JPH0256687A - Bar code reading device - Google Patents

Abstract

PURPOSE:To reduce the number of constituting parts and to obtain the bar code reading device of high performance at a low price by changing the slice value of a video signal slice part in correspondence to the change of an output value from a scanning beam photo-detecting part which measures the output value of scanning beam. CONSTITUTION:A reflected light by the bar code symbol of the scanning beam to be outputted from a scanning part 1 is photo-detected by a reflected light photo-detecting part 3 and goes to be an electric signal. Then, the reflected light is amplified by a slice voltage generator 24, outputted to a comparator 6 and compared with a slice voltage which is the output of an integrator 5. Here, when the output of a laser tube is high, since the reflected light from the bar code symbol goes to be large, the output value of a video signal amplifying part 4 also goes to be large. Thus, a pulse train to exactly correspond to the width of a white bar wi and a black bar bi can be obtained from the comparator 6 and even when there is the output fluctuation of the laser tube, the high performance can be obtained. Then, the number of the constituting parts can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a barcode reading device that reads barcode symbols affixed or printed on articles.

[Conventional technology]

The fixed slice method shown in FIG. 3 is usually used as a video signal slicer method in a conventional bar code reader. In the barcode reading device shown in FIG.
The surface of the barcode as shown in FIG. 4 is scanned by a scanning beam outputted from the barcode, and the light reflected from the surface of the barcode is converted into an electrical signal by the light receiving section 22, and amplified by the video signal amplifying section 23. and outputs it to the video signal slicing section 27.

Here, the recognition unit 26 recognizes the black 7<b of the barcode shown in FIG.
In order to decode a barcode by measuring the width of the white bar wi, the electrical signal output from the comparator 25 is waved in a pulse train with a pulse width proportional to the width of the black bar wi and the white bar wi. Must be. Therefore, in the video signal slice section 27, the analog signal output from the video signal amplification section 23 and the voltage output from the slice voltage generator 24, that is, the slice voltage, are compared in the comparator 25, and when the analog signal is higher than the slice voltage, The comparator 25 outputs a high level signal assuming that the scanning section 21 is scanning over the white bar wi, and when the analog signal is lower than the slice voltage, it is assumed that the scanning section 21 is scanning over the black bar bi. By outputting a low level signal, the comparator 25 generates a pulse train with a pulse width proportional to the widths of the black bar bi and the white bar wi. This method is called a fixed slice method because the slice voltage is fixed.

[Problem to be solved by the invention]

In the barcode reading device using the fixed slice method shown in FIG. 3 described above, as shown in FIG. Therefore, it becomes impossible to obtain from the comparator 25 a pulse train having a width proportional to the width of the black bar bi and white bar wi in FIG. In order to obtain accurate pulse trains proportional to the black bar bj and white bar wi when the output of the video signal amplifying section 23 decreases as shown in the output 13, the slice voltage is set by lowering it to the slice voltage 16 shown in FIG. However, when the output of the video signal amplifying section 23 becomes large as shown in the output 11 of FIG. 2, the black bar b1. This has the drawback that not only is it impossible to obtain a pulse train having a width proportional to the white bar wi, but also that all of the bars are determined to be white bars.

Here, the first factor that causes the magnitude of the analog signal of the video signal amplification section 23 to change is the black bar b shown in FIG.
There is a change in the reflectance of light from i and white bar wi, and the second
There is a fluctuation in the output of the laser tube, which is the light source of the scanning beam generally used in the scanning section 21.

Regarding the change in reflectance, which is the first factor, the reflectance of the barcode symbol shown in FIG. 4 is specified by JIS. also changes. Therefore, since changes in this analog signal are predictable, it is possible to set the slice level in the video signal slicer 27, that is, the output voltage of the slice voltage generator 24, to an optimal voltage value.

However, the second factor is that the laser tube, which is the light emitting source of the scanning beam, suffers from output fluctuations such as periodic output fluctuations at the start of light emission, output fluctuations due to temperature changes in the usage environment, and output decreases as the light emission period increases. be. These power fluctuations of the laser tube are generally unpredictable here. Furthermore, suppressing output fluctuations is difficult to achieve because it requires sorting of laser tubes, constant temperature control of the laser tube mounting case, etc., which results in increased costs.

Therefore, unpredictable output fluctuations of the laser tube are inevitable, and if a laser tube is used in the scanning section 21, changes in the analog signal output of the video signal amplification section 23 due to output fluctuations of the laser tube will also become unpredictable. . In other words, since it is impossible to predict changes in the analog signal of the video signal amplifying section 23, the slice voltage at the video signal slicing section 27,
In other words.

It becomes impossible to set the output of the slice voltage generator 24 to an optimal voltage value. Specifically, in two states where the output of the laser tube is high and low at the same time, a pulse train having a width proportional to the width of the black bar bi and white bar wi shown in FIG. 4 is obtained from the comparator 25. In normal fixed slicing methods, the slice level is set when the output of the laser tube is high, so the black bar bi and white bar wi correspond to the decrease in output as the laser tube elapses. The disadvantage is that it is not possible to obtain an accurate pulse train.

[Means to solve the problem]

The present invention includes a scanning section that scans a barcode symbol with a scanning beam, a scanning beam receiving section that receives reflected light by the scanning beam and converts it into an electrical signal, and a video signal that amplifies the electrical signal from the scanning beam receiving section. A bar comprising a signal amplifying section, a video signal slicing section that converts an analog signal of the video signal amplifying section into a digital signal, and a recognition section that receives an output from the video signal slicing section and decodes the barcode symbol. The code reading device has a scanning beam receiving section for measuring an output value of the scanning beam, and is configured to change the slice value of the video signal slicing section in accordance with a change in the output value of the scanning beam receiving section. It is characterized by:

Note that the barcode reading device described above may be configured to change the video signal amplification degree of the video amplifying section in accordance with a change in the output value of the scanning beam receiving section.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, in which a scanning beam output from a scanning section 1 is incident on a scanning beam receiving section 2 in the device, where it is converted from light into an electrical signal, and is converted into an electrical signal by an integrator 5. is input.

Here, the output of the scanning beam receiver 2 is the output of the scanning beam receiver 2.
It is a pulse output because it is output only when the scanning beam is incident on it. The peak value of this pulse is proportional to the output value of the scanning beam, but since a DC voltage is required as the slice voltage input to the comparator 6, the output of the scanning beam receiver 2 is input to the integrator 5. to obtain a slice voltage and output it to the comparator 6.

Next, the reflected light of the scanning beam output from the scanning section by the barcode symbol is received by the reflected light receiving section 3,
This becomes an electric signal, is amplified by the slice voltage generator 24, is output to the comparator 6, and is compared with the slice voltage that is the output of the integrator 5.

Here, if the output of the laser tube is high, the amount of light reflected from the barcode symbol will increase, so the output value of the video signal amplification section 4 will also increase. Here, if the output 11 in Fig. 2 is the output of the video signal amplifying section 4 when the output of the laser tube is high, the slice voltage 14 in Fig. 2 changes when the output of the laser tube is high. The white bar wi in FIG. 4 is thick, and the black bar bi does not become thin. Even when the output of the laser tube becomes low, the slice voltage decreases, so that the white bar wi in FIG. 4 becomes thin and the black bar bi does not become thin. does not become thicker, and from the comparator 6, the white bar in Figure 4 w
It is possible to obtain a pulse train that accurately corresponds to the width of the black bar i and the width of the black bar bi, and high performance can be obtained even if there are fluctuations in the output of the laser tube.

〔Effect of the invention〕

According to the present invention, as explained above, it is possible to realize an inexpensive and high-performance barcode reading device with a small number of component parts.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
Figure 3 is a block diagram of the conventional example; Figure 4 is a block diagram of the conventional example;
The figure shows a general barcode symbol. 1... Scanning section, 2... Scanning beam receiving section, 3...
Reflected light receiving section, 4... Video signal amplification section, 5... Integrator, 6... Comparator, 7... Recognition section, 8... Video signal slice section. No. 111]

Claims (1)

[Claims] a scanning unit that scans the barcode symbol with a scanning beam;
a scanning beam receiver that receives reflected light from the scanning beam and converts it into an electrical signal; a video signal amplifier that amplifies the electrical signal from the scanning beam receiver; and a video signal amplifier that converts the analog signal of the video signal amplifier into a digital signal. A scanning beam receiving device that measures an output value of the scanning beam in a barcode reading device comprising a video signal slicing unit for converting the video signal and a recognition unit for receiving the output from the video signal slicing unit and decoding the barcode symbol. What is claimed is: 1. A barcode reading device comprising: a barcode reading device; and a barcode reading device configured to change a slice value of a video signal slice portion in accordance with a change in an output value of the scanning beam receiving portion.