Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2001-03-23
2001-10-09
Frech, Karl D. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462190
Reexamination Certificate
active
06299064
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method for correcting a bar width, a bar code reader, and a method for decoding a bar code.
2. Description of the Related Art
In recent years, as represented by POS systems in distributors, the management of goods or the like is generally performed by bar codes. For example, in a POS system of shops, information such as the type and a price of goods is coded into the format of a bar code, and the bar code is printed on the goods. Thereafter, checkout is performed by reading the bar code on a cash disk, and the number of sold goods are counted on real time. The number of sold goods is used in stock management and buying management.
In order to correctly read a read bar code, the bar width of each of bars constituting the bar code must be correctly recognized. For this reason, some methods for correcting the bar widths of the read bar code are proposed. As one of the problems in the bar width correction, a problem that the bars of the bar code are thickened or thinned by the degradation of print quality of the bar code is known.
A conventional bar width correcting method is effective when the bar widths of a bar code are uniformly thickened or thinned. However, when the bar widths of a bar code are locally thickened or thinned by bending or the like when the bar code is pasted on a curved surface, the bar widths are not effectively corrected, and the bar code may be erroneously read. An example in which bar width correction is not effectively performed will be described below.
As one of bar codes having low print quality, a bar code in which the width of a black bar of the bar code is thickened or thinned. A method in which the influence of uniform thickening or thinning of a black bar caused by printing a bar code is removed by using a delta distance to prevent the bar code from being erroneously read is known.
More specifically, as shown in
FIG. 11
, with reference to a bar code (see FIG.
11
(A)) having normal black bars, when a bar code (see
FIG. 11
(B)) having a thick black bar or a bar code (see
FIG. 11
(C)) having a thin black bar exists, a black bar portion and a white bar portion of the bar code are read as continuous values so as to detect delta distances T
1
and T
2
. More specifically, the widths of d bar and c bar of each bar code shown in
FIG. 11
are detected as the delta distances T
1
, and the widths of c bar and b bar are detected are detected as the delta distances T
2
. Thereafter, the number of modules in the delta distances T
1
and T
2
are detected.
As shown in
FIG. 12
, a first decoding table
61
in which character values are stored in correspondence with the number of modules of the delta distances T
1
and T
2
is prepared, and the character values corresponding to the delta distances T
1
and T
2
are detected from the first decoding table
61
, so that the character of the bar code is decided.
When the character is decided by the number of modules of the delta distances T
1
and T
2
, as is apparent from
FIG. 12
, an odd number “1” (01) and an odd number “7” (07) satisfy T
1
=3 and T
2
=4. For this reason, 01 cannot be discriminated from 07. Similarly, since an even number “2” (E2) and an even number “8” (E8) satisfy T
1
=3 and T
2
=3, E2 and E8 cannot be discriminated from each other.
For this reason, the values of characters are 01 and 07 or E2 and E8, the number of modules of black bars existing in the delta distance T
1
is calculated to discriminate the characters from each other. More specifically, the number of modules of the d bar shown in
FIG. 11
is calculated. A second decoding table
62
shown in
FIG. 13
is prepared, the character value corresponding to the number of modules of the d bar is detected from the second decoding table
62
. In this manner, a character is specified.
For example, when a delta distance satisfies T
1
=3 and T
2
=4, and the number of modules of d bar is 1, a character value is “01”. When the number of modules of the d bar is 2, a character value is “07”. Similarly, when a delta distance satisfies T
1
=3 and T
2
=3, and when the number of modules of d bar is 2, a character value is “E2”. When the number of modules of the d bar is 1, the character value is “E8”.
As described above, the width of a black bar is thickened or thinned depending on a print state. For this reason, when the number of modules of the black bar is directly calculated, the number of modules may be erroneously calculated. For this reason, in a conventional technique, bar width data of black bars (to be referred to as “X bars”) of a character (or any one of guard bars and center bars) immediately before decoding is completed is used on the assumption that the black bars of the bar code are uniformly thickened or thinned, so that the width of d bar is corrected (to be referred to as a “correction decoding process”: see Japanese Patent Application Laid-Open (JP-A) No. 6-36065).
More specifically, for example, when correction decoding of a character shown in
FIG. 14
is performed in a forward direction (direction from a start guard bar to an end guard bar), the widths (bar width count values) of black bars (b bar and d bar) of a character to be decoded are set to be b
1
and b
3
, respectively, and the bar width data (bar width count value) of an X bar is set to be bv. When the initial values of the bar widths are represented by Bv, B
1
, and B
3
, respectively, and when the differences between the ideal values and actual bar widths are represented by &Dgr;v, &Dgr;
1
, and &Dgr;
3
, respectively,
Bv=bv+&Dgr;v
Equation (1)
B
1
=
b
1
+&Dgr;
1
Equation (2)
B
3
=
b
3
+&Dgr;
3
Equation (3)
&Dgr;
x
≈&Dgr;
1
≈&Dgr;
3
Equation (4)
(assumption) are satisfied. Here, the difference between Bv and B
1
and the difference between Bv and B
3
are calculated, on the basis of Equation (1) and Equation (2),
Bv
-
B1
=
(
bv
+
Δ
v
)
-
(
b1
+
Δ
1
)
=
(
bv
+
b1
)
+
(
Δ
v
-
Δ
1
)
≈
bv
-
b1
Equation
(
5
)
is satisfied. Similarly, on the basis of Equation (1) and Equation (3),
Bv−B
3
≈
bv−b
3
Equation (6)
is satisfied. The Equation (5) and Equation (6) show that an error caused by printing or the like can be removed by calculating a difference between the bar widths of adjacent bars. In this case, when the number of modules of Equation (5) is calculated, the following is satisfied. However, the number of modules is represented as a symbol MOD (bar width count value).
MOD
(
Bv−B
1
)=
MOD
(
bv−b
1
) Equation (5)′
Here, since Bv and B
1
represent ideal bar widths, respectively, Bv and B
1
can be divided as follows:
MOD
(
Bv−B
1
)=
MOD
(
Bv
)−
MOD
(
B
1
).
Therefore, Equation (5)′ is also expressed by:
MOD
(
Bv
)−
MOD
(
B
1
)=
MOD
(
bv−b
1
)
∴
MOD
(
B
1
)=
MOD
(
Bv
)−
MOD
(
bv−b
1
) Equation (5)″.
Equation (5)″ represents that the ideal number of modules MOD (B
1
) of the d bar is calculated when MOD (bv−b
1
) is calculated and when MOD (bv−b
1
) is subtracted from the ideal number of modules MOD (Bv) of the bar X. Similarly, the following equation is satisfied:
MOD
(
B
3
)=
MOD
(
Bv
)−
MOD
(
b−bv
),
so that the ideal number of modules MOD (B
3
) of the b bar can be calculated. A character value corresponding to the ideal number of modules MOD (B
1
) of the d bar is read from the second decoding table
62
, and the character value is set as a character value of a character to be decoded.
However, the correction decoding described above is performed on the assumption that the black bars of a bar code are uniformly thickened or thinned. For this reason, when the black bars
Itoh Motohiko
Iwaguchi Isao
Kawai Hiroaki
Watanabe Mitsuo
Armstrong Westerman Hattori McLeland & Naughton LLP
Frech Karl D.
Fujitsu Limited
Taylor Larry D
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