Synthesis decoding and methods of use thereof

• US 7,416,125 B2
• Filed: 03/24/2005
• Issued: 08/26/2008
• Est. Priority Date: 03/24/2005
• Status: Active Grant

• Current Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Original Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Inventors: Longacre, Andrew Jr., Wang, Ynjiun P.
• Primary Examiner(s): Hess; Daniel A
• Application Number:
  US11/088,612
• Publication Number:
  US 20060213999A1
• Time in Patent Office: 1,251 Days
• Field of Search: 23546201-46249, 235/454
• US Class Current: 235/462.25
• CPC Class Codes: G06K 7/1093 sensing, after transfer of the image of the data-field to an intermediate store, e.g. storage with cathode ray tube

Abstract

Systems and methods for successfully decoding optical images of objects of interest when such objects are situated outside a conventional working range of an imaging system, or when such objects are degraded. The systems and methods are based upon a comparison of computed signals corresponding to distorted images that would be obtained from known objects, such as barcodes, when viewed outside a working range, or when degraded, with actual signals obtained from the object of interest. The computed signals in one embodiment are recorded in a lookup table. An advantage of the systems and methods disclosed is that there results a smooth, monotonic probability of correctly decoding the image of interest, even beyond the working distance. A handheld or portable apparatus useful for practicing the invention is also disclosed.

Claims

1. A bar code reading apparatus for decoding a degraded encoded symbol character of a symbology, comprising:

a detector that detects light intensity corresponding to illumination reflected from the degraded encoded symbol character and that generates an electrical signal from the detected light intensity, the degraded encoded symbol character failing to conform with a standard definition of a character of said symbology;

a signal processor that recovers from the generated electrical signal a value representative of a valid encoded symbol character of the symbology; and

a Synthesis Decode Table having values representative of valid encoded symbol characters correlated to bar space patterns having a number of bar space elements that deviate from a standard defined number of bar space elements for said symbology.

2. The bar code reading apparatus for decoding a degraded encoded symbol character of claim 1, wherein the signal processor comprises a microprocessor, a memory, and instructions recorded on a machine-readable medium for controlling operation of the microprocessor.

3. The bar code reading apparatus for decoding a degraded encoded symbol character of claim 1, wherein the valid encoded symbol character corresponds to a value represented by the degraded encoded symbol character at a time prior to it being degraded.

4. The bar code reading apparatus for decoding a degraded encoded symbol character of claim 1, wherein the detector comprises an imager device having a plurality of pixel elements.

5. The bar code reading apparatus for decoding a degraded encoded symbol character of claim 1, wherein the detector comprises a laser scanner apparatus.

6. The bar code reading apparatus for decoding a degraded encoded symbol character of claim 1, wherein the bar code reading apparatus is of a format compact enough to be operated while being supported by a hand of a user.

7. The bar code reading apparatus for decoding a degraded encoded symbol character of claim 1, wherein the symbology is a Universal Product Code (“

UPC”

) symbology.

8. The bar code reading apparatus for decoding a degraded encoded symbol character of claim 1, wherein the signal processor compares the generated electrical signal to a pre-defined signal.

9. The bar code reading apparatus for decoding a degraded encoded symbol character of claim 1, further comprising an analog-to-digital converter for digitizing the generated electrical signal.

10. A bar code reading apparatus for processing a degraded encoded symbol character of a symbol in accordance with a symbology lacking error correction at a symbol character level and wherein according to a standard definition of the symbology M element bar space patterns are correlated to valid symbol characters, and wherein said degraded encoded symbol character is degraded such that said degraded encoded symbol character has M-N bar space elements, said apparatus comprising:

detector that detects light intensity corresponding to illumination reflected from said degraded encoded symbol character and that generates an electrical signal from said detected light intensity;

pre-stored information correlating M-N element bar space patterns with valid symbol characters of said symbology having a symbology standard definition wherein M element bar space patterns are correlated to said valid symbol characters; and

a signal processor utilizing said pre-stored information to recover from said generated electrical signal a value representative of a valid encoded symbol character of said symbology.

11. The bar code reading apparatus of claim 10, wherein said pre-stored information includes calculated values calculated to be produced by said detector when a valid encoded symbol character is disposed a distance selected from one of distance shorter than a minimum working distance of said bar code reading apparatus or a distance longer than a maximum working distance of said bar code reading apparatus.

12. The bar code reading apparatus of claim 10, wherein said pre-stored information is determined by reading known indicia at known distances and recoding produced signals.

13. The bar code reading apparatus of claim 10, wherein said pre-stored information is determined by synthesizing expected decoded waveform utilizing a point spread function of said bar code reading apparatus.

14. The bar code reading apparatus of claim 10, wherein said signal processor in recovering said value from said electrical signal determines an edge shift distance for said electrical signal.

15. The bar code reading apparatus of claim 10, wherein said signal processor in recovering said value from said electrical signal does not attempt to recover missing bar space elements from said electrical signal.

16. The bar code reading apparatus of claim 10, wherein said bar code reading apparatus is hand held.

17. The bar code reading apparatus of claim 10, wherein said detector is a multiple pixel image sensor.

18. The bar code reading apparatus of claim 10, wherein said certain symbology is UPC symbology.

19. The bar code reading apparatus of claim 10, wherein said degraded encoded symbol character has a 3 unit wide black bar in place of a bar-space-bar pattern converting said bar-space-bar pattern into a 3 unit wide bar.

20. A bar code reading apparatus for processing a degraded encoded symbol character of a symbol in accordance with a symbology and wherein according to a standard definition of said symbology M element bar space patterns are correlated to valid symbol characters, and wherein said degraded encoded symbol character is degraded such that said degraded encoded symbol character has K bar space elements, and wherein K is not equal to M, said apparatus comprising:

a detector that detects light intensity corresponding to illumination reflected from said degraded encoded symbol character and that generates an electrical signal from said detected light intensity;

pre-stored information correlating a K element bar space pattern with a valid symbol character of said symbology having a symbology standard definition wherein M element bar space patterns are correlated to said valid symbol characters; and

wherein said barcode reading apparatus utilizes said pre-stored information to recover from said generated electrical signal a value representative of a valid encoded symbol character of said symbology.

21. The bar code reading apparatus of claim 20, wherein said pre-stored information includes calculated values calculated to be produced by said detector when a valid encoded symbol character is disposed a distance selected from one of distance shorter than a minimum working distance of said bar code reading apparatus or a distance longer than a maximum working distance of said bar code reading apparatus.

22. The bar code reading apparatus of claim 20, wherein said pre-stored information is determined by reading known indicia at known distances and recoding produced signals.

23. The bar code reading apparatus of claim 20, wherein said pre-stored information is determined by synthesizing expected decoded waveform utilizing a point spread function of said bar code reading apparatus.

24. The bar code reading apparatus of claim 20, wherein said bar code reading apparatus in recovering said value from said electrical signal determines an edge shift distance for said electrical signal.

25. The bar code reading apparatus of claim 20, wherein said bar code reading apparatus in recovering said value from said electrical signal does not attempt to recover missing bar space elements from said electrical signal.

26. The bar code reading apparatus of claim 20, wherein said bar code reading apparatus is hand held.

27. The bar code reading apparatus of claim 20, wherein said detector is a multiple pixel image sensor.

28. The bar code reading apparatus of claim 20, wherein said certain symbology is UPC symbology.

29. The bar code reading apparatus of claim 20, wherein said degraded encoded symbol character has a 3 unit wide black bar in place of a bar-space-bar pattern converting said bar-space-bar pattern into a 3 unit wide bar.