Method and apparatus for multiplexed symbol decoding

• US 7,984,854 B2
• Filed: 07/17/2006
• Issued: 07/26/2011
• Est. Priority Date: 07/17/2006
• Status: Active Grant

• Current Assignee: Cognex Corporation
• Original Assignee: Cognex Corporation
• Inventors: Nadabar, Sateesha
• Primary Examiner(s): Kim; Ahshik
• Application Number:
  US11/457,968
• Publication Number:
  US 20080011855A1
• Time in Patent Office: 1,835 Days
• Field of Search: 235/462.07, 235/462.1, 235/462.11, 235/462.41
• US Class Current: 235/462.07
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/10851 Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device basic electronic circuitry H03
• 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

A method and apparatus for multi-threaded operation of an image-based symbology reader is provided. In the method of the invention, acquired images of an encoded symbol are attempted to be decoded using a plurality of decoding engines asynchronously and substantially simultaneously in a multi-threaded processing environment. Each of the decoding engines can be directed to a specific symbology type to achieve an improved response time when reading multiple symbol types.

Claims

1. A symbology reader comprising:

an imaging module having an image sensor and a lens to cooperatively provide an image of a field of view;

a data bus coupled to the imaging module;

a memory module coupled to the data bus; and

a processor coupled to the data bus, the processor comprising;

an acquisition process that controls the imaging module and the memory module to transfer the image into the memory module via the data bus;

a first decoding thread process that attempts to decode a first symbol type of the image of the field of view;

a second decoding thread process that attempts to decode a second symbol type of the image of the field of view; and

wherein the first decoding thread process and the second decoding thread process execute substantially simultaneously.

2. The symbology reader of claim 1 wherein the imaging module, data bus, memory module, and processor are contained within a housing adapted for use as a hand-held reader.

3. The symbology reader of claim 2 further comprising a trigger cooperative with the processor and adapted to initiate the acquisition process, first decoding thread process, and second decoding thread process when the trigger is actuated by a user.

4. The symbology reader of claim 1 wherein the imaging module, data bus, memory module, and processor are contained within a housing adapted for use as a fixed-mount reader.

5. The symbology reader of claim 1 wherein the processor further comprises at least one additional decoding thread process that attempts to decode at least one additional symbol type of the image of the field of view, and wherein each of the first decoding thread process, second decoding thread process, and the at least one additional decoding thread process execute substantially simultaneously.

6. The symbology reader of claim 1 further comprising a communications module adapted to transfer a result of any of the first and second decoding thread process to a host computer.

7. The symbology reader of claim 6 wherein the communications module uses a protocol selected from a list consisting of USB, RS-232, and 802.11 wireless.

8. The symbol reader of claim 1 wherein any of the first decoding thread process and second decoding thread process that is rendered unsuccessful when the elapsed time exceeds an associated timeout variable repeats the decode attempt asynchronously and substantially simultaneously to the respective other of the first decoding thread process and the second decoding thread process using another of the acquired images of the field of view.

9. The symbol reader of claim 8 wherein each time a decoding thread process is used to attempt to decode an image, the image used is a most recently acquired image.

10. The symbol reader of claim 9 wherein the elapsed time is reset for a decoding thread when an attempt to decode a most recently acquired image commences.

11. The symbol reader of claim 1 wherein each time a decoding thread process commences the decoding thread process attempts to decode the encoded symbol in the most recently acquired image of the field of view.

12. The symbol reader of claim 1 wherein first and second apportioning variables are assigned to first and second decoding threads, respectively, where the apportioning variables distribute processing resources unevenly between the first and second decoding threads.

13. The reader of claim 1 wherein the first and second decoding thread processes are executed during small time slices in an interleaved fashion.

14. A method for reading an encoded symbol comprising:

acquiring image of a field of view;

attempting to decode an encoded symbol from the acquired image using a first decoding thread while asynchronously and substantially simultaneously attempting to decode the encoded symbol from the image using a second decoding thread; and

reporting a result when one of the first decoding thread and the second decoding thread is successful.

15. The method of claim 14 wherein the step of acquiring an image further comprises continuously acquiring a plurality of images and wherein at least one of the images includes the encoded symbol.

16. The method of claim 15 wherein each of the first decoding thread and the second decoding thread has a timeout variable that renders the respective decoding thread unsuccessful if an elapsed time exceeds the timeout variable.

17. The method of claim 16 wherein any of the first decoding thread and second decoding thread that is rendered unsuccessful by the timeout variable repeats the acquiring step and the decode attempt step asynchronously and substantially simultaneously to the respective other of the first decoding thread and the second decoding thread.

18. The method of claim 16 wherein the at least one acquired image is a first image, first and second different timeout variables are associated with the first and second decoding threads, respectively, the method further including the step of, when one of the first and second decoding threads is unsuccessful prior to the timeout variable associated with the other of the first and second decoding threads elapsing, attempting to decode an encoded symbol in a second image of the field of view that is different than the first image using the unsuccessful decoding thread.

19. The method of claim 18 wherein the second image is the most recently obtained image of the field of view.

20. The method of claim 14 wherein the first decoding thread is intended for a one-dimensional bar code symbol, and the second decoding thread is intended for a two-dimensional symbol.

21. The method of claim 14 wherein the first decoding thread is intended for a two-dimensional code of a first type, and the second decoding thread is intended for a two-dimensional code of a second type.

22. The method of claim 14 wherein the first decoding thread and the second decoding thread are intended for a similar symbol type.

23. The method of claim 14 wherein the first and second decoding thread processes are executed during small time slices in an interleaved fashion.

24. A method for reading an encoded symbol comprising:

assigning first and second timeout variables to first and second decoding threads, respectively, where the first and second timeout variables are different and the first and second decoding threads are unsuccessful if an elapsed time exceeds the first and second timeout variables, respectively;

acquiring at least one image of the encoded symbol;

attempting to decode the encoded symbol from the at least one image using the first decoding thread while substantially simultaneously and asynchronously attempting to decode the encoded symbol from the at least one image using the second decoding thread; and

reporting a result when one of the first decoding thread and the second decoding thread is successful.

25. The method of claim 24 wherein the step of attempting to decode the encoded symbol is repeated by any one of the first and second decoding threads asynchronously and substantially simultaneously with the other respective one of the decoding threads using another of the plurality of images.

26. The method of claim 25 wherein two of the plurality of decoding threads are intended for a similar symbol type.

27. The method of claim 24 wherein the first decoding thread is intended for a two-dimensional code of a first type, and the second decoding threads is intended for a two-dimensional code of a second type.

28. The method of claim 24 wherein the at least one image is a first image, the first time out period is shorter than the second time out period and, when the elapsed time exceeds the first time out period, the step of attempting to decode the encoded symbol using the first decoding thread is repeated asynchronously and substantially simultaneously with the second decoding threads using a second images that is different than the first image.

29. The method of claim 28 wherein the first decoding thread is intended for a two-dimensional code of a first type, and second decoding thread is intended for a two-dimensional code of a second type.

30. A method for reading an encoded symbol comprising:

assigning first and second apportioning variables to first and second decoding threads, respectively, where the apportioning variables distribute processing resources unevenly between the first and second decoding threads;

assigning first and second different timeout variables to first and second decoding threads, respectively, wherein the first decoding thread is unsuccessful when an elapsed time exceeds the first timeout variable and the second decoding thread is unsuccessful when an elapsed time exceeds the second timeout variable;

continuously acquiring images of a field of view;

attempting to decode an encoded symbol from at least one of the acquired images using the first decoding thread while asynchronously and substantially simultaneously attempting to decode the encoded symbol from at least one of the acquired images using a second decoding thread;

when the attempt to decode using the first decoding thread is unsuccessful while the attempt to decode the encoded symbol using the second decoding thread continues, repeating the attempting to decode step using the first decoding thread for another of the acquired images during another period corresponding to the first timeout variable; and

when the attempt to decode using the second decoding thread is unsuccessful while the attempt to decode the encoded symbol using the first decoding thread continues, repeating the attempting to decode step using the second decoding thread for another of the acquired images during another period corresponding to the second timeout variable.

31. The method of claim 30 wherein, each time an attempting step is repeated, the step is repeated using a most recently acquired image of the field of view.

32. A symbology reader comprising:

an imaging module having an image sensor and a lens to cooperatively provide

a series of images of a field of view;

a data bus coupled to the imaging module;

a memory module coupled to the data bus; and

a processor coupled to the data bus, the processor comprising;

an acquisition process that controls the imaging module and the memory module to transfer the series of images into the memory module via the data bus;

a first decoding thread process that attempts to decode a first symbol type of at least one of the images of the field of view;

a second decoding thread process that attempts to decode a second symbol type of at least one of the images of the field of view; and

wherein first and second timeout variables are assigned to the first and second decoding threads, respectively, where, the first and second timeout variables are different and the first and second decoding threads are unsuccessful if an elapsed time exceeds the first and second timeout variables, respectively;

wherein the first decoding thread process and the second decoding thread process execute substantially simultaneously.

33. A method for reading an encoded symbol comprising:

assigning first and second apportioning variables to first and second decoding threads, respectively, where the apportioning variables distribute processing resources unevenly between the first and second decoding threads;

acquiring at least one image of a field of view;

attempting to decode an encoded symbol from the at least one image using the first decoding thread while asynchronously and substantially simultaneously attempting to decode the encoded symbol from the at least one image using a second decoding thread; and

reporting a result when one of the first decoding thread and the second decoding thread is successful.

34. A symbology reader comprising:

an imaging module having an image sensor for generating images of a field of view;

a data bus coupled to the imaging module;

a memory module coupled to the data bus; and

at least one processor coupled to the data bus, the at least one processor running at least one program to perform the following processes;

an acquisition process that controls the imaging module and the memory module to transfer the images into the memory module via the data bus;

a first decoding thread process that attempts to decode a first symbol type in at least one of the generated images;

a second decoding thread process that attempts to decode a second symbol type in at least one of the generated images; and

wherein the first decoding thread process and the second decoding thread process execute substantially simultaneously.

35. The symbology reader of claim 34 wherein the processor further comprises at least one additional decoding thread process that attempts to decode at least one additional symbol type of the image of the field of view, and wherein each of the first decoding thread process, second decoding thread process, and the at least one additional decoding thread process execute substantially simultaneously.

36. A method for reading an encoded symbol comprising:

using a single imaging module to acquire images of a field of view;

attempting to decode an encoded symbol in at least one of the acquired images using a first decoding thread while asynchronously and substantially simultaneously attempting to decode an encoded symbol in at least one of the images using a second decoding thread; and

reporting a result when one of the first decoding thread and the second decoding thread is successful.

37. The method of claim 36 wherein the first decoding thread is intended for a one-dimensional bar code symbol, and the second decoding thread is intended for a two-dimensional symbol.