Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2002-02-21
2003-04-15
Lee, Michael G. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S437000
Reexamination Certificate
active
06547143
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a bar-code reader and a bar-code reading method for optically reading bar codes by scanning bar codes that express characters based on bar width, with laser beams.
BACKGROUND ART
Recently, POS (point of sales) systems have been diffused rapidly in retail shops, particularly, in convenience stores, department stores, supermarkets, etc, in order to quickly understand the contents of sales of products and to save manpower. In the POS system, there is built in a bar-code reader for optically reading bar codes that express characters, and decoding these characters based on the read result of the bar codes.
There may arise variances in the bar widths of the bar codes that are attached to goods, depending on print precision levels. Therefore, the bar-code reader is required to decode characters in high precision without being affected by the variances in the bar widths.
FIG. 8
is a block diagram showing a structure of a conventional bar-code reader. In this drawing, a bar code
10
is attached to goods not shown. The bar code consists of a plurality of black bars and white bars that are combined together in alternate order, to express twenty kinds of characters in total including E (EVEN) 0 to E9 and O (ODD) 0 to O9. As this bar code
10
, there are EAN (European Article Number) that is used invarious countries in the world, and UPC (Universal Product Code) that is used in America.
FIG. 9
is a top plan view which shows the bar code
10
. The bar code
10
shown in this drawing has black bars BB
1
, white bars WB
1
, black bars BB
2
, and white bars WB
2
that are laid out alternately, as an example. Further, this bar code
10
is constructed of a left margin LM, a left guard bar LGB that includes a black bar LGB
1
and a white bar LGB
2
, a left data character
10
L that consists of six characters (for example, “000000”), a center bar CB, a right data character
10
R that consists of five characters (for example, “128963”), a check digit code CD that consists of one character (for example, “2”), a right guard bar RGB that includes a white bar RGB
1
and a black bar RGB
2
, and a right margin RM, in the order from the left to the right in the drawing.
In this drawing, a country code C
1
is “20”, a goods maker code C
2
is “00000”, a goods item code C
3
is “28963”, and a check digit code CD is “2”. This check digit code CD is a code that is used for a calculation check (for example, a modulus ten check) for increasing the reliability (precision) of the bar-code data.
One character in the bar code
10
is constructed of four bars (elements) including a first black bar, a second white bar, a third black bar, and a fourth white bar, in the order from the right to the left, as shown in FIG.
10
(
a
) to FIG.
10
(
d
). A character length C (a distance from the edge of the first black bar to the edge of the fourth white bar) is set to have seven modules (a unit length is called a “module”).
Further, the bar code
10
expresses ten kinds of numbers (characters) from “0” to “9”, based on the combination of a black-bar width B
1
of the first black bar, a white-bar width B
2
of the second white bar, a black-bar width B
3
of the third black bar, and a white-bar width B
4
of the fourth white bar. Further, the bar code
10
can express twenty kinds of characters with the same number, by introducing a combination of two kinds of an odd number and an even number for the number of modules of the black bars, as shown in FIG.
11
.
A number of modules of black bars that becomes an odd number will be called ODD (hereinafter to be abbreviated as O), and, on the other hand, a number of modules of black bars that becomes an even number will be called EVEN (hereinafter to be abbreviated as E).
FIG. 11
shows an example of twenty kinds of characters in total that includes ten kinds of characters from a character O0 to a character O9 for which the number of modules of black bars becomes an odd number respectively, and ten kinds of characters from a character E0 to a character E9 for which the number of modules of black bars becomes an even number respectively.
The character O0 and the character E0 shown in the drawing will be explained as an example. The character O0 is constructed of a first black bar (the number of modules is one), a second white bar (the number of modules is one), a third black bar (the number of modules is two), and a fourth white bar (the number of modules is three), in the order from the right to the left in the drawing. Further, the character O0 has three modules as the sum of the number of modules of the first black bar (=1) and the number of modules of the third black bar (=2), that is, an odd number.
On the other hand, the character E0 is constructed of a first black bar (the number of modules is three), a second white bar (the number of modules is two), a third black bar (the number of modules is one), and a fourth white bar (the number of modules is one), in the order from the right to the left in the drawing. Further, the character E0 has four modules as the sum of the number of modules of the first black bar (=3) and the number of modules of the third black bar (=1), that is, an even number.
A character E4 shown in FIG.
10
(
a
) is constructed of a black bar having one module for the black-bar width B
1
, a white bar having one module for the white-bar width B
2
that is adjacent to this black bar, a black bar having three modules for the black-bar width B
3
that is adjacent to this white bar, and a white bar having two modules for the white-bar width B
4
that is adjacent to this black bar, in the order from the right to the left in this drawing.
The sum of the black-bar width B
1
and the white-bar width B
2
, that is a distance from the edge of the first black bar to the edge the second white bar, is called a delta distance T
1
. In the example shown in this drawing, this delta distance T
1
is two modules. Further, the sum of the white-bar width B
2
and the black-bar width B
3
, that is a distance from the edge of the second white bar to the edge the third black bar, is called a delta distance T
2
. In the example shown in this drawing, this delta distance T
2
is four modules.
The delta distance T
1
, the delta distance T
2
, the black-bar width B
1
, and the black bar B
3
are important parameters that are used to decide which one of the character O0 to the character O9 and the character E0 to the character E9 shown in
FIG. 11
the character belongs to.
In other words, in
FIG. 11
, the delta distance T
1
and the delta distance T
2
for each one of the character O0 to the character O9 and the character E0 to the character E9 are different from those delta distance of the other characters. Therefore, it is possible to decide a character from the delta distance T
1
and the delta distance T
2
. For making this decision, a first demodulation table
100
of
FIG. 13
is used that shows a relationship between each pattern of combination of the delta distance T
1
and the delta distance T
2
, and each character.
However, as shown in
FIG. 13
, the character E2 and the character E8, the character O2 and the character O8, the character O1 and the character O7, and the character E1 and the character E7 respectively have the same combination values for the delta distance T
1
and the delta distance T
2
. Therefore, it is not possible to decide these characters based on the delta distance T
1
and the delta distance T
2
.
Specifically, taking an example of the character E2 and the character E8, both characters have the same values for the delta distance T
1
as three modules and the delta distance T
2
as three modules. Therefore, based on only the delta distance T
1
and the delta distance T
2
, it is not possible to decide whether the character is the character E2 or the character E8.
Accordingly, between the character E2 and the character E8, between the character O2 and the character O8, between the character O1 and the character O7, and between the character E1 and the character E7 respec
Ishi Mitsuharu
Koyanagi Norio
Armstrong Westerman & Hattori, LLP
Fureman Jared J.
LandOfFree
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