JPS60108979A - Ne7 type bar code symbol demodulating system - Google Patents

Abstract

PURPOSE:To attain highly accurate reading and precise demodulation by subtracting adjacent black bars and adjacent white bars each other and comparing the subtracted results with a threshold found from bar code symbol length. CONSTITUTION:Subtractors 1, 2 subtract adjacent black bars and adjacent white bars each other. On the other hand, a decision reference value forming circuit 3 forms a threshold value by reading the whole length of the array of seven bars of the bar code symbol. The difference values from the circuits 1, 2 and the threshold signal outputted from the circuit 3 are inputted to decision circuits 4, 5 to decide the bar width. The decided results are sorted by a selecting circuit 6 and the sorted signals are stored in a black bar result storing circuit 7 and a white bar result storing circuit 8 respectively to set the white bars and black bars expressing one character. Decision result converting circuits 9, 10 convert the white bars and black bars into simplified codes respectively. The simplified codes are applied to a demodulating circuit 11 to demodulate the character.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) 0 Technical Field of the Invention The present invention relates to a method for demodulating NWT barcode symbols, and more particularly to an improvement in the reading accuracy of NWV barcode symbols and an accurate demodulation method.

(b11 Background of the Invention Recently, systems that use barcode symbols have expanded significantly in the distribution industry and have been put into practical use in PO3 terminals, inventory management, etc.The reason for this is that barcode symbols are extremely easy for computers to input and output. By being a means.

However, in this barcode symbol, white bars and black bars shown in Figure 1 (al) are arranged alternately within a small space written alongside the product name, and each bar has two different bar widths. There are many problems because the array consists of a total of 817 bars, which are a combination of different types of bars (module 2.5 and module 1).

For example, if there is printing blur on the barcode symbol,
Further, when a barcode symbol is attached to a cylindrical product, the mutual spacing between the bars of the barcode symbol to be read varies.

Even in the above cases, there is a need for a highly reliable reading and demodulation method that reads barcode symbols with high precision and demodulates them into characters accurately.

(C), Prior Art and Problems The NWV barcode symbol consists of four black bars with low optical reflectance and three white bars with high reflectance, as shown in Figure 1+al. There is one thick bar with module 2.5 in each of black and white, and the other 5 bars are 5 thin bars with module l, making a total of 7 bars, for a total of 10 modules. , one character is expressed by arranging these seven bars in a prescribed manner.

Generally, barcode symbols are read optically using a laser beam, which scans the array of barcode symbols each time to convert the array of bars into an electrical signal, and then converts the bar width into an electrical signal based on the sampling clock signal. °ζ is read according to the number of pulses.

However, since the laser beam that scans the barcode symbol moves in a plane, when reading a barcode symbol on a cylindrical product, the center and edges of the barcode are different. Differences occur in the arrangement of the bars read in the barcode.

Also, for example, if a barcode symbol is printed or blurred, the black bar becomes thicker by the amount of blurring, and the white bar becomes thinner by that amount. cause movement.

Even in such cases, it is necessary to accurately read barcode symbols and demodulate them into characters.

There are two main types of demodulation methods for conventional NW7 barcode symbols: one is a bar width absolute value comparison method that determines the size of a module by comparing the absolute values of the read bar widths; This is a proportional comparison method that determines the size of a module using a threshold value proportionally determined from the maximum bar width of the absolute value of the read bar widths.

However, since the former method is a comparison judgment of the absolute value of the bar width, even if the bar width changes uniformly, there is printing blur on the bar as shown in Figure 1 (bl), and the original bar width of B is different from the original bar width. 1 and the bar width of B is 2.5, even if the bar width becomes larger, it will not reach the theoretical module width of 2.5:l.1 For example, if the blur is 0°2, 2. 9 il, 4, which has the disadvantage that the discrimination threshold value fluctuates, and the latter has the disadvantage that the reference discrimination value itself is greatly affected by changes in the bar width.

(d) 9 Purpose of the invention The present invention is based on NW7 series 7, -iodine and bo2. ．． ) reading.

Regarding the extraction and demodulation method, in view of the above drawbacks, adjacent black bars and adjacent white bars are subtracted from each other for each black bar and white bar, and compared with a threshold value determined based on the barcode symbol length, the high The object of the present invention is to provide a method for accurately demodulating the read barcode symbol into a character after reading the barcode symbol accurately.

(e) 9 Structure of the Invention The above object relates to the reading and demodulation of N'W7 barcode symbols, by counting the total length of the seven bar arrays of NWV barcode symbols, A discrimination basic value creation circuit is provided to create a threshold value, while a subtraction circuit performs mutual subtraction between the black bar and the adjacent black bar via the white bar for the read NWT barcode symbol. The difference value obtained by performing mutual subtraction with the adjacent white bar through the black bar and the above threshold value are compared by a circuit that determines the size of the module of the bar.
After determining the state change of each bar, it is inputted to a black bar result storage circuit and a white bar result storage circuit for converting the black bar and the own bar into one character through a selection circuit, and the corresponding black This is achieved by inputting the outputs of the bar result storage circuit and the white bar result storage circuit into a judgment result conversion circuit that converts the respective simplified codes, and demodulating the characters by each combination of white par and ring par. Ru.

(f) 1 Embodiment of the Invention The present invention provides highly accurate reading of NW7 barcode symbols and an accurate demodulation method. This threshold is set by counting the total length of the seven bar arrays of the barcode symbol that is the target of reading, and corresponding to the total length. Since a predetermined threshold value is set according to the above criteria, this threshold value becomes an extremely rationally set determination criterion.

On the other hand, the read barcode symbol is processed by a subtraction circuit, so that the black bar mutually subtracts the adjacent black bar through the white bar, and similarly, the white bar mutually subtracts the adjacent white bar through the black bar. Since the difference values obtained by performing the above steps are compared with the above threshold value, it is possible to identify barcode symbols or bars attached to cylindrical products, etc. It becomes possible.

To explain specifically how to set the threshold, there are two types of NW7 barcode symbols: module 2.5 and module 1, so the threshold setting is based on the difference between these two types of modules, 1 and 5. 0, which is exactly 1/2 of the module.
The setting is 75.

The discrimination basic value creation circuit creates a threshold by reading the entire length of the seven bar array of the barcode symbol, so in order to obtain a value near the threshold value of 0.75, the discrimination basic value creation circuit reads the entire length of the seven bar array of the barcode symbol. The total length of the seven bar array of the symbol is read as Cn using the clock pulse, and this corresponds to the ]O module. Therefore, for ease of circuit configuration, it is most appropriate to divide it by 14, and become.

Cn/14=1/14=0.714 (11This threshold value is determined by reading the total length of the module made up of the seven bar arrays of the barcode symbol and using this read value as the standard. This is an extremely reasonable number.

The meaning of this threshold value is that if the subtracted value of the read black bar or the own bar is smaller than 0.714, there is no change, and on the other hand, if it is larger than 0.714, it is judged as an increase or decrease. It turns out. If we use this threshold value to mutually subtract the black and white bars mentioned above, we get the second
There are four types of state changes shown in the figure.

These four types of state changes are defined by three types of areas divided by threshold values as shown in Figure 3, and each of the ingredients is
The area will be encoded as I, 00, and IO. Figure 4 shows a barcode symbol corresponding to a character.
FIG. 5 shows the results of comparing the difference values obtained for each of the white bar and black bar with the threshold value using the subtraction circuit.

In FIG. 5, the code of the black bar discrimination result is ooo'
ooi, 000110.100000, and 01100
There are four types of 0, but in order to demodulate to characters, the first two focuses of each are used to create 0, 101, 10, and 11.
Simplify according to each. Similarly, the white bar discrimination results are simplified by adopting the first two bits corresponding to 0001.0110 and 1000 (713 types, oo, 6t, and IO, respectively).

The bar code symbol is demodulated into characters by combining the white bar result and the black bar result, as shown in FIG. 6, to generate all the characters.

FIG. 7 is a block diagram showing the circuit system of the present invention.

Subtraction circuits 1 and 2 perform subtraction between adjacent black bars and between adjacent white bars as shown in equation (2). , bl byl-2
+ 11vl-2b, f21(b, , :b, to b
7) These difference values and the threshold signal output from the discrimination basic value creation circuit 3 are used in the judgment circuits 4 and 5.
The width of the 1°ζ bar is determined by:

These results are classified by the selection circuit 6 into the three types of state change regions mentioned above, and the signals classified into the state change regions are sent to the black bar result storage circuit 7 and the white bar result storage circuit 8, respectively. A white bar that is stored and represents one character,
The black bar is set.

The determination result conversion circuits 9 and 10 are circuits that convert each of the white bar and the black bar into a simplified code,
The simplified code of this white bar and black bar is the demodulation circuit 1
1, demodulation into characters is performed.

(g) 1. Effects of the Invention As explained in detail above, the present invention is a demodulation method for NWV barcode symbols that allows extremely high precision barcode reading and accurate demodulation. , a highly reliable device can be realized.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the barcode, Figure 2 is a diagram showing changes in bar status, Figure 3 is a diagram explaining the bar width area depending on the threshold value, and Figure 4 is the NW7 series barcode symbol and characters. A diagram showing the correspondence, Figure 5 is a conversion diagram of the discrimination results of black bars and white bars and code conversion, Figure 6 is a demodulation diagram of a character based on the combination of white bar results and black bar results, Figure 7 is a block diagram of the circuit. In Figure 7, 1.2 is a subtraction circuit, 3 is a discrimination basic value creation circuit,
4.5 is a determination circuit, 6 is a selection circuit, 7 is a black bar result storage circuit, 8 is a white bar result storage circuit, 9.10 is a determination result conversion circuit, and 11 is a character demodulation circuit.

Claims (1)

[Claims] In reading NWT barcode symbols and demodulating characters, a discrimination basic value creation circuit counts the total length of the seven bar array of the NWT barcode symbol and generates a threshold value corresponding to the counted value. On the other hand, in the read NWT barcode symbol, the black bar mutually subtracts the adjacent black bar through its own bar through the subtraction circuit, and similarly, the white bar mutually subtracts the adjacent white bar through the black bar. The change in the state of each bar is determined by comparing and determining the size of the module of the bar with the difference value obtained by performing mutual subtraction and the above threshold value.
Further, the input is passed through a selection circuit to a black bar result storage circuit and a white bar result storage circuit for setting the black bar and white bar to one character, and the outputs of the black bar result storage circuit and white bar result storage circuit are respectively input. NW characterized in that the character is demodulated by each combination of the white bar and the black bar after the determination result is input to a conversion circuit that converts it into a simplified code.
7 series barcode symbol demodulation method.