TRELLIS BASED WORD DECODER WITH REVERSE PASS

• US 20150242710A1
• Filed: 04/28/2015
• Published: 08/27/2015
• Est. Priority Date: 07/19/2012
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Baheti, Pawan Kumar, Barman, Kishor K., Krishna Kumar, Raj Kumar
• Granted Patent: US 9,639,783 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/262 using context analysis, e.g. lexical, syntactic or semantic context

Abstract

Systems, apparatuses, and methods to relate images of words to a list of words are provided. A trellis based word decoder analyses a set of OCR characters and probabilities using a forward pass across a forward trellis and a reverse pass across a reverse trellis. Multiple paths may result, however, the most likely path from the trellises has the highest probability with valid links. A valid link is determined from the trellis by some dictionary word traversing the link. The most likely path is compared with a list of words to find the word closest to the most.

Claims

1. A method to prepare a forward trellis and a reverse trellis in an optical character recognition (OCR) system, the method comprising:

accessing a list of words;

loading the forward trellis using the list of words to form a loaded forward trellis; and

loading the reverse trellis using the list of words to form a loaded reverse trellis.

2. The method of claim 1, wherein the list of words comprise a Devanagari list of words.

3. The method of claim 1, further comprising forming a linking vector that indicates valid and invalid links into a node.

4. The method of claim 1, further comprising, for each node in the forward trellis and the reverse trellis having a previous character position entering the node, forming a linking vector that indicates valid and invalid links into a node.

5. The method of claim 1, further comprising, for each node in the forward trellis and the reverse trellis having a previous character position entering the node, forming a set of words indicating which words from the list of words have a path through the node.

6. The method of claim 1, wherein loading the reverse trellis comprises, for each word in the list of words:

selecting a word from the list of words; and

loading the reverse trellis at;

a first character position with a final character;

a second character position with a second to the final character; and

a third character position with a third to the final character.

7. The method of claim 1, further comprising sending the loaded forward trellis and the loaded reverse trellis to a mobile device.

8. A server to prepare a forward trellis and a reverse trellis in an optical character recognition (OCR) system, the server comprising:

a list of words;

the forward trellis;

the reverse trellis;

a processor coupled to receive the list of words and coupled to load the forward trellis and the reverse trellis, wherein the processor comprises program code to;

access the list of words;

load the forward trellis using the list of words to form a loaded forward trellis; and

load the reverse trellis using the list of words to form a loaded reverse trellis.

9. The server of claim 8, wherein the list of words comprise a Devanagari list of words.

10. The server of claim 8, further comprising a linking vector that indicates valid and invalid links into a node.

11. The server of claim 8, further comprising, for each node in the forward trellis and the reverse trellis having a previous character position entering the node, a linking vector that indicates valid and invalid links into a node.

12. The server of claim 8, further comprising, for each node in the forward trellis and the reverse trellis having a previous character position entering the node, a set of words indicating which words from the list of words have a path through the node.

13. A server to prepare a forward trellis and a reverse trellis in an optical character recognition (OCR) system, the server comprising a processor and a memory, wherein the memory includes software instructions to:

access a list of words;

load the forward trellis using the list of words to form a loaded forward trellis; and

load the reverse trellis using the list of words to form a loaded reverse trellis.

14. A non-transitory computer-readable storage medium including program code stored thereon for a server to prepare a forward trellis and a reverse trellis, the non-transitory computer-readable storage medium comprising program code to:

access a list of words;

load the forward trellis using the list of words to form a loaded forward trellis; and

load the reverse trellis using the list of words to form a loaded reverse trellis.

15. The non-transitory computer-readable storage medium of claim 14, wherein the list of words comprise a Devanagari list of words.

16. The non-transitory computer-readable storage medium of claim 14, further comprising forming a linking vector that indicates valid and invalid links into a node.

17. The non-transitory computer-readable storage medium of claim 14, further comprising, for each node in the forward trellis and the reverse trellis having a previous character position entering the node, forming a linking vector that indicates valid and invalid links into a node.

18. The non-transitory computer-readable storage medium of claim 14, further comprising, for each node in the forward trellis and the reverse trellis having a previous character position entering the node, forming a set of words indicating which words from the list of words have a path through the node.

19. The non-transitory computer-readable storage medium of claim 14, wherein loading the reverse trellis comprises, for each word in the list of words:

selecting a word from the list of words; and

loading the reverse trellis at;

a first character position with a final character;

a second character position with a second to the final character; and

a third character position with a third to the final character.

20. The non-transitory computer-readable storage medium of claim 14, further comprising sending the loaded forward trellis and the loaded reverse trellis to a mobile device.