JP2750244B2 - Barcode decoder decoding method - 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 decoder for decoding a binary signal obtained by optically reading a bar code symbol.

[0002]

2. Description of the Related Art ECR (electronic cash register) and POS (point-of-sale information) terminals connected to a barcode reader are installed at mass retailers such as supermarkets, and are used for registering product sales data. . That is, a barcode label printed or affixed to a product is optically read by a barcode reader, and the read data is transferred to an ECR or POS terminal as a host device. The registration processing of merchandise sales data is performed based on this.

A bar code reader used for such a device optically reads a bar code symbol of a bar code label with a sensor, photoelectrically converts the bar code symbol, and binarizes an obtained electric signal with a binarization circuit. A bar code decoder decodes the characters into characters such as numerals, alphabets, and symbols, and transfers the characters to an ECR or POS terminal.

As an optical reading method, a bar code label is scanned by irradiation light such as a laser beam, and the intensity of the reflected light is read by a sensor. The bar code label is irradiated with light from an LED (light emitting diode). A method of scanning the reflected light with a one-dimensional line sensor, a method of scanning a barcode label by hand with a pen type scanner provided with a light emitting element and a light receiving element as a pair, and the like are known.

The bar code symbol of the bar code label is composed of a combination of a bar B and a space S as shown in FIG. 4A, and by scanning this, the edge of the boundary between the bar and the space is detected and the edge is detected. Measure the interval,
A binary signal as shown in FIG. 4B having a width value corresponding to the bar width and the space width of the bar code symbol is obtained. The binarized signal is input to a barcode decoder as a barcode signal and decoded.

The decoding process is performed based on FIG.

First, an incoming margin check is performed. Various checks are known as this check. For example, a value obtained by multiplying a space width at a position assumed as a margin and a total width of a predetermined number of bars and spaces corresponding to the first character following the space by a coefficient is used. And if the space width is larger, consider this as the correct margin.

Next, the first character is decoded, and it is checked whether this character is a start character or a stop character. It can be understood that the reading in the forward direction is established when the character is established as the start character, and the reading in the backward direction is established when the character is established as the stop character. At this time, if the first character is not established as a start character or a stop character, it is determined that the signal is not a correct barcode signal, and the data is invalidated. For example, when the bar code symbol shown in FIG. 4A is scanned from left to right in the figure, a start character is detected following the margin.

Next, the data character is decoded in the same manner as the start character and the stop character, and it is checked whether the character is the start character or the stop character. If it is not a start character or a stop character, it is sequentially decoded as a data character.

When the stop character is decoded at the time of forward reading in which the start character is detected first, it is regarded that the data of one label is completed. When the start character is decoded at the time of the backward reading in which the stop character is detected first, it is considered that the data of one label is completed.

Finally, the output margin is detected, and if the margin is correctly established, the decoding of one barcode symbol ends.

As a specific example, a method of decoding a barcode data character of NW7 in which one character is composed of four bars and three spaces will be described.

As shown in FIG. 6, among the four bars and three spaces in one character, the largest width bar and the largest width space are searched.

Next, all the bar widths are compared with the reference value using 5/8 of the maximum bar width as a reference value. If the bar width is not less than the reference value, it is regarded as a wide bar, and if smaller than the reference value, it is regarded as a narrow bar.

Next, if only one of the four bars is wide, 5/8 of the maximum space width is used as a reference value, and all space widths are compared with the reference value. If it is smaller than the reference value, it is regarded as a narrow space.

If three of the four bars are wide, it is confirmed that the width of each space is larger than the reference value. In this case, all spaces are regarded as narrow spaces.

Next, "0" is assigned to the narrow element and "1" is assigned to the wide element to create a 7-bit binary number.

Finally, NW7 shown in Table 1 is a 7-bit binary number.
Compare with the character table to find the character value.

The NW7 character including the start character and the stop character is decoded by the above algorithm.

[0020]

[Table 1]

[0021]

When a bar code symbol is read and binarized by a binarizing circuit, the characteristic of the binarizing circuit immediately follows a long space as shown by a in FIG. May be wider than the actual waveform.
That is, when the first bar width of the first character after the margin is not correctly reproduced. In such a case,
Since the first character is no longer a start character and a stop character, even if all subsequent data is correct, it is not recognized as a correct bar code signal. For this reason, there has been a problem that decoding efficiency is deteriorated and a reading rate is reduced.

Accordingly, an object of the present invention is to provide a decoding method of a bar code decoder capable of efficiently decoding bar code data and thus improving a reading rate.

[0023]

According to the present invention, there is provided a bar code decoder for decoding a binary signal obtained by optically reading a bar code symbol, except for a bar except for a first bar adjacent to a margin. The first character following the margin is decoded by the bar and space
And start character or stop character
It is to recognize .

[0024]

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

As shown in FIG. 1, a binarized signal obtained by optically reading a bar code symbol of a bar code label is input to a bar width counting circuit 1, and the bar width and the space width are counted by a reference clock number. , The count value is RA
M (random access memory) 2.

Reference numeral 3 denotes an MPU (microprocessor unit). The MPU 3 reads a count value corresponding to the bar code stored in the RAM 2, converts the bar code data into binary data from the count value, and further stores the read data in the ROM 4. The bar code is converted into a character value based on the stored character table, and when all the character values of the barcode are normally converted, the decoding result is converted to ECR or P.
The data is transferred to the host device 5 such as an OS terminal.

The ROM 4 stores the character table shown in Table 1 and the start and stop character tables shown in Table 2. In Table 2, (F) shows a binary number and a character at the time of forward reading, and (B) shows a binary number and a character at the time of backward reading.

[0028]

[Table 2]

The MPU 3 decodes, for example, the start / stop character of the bar code of the NW 7 based on the flowchart shown in FIG.

First, among the three bars and the three spaces except the first one bar in the start / stop character, the largest width bar and the largest width space are searched.

Next, all bar widths are compared with the reference value using 5/8 of the maximum bar width as the reference value. If the bar width is equal to or larger than the reference value, the bar is regarded as a wide bar, and if smaller than the reference value, it is regarded as a narrow bar.

If all the bars are not equal to or larger than the reference value, then all the space widths are compared with the reference value using 5/8 of the maximum space width as the reference value. If it is smaller, it is considered a narrow space.

When all the bars are equal to or larger than the reference value, all the bars are regarded as narrow. This processing is performed when characters B and C, which are start / stop characters, are read in the reverse direction. Then the maximum space width of 5
All space widths are compared with the reference value using / 8 as a reference value. If the space width is equal to or larger than the reference value, it is regarded as a wide space, and if smaller than the reference value, it is regarded as a narrow space.

Next, "0" is assigned to the narrow element and "1" is assigned to the wide element to create a 6-bit binary number.

Finally, the 6-bit binary number is compared with a start and stop character table shown in Table 2 to determine a character value. If the obtained character value is correct as a start / stop character, it is regarded as a valid start / stop character.

The start / stop character which is the first character is decoded by the above algorithm.

The decoding process of FIG. 6 described above is performed for the second and subsequent characters. In this case, finally compare the 7-bit binary number with the character table shown in Table 1.
The character value will be determined.

In the embodiment having such a configuration, the first
For the character, three bars excluding the four bars that make up one character and the first one of the three spaces
The bar and the three spaces are validated, and the bar and the space reference value are obtained by searching the maximum width bar and the space from the six bars / spaces. Then, the narrow bar and the wide bar are determined by comparing the reference value with the six bars / spaces, and the narrow bar is set to "0" and the wide bar is set to "1" to form a binary number. Convert.

Therefore, even if the first bar width of the first character is not correctly reproduced due to the characteristics of the binarization circuit, the bar width does not contribute to decoding at all, and the decoding of the first character can be performed without any trouble. Will be Therefore, barcode data can be efficiently decoded, and the reading rate can be improved.

Next, another embodiment of the present invention will be described with reference to the drawings.

This embodiment describes the decoding process of the start / stop character of the CODE39 bar code. The CODE39 barcode is composed of five bars and four spaces per character.

In the case of a CODE39 bar code, the decoding process shown in FIG. 3 is performed.

First, of the four bars and the four spaces except the first one bar in the start / stop character, the largest bar and the largest space are searched.

Next, all bar widths are compared with the reference value using 5/8 of the maximum bar width as a reference value. If the bar width is not less than the reference value, it is regarded as a wide bar, and if smaller than the reference value, it is regarded as a narrow bar.

Next, all the space widths are compared with the reference value using 5/8 of the maximum space width as the reference value. If the space width is larger than the reference value, it is regarded as a wide space, and if smaller than the reference value, it is regarded as a narrow space.

Next, "0" is assigned to the narrow element and "1" is assigned to the wide element to create an 8-bit binary number.

Finally, the 8-bit binary number is compared with the start and stop character tables shown in Table 3 to determine a character value. If the obtained character value is correct as a start / stop character, it is regarded as a valid start / stop character.

The start / stop character which is the first character is decoded by the above algorithm.

[0049]

[Table 3]

Also in this embodiment, for the first character, four bars and four bars excluding the first bar of the five bars and four spaces constituting one character.
The book space is validated, and the bar and space reference values are obtained by searching for the maximum width bar and the maximum width space from the eight bars / spaces. The narrow bar and the wide bar are determined by comparing the reference value with the eight bars / spaces, and the narrow bar is set to "0" and the wide bar is set to "1".
Create a hexadecimal number and convert the binary number to a character value according to Table 3.

Therefore, even if the first bar width of the first character is not correctly reproduced due to the characteristics of the binarization circuit, the bar width does not contribute to decoding at all. A similar effect can be obtained.

The above-described embodiment is based on NW7 and CODE3.
9 has been described, but the present invention is not necessarily limited to this.
It can be applied to decoding of barcodes having start / stop characters such as E93.

[0053]

As described above, according to the present invention, the first start character and the stop character are decoded by the remaining bars and spaces except for the first bar adjacent to the margin, so that the bar code data can be efficiently processed. Decoding, thus improving the read rate.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart showing decoding processing of a start / stop character in the embodiment.

FIG. 3 is a flowchart showing a decoding process of a start / stop character in another embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a barcode pattern and a corresponding binary signal.

FIG. 5 is a flowchart showing a basic decoding process of a decoder.

FIG. 6 is a flowchart showing a conventional NW7 decoding process.

[Explanation of symbols]

2 ... RAM (random access memory), 3 ... MP
U (microprocessor unit), ROM (read
Only memory).

Claims (1)

(57) [Claims] 1. A bar code decoder for decoding a binarized signal obtained by optically reading a bar code symbol, wherein a bar and a space other than a first bar adjacent to the margin are firstly arranged following the margin . Decode character and start character or
Is a bar code decoder decoding method that recognizes a stop character.