JP2720691B2 - Barcode reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved bar code reader.

[0002]

2. Description of the Related Art FIG. 5 is a perspective view showing the appearance of a bar code reader. As shown in the figure, a bar code reader 50 converts a bar code 52 attached to a product 51 into a light beam 53.
And reads the reflected light to recognize information such as a product name and a price. FIG. 6 is a perspective view showing a conventional optical system of a bar code reader. The light beam emitted from the laser tube 61 is narrowed by an imaging lens 62 having a predetermined focal length so as to be converged on a barcode 68, and further set to a predetermined beam shape by a slit 63. Then, the light is reflected by the plane mirror 64 and the polygon mirror 65 to irradiate the bar code 68. At this time, the polygon mirror 65
Is rotated as shown by the arrow in the figure, and the light beam is scanned on the bar code 68. The light beam reflected on the bar code 68 is reflected again by the polygon mirror 65 via a path shown by a dotted line. After being condensed by the condenser lens 66, the light is converted into an electric signal by the photodiode 67.

In order to improve the reading accuracy of the above-described bar code reading apparatus, it is necessary to increase the number of times of scanning of the light beam, which is usually dealt with by rotating the polygon mirror 65 at high speed. Further, a method has been proposed in which the light beam emitted from the laser tube 61 is divided into a plurality of light beams, and each light beam is scanned on a bar code, thereby substantially increasing the number of scans (Japanese Patent Application Laid-Open No. Sho 63).
-278187).

In FIG. 5, a bar code reader is shown.
If the distance between 50 and the product 51 is not appropriate, the light beam may not be focused on the barcode 52. For this reason, a method has been proposed in which a plurality of light beams having different condensing distances are switched and scanned, and a bar code is read by any one of the light beams to substantially widen a readable distance range (Japanese Patent Laid-Open No. Hei. 2-294888).

[0005]

However, when a plurality of light beams are used as described above, there are the following problems. That is, as shown in FIG.
The light beam incident in the direction of the arrow shown by the solid line is scattered on the bar code 68, and the light intensity spreads in the range indicated by the dotted line in the figure with the incident direction as the axis.
Return to 65. After being reflected by the polygon mirror 65, the light is condensed by the condenser lens 66 and detected by the photodiode 67. Therefore, when a plurality of light beams scan on the barcode 68 when the plurality of light beams approach each other on the barcode 68, the reflected beams interfere with each other and the reading accuracy is reduced.

It is known that the reading accuracy of a barcode is affected by the beam shape of a light beam. 3 and 4 are diagrams showing the relationship between the barcode and the beam shape. As shown in FIG. 3, when the bar 30 having a defective portion is scanned along a direction indicated by an arrow within a dotted line using the perfect circular light beam 31 and the elliptical light beam 32, the method using the elliptical light beam 32 is preferable. In general, the ratio of the defect area to the beam area becomes smaller as compared with the case where the perfect circular light beam 31 is used. Therefore, when a bar constituting a bar code has a missing portion, the use of the elliptical light beam 32 can increase the S / N ratio and increase the reading accuracy. On the other hand, when the bar code is scanned obliquely as shown in FIG. 4, the elliptical light beam 32 has a higher probability of being applied to both adjacent bars, so that the use of the perfect circular beam 31 makes the resolution higher. And high reading accuracy. However, conventionally, even when a plurality of light beams are used, there has been a problem that such a situation cannot be dealt with because each beam shape is the same.

[0007] Further, since the amount of information that can be recognized only by a normal bar code composed of white and black bars is limited, the second bar code having a sensitivity in the infrared region, for example, is superimposed on a normal bar code. It is convenient if a barcode is attached to a product and information can be read from the second barcode together with a normal barcode. However, in this case, it is necessary to separately prepare a barcode reading device that generates a light beam having sensitivity only to the second barcode, and there is a problem that operability is deteriorated.

Accordingly, it is an object of the present invention to improve reading performance by scanning a bar code so that a plurality of light beams do not interfere with each other.

[0009]

The object of the present invention is achieved by a light source (11, 15) for generating a plurality of light beams, and condensing means (12, 16) for condensing the plurality of light beams, respectively. Scanning means (14, 18, 19) for scanning the plurality of light beams at a predetermined distance or more from each other on a bar code, and shaping means (13, 1) for shaping the plurality of light beams into mutually different beam shapes.
7), detecting means (20 to detect a plurality of light beams reflected on the bar code, the bar code reading apparatus comprising the 21, 22, 23), or該整shaped means (13
, 17) shapes at least one light beam into a perfect circle
And at least one of the remaining light beams
This is achieved by the barcode reader described above, which is formed in an elliptical shape .

[0010]

[0011]

[0012]

According to the present invention, a plurality of light beams are transmitted from different beams.
Shape, and separate the light beams by a specified distance or more.
To scan, so that bar code defects and bar code
Different depending on the situation such as the relative position of the light beam
Reading with a light beam having a beam shape becomes possible.
This can suppress a decrease in reading accuracy. In the above configuration
And shape at least one of the plurality of light beams into a perfect circle
When scanning barcodes diagonally,
Lowering of the reading resolution can be prevented.
Form at least one of the light beams of
When scanning barcodes with missing parts
It is possible to prevent the S / N ratio from deteriorating.

[0013]

[0014]

FIG. 1 is a plan view of a main part of a bar code reader according to an embodiment of the present invention, and FIG. 2 is a sectional view of the bar code reader shown in FIG. A light beam L ₁ emitted from a laser tube 11 composed of a He-Ne gas laser or the like is converged by an imaging lens 12 having a predetermined focal length so as to be focused on a bar code 24, , For example, shaped into a perfect circle. Next, the light is reflected by the plane mirror 14 and enters the polygon mirror 19. Similarly, the light beam L emitted from the laser tube 15
₂ is converged by an imaging lens 16 having a predetermined focal length so as to converge on a bar code 24, and further shaped by a slit 17 into a predetermined beam shape, for example, a perfect circle. Next, the light is reflected by the plane mirror 18 and enters the polygon mirror 19. At this time, the light beams L ₁ and L ₂ are incident on the polygon mirror 19 at a distance a.

Light beam L reflected by polygon mirror 19
₁, L_TwoIs guided to the outside of the barcode reader and
Irradiate the gate 24. As can be seen in FIG. 2, the polygon mirror
A motor 26 is connected to the motor 19 via a rotary shaft 25.
Then, the polygon mirror 19 is moved by the motor 26 as shown by the arrow in FIG.
By rotating the light beam L as shown in FIG.₁, L _Two
Is repeatedly scanned on the bar code 24. Light beam
L₁, L_TwoIs a distance a on the polygon mirror 24
Reflected on the bar code 24,
Will scan different areas. On barcode 24
Reflected light beam L ₁, L_TwoIs the same as the incident light
It returns to the direction and enters the polygon mirror 19 again.
The light intensity distribution is shown by the dotted line in
It will be spread over the range. Spread in this way
Light beam L₁, L_TwoAre collected by condenser lenses 20 and 22, respectively.
After being illuminated, the light enters the photodiodes 21 and 23, where
Is converted to Light beam L₁, L_TwoIs on barcode 24
Measure the spread of the light intensity distribution when reflected
In advance, the spread light beam L₁, L_TwoIf they overlap each other
If the above-mentioned distance a is set so as not to be mixed with each other
The photodiodes 21 and 23 each emit a light beam L
₁, L_TwoOnly can be detected. Therefore, light bee
Mu L₁, L_TwoReading accuracy is low due to interference between
The bottom can be prevented.

By setting the focal lengths of the imaging lenses 12 and 16 to different values, the light beams L ₁ and L ₂ can be focused at different distances from the bar code reader. In this case, the distance range between the readable bar code reader and the product is widened, and the reading results by the light beams L ₁ and L ₂ do not interfere with each other, so that a decrease in reading accuracy can be prevented. .

Also, by setting the shape of one slit 13 to a perfect circle and the shape of the other slit 17 to an ellipse, the beam shapes of the light beams L ₁ and L ₂ are set to a perfect circle and an ellipse, respectively. can do. In this case, as described in the section of the related art, when the bar code is scanned obliquely, the light beam L ₁ having a perfect circular shape is obtained.
Makes it possible to prevent the deterioration of the resolution, also when scanning the bar code containing the partially missing bars, by the light beam L ₂ having an elliptical shape can prevent the deterioration of the S / N ratio further, It is also possible to prevent the reading accuracy from deteriorating due to the interference of the reading results by the light beams L ₁ and L ₂ .

In the embodiment described above, a plurality of light beams are emitted from different laser tubes. However, a single light beam is split by using a beam splitter to emit a plurality of light beams. The same result can be obtained even if the control is performed.

In the case where laser tubes having different oscillation wavelengths are used, for example, a He tube having an oscillation wavelength of 630 nm is used as the laser tube 11.
-Ne gas laser, oscillation wavelength 900n as laser tube 15
When using an infrared semiconductor laser m, to read the ordinary bar code consisting of white and black bars by the light beam L ₁ generated from a laser tube 11, whereas, the infrared radiation printed over the bar code bar codes with sensitivity, it can be read by the light beam L ₂ generated from a laser tube 15.

[0020]

As described above, according to the present invention, a defect of a bar code is obtained.
Accuracy due to the relative position between the light beam and the barcode
Therefore, it is useful for improving the performance of the bar code reader.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of the present invention;

FIG. 2 is an AA ′ sectional view showing an embodiment of the present invention;

FIG. 3 is a plan view (part 1) showing a relationship between a bar code and a beam shape;

FIG. 4 is a plan view (part 2) showing a relationship between a bar code and a beam shape;

FIG. 5 is a perspective view showing the external appearance of a barcode reader;

FIG. 6 is a perspective view showing an optical system of a conventional bar code reader.

[Explanation of symbols]

11, 15, 61 laser tube, 12, 16, 62 imaging lens, 19, 65 polygon mirror, 13, 17,
63 slits, 20, 22, 66 condenser lens, 1
4, 18, 64 flat lens, 21, 23, 67 photodiode, 32 elliptical light beam, 24, 52, 68 barcode, 50 barcode reader, 30 bar,
51 products, 31 perfect circular light beam, 53 light beam,

Claims (2)

(57) [Claims] 1. A light source for generating a plurality of light beams, a condensing means for condensing the plurality of light beams, and a scanning means for scanning the plurality of light beams at a predetermined distance or more from a bar code. And shaping the plurality of light beams into mutually different beam shapes.
A bar code reader , comprising: a shaping unit; and a detecting unit that detects a plurality of light beams reflected on the bar code. 2. The shaping means includes at least one light beam.
Shape the beam into a perfect circle and use at least
The bar code reader according to claim 1, wherein one light beam is formed in an elliptical shape .