JP2500859B2 - Bar code reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is a bar for encoding a predetermined symbol, alternately arranging line segments having different optical reflectances, and reading a bar code recorded in a combination of widths of the line segments. The present invention relates to a code reader.

[Conventional technology]

Conventionally, a line segment having different light reflectance, for example, a black line and a white line are alternately arranged, the width of each black line and a white line is changed, and the combination of them forms a bar code in which an encoded symbol is recorded. Is generally known.

Then, this bar code is converted into an electric signal corresponding to the reflectance and width of each bar of the bar code by a scanning sensor such as an electronic scanning type, a manual scanning type, or a laser scanning type, and the electric signal is processed. By doing so, a bar code reading device for reading the code recorded in the bar code is also generally known.

As an example of such a thing, the bar code system generally called NW-7 is described. As a special example of NW-7, there is a separate type that allows a blank of an arbitrary length between characters after the start code as shown in FIG. 4 (a). This is so that the data code after the start code can be arbitrarily replaced by attaching a sticker on which a new data code is printed. Seal 4b as shown by the broken line in Fig. 4 (a)
If the reflectance of the sticker 4b is lower than the reflectance of the surface pasted with the sticker, the output waveform of the reading sensor,
Further, the binarized waveforms are as shown in FIGS. 4 (b) and 4 (c), respectively.

As shown in FIGS. 4 (a), (b), and (c), a binarized waveform is obtained in which the first thin black bar on the seal starts at the label boundary or in the middle.

In other words, what should be originally detected as a thin black bar is detected as a thick black bar.

Now, in the conventional bar code reader, the threshold value for distinguishing between the thick bar and the thin bar is the data of the number of one character representing the width of each bar obtained from the binarized waveform. And the threshold value is determined based on a predetermined ratio. Here, in FIG.
As shown in (b) and (c), when one bar is detected as an abnormally thick bar, the above-described threshold value does not reach the originally set value and should be recognized as a thick bar originally. Sometimes the bar is recognized as a thin bar.

For NW-7, the encoding of special characters and numbers is predetermined. If the bar at the beginning of the bar code representing a number becomes abnormally thick for the above-mentioned reason, only the black bar at the beginning is judged to be a thick bar by the conventional width recognition threshold value, and the original bar after that is detected. The thick bar is judged as a thin bar. When the width of each bar is decoded with this threshold value, a code corresponding to a number different from the original number will be obtained.

For example, in the case of FIGS. 4 (a), (b), and (c), originally, the leading bar is a thin bar, "0000011", and the number "0".
However, if the top bar becomes an abnormally thick bar, it will be decoded as "1000010" and will correspond to the number "5".

Such an example occurs not only in NW-7 but also in other bar code systems.

[Problems to be solved by the invention]

In the above-mentioned conventional technique, the bar code system called NW-7 and the separate type has been described. However, it is not limited to NW-7 that a label is affixed or the label becomes dirty, and it becomes an electric signal as a bar thicker than the original bar width, resulting in a reading failure.
For example, 2of5, 3of9, and JAN can happen.

That is, in the normal bar code system, the start code and the stop code are defined, and if they are not recognized, it is determined that the reading is defective. However, as described in the related art, as the usage of the barcode is diversified, such as the separate type or the label replacement, the reading failure may occur.

As described in the above-mentioned conventional technique, the recognition of a number different from the number originally recorded significantly deteriorates the reliability of the bar code reading device, and the bar code reading device allows data input. It also reduces the reliability of the system in place.

The present invention has been made in view of the problems caused by such poor reading.
Focusing on the cause that it is originally detected to be thicker than the bar width, we provide a bar code reading position that can detect the reading failure that occurs due to this cause with sufficient certainty, and check the reading result of the bar code reading device. It aims to improve reliability.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention, as shown in the configuration in FIG. 1, includes a bar code composed of a plurality of bars and a plurality of spaces formed between the bars, Photoelectric conversion means for converting into an electric signal according to the width of each bar and the width of each space, according to the width of each bar converted into the electric signal and the width of each space, the bar code In a bar code reading device including a reading means for decoding, the width of the bar having the minimum width indicated by the electric signal is obtained, and a calculation is performed with a value slightly larger than this width as a first threshold value. Calculating means for calculating a second threshold value from the width of the space indicated by, and comparing with the first threshold value to detect the number of the bars having a width equal to or smaller than the first threshold value. A first detecting means; Second detection means for detecting the number of the spaces having a width equal to or larger than the second threshold, and detected by the first detection means and the second detection means. It is determined whether or not each of the above-mentioned numbers matches the number of reference lines set based on the specific standard of the barcode,
The technical means is provided which comprises: a determining means for causing the reading means to decode the bar code when both of the respective numbers match the reference number, and for outputting a reading failure signal when the bar code is negative.

[Action]

First, the bar code is based on a predetermined system, the number of the bar, the ratio of the width of the bar, the encoding of the symbol,
The type of bar corresponding to the code and the number of types of width are determined. For example, as well-known ones, 2of5, NW-7 (2of7), code39 (3of9), JAN (PO
There is something called S), etc., and each has a different system.

The structure of the present invention is shown in FIG. 1 and its operation will be described.

The present invention, before the decoding by the reading means, for example, as described in the prior art, in order to reduce the reading failure due to the detection of noise as a bar thicker than the original bar width, the electric power from the photoelectric conversion means is reduced. Of the signal, the first threshold value is calculated from only the bar having the minimum width not including the noise, and further compared with the first threshold value to determine the width equal to or smaller than the first threshold value. The number of bars that it has is detected, and it is determined whether or not this number matches the number set based on a specific bar code standard. As a result, if even one bar is detected thicker than the original width, it is determined that it is noise that causes reading failure and is not decoded, so the reading accuracy is reliably improved.

On the other hand, regarding the space formed between the bars, the second threshold value is calculated from the electric signal of the space, and the second threshold value is compared with this second threshold value. The number of lines having a width equal to or larger than the value is detected, and it is determined whether or not this matches the number set based on a specific standard to determine whether or not decoding is possible. Therefore, the reading accuracy is further improved.

〔effect〕

As described above, according to the present invention, even if the electric signal from the photoelectric conversion unit includes an original bar, a bar different from the width of the space, or an electric signal indicating the space by mistake, the reading performance is improved. It has an excellent effect that it can be improved.

〔Example〕

 An embodiment to which the present invention is applied will be described below.

This embodiment is a bar code reading device for reading a bar code system bar code called NW-7 (2of7), and has an arbitrary length between character codes between a start code and a stop code. It also reads the separate type that allows the blank part of.

In the bar code system called NW-7, in addition to the numbers 0 to 9, characters that are start and stop codes and some special characters are treated as characters. One character is encoded into a 7-bit binary code and odd-numbered bit
A space (S) is assigned to an even bit of a bar (B), and "0" is recorded thinly (N) and "1" is recorded thickly (W). This thick and thin ratio is about 1: 2.5.

Numeric characters are coded with 2 bits out of 7 bits as "1". One thick bar (WB), three thin bars (NB), one thick space (WS), and two thin spaces (NS). Recorded in a book.

And a narrow space (NS) between each character
Alternatively, a thick space (WS) character gap is provided.

In the following description, the bar and the space that make up the bar code, and the thinness and the thickness of each, will be described by the symbols in the above parentheses.

In this embodiment, the bar that constitutes the bar code is both B and S described above.

 Hereinafter, the configuration of the embodiment will be described with reference to the drawings.

FIG. 2 is a configuration diagram showing the configuration of the sensor unit of the handheld bar code reader and the flow of signal processing.

Reference numeral 1 denotes a sensor unit, which has a configuration described below. Two
Is an illumination light source consisting of 10 high-intensity red light emitting diodes used for the light source. A light scattering material 3 scatters the illumination light from the red light emitting diode 2 to make it uniform over a predetermined range. Reference numeral 4 is a recording medium label, on which a bar code 5 of optical information is printed.

A plane reflecting mirror 6 reflects the light reflected from the barcode label 4 and changes its direction. A lens 7 collects the reflected light from the bar code label 4 and passes the diaphragm member 8 to form a bar code image at a predetermined position. Reference numeral 9 denotes a silicon-based image sensor as a reading sensor, which has a one-dimensional resolution of 2048 bits in which a large number of photo elements are arranged linearly, and has a spectral sensitivity peak region near the emission spectrum of the illumination light source 2. It has. Reference numeral 10 denotes a handheld case, which is connected to the signal processing unit 11 via a signal cable for exchanging various electric signals between the inside and the outside. The signal processing unit 11 includes a binarization circuit 12 and a microcomputer 13, and outputs the output waveform a of the image sensor 9 to 2
The binarizing circuit 12 shapes the binarized output b, and the microcomputer 13 performs predetermined processing, read failure determination, and the like.
Output as a digital signal c.

In this embodiment, the microcomputer 13 converts the character read from the bar code into an ASCII code and outputs it as a digital signal C.

FIG. 3 shows the configuration of the binarization circuit 12. Reference numeral 12a denotes a delay attenuator that slightly delays and attenuates the output from the image sensor 9, and 12b compares the output of the delay attenuator 12a with the output of the image sensor 9 and finds that they intersect. It is a comparator that inverts the output.

FIG. 4A shows an example of a separate type NW-7 barcode. It shows a case where a sticker 4b having a bar code 5b printed thereon is attached onto a label 4a having a bar code 5a printed in advance.

The reflectance of the white background of the sticker 4b is slightly lower than that of the label 4a due to the difference in paper quality. It is assumed that the reading line of the image sensor 9 is placed on the bar code as indicated by L.

The output waveform (solid line) of the image sensor 9 from L ₁ to L ₂ on this read line and the output (broken line) of the delay attenuating circuit 12a are shown in the same figure (b), and the output of the binarization circuit 12 is shown in the same figure ( c)).

From these FIG. 4 (a), (b), (c), the label
It can be seen that the output waveform of the image sensor 9 drops at the boundary between 4a and the seal 4b, and the binarized output has risen from point A. Therefore, the original NB should be detected as B
At that point, the binarized output is already at the black level,
It can be seen that NB is detected as an abnormally thick B.

 Next, the operation of this embodiment will be described with reference to the drawings.

FIG. 5 shows a flowchart of the bar code reading operation by the microcomputer 13.

First, in step 110, the widths of B and S are stored as data in the memory incorporated in the microcomputer 13 from the binarized output obtained from one reading operation of the image sensor 9.

In step 120, a left margin that is S equal to or larger than a predetermined value is detected.

In step 130, a start code is detected from B following S of the left margin. This start code is predetermined, and in the case of FIG. 4 (a), the character "a" is used. When the left margin and the start code are detected in step 120 and step 130, it is understood that the data character is recorded following S which is the next character gap.

In step 140, this data character is decoded into a data code.

 This operation will be described in more detail later.

In step 150, a stop code is detected and it is confirmed that the data code is completed.

In step 160, a write margin of S having a length equal to or longer than a predetermined value is detected.

In step 170, the character corresponding to the data code decoded in step 140 is converted into an ASCII code and output.

This completes a series of bar code reading operations and notifies the operator of the end of reading. When the processes of steps 110 to 170 are completed, the reading operation of the image sensor 9 is commanded again, and the processes of steps 110 to 170 are repeated.

Table 1 shows the storage state in the memory when the bar code shown in FIG. 4 (a) is read.

Table 1 shows that each data has different optical reflectance, that is, 2
It is shown that the levels of digitized outputs are alternately arranged and arranged every 7 bits. By the operation of step 120 of the microcomputer 13, S having a predetermined value or more is arranged as a left margin.

FIG. 6 shows a more detailed flowchart of step 140 shown in FIG.

In step 141, one character, that is, NW-
In 7, the data for 7 lines including B and S are read from the memory.

In step 142, the number of B and S is checked. This step is an essential part of the present invention and will be described later.

In step 143, thresholds TB and TS for identifying NB and WB and NS and WS are calculated from the following equations (1) and (2).

In step 144, N and W are identified based on the threshold value obtained in step 143 and converted into a binary code.
Then, in accordance with the bar code system of NW-7, it is associated with a character and converted into an ASCII code. This ASCII code is stored in the memory and output as a data code in step 170.

If the decoded binary code is the stop code in step 144, the process branches to YES in step 145, and proceeds to step 150. If it is not a stop code,
The operations from step 141 to step 145 are repeated.

TB = (B1 + B2 + B3 + B4) / 3 (1) TS = {(S1, S2, S3) max + (S1, S2, S3) min} / 2 (2) In addition, 1 in the equations (1) and (2) 3,1 / 2 coefficient is NW
The ratio of N to W of -7 is approximately 1: 2.5, and it was derived in consideration of the fact that the numerical characters are bar coded from 3 NB, 1 WB, 2 NS, and 1 WS. It is a value.

Taking the third row of bar data in Table 1 as an example, TB = (38 + 6 + 5 + 13) /3≈20.6 ... (1 ') TS = (13 + 3) / 2≈8 ... (2') If the larger value is “1” and the smaller value is “0”, the binary code becomes “1000010”.
In the case of -7, the numerical character is "5".

However, the bar code in this portion originally represents the numeric character "0", and "0" is read as "5" due to incorrect binarization as shown in FIG. That is, the NB is recognized as the WB and the WB is recognized as the NB only by the processes of step 143 and step 144.

Therefore, in this embodiment, the steps that are the main part of the present invention are performed.
Added 142 processes. FIG. 7 shows a more detailed flowchart of step 142.

In step 142-1, the threshold values T1 and T2 are calculated by the following equations (3) and (4).

T1 = (B1, B2, B3, B4) min × 1.6 + 2 (3) The constant of +2 is a correction that B is detected to be slightly thin.

In step 142-2, the number of Bs equal to or less than T1 is detected based on the threshold value T1 and set as C1. Equation (3) and step
142-2, the number of NBs among the Bs forming the character is detected from the B having the smallest width. In other words, one character has two or more
NB is included, and it is assumed that one of them is correctly detected.

In step 142-3, the number of S equal to or greater than the threshold value T2 is detected and set as C2. By the equation (4) and step 142-3, the number of WS's among the S's constituting the character is detected from the thickest S.

At step 142-4, the numerical character of NW-7 is NB.
Since there are three, it is determined whether or not C1 is equal to 3, and if equal, to step 142-5, and if not, to step 142.
Go to -6.

At step 142-5, the numerical character of NW-7 is W
Since there is only one S, determine whether C2 is equal to 1,
If they are equal to each other, step 143 is performed. If not, step 142-
Go to 6.

In step 142-6, a read failure countermeasure process is performed. In this embodiment, all the bar data input in step 110 are canceled, the reading operation is instructed to the image sensor 9 again, and the operation from step 110 is restarted.

According to the flow chart shown in FIG.
As shown in the figure, it can be detected that the binarization is incorrect.

That is, in the case of the example of FIG. 4, the threshold value T1 of the equation (3) is
Becomes the following equation (3 ′), T1 = (38,6,5,13) min × 1.6 = 8 (3 ′) C1 = 2 by the process of step 142-2, so step 142-4 The process branches to step 142-6 and the read failure countermeasure process is performed.

The check of the number of S in Steps 142-3 and 142-5 in the equation (4) is effective when the barcode printed on the label 4a appears in the output of the image sensor 9 through the sticker 4b.

With the configuration and operation described above, the present embodiment reads the bar code correctly.

In the embodiment described above, only the problem due to the optical reflectance of the seal 4b attached to the label 4a was described,
If the sticker 4b is thin, the bar code printed on the label 4a is transparent, which may cause problems as described in the above-mentioned embodiment. However, in this embodiment, the reading failure can be detected in this case as well.

Further, as the read failure countermeasure processing shown in step 142-6 in the above-described embodiment, various kinds can be considered. For example, as described in the present embodiment, if only the head NB being thickly detected is a problem, this step 142
In -6, a process may be performed in which the leading B is regarded as an NB, and the decoding is performed in steps 143 and 144. By doing so, since the reading failure can be corrected, it is not necessary to restart the reading operation of the image sensor 9 again.
The efficiency of reading work is improved. Furthermore, by checking the number of bars for all types of bars, it is possible to specify which type of bar was erroneously detected.

Further, in the above-described embodiment, the read failure determination according to the present invention is described only for the data code when the separate type barcode is read. However, if the start code to the stop code are printed on the sticker, the top bar may be similarly detected to be thicker. In this case, since the start code is predetermined, if the decoding result does not match the start code, read failure countermeasure processing is performed. However, if the decoding result coincides with the start code and stop code of the bar code system, it may happen.
Therefore, the number of start codes and stop codes may be checked, and the reading error may be corrected based on the result.

Further, in the above-described embodiment, the number of characters is checked for each character in order to read a curved bar code or a bar code having a different size for each character. However, the number of lines may be checked collectively for the whole from the start code to the stop code.

Also, in the above embodiment, the threshold for decoding
TB and TS and thresholds T1 and T2 for checking the number of lines were calculated. However, thresholds T1 and T2 for checking the number may be used as the thresholds TB and TS.

Further, in the above-described embodiment, two types (N, 7) called NW-7 are used.
W) width bar code system was explained. However, the bar code system called JAN (POS) has four widths. In this case, the present invention may be applied to calculate the threshold value based on B having the smallest width.

Further, in the above-described embodiment, the black B is printed on the white background, but the white B may be printed on the black background.

In the embodiment as described above, it is possible to detect a reading failure caused by being detected thicker than the original bar, and since the data of this reading failure is not output, the reliability of the reading result of the bar code reading device can be improved. Can be improved. Further, it is possible to improve the reliability of a system for inputting data from the bar code reader, for example, an inventory management system or a sales management system, and it is possible to remarkably reduce the burden on an operator who operates them. Further, in this embodiment, not only B but also S is checked for the number of lines, so that the reliability is further improved.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of the present invention, FIG. 2 is a configuration diagram of a bar code reading apparatus according to one embodiment, FIG. 3 is a configuration diagram of a binarization circuit according to one embodiment, and FIG. ) Is a plan view showing an example of a bar code, FIG. 4 (b) is an output waveform diagram of the image sensor, FIG. 4 (c) is an output waveform diagram of the binarization circuit, and FIG.
FIG. 6, FIG. 7 and FIG. 7 are flowcharts showing the operation of the microcomputer. 1 ... Sensor, 2 ... Illumination light source, 3 ... Light scattering material, 4 ... Bar code label, 5 ... Bar code, 6 ... Flat reflector, 7 ...
… Lens, 8 …… Aperture member, 9 …… Image sensor, 10 ……
Handheld case, 11 …… Signal processing unit, 12 …… Binarization circuit, 13
…… Microcomputer.

Claims (1)

(57) [Claims] 1. A bar code composed of a plurality of bars and a plurality of spaces formed between the bars,
Photoelectric conversion means for converting into an electric signal according to the width of each bar and the width of each space, according to the width of each bar converted into the electric signal and the width of each space, the bar code In a bar code reading device including a reading means for decoding, the width of the bar having the minimum width indicated by the electric signal is obtained, and a calculation is performed with a value slightly larger than this width as a first threshold value. Calculating means for calculating a second threshold value from the width of the space indicated by, and comparing with the first threshold value to detect the number of the bars having a width equal to or smaller than the first threshold value. A first detecting means; a second detecting means for detecting the number of the spaces having a width equal to or larger than a second threshold by comparing with the second threshold; and the first detecting means. And the above-mentioned detected by the second detecting means It is determined whether or not the number of lines coincides with a standard number set based on a specific standard of the barcode, and when both of the respective numbers coincide with the standard number, the bar is read by the reading means. A bar code reading device, comprising: a determination unit that decodes a code and outputs a read failure signal when the code is denied.