JPH0950479A - Light projector for bar code reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light projector for bar code reader making the bar code reader exactly read bar code regardless of the state of the bar code, and impoving reading accuracy. SOLUTION: In this light projector for bar code reader for performing a scanning while reflecting the light from laser on the plural reflection surfaces of a polygon mirror 1, a specer 3A to incline the axis line of the polygon mirror 1 for the rotary axis 21 of the motor 2 is provided between the polygon mirror 1 and the plane 20 of rotation of a motor 2 rotating the polygon mirror 1. The projecting part 30 of the spacer 3A is fitted to the recessed to the recessed part 12 of the polygon mirror 1 to position the spacer 3A and the polygon mirror 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projector for a bar code reader.

[0002]

2. Description of the Related Art As shown in FIG. 13, a bar code B has a partial thickening Ba, a thinning Bb and a lacking Bc. Even with such a bar code B, in order to enable stable reading of the bar code, the scanning line S
There is known a bar code reader including a plurality of barcode readers. FIG. 14 shows an example of a floodlight device of this type of bar code reader.

In FIG. 14, a polygon mirror (rotary polygonal mirror) 1 is rotated by a motor 2 and a laser beam La from a laser (not shown) is reflected by a plurality of reflecting surfaces 10 so that a bar code B shown in FIG. To scan. Between the polygon mirror 1 and the rotating surface 20 of the motor 2,
A spacer 3 having a wedge-shaped cross section is inserted, whereby the polygon mirror 1 is attached to the rotation shaft 21 of the motor 2.
The axis line of is inclined by an angle θ. Therefore, as the polygon mirror 1 rotates, the angle of the reflecting surface 10 that reflects the laser light La from the laser changes,
Since the emission direction of the laser light La changes by 4θ,
As shown in FIG. 3, there are plural types of trajectories of the scanning lines S _{1 to} S ₆ . That is, a plurality of scanning lines S _{1 to} S ₆ can be obtained.

[0004]

By the way, the number of scanning lines S varies depending on the positional relationship between the polygon mirror 1 and the spacer 3 in FIG. 14, as will be described below. For example, as shown in FIG. 15 (a), an n-prism polygonal mirror 1
If the angle formed by the straight line L1 passing through the center O and the angle Co of the rotation surface 20 of FIG. 14 is set to θ, that is, if the straight line L1 is set to the straight line Ln of FIG. Since they overlap, there are n / 2 types (n / 2). Further, as shown in FIG. 15B, the center So and the center O of the sides are
When the angle formed by the straight line L2 passing through the line and the rotation surface 20 in FIG. 14 is set to θ, the locus of the scanning line S becomes (n / 2) +1 types (lines). Further, in the cases other than FIGS. 15A and 15B, that is, in the case of FIG. 15C, there are n types (lines) of trajectories of the scanning lines S. In particular, when the straight line L3 that divides the center So of the side and the angle Co at equal angles α and α is set to an angle θ with the rotating surface 20 of FIG. 14, the scanning line S has n types of loci (books). In addition, the intervals between the scanning lines S become substantially equal. Therefore, in general, the state of FIG. 15C is the most preferable.

However, in the above-mentioned prior art, the spacer 3 and the polygon mirror 1 of FIG. 14 are adhered and fixed,
Therefore, the positional relationship between the polygon mirror 1 and the spacer 3 varies. Therefore, it is not decided which state of FIG. 15A to FIG. 15C until actually bonding and assembling, so that the number of scanning lines S and the intervals thereof vary from product to product, and the accuracy of reading is lowered. Cause

By the way, the amount of light reflected from the bar code, that is, the amount of received light, changes depending on the distance from the bar code reader to the bar code. Further, even if the distance is the same, the amount of received light changes due to specular reflection or diffuse reflection depending on the incident angle of the laser light on the barcode. Further, the amount of received light also changes depending on the gloss and color of the barcode label or the like. If the received light amount is too large or too small, black and white cannot be discriminated. Therefore, as a countermeasure against this, conventionally, the emitted light amounts of the scanning lines S ₁ , S ₂ ... S ₆ in FIG. There is a scanning line S _i having a light amount.

However, in such a method, the bar code B is placed on the locus of the scanning line S _i having an appropriate irradiation light amount.
If the defects Ba to Bc are present, the accuracy of reading the barcode is reduced.

The present invention has been made in view of the above-mentioned problems of the prior art, and its object is regardless of the state of the bar code.
It is an object of the present invention to provide a floodlighting device of a bar code reader which enables accurate reading of a bar code and improves the accuracy of reading.

[0009]

In order to achieve the above-mentioned object, the light projecting device of the bar code reader of the first invention is provided with a spacer between the rotary polygon mirror and the rotating surface of the motor, and the spacer is rotated with the spacer. Positioning elements that determine the relative position to the polygon mirror are formed on the spacer and the rotary polygon mirror.

According to the first invention, since the spacer and the rotary polygon mirror are positioned, it is possible to make the number of scanning lines a predetermined number. Therefore, the accuracy of reading the barcode is improved.

In the projector of the bar code reader according to the second aspect of the present invention, the convex portion projecting toward the rotation surface of the motor for rotating the rotary polygon mirror is formed integrally with the rotary polygon mirror, and the axis line of the rotary polygon mirror is formed. It is inclined with respect to the rotation axis of the motor.

According to the second aspect of the invention, since the convex portion is formed integrally with the rotary polygon mirror, a predetermined number of scanning lines can be provided as in the first aspect of the invention.

The light projecting device of the bar code reader according to the third invention is provided with a light quantity control means for changing the output of the laser and periodically changing the emitted light quantity for each scanning line.

According to the third aspect of the invention, since the light quantity for each scanning line changes periodically, it is possible to provide two or more kinds of irradiation light quantity for a scanning line which scans a defect-free portion of a bar code. Therefore, regardless of the state of the barcode such as the barcode defect, the distance to the barcode, the gloss of the barcode, and the color of the barcode, accurate reading can be performed, and the reading accuracy is improved.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a first embodiment of the present invention. In FIG. 3, the laser light La emitted from the semiconductor laser 6a passes through the light projecting lens 50 and is intermittently irradiated toward each reflecting surface 10 of the polygon mirror 1. The polygon mirror 1 is rotated by the motor 2 of FIG. 1, reflects the laser beam La of FIG. 3 toward the bar code B, and scans it. The reflected light Lb reflected by the barcode B is condensed by the condensing lens 51, and the PD
It is incident on the light receiving portion 52 such as a (photodiode). A photo interrupter 64 is provided on the side surface of the polygon mirror 1.
Are provided so as to face each other, and the light Lc emitted toward the reflecting surface 10 of the polygon mirror 1 is specularly reflected from the light projecting element (not shown) of the photo interrupter 64, and the light receiving element of the photo interrupter 64 ( The laser beam La is emitted from the laser 6a based on the timing of incidence on a laser beam (not shown).

In FIG. 1, the motor 2 includes a rotating shaft 21 rotatably mounted on a substrate 9 and the rotating shaft 21.
And a rotor 22 that rotates therewith. Rotor 22
Has a large number of magnetic poles (permanent magnets) not shown,
It is rotationally driven by the electric current flowing through the plurality of coils 23 fixed to the substrate 9.

The polygon mirror 1 is fixed to the rotor 22 by a leaf spring 41. The polygon mirror 1 shown in FIG. 2A is made of, for example, aluminum (metal),
It is formed in a polygonal column shape having a hole 13 in the center. The polygon mirror 1 generally has about 10 reflecting surfaces 10. However, in this specification, for convenience of drawing and explanation,
There are 6 to 8 faces. Polygon mirror 1 and Fig. 1
A spacer 3A for inclining the axis 1C of the polygon mirror 1 with respect to the rotation axis 21 (axis 2C) of the motor 2 is provided between the rotor 22 and the rotation surface 20.
The axis 1C of the polygon mirror 1 is a straight line passing through the center of the end surface (bottom surface) 11 of the polygon mirror 1 and perpendicular to the end surface 11.

As shown in the enlarged view of FIG. 2 (b), the spacer 3A is formed by integrally forming a positioning cylindrical protrusion 30 on a disc-shaped base 31 and has, for example, a diameter of 2
It is made of chip-shaped synthetic resin of about 3 mm.
On the other hand, the end face 11 of the polygon mirror 1 is formed with a recess 12 formed of a small circular hole. The recess 1
2 and the convex portion 30 constitute the positioning element in the present invention, and the relative position between the spacer 3A and the polygon mirror 1 is set by fitting the convex portion 30 of the spacer 3A into the concave portion 12 as shown in FIG. Is determined. The polygon mirror 1 includes a chip-shaped spacer 3A and a rotor 22.
It is fixed while being supported by a part of the rotating surface 20 of the.

The recess 12 is formed as shown in FIG.
It is provided on a straight line L3 that divides the center So of the side of the polygon forming the polygon mirror 1 and the angle Co at equal angles α and α. Therefore, in this embodiment, the same number of scanning lines S ₁ ... S _{n as the} number of the reflective surfaces 10 are obtained.

In the light-projecting device of this bar code reader having the above-described structure, since the concave portion 12 is provided in the polygon mirror 1 of FIG. 2 and the convex portion 30 is provided in the spacer 3A,
The spacer 3A is positioned with respect to the polygon mirror 1. Therefore, the number of scanning lines does not vary from product to product, and a desired number of scanning lines can be obtained. Further, the interval A between the scanning lines S ₁ and S ₆ (hereinafter referred to as “scan width”) A in FIG. 13 is also desired. Therefore, even if the barcode B has a defect such as a chipped portion Bc or a thin portion Bb, the barcode B can be accurately read, so that the reading accuracy is improved.

By the way, when the spacer 3 and the polygon mirror 1 of FIG. 14 are adhered with an adhesive as in the prior art, the inclination angle θ of the polygon mirror 1 changes depending on the amount of the adhesive. On the other hand, since the emission direction of the laser light La changes by the angle 4θ, the scan width A in FIG. 13 also changes depending on the amount of adhesive applied, which may reduce the accuracy of reading.

On the other hand, in the light projecting device of the present bar code reader, since the convex portion 30 of the spacer 3A of FIG. 2 is fitted into the concave portion 12 of the polygon mirror 1, no adhesive is used. The inclination angle θ is also stable and the reading accuracy is improved.

By the way, in this embodiment, the polygon mirror 1 of FIG. 2 is provided with the concave portion 12, and the spacer 3A is provided with the convex portion 30.
However, in the present invention, a convex portion may be formed on the polygon mirror 1 and a concave portion may be formed on the spacer 3. However, when the polygon mirror 1 is made of aluminum metal as in the present embodiment, forming the recess 12 in the polygon mirror 1 makes the machining significantly easier.

By the way, in the above embodiment, the polygon mirror 1 is supported by a part of the rotating surface 20 of the rotor 22 of FIG. 1 and the chip-shaped spacer 3. That is, the polygon mirror 1 is supported at two points. Therefore, the posture of the polygon mirror 1 may not be stable. Therefore, as shown in FIG. 4B, the cylindrical convex portion 30 is formed on the rectangular parallelepiped base 31, and the polygon 31 is formed on the side 31 a of the base 31. The mirror 1 may be supported.

For the same reason, as shown in FIG. 5, a positioning element having a rectangular parallelepiped concave portion 12 is formed on the polygon mirror 1, and a spacer having a rectangular parallelepiped positioning element 30A fitted in the concave portion 12 is provided. It may be 3A.

Further, as shown in FIG. 6 (b), the rectangular parallelepiped convex portion 30 may be integrally formed on the flat plate rectangular parallelepiped base 31 to form the spacer 3A. In addition, the spacer 3
It is not necessary to form A into a chip shape. For example, the convex portion 30 is formed on an annular plate having a bottom area similar to that of the polygon mirror 1.
May be formed.

FIG. 7 is an enlarged perspective view showing the polygon mirror 1 according to the second embodiment. In FIG. 7, in the present embodiment, the polygon mirror 1 has a reflecting surface 10 in which a metal thin film is formed on the surface of synthetic resin. The end surface 11 of the polygon mirror 1 has a rotation surface 2 of the rotor 22 shown in FIG.
The protrusion 12A of FIG. 7 protruding toward 0 is integrally formed. With the convex portion 12A, the axis line of the polygon mirror 1 is the same as in the first embodiment, and the rotary shaft 2 of the motor 2 of FIG.
The state is inclined with respect to 1. It should be noted that the present embodiment has an advantage that the number of parts and the number of assembling steps are reduced. Further, the posture of the polygon mirror 1 may be stabilized by forming the convex portions 12A into a rectangular parallelepiped shape shown in FIG. 7A or by providing a pair as shown in FIG. 7B.

8 to 10 show a third embodiment. In the present embodiment, for convenience of description, the hexagonal prism-shaped polygon mirror 1 is used.
As shown in FIG. 10, the six scanning lines S _{1 to} S ₆
The case of irradiating a bar code with will be described.

As shown in FIG. 8, the bar code reader is
The bar code B is irradiated with the laser light La from the light projecting unit 6,
The light receiving section 52 receives the reflected light Lb. The reflected light Lb is photoelectrically converted by the light receiving unit 52, amplified by the amplifying unit 54, binarized by the binarizing unit 55, and input to the storage unit 70 of the microcomputer 7. The microcomputer 7 includes a decoding unit 71 and a control unit 72, and outputs the decoded signal from the output unit 80 or the display unit 81. In addition, the microcomputer 7
It operates according to commands from the input unit 82, and receives setting changes and communication control from the communication unit 83.

As shown in FIG. 9, the light projecting section 6 includes a semiconductor laser 6a and a P provided in the laser 6a.
It is equipped with D6b. The laser light La from the laser 6a is directly incident on the PD 6b. The output of the laser 6a is controlled by the light quantity control means 60 described below.

The light quantity control means 60 comprises a first reference circuit 62 and a second reference circuit 63. The first and second reference circuits 62 and 63 each have a resistor serving as a reference for the low-level L output and the high-level H output of the laser 6a. The circuits 62 and 63 are connected to the laser drive circuit 61.

The laser light La received by the PD 6b is photoelectrically converted and input to the laser drive circuit 61. The laser drive circuit 61 performs feedback control so that the voltage generated in the first reference circuit 62 or the second reference circuit 63 by the current from the PD 6b becomes a constant value.
The laser 6a is driven. As a result, the laser light La from the laser 6a has either the low level L or the high level H in FIG.

The laser drive circuit 61 shown in FIG.
The laser 6a is intermittently driven based on the timing signal t from the photo interrupter 64 (FIG. 3).
The timing signal t from the photo interrupter 64 is also input to the counter 65 and the switching circuit 66, and the counter 6
5 counts the timing signal t.

The switching circuit 66 includes a photo interrupter 6
4 when receiving the timing signal t from the first reference circuit 62 or the second reference circuit 63.
Alternately connect to 1. Therefore, as shown in FIG. 10, in the first scanning, the output of the scanning lines S _{1 to} S ₆ is L.
(Low level) and H (high level) are alternately changed in this order. The counter 65 in FIG. 9 is a hexadecimal counter, which counts the timing signal t from the photointerrupter 64 to count the number of the scanning lines S _{1 to} S ₆ so that the first scanning is completed. It detects and outputs the count signal k to the switching circuit 66. The switching circuit 66 is the switching circuit 66.
It is set so that it does not switch when it receives the count signal k from the timing signal t.
Therefore, as shown in FIG. 10, in the second scanning, the outputs of the scanning lines S _{1 to} S ₆ are alternately changed in the order of H and L.
In this way, the output of the laser 6a is changed so that the light quantity for each arbitrary scanning line S _i becomes L, H, L, H ...
It changes periodically.

The other structure is similar to that of the first embodiment, and the description thereof is omitted.

As described above, in this embodiment, each scanning line S
Not only the light amounts of _{1 to} S ₆ are different from each other, but also the light amount of each scanning line S _i changes periodically, so that the defect of the bar code, the distance to the bar code, and the laser light incident on the bar code. Since the accurate reading is possible regardless of the bar code state such as the incident angle of La and the gloss and color of the bar code, the reading accuracy is improved.

By the way, conventionally, a method of controlling the output of the laser 6a based on the reflected light Lb (FIG. 3) reflected by the bar code so that the reflected light Lb has a constant light quantity has been proposed. However, in this way, the scan line S _i
Since the length of the mark changes depending on the distance to the article, the reflected light Lb is not reflected from the barcode but also reflected from the surface of the article other than the barcode. Therefore, the quantity of the incident reflected light Lb changes depending on the gloss of the article, which makes it difficult to adjust the laser output and complicates the control circuit.

On the other hand, in this embodiment, the PD 6 of FIG.
The laser beam La directly incident from the laser 6a is detected by b, and the output of the laser 6a is periodically changed irrespective of the light amount of the reflected light Lb from an object such as an article. Therefore, the output of the laser 6a is adjusted. Can be easily realized.

By the way, in the above-described embodiment, as shown in FIG. 10, the light amount of each scanning line S _i is alternately changed every scanning such as L, H, L, H. S _i
The light intensity of L, L, H, H, L, L ...
Thus, it may be changed periodically every two scans. Further, in the present invention, the light amount of each scanning line S _{1 to} S ₆ is not limited to two types of L and H, and 6 types of large amount such as H _{1 to} H ₆ as shown in FIG. after the first scan with the light quantity, so that L ₁ ~L _6,
The second scan may be performed with six small light amounts.

In the third embodiment, the polygon mirror 1 may be fixed as shown in FIG.
The polygon mirrors 1 which are not parallel to each other may be used.

[0041]

As described above, according to the first aspect of the invention, since the spacer and the rotary polygon mirror are positioned with respect to each other by the positioning element, the number of scanning lines and the interval between the scanning lines are predetermined. As a result, the barcode can be accurately read even if the barcode has a defect such as a chip. Therefore, the accuracy of reading is improved.

Further, when the rotary polygon mirror is made of metal, a convex portion is formed on the spacer, while a concave portion is formed on the end face of the rotary polygon mirror, which facilitates machining.

According to the third aspect of the present invention, since the convex portion is integrally formed on the end face of the rotary polygon mirror and the rotary polygon mirror is inclined, the accuracy of reading the bar code is improved as in the first aspect. . Further, since the convex portion is formed integrally with the rotary polygon mirror, the number of parts and the number of assembling steps are reduced.

Further, in the invention of claim 4, since the rotary polygon mirror is made of synthetic resin, the convex portion can be easily formed at the time of molding the rotary polygon mirror.

Further, according to the invention of claim 5, since the output of the laser is changed to change the emitted light amount periodically for each scanning line, the distance to the bar code, the gloss and color of the bar code. Regardless of the barcode status,
Since the barcode can be read accurately, the reading accuracy is improved.

[Brief description of drawings]

FIG. 1 is a side view showing a mechanical structure of a light projecting device showing a first embodiment of the present invention.

FIG. 2 is a plan view of a polygon mirror and an enlarged perspective view of a spacer.

FIG. 3 is a schematic configuration diagram of a barcode reader.

FIG. 4 is a plan view of a polygon mirror according to a modification and an enlarged perspective view of a spacer.

FIG. 5 is a plan view of a polygon mirror and an enlarged perspective view of a spacer according to another modification.

FIG. 6 is a plan view of a polygon mirror and an enlarged perspective view of a spacer according to still another modification.

FIG. 7 is a perspective view of a polygon mirror showing a second embodiment.

FIG. 8 is a block diagram of a barcode reader according to a third embodiment.

FIG. 9 is a block diagram of a light projecting unit according to a third embodiment.

FIG. 10 is a chart showing a change in light amount of a scanning line.

FIG. 11 is a chart showing changes in the light amount of scanning lines.

FIG. 12 is a chart showing changes in the light amount of scanning lines.

FIG. 13 is a conceptual diagram showing a barcode and scanning lines.

FIG. 14 is a schematic side view showing a conventional light projecting device.

FIG. 15 is a schematic diagram illustrating a positioning state of a polygon mirror.

[Explanation of symbols]

 1: Rotating polygonal mirror 1c: Axis 10: Reflective surface 11: End surface 12: Recessed portion (positioning element) 12A: Convex portion 2: Motor 20: Rotational surface 21: Rotation axis 3A: Spacer 30: Convex portion (positioning element) 6a: Laser 60: Light amount control means La: Laser light

Claims (5)

[Claims] 1. A light projecting device for a bar code reader, wherein light from a laser is reflected by a plurality of reflecting surfaces of a rotary polygon mirror and scanned, wherein the rotary polygon mirror and a motor for rotating the rotary polygon mirror. A spacer for tilting the axis of the rotary polygon mirror with respect to the rotation axis of the motor is provided between the rotary surface and the rotary surface, and a positioning element for determining a relative position between the spacer and the rotary polygon mirror is provided. A projector for a bar code reader formed on the spacer and the rotary polygon mirror. 2. The rotary polygon mirror according to claim 1, wherein the rotary polygon mirror is made of metal, and the positioning element has a concave portion formed on an end face of the rotary polygon mirror, and a convex portion formed on the spacer by fitting the concave portion. And a bar code reader floodlight device. 3. A light projecting device for a bar code reader, wherein light from a laser is reflected by a plurality of reflecting surfaces of a rotary polygon mirror and scanned, wherein the rotary polygon mirror is rotated on an end face of the rotary polygon mirror. A projecting device for a bar code reader in which an axis of the rotary polygon mirror is inclined with respect to a rotation axis of the motor by integrally forming a convex portion projecting toward a rotation surface of the motor. 4. The rotating polygon mirror according to claim 3,
A light projecting device for a bar code reader, wherein a metal thin film is formed on the surface of synthetic resin to form the reflecting surface. 5. The rotating polygon mirror is reflected by a plurality of reflecting surfaces of the rotating polygon mirror for scanning, and the reflecting surface of the rotating polygon mirror is inclined with respect to a rotation axis of the motor, thereby enabling the rotation. In a projector for a bar code reader that can obtain a plurality of scanning lines with the rotation of a polygonal mirror, a light amount control means for changing the output of a laser and periodically changing the emitted light amount is provided for each scanning line. A light projection device for a bar code reader, which is characterized in that