JPH01236386A - Bar code reading system - Google Patents

Abstract

PURPOSE:To prevent the occurrence of erroneous reading without making data ineffective by comparing successively inputted two pieces of read data with flags at a discriminating part, outputting the data when the two pieces of data are coincident, and erasing one piece of data in which the flag to indicate the occurrence of mode hopping is raised when the two pieces of data are inconsistent. CONSTITUTION:A semiconductor laser oscillating part 10, a mode hopping detecting part 11, a signal detecting part 12, a bar code decoding part 13, and a discriminating part 14 are provided for the title system. Further, the mode hopping is detected by the mode hopping detecting part 11 of an oscillator for a semiconductor laser, the flag is raised in the read data at that time by the detected output, the data are compared in operations for discriminating whether the plural data are coincident or not, the data are outputted as the read data when both the data are coincident, and the data in which the flag is raised are erased when both the data are inconsistent. Thus, the occurrence of the erroneous reading can be prevented without making the data at that time ineffective immediately even when the mode hopping occurs in the oscillated wavelength of the semiconductor laser.

Description

[Detailed description of the invention] [+1! Regarding the barcode reading method, in which barcodes printed or attached to the packaging of various products are read using a hollowwind reader, even if a mode hop occurs in the oscillation wavelength of the semiconductor laser, the data at that time is immediately invalidated. The aim is to provide a barcode reading method that can prevent the occurrence of erroneous readings without having to do so. A detection section is provided, and the bar code decoding section decodes the output from the signal construction section into read data, and at the same time sets a flag section according to the output state of the mode hop detection section. The read data with a flag is held and the comparison unit compares the two, and if they match, the data is output, and if they do not match, the data flagged as mode hop occurrence is erased.

[Industrial Field of Application] The present invention relates to a barcode reading system for reading barcodes printed on or attached to packages of various articles using a Hollowwind type reading device.

In recent years, there has been an increase in the number of stores that perform calculations by attaching barcodes to the packaging of various goods and reading them at payment counters. In that case, the fixed Holowind method (
A barcode reading device is used in which a barcode is scanned through a hologram window, and a helium-neon laser tube has conventionally been widely used as a light source for reading. However, since devices using helium-neon laser tubes are large in size, there has been a problem in that they cannot meet recent demands from users for miniaturization. To improve this, a semiconductor laser that can be used for barcode reading has recently been developed, but semiconductor lasers also have problems with their characteristics, and a solution to these problems is desired.

[Prior Art] FIG. 3 shows a schematic configuration diagram of a conventional fixed hollow window type barcode reading device.

To explain this configuration, a laser beam generated from a helium-neon tube laser oscillator 43 is reflected by a pentagonal rotating polygon mirror 44 and proceeds to a three-sided mirror 42, where it is reflected to a bottom mirror 45 and from there to a hollow window 41. It is incident, diffracted by the hologram, reaches the barcode label (or product packaging), and scans the barcode. The reflected light from the barcode label passes through the hollow window 41 and returns in the opposite direction along the same path as the emitted light, and is reflected at the next concave mirror 46 toward the detector 47.

The detector detects the reflected light of the laser focused by the auxiliary lens and supplies an output to the reading circuit 48.

The hollow window is provided in three directions, and laser light scans are repeated in each direction in sequence depending on the angle of rotation of the rotating polygon mirror 44, and the cycle of these scans is about 100 times per second.

In the above conventional configuration, laser light is generated by a helium/fluoron tube, but since the device becomes large, it has been desired to replace this with a semiconductor laser. However, according to the conventional semiconductor laser, the oscillation The wavelength is approximately 780 nm (nanometers), which is the wavelength of a helium neon tube (633 nm).
For example, some barcodes printed in blue color could not be read because they were longer than m) (
When reading at long wavelengths, the reflectance of blue and white becomes about the same, making it impossible to read).

However, recently, semiconductor lasers with short wavelengths (650 to 6,800 m) have been developed, and such semiconductor lasers can be used to read barcodes, so miniaturization of barcode reading devices is being considered.

[Problems to be Solved by the Invention] Regarding the mode hop that is a problem when reading barcodes using the hollow wind method using the short wavelength semiconductor laser described above, the effect of the mode hop of the semiconductor laser shown in FIG. This will be explained with reference to explanatory diagrams.

As shown in Figure 4 (a), the oscillation wavelength of a semiconductor laser hardly changes with temperature changes within a certain temperature range, but when the temperature exceeds a certain temperature, the oscillation wavelength changes discontinuously. Occurs stepwise at multiple temperatures. This phenomenon is called a mode hop, and is an inherent drawback of semiconductor lasers.

On the other hand, holograms have the property of diffracting incident light, but the diffraction angle changes depending on the wavelength of the incident light, which adversely affects barcode reading.

Specifically, in the case of the Hollowwind method, the opening in Figure 4.

As shown in Figure 3, a laser beam with wavelength λ1 from a light source enters a hologram (hollow window in Figure 3), is diffracted within the hologram, and when the light is emitted at an angle as shown in Figure 1), the temperature changes. Therefore, the oscillation wavelength of the semiconductor laser is λ2 (
When λ1<λ2), the light emitted from the hologram changes as shown in (2). If such a change occurs during scanning of a bar code, beam interruption occurs due to a mode hop as shown in FIG. 4C.

Due to this interruption of the beam, the reading width fluctuates as shown in FIG. 4-2. In the case of this figure, the white code may be mistakenly read as being longer by Δβ than the original white reading width, which may cause so-called misreading. Misreading of this barcode is a problem related to trust when used in stores.

However, as a means to prevent mode hops from occurring, there is a conventional method of controlling the temperature of the semiconductor laser itself using a Peltier element to keep it constant.
There is a problem in that the equipment becomes expensive and at the same time the equipment becomes larger to control it.

SUMMARY OF THE INVENTION An object of the present invention is to provide a barcode reading method that can immediately invalidate data even if a mode hop occurs in the oscillation wavelength of a semiconductor laser, thereby preventing the occurrence of erroneous reading.

[Means to solve the problem] FIG. 1 shows a basic configuration diagram of the present invention.

In FIG. 1, 10 represents a semiconductor laser oscillation section, 11 represents a mode hop detection section, 12 represents a signal detection section, 13 represents a barcode decoding section, and 14 represents a discrimination section.

The present invention detects mode hops using the mode hop detection section of the oscillator of a semiconductor laser, sets a flag on the read data at that time based on the detection output, compares the data in an operation to determine multiple matches, and when the two match, The data is output as read data, and if there is a mismatch, the flagged data is erased.

[Operation] A laser beam for reading is emitted from the semiconductor laser oscillation section 10, and on the other hand, a mode hop phenomenon of the oscillation wavelength is detected in the mode hop detection section 11. The emitted laser beam scans a bar code using a scanner configured as shown in FIG. 1, and the reflected light is input to the signal detection section 12 as received light.

The signal amplified and binarized by the signal detection section 12 and output is input to the barcode decoding section 13 and converted into a data code. This barcode decoding section 13 is provided with a flag section 131, and when a mode hop detection section detects a mode hop, a flag is set in the flag section 131 according to its output.

Next, the flagged data from the barcode decoding section 13 is input to the discriminating section 14. The determining unit 14 generates an output for the first time when the data read twice on the barcode matches, and alternately sets the two consecutively input data in the first storage unit 141 and the second storage unit 143, respectively. . However, if there is a storage section that is in an empty state (reset state), it is set in that storage section.

The comparing unit 142 of the determining unit 14 compares the data parts (
(excluding the flag), and if they match, the current data is generated as a discrimination output, and if they do not match, the contents of the memory section with the flag set are cleared (reset) and the next read data is The data is stored in the free storage section and the next comparison is performed.

[Example] A configuration diagram of an embodiment of the present invention is shown in Figure 2 (al), a specific configuration diagram of the mode hop detection circuit is shown in Figure 2 tbl, and a diagram explaining the operation of the comparison section is shown in Figure 2 fcl. .

In FIG. 2 tal, 20 is a mode hop detection circuit;
21 is a barcode signal detection circuit, 22 is an A/D conversion circuit, 23 is a decoder, 24 is a storage circuit, 25 is a comparison circuit,
26 represents an output circuit.

The specific configuration of the mode hop detection circuit 20 is shown in FIG.
The contents are explained below.

This circuit is based on the principle of detecting noise that occurs when mode hop occurs in a laser diode. That is, the laser light oscillated from the laser diode is output for reading, is detected by a photodiode sealed together with the laser diode, is converted into an electrical signal, and is sent to the amplifier 3.
1 (indicated by Amp), the DC component is cut off by a capacitor, and only the AC signal component (noise component) is supplied to comparison units 32 and 33. If the output signal of the photodiode is between the preset reference voltage values ('Vr, -V,) in each comparison section, no output signal will be generated (no noise due to mode hops). ), “1” if outside of those levels.
A signal is generated and provides the mode hop detection output to the outside via the OR circuit 34.

Next, to explain the operation of the configuration shown in FIG. 2(a), the barcode signal detection circuit 21 detects the received optical signal, amplifies it, and sends it to the A/D conversion circuit 22. 22 converts the input signal into a binary signal and sends it to the next decoder 2.
Output to 3. The decoder 23 received 241! from the A/D conversion circuit 22! Decode the signal using the same technology as before, convert it into numerical data, and store it in the data register.
Set the data corresponding to one barcode.

On the other hand, the mode hop detection circuit 20 detects a mode hop using the above-described configuration, and its output is supplied to the flag register 231. If a mode hop occurs while one barcode data is being read, "1" is sent. Otherwise, it remains in the "0" state.

Every time one barcode data is generated in the decoder 23, the predetermined registers 241 and 24 of the next storage circuit 24 are
Flags and data are stored in one of the two. Two registers 241 and 242 of this storage circuit 24 store previous data (results of reading the same barcode) and current data.

In the comparison circuit 25, registers 241 and 2 in the storage circuit 24
The data stored in 42 is taken out and compared without the flag. This situation is shown in the operation explanatory diagram of the comparison section of the second [g (C1). In this example, the data of ■ and the data of
6, and if they do not match, the flag is checked and a signal is sent to the storage circuit 24 to erase the data for which 1 is set. After the discrepancy, the data set in the storage circuit (2) and the data (2) are compared and the same processing is performed.

In the case of a read operation based on this multiple match, the data when a mode hop is detected is not immediately invalidated, but is compared as is, and if there is a match, a read output is generated, so the minimum number of data is 2. It can be read only with the data (when the data match).

FIG. 2 Fdl shows a diagram of the relationship between barcode symbols and beam angles. The i is a normal barcode symbol,
This is a case where the code line is relatively long, and the beam angle (the angle at which the laser beam can see the entire barcode) is a fairly large angle α. On the other hand, recently short symbols called truncated symbols have been used for reasons such as improving appearance, and in this case the beam angle β is approximately 60 degrees, which is a very narrow angle. .

When scanning (beam scanning) a fixed Holowind method for such symbols, the number of times the entire barcode is read in one scan (the third
As explained in the figure, the number of scans (repeated scanning is performed in one reading operation) is quite large in the case of A, but it decreases in the case of the mouth due to the angle of the beam.
~Sometimes it can only be read 3 times. At that time, even if a mode hop occurs, by generating a matching output at least twice as described above, the possibility of re-reading (moving the item for another reading) is reduced. can do.

[Effects of the Invention] According to the present invention, it is possible to prevent misreading of a bar code due to mode hopping of a semiconductor laser using a small circuit, without using a Peltier element which makes the device large and expensive.

Furthermore, it is possible to achieve positive and blind reading for any barcode symbol without reducing the reading rate.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of the present invention, FIG. 2 tal is a configuration diagram of an embodiment of the present invention, FIG. Explanatory diagram,
FIG. 2 (dl is an explanatory diagram of the relationship between barcode symbols and beam angles, FIG. 3 is a schematic diagram of a conventional fixed barcode reader, and FIG. 4 is an explanatory diagram of the mode hop effect of a semiconductor laser. In FIG. 1, 10: Semiconductor laser oscillation section 11: Mode hop detection section 12: Signal detection section 13: Barcode decoding section 14: Discrimination section

Claims (1)

[Claims] In a barcode reading method that uses a semiconductor laser as a light source and uses a hologram for laser beam scanning, a mode hop detection section (10) is provided in the oscillation section (10) of the semiconductor laser.
11) is provided, and the output from the signal detection section (12) is sent to the barcode decoding section (12).
In step 3), at the same time as the read data is decoded, a flag section (131) is set according to the output state of the mode hop detection section (11), and the two flagged read data sequentially inputted in the discriminator (14) are A barcode reading method is characterized in that the data is held and compared by a comparison unit (142), and if they match, the data is output, and if they do not match, the flagged data is erased.