JPH0470667B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] The present invention provides a bar code demodulation method in which bar width is determined based on a threshold value based on a count value obtained by reading a bar code. Demodulation is performed using a first method that determines the bar width based on the first method, and if a reading error occurs in the demodulation using the first method, a new threshold value is obtained by dividing the sum of each bar by a specific number, By performing demodulation using the second method when the continuity of this threshold value is guaranteed, it is possible to follow changes in scanning speed, and it is possible to prevent abnormal values from being read.
This makes it possible to significantly improve the reading rate and significantly reduce the misreading rate.

[Industrial application field]

The present invention relates to a barcode demodulation method used in a barcode reading device, and in particular makes it possible to set a threshold value, which is a standard for determining the bar width of a read barcode, to an appropriate value. This relates to a barcode demodulation method.

Determining the width of the black and white bars that make up a barcode is affected by the speed at which the barcode is scanned, and it is extremely difficult to accurately read and demodulate this with a hand-operated barcode pen. Improving the reading rate and reducing the misreading rate are major technical challenges.

[Conventional technology]

Recently, in supermarkets and the like, product name code numbers, prices, etc. are displayed in the form of stick-shaped barcodes, which are printed on foods, miscellaneous goods, etc., or attached as labels. This barcode is used in industries that handle a large number of shoppers in a short period of time.
The information read by a barcode reader and recorded therein is used for various purposes such as point of sale information management.

Normally, barcodes are read by scanning a surface on which a barcode is displayed with light and demodulating coded data from reflected light modulated by the barcode. Currently, there are many types of barcode formats, but there are usually two types of bars: black bars and white bars, and the widths of the black and white bars vary in size. A code representing a data character etc. is constructed by a combination of bar widths. Therefore, accurate detection of this bar width is extremely important in demodulating the bar code, and is required to be unaffected by variations in the speed at which the bar code is scanned.

The barcode reading device scans a barcode with a barcode pen, etc., obtains a count value corresponding to the bar width from an electrical signal, and sequentially scans the barcode with a barcode pen or the like to obtain a count value corresponding to the bar width, and sequentially scans the barcode with a wide width (hereinafter referred to as W) and a narrow width of the white bar. (hereinafter expressed as N)
The bit pattern is determined from the combination data of W and N of the black bar and white bar for one character, and is processed as data.

In Japanese Patent Application Laid-Open No. 180380/1983, the present applicant first performs first demodulation in order to follow fluctuations in barcode scanning speed and achieve a good reading rate. This discloses a conventional technique related to a barcode demodulation method in which a second demodulation is performed when a barcode demodulation occurs. That is, in the first demodulation method, the count value N of the first narrow bar near the start code or stop code and the count value W of the first wide bar are extracted, and (N+W)/2 is calculated. is set as a threshold value SH, the bar width of the first bar is determined using the threshold value SH, and a count value is calculated based on the determination result of the first bar width.
Using N' or W' and the count value N or W, calculate (N'+W)/2 or (N+W')/2 to determine the threshold value SH', and use the threshold value SH' to calculate (SH+
SH')/2 is calculated and set as the threshold SH'', and the threshold
SH'' is used to determine the bar width of the next bar, and the bar width of subsequent bars is calculated by calculating the threshold value SN''. This operation is performed for black bars and white bars. Next, the second
In the demodulation method, if a reading error occurs in the first demodulation method, a new threshold value is set by dividing the sum of the count values of all the black bars for one character by the first specific number. Determine the bar width of the black bar as , and determine the bar width of the white bar as a new threshold value by calculating the sum of all the count values of the white bar for one character by a second specific number. perform an action.

[Problem that the invention seeks to solve]

In the above-mentioned conventional barcode demodulation method, the first demodulation method corrects the bar width count value to the threshold value SH every time the bar width count value N or W appears, so the threshold value changes according to the scanning speed of a light pen, etc. Although the reading rate improves, when moving to the second demodulation method, the continuity of the threshold values is not guaranteed, so the count values N and W
When it corresponded to a certain number, there were cases where it was misread. In other words, when scanning a barcode with a barcode pen, it is returned midway, a line is drawn on the barcode with a pencil or ballpoint pen, or the barcode has a stain or spot. The count value may become abnormal and continuity may not be guaranteed.

The present invention was made to solve these problems, and its purpose is to provide a barcode demodulation method that can significantly improve the reading rate and significantly reduce the misreading rate. shall be.

[Means for solving problems]

The barcode demodulation method of the present invention first performs the first demodulation using a threshold value that corresponds to the scanning speed, and if a reading error occurs, a new threshold value determined from the total bar width count value is continuously applied. determine the gender,
When continuity is guaranteed, the second method of demodulation is performed using this threshold. That is, first, the average value of the count value N of the first narrow bar and the count value W of the wide bar is determined and set as the threshold value SH. Then, the count value N' or W' of the first bar is determined using this threshold value SH, and the count value N',
The average value of W or N and W' is determined and set as the threshold value SH'.
Next, calculate the average of the threshold values SH and SH′ and obtain the threshold value SH ₁
shall be. This threshold value SH ₁ is used to determine the bar width of the next bar, and thereafter, the threshold value SH ₁ is sequentially determined and determined in the same manner, and demodulation of the first method is performed.

If a reading error occurs in demodulation using the first method, the threshold value SH ₂ is determined by dividing the total count value of each black bar and white bar for one character by their respective specific numbers. Then, when the values of the above two thresholds SH ₁ and SH ₂ satisfy 1/1.6≦SH ₂ /SH ₁ ≦1.6, it is determined that the thresholds SH ₁ and SH ₂ have continuity, and the threshold SH ₂ is used. Determine the bar width and
Perform demodulation using the following method.

[Effect]

In the demodulation of the first method, the sequentially corrected threshold values obtained for each black bar and white bar are optimal values that follow changes in scanning speed. Therefore, the determination of each bar width obtained based on such an optimal value is accurate, and demodulation is performed based on this accurate determination, so the reading rate improves and the reading rate decreases. do.

In addition, in the demodulation of the second method, a new threshold value SH ₂ , which is calculated by dividing the total bar width count value for each of the black bars and white bars in one character by a specific number, is used to prevent extreme changes in scanning speed. Even if there is a difference in width, it will be the optimum value that approximately corresponds to the width of each bar for one character. This new threshold SH ₂ is then compared with the threshold SH ₁ for demodulation of the first method, and when continuity is guaranteed, demodulation of the second method is performed based on the threshold SH ₂ . Therefore, the determination of each bar width based on the optimal value with guaranteed continuity is accurate. That is, since cases where the bar width count value becomes an abnormal value are removed, the reading rate is further improved and the reading rate is reduced.

In this way, in the present invention, it is possible to follow the scanning speed and achieve a high reading rate and a low misreading rate by using only the first method of demodulation, but when the first method cannot be demodulated, continuity can be improved. By performing the second method of demodulation using the guaranteed new threshold, it is possible to significantly improve the reading rate and significantly reduce the misreading rate.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

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

In the figure, a photoelectric conversion section 1 is composed of, for example, a barcode pen, and is a means for scanning a barcode to obtain an optical signal and converting it into an electrical signal.
The analog-to-digital converter 2 is a means for converting the analog signal output from the photoelectric converter 1 into a digital signal. This digital signal is a step-like signal of "1" and "0", each having a pulse width corresponding to the width of each black and white bar constituting the bar code. The signal converter 3 has the above-mentioned black,
This means creates a pulse signal at the change point of "1" and "0" in a digital signal of "1" and "0" corresponding to white, and outputs a black and white signal corresponding to each. The time interval of the pulse signals obtained here corresponds to the widths of the black and white bars.

The barcode thus converted into a pulse signal and a black and white signal is demodulated via the data bus 4. This demodulation uses a timer counter section 5 and a memory section (RAM) 6, and is based on a microprogram in the memory section (ROM) 7.
This is done under the control of the main control unit (CPU) 8. In addition,
A line control section 9 transmits the barcode reading data to an external base unit, and a power supply section 10 supplies power to each block.

The barcode demodulation method according to this embodiment will be specifically explained below.

In this embodiment, a threshold value that follows the scanning speed is determined and demodulation of the first method is performed, and if a reading error occurs with this, a new second threshold value is determined, and the continuity is determined. The second method of demodulation is performed. Here, a case will be described in which barcodes as shown in FIG.

FIG. 2 is a main flowchart of demodulation according to an embodiment of the present invention. In the figure, first, a bar code is input in step _a1 , and when the bar code is input, a start code is demodulated in step _a2 . Next, in step _a3 , it is determined whether or not demodulation of the start code has been completed normally.If it has not been completed normally, the process returns to step _a1 to wait for barcode input, and if it has been completed normally, the process proceeds to step _a4 , which will be described later. , and demodulates one character.
That is, in steps _a1 to _a3 , when the start code of the input barcode is successfully demodulated, demodulation of subsequent barcodes is executed.
Next, in step _a5 , it is determined whether the demodulation of one character (step _a4 ) has been completed normally.If it has not been completed normally, the process returns to step _a1 to input the barcode, and if it has been successfully completed, Proceed to step _a6 . In this step _a6 , it is determined whether or not it is a stop code. If it is not a stop code, the process returns to step _a4 and the demodulation of one character is repeated again. If it is a stop code, the reading ends as normal.

Next, the demodulation of one character (step a ₄ ) will be specifically explained based on FIG.

First, in step _b1 , one character is demodulated using the first method. Details of demodulation by this first method are shown in FIG. In FIG. 4, first, in step _c1 , the count value N of the first narrow bar near the start code of the bar code (the counted value of the bar width by the timer counting section 5) and the count value N of the first wide bar near the start code of the bar code are determined. The count value W is read out, and the threshold value SH is determined using the count values N and W. Specifically, this is performed based on the formula SH=(N+W)/2. Next, in step _c2 , the above threshold value is
Use SH to determine the bar width of the first bar that makes up the next character (for example, "0"), and based on the determination result, if the bar width is narrow, the count value will be
N′ or the count value if the bar is wide
Read W′. Then, in step _c3 , the threshold value SH' is determined using the count value N' or W'. Specifically, SH'=(N'+W)/2 or (N+
This is done based on the formula W′)/2. Next, step
c ₄ , use the above thresholds SH and SH′ to calculate the threshold
SH''=(SH+SH')/2 is determined. Then, in step _c5 , the bar width of the next bar is determined using the threshold value SH''. Thereafter, in step _c6 , the processes of steps _c2 to _c5 are sequentially repeated for the black bar and white bar. And step c ₇
In the step, the combination data of W and N of a black bar and a white bar for one character is converted into a corresponding bit pattern. In step _c8 , the bit pattern is compared with the bit pattern of the corresponding character, and the corresponding character is demodulated. Demodulation of one character by the first method is completed through the following steps.

Next, in step _b2 of FIG.
Determine whether the demodulation using the method has been completed normally without any reading errors. If it has been completed normally, the process proceeds to step _b3 , where it is determined whether or not it is a stop code.If it is not a stop code, the process returns to step _b1 to demodulate the next character, and if it is a stop code, the demodulation ends as normal. If the process does not end normally and a reading error occurs, the process proceeds to step _b4 to find a new threshold using the second method. FIG. 5 shows how to find the new threshold value in step _b4 . In FIG. 5, first, in step _d1 , the totals X and Y of all the count values of the black bar and white bar for one character are calculated. Then, in step _d2 , the sums X and Y are divided by specific numbers A and B, respectively, and the second demodulation threshold is determined.
Find SH ₂ . Specifically, SH ₂ =X/A, Y/
This is done based on formula B.

The above specific numbers A and B are, for example, X/A≒(N+
W)/2, Y/B≒(N+W)/2, the first
and second specific numbers A and B.

Next, in step _b5 of FIG. 3, the threshold value SH ₂ for determining the last bar width for one character in the first method is set as SH ₁ , and this threshold value SH ₁ and the new threshold value SH 2 of the second method are set as SH ₁ . Compare with to determine whether there is continuity. That is, it is checked whether _{the threshold value SH 2 of} the second method has become an abnormal value compared to the threshold value SH 1 of the first method. The causes of this abnormal value include a scanning error on the barcode (for example, a scan that returns halfway), a stain, a spot, etc. on the barcode. For specific continuity determination, the threshold SH ₁
This is done depending on whether the ratio between SH2 and _SH2 is about 1.6 times or less. Setting this ratio to about 1.6 times is a reasonable judgment considering the speed change, and at about 1.5 times, the speed change is large because the pen code is manually operated.
This is because the judgment is difficult, and at around 1.7 times, the judgment becomes insufficient even when speed changes are taken into account. This continuity determination is performed based on the following formula.

1/1.6≦SH ₂ /SH ₁ ≦1.6 In other words, if the thresholds SH ₁ and SH ₂ satisfy the above formula, it is determined that there is continuity, and the process proceeds to step b ₆ and sets the thresholds.
A second demodulation is performed by determining the bar width of one character using SH ₂ , and if it is not satisfied, it is treated as a demodulation error. The second demodulation in step _b6 above converts the combination data of W and N of the black bar and white bar for one character into the corresponding bit pattern using the threshold value _SH2 , and demodulates into the character corresponding to this bit pattern. do. Next, in step _b7 ,
It is determined whether demodulation using the second method has been completed normally without any reading errors. If it has been completed normally, the process proceeds to step _b8 , where it is determined whether or not it is a stop code.If it is not a stop code, the process returns to step _b1 and demodulation is performed again using the first method, and if it is a stop code, the demodulation is completed as normal.

FIG. 6 is a diagram illustrating the bar width count value according to this embodiment. In the figure, the count value for one character (for example, N, W,
N, N, W) are read out. Here, the threshold value SH ₁ of the first method changes following the scanning speed. Next, when a reading error occurs, the threshold value of the second method is
Determine using SH ₂ . This threshold value _SH2 is the count value of the bar width for one character (for example, X, N, N, N,
Since the sum of W) is divided by the specific values A and B, the value almost corresponds to each count value.

As described above, in this embodiment, when a reading error occurs during demodulation using the first method, demodulation using the second method is performed. At this time, it is determined whether there is continuity between the threshold value SH ₁ of the first method and the threshold value SH ₂ of the second method. In the first method, a threshold value SH ₁ is obtained that is sequentially corrected corresponding to the bar width count value for each of the black bar and white bar, so the bar width determination based on this threshold value SH ₁ is based on the bar code It follows the change in scanning speed above and is accurate. Therefore, demodulation based on this accurate bar width determination becomes possible, and it is possible to improve the reading rate and reduce the misreading rate.

Furthermore, in the second method, since the threshold value SH ₂ is determined from the sum of the count values of the respective bar widths for the black bar and the white bar, reading is performed even if there is an extreme change in the scanning speed. Furthermore, in step _b5 of the second method, the final threshold value SH ₁ used for demodulation of the first method (threshold value for determining the final bar width for one character) and the threshold value used for demodulation of the second method are determined. Since continuity with SH ₂ is guaranteed, abnormal values will not be read and erroneously demodulated. To determine this continuity, if the threshold value SH ₂ used for the demodulation of the second method is within about 60% of the threshold value SH ₁ used for the demodulation of the first method, the reading rate will further improve and misreading will occur. It has been confirmed that a further reduction in the ratio can be achieved.

In the present invention, any method may be used as long as the bar width is determined using a threshold value and demodulation is performed based on the determination result, and any bar code format may be used. In addition, in the above embodiment, the determination to ensure the continuity of the threshold values SH ₁ and SH ₂ is based on the assumption that the threshold value SH ₂ changes by about 60% with respect to the threshold value SH ₁ , but this is not limited to this example. figure,
Various values can be set depending on the barcode format or experimental results.

〔Effect of the invention〕

According to the barcode demodulation method of the present invention, continuity between the threshold value of the first method and the threshold value of the second method is guaranteed, so it is possible to follow the scanning speed when scanning with a barcode pen. , and abnormal values are no longer read, making it possible to significantly improve the reading rate and significantly reduce the misreading rate.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the internal configuration of a barcode reader to which an embodiment of the present invention is applied, FIG. 2 is a main flowchart showing demodulation according to the embodiment, and FIG. FIG. 4 is a flowchart showing the demodulation of characters in the first method according to the same embodiment. FIG. 5 is a flowchart for determining the threshold value in the second method according to the same embodiment. The figure shows bar width count values according to the same embodiment, and FIG. 7 is a diagram showing an example of a bar code (for example, industrial 2 out of 5). 1...Photoelectric conversion unit (barcode pen), 2...
Analog-digital converter, 3...Signal converter, 4
...Data bus, 5...Timer counter section, 6,
7... Memory section, 8... Main control section, 9... Line control section, 10... Power supply section, N, W, N'W'... Count value, SH ₁ , SH ₂ ... Threshold value, W, Y...Total count value, A, B...Specific number.

Claims (1)

[Scope of Claims] 1. In a barcode demodulation method in which a bar width is determined based on a threshold value based on a count value obtained by reading a barcode consisting of a plurality of black and white covers, each of the barcodes read Demodulation is performed using the first method that determines the bar width based on the threshold value SH ₁ that is sequentially corrected for each bar count value, and if a reading error occurs in the demodulation using the first method, one additional character is decoded. A new threshold SH ₂ is obtained by dividing the total count value of each bar by a specific number, and the value of the two thresholds SH ₁ and SH ₂ is 1/1.6≦
Demodulation of a second method in which it is determined that the modified threshold SH ₁ and the new threshold SH ₂ have continuity when SH ₂ /SH ₁ ≦1.6, and the bar width is determined using the threshold SH ₂ . A barcode demodulation method that performs the following. 2. The demodulation of the first method reads the count value N of the first narrow bar and the count value W of the first wide bar of the barcode,
The average value of the count values N and W is determined as a threshold value SH, the bar width of the leading bar is determined using the threshold value SH, and the count value N' or W' is determined based on the determination result of the leading bar width. Using the count value N or W, the average value of the count values N', W or N, W' is determined as a threshold value SH', the average value of the threshold values SH, SH' is determined as a threshold value _SH1 , and the The bar width of the next bar is determined using the threshold value SH ₁ , and the bar widths of subsequent bars are determined and demodulated sequentially by obtaining the same threshold value SH ₁ as described above. Barcode demodulation method described in section. 3 The specific number of demodulations in the second method is the first specific number A, which is determined by X/A≒(N+W)/2, where X is the sum of all count values of the black bars for one character. If the sum of all count values of the white bar for one character is Y, then Y/B≒(N+W)/
2. The barcode demodulation method according to claim 1, wherein the second specific number B is determined by 2.