JP3131866B2 - Bar code reading method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bar code reading method and a bar code reading apparatus, and more particularly, to a bar code using a binary code and a multi-code, and a start code or a start code in a symbol. The present invention relates to a technique for preventing erroneous reading in barcode reading that is effective when a comparable first character exists and an adjacent narrow bar (narrow bar) and a narrow space (narrow space) exist therein.

[0002]

2. Description of the Related Art Conventionally, there are the following techniques for width determination in bar code reading. The first method is a method of judging a wide width and a narrow width while updating a reference value for width determination for each bar and each space for each bar. Hereinafter, this method will be described using the barcode shown in FIG. 6 as an example. FIG. 6 shows the NW-7 standard (CODA
BAR) Start character a in barcode
And an example of the character 1 following it. Actually, a code representing each character is described after the illustrated portion to reach the stop character, but here, this is omitted for convenience. In the NW-7 standard, four start characters "a", "b", "c", and "d" are used as start characters.
Although two characters are defined, in the example of FIG.
a ″ is used. Reference numeral 101 denotes the direction of the scanning line.

First, a code described at the beginning of a symbol, here, a character a is searched. NW-7
According to the standard, the arrangement of the bar and the space of the character a is “0011010” (0 indicates a narrow bar or space, and 1 indicates a wide bar or space). The determination of the character a is performed, for example, in the following procedure.

[0004]

## EQU1 ## (1) B1 <B2... Reference is narrow width of B1 and is B2 wide? (2) B2 <B3 ... Is the standard B2 thick and B3 narrow? (3) b3 = b4: The standard is the narrow width of B3, and is B4 narrow? (4) S1 <S2: Is the standard the narrow width of S1, and is S2 the wide width? (5) S2 = S3: The standard is the wide width of S2, and is S3 the wide width?

[0005] As the width determination is performed as described above, the reference data is "B1 narrow width" in the case of a bar.
It is updated in the order of “B2 wide width” → “B3 narrow width” → “B4 narrow width”. In the determination of the width, the next determination is always performed using the width determined immediately before as a reference value. Similarly, in the case of a space, “S1 narrow width” → “S2
Are updated in the order of “thick width” → “narrow width of S3” → “narrow width of S4”. That is, the width is determined by comparing the bars with each other and the space by comparing the spaces with each other, and the subsequent width determination is similarly performed.

[0006] In the NW-7 standard, the width ratio of the bar code is defined to be in the range of 1: 2.0 to 1: 3.0, and is usually set to 1:
Any of the ratios 2.0, 1: 2.5, 1: 3.0 is used. Here, a specific width determination is performed based on the following criteria.

[0007]

[Equation 2] (a) Judgment of the same width: Comparison value is -α1 to + α2 of the reference value
Is it within [%]? (b) Thin-thick judgment: The comparison value is the narrow reference value x -α3 to + α4
Is it within [%]? (c) Thick-thin judgment ... Comparative value is -α5 of 1 / x thick reference value
Is it within + α6 [%]?

<When the ratio is 1: 2.0> -α1 = -α3 = -α5
= -20%, + α2 = + α4 = + α6 = + 50%, and 0.8
It is determined that ≦ narrow width <1.5, 1.6 ≦ thick width <3.0 (both relative values when the narrow width is 1). <When the ratio is 1: 2.5 or 1: 3.0> -α1 = -α3 = -α
5 = -37.5 [%], + α2 = + α4 = + α6 = + 50 [%] Here, when the ratio is 1: 2.5, 0.625 ≦ narrow width ≦ 1.5,
It is determined that 1.56 ≦ thick width ≦ 3.75 (all relative values when the narrow width is set to 1). On the other hand, when the ratio is 1: 3.0, 0.625 ≦ narrow width ≦ 1.5, 1.875 ≦ thick width ≦ 4.5 (all (A relative value when the narrow width is 1).

[0009] As a second conventional method, a reference value for judging the width is prepared, a narrow reference value is prepared for each bar, and a space is prepared for each space. Is determined. That is, in the above example, the first bar B1 of the character a of the NW-7 standard
And the first space S1 is both narrow,
The widths of B1 and S1 are used as narrow width reference values, and the determination of each width is performed as follows. In this case, the reference value is not updated.

[0010]

[Expression 3] 0.5 × Narrow width reference value ≦ Comparison width ≦ 1.5 × Narrow width reference value ・ ・ ・ Narrow width 1.5 × Narrow width reference value <Comparison width ≦ 4.5 × Narrow width reference value ・ ・ ・ Thick width

The above two methods are characterized in that comparison and judgment are made based on the width of one bar or space read. On the other hand, Japanese Patent Application Laid-Open No. 5-165997 discloses a technique for determining the width using an average value of the widths of a plurality of bars and spaces. In this technique, the width of one character is calculated, and the average value of one bar and one space is calculated therefrom. Then, the calculated average value is compared with the size of each bar and space, the width is divided into a wide width and a narrow width, and the width is divided by each number to calculate one width, and a ratio of the narrow width to the wide width is calculated. Things.

[0012]

In the prior art, if the printing accuracy of the barcode is low, it is known that erroneous reading or impossible reading may occur. In any of the above-described techniques, even if there is a local deformation such as a void or a spot in the bar or the space, it is easily affected by the local deformation. The reasons are as follows. First, in the two general techniques described above, one bar and / or one bar
Since the space of the book is used as the reference value, if there is a void or spot there, the width itself is misread and used as a reference. As a result, the thinness is determined based on the erroneous value, resulting in erroneous reading.

Second, a technique for making a width judgment using an average value of the widths of a large number of bars and spaces as described above (Japanese Patent Laid-Open No. Hei 5
165997), the average value serving as a reference differs between a character having a large width and a character having a large width. In the former case, as the number of narrow bars and spaces increases, the average value approaches the narrow value. Therefore, the difference between the average value and the actual narrow width value becomes small, and the narrow width is often misread as a wide width. Conversely, in the latter case, as the number of wide bars and spaces increases, the average value approaches the value of the wide width, and the wide width is often misread as the narrow width.

The above relationship will be described with reference to the bar code shown in FIG. 1 as an example. The barcode in FIG. 1 is the same as the barcode shown in FIG. 6 described above, except that one void is present inside each of the characters a and 1. The void V1 is located at the edge of the first bar B1 of the bar representing the character a, and the void V1 is located at the edge of the second bar B7 of the bar representing the character 1.
2 respectively exist. The ratio of narrow width to wide width is 1:
2.0. Table 1 below shows the result of reading the barcode shown in FIG. 1 by the conventional width determination technology.
In the upper part of the table, the numbers of the display characters, bars and spaces, and the original width values are described. The first row in the lower part of the table describes the actual width value deformed by the void.

[0015]

[Table 1]

In Table 1, what is described as "conventional technology (I)" is that the reference value for width determination is read by updating the bar for each bar and the space for each space. This is the result of performing. In the table
The description “0” indicates that the width is determined to be “narrow”.
1 ”indicates a case where the width is determined to be wide. A portion where the reading is correctly performed is blank. In the start code a, B1 is a narrow width and B is a narrow width.
Since B2 has a large width, B2 is determined based on B1. However, since the width of B2 is at least three times the width of B1, 1.6 ≦
The condition of thick width <3.0 (relative value when the thin width is set to 1) is not satisfied, and B2 is too thick to be determined. Since the B2 determination is impossible, the subsequent determination cannot be performed. However, when the B7 is determined based on the B6, the determination is too small to be performed.
Conversely, in the width determination in the space, since S1 is narrow and S2 is wide in the start code a, S1
Is determined on the basis of. However, since S2 is not more than 1.5 times S1, it satisfies 0.8 ≦ narrow width <1.5 (relative value when the narrow width is 1), and S2 is determined to be narrow. Similarly, when S7 is determined based on S6,
7 is less than 1.5 times S6, and S7 is determined to be narrow.

In Table 1, "prior art (II)" describes a reference value for determining the width, a bar updates the first narrow bar, and a space updates based on the first narrow space. This is a result of reading by a method of making a determination without performing the reading. Since B1 is the narrow width and S2 is the narrow width in the start code a, the subsequent determination is made using these as narrow reference values. In the determination of the bar B3,
0.5 × narrow reference value ≤ comparison width ≤ 1.5 × narrow width reference value, 0.
5 × 12 ≦ 20 ≦ 1.5 × 12, and the formula does not hold.
Narrow width reference value <Comparison width ≤ 4.5 x Narrow width reference value, 1.5 x 12
<20 ≦ 4.5 × 12, which fits this and is determined to be wide. The same applies to B3, B4, B5, and B6. In the determination of the space S2, 0.5 × (narrow reference value) ≦ comparison width ≦ 1.5 × (narrow reference value).
28 ≦ 40 ≦ 1.5 × 28, which fits this and is determined to be narrow. The same applies to S3, S4, and S7.

In Table 1, "prior art (III)" describes a technique for determining the width by using an average value of the widths of a large number of bars and spaces (Japanese Patent Laid-Open No. 5-16).
No. 5997). The character width of the start code a (total of B1 to B4) is 20
It is 0, and the average value per one is 200/7 = 28.6. If the narrow width <28.6 <thick width is determined, the character a can be determined normally. However, for character 1, the average value per character is 180/7 = 25.7, and if a determination is made based on narrow width <25.7 <thick width, a determination error occurs in S6.

As described above, in the conventional technique, there is a problem that the bar and the space are easily affected by local deformation such as voids and spots. Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a barcode reading method and a barcode reading device in which erroneous reading hardly occurs.

[0020]

A first method provided by the present invention is a method of reading a bar code having adjacent narrow bars and narrow spaces in a symbol. Here, the narrow bar and the narrow space mean not only a narrow bar and a space when using a binary level code, but also a bar and a space having one module width when using a multi-level code. At the time of reading a barcode, first, the width in the scanning direction of each of the adjacent narrow bar and narrow space is detected, and an average value of the detected widths is derived. Then, the thickness of each bar and space in the symbol is determined using the derived average value as a determination reference value.

A second method provided by the present invention is a method for reading a bar code having an adjacent narrow bar and a narrow space in a symbol. The thickness of each bar and space in the symbol is determined using a value obtained by multiplying the sum of the width of the bar and space by which the sum of the widths of the spaces is the smallest value by half as a determination reference value. I do. Here, when the sum of the widths of the adjacent bar and space has the smallest value and there are two or more of the same value, any of them may be used as a reference.

Further, a third method provided by the present invention is:
This is a barcode reading method in a case where a plurality of reference characters are predetermined barcodes, and each of the plurality of reference characters has a pair of adjacent narrow bars and narrow spaces. Here, a plurality of reference characters are predetermined, for example, NW
In the -7 code, "a", "
When b "," c ", and" d "represent start and stop codes, they are referred to as comparison targets. Each code of "d" has a portion where the narrow bar and the narrow space are adjacent to each other.In this method, first, the pattern of the set of the adjacent narrow bar and the narrow space existing in any of the reference characters is set to the first pattern.
As a determination criterion, a pattern of a set in which the sum of the widths of the bars and spaces in the scanning direction is the smallest value among the pairs of bars and spaces in the character read first is detected. Compare with one criterion. As a result of the comparison, if the two do not match, the pattern of the narrow bar and narrow space of the other reference character is compared with the pattern of the bar and space of the first read character as a second criterion, and this is repeated until a match is found. . Then, the thickness of the bar and space in the symbol is determined using the value obtained by multiplying the sum of the widths of the bar and space of the matched character in the scanning direction by half as a determination reference value.

The bar code reader provided by the present invention has bar code input means and decoding means for decoding the input bar code, and the decoding means is adjacent to the input bar code. A width detection unit that detects the width of the existing narrow bar and narrow space in the scanning direction, a calculation unit that derives an average value of the detected widths, and a calculation unit that uses the derived average value as a determination reference value to determine the width of each bar and space. A judging unit for judging the thickness.

[0024]

In the first method, the width in the scanning direction of each of the narrow bar and the narrow space adjacent in the symbol is detected, and the average value of the detected widths is derived.
The effects of voids, spots and the like existing inside the two bars and spaces are eliminated, and the effects of local deformation and the like existing at the edges thereof are significantly reduced. Then, the thickness of each bar and space in the symbol is determined using the derived average value as a determination reference value. As a result, misreading and the like are less likely to occur.

In the second method, when deriving the width values of adjacent narrow bars and spaces, the combination in which the sum of the widths of adjacent bars and spaces in the character is the smallest is virtually adjacent. Treat as a narrow width.

In the third method, pattern matching is performed between the position of the set of the bar and space virtually treated as the narrow width and the position of the adjacent narrow set in the character defined as the start code. By doing
The start character can be confirmed, and at the same time, it is confirmed that the read adjacent bar and space are actually narrow.

Further, in the bar code reader of the present invention,
The width detector in the decoding means detects the width in the scanning direction of the narrow bar and the narrow space adjacent to each other among the input barcodes, and derives an average value of each of the detected widths in the calculation unit. The determination unit determines the thickness of each bar and space using the obtained average value as a determination reference value.

[0028]

(First Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to Table 2 and Table 2. FIG. 1 shows a part of a barcode to be read in this embodiment, and is a diagram for explaining a reference width n for width determination in the barcode reading method of the present invention. As already explained,
FIG. 1 shows a barcode of the NW-7 standard in which "a" is used as a start character and "1" is described as a subsequent character. In the figure, B1 to B9 and S1 to S8 are bar and space identification numbers, respectively, and V1 and V2 are voids formed at positions where the scanning lines on the bars B1 and B7 pass, respectively.

[0029]

[Table 2]

As shown in the upper part of Table 2, the original width value of each bar is the narrow bar (B1, S1, B3, B4,
For B5, S5, B6, S6, and B7), it is "20", and the bar (B2, S2, S3, S4, S
7, B8) is "40". On the other hand, the width value actually measured is deformed under the influence of the voids V1 and V2, and becomes the value shown in the lower part of Table 2. The width value of the void V1 on the scanning line is “8”, and the width value of the bar B1 is changed to “12” and the width value of the space S1 is changed to “28” under the influence. Further, since the width value of the void V2 is “9”, the width value of the space S6 is changed to “29” and the width value of the bar B7 is changed to “11” under the influence.

FIG. 2 is a schematic configuration diagram of a bar code reader according to one embodiment of the present invention. The bar code reader includes a bar code input unit 10 for inputting a bar code,
The apparatus includes a decoding unit 1 that decodes an input barcode, and an encoding device 15 that encodes decoded information and outputs the encoded information. The input unit 10 includes a scanning unit 11 that optically scans the surface of the barcode symbol 20, a light receiving unit 12 that receives reflected light and amplifies the video, and an A / D that converts the amplified analog signal into a digital signal. The decoding unit 1 includes a conversion unit 13 and a digital signal analysis unit 14 that analyzes a digital signal and outputs a pulse data train. The decoding unit 1 is configured to scan adjacent bar narrow bars and narrow spaces in an input bar code in the scanning direction. , A calculating unit 3 for deriving an average value of each detected width, and a determining unit 4 for determining the thickness of each bar and space using the derived average value as a determination reference value. Consists of

The above function of the decoding unit 1 is specifically realized by a central processing unit (CPU), required programs and data. FIG. 3 is a processing procedure diagram of the decoding unit 1 when reading a barcode in the barcode reading device having the above configuration. Hereinafter, this processing procedure will be described with reference to FIG.

The width detecting section 2 in the decoding section 1 measures each pulse width based on the pulse data train sent from the digital signal analyzing section 14 and detects the sum of adjacent narrow widths from the measured pulse width (see FIG. 1). S100). There are various methods for detecting the sum of the narrow widths. In this embodiment, the following procedure is used. That is, the total width of adjacent bars and spaces is calculated based on the measured pulse widths (S10).
1) A combination of a bar and a space that takes the minimum value among them is treated as an adjacent narrow width (S102). FIG.
In the bar code shown in FIG.
The sum of S1 is the width value “40”, which is the minimum width for the adjacent bar and space. By the way, the minimum width including the character 1 is B5 + S5, S5 +
B6 and S6 + B7 have a width value of “40”, and both have the minimum width. From the total of the extracted minimum widths, an average value n of the narrow width per line is obtained (S300). Here, the width value of n is “20”.

Next, the thickness of each bar and space is determined using the average value n as a reference value (S400). In the present embodiment, since the barcode to be read is a barcode conforming to the NW-7 standard, the determination of the thickness is to determine whether the barcode is narrow or wide. 0.5 times or more 1.5 times the standard value (average value) n
A range less than or equal to twice is defined as a narrow width (S401, S402), and 1.5
A range exceeding twice and not more than 4.5 times is determined to be a wide width (S40).
3, S404). The result of each determination is encoded by the coder / decoder circuit in the encoding device 15 (S500).
Is output.

(Second Embodiment) Next, FIG. 4 shows an embodiment in which pattern matching is performed for the position of a set of adjacent narrow bars and spaces in a start code.
A description will be given also with reference to FIG.

FIG. 4 is a diagram showing a part of a bar code to be read in this embodiment, and shows an example in which a start code b of the NW-7 standard is used. There is a void V3 on the scanning line of the bar B3. The other points are the same as the barcode shown in the first embodiment (see FIG. 1). FIG. 5 is a barcode reading procedure according to this embodiment. The width determination procedure in this embodiment is as follows.
The procedure is the same as the procedure shown in FIG. 3 except that a position collation procedure (S200) of adjacent narrow sets is added.

That is, in this embodiment, after detecting the widths of adjacent narrow bars and spaces (S100 to S100).
2) a pattern of a set of the narrow bar and space;
Matching is performed with a pattern of adjacent narrow bars and spaces in a plurality of reference characters that are predetermined to be used for the start code and the stop code (S200). First, from the first character described in the symbol, the position and width value of a bar / space pair that minimizes the total width of adjacent bars and spaces are detected (S100). In this embodiment, since the start code b is used for the symbol, the sum of the bars and spaces adjacent to each other at the narrow width is the position of B3 + S3. Next, in each of the codes "a", "b", "c", and "d" that can be used as a start character, the collation between the adjacent narrow bar and space and the detected position B3 + S3 is sequentially performed. (S201
To S204). First, since the start character a is the code "0011010" (0 represents a narrow width and 1 represents a wide width), narrow widths are adjacent to each other at the top bar and space; B1 + S1. Therefore, the result of collation is "N
o "(S201), and the process shifts to the collation with the start character b.
01001 ”, the narrow width is adjacent to B3 + S3. Therefore, the result of the collation is “Yes” (S202), and the process proceeds to the calculation of the average value (S300) and the determination of the thickness (S401).

Although not shown in FIG. 5, the code read based on the determined thickness may be re-collated with the code of the start character. In the barcode of the NW-7 standard, the start characters "a", "
c ”and“ d ”are both the leading bar and space B2
Since + S1 is narrow, in practice, S203 and S20
Step 4 is the same procedure as step S201. Here, the procedure of collation with all start characters is schematically shown.

[0039]

As is apparent from the above description, according to the bar code reading method of the present invention, the average value of the widths of adjacent narrow bars and spaces becomes the reference value for the width judgment. Even if there are voids and spots inside the reference bar and the space, the barcode can be read without being affected by such voids and spots, so that there is an effect that erroneous reading is prevented.

In the bar code reader of the present invention,
Among the barcodes input by the width detection unit in the decoding means, the width of the narrow bar and the narrow space adjacent to each other in the scanning direction are detected, and the average value of the detected widths is derived. Since the thickness of each bar and space is determined, even if there are voids and spots inside the bar and space, the bar code can be read without being affected by them.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a part of a barcode to be read in a barcode reading method according to the present invention, and is a diagram for describing an average value of a narrow width which is a width determination reference value.

FIG. 2 is a schematic configuration diagram of a barcode reading device according to an embodiment of the present invention.

FIG. 3 is a flowchart showing characteristics of a bar code reading procedure by the bar code reading device.

FIG. 4 is a diagram showing a bar code to be read for explaining a bar code reading method according to another embodiment of the present invention.

FIG. 5 is a flowchart showing characteristics of a barcode reading procedure shown in FIG. 4;

FIG. 6 is a diagram showing a bar code to be read in a conventional bar code reading method.

[Explanation of symbols]

 n Average value of narrow width B1 to B9 Bar S1 to S8 Space V1 to V3 Void 1 Decoding unit 2 Width detection unit 3 Operation unit 4 Judgment unit 10 Barcode input unit 11 Scanning unit 12 Light receiving unit 13 A / D conversion unit 14 Digital Signal analysis unit 15 Encoding device 20 Barcode symbol

Claims (4)

(57) [Claims] 1. A bar code reading method in which a narrow bar and a narrow space are present adjacent to each other in a symbol, wherein the width of each of the adjacent narrow bar and the narrow space in the scanning direction is detected, and the detected width is detected. A bar code reading method, wherein an average value of the bar code is derived, and the thickness of each bar and space in the symbol is determined using the derived average value as a determination reference value. 2. A method of reading a barcode in which a narrow bar and a narrow space are adjacent to each other in a symbol, wherein the sum of the widths of the adjacent bars and spaces among the bars and spaces in the symbol is set to the smallest value. A bar code reading method comprising: determining the thickness of each bar and space in a symbol by using a value obtained by multiplying the sum of the widths of the bar and space by half as a determination reference value. 3. A bar code reading method in which a plurality of reference characters each including a pair of adjacent narrow bars and narrow spaces are predetermined, wherein a plurality of reference characters include a pair of adjacent narrow bars and narrow spaces existing in any of the reference characters. Using the pattern as a first determination criterion, a pattern of a set having the smallest value of the sum of the widths of the bars and spaces in the scanning direction is detected from among the pairs of bars and spaces in the character read first, and The pattern is compared with the first criterion. If the two do not match, the narrow bar and narrow space pattern of the other reference character are compared with the bar and space pattern of the first read character as the second criterion. , The sum of the width of the bar and space of the matched character in the scanning direction multiplied by half Bar code reading method characterized by determining the thickness of the bars and spaces in a symbol as a determination reference value. 4. A bar code input means, and a decoding means for decoding the input bar code, wherein the decoding means has a width in the scanning direction of an adjacent narrow bar and a narrow space of the input bar code. A width detection unit for detecting
A bar code comprising: a calculation unit for deriving an average value of each detected width; and a determination unit for determining the thickness of each bar and space using the derived average value as a determination reference value. Reader.