JP2900561B2 - Barcode reading device and barcode reading method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a bar code reader, and aims to prevent erroneous reading due to noise without lowering a reading rate, and separates right and left guard bars and a center bar into right and left blocks. A scanning unit that repeatedly scans the obtained barcode label and converts the reflected light into an electric signal, a demodulation unit that demodulates a barcode for each of the left and right blocks based on the electric signal, and combines the demodulated data of the left and right blocks. And a check unit for checking the normality of reading. The demodulation unit adds an identification flag to the demodulated data of the block in which the center bar is detected after the guard bar is detected, and inputs the demodulated data to the check unit. When the demodulated data provided with the identification flag is input, the check unit checks if at least two or more identical demodulated data are obtained. The demodulated data block configured to synthesize the demodulated data of the other blocks.

[Industrial applications]

 The present invention relates to an improvement in a barcode reader.

White portions are provided as margins on the left and right sides of the barcode, and there is a risk of erroneous reading depending on the scanning direction if noise is applied to these portions.

In order to prevent this erroneous reading, in a reading device that scans a label a plurality of times, it is sufficient to match all data, but the reading rate is reduced.

Therefore, it is required to prevent erroneous reading due to noise without lowering the reading rate.

[Conventional technology]

FIG. 5 is a diagram for explaining the prior art, and FIG. 6 is a diagram showing an example of a bit shift due to noise.

As shown in FIG. 5, a bar code used in a POS terminal or the like is divided by a left guard bar LGB, a center bar CB, and a right guard bar RGB, and (LGB-CB), (CB
−RGB) can be read even when input in half blocks.

FIG. 5 shows a configuration example of a stationary bar code reader using a laser beam. The scanning unit 1 repeatedly scans a bar code label 15 with a laser beam,
The reflected beam is received and photoelectrically converted, the AD conversion circuit 2 binarizes the converted signal, and the demodulation unit 11a demodulates the signal for each block.

The demodulated data 20 of the left and right blocks is transmitted to the check unit 10a.
The normality of the data is checked based on a check digit or the like provided in the barcode. If the data is normal, the operator is notified and the respective demodulated data 20 is output to the main unit.

In order to prevent erroneous reading, the left and right blocks are scanned at least twice each, and the demodulated data matches, and when the other checks are OK, the reading is OK twice, or one of the two methods. If the block is scanned two or more times and the demodulated data matches, the reading is OK even if the other block is scanned once.
A times matching method or the like is used.

[Problems to be solved by the invention]

As shown in FIG. 5, the barcode label 15 is provided with left and right white portions as margins.

However, if the white portion is long, paper noise is likely to be widened due to irregularities on the paper surface, etc., and depending on the scanning direction, a bit shift of a bar code may occur and cause erroneous reading.

FIG. 6 shows an example of the bit shift. FIG. 5 (II) shows the scanning in the direction of FIG. 5A, that is, from LGB to CB.
2 shows an example of binary data output from the AD conversion circuit 2 when the noise 30 is spread in the margin portion immediately before the data. According to this, the normal value ODD shown in (I) [303
0] is bit-shifted and is erroneously read as [6464] of ODD as shown in (II).

This bit shift is from the white part (LGB or RGB) to CB
This is likely to occur when scanning is performed in the direction, that is, in the direction A or C in FIG. 5, and does not occur when scanning is performed in the direction B or D.

This is due to the characteristics of the AD conversion circuit 2, and for a reason such that if the white portion is long, the slice level for removing noise decreases.

In order to prevent erroneous reading due to this noise, the above-described two-time matching method may be adopted. However, since the left and right blocks need to be scanned at least twice, the reading rate decreases.

The present invention has been made in view of the above circumstances, and has as its object to provide a barcode reading device that prevents erroneous reading due to noise without lowering a reading rate.

[Means for solving the problem]

FIG. 1 In the principle diagram of the present invention, reference numeral 1 denotes a scanning unit which repeatedly scans a bar code label 15 divided into left and right blocks by left and right guard bars and a center bar, and converts reflected light into an electric signal.

A demodulation unit 11 demodulates a barcode for each of the left and right blocks based on the electric signal, and attaches an identification flag 21 to demodulated data 20 obtained by scanning from the left guard bar to the center bar or from the right guard bar to the center bar. Input to the check section 10.

Reference numeral 10 denotes a check unit, which combines the demodulated data 20 of the left and right blocks to check the normality of the read, and an identification flag.
The demodulated data 20 having 21 is input at least twice, and when they match, it is regarded as the demodulated data 20 of the block.

(Operation)

When the demodulation unit 11 detects the right or left guard bar LGB, RGB from a series of electric signals that are repeatedly scanned and input by the barcode label 15 and starts demodulation, the demodulation data 20 includes an identification flag. 21 is given and passed to the check unit 10.

When the demodulation data 20 to which the identification flag 21 is added is input, the check unit 10 checks the demodulation data 20 as demodulation data 20 of one block when the demodulation data 20 is input at least twice and when they match.

Thus, when the guard bar LGB, RGB is scanned from the center bar CB to the center bar CB, it is necessary to scan twice, but when the other block is scanned from the center bar CB in the direction of LGB or RGB, only one scan is required.

As described above, since the data is matched twice only in the scanning direction where noise is likely to be spread, the reading rate is improved compared to the conventional method in which both blocks are matched twice, and erroneous reading is prevented to the same extent. Can be.

〔Example〕

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

FIG. 2 is a block diagram of one embodiment, FIG. 3 is a flowchart of a demodulation operation, and FIG. 4 is a flowchart of a check operation.

Reference numeral 1 denotes a scanning unit that repeatedly scans light and converts reflected light from the bar code label 15 into an electric signal.

Reference numeral 2 denotes an AD conversion circuit that binarizes the converted electric signal.

11 is a demodulation unit, which first performs LGB or RGB
Is detected, an identification flag 21 is added to the demodulated data 20 and stored in the memory 9 together with the other demodulated data 20.

Reference numeral 9 denotes a memory in which a series of demodulated data 20 is stored and passed to the check unit 10.

Reference numeral 10 denotes a check unit for verifying the normality of reading by using check digits or the like. When the demodulated data 20 to which the identification flag 21 is added is input, the input is not performed twice,
If they do not match even after being input twice, the reading is not accepted and the input is waited.

In the demodulation unit 11, reference numeral 3 denotes a bar width detection circuit which detects the black and white bar width of the binarized signal and encodes it.

Reference numeral 4 denotes a filter circuit which detects the left and right guard bars LGB, RGB, and the center bar CB, instructs the demodulation circuit 5 to start / stop demodulation, and outputs LGB or RGB following white data of a predetermined width (corresponding to a margin). When input, "1" is set to a predetermined bit of buffer 7 (identification flag 21 is turned on)
I do.

Reference numeral 5 denotes a demodulation circuit which converts the input bar width code into a numerical code while referring to a conversion table 6 and sets a numerical code for each O / E in a buffer 7.

Reference numeral 7 denotes a buffer, the contents of which are transferred to the memory 9 by the writing circuit 8 every time one digit is demodulated.

In this example, the demodulated data 20 for each block is composed of 4 bytes when the block is composed of 4 digits.
1 has been granted.

In the above configuration, demodulation and check operations are performed as follows.

(1) The filter circuit 4 checks the data output from the bar width detection circuit 3, and when detecting LGB, RGB, and CB following white data having a predetermined width or more, instructs the demodulation circuit 5 to start demodulation. .

At this time, if it is LGB, RGB, the identification flag 21 of the buffer 7
Turn on.

(2) The demodulation circuit 5 demodulates the first digit and sets the O / E-specific and numerical data in the buffer 7.

(3) When one-digit demodulation is completed, the writing circuit 8 transfers the contents of the buffer 7 to the memory 9.

End the above demodulation operation for half a block, that is, CB or LGB
Until (RGB) is detected.

In this manner, the demodulation operation is performed while the barcode label 15 is being scanned, and the demodulated data 20 is sequentially stored in the memory 9.

(4) The check unit 10 starts a check process during the demodulation operation, searches the memory 9 and searches for two or more sets if there is the demodulated data 20 with the identification flag 21 turned on. .

Then, when it comes to two sets, the demodulated data 20 is compared,
If they do not match, wait for input, and if they match, check the normality by combining with the demodulated data 20 of the other block,
If normal, output normally.

As described above, from the guard bar LGB, RGB to the center bar CB
Only when scanning is performed twice, the matching method is performed twice, so that erroneous reading due to bit shift due to noise can be prevented without lowering the reading rate.

〔The invention's effect〕

As described above, according to the present invention, when scanning is performed from the right or left guard bar toward the center bar, scanning is performed twice, and when the demodulated data matches, the block is read OK. This has the effect of preventing erroneous reading due to noise caused by the margin portion without lowering the reading rate.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention, FIG. 2 is a configuration diagram of one embodiment,
FIG. 3 is a flowchart of a demodulation operation, FIG. 4 is a flowchart of a check operation, FIG.
The figure shows a bit shift example due to noise. In the figure, 1 is a scanning unit, 2 is an AD converter circuit, 3 is a bar width detection circuit, 4 is a filter circuit, 5 is a demodulation circuit, 6 is a conversion table, 7 is a buffer, 8 is a writing circuit, 9 is a memory, 10 Is a check unit, 11 is a demodulation unit, 15 is a barcode label, 20 is demodulated data, 21 is an identification flag, and 30 is noise.

Claims (3)

(57) [Claims] A scanning unit that repeatedly scans a bar code label divided into left and right blocks by left and right guard bars and a center bar, and converts reflected light into an electric signal;
A demodulator for demodulating a barcode for each of the left and right blocks based on the electric signal; and a check unit for synthesizing demodulated data of the left and right blocks to check the normality of reading. After the detection of the center bar, an identification flag is added to the demodulated data of the block in which the center bar is detected, and the demodulated data is input to the check unit. When the demodulated data having the identification flag is input, A barcode reading device that, when at least two or more identical demodulated data are obtained, combines the demodulated data of the block with the demodulated data of the other block. 2. The method according to claim 1, wherein if a match is obtained twice in the demodulated data to which the identification data is attached in one block, the match check is omitted twice in the demodulated data in the other block. 2. The barcode reader according to 1. 3. A bar code reading method for reading a bar code having a block separated by a guard bar and a center bar, wherein an identification flag is added to the read data in which the center bar is detected after the guard bar is detected. A bar code reading method, wherein, when given read data is input, reading is OK on condition that two or more identical read data are input.