JPS6037950B2 - Barcode detection device - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in barcode detection devices.

For example, in order to detect information on moving objects such as vehicles and containers at cargo handling yards, barcode boards that represent binary codes by alternately combining black and white bars with long and short widths are installed on these moving objects. It is well known that information is obtained by attaching a sensor and reading it optically on the detection side.

In the conventional barcode detection device, the black and white bar widths are detected by setting an intermediate tone between black and white as the slice level. FIG. 1 is an explanatory diagram of a conventional barcode detection method, where a indicates an example of a barcode, b indicates the detection level of code a, the black bar is the B level, and the white bar is the W
Each represents a level.

Discrimination between black bars and white bars is performed using the S level, which is the intermediate value between the black and white levels, as a slice level, and is converted into a square wave to obtain an output code. is often given, and it is not always possible to accurately detect the black and white level as shown in b. For example, if the entire barcode board becomes dirty and the white reflectance decreases, Figure 1c
The white level W is not output like this. Conversely, in general, if the reflectance of black becomes slightly dirty on the white side, black level B will not be output as shown in d. Furthermore, there is a drawback that barcode detection may be ambiguous due to contamination that compresses the difference between black and white levels and may become indistinguishable. The present invention was made to improve the above-mentioned conventional drawbacks, and is characterized by accurate discrimination even when the barcode is dirty and cannot detect the black and white levels. (Operation site) In management and transportation control, even dirty barcodes can be accurately interpreted, which has a great effect on rationalizing management and control and saving labor.

The present invention will be explained in detail below. FIG. 2 is a configuration example diagram of a barcode detection circuit according to the present invention, in which 1 is a barcode display board, 2 is an infrared light source, 3 is a light receiver, 4 is a slice level separation amplifier, 5 is an AC signal (carrier wave) oscillator, 6 and 7 are amplitude modulators (MO
D), 8 and 9 are slide-back type detectors D, and 10 is a square wave conversion output circuit.

Further, FIG. 3 is a time chart of waveform examples of various parts in FIG. 2. Now, in FIG. 2, when the bar code 1 is irradiated with infrared light from the light source 2, the light receiver 3 receives the light and converts it into an electrical signal and outputs it.

In this case, the barcode plate 1 is moved, or the movement of the barcode plate 1 and the scanning of the barcode plate 1 by the light source 2 and receiver 3 are used together, but here the barcode plate 1 is scanned at a constant speed. If so, the output of the photodetector 3 will have a waveform e in FIG. 3. BB in the waveform diagram is the black bar with no reflection, that is,
The maximum level of the black bar, WW is the maximum reflection of the white bar, that is, the maximum level of the white bar.Actually, the e waveform in the BB and WW ranges is output, but if the barcode plate 1 is soiled and discolored, its black and white amplitude will change. It is output with various changes in the level and center level of the amplitude. The waveform e in FIG. 3 is shown on the assumption that the median of the light reception levels of the black and white bars coincides with the median level S of BB-WW. The e waveform is input to the slice level separation amplifier 4. This amplifier 4 consists of a separation amplifier for the black bar (signal) whose slice level is SB in the e waveform diagram, and a white bar (signal) whose slice level is Sw.
It consists of two separate amplifiers. Each level of SB and Sw is set so that even if there is a change in the black-and-white amplitude level or a change in the black-and-white center level S, the e waveform always intersects with one of the slice levels. For example, if the amplitude waveform e of the black and white bar is closer to BB and the amplitude level is between the center level S and BB, the separation amplifier of the black bar with SB as the slice level operates, and conversely, the e waveform is closer to WW. If so, the white bar separation amplifier with Sw as the slice level operates. These separation amplifiers amplify the amplitude of the e-waveform level corresponding to the black bar or white bar, which is higher than the SB or Sw level, up to a certain level and output it, but a variable amplification circuit is used for the amplifier. Also, due to this separation amplification operation, the third output, which is the output for the black bar, is
The f waveform in the figure and the g waveform which is the output for the white bar are output to NOD6 and MOD7, respectively. In addition,
For example, when the e-waveform is closer to B and the amplitude level is between the center level S and BB, only the f-waveform may be output. Next, amplitude modulated waves (MOO) 6 and 7
To each carrier wave input terminal, a voltage of 10 female HZ to 50 female HZ is supplied from an AC signal oscillator (OSC) 5 at a specific frequency that is sufficiently large compared to the signal speed of the e waveform. , respectively f waveform and g
Amplitude modulation is performed using the waveform.

Their modulated outputs are as shown in the h waveform and i waveform of FIG. 3, respectively, with the h waveform from MOD6 inputting to the slide-back type detector D8, and the i waveform from MOD7 inputting to D9. Here, the slide-back type detector will be explained.

Figure 4 is an example of the circuit, where T is a coupling transformer, D,, D2
is a diode, C, , C2 are capacitors, and R, , R2 are resistors. The charging/discharging time constants of D, and C,,R, are small enough to follow the bar detection signal speed, and the charging time constants of D2, C2, and R2 are also small so that they can follow the bar detection signal speed. The discharge time constant is configured to have a large value several times or more the bar detection signal speed. Further, the winding ratio of w and w2 on the secondary side of the transformer T is 2:1. FIG. 5 is an explanatory diagram of the operation of the circuit shown in FIG. 4. For example, when the amplitude modulated wave shown as n in Figure 5 is input to the input side in Figure 4 and transmitted to the secondary side, w, the output is detected by diode ○, but C, , R, The time constant is small as described above, and the waveform shown in FIG. 5 is output, and the w2 output is detected by the diode D2, and the e2 waveform is output depending on the time constants of C2 and R2. In other words, the e wave is the envelope detection output of the signal wave, and when the e heat wave signal is on (on)
The envelope level of the signal wave is output when there is no signal (off), and the discharge characteristic level of the preceding signal is output. As is clear from the figure, e. is a ten-polarity output and e2 is a unipolar output, but they are added on the detector output side and the output becomes a differential output of e and e2. The level ratio of e,, e2 is 2:1 because the winding ratio on the secondary side is 2:1, and the detector output becomes a positive and negative double current output as shown in the waveform q in Figure 5. . Due to the operation of the detector as described above, in the above example, the detector 8 becomes h
Outputs a 10-polarity i waveform when a signal is input to the waveform input,
In the wave detector 9, the operating polarity of the wave detector is determined so that a unipolarity k waveform is outputted when a signal is inputted in response to an i waveform input.

Furthermore, the outputs of both the 8th and 9th detectors are added and combined as shown in Figure 2, and the output of the 1st waveform is converted into a square wave conversion output circuit 1 in Figure 3.
Send to 0. The circuit 10 converts the waveform into a square wave of constant amplitude, with the 0 and - levels set to L (low) level and the 10 level set to H level, and outputs a bar code as a waveform m in FIG. To illustrate these, for example, e with black and white bars.
When the amplitude level of the waveform is close to B in Figure 3 and the amplitude level is between the center level S and BB, only the separation amplifier indicated by the black bar with SB as the slice level operates, and Sw as the slice level. If the white bar separation amplifier does not operate because the input does not reach the slice level, the waveforms f, h, and j in FIG. 3 are output almost equally, and g. Each waveform of i and k becomes zero or no signal, but since the outputs of detectors 8 and 9, i.e., the outputs of i and k, are added, a waveform of 1 equal to j is output, and the positive and negative signals are at the same level. Double flow type.

This one waveform input is 0 in the circuit 101, and the negative level is L.
In the case of a correct signal, the signal is converted into a square wave m having an H level. Conversely, if the e waveform is closer to WW in Figure 3, g,
Only the i and k waveforms may be output equally, and in this case, one waveform equal to k is output and the corresponding m waveform is output. As mentioned above, when the amplitude level of the black and white bar detection output e obtained from the photoreceiver (3 in Figure 2) is small due to dirt on the barcode board, or when it is closer to black or white, it is necessary to set it in advance. As long as it intersects with either a certain slice level S8 or Sw, the barcode can be accurately determined and output. Next, Fig. 6 is an example in which the slice levels SB and Sw- in Fig. 3 are matched to the center S level of each level of BB and WW, and the e' waveform corresponds to e in Fig. 3 and is black. Assume that e8>raft w holds between the detection level eB of the bar and the detection level ew of the white bar.

In this case, only the black bar separation amplifier 4 in FIG. 2 operates, the amplitude modulator 6 is driven, and the h' waveform, which is an amplitude modulated wave, is output. The e3 and e4 levels in this waveform are proportional to eB and ew in the e' wave, respectively. At this time, there is no output from the amplitude modulator 7. The h' waveform is subjected to slide-back detection by the wave detector 8 and becomes the i' waveform, that is, 1' in this case.
The waveform (i' = 1') is output, but as shown in the i' waveform in Figure 6, when the black bar signal is present, the differential level of e3 as explained above is output, and the output of the detector 8 is e5, and the white bar signal is Sometimes the amplitude level of h' wave is e4, but eB> from w to e
Since 3/2>e4, the output of the detector 8 is the differential output level e6, which is the difference between the level of the discharge characteristic of the preceding e5 (which is referred to as e5d) and the detected level e'4 of e4. Further, since e3/2>e4, the black bar output has ten polarities, whereas the white bar output has one polarity of e5=e5d-e'4, and a bisulfurized 1' waveform is output to the circuit 10. circuit 1
At 0, 0 and - level inputs are L level, and 10 level inputs are H level.
Convert to leveled square wave and output. In this way, in the output of the light receiver 3 where the difference in amplitude between the black and white bars is large and the e waveform is biased towards the BB or WW level, it is possible to match the slice level to the center level S of BB-WW. As is clear from the above description, in the device of the present invention, when required information is displayed on a barcode display board on a moving object such as a vehicle or a container and is read by optical means, the barcode board has a black bar color tone. It is possible to accurately detect black and white bars regardless of whether they are soiled or soiled with a white bar color tone, and is useful for automatic discussion of moving object information in marshalling yard management, transportation control, etc. Since it is accurate, it can greatly contribute to streamlining work and saving labor.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional barcode detection method, FIG. 2 is an example of the configuration of a barcode detection circuit according to the present invention, FIG. 3 is an example of waveforms of each part of FIG. 2, and FIG. Fig. 5 is an explanatory diagram of the circuit operation of Fig. 4, and Fig. 6 shows the slice level in Fig. 3 at the middle S.
FIG. 3 is an explanatory diagram of the operation of the circuit of FIG. 2 when the levels are matched; 1... Barcode display board, 2... Light source, 3... Light receiver, 4... Slice level separation amplifier, 5... AC signal oscillator, 6, 7
... Amplitude modulator, 8, 9 ... Slide back type detector, 10 ... Square wave conversion output circuit. Outside 1 Box Outside 2 Figure Husband 5 Figure Outside 4 Figure Age 5 Spotted O 6 Figure

Claims (1)

[Claims] 1 A barcode detection side that moves relative to a barcode display board, which is composed of long and short black and white bars in which binary code information to be transmitted is arranged alternately, detects the barcode by an optical method. As a device for detecting the widths of black bars and white bars, the detected electric signal of the bar that has been optically converted into electricity by a photoreceiver is connected to a black bar signal separation amplifier that sets the slice level of the black bar signal and a slicer of the white bar signal. Means for separately extracting signals corresponding to the black bar and white bar by sending the white bar signal to a level-set white bar signal separation amplifier, and modulating the output of a separately provided carrier wave oscillator using each of the extracted signals to obtain a pair of amplitudes. The means for obtaining a modulated wave and the pair of amplitude modulated waves described above are passed through separate slide-back type detectors, and the obtained outputs are summed and synthesized, and then converted into a square wave to generate black and white bar signals according to their widths. What is claimed is: 1. A barcode detection device comprising means for outputting a double current signal having a duration of time.