JPH0786904B2 - Bar code demodulation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention relates to a bar code demodulation system for demodulating a bar code composed of a plurality of black and white bars having different numbers of modules. The bar code is converted into characters based on the number of modules obtained by using the corrected optimal basic module value, and if the number of modules is inappropriate and the above character conversion is impossible, one character By correcting the number of modules of each bar included based on the combination of the number of modules of the difference between each black and white bar, by performing the above character conversion, poor printing accuracy of the bar code itself, or Eliminating the effects of thick and thin black bars caused by changes in scanning speed when scanning with a barcode pen, it is possible to significantly improve the reading rate and significantly reduce the misreading rate. Than it is.

[Industrial application field]

The present invention relates to a bar code demodulation method used in a bar code reader, and particularly to a bar code demodulating bar code composed of a plurality of black and white bars having different numbers of modules such as UPC / EAN / JAN code. It relates to a code demodulation method.

For example, the black and white bar widths that make up the above UPC / EAN / JAN code are 1,2,3,4 of the basic module (single module).
Since there are four types, it is very difficult to accurately read and demodulate this with a manual barcode pen if there is an error in the bar width due to ink bleeding during barcode printing. The improvement of read rate and the reduction of erroneous read rate are major technical issues.

[Conventional technology]

In the conventional bar code demodulation method applied to the UPC / EAN / JAN code, as a means for eliminating the influence of the above error, after demodulating the bar group corresponding to a certain character, the bar group The total black bar width of and the standard value thereof are stored in a register, each black bar width of the next bar group is corrected based on the contents of the above register, and the next black bar width is corrected according to the corrected black bar width. A device for demodulating a group has been proposed (see Japanese Patent Application Laid-Open No. 57-191783).

[Problems to be solved by the invention]

Even with the above conventional bar code method, the fatness of the black bar,
It was not possible to sufficiently eliminate the influence of thinning, so that the reading rate was slightly inferior or the problem of erroneous reading occurred.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a bar code demodulation system capable of significantly improving the reading rate and significantly reducing the erroneous reading rate.

[Means for solving problems]

In the bar code demodulation method of the present invention, first the first demodulation is executed, and when this is impossible, the second demodulation is executed. That is, first, the number of modules (the number of the basic modules included in the bar) is calculated based on the basic module value (width of a basic single module) obtained from the previous bar for each of the black bar and the white bar. obtain. Then, the basic module value is corrected based on this module number and the bar width actually read to obtain a new basic module value, and the module number of the next bar is obtained based on this new basic module value. To In this way, the number of modules of each bar is sequentially obtained, and the bar code is converted into a character based on the number of modules.

The above is the first demodulation, and if the number of modules obtained as described above is inappropriate and the character conversion cannot be performed, the following second demodulation is executed.

First, for each of the black bar and the white bar that make up one character, the module number of the difference between the bars is obtained. Then, the number of modules of each bar is determined based on the combination of such difference module numbers, and the character conversion is performed based on these module numbers.

[Action]

In the first demodulation, for each of the black bar and the white bar, the sequentially corrected new basic module value obtained for each bar is the optimum basic module considering the thick and thin states of the black bar. It becomes a value. Therefore, the number of modules of each bar obtained based on such an optimum basic module value is very accurate, and demodulation is performed based on such an accurate number of modules, so that the reading rate is improved. , The misreading rate is reduced.

Further, in the second demodulation, since the number of modules of the difference between each bar is obtained for each of the black bar and the white bar in one character, the error of the fatness and the thinness of the bar is canceled and becomes zero. The difference in the number of modules is not affected by the thick or thin bar. Also, black that can be included in one character,
Since the combination of the number of modules of the white bar is fixed, if the combination of black and white of the number of modules of the above difference is determined, the number of each module of black and white bar is determined, and the number of modules of each bar should be known from this You can The number of modules of each bar obtained in this way is also the same as the number of modules of the above difference, without the influence of the thick and thin bars,
It will be very accurate.

As described above, according to the present invention, the read rate can be increased and the misread rate can be reduced by only the first demodulation. However, when the first demodulation cannot be performed, an inappropriate number of modules is corrected and the second demodulation is performed. By executing the above, it is possible to significantly improve the read rate and significantly reduce the misread rate.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an internal configuration of a bar code reader to which a bar code demodulating method according to an embodiment of the present invention is applied.

In the figure, the photoelectric conversion unit 1 is composed of, for example, a bar code pen or the like, and is means for scanning the bar code to obtain an optical signal and converting the optical signal into an electric signal. The analog-digital conversion unit 2 is a unit that converts the analog signal output from the photoelectric conversion unit 1 into a digital signal. This digital signal is a step-like signal of "1" and "0", respectively, having a length corresponding to the width of each black and white bar which constitutes the above bar code. The signal conversion unit 3 uses “1” in the digital signals of “1” and “0” corresponding to the black and white,
It is a means for producing a pulse signal at a change point of "0" and outputting a black and white signal corresponding to each. The time interval of the pulse signal obtained here corresponds to the width of the black and white bars.

The bar code converted into the pulse signal and the black and white signal in this way is demodulated via the data bus 4. This demodulation is performed by the timer counter unit 5 and the memory unit (RA
M) 6 and is controlled by the main control unit (CPU) 8 based on the microprogram in the memory unit (ROM) 7.
The line control unit 9 transmits the bar code read data to an external parent device, and the power supply unit 10 supplies power to each block.

The bar code demodulation method according to this embodiment will be specifically described below. In this embodiment, the first demodulation (Fig. 2) is first executed, and when this is impossible, the second demodulation (Fig. 3) is executed. Note that, here, a case will be described in which the bar codes (for example, UPC code) shown in FIG. 7 are sequentially input according to the scanning of the photoelectric conversion unit 1.

The first demodulation will be specifically described with reference to FIG. First, in step a ₁ , the width of the white and black bars W ₀ and B ₀ of the single module that constitutes the left guard bar at the beginning of the bar code (actually, it is converted into a time value by the timer count section 5). Are the basic module values WM ₀ and BM ₀ for white and black, respectively. And the number of modules of the first white bar W ₁ that makes up the next 1 character (for example, “9”)
m ₁ (an integer) is obtained based on the basic module value WM ₀ (step a ₂ ). Specifically, the width T _W1 of the white bar W ₁ is divided by the basic module value WM ₀ , and the integer value closest to the value (T _W1 / WM ₀ ) obtained by this is taken as the module number m ₁ . For example, if the value of T _W1 / WM ₀ is 2.5 or more and less than 3.5,
The number of modules m ₁ is judged to be 3. Then, the number of modules m ₁ thus obtained and the white bar W ₁ actually read
On the basis of the width T _{W1 of} the above, the basic module value WM ₀ of the above (one bar before) is corrected to obtain a new basic module value WM ₁ (step a ₃ ). Specifically, it is performed based on the following formula.

Next, the module number m ₂ (integer) of the next white bar W ₂ is obtained based on the basic module value WM ₁ obtained from the previous white bar W ₁ in the same manner as in step a ₂ above (step a ₄ ).
Subsequently in the same manner as in step a _3, based on the width Tw ₂ module number m ₂ and white bars W _2, and correction of the previous one bar basic module value WM ₁ of the new basic module value WM ₂ seek (step a _5).

When the number of modules m ₁ and m ₂ of the white bars W ₁ and W _{2 in} one character is obtained by the above processing, the black bars B ₁ and B ₂ are next.
Also for the above, based on the data on the black bar
By performing the same processing as a ₂ ~a _5, obtains the number of each module (step a _6).

In this way, the white bars W ₁ , W ₂ and the black bar B ₁ ,
When all the numbers of the respective modules of B ₂ are obtained, it is judged whether or not the numbers of these modules are appropriate, for example, whether or not the total number of the respective modules is a predetermined number of modules (for example, 7 modules) ( Step a ₇ ). A four-level bar code such as the UPC / EAN / JAN code consists of two black and white bars for each character, and each bar has 1 to 4 modules, making a total of 7 modules. Since it is configured, the determination as to whether the number of modules is appropriate is not limited to the above example, but various determinations can be made. When the number of modules is determined to be appropriate in step a _7, a code consisting of bars _{W 1, B 1, W 2} , B 2 is converted to a character in a known manner based on the number of the module, whereas, unsuitable If it is determined that, the second demodulation described below is executed.

1 demodulation of each character as described above, to the left of the data of the bar code (the left of the data than the center cord) is finished, sequentially repeated (Step a ₂ ~a _8). The center guard bar and the data on the right side of the bar code are also demodulated in the same manner by continuously using the basic module value obtained by sequential calculation.

Next, the second demodulation will be specifically described with reference to FIG. In addition, here, one character shown in FIG. 7 (black bar B ₁ , B
₂ and white bar W ₁ , W ₂ ) demodulation is described.

First, in step b ₁ , the black bar present in one character
Width of B ₁ and B ₂ T _B1 and T _B2 Difference DB (= | T _B1 −T
_B2 |). At the same time, the sum AB of the above widths T _B1 and T _B2
(= T _B1 + T _B2 ) and the sum AW (= T _W1 + T _W2 ) of the widths T _W1 and T _W2 are also obtained (these sums are used in steps c _{9 to} c ₁₂ described later). Proceeding to step b _2, the upper width T _B1,
All of T _B2 , T _W1 and T _W2 are added, and this is divided by the total number of modules in one character (for example, “7”) to obtain the basic module value RM ₀ for the one character. Next step b
_{In 3} , the difference D between the black and white bars obtained in step b ₁ above
B and DW are the basic module values RM obtained in step b ₂ above.
By dividing by ₀ , the numbers of modules m _B and m _W (integers) of the above differences DB and DW are obtained.

Here, since there are only specific combinations for the number of modules (1 to 4) of two black and white bars included in one character, respectively, the number of modules m _B and m _{W of} those differences is also a specific combination. do not have. An example of this combination is shown in FIG. In the figure, the number surrounded by a square indicates the number of modules of difference, and the number in () indicates the total number of modules of each bar for each black or white, and between the black bar and the white bar. Each line connected represents a possible combination with each other. As shown in the figure, when the combination of the number of modules “m _B , m _W ” of the difference is “0,3”, “1,2”, “2,1”, “3,0”, black, Total number of modules for each white "2,5", "3,4",
It can be seen that there is a one-to-one correspondence with "4,3" and "5,2". However, the combination of difference modules is "0,1",
In the case of "1,0", it corresponds to either "4,3" or "2,5" of the total number of modules, or "3,4" or "5,2" respectively. Does not correspond to 1. The correspondence between these is shown in FIG.

Therefore, based on the above combination and correspondence, step
At b ₄ , basic module values M _B and M _W for each black bar and white bar are obtained. An example of a specific process in step b _4, described below based on Figure 4.

First, in step c ₁ , the combination of the difference module numbers “m _B , m _W ” is determined, and the subsequent steps are determined based on FIG. 6.

The combination is "3,0", the case of "0,3", "1,2", "2,1", respectively proceeds to step _{c 9, c 10, c 11} , c 12. In step C _9, black obtained corresponding to combinations of the number of modules "3,0" of the difference as shown in Figure 6, the module number 5,2 of the total of each white, in step b ₁ described above The basic module values M _B , M _W for each black and white are obtained by dividing the sum AB, AW of the widths for each black and white obtained in advance.
Also in step c ₁₀ to c _12, on the basis of FIG. 6, by performing the same processing as that in step c ₉ according each combination to obtain the basic module value M _B, M _W.

On the other hand, in step c ₁ , the difference module number "m _B , m _W "
If the combination is “0.1” or “1,0”, the process proceeds to step c ₂ . In step c _2, select bar (black bar or white bars) towards the number of modules of the difference is "0", it is checked whether overweight watching the width of these bars (step c _3). If the bar is overweight, go to step c ₄ , and if the bar is not overweight, go to step c ₅ . In step c ₄ , select the thinner bar (that is, the one with less influence of weight gain) from the two bars,
In step c ₅ , the thicker bar (that is, the one with less influence of thinning) is selected from the two bars. The number of modules of one black bar or white bar thus obtained is 1 or 2, as is clear from FIG.
Therefore, in order to judge 1 or 2, the width of the bar is compared with the basic module value RM ₀ (see step b ₂ ) to judge whether there is any change (step c ₆ ). If there is no change (i.e. the number of modules it if 1) the process proceeds to step c _7, wherein the the bar know whether black or the black, the number of modules in total for each white "2,5" since "5,2" Kagawakaru, step c _10, c ₉ described above in accordance with the result
Proceed to. On the other hand, if there is a change in step c ₆ (that is, if the number of modules is 2), the process proceeds to step c ₈ , where it is also known whether the bar is white or not. Since it is known whether is “3,4” or “4,3”, the process proceeds to steps c ₁₁ and c ₁₂ according to this result.

In this way, the basic module values M _B and M _W for each black bar and white bar in one character are obtained by the above steps c _{1 to} c ₁₂ . Next, returning to FIG. 3, in step b ₅ , the basic module values M _B and M _W are compared with the old basic module values (old M _B , old M _W ) obtained for the preceding character, Whether or not they are continuous (for example, within 1.6 times)
Check. Without continuity error processing is performed as a demodulation error, and proceeds to the next step b ₆ ~b ₉ if there is continuity. In step b _6, b _7, based on the basic module value M _W of the white bar, respectively determine the number of modules white bar W _1, W _2. Specifically, the width of each white bar W ₁ , W ₂
T _W1 and T _W2 are divided by the basic module value M _W , and the integer values closest to that value are taken as the module numbers of the white bars W ₁ and W ₂ , respectively. At this time, the calculation for correcting the basic module value like the first demodulation is not performed. Also in steps b ₈ and b ₉ , the above steps are performed based on the basic module value M _B of the black bar.
The module numbers of the black bars B ₁ and B ₂ are calculated in the same manner as b ₆ and b ₇ . Finally, it is judged whether the number of these modules is appropriate in the same manner as in step a ₇ described above (step b ₁₀ ). If not, the error process is started. A code consisting of bars W ₁ , B ₁ , W ₂ , B ₂ is converted into a character by a known method based on the number of modules. After that, returning to FIG. 2, the demodulation is started for the next character.

As described above, the first demodulation or the second demodulation in addition to the first demodulation is performed in this embodiment. In the first demodulation, a new basic module value that is sequentially corrected for each of the black bar and the white bar is obtained for each bar (steps a ₁ , a ₃ , a ₅ ), so this basic module value is black. It is the optimal value that takes into consideration the fatness and thinness of the bar. Therefore, the number of modules of each bar (steps a ₂ and a ₄ ) obtained based on such an optimum basic module value becomes very accurate. Therefore, demodulation based on such an accurate number of modules becomes possible, so that the reading rate can be improved and the erroneous reading rate can be reduced.

Also, in the second demodulation, the difference DB, DW between the black and white bars is obtained in step b ₁ , but by doing so, the fat and thin errors of the bars can be canceled out from each other. Therefore, the above difference is not affected by the fatness and the thinness at all. Furthermore, since all added the black bar and white bar 1 in the character in step b _2, Again black, the basic module value RM ₀ to thickening thinning was offset white obtained. From these facts, the module numbers m _B and m _{W of the} difference obtained in step b ₃ based on these values are not affected by the thickening or thinning of the bar at all. Therefore, the number of modules of each bar obtained based on the number of modules of these differences is also very accurate without the influence of the thick or thin bar.
Therefore, by the demodulation based on such a very accurate number of modules, it is possible to further improve the reading rate and further reduce the erroneous reading rate.

As described above, in this embodiment, first, the first demodulation is executed, and if this demodulation is impossible due to the influence of the change in the scanning speed of the barcode pen, the number of modules of each bar is corrected by the retry process. By executing the second demodulation by using the second demodulation, the reading rate can be remarkably improved and the erroneous reading rate can be remarkably reduced.

〔The invention's effect〕

According to the bar code demodulation method of the present invention, the influence of the thick and thin black bars due to the poor printing accuracy of the bar code itself or the change in the scanning speed when scanning with the bar code pen is eliminated, and the reading rate is reduced. Can be significantly improved and the misreading rate can be significantly reduced.

[Brief description of drawings]

1 is a block diagram showing an internal configuration of a bar code reader to which an embodiment of the present invention is applied, FIG. 2 is a flow chart showing a first demodulation according to the embodiment, and FIG. 3 is related to the embodiment. FIG. 4 is a flow chart showing a second demodulation, FIG. 4 is a flow chart showing a specific example of step b ₄ in FIG. 3, and FIG. 5 is a combination of the number of modules of the difference obtained in step b ₃ in FIG. FIG. 6 is a diagram showing an example, FIG. 6 is a diagram showing a correspondence relationship between the combination of the number of modules having the above difference and the total number of modules for each black and white, and FIG. It is a figure which shows an example of the bar code (for example, UPC code). W ₀ , W ₁ , W ₂ …… White bar, B ₀ , B ₁ , B ₂ …… Black bar, WM ₀ , WM ₁ , WM ₂ …… Basic module value of white bar, m ₁ , m ₂ …… Number of modules in white bar, m _B …… Number of modules in difference between black bars, m _W …… Number of modules in difference between white bars, M _B …… Basic module value of black bar, M _W …… of white bar Basic module value.

Claims (5)

[Claims] 1. A bar code demodulation system for converting a bar code into a character based on the number of modules of each bar obtained by reading a bar code composed of a plurality of black and white bars having different numbers of modules. For each of the white bars, the number of modules is obtained based on the basic module value obtained from the previous bar, and the basic module value is modified based on the module number and the bar width actually read to obtain a new basic value. The module value is obtained, and the module number of the next bar is obtained based on the new basic module value. The module number of each bar is sequentially obtained. If possible, obtain the number of modules of the difference between each bar for each of the black bar and the white bar that form one character, and use the module number combination of the difference as the basis. There obtains the number of modules of each bar, the bar code demodulation method, wherein the character conversion based on the number of the module. 2. The correction of the basic module value is a value obtained by dividing the bar width actually read by the number of modules,
The bar code demodulation system according to claim 1, wherein the basic module value obtained from the preceding bar is added and the added value is divided by two. 3. The number of modules of the difference between the bars is obtained by calculating the difference between the widths of the bars, and the added value of the widths of all the black and white bars in the one character is calculated in the one character. The bar code demodulation method according to claim 1 or 2, wherein the basic module value is obtained by dividing by a predetermined total number of modules, and the difference in the width is divided by the basic module value. 4. The number of modules of each bar obtained based on the combination of the number of modules of the difference obtains respective basic module values of black and white bars based on the combination,
The bar code demodulation method according to any one of claims 1 to 3, wherein the bar width is calculated by dividing the width of each bar by the basic module value. 5. The bar module of each of the black and white bars obtained based on the combination is continuous only with the base module value of the preceding character. The bar code demodulating system according to claim 4, wherein the number of modules is obtained.