JP2742920B2 - Barcode reader - 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 reader for reading a binary bar code.

[0002]

2. Description of the Related Art In recent years, barcodes have been used for inventory management for most of distribution products. This barcode is composed of a combination of thin lines and thick lines and the number of the lines, and is printed or affixed to the surface of a product or the like.These barcodes are generally captured by a barcode scanner using red visible light, and are read. Whether the decoder can accurately read the data as numbers or characters determines the performance of the decoder.

FIG. 8 shows a flow of a decoding process for one character. In the figure, (S8-1) is a minimum value (N) and a maximum value from among K bars / spaces constituting one character.
(S) is a process of calculating a threshold (T) from N and W in one character, and (S8-3) is a process of calculating K values from the threshold (T). The process of calculating the narrow / wide of the bar / space, and the process (S8-4) is the process of converting one character narrow / wide into ASCII using the conversion table.

When the type of code is CODE39, K = 9, when NW7, K = 7, when ITF is K = 10, K = 10 with two character pairs, and when CODE11, K = 5. It should be noted that the two character pairs of the ITF are
This is because both spaces are required.

[0005]

In the prior art, when reading a bar code, ink bleeding during printing,
Variations in the scanning speed of the pen scanner, the curvature of the label printing surface, etc. become problems, and the width of the bar / space fluctuates in a complicated manner. For this reason, how to set a threshold value for judging narrow / wide of the width from the width of the taken bar / space becomes a problem.

[0006] Generally, a bar /
The average of the maximum width and the minimum width in the space is used as the threshold. However, with such a threshold value, the scanning speed variation and the curvature of the printing surface can be synchronized in units of characters, so that reading is easy.
Since the space ratio deviates from the standard, it is necessary to correct this at the time of reading so that reading can be performed correctly.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bar code reader capable of reading correctly even if the bar / space ratio is deviated from a standard due to ink bleeding or the like when printing a bar code label.

[0008]

In order to achieve the above object, a bar code reader according to the present invention comprises a binary level bar code comprising a character including a narrow bar / space and a wide bar / space. A bar code reader that reads a minimum value for each bar / space from a plurality of count values that constitute one character.
(NB, NS) and a minimum / maximum value calculation circuit for obtaining a maximum value (WB, WS); a narrow average calculation circuit for obtaining an average value (M) of narrow count values from the NB and NS;
A threshold value calculating circuit for obtaining a threshold value for binary discrimination based on the average value (TB) of B and the average value (TS) of WS and NS; And a binary code conversion circuit for converting into a sequence of

Also, among the elements constituting one character, the absence of a wide element in either the bar or the space is determined by the threshold value of the bar NB + (M / 2) or the threshold value of the space NS + (M / 2), the value corresponding to the wide element is calculated as WB = WS + NB
-NS or WS = WB + NS-NB.

When the bar count value is equal to or less than J times the average value of the narrow count value (M) + NB, or when the count value of the space is J times the average value (M) of the narrow count value. When NS is equal to or less than + NS, the data is made valid, and the other means is made invalid.

When converting to a binary code, a readable range of the bar / space ratio in the narrow count value (NB, NS) is determined, and when exceeding this range, the data of the character is invalidated. It is characterized by having means.

In the binary code conversion circuit, the threshold count (TB, TS) is used to read the width count value of the start bar / space or the stop bar / space adjacent to the character by 2 in the 2of5 system. It is characterized by conversion into a series of value codes.

[0013]

According to the bar code reader having the above-mentioned structure, the bar / space is separated for each character and discriminated, so that even if the ratio of the bar / space is different, the bar / space can be correctly read without any influence.

When a wide bar or a wide space does not exist in one character in order to separate and distinguish a bar / space (CODE39, NW7, 2of5),
By calculating from the other bars / spaces in the same one character by the above formula, the bar / space ratio can be correctly read even if the bar / space ratio is different.

A readable range of the count value is provided for each character in a bar / space separately. If the count value does not fall within this range, it is assumed that noise other than the bar code label has been read and an error is determined.

Further, in order to separate and discriminate the bar / space, a readable range is provided in the bar / space ratio of the narrow element. If the range does not fall within this range, noise other than the bar code label is read. Judge as an error.

As a method of discriminating a start bar / space or a stop bar / space that does not constitute a character as in 2of5, discrimination is performed using a threshold value of an adjacent character, thereby affecting the effect of a change in the scanning speed of the scanner. Since it is hard to receive, it can be read correctly.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system block diagram of a bar code reader according to the present invention, in which 11 is a light source, 12 is a bar code label, 13 is a reading optical system, 14 is an analog processing system, 15 is a decoding processor, and 16 is a decoding processor. Is a communication interface.

FIG. 2 shows a first embodiment of a bar code reader according to the present invention.
21 is a control block diagram of the embodiment, 21 is a scanner, 22 is a pulse width counting circuit, 23 is a pulse width storage circuit, 24 and 25 are minimum and maximum value calculation circuits, 26 is a narrow average calculation circuit, and 27 is a bar threshold. An operation circuit, 28 is a space threshold value operation circuit, 29 is a binary code conversion circuit, and 30 is an ASCII character conversion circuit.

FIG. 3 is an operation flowchart of the first embodiment. (S3-1) shows the minimum value (NB, NS) for each bar / space from among the count values of the bar / space constituting one character. The process of finding the maximum value (WB, WS), (S3-2) is the process of finding the average value (M) of the narrow count value from each minimum value of the bar / space, and (S3-3) is the process of finding the bar / space.
A process for obtaining a threshold for binary discrimination based on the average value of WB and NB (TB) or the average value of WS and NS (TS) for each space, and (S3-4) a threshold value for each bar / space The binary code (wide →
(S3-5) is a process for converting to ASCII characters using a conversion table.

FIG. 4 is a flowchart showing the operation of the second embodiment of the present invention. Among the elements constituting one character, a wide element (W
B or WS) is not present, the bar threshold N
B + (M / 2) or space threshold NS + (M / 2)
, The value corresponding to the wide element is represented by W
A process of calculating from B = WS + NB-NS or WS = WB + NS-NB is performed in (S4-1) to (S4-3).

FIG. 5 is a flowchart showing the operation of the third embodiment of the present invention. In order to prevent erroneous reading due to noise other than bar codes, the bar count value is equal to or less than N times the average value (M) of narrow count values + NB (NB). If the count value of the space is less than (less than) N times + NS of the average value (M) of the narrow count value, the data is valid,
Otherwise, invalidation processing is performed in (S5-1) to (S5-3).

FIG. 6 is a flowchart showing the operation of the fourth embodiment of the present invention. In order to enhance the effect of preventing erroneous reading, a narrow bar / space (NB, NS) in one character is converted into a binary code. A range in which the bar / space ratio can be correctly read is determined, and when the range exceeds this range, the processing of invalidating the data of the character is performed from (S6-1) to (S6-).
Perform in 3). L in FIG. 6 is a bar / space ratio control.
Indicates the limit value (0 to 1).

FIG. 7 is a layout diagram of a 2 of 5 series bar code. In reading of 2 of 5 series, a start bar / space or a stop bar adjacent to the character is determined by using the threshold values (TB, TS) obtained above. / Space width count value is binary code (wide → 1, narrow → 0)
Perform a process of converting to a list of

[0026]

As described above, according to the first aspect of the present invention, when a wide bar / space and a narrow bar / space are present in one character, a bar code label is provided. Even if the bar / space ratio deviates from the standard due to ink bleeding or the like at the time of printing, it can be correctly read by correcting this.

According further to the first aspect of the present invention, even in the code that may wide bar or wide space does not exist in one character, the same effect as described above can be obtained.

According to the second aspect of the present invention, the bar / space count value is provided separately for each character so that the bar / space ratio can be correctly read even if the bar / space ratio deviates from the standard. Misreading due to noise other than the label can be prevented.

According to the third aspect of the present invention, by providing a readable range of the narrow bar / space ratio range for each character, the range of the readable bar / space ratio is narrowed, but the label is accordingly reduced. Misreading due to other noises can be prevented.

According to the fourth aspect of the present invention, when discriminating a start bar / space or a stop bar / space that does not constitute one character, the scanning speed of the scanner is determined by using a threshold value obtained from an adjacent character. Can be distinguished without being affected by changes in

[Brief description of the drawings]

FIG. 1 is a system block diagram of a barcode reader according to the present invention.

FIG. 2 is a control block diagram of a first embodiment of the barcode reader according to the present invention.

FIG. 3 is an operation flowchart of the first embodiment.

FIG. 4 is an operation flowchart of a second embodiment of the present invention.

FIG. 5 is an operation flowchart of a third embodiment of the present invention.

FIG. 6 is an operation flowchart of a fourth embodiment of the present invention.

FIG. 7 is a layout diagram of a 2of5 barcode.

FIG. 8 is a flowchart showing a decoding process of one character.

[Explanation of symbols]

24, 25: minimum and maximum value calculation circuit, 26: narrow average calculation circuit, 27: bar threshold value calculation circuit, 28: space threshold value calculation circuit, 29: binary code conversion circuit.

Claims (4)

(57) [Claims] 1. A bar code reader for reading a binary level bar code composed of characters including a narrow bar / space and a wide bar / space, a plurality of count values constituting one character. , A minimum / maximum value calculation circuit for obtaining a minimum value (NB, NS) and a maximum value (WB, WS) for each bar / space, and an average value (M) of narrow count values from the minimum values NB and NS. , An average value (TB) of the maximum and minimum values WB and NB, and WS and N
A threshold calculation circuit for obtaining a threshold value for binary discrimination by the mean value of S (TS), constituting one character
In the element, either WB or bar / space
Or the absence of WS is indicated by a bar threshold NB +
(M / 2) or space threshold NS + (M / 2)
, The phase corresponding to this WB or WS
Set this value to WB = WS + NB-NS or WS = WB + N
A bar code reader, comprising: a binary code conversion circuit that calculates a value from S-NB and converts the value into a sequence of binary codes using a threshold value as a criterion separately for each bar / space. 2. The bar count value is equal to the narrow count value.
When the average value (M) is less than or less than J times + NB
Or the count value of the space is the narrow count value
Is less than or less than J times the average value (M) of NS + NS
Means to validate the data and invalidate the rest.
2. The bar code reading device according to claim 1, wherein
Place. 3. Narrow count when converting to binary code
Bar / space ratio in value (NB, NS) is legible
If you exceed this range, the character
A means for invalidating the data of
The barcode reader according to claim 1. 4. The binary code conversion circuit according to claim 2, wherein
In reading, the threshold (TB, TS) is used
Start bar / space adjacent to character or
Stop bar / space width count value
The bar code according to claim 1, wherein the bar code is converted into a column.
Reader.