to another, the probabilities being stored in correspondence with pointers to those words in a word dictionary which include said transitions;

detecting pointers to those words in said word dictionary which include the character-to-character transitions of the optimized candidate character string;

matching said optimized candidate character string with those words pointed to by the detected pointers from among said plurality of words stored in said word dictionary; and

inferring information about the words in question from said word dictionary in order to display inferred results as the candidate character strings.

13. A pattern recognition method according to claim 12, wherein the words in said word dictionary are constituted by hierarchical data.

14. A pattern recognition method according to claim 12, wherein said character patterns are handwritten for input, and wherein the inferred candidate character strings are displayed in the vicinity of the handwritten input character patterns.

15. A pattern recognition method according to claim 14, wherein, of the candidate character strings, those corresponding to said handwritten input character patterns are displayed either in reverse video or in a different font.