JP2010049110A - Barcode reader and method of forming multifocus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a barcode reader in which a plurality of focal points are obtained at the same time and the cost of the equipment is reduced. <P>SOLUTION: The barcode reader includes: a laser beam source 11a which emits laser beam; deflection and separation means 13 to 16, which separate the laser beam into a plurality of polarized light beams, transmit the light beams so that the optical path varies for each separated polarized light beam, and output the respective polarized light beams by synthesizing on substantially the same axis; and a deflection element 19 which emits a scan beam, including the respective polarized light beams to the barcode and scans it. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical bar code reader using laser light and a multi-focus forming method realized in the bar code reader, and more particularly to an autofocus laser bar code reader for logistics requiring a wide reading depth ( The present invention relates to a barcode reader useful as an AFLBR (Auto Focus Laser Bar code Reader) and a multi-focus formation method.

A bar code reader refers to a device for optically detecting a bar code and converting it into a specific character by analyzing the pattern of the bar and space constituting the bar code.
Light sources for reading barcodes include, for example, LEDs (Light Emitting Diodes), CCDs (Charge Coupled Devices), and lasers. Among them, lasers can be read remotely, and the reading width must be wide. And has a high reading rate.

  However, since the laser light is condensed by the lens, there is a focal point and the focal length is constant. As a result, the distance from the object to which the barcode is attached fluctuates, so that there is a problem that the light beam incident on the barcode cannot be narrowed and reading is erroneous.

Therefore, in order to solve the problem, a technique for making a plurality of focal lengths has been proposed.
For example, a light beam output unit that outputs a linearly polarized beam, a polarization direction changing unit that changes the polarization direction of the linearly polarized beam in accordance with an external signal, and a beam that emits a linearly polarized beam at a predetermined angle that varies depending on the polarization direction There has been proposed a technique including an angle changing unit and a diffractive unit having a diffractive surface that focuses and scans the linearly polarized beam at different focal positions according to the incident angle of the linearly polarized beam (for example, a patent). Reference 1).
As a result, a plurality of focal lengths can be obtained, so that even when the position of the object fluctuates, the light beam is scanned at the focal position corresponding to the object position, and good bar code reading is always possible.
Japanese Patent Laid-Open No. 02-056520

However, the technique (light beam scanning device) described in Patent Document 1 described above has the following problems.
For example, the apparatus, although the two focal points of F _B based on F _A and P-polarized light based on the S-polarized light can be obtained, depending on the presence or absence of the voltage applied in the polarization direction changing means (liquid crystal panel) of the S polarized light and P-polarized light Since either one is selected, two focal points cannot be obtained at the same time. For this reason, the time resolution was low.
In addition, the formation of the diffracting means (hologram plate) is not easy and is special, leading to high cost of the apparatus.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a barcode reader and a multi-focus forming method capable of obtaining a plurality of focal points at the same time and reducing the apparatus cost. And

  In order to achieve this object, the barcode reader of the present invention separates a laser light source that emits laser light, and the laser light into a plurality of polarized lights, and propagates optical paths having different lengths for each of the separated polarized lights. The configuration includes polarization separating means for combining and outputting polarized lights on the same axis, and a deflecting element for scanning a scan beam including each polarized light against a barcode.

  Further, the multi-focus formation method of the present invention emits laser light, separates the laser light into a plurality of polarized lights, propagates each polarized light with different optical path lengths, synthesizes the polarized lights on the same axis and outputs them, This is a method in which a scanning beam including each polarized light is applied to a barcode and scanned.

According to the barcode reader and the multi-focus formation method of the present invention, the laser light is polarized and separated, and each polarized light passes through optical paths having different lengths. Multiple focal points can be obtained at different positions on the same axis at the same time. Thereby, time resolution can be improved.
In addition, since a part requiring special processing such as the diffraction means (hologram plate) described in Patent Document 1 is not required, the apparatus cost can be reduced.

  Hereinafter, preferred embodiments of a barcode reader and a multifocus forming method according to the present invention will be described with reference to the drawings.

[First embodiment]
First, a first embodiment of the barcode reader and multifocus forming method of the present invention will be described with reference to FIG.
FIG. 2 is a block diagram showing the configuration of the barcode reader of this embodiment.

(Barcode reader)
As shown in the figure, the barcode reader 10-1 includes a laser light source 11a, a lens 12a, polarizing beam splitters 13 and 16, total reflection mirrors 14 and 15, quarter wavelength plates 17 and 20, A perforated mirror 18, a deflection element 19, a collector lens 21, a polarization beam splitter 22, lenses 23 and 25, and optical sensors 24 and 26 are provided.

Here, the laser light source 11a is a small laser light source such as a semiconductor laser, and emits red laser light having a wavelength of, for example, 635 nm. This laser light is then propagated on the barcode so as to be focused to a desired beam diameter.
The wavelength of the laser beam may be any wavelength as long as the barcode can be read, and can be arbitrarily selected.
The lens 12a condenses the laser light emitted from the laser light source 11a.

A polarization beam splitter (separator) 13 separates the laser light into P-polarized light and S-polarized light, and outputs them in different directions. That is, the P-polarized light is output straight as it is with respect to the incident light, and the S-polarized light is output in a direction perpendicular to the P-polarized light.
Here, the laser light (propagation beam) emitted from the laser light source 11a is linearly polarized light. The polarization plane of the polarization beam splitter 13 is provided with an inclination of 45 degrees with respect to the incident direction of the laser beam so that the laser beam is equally divided into P polarization and S polarization by the polarization beam splitter 13.
The P-polarized light and S-polarized light separated by the polarization beam splitter 13 pass through different optical paths.

Total reflection mirrors (reflectors) 14 and 15 reflect the S-polarized light from the polarization beam splitter 13 and send it to the polarization beam splitter 16.
The polarization beam splitter (polarization synthesizer) 16 transmits the P-polarized light from the polarization beam splitter 13. The polarization beam splitter 16 reflects the S-polarized light from the total reflection mirror 15 and sends it to the quarter wavelength plate 17 coaxially or substantially coaxially with the P-polarized light.
Here, the S-polarized light and the P-polarized light that have reached the polarizing beam splitter 16 have different optical path lengths. That is, the optical path through which the S-polarized light has passed is longer than the optical path of the P-polarized light by the reciprocating distance from the polarizing beam splitters 13 and 16 to the total reflection mirrors 14 and 15. For this reason, as shown in FIG. 2, in the scan beam, the S-polarized light condensing point is positioned closer to the front (closer to the barcode reader 10-1) than the P-polarized light condensing point (focus). Therefore, double focus can be realized.
In the present embodiment, the polarization beam splitters 13 and 16 and the total reflection mirrors 14 and 15 are collectively referred to as “polarization separating means”.

The quarter-wave plate 17 converts P-polarized light and S-polarized light whose polarizations are orthogonal to each other into clockwise and counterclockwise circularly polarized light.
The perforated mirror 18 allows S-polarized light and P-polarized light from the quarter-wave plate 17 to pass through. The perforated mirror 18 reflects the scan beam from the deflection element 19 and sends it to a light receiving system (described later).

The deflecting element 19 scans the barcode with the S-polarized light and the P-polarized circularly polarized light beams that have passed through the perforated mirror 18. That is, the barcode is scanned with a scanning beam including clockwise and counterclockwise circularly polarized light. Then, the reflected light from the barcode is reflected and sent to the perforated mirror 18.
For example, a polygon mirror, a galvanometer mirror, an acousto-optic deflection element, a MEMS mirror, or the like can be used as the deflection element 19.

The quarter-wave plate 20 converts the reflected light from the perforated mirror 18 into P and S linearly polarized light.
The collector lens 21 collects S-polarized light and P-polarized light from the quarter-wave plate 20.
The polarization beam splitter (light receiving / separating device) 22 separates the polarized light from the collector lens 21 into P-polarized light and S-polarized light and outputs the separated light.

The lens 23 condenses the P-polarized light from the polarization beam splitter 22.
The lens 25 condenses the S-polarized light from the polarization beam splitter 22.
The optical sensor 24 receives P-polarized light from the lens 23 and converts it into an electrical signal.
The optical sensor 26 receives S-polarized light from the lens 25 and converts it into an electrical signal.
In the present embodiment, the quarter wavelength plate 20 to the optical sensor 26 are referred to as “light receiving system”.

(Multi-focus formation method)
Next, the operation of the barcode reader of this embodiment (multifocus formation method) will be described with reference to FIG.
Laser light emitted from the laser light source 11 a is collected by the lens 12 a and is equally divided into P-polarized light and S-polarized light by the polarization beam splitter 13.
When the S-polarized light is output from the polarization beam splitter 13, it is folded (reflected) by the total reflection mirrors 14 and 15 and sent to the polarization beam splitter 16.
On the other hand, the P-polarized light passes through the polarizing beam splitter 13 and further passes through the polarizing beam splitter 16. In this polarization beam splitter 16, S-polarized light is synthesized coaxially or substantially coaxially with P-polarized light and output.
Thus, since the S-polarized light path is longer than the P-polarized light path, the S-polarized light condensing point is closer to the P-polarized light condensing point in the scan beam (the one closer to the barcode reader 10-1). Will come to be located.

The P-polarized light and S-polarized light transmitted or reflected by the polarizing beam splitter 16 pass through the perforated mirror 18 and reach the deflecting element 19. The deflecting element 19 is reflected in the direction of the barcode and scans the barcode as a scan beam.
When the bar code is scanned, the scan beam returns as reflected light, is reflected by the deflecting element 19, is reflected by the perforated mirror 18, and is guided to the light receiving system.

In the light receiving system, the reflected light is converted into P and S linearly polarized light by the quarter wavelength plate 20, condensed by the collector lens 21, and separated into P polarized light and S polarized light by the polarization beam splitter 22.
The P-polarized light passes through the lens 23, is received by the optical sensor 24, and is converted into an electrical signal.
On the other hand, the S-polarized light passes through the lens 25, is received by the optical sensor 26, and is converted into an electric signal.

(Optical path difference between polarization and multiple focal points)
In the barcode reader 10-1 of this embodiment, an optical path difference is generated between the S-polarized light and the P-polarized light separated by the polarizing beam splitter 13.
Specifically, an optical path difference corresponding to the reciprocal distance between the polarizing beam splitters 13 and 16 and the total reflection mirrors (folding mirrors) 14 and 15 is generated. For this reason, the polarized light condensing point (focal point) included in the scan beam irradiated to the barcode is, as shown in FIG. The condensing point of P-polarized light comes to be located on the back side.
In the present embodiment, the light is converted into circularly polarized light having a different turning direction through the ¼ wavelength plate 17 (in a configuration without the ¼ wavelength plate 17, it is separated as linearly polarized light).

Further, as shown in the figure, both the original S-polarized light and the original P-polarized light beam are shifted so that the focused spot diameter range in which the barcode is read, that is, the focal depth overlaps (partially overlaps). The optical path difference is determined.
Since both polarized beams reflected by the barcode are separated by the polarization beam splitter 22 of the light receiving system, the barcode information at the respective focal depths can be detected with a high S / N ratio.

  As described above, according to the barcode reader and the multifocus forming method of the present embodiment, the laser light is polarized and separated, and each polarization passes through optical paths having different lengths, and the polarized lights are combined on the same axis or substantially on the same axis. Therefore, the focal point corresponding to each polarized light can be obtained at different positions (double focus). As a result, the reading range (depth) of the barcode reader can be increased, and multi-focusing can be performed while ensuring spatial resolution, temporal resolution, and S / N ratio.

Further, since the separation by polarization is used as the multi-focus on the irradiation side, different focus can be detected at the same time even if they are on the same axis, the light receiving efficiency is good, and S / N can be secured.
Further, since the S-polarized light and the P-polarized light are respectively passed through optical paths having different lengths, and are combined on the same axis or substantially on the same axis, the S-polarized light focus and the P-polarized light focus are combined on one scan beam. Can be formed. For this reason, unlike the focal points F _A and F _B described in Patent Document 1 described above, the positions of the focal points with respect to the barcode reader main body are not shifted from each other, and the barcode reading range becomes clearer. A practical barcode reader can be provided.

In addition, since the optical components are shared between the S-polarized light and the P-polarized light, the cost of the apparatus can be suppressed.
In addition, since a part that requires special processing such as the hologram plate described in Patent Document 1 is not required, the cost of the apparatus can be reduced.

[Second Embodiment]
Next, a second embodiment of the barcode reader and multi-focus formation method of the present invention will be described with reference to FIG.
FIG. 2 is a block diagram showing the configuration of the barcode reader of this embodiment.
This embodiment differs from the first embodiment in the number of laser light sources and the number of condensing points in the scan beam. That is, in the first embodiment, there is one laser light source and two condensing points, whereas in this embodiment, there are two laser light sources and four condensing points. . Other components are the same as those in the first embodiment.
Therefore, in FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

(Barcode reader)
As shown in FIG. 3, the barcode reader 10-2 of this embodiment includes laser light sources 11a and 11b, lenses 12a and 12b, polarization beam splitters 13 and 16, total reflection mirrors 14 and 15, 4 wavelength plates 17 and 20, a perforated mirror 18, a deflection element 19, a collector lens 21, a polarization beam splitter 22, lenses 23 and 25, optical sensors 24 and 26, and a half mirror 27 are provided. Yes.

Here, the laser light source 11b has the same function as the laser light source 11a and emits laser light.
The laser light source 11a and the laser light source 11b can emit laser light so that the emission times do not overlap each other.
The lens 12b condenses the laser light emitted from the laser light source 11b.
The half mirror (laser beam synthesizer) 27 synthesizes the laser beam from the laser light source 11b and the laser beam from the laser light source 11a on the same axis or substantially on the same axis and outputs it.

(Multi-focus formation method)
Next, the operation of the barcode reader of this embodiment (multifocus formation method) will be described with reference to FIG.
Laser light a emitted from the laser light source 11 a is collected by the lens 12 a, passes through the half mirror 27, and reaches the polarization beam splitter 13. Further, the laser beam b emitted from the laser light source 11 b is condensed by the lens 12 b and reaches the half mirror 27. Here, the laser beam b is synthesized and output coaxially or substantially coaxially with the laser beam a by the half mirror 27.

The laser beams a and b incident on the polarization beam splitter 13 are equally divided into P-polarized light and S-polarized light.
When the S-polarized light is output from the polarization beam splitter 13, it is folded (reflected) by the total reflection mirrors 14 and 15 and sent to the polarization beam splitter 16. On the other hand, the P-polarized light passes through the polarizing beam splitter 13 and further passes through the polarizing beam splitter 16. In this polarization beam splitter 16, S-polarized light is synthesized coaxially or substantially coaxially with P-polarized light and output.
The polarization beam splitter 16 and the subsequent steps are the same as the multifocus forming method of the first embodiment.

(Multiple focal points and expanded reading range)
Next, a plurality of focal points formed by the barcode reader of this embodiment and expansion of the reading range will be described with reference to FIGS. 4 (i), (ii), and FIG.
FIG. 4I is a diagram showing a focal position based on S and P polarized light of the laser light a emitted from the laser light source 11a. FIG. 4 (ii) is a diagram showing a focal position based on S and P polarized light of the laser light b emitted from the laser light source 11b. FIG. 5 is a diagram showing focal positions based on the S and P polarizations of the laser light a and the laser light b, respectively.

In the first embodiment, two focal positions can be obtained based on the S-polarized light and the P-polarized light of the laser light a.
However, when the reflected light from the bar code does not preserve the polarization state well, it is considered that the polarization separation ratio decreases, and the S / N ratio deteriorates particularly in the vicinity of overlapping.
Therefore, as shown in FIG. 4 (i), the double focus based on the polarization separation is installed in a state where the focal depths are separated so as not to overlap.

On the other hand, in the present embodiment, a laser light source 11b is added to fill the gap between the polarized lights.
The focal position based on the S and P polarizations of the laser beam b emitted from the laser light source 11b is shown in FIG.
Here, comparing (i) and (ii) in the figure, the focal point based on the laser beam a and the focal point based on the laser beam b are in positions that do not overlap each other.
And the state which combined those focuss is shown in FIG.
As shown in the figure, the quad focus (four focal points) is realized in a state where the focal point based on the laser beam a and the focal point based on the laser beam b do not overlap each other. That is, with respect to one laser light source 11, double focus is realized by polarization separation, and quad focus is realized by providing two laser light sources 11.

  At this time, the laser light source 11a and the laser light source 11b blink alternately in synchronization with the scan. For example, when the deflection element 19 is a polygon mirror, the laser light sources 11a and 11b are switched for each reflection surface. Specifically, for example, as shown in FIG. 6, the laser beam a from the laser light source 11a is reflected by the surface 1 of the polygon mirror, the laser beam b from the laser light source 11b is reflected by the surface 2, and the surface 3 Then, the laser beam a is reflected, the laser beam b is reflected by the surface 4, the laser beam a is reflected by the surface 5, the laser beam b is reflected by the next surface 1, and these are repeated.

When each focal point is arranged as shown in FIG. 5, since there is no overlap within the focal depth between the polarized lights, the optical power density becomes low with one of the beams spread. From this, the influence on the S / N ratio is mitigated.
Since the laser light source 11a and the laser light source 11b are temporally separated for alternate blinking, detection with a high S / N ratio is possible within a quadruple depth of focus.

4 (i) and (ii), in order to make the focal position based on the laser light source 11a different from the focal position based on the laser light source 11b, as shown in FIG. The optical path lengths between the laser light sources 11a and 11b and the half mirror 27 may be made different.
That is, by shortening the optical path length between the laser light source 11 and the half mirror 27 (in the case of the laser light source 11a shown in FIG. 7), the barcode reading range (focusing surface) is positioned far from the barcode reader 10. Can be. On the other hand, by increasing the optical path length between the laser light source 11 and the half mirror 27 (in the case of the laser light source 11b shown in FIG. 7), the barcode reading range (focusing surface) is a position close to the barcode reader 10. Can be.

As described above, according to the barcode reader and the multi-focus formation method of the present embodiment, by combining polarization separation and time axis separation, the object to be read by multi-focus without significantly increasing the scan interval. Can be scanned.
In addition, since it is not necessary to have a plurality of the same optical systems, an increase in the cost of the apparatus can be suppressed.

Furthermore, the present invention can exert an advantageous effect even when compared with the multi-focus technique already disclosed.
For example, as a known technique, there has been a technique that realizes pseudo-autofocusing as multi-focus on the irradiation side. However, this technique has a single focus range, and cannot simultaneously read barcodes at a plurality of focus positions. In addition, focus switching time is required, and the mechanical life of focus switching has become a problem in apparatus maintenance. Furthermore, it was necessary to prepare a separate mechanism for measuring the distance to the barcode.
In contrast, according to the present invention, since there are a plurality of in-focus ranges, barcodes at a plurality of focus positions can be read simultaneously. In addition, the focus switching time is unnecessary, and there is no problem of the mechanical life of the focus switching. Furthermore, a mechanism for measuring the distance to the barcode is not necessary. For this reason, it is effective for increasing the conveying speed of the high-speed logistics sorting conveyor and for narrowing the intervals of the items to be sorted.

  Further, it is not necessary to use a plurality of optical systems with different focus, and the cost can be reduced. Also, in the case where scanning is performed by separating each focus temporally in order to ensure the S / N ratio, scanning at a certain focal position is thinned out by switching, and the scanning interval becomes longer due to the multi-ization. That was not practical. When this interval is large, the conveyance speed is suppressed or the reading rate is lowered, and the basic performance is lowered.

Furthermore, various excellent effects can be obtained when the barcode reader of the present invention is used for physical distribution.
For example, when the barcode reader of the present invention is used as a fixed barcode reader and a barcode attached to a hand-held baggage is to be read, even if the hand-held baggage is not brought close to the distance of the barcode reader, the A barcode can be read. This allows humans to read barcodes in the most easy state for handling and input passing information / sorting information regardless of height difference, physique difference, luggage shape / size, label height, etc. be able to.

Furthermore, by ensuring a sufficient reading depth, a height sensor becomes unnecessary.
In addition, by eliminating the focusing time, high-speed conveyance is possible, and a higher-density arrangement of the sorting objects can be realized.
Furthermore, by having a sufficient focus range, focus adjustment and confirmation at the position is not necessary, and installation, immediate operation is possible, and it is easy to start up the position and handle maintenance and maintenance. To provide a system.

  Another object of the present invention is to provide a distribution system that can simplify a device / system configuration, simplify installation / operation, and improve operability because it can consolidate a small number of barcode readers that have conventionally been required. .

The preferred embodiments of the barcode reader and multifocus formation method of the present invention have been described above, but the barcode reader and multifocus formation method according to the present invention are not limited to the above-described embodiments, and the present invention is not limited thereto. It goes without saying that various modifications can be made within the range described above.
For example, in the first embodiment described above, the configuration in which one laser light source is provided and in the second embodiment has been described, the laser light source is not limited to one or two, but an arbitrary number. Can be provided. Here, if three laser light sources are provided, the depth of focus is multiplied by six. If four laser light sources are provided, the magnification is 8 times.

  In each of the above-described embodiments, circular polarization is used to relax the polarization characteristics of the measurement object. However, it is possible to implement linear polarization with a configuration excluding the quarter-wave plates 9 and 16. . In this case, since two wave plates are eliminated, an inexpensive configuration can be expected.

  Since the present invention relates to a double focus of a barcode reader, the present invention can be used for an apparatus or a device that outputs a laser beam.

It is a block diagram which shows the structure of the barcode reader in 1st embodiment of this invention. It is a figure which shows the position of the focus in the scan beam output from the barcode reader of 1st embodiment. It is a block diagram which shows the structure of the barcode reader in 2nd embodiment of this invention. It is a figure which shows the position of the focus in the scan beam output from the barcode reader of 2nd embodiment, Comprising: (i) is the focus of the laser beam a emitted from the laser light source 11a based on the S polarization and P polarization. FIG. 2B is a diagram illustrating the position of the focal point based on the S-polarized light and the P-polarized light of the laser light b emitted from the laser light source 11b. It is a figure which shows the position of the focus in the scan beam output from the barcode reader of 2nd embodiment. It is a table | surface shown about switching to the laser light source with respect to the reflective surface of a deflection | deviation element (polygon mirror). It is a figure which shows the relationship between the optical path length between laser light source 11a, 11b and the half mirror in the barcode reader of 2nd embodiment, and the reading range (focusing surface) of barcode.

Explanation of symbols

10 Barcode reader 11a, 11b Laser light source 12a, 12b Lens 13, 16 Polarizing beam splitter 14, 15 Total reflection mirror 19 Deflection element 22 Polarizing beam splitter 24, 26 Optical sensor 27 Half mirror

Claims (7)

A laser light source for emitting laser light;
Polarization separation means for separating the laser light into a plurality of polarized lights, propagating optical paths having different lengths for each of the separated polarized lights, and combining and outputting the polarized lights on the same axis;
A bar code reader, comprising: a deflection element that scans a bar code with a scan beam including each polarized light. The polarized light separating means is
A separator that separates the laser light into a plurality of polarized light beams and outputs them in different directions;
A reflector that reflects a portion of the polarized light output from the separator;
The bar code reader according to claim 1, further comprising a polarization beam combiner that coaxially combines and outputs the polarized light from the separator and the polarized light from the reflector. A plurality of laser light sources for emitting laser light;
The bar code reader according to claim 1, further comprising: a laser beam combiner that synthesizes and outputs the laser beams from the laser light sources so as to pass on the same axis. The barcode reader according to claim 3, wherein the plurality of laser light sources emit the laser light so that the emission times do not overlap each other. A light receiving separator that separates the scan beam after scanning the barcode into a plurality of polarized light;
The barcode reader according to any one of claims 1 to 4, further comprising: an optical sensor that inputs the separated polarized light, converts the polarized light into an electrical signal, and outputs the electrical signal. Emits laser light,
Separating the laser light into a plurality of polarized lights;
Propagating each of the polarizations with different optical path lengths,
Combining and outputting each of the polarized lights on the same axis,
A multi-focus forming method, wherein a scan beam including each of the polarized lights is applied to a bar code and scanned. Emits multiple laser beams,
The laser beams are combined so that they pass on the same axis,
The multi-focus formation method according to claim 6, wherein the combined laser beam is separated into a plurality of polarized lights.

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