Method and apparatus for capturing a decodable representation of a 2D bar code symbol using a hand-held reader having a 1D image sensor

• US 5,773,806 A
• Filed: 07/20/1995
• Issued: 06/30/1998
• Est. Priority Date: 07/20/1995
• Status: Expired due to Term

• Current Assignee: Welch Allyn Data Collection Inc (Welch Allyn Incorporated)
• Original Assignee: Welch Allyn Incorporated
• Inventors: Longacre, Andrew Jr.
• Primary Examiner(s): Hajec, Donald T.
• Assistant Examiner(s): Le, Thien Minh
• Application Number:
  US08/504,643
• Time in Patent Office: 1,076 Days
• Field of Search: 235/462, 235/472, 235/454, 235/463, 235/470
• US Class Current: 235/462.1
• CPC Class Codes: G06K 17/0022 arrangements or provisions for transferring data to distant stations, e.g. from a sensing device "transfer between computer elements G06F13/00 "; data-transmission H04L
• CPC Class Codes: G06K 19/06037 multi-dimensional coding
• 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 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence
• CPC Class Codes: G06K 7/1491 the method including a reconstruction step, e.g. stitching two pieces of bar code together to derive the full bar code

Abstract

A method and apparatus for capturing and storing a decodable representation of a 1D or 2D bar code symbol using a hand-held bar code reader having only a 1D image sensor. A succession of 1D digital representations are produced as the reader is moved asynchronously across the symbol to be read. These representations are examined, substantially in real time, and, if the symbol is a 1D symbol, is decoded immediately. If the symbol is not a 1D symbol, these representations are examined for the presence of one of a variety of different types of 2D finder patterns and, when the finder has been identified, decoded with reference to that finder pattern.

Claims

1. A method for asynchronously acquiring and storing a decodable representation of 1D or 2D bar code symbol using a hand-held bar code reader of the type which is adapted to image a 1D slice of said symbol, and to produce a digital representation of said slice, including the steps of:

providing in said reader a memory space for storing the digital representations of a plurality of said slices;

moving said reader across said symbol while imaging a succession of 1D slices thereof;

producing from said succession of imaged slices a succession of digital representations thereof, including a timercount representation and a bit image representation of said each imaged slice;

storing said digital representations in said memory space substantially in real time;

continuing said storing step until the number of stored representations is sufficient to allow the data encoded in said symbol to be determined with reference to said stored representations.

2. The method of claim 1 including the further steps of:

examining successive digital representations, substantially as they occur, and;

(i) for 1D symbols, attempting to decode such symbols with reference to one or more timercount representations thereof;

(ii) for 2D symbols, examining successive ones of the bit image representations of said symbol to locate and identify a finder pattern for said symbol and, if a finder pattern is located and identified, attempting to decode such symbols with reference to the bit image representations stored in said memory space.

3. The method of claim 1 in which said bar code symbol may be a 1D stacked bar code symbol that includes plurality rows of decodable elements, including the further step of determining whether said symbol is a 1D stacked symbol and, if said symbol is a 1D stacked symbol, repeating the decoding step until enough of the rows of the 1D stacked symbol have been decoded to assemble a complete message.

4. The method of claim 2 in which the step of examining successive ones of the bit image representations for a finder pattern includes the steps of;

(i) storing a plurality of finder identifying algorithms, each finder identifying algorithm being of a type suitable for identifying a respective type of finder pattern;

(ii) executing said finder identifying algorithms one after another to determine which of said finder patterns is used in said symbol; and

(iii) discontinuing the storing of additional bit image representations when the number of bit image representations stored in said memory space is sufficient to permit the data stored in said memory space to be decoded with reference to the finder pattern used by said symbol.

5. The method of claim 4 in which one of said finder identifying algorithms is an algorithm which includes the steps of:

deriving, from successive bit image representations, sets of numbers which are indicative of the degrees of isolation of the bits of said bit image representations, and

comparing successive ones of said sets of numbers to identify the bit image representation having bits with the highest degree of isolation.

6. The method of claim 4 in which said finder identifying algorithms include a first algorithm for identifying finder patterns of the central type, a second algorithm for identifying finder patterns of the waistband type, and a third algorithm for identifying finder patterns of the peripheral type.

7. The method of claim 1 in which the step of storing successive bit image representations is performed on a first in-first out basis, whereby predetermined sets of successive bit image representations may be examined and compared, substantially in real time, for symbol structures which cannot be identified with reference to a single bit image representation.

8. The method of claim 4 including the step, after said discontinuing step, of reorganizing said bit image representations in order to facilitate the decoding thereof.

9. The method of claim 4 including the step, after said discontinuing step, of reorganizing said bit image representations to form an image of the bar code symbol in which the bits of the bit image representations are located approximately in their true relative positions with respect to said finder pattern.

10. A method for asynchronously acquiring and storing a decodable representation of a 1D or 2D bar code symbol using a hand-held bar code reader of the type which includes a 1D image sensor and which is adapted to image a 1D slice of said symbol and to produce at least two types of digital representation of said slice, including the steps of:

moving said reader across said symbol while imaging a succession of 1D slices thereof;

producing from said slices a succession of digital representations thereof, said digital representations including both timercount and bit image representations of said slices;

examining said digital representations substantially as they occur to determine if the symbol can be decoded as a 1D symbol and,

if it can be decoded as a 1D symbol, decoding said symbol as a 1D symbol with reference to at least said timercount representations thereof, and,

if it cannot be decoded as a 1D symbol, examining sets of said digital representations to locate and identify a 2D finder pattern for said symbol and, when said finder pattern has been located and identified, decoding said symbol as a 2D symbol with reference to the finder pattern and at least said bit image representations thereof.

11. The method of claim 10 in which said bar code symbol may be a 1D stacked bar code symbol that includes a plurality of rows of decodable elements, including the further step of determining whether said symbol is a 1D stacked symbol and, if said symbol is a 1D stacked symbol, repeating the decoding step until enough of the rows of the 1D stacked symbol have been decoded to assemble a complete message.

12. The method of claim 10 in which the step of examining sets of the digital representations for a finder pattern includes the steps of;

(i) storing a plurality of finder identifying algorithms, each finder identifying algorithm being of a type suitable for identifying a respective type of finder pattern;

(ii) executing said finder identifying algorithms one after another to determine which of said finder patterns is used in said symbol; and

(iii) continuing to produce digital representations until the number of digital representations is sufficient to permit the symbol to be decoded.

13. The method of claim 12 in which one of said finder identifying algorithms is an algorithm which includes the steps of:

deriving, from successive bit image representations, sets of numbers which are indicative of the degrees of isolation of the bits of said bit image representations, and

comparing successive ones of said sets of numbers to identify the bit image representations having bits with the highest degree of isolation.

14. In a hand-held bar code reader for asynchronously acquiring and storing a decodable representation of a 1D or 2D bar code symbol, said reader being of the type having a 1D image sensor for receiving an image of a slice of said symbol and generating an output signal that varies in accordance with the data content of said slice, and processing circuitry for converting said output signal into a digital representation of said slice, in combination:

programmed control means responsive to said image sensor and said processing circuitry for producing digital representations of successive slices of said symbol as said reader is moved asynchronously across said symbol, said digital representations including both timercount and bit image representation of said successive slices;

a memory space for storing the digital representations of said succession of slices substantially in real time;

wherein said programmed control means is programmed to discontinue the storing of said digital representations when the number of said representations is sufficient to allow the data encoded in said symbol to be determined with reference to said memory space.

15. The bar code reader of claim 14 in which said programmed control means includes a central processor for controlling the generation of said digital representations in accordance with a stored program, and DMA circuitry for controlling the storing of said representations in said memory space.

16. The bar code reader of claim 14 in which said stored program is a stored program which examines said digital representations substantially in real time to determine whether the symbol being imaged can be decoded as a 1D symbol and, if it can be decoded as a 1D symbol, decoding said symbol without searching for a finder pattern and, if it cannot be decoded as a 1D symbol, examining said digital representations to identify which of a plurality of possible finder patterns is used therein and, when said finder has been identified, decoding the symbol with reference to said finder pattern.

17. The bar code reader of claim 16 in which said program is arranged to determine whether the 1D symbol is a stacked linear symbol or a symbol and, if it is a stacked symbol, to decode each tier of the stacked symbol until enough data to construct a complete message is obtained.

18. The bar code reader of claim 16 in which said program includes a plurality of finder identifying component programs each adapted to identify a respective one of said possible finder patterns, and a program for sequentially applying said component programs to said digital representations and determining the component program which most nearly corresponds to the finder pattern used by said symbol.

19. The bar code reader of claim 16 in which said finder identifying component programs include a first component program for identifying finder patterns of the central type, a second component program for identifying finder patterns of the waistband type, and a third component program for identifying finder patterns of the peripheral type.

20. The bar code reader of claim 18 in which one of said finder identifying component programs comprises a program which:

derives, from successive digital representations, sets of numbers which are indicative of the degrees of isolation of the digital constituents thereof, and

compares successive ones of said sets of numbers to determine which of said representations has the constituent with the highest degree of isolation.

21. The bar code reader of claim 16 in which said successive digital representations are stored on a first in-first out basis, whereby subsets of successive digital representations may be examined and compared to identify symbol structures which cannot be represented in a single digital representation.

22. The bar code reader of claim 18 in which said program discontinues the storage of digital representations after enough such representations have been produced to enable said symbol to be decoded.

23. A method for asynchronously acquiring and storing a decodable representation of 1D or 2D bar code symbol using a hand-held bar code reader of the type which is adapted to image a 1D slice of said symbol, and to produce a digital representation of said slice, including the steps of:

providing in said reader a memory space for storing the digital representations of a plurality of said slices;

moving said reader across said symbol while imaging a succession of 1D slices thereof;

producing from said succession of imaged slices a succession of digital representations thereof;

storing said digital representations in said memory space substantially in real time, wherein said storing step of storing successive bit image representations is performed on a first in-first out basis so that predetermined sets of successive bit image representations may be examined and compared, substantially in real time, for symbol structures which cannot be identified with reference to a single bit image representation; and

continuing said storing step until the number of stored representations is sufficient to allow the data encoded in said symbol to be determined with reference to said stored representations.