JP2785844B2 - Bar code reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bar code reader for reading bar code information by repeatedly deflecting a light beam along a predetermined bar code scanning pattern and scanning the bar code with the bar code scanning pattern. Related to the device. In recent years, information management systems using barcodes have been introduced not only in POS (Point of Seals) systems but also in fields such as OA (office automation) and FA (factory automation). There is a demand for miniaturization and cost reduction of the device.

[0002]

2. Description of the Related Art Referring to FIGS.
FIG. 1 shows a typical example of a conventional stationary bar code reader used in an S system or the like. The bar code reader has a bar code reading window 10 formed of, for example, transparent glass. 10 includes a pair of transmission diffraction hologram elements 10a and 10a '.
And a single transmission diffraction hologram element 10b and a pair of transmission diffraction hologram elements 10c and 10c 'are attached so as to intersect each other. The bar code reader also includes a light beam deflecting optical system, generally designated by the reference numeral 12, comprising a bottom planar reflecting mirror 14 having a generally fan-shaped configuration and a bottom planar reflecting mirror 14. A light beam deflecting means or polygon mirror 18 which is disposed substantially at the center of the fan shape of the mirror 14 and is rotated clockwise at a constant speed by an appropriate motor 16 and a peripheral edge of the fan shape of the bottom plane reflecting mirror 14 Are formed at the center of three long plane reflecting mirrors 20a, 20b, and 20c arranged at positions above and along the center of a spherical concave mirror 22 arranged below the central long plane reflecting mirror 20b. Small hole 2
The small flat mirror 24 (FIG. 19)
And FIG. 20). In FIG. 18, the bar code reading window 10 and the light beam deflecting optical system 12 are shown separated from each other in order to avoid complication of the drawing. On the other hand, the barcode reading window 10 is arranged as shown by a dotted line in FIG.

In the example shown in FIG. 18, a laser beam is used as a light beam, and this laser beam is obtained from a suitable laser light source, for example, a gas laser tube 26. The laser beam L generated by the gas laser tube 26 is first shaped into a predetermined sectional shape by a beam shaping lens 28 and narrowed down to a predetermined beam diameter, and then the laser beam LB is beam-formed by a plane reflecting mirror 30. The light is guided to the deflection optical system 14. That is, as shown in FIG. 19, the laser beam LB is first made incident on the small plane reflecting mirror 24 through the small hole 22a of the spherical concave mirror 22, and the reflected laser beam LB reflected there is emitted from the small hole 22a of the spherical concave surface 22. It is made to face the rotating polygon mirror 18.

When each reflecting surface of the polygon mirror 18 traverses the laser beam LB coming toward it, the laser beam LB scans three long flat reflecting mirrors 20a, 20b and 20c in the longitudinal direction. The laser beam LB, which is sequentially deflected and scans each of the long plane reflecting mirrors 20a, 20b, 20c, is directed to the bottom plane reflecting mirror 16 and then reflected toward the barcode reading window 10. At this time, the laser beam that scans the long plane mirror 20a is a pair of transmission diffraction hologram elements 10a and 1a.
0a ', the laser beam scanning the long plane mirror 20b is incident along the transmission type diffraction hologram element 10b, and the laser beam scanning the long plane mirror 20c is a pair of transmission type hologram elements. The light is made incident along one of the diffraction hologram elements 10c and 10c '.

More specifically, in the illustrated example, the polygon mirror 18 has a hexagonal shape, and its six reflecting surfaces have two kinds of reflecting angles, three reflecting surfaces having one reflecting angle and the other reflecting angle. Are alternately arranged with the three reflecting surfaces having. When the laser beam LB deflected by the reflection surface having one reflection angle scans the long plane reflecting mirrors 20a, 20b and 20c, the scanning laser beams are transmitted through the transmission type diffraction hologram elements 10a, 10b and 1 respectively.
0c, the laser beam LB deflected by the reflection surface having the other reflection angle is deflected so as to scan the long plane reflecting mirrors 20a, 20b and 20c. The light is incident along the transmission type diffraction hologram elements 10a ', 10b and 10c'.

In short, three long flat reflecting mirrors 20a,
By 20b and 20c and the polygon mirror 18,
The laser beam LB is transmitted through the transmission diffraction hologram element 10a,
The light is repeatedly incident in the order of 10b, 10c, 10a ', 10b and 10c'. In this order, each transmission diffraction hologram element 10a, 10b, 10
The laser beams incident on c, 10a ', 10b, and 10c' are diffracted in a predetermined direction. As a result, a scanning pattern 32 is drawn above the bar code reading window 10 by the diffracted laser beam. 32 comprises line segments 32a, 32a ', 32b, 32b', 32c and 32c '. That is, the transmission diffraction hologram elements 10a, 10b, 10c, 10a ', 10b and 1
The laser beams incident in the order of 0c 'are line segments 32, respectively.
a, 32a ', 32b, 32b', 32c and 32
It will be diffracted along c '. When a laser beam deflected by the reflecting surface of the polygon mirror 18 having two kinds of reflection angles scans the long plane reflecting mirror 20b, the scanning laser beams are both incident on the same transmission type diffraction hologram element 10b. Therefore, the diffraction directions of the incident laser beams are the same, and the distance between the line segments 32b and 32b 'appears as a difference between the two types of reflection angles of the polygon mirror 18.

When a bar code is read by the above-described bar code reader, the article G with the bar code B is passed over the bar code reading window 10 while being held by the operator's hand. When the bar code forms the scanning pattern 32, the line segments 32a, 32
When scanned by any of the laser beams diffracted or deflected along a ', 32b, 32b', 32c and 32c ', a portion of the reflected scattered light is reflected by the laser beam as shown by the dashed line in FIG. The light is returned along the exit optical path, is incident on the spherical concave mirror 22, and is then detected by the photodetector 34 arranged at the condensing point of the spherical concave mirror 22. As apparent from FIGS. 19 and 20, the photodetector 34 is composed of a small inclined plane reflecting mirror 34a and a photodiode 34b disposed therebelow, and the reflected scattered light converged by the spherical concave mirror 22 is reduced by a small inclined plane. After being once reflected by the reflecting mirror 34a, it is directed to the light receiving portion of the photodiode 34b. In short, the light receiving portion of the photodiode 34b is located at the converging point of the spherical concave mirror 22, and receives the convergent reflected scattered light from the spherical concave mirror 22 via the inclined plane reflecting mirror 34a. When the rotation speed of the polygon mirror 18 is compared with the speed of light, the polygon mirror 18 can be considered to be in a stopped state, so that the laser beam reflected by the reflection surface of the polygon mirror 18 is reflected and scattered by scanning the bar code. When the light enters the polygon mirror 18 again as light, the rotational displacement of the reflection surface of the polygon mirror 18 can be almost ignored.

The barcode information detected by the photodetector 34 is processed by a barcode decoding circuit (not shown) composed of a microcomputer or the like. In this case, it is determined whether or not the detected barcode information is complete. If the barcode information is complete, for example, a signal sound is emitted, and the signal sound allows the operator to read the barcode information. Know it's done. On the other hand, if the barcode information is incomplete, for example, if the barcode is only partially scanned by the laser beam,
Such a signal tone is not emitted and the detected barcode information is ignored as incomplete. At this time, the operator repeats the barcode reading operation until the above-mentioned signal sound is emitted.

[0009]

As is apparent from the above description, since the conventional bar code reader has a relatively complicated light beam deflecting optical system, the overall configuration is bulky and bulky. This is not only a problem, but also an economical problem that the manufacturing cost is high. Therefore, an object of the present invention is to provide a bar code reading apparatus for reading bar code information by repeatedly deflecting a light beam along a predetermined bar code reading scanning pattern and scanning a bar code with the bar code reading scanning pattern. Accordingly, it is an object of the present invention to provide a bar code reader which can be reduced in size and manufactured at low cost.

[0010]

SUMMARY OF THE INVENTION A bar code reader according to the present invention comprises a light beam deflecting means for repeatedly deflecting a light beam along at least one path, and a transmission type diffraction hologram means arranged along said path. With
This transmission type diffraction hologram means has a diffraction characteristic such that a polarized light beam incident thereon is diffracted to form a predetermined bar code reading scanning pattern.

According to the present invention, a transmission type diffraction hologram means is used for forming a bar code reading scanning pattern, and such a transmission type diffraction hologram means can be designed so as to obtain a desired diffraction characteristic. Not only is it relatively easy, but it can also be made relatively cheaply.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a bar code reader according to an embodiment of the present invention; FIG. FIG. 1 is a perspective view schematically showing the overall structure of a bar code reader according to the present invention, which comprises a rectangular housing 36 shown by broken lines.
One side wall portion of the housing 36 is formed of a transmission type diffraction hologram means 40 and a reflection type diffraction hologram means 42. As is apparent from FIG. Located in. In this embodiment, the transmission diffraction hologram means 40 comprises three transmission diffraction hologram elements 40a, 40b and 40c, each of which has different diffraction characteristics as described later. Further, the reflection type diffraction hologram means 42 is configured as a single reflection type diffraction hologram element, which has the same characteristics as the spherical concave reflection mirror, that is, the light condensing diffraction characteristics. As best shown in FIG. 2, a reflection type diffraction hologram element 44 having another diffraction characteristic is formed in a small area substantially at the center of the reflection type diffraction hologram means 42. Has the property of diffracting and deflecting the light beam incident on the. The reflection type diffraction hologram element 44 can be attached to the reflection type diffraction hologram means 42 formed in advance, or the reflection type diffraction hologram element can be applied to a substrate common to the reflection type diffraction hologram means 42 by applying a masking technique. It is also possible to form 44.

A polygon mirror 46 is provided in the housing 36 as a light beam deflecting means. In this embodiment, the polygon mirror 46 has a pentagon shape and is rotated clockwise at a constant speed. The polygon mirror 46 forms a light beam deflecting optical system together with the reflection type diffraction hologram element 44, and repeatedly deflects a light beam from a light beam source 48 provided in the housing 36 along a predetermined path. The light beam generating source 48 is formed as, for example, a semiconductor laser. The laser beam generated by the semiconductor laser 48 is shaped by a beam shaping lens 50 and then incident on the reflection diffraction hologram element 44 as a laser beam LB. When the reflection type diffraction hologram element 44 diffracts the laser beam LB incident thereon toward the polygon mirror 46, the rotating polygon mirror 46 repeats the laser beam LB by the five reflection surfaces along a predetermined path 52. To deflect. That is, each time the polygon mirror 46 makes one rotation, the laser beam LB is deflected five times along the path 52.

As is apparent from FIGS. 1 and 3, the transmission diffraction hologram means 40 is arranged along the path 52, and therefore, the transmission diffraction hologram elements 40a, 40b and 40c of the transmission diffraction hologram means 40 are provided. The deflected laser beams LB are sequentially incident. The deflection laser beam LB is transmitted through the transmission type diffraction hologram elements 40a, 40
b and 40c, each of the transmission diffraction hologram elements 40a, 40b, and 40c diffracts a deflected light beam in accordance with the respective diffraction characteristics. A bar code reading scanning pattern 54 is drawn on the upper side, and the bar code reading scanning pattern 54 is formed from line segments 54a, 54b, and 54c that cross each other. That is, as shown in FIG. 3, the deflected laser beam incident on the transmission type diffraction hologram element 40a has a line segment 54.
a, the deflected laser beam incident on the transmission diffraction hologram element 40b is diffracted and deflected along the line segment 54b.
The deflected laser beam incident on c is diffracted and deflected along a line segment 54c, whereby a bar code reading scanning pattern 54 is obtained. The point to note here is that
The deflection trajectory (54b) of the laser beam diffracted and deflected by the transmission diffraction hologram element 40b is parallel to the deflection trajectory (52) of the laser beam incident on the transmission diffraction hologram element 40b. That the deflection trajectories (54a, 54c) of the laser beams diffracted and deflected by the hologram elements 40a and 40c are turned with respect to the deflection trajectories (52) of the laser beams incident on the transmission diffraction hologram elements 40a and 40b. This will be described in detail later.

As shown in FIG. 4, the bar code B attached to the article G is passed through the upper part outside the transmission type diffraction hologram means 40, and the bar code reading scanning pattern 5 is read.
Scanning with a laser beam diffracted and deflected along any of the four line segments 54a, 54b and 54c,
Part of the reflected scattered light is returned to the polygon mirror 46 along the laser beam emission path. For example, line segment 54
When the bar code B is scanned with the laser beam diffracted and deflected along the line b, a part of the reflected scattered light is incident on the transmission type diffraction hologram element 40b and
6, and then the polygon mirror 46
Thus, the light is reflected toward the reflection type diffraction hologram means 42. The reflected scattered light incident on the reflection type diffraction hologram means 42 is condensed and diffracted toward the light detecting means 56 as best shown in FIG. 5, and the condensed diffracted light is converted into bar code information by the light detecting means 56. Is detected. The light detecting means 56 is formed of, for example, a photodiode, and the bar code information detected by the light detecting means 56 is processed by a bar code decoding circuit (not shown) constituted by a microcomputer or the like, as in the case described above. .

Referring to FIG. 6, there is shown an example of forming the transmission type diffraction hologram element 40b. In FIG. 6, reference numeral 58 indicates a recording medium formed by applying a photosensitive emulsion to a transparent film substrate, for example. Assuming a three-dimensional orthogonal coordinate system xyz having a coordinate origin at the center of the medium 58,
It is assumed that the recording medium 58 is located in the y plane. The reference light source 60 is located within the zy plane of the three-dimensional rectangular coordinate system xyz.
When the object light source 62 is disposed with the y-axis interposed therebetween, interference fringes are formed on the recording medium 46 by the interference of the spherical waves generated from the light sources 60 and 62, and are recorded. By developing / fixing the recording medium 58, a transmission diffraction hologram element having diffraction grating fringes is obtained. Referring to FIG. 7, such a transmission-type diffraction hologram element is indicated by reference numeral 58 ', and a three-dimensional orthogonal coordinate system xyz similar to FIG. place the laser beam source 60 'as a reproduction light source in the yz plane, the transmission diffraction laser beam emitted therefrom is deflected along the x-axis as indicated by L _1, L ₂ and L ₃ 'when the transmit, transmitted laser beam L _1' hologram element 56, but is diffracted by such deviates from the x-axis as shown by L ₂ 'and L _3', the deflection trajectory of the transmitted laser beam is the x-axis (Note that in FIG. 7,
x 'and y' denote the projection axes of the x and y axes, respectively). In FIG. 6, the diffraction angles of the diffracted laser beams L ₁ ′, L ₂ ′, and L ₃ can be arbitrarily determined by appropriately selecting the angular positions of the reference light source 60 and the object light source 62.

Referring now to FIG. 8, there is shown an example in which the transmission type diffraction hologram elements 40a and 40c are formed. In FIG. 8, a three-dimensional coordinate system xyz similar to FIG. I do. 8, the reference light source 60 and the object light source 62 are arranged at positions shifted from the yz plane to one side of the x-axis (the positive side in the example of FIG. 8). The creation method of FIG. 8 is different from the creation method of FIG. The interference fringes are formed and recorded on the recording medium 58 by the interference of the spherical waves generated from both of the light sources 60 and 62, and then the recording medium 58 is developed / fixed to form a transmission diffraction hologram having diffraction grating fringes. Obtaining the elements is the same as in FIG. Referring to FIG. 9, such a transmission diffractive hologram element is designated by reference numeral 58 ".
8 ", a three-dimensional orthogonal coordinate system xyz similar to that in FIG. 8 is assumed, and a laser beam source 60 'is arranged as a reproduction light source in the yz plane as in FIG. Is deflected along the x-axis as indicated by L ₁ , L ₂ and L ₃ and transmitted through the transmission diffraction hologram element 58 ″, the transmitted laser beams are L ₁ ′, L ₂ ′ and Although diffracted so as to deviate from the x-axis as shown by L ₃ ′, the deflection trajectory of the transmitted laser beam is rotated counterclockwise differently from the case of FIG. And y 'denote the x-axis and y-axis projection axes, respectively). In FIG. 8 as well, by appropriately selecting the angular positions of the reference light source 60 and the object light source 62, the diffracted laser beams L ₁ ′, L ₂ ′,
The diffraction angle of the L ₃ may optionally be determined.

The reason why the transmission type diffraction hologram element 58 "obtained by the production method shown in FIG. 8 has a diffraction characteristic for rotating a laser beam will be briefly described. The spatial frequency of the interference fringes recorded on the x-axis gradually increases toward the positive side of the x-axis, and the laser beam from the laser beam generation source 60 ′ shifted from the reference light generation source 60 toward the yz plane is shifted along the x-axis. Is subjected to a greater diffraction effect on the positive side of. In other words, the largest the diffraction action of the laser beam L ₃ which passes the largest side of the spatial frequency of the fringe, the diffraction effect of the laser beam L ₁ passing through the smallest side of the spatial frequency of the fringe is the smallest, and therefore The deflection trajectory of the transmitted laser beam is turned as shown in FIG.

Incidentally, in the transmission type diffraction hologram element 58 ″ shown in FIG. 9, in order to increase the turning angle of the deflection trajectory of the diffracted laser beam, the laser beam source 6 is required.
The position of 0 'may be moved to the negative side of the x-axis. However, the farther the laser beam source 60' is shifted from the position of the reference beam source 60, the more the incident beam on the transmission type diffraction hologram element 58 ". The laser beam greatly deviates from the Bragg condition, which causes a problem that the intensity of the diffracted laser beam is weakened, and also causes a problem that the aberration of the emitted laser beam is increased. In the case where the beam diameter of the laser beam is increased due to the aberration, the reflected scattered light obtained at the time of scanning the bar code, that is, the S / N ratio of the bar code information decreases, and the accuracy of reading the bar code decreases. However, such a problem is solved by using a plurality of transmission type diffraction hologram elements 58 ″ as shown in FIG. Doo is possible, it will be described below this.

Referring to FIG. 10, two transmission-type diffraction hologram elements 58 ″ as shown in FIG. Transmission type diffraction hologram element 58
b. Upper transmission diffraction hologram element 58
9a is arranged in the same direction as the transmission-type diffraction hologram element 58 ″ shown in FIG. 9, while the transmission-type diffraction hologram element 58b on the lower side is replaced with the transmission-type diffraction hologram element 58 ″ shown in FIG. It is arranged in a direction rotated by 180 ° in the plane. That is, in the transmission diffraction hologram element 58a, the spatial frequency of the interference fringe gradually increases toward the positive side of the x-axis, whereas in the transmission diffraction hologram element 58b, the spatial frequency of the interference fringe is It gradually increases toward the negative side of the x-axis. The two transmission diffraction hologram elements 58a and 58b are shown in FIG.
As shown in FIG. 10, they are bonded together while maintaining the relationship of FIG.

Two-stage transmission type diffraction hologram element 58
The diffraction characteristics of a and 58b are the product of their individual diffraction characteristics. Transmission type diffraction hologram element 5
The diffraction characteristics of the transmission diffraction hologram element 58b are the same as those described with reference to FIG.
As shown in Fig. 12, the diffraction characteristics obtained when the transmission type diffraction hologram element 58 "is rotationally displaced by 180 degrees in the xy plane are the same. In short, Fig. 12 shows Fig. 9 observed from the back side of the drawing. It should be noted that in FIG.
While the laser beam is deflected along its x-axis towards its positive side, in FIG. 12, the laser beam is deflected along its x-axis towards its negative side, but the diffraction pattern of the laser beam is Is similar.

Here, the transmission type diffraction hologram element 58a
Of the diffracted laser beam diffracted through the beam
Considering the light source of FIG.
Position P as shown₁From position P_TwoThrough position P_ThreeMa
Move with. In FIG. 13, the illustration is not complicated.
Transmission diffraction hologram element 58a is omitted
However, the deflected laser beam L incident thereon₁, L_Two
And L_ThreeAnd their diffracted laser beams L₁', L
_Two'And L_Three'Is the same as that shown in FIG. Figure
As shown in FIG.₁', L_Two´O
And L_Three'Is actually yz as described in FIG.
Laser beam source 60 'located in the plane
But their apparent light sources are located
P₁, P_TwoAnd position P_ThreeIt is arranged in. I
Therefore, the laser beam from the laser beam source 60 '
If the system is deflected along its x-axis towards its positive side,
The apparent light source of the diffracted laser beam is located in the yz plane
P₁From position P_TwoThrough position P _ThreeMoving light moving up
Can be considered a source.

This is because the transmission type diffraction hologram element 5
8b is incident on the position P₁Or
Position P_TwoThrough position P_ThreeFrom a moving light source that moves up
Will be obtained. Referring to FIG. 14, the position P₁Or
Position P_TwoThrough position P_ThreeLaser beam traveling up
The transmission type diffraction hologram element 58b (see FIG.
In Fig. 4, a transmission diffraction hologram is used to avoid complication of the drawing.
The ram element 58b is omitted).
The beam is LP₁, LP_TwoAnd LP_ThreeIndicated by
From the laser beam source 60 'in FIG.
Laser beam L incident on Gram element 58a₁,
L_TwoAnd L_ThreeAnd their diffracted laser beams L₁', L
_Two'And L_Three'Is also shown for reference. FIG.
As is clear from FIG.₁From the light source at
Laser beam LP₁Is the laser beam from the light source 60 '
L₁At the same location as₁Is the light source 60 '
Because the diffraction laser beam LP₁′
Diffraction angle of the diffraction laser beam L₁'Greater than the diffraction angle
No. Position P₁Emitted from light source at and incident on coordinate origin
Laser beam LP_TwoFrom the light source 60 'to the coordinate origin
Laser beam L _TwoAnd the diffraction laser beam
Room LP_Two'Is also the diffracted laser beam L_Two'. Rank
Place P_ThreeBeam LP emitted from a light source located in_ThreeIs
Laser beam L from light source 60 '_ThreeIncident on the same place as
Position P_ThreeIs below the light source 60 ',
The diffracted laser beam LP_Three'Is a diffracted laser beam
L_Three′ Is further diffracted in the negative direction of the y-axis.

Thus, as shown in FIG. 15, the laser beam is emitted from the laser beam source 60 'to the two-stage transmission type diffraction hologram elements 58a and 58b and is deflected along the x-axis toward its positive side. Laser beam L
_1, L ₂ and L ₃ transmission diffraction hologram element 58a
The diffraction laser beams LP ₁ ′, LP ₂ ′ and LP ₃ ′ are subjected to the respective diffraction actions of the diffraction laser beams 58 and 58b, and the deflection trajectories of these diffraction laser beams are further rotated as compared with the case of FIG. Here, it should be noted that since the laser beam can enter the transmission type diffraction hologram elements 58a and 58b without greatly deviating from the Bragg condition, the intensity of the diffracted laser beam is hardly weakened. is there. In order to further increase the turning angle of the deflection trajectory of the diffracted laser beam, a plurality of transmission diffraction hologram elements 58 ″ as shown in FIG. The hologram elements have the relationship as described in FIG.

In the examples shown in FIG. 10 and FIG. 11, the transmission diffraction hologram elements 58a and 58b which are individually formed are bonded to each other, but a plurality of transmission diffraction hologram elements are formed on the same transparent film substrate. It is also possible to create them sequentially. Further, it is preferable to eliminate the wavefront aberration by giving the same spatial frequency characteristics to the respective interference fringes of the transmission type diffraction hologram elements 58a and 58b.

FIG. 16 shows a reflection type diffraction hologram means 42.
In the figure, reference numeral 64 indicates a suitable transparent substrate coated with a photosensitive emulsion, one side of which is irradiated with divergent reference light 66, and the other side is convergent object light. 68 are illuminated. The interference fringes generated by the interference between the diverging reference light 66 and the convergent object light 68 are recorded on the photosensitive emulsion layer of the transparent substrate 64, and when the transparent substrate 64 is developed, the reflection type diffraction hologram element 6 shown in FIG.
4 'is created. As shown in FIG. 17, when the divergent reproduction reference light 66 enters the reflection type diffraction hologram element 64 ', the diffracted light 68' becomes convergent light. If such a reflection type diffraction hologram element 46 ′ is used as the reflection type diffraction hologram means 42, the reflected scattered light obtained by scanning the bar code can be converged toward the light detection means 56. The diverging reference light 66 for the transparent substrate 64
By appropriately selecting the light source positions of the converging object light 68 and the converging object light 68, it is possible to arbitrarily determine the converging point of the diffracted light 68 '.

In the above-described embodiment, the transmission diffraction hologram means 40 comprises three transmission diffraction hologram elements 40a,
0b and 40c are arranged in a row in the horizontal direction, but the number of transmission diffraction hologram elements is 3
Needless to say, the present invention is not limited to this, and various embodiments can be considered for the sequence. For example, a plurality of transmission-type diffraction hologram elements are arranged in upper and lower two rows, and a laser beam is alternately incident on the transmission-type diffraction hologram elements in the upper and lower two rows by using the polygon mirror 18 described with reference to FIG. In this case, a more complicated bar code reading scanning pattern than that shown in FIG. 1 can be obtained, so that the bar code reading accuracy can be further improved. Further, in the above-described embodiment, a plane reflection mirror may be used instead of the reflection type diffraction hologram element 44,
Also, instead of the reflection type diffraction hologram means 42 and the reflection type diffraction hologram element 44, it is possible to use a spherical concave mirror 22 and a plane reflection mirror 24 as shown in FIG.

[0027]

As is apparent from the above configuration, according to the present invention, a transmission type diffraction hologram means is used for forming a bar code reading scanning pattern. Is not only relatively easy to design so as to obtain the diffraction characteristics, but also the production itself can be performed relatively inexpensively.
It is possible to reduce the size and simplification of the barcode reader and to reduce its manufacturing cost.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing one embodiment of a barcode reader according to the present invention.

FIG. 2 is a perspective view showing a part of the bar code reader of FIG. 1;

FIG. 3 is a perspective view showing a part of the bar code reader of FIG. 1;

FIG. 4 is a perspective view showing an appearance of the bar code reader of FIG. 1, showing a bar code reading state.

FIG. 5 is a perspective view showing a part of the bar code reader of FIG. 1;

FIG. 6 is a perspective view showing an example of forming a transmission type diffraction hologram element used in the bar code reader of FIG. 1;

FIG. 7 is a perspective view showing diffraction characteristics of a transmission type diffraction hologram element obtained by the production method of FIG. 6;

FIG. 8 is a perspective view showing an example of forming another type of transmission diffraction hologram element used in the bar code reader of FIG. 1;

FIG. 9 is a perspective view showing diffraction characteristics of the transmission type diffraction hologram element obtained by the method of FIG.

FIG. 10 is a perspective view illustrating a method of forming another transmission type diffraction hologram element using two transmission type diffraction hologram elements of the type shown in FIG. 9;

FIG. 11 is a side view showing the two transmission diffraction hologram elements of FIG.

FIG. 12 is a perspective view for explaining the diffraction characteristics of the two-stage transmission type diffraction hologram element of FIG. 11;

13 is a perspective view for explaining the diffraction characteristics of the two-stage transmission type diffraction hologram element shown in FIG. 11;

FIG. 14 is a perspective view for explaining the diffraction characteristics of the two-stage transmission type diffraction hologram element of FIG. 11;

FIG. 15 is a perspective view showing diffraction characteristics of the two-stage transmission type diffraction hologram element shown in FIG. 11;

FIG. 16 is a side view showing a production example of a reflection type diffraction hologram means used in the bar code reader of FIG. 1;

FIG. 17 is a side view showing the diffraction characteristics of the reflection type diffraction hologram means of FIG.

FIG. 18 is a perspective view showing a conventional bar code reader.

FIG. 19 is a side view of the bar code reader of FIG. 18, showing a laser beam emission path for bar code scanning.

FIG. 20 is a side view similar to FIG. 19, showing a detection path of reflected scattered light during barcode scanning.

[Explanation of symbols]

 36 housing 40 transmission diffraction hologram means 40a 40b 40c transmission diffraction hologram element 42 reflection diffraction hologram means 48 light beam source 50 beam forming lens 52 path 54 scanning pattern 56 light detection means

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G06K 7/12 G02B 26/10 102 G06K 7/10

Claims (3)

(57) [Claims] The light beam is directed through at least one path (5).
Light beam deflecting means (4) for repeatedly deflecting along (2)
6) and a plurality of transmission-type diffraction hologram means (40) arranged along the path (52), and the plurality of transmission-type diffraction hologram means (40) continuously scan therethrough. A bar code reading device having a diffraction characteristic such that a light beam is diffracted in different directions by respective transmission type diffraction hologram means to form a predetermined bar code reading scanning pattern (54). 2. The bar code reading device according to claim 1, wherein said bar code reading scanning pattern (54).
Light detecting means (56) for detecting, as bar code information, a part of the reflected scattered light obtained when the bar code is scanned, and receiving the part of the reflected scattered light and performing light detection. And a reflection type diffraction hologram means (42) for converging light toward the means (56). 3. The bar code reader according to claim 2, further comprising: a reflection type diffraction hologram means (44) for reflecting a light beam from a light source and directing the light beam to said light beam deflecting means (46). A bar code reader characterized by the above-mentioned.