JPH06103394A - Decoding method for bar-code decoder - Google Patents

Abstract

PURPOSE:To enhance a read rate by decoding efficiently bar-code data. CONSTITUTION:For instance, an NW 7 searches a bar of the maximum width and a space of the maximum width in six pieces of bars/spaces except a first one piece of bar in start/stop characters. Subsequently, a reference value is derived from the maximum bar width, and the bar is regarded as a wide bar, and a narrow bar, when the bar width exceeds the reference value, and when it is smaller than the reference value, respectively. Also, a reference value is derived from the maximum space width, and the space is regarded as a wide space, and a narrow space, when the space width exceeds the reference value, and when it is smaller than the reference value, respectively. Next, by allocating '0' to a narrow element, and allocating '1' to a wide element, a binary number of 6 bits is generated, and by comparing its binary number with a start and stop character table, a character value is derived.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decoding method of a bar code decoder for decoding a binarized 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 management) terminals to which bar code readers are connected are installed in mass retailers such as supermarkets and used for registering product sales data. . That is, the bar code label printed or affixed to the product is optically read by the bar code reading device, the read data is transferred to the ECR or POS terminal as a host device, and the transferred data is transferred to the ECR or POS terminal. Based on this, registration processing of product sales data is performed.

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

As an optical reading method, a bar code label is scanned with irradiation light such as a laser beam, and the intensity of reflected light is read by a sensor. Light from an LED (light emitting diode) is applied to the bar code label. A method of scanning the reflected light with a one-dimensional line sensor, a method of manually scanning and reading a bar code label with a pen type scanner provided with a light emitting element and a light receiving element as a pair 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. 4 (a). By scanning this, the edge of the boundary between the bar and the space is detected to detect the edge. Measure the distance,
A binarized signal as shown in FIG. 4 (b) having a width value corresponding to the bar width and space width of the bar code symbol is obtained. Then, this binarized signal is input to the bar code decoder as a bar code signal and decoded.

This decoding process is performed based on FIG.

First, an entry margin check is performed. Although various checks are known as this check, for example, a space width at a position assumed to be a margin, and a value obtained by multiplying a total width of a predetermined number of bars and spaces corresponding to the first character following the space by a coefficient. And consider this as the correct margin when the space width is larger.

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

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. Unless it is a start character or a stop character, it is sequentially decoded as a data character.

When the stop character is decoded during the forward reading in which the start character is first detected, it is considered that the data of one label is completed. Further, when the start character is decoded in the backward reading in which the stop character is first detected, 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 bar code symbol is completed.

As a concrete example, a decoding method of a data character of a bar code of NW7 in which one character consists of four bars and three spaces will be described.

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

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

Next, if only one of the four bars is wide, all space widths are compared with the reference value with 5/8 of the maximum space width as a reference value. If it is smaller than the standard value, it is regarded as 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 considered 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, the NW7 shown in Table 1 is a 7-bit binary number.
Calculate the character value by comparing with the character table.

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 the binarization circuit, it is immediately after a long space as shown by a in FIG. 4 (c) due to the characteristics of the binarization circuit. The bar width of may be thicker than the actual waveform.
That is, the first bar width of the first character immediately after the margin may not be reproduced correctly. In such cases, the first
Since the character is not established as the start character and the stop character, even if all the data thereafter is correct, it cannot be recognized as a correct bar code signal. Therefore, there is a problem that the decoding efficiency is deteriorated and the reading rate is lowered.

Therefore, the present invention is intended to provide a decoding method of a bar code decoder which can efficiently decode bar code data and thus improve the reading rate.

[0023]

SUMMARY OF THE INVENTION The present invention is a bar code decoder for decoding a binarized signal obtained by optically reading a bar code symbol, and the remainder except for the first bar adjacent to the margin. It consists in decoding the first start and stop characters by the bars and spaces.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 space width are counted by a reference clock number. , The count value is RA
It is adapted to be stored in M (random access memory) 2.

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

The ROM 4 stores the character table of Table 1 and the start and stop character table of Table 2 described above. In Table 2, (F) shows a binary number and a character when reading in the forward direction, and (B) shows a binary number and a character when reading in the backward direction.

[0028]

[Table 2]

The MPU 3 decodes the start / stop characters of the NW7 bar code, for example, based on the flow chart shown in FIG.

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

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

If all bars are not above the reference value, then all space widths are compared with the reference value with 5/8 of the maximum space width as the reference value. If it is small, it is considered as a narrow space.

When all the bars are above the reference value, all the bars are regarded as narrow. This processing is intended when the 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 with / 8 as the reference value. If the 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 the start and stop character table shown in Table 2 to obtain the character value. If the obtained character value is correct as a start / stop character, this is regarded as a valid start / stop character.

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

For the characters after the second character, the decoding process shown in FIG. 6 is performed. In this case, finally, compare the 7-bit binary number with the character table shown in Table 1,
The character value will be obtained.

In the embodiment having such a configuration, the first
About the character 3 excluding the 4 bars that make up one character and the first 1 bar of the 3 spaces
The bar of the book and the space of 3 are validated, the bar of the maximum width and the space of the maximum width are searched from the 6 bars / space, and the reference value of the bar and the space is obtained. Then, the narrow bar and wide bar are determined by comparing the standard value with 6 bars / spaces, a binary number is created by setting the narrow bar to "0" and the wide bar to "1", and the binary number is converted into a character value according to Table 2. Convert.

Therefore, even if the first bar width of the first character is not reproduced correctly due to the characteristics of the binarization circuit, the bar width does not contribute to the decoding at all, so that the decoding of the first character can be performed without any trouble. Will be seen. Therefore, the 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 CODE 39 bar code is composed of five bars and four spaces for one character.

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

First, among the four bars and the four spaces excluding the first one bar in the start / stop character, the maximum width bar and the maximum width space are searched.

Next, all the bar widths are compared with the reference value with 5/8 of the maximum bar width as the reference value. If the bar width is equal to or larger 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 space widths are compared with the reference value with 5/8 of the maximum space width as the reference value. If the 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 an 8-bit binary number.

Finally, the 8-bit binary number is compared with the start and stop character table shown in Table 3 to obtain the character value. If the obtained character value is correct as a start / stop character, this 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, four bars and four excluding the first bar out of the five bars and the four spaces forming one character for the first character.
The space of the book is validated, the bar of the maximum width and the space of the maximum width are searched from the eight bars / spaces, and the reference value of the bar and the space is obtained. Then, the narrow bar and wide bar are decided by comparing the standard value with 8 bars / spaces, and the narrow bar is set to "0" and the wide bar is set to "1".
A base number is created and the base number is converted into a character value according to Table 3.

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

In the above embodiment, NW7 and CODE3 are used.
Although the decoding of the barcode of 9 has been described, it is not necessarily limited to this, and CODE128 and CODE can be used.
It can be applied to the decoding of bar codes 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 bar and space except the first bar adjacent to the margin, so that the bar code data can be efficiently processed. It can be decoded and thus the read rate can be improved.

[Brief description of drawings]

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

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

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

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

FIG. 5 is a flowchart showing basic decoding processing 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)

[Claims] 1. A bar code decoder for decoding a binarized signal obtained by optically reading a bar code symbol, wherein a first start character and a space are provided by a remaining bar and a space except a first bar adjacent to a margin. A decoding method for a bar code decoder characterized by decoding a stop character.