JPH05189596A - Bar code demodulating device - Google Patents

Abstract

PURPOSE:To improve the bar code read precision by using data obtained by incomplete scanning of a light beam with respect to a bar code demodulating device which scans the light beam on a bar code consisting of single or plural blocks and reads the reflected light to demodulate the bar code. CONSTITUTION:The bar width of the bar code is detected by a bar width counter 1 to perform demodulation in a demodulating part 3; and meanwhile, the range and the direction of scanning of the light beam are recognized in a recognition part 2 based on the output of the bar width counter 1, and read data of the completely scanned block is demodulated based on the recognition result, and next, read data of blocks which precede and succeed this block and are incompletely scanned are demodulated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to improvements in bar code demodulators.

[0002]

2. Description of the Related Art FIG. 7 shows an external view of a bar code reader, in which a bar code 21 printed on a product 23 is scanned by a light beam 22 and the reflected light is built into the bar code reader 20. The barcode demodulator is used to read the information such as the product name and price of the product. FIG. 6 shows the configuration of a UPC bar code. The left guard bar (LGB) is at the left end and the center bar (C is at the center.
B), a right guard bar (LGB) is arranged at the right end, a character bar is arranged between them, and a left margin and a right margin are further arranged at both ends. Numerical values are represented by the width, the number, and the interval of the bars. In the bar code shown in the figure, the bar group on the left side of CB represents a 7-digit numerical value, and the bar group on the right side of CB represents a 6-digit numerical value. The bar code is demodulated by scanning the bar group with a light beam such as a laser beam in the left-right direction or the opposite direction to photoelectrically convert the reflected light, and the width, number, and pulse width of each pulse of the obtained rectangular wave signal. This is done by examining the intervals and converting them into numbers. On this occasion,
Since the order of the demodulated numbers differs depending on the scanning direction, when scanning from right to left, the obtained numbers are rearranged in the reverse order and output, and when scanning from left to right. The demodulation is performed so as to match the obtained numerical value sequence. The scanning direction can be determined based on the above-mentioned rectangular wave signal.

The bar code reader repeatedly scans the light beam, but the scanning locus of the light beam with respect to the bar group is not constant, and the bar code reader deviates from the horizontal line passing through the center of each bar and passes vertically or obliquely. Or part of it may be missing. The reason for performing such irregular scanning is to eliminate the necessity of accurately positioning the commodity when reading the barcode.

In order to obtain product information from a bar code, information on all the bar codes printed on the product is required. Scanning does not mean that the light beam scans all bar codes. Therefore, of the multiple scannings of the light beam, only when all the barcodes are scanned, the obtained demodulated data is validated, and the data obtained by other incomplete scanning is invalidated and discarded. Although conceivable, the number of unnecessary scans increases, which causes a problem such as a reduction in reading speed.

Therefore, the following method is used for a bar code consisting of a plurality of blocks. That is, as shown in FIG. 6, the bar group is divided into two blocks, a left block on the left side and a right block on the right side from CB,
When the light beam scans all the barcodes belonging to one block, the demodulated data of the barcodes belonging to the block is validated. In this way, after the demodulated data of the bar code belonging to one block is obtained, by further demodulating the blocks located before and after the block completely scanned by another light beam, Demodulation can be performed. When the light beam is irregularly scanned, the barcode belonging to one of the blocks may be scanned completely, but the other block may be scanned incompletely, rather than the case of scanning all the barcodes. Probability is generally higher. Therefore, according to this method, the amount of invalid data is reduced as compared with the method described above, and the data utilization efficiency is improved.

[0006]

However, even in the method described above, there is a problem in that the data of the block in which the scanning of the light beam is incomplete is invalid, so that the data read at all cannot be utilized.

Therefore, an object of the present invention is to utilize the data obtained by the incomplete scanning of the light beam to help improve the bar code reading accuracy.

[0008]

To solve the above-mentioned problems, a bar code demodulating device for scanning a bar code consisting of a single block or a plurality of blocks with a light beam and reading the reflected light to demodulate the bar code. 1, a bar width counter 1 for reading the bar width of the scanned bar code, a recognition unit 2 for recognizing the scanning range and scanning direction of the light beam based on the read data of the bar width counter 1, and the bar width counter 1 The demodulation unit 3 for demodulating the read data of is provided, the recognition unit 2 determines whether or not each block is completely scanned by the light beam, and based on the result, the read data of the completely scanned block is read. A bar code demodulating device characterized by demodulating and subsequently demodulating read data of incompletely scanned blocks located before and after the block; or And a second storage unit 5 for storing demodulation data of a block completely scanned by the light beam, and a second storage unit 5 for storing demodulation data of a block imperfectly scanned by the light beam. The comparison unit 6 for comparing the demodulation data of the first storage unit 4 and the demodulation data of the demodulation data of the second storage unit 5 corresponding to the demodulation data of the first storage unit 4 is provided, and the comparison unit 6 is provided. The demodulated data of the block stored in the first storage unit 4 is output based on the result of the unit 6, and then the demodulated data of the blocks located before and after the block is output from the first storage unit 4. This is achieved by a bar code demodulating device characterized in that

[0009]

1 is a diagram for explaining the principle of the present invention. 1 is a bar width counter, 2 is a recognition section, 3 is a demodulation section, 4 is a first storage section, 5 is a second storage section, and 6 is a comparison. It is a department.

In the present invention, the bar width of the bar code scanned by the light beam is detected by the bar width counter 1, while the recognition range of the scanning range and the scanning direction of the light beam is detected by the recognition unit 2 based on the read data of the bar width counter 1. recognize. Then, it is determined whether or not each block is completely scanned by the light beam based on the result of the recognition unit 2. And
The read data of a completely scanned block is demodulated, and subsequently the read data of an incompletely scanned block located before and after the block is demodulated. As described above, by demodulating the read data of the incompletely scanned block, this demodulated data can be used for the purpose of collating the demodulated data of the completely scanned block, etc. It is possible to effectively use the collected data.

Further, based on the result of the recognition section 2, the demodulation data of the block completely scanned by the light beam is transferred from the demodulation section 3 to the first storage section 4, and the demodulation data of the incompletely scanned block is transferred. Are transferred from the demodulation unit 3 to the second storage unit 5. At this time, the demodulated data stored in the first storage unit 4 is output to the outside as valid demodulated data in the conventional method, and the demodulated data stored in the second storage unit 5 is In the conventional method, the data is discarded as invalid data. Then, after the demodulated data obtained each time the light beam is scanned is stored in the first storage unit 4 and the second storage unit 5 according to the above-mentioned criteria, the demodulation data of the first storage unit 4 is demodulated in the comparison unit 6. The data and the first storage unit 4 of the demodulated data in the second storage unit 5
If the demodulation data of the first storage unit 4 is output when the demodulation data of the first storage unit 4 is compared with the corresponding demodulation data and the demodulation data of the first storage unit 4 is output when the two match. Get higher. That is, the reliability of the data demodulated and output to the outside can be improved by using the invalid data without using it.

[0012]

FIG. 2 is a block diagram showing the configuration of the recognition unit 2 shown in FIG. 1, FIGS. 3 and 4 are diagrams showing scanning paths of a light beam on a bar code, and FIG. 5 is shown in FIG. It is a figure which shows the content of the 1st storage part 4 and the 2nd storage part 5 which were shown. Below, Figure 1
-Example of this invention is described with reference to FIG.

When the light beam scans the bar code shown in FIG. 6, the bar width counter 1 detects a pulse corresponding to the width, number and interval of the bar code. The bar width data detected by the bar width counter 1 is sent to the demodulation unit 3 and demodulated into numerical values.

The output of the bar width counter 1 is the recognition unit 2
Entered in. As shown in FIG. 2, the start guard bar (SGB) first scanned by the light beam is SGB.
When detected by the detector 11, its output is the shift register 14
And is sequentially shifted to the right by a shift clock synchronized with the input of data. SGB is either LGB or RGB depending on the scanning direction of the light beam. Next, when the CB detector 12 detects CB, its output is input to the shift register 15 and sequentially shifted to the right by the shift clock. Finally, when the end guard bar (EGB) is detected by the EGB detection unit 13, the output thereof and the logical product of the shift registers 14 and 15 are ANDed.
Taken by gate 16. If the shift register 14 has 13 digits and the shift register 15 has 7 digits, the light beam scans all the bar codes to SGB, CB, EG.
Output S of AND gate 16 only when all B are detected
1 will be obtained. That is, it is possible to judge by S1 whether or not the light beam has scanned all the bar codes. Further, since the input terminal of the AND gate 17 is connected to the seventh digit from the right of the shift register 14 and the output of the CB detection unit 12, when S2 is output from the AND gate 17, the scanning direction of the light beam is It can be seen that when is from left to right, at least all the bar codes belonging to the left block are scanned, and when the scanning direction is from right to left, at least all bar codes belonging to the right block are scanned.
Similarly, the output S3 of the AND gate 18 scans all bar codes belonging to at least the right block when the scanning direction is from left to right, and at least the left block when the scanning direction is from right to left. It can be seen that all the belonging barcodes have been scanned.

The signals S1, S2, S3 described above and the signal indicating the scanning direction described in the section of the prior art are output from the recognition section 2 to the demodulation section 3. The demodulation unit 3 distributes the demodulated data to either the first storage unit 4 or the second storage unit 5 based on the above-mentioned signal sent from the recognition unit 2 and stores the demodulated data.

When all the bar codes are scanned, for example, when the scanning locus on the bar code is a, the recognition unit 2 outputs S1 = "1". When a part of the bar code is scanned, for example, when the scanning loci on the bar code are b, c and d, S1 = "0". Therefore, when S1 = "1", the demodulated data is transferred from the demodulation unit 3 to the first storage unit 4, and when S1 = "0", the demodulated data is transferred from the demodulation unit 3 to the second storage unit 5. To do. At this time, the demodulated data is rearranged as needed based on the signal indicating the scanning direction of the light beam sent from the recognition unit 2 and stored in the first storage unit 4 and the second storage unit 5.

Next, in the comparison unit 6, the first storage unit 4
Demodulation data and the demodulation data of the first storage unit 4 among the demodulation data of the second storage unit 5 are compared, and if they match, it means that the barcode is normally read. The demodulated data is output from the first storage unit 4 after making a determination.

As described above, by using the demodulated data obtained by the imperfect scanning, the reading accuracy of the demodulated data obtained by the perfect scanning can be improved. Next, an embodiment of the present invention in the case where the barcode is divided into two blocks as shown in FIG. 6 will be described. As shown in FIG. 3, the scanning trace on the barcode is b
In this case, since the bar group A belonging to the left block is all scanned and a part B'of the bar group belonging to the right block is scanned, S2 is output from the recognition unit 2 and S1 and S3 are not output. .. Therefore, S1 = "0", S2 = "1",
When S3 = “0”, as shown in FIG. 5, the demodulated data of the bar group A is transferred from the demodulation unit 3 to the first storage unit 4, and the demodulated data of the bar group B ′ is transferred from the demodulation unit 3 to the second storage unit 4. To the storage section 5 of.

When the scanning locus is c, a part A'of the bar group belonging to the left block is scanned and all bar groups B belonging to the right block are scanned, so that the recognition section 2 outputs S3. S1 and S2 are not output. Therefore, S1 =
When “0”, S2 = “0”, and S3 = “1”, as shown in FIG.
Of the bar group A ′ to the demodulation unit 3
To the second storage unit 5.

When any block is imperfectly scanned as in the scanning locus d, the demodulated data of C'and D'will be moved to the second storage unit 7, and at this time, If the lengths of the corresponding A'and C'and the corresponding B'and D'are compared and the shorter one is erased, the accuracy of the demodulated data output from the first storage unit 4 is further enhanced. be able to.

The recognition unit 2 determines the scanning direction of the light beam based on the signal sent from the bar width counter 1, and the demodulation unit 3 rearranges the demodulated data according to the scanning direction and stores the first data. The data is stored in the unit 4 and the second storage unit 5.

Then, in the comparison unit 6, the first storage unit 4
Of the demodulation data of the second storage unit 5 and the demodulation data of the first storage unit 4 corresponding to the demodulation data of the second storage unit 5 are compared. In the example shown in FIG. 3, the demodulated data of A and the demodulated data of A ′ are compared with each other, and if they match, the demodulated data of A is output from the first storage unit 4. Then, the demodulated data of B belonging to the end of A and the demodulated data of B'are compared with each other, and if they match, the demodulated data of B is output from the first storage unit 4. Of A and B,
Regarding which belongs to the previous block and which belongs to the latter block, it is determined that the block in which LGB and CB are detected is the previous block, and the block in which CB and RGB are detected is the subsequent block.

As described above, according to the conventional method, only the completely scanned demodulated data of A and B are output, and the demodulated data of A'and B'or C'and D'are invalid data. However, in the present invention, such demodulated data is also used to correct the misreading of A and B, respectively. Therefore, the read result of the demodulated data of A and B output from the first storage unit 4 is more accurate than the conventional one.

The present invention can be applied to a bar code having an arbitrary number of digits by changing the number of bits of the shift registers 14 and 15 in this embodiment. It is also possible to divide the bar group into two or more arbitrary blocks and perform the same processing as in this embodiment on each block.

[0025]

As described above, according to the present invention, it is useful to improve the reliability of barcode reading by utilizing incomplete data which has not been used conventionally.

[Brief description of drawings]

FIG. 1 is a block diagram showing the principle of the present invention,

FIG. 2 is a block diagram showing a configuration of a recognition unit,

FIG. 3 is a diagram showing a scanning trace on a barcode (No. 1),

FIG. 4 is a diagram showing a scanning trace on a barcode (2),

FIG. 5 is a diagram showing the contents of a first storage unit and a second storage unit,

FIG. 6 is a diagram showing the configuration of a barcode,

FIG. 7 is a diagram showing an appearance of a barcode reader,

[Explanation of symbols]

1 bar width counter, 11 SGB (start guard bar) detector, 2 recognizer, 12
CB (center bar) detector, 3 demodulator,
13 EGB (end guard bar) detector, 4 first storage, 14 and 15 shift register, 5
Second storage, 16, 17, 18 AND gates,
6 comparison section, 20 bar code reader,
21 barcodes, 22 light beams, 23 products,

Claims (2)

[Claims] 1. A bar code demodulating device for scanning a bar code composed of a single block or a plurality of blocks with a light beam and reading the reflected light to demodulate the bar code. Reading bar width counter (1), a recognition unit (2) for recognizing the scanning range and scanning direction of the light beam based on the read data of the bar width counter (1), and a reading of the bar width counter (1) Demodulator for demodulating data
(3) is provided, the recognition unit (2) determines whether or not each block is completely scanned by the light beam, and based on the result, demodulates the read data of the completely scanned block, and And a bar code demodulating device for demodulating read data of incompletely scanned blocks located before and after the block. 2. A first storage section (4) for storing demodulation data of a block completely scanned by a light beam, and a second storage section (4) for storing demodulation data of a block imperfectly scanned by a light beam. Part (5), demodulated data of the first storage part (4), and the second storage part
A comparison unit (6) for comparing the demodulation data of the first storage unit (4) and the corresponding demodulation data of the demodulation data of (5) is provided, and based on the result of the comparison unit (6), the first comparison unit The demodulated data of the block stored in the storage section (4) of the first block is output, and then the demodulated data of blocks located before and after the block are output from the first storage section (4). Term
(1) The bar code demodulator described.