Registers – Coded record sensors – Error checking
Patent
1991-01-17
1993-02-23
Shepperd, John W.
Registers
Coded record sensors
Error checking
235462, G06K 500, G06K 714, G06K 7016
Patent
active
051892898
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a bar code reading method and apparatus.
2. Background Art
Labels having bar codes are classified into, for example, two kinds, i.e., eight-digit labels and 13-digit labels. The eight-digit label is constructed by two blocks of left and right each having four digits. The 13-digit label is constructed by two blocks of left and right each having six digits. The left block has seven digits including two flag digits for indicating a figure.
In reading the 13-digit label, the six-digit block is sometimes read as a four-digit block depending on a way of beam scanning. As will be described in detail later, a prior art technique has a problem of erroneously reading the 13-digit label as the eight-digit label.
SUMMARY OF THE INVENTION
In view of the problems in the prior art, the present invention has an object to provide a bar code reading method and apparatus that can reduce a read error rate. More particularly, the present invention relates to a method and apparatus for distinguishing labels of, for example, the EAN-8 and EAN-13 type.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of an eight-digit label;
FIG. 2 is a diagram of a 13-digit label;
FIG. 3 is a chart showing data in a buffer memory;
FIG. 4 is a block diagram showing a principle of an aspect of the present invention;
FIG. 5 is a block diagram showing an embodiment of the present invention;
FIG. 6 is a diagram illustrating a configuration of data provided by a demodulator 16:
FIG. 7 is a diagram view showing a configuration of data stored in a buffer memory;
FIG. 8 is a diagram showing configurations of data stored in six-digit memory and four-digit memory;
FIGS. 9a and 9b form a flowchart explaining an operation of a central processing unit shown in FIG. 6;
FIG. 10 is a block diagram showing another embodiment of the present invention; and
FIGS. 11a and 11b form a flowchart explaining an operation of a central processing unit shown in FIG. 10.
DESCRIPTION OF THE PREFERRED EMBODIMENT
To understand the present invention more clearly, a conventional bar code reading system and its problems will be explained with reference to FIGS. 1 to 3.
Labels having bar codes are classified into two kinds, i.e., an eight-digit label 1 shown in FIG. 1 and a 13-digit label 2 shown in FIG. 2.
As shown in FIG. 1, the eight-digit label 1 has a left guard bar (LGB) 3, a center bar (CB) 4, and a right guard bar (RGB) 5, and is constructed by two blocks 6 and 7. Each of the blocks 6 and 7 comprises data of four digits where four is a standard value.
As shown in FIG. 2, the 13-digit label 2 has a left guard bar 3, a center bar 4, and a right guard bar 5, and is constructed by two blocks 8 and 9. Each of the two blocks 8 and 9 is constructed by data having a standard value of six digits.
The eight-digit label 1 and 13-digit label 2 are read as follows:
A bar code reader converts a bar code into a digital signal which is demodulated and stored in a buffer memory. Since the scanning speed of a light beam is high, the bar code printed on a bar code label is usually read by the bar code reader several times in a single reading operation in which the bar code is traced once from the right to the left or from the left to the right. The above-mentioned buffer memory 10, therefore, stores, in one reading operation, plural pairs of data, each pair of data consisting of the left and right blocks, as shown in FIG. 3. FIG. 3 shows that the 13-digit label 2 has been scanned "n" times in one reading operation, and that the buffer memory 10 is storing "n" pairs of data. In the figure, each circled numeral denotes the number of actually read digits. For example, in the first scan, four digits are read from the left block which originally has six digits, and six digits are correctly read from the right block. Each bar code data of the left or right block in the buffer memory 10 is provided with a flag indicating the number of digits (see FIG. 7). A CPU discriminates the number of digits of each dem
REFERENCES:
patent: 3932840 (1976-01-01), Hanchett
patent: 4329574 (1982-05-01), Jordan, Jr.
patent: 4717818 (1988-01-01), Broockman et al.
patent: 4746789 (1988-05-01), Gieles et al.
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IBM Technical Disclosure Bulletin, vol. 17, No. 7, Dec. 1974, "Code Validation in an Optical Bar-Code Reader", by R. A. Brecke et al., pp. 2080-2081.
IBM Technical Disclosure Bulletin, vol. 27, No. 7A, Dec. 1974, "Utilization of Data from Partial Reads of UPC Label", by E. C. Broockman, pp. 3720-3721.
Fujitsu Limited
Shepperd John W.
Sikorski Edward
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