JPH06325199A - Optical reader and optical read system for latent image mark - Google Patents

Abstract

PURPOSE:To take large output out, to decrease read errors, and to improve the reliability by making the total area of projection on a latent image mark larger than the total area of photodetection of light emitted from the latent image mark. CONSTITUTION:A light emitting element 3 such as an LED, a projection-side optical fiber 4, a photodetection-side optical fiber 5, an optical filter 6, and a photodetecting element 7 are provided. The projection-side optical fiber 4 and photodetection-side optical fiber 5 constitute a coaxial cable by integrating their detection sides facing the latent image mark 2. In this case, glass-made optical fibers which are equal in diameter are used for the projection-side optical fiber 4 and photodetection-side optical fiber 5, and the using number of projection-side optical fiber units 4a are more than that of photodetection-side optical fiber units 5a, so that the total area of projection on the latent image mark 2 is larger than the total area of photodetection. Further, many projection- side optical fiber units 4a and many photodetection-side optical fiber units 5a are arranged at random.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a latent image mark optical reading apparatus for projecting infrared rays onto a latent image mark containing a fluorescent substance to optically detect light emitted from the latent image mark, and an optical reading apparatus therefor. The present invention relates to a system, and particularly to a relationship between a total projected area and a total received area of a latent image mark.

[0002]

2. Description of the Related Art In a conventional reflective bar code, a printing ink containing carbon black is generally used. With this ink, a bar code is printed on the surface of a paper, and a part where the bar code is printed is printed. The code information was read by optically detecting the difference in light reflectance from the non-existing portion with a barcode reader.

However, this reflective bar code impairs the appearance of the product because the bar code is printed on the surface of the product, and the above-mentioned difference in reflectance occurs when the printed surface is soiled. It has a drawback that it becomes small and causes a read error.

In order to solve such a drawback, various methods are used in which a latent image mark containing a phosphor is printed, infrared rays are projected onto the latent image mark, and light emitted from the latent image mark is optically detected. Proposed.

12 to 15 are shown in Japanese Patent Application Laid-Open No. 53-96.
It is a figure for demonstrating the optical reader of this kind described in the 00 publication.

12 and 13 are views showing the first conventional example, FIG. 12 is a side view of the optical reading device, and FIG. 13 is an enlarged plan view showing the relationship between the light projecting surface and the light receiving surface.

In the case of this example, the light receiving side optical fibers 52 are provided on both sides of the semiconductor light emitting element 51 (vertical direction toward the paper).
Are arranged so as to face the latent image marks 54 printed on the paper 53.

A light receiving element 56 is arranged at the other end of the light receiving side optical fiber 52 through an optical filter 55, and an optical signal received by the light receiving element 56 is converted into an electric signal, and then a signal is outputted at a computer terminal 57. To be processed.

Reference numeral 58 in FIG. 13 denotes a light projecting surface for irradiating the latent image mark 54 with light, and 59 denotes a light receiving surface for receiving the light emitted from the latent image mark 54.

14 and 15 are views showing a second conventional example, FIG. 14 is a side view of an optical reading device, and FIG. 15 is an enlarged plan view showing a relationship between a light projecting surface and a light receiving surface.

In this example, a light projecting side optical fiber 60 is arranged between the light emitting element 51 and the latent image mark 54, and the projecting side optical fiber 60 and the light receiving side optical fiber 52 are integrally formed on the detection side facing the latent image mark 54. Is bound to.

As shown in FIG. 15, one light receiving surface 59 is provided at the center, and a plurality of light receiving surfaces 59 and light projecting surfaces 58 are alternately arranged on the outer periphery thereof.

[0013]

By the way, in the above-mentioned conventional optical reader, the output when the latent image mark is detected is small, which causes erroneous detection and has a problem in reliability. The tendency of low output is to emit light to a latent image mark containing a phosphor to excite the phosphor, and then stop the light emission to optically detect the afterglow of the phosphor. This is remarkable in the optical reading system (details will be described later).

As a result of various studies on the cause of this low output, the present inventors have found that the areas of the light projecting surface and the light receiving surface are related.

That is, in the conventional optical reading apparatus, as shown in FIG.
3 and FIG. 15, the total area (S1) of the light projecting surface with respect to the latent image mark is smaller than the total area (S2) of the light receiving surface (S1 <S2).

For example, when the latent image mark is a bar code, J
In the AN code, the thinnest bar has a line width of 0.264
mm, and the distance between adjacent bars is 0.2 mm (J
ISX 0501 Common product code bar code symbol), the thinnest bar can be detected without detecting the adjacent bar at the same time, or a latent image mark attached to an extremely fine line body such as a thread or an extremely small part. In the case of detecting, the detection area (light emitting area + light receiving area) facing the latent image mark is limited, and for example, the diameter of the detection surface is 1.6 m.
Limited to about m.

Further, the light emitted from the phosphor is weak,
Moreover, since the light has no directivity, it is necessary to bring the light-receiving surface as close as possible to the latent image mark, and the detection area is limited when performing the above-described ultra-fine or minimal detection. Will end up.

Further, depending on the object to be detected, it may be detected in a narrow place, and this also limits the detection area.

When the total area of the light projecting surface (S1) is smaller than the total area of the light receiving surface (S2) (S1 <S2) under such a situation that the detection area is limited, the fluorescent material It was clarified that the excitation was insufficient and therefore the output when the latent image mark was detected was small, which was the cause of erroneous detection.

An object of the present invention is to eliminate such drawbacks of the prior art and provide a highly reliable latent image mark optical reading apparatus and optical reading system capable of obtaining a large output.

[0021]

In order to achieve the above-mentioned object, the present invention projects excitation light onto a latent image mark containing a phosphor and optically detects the light emitted from the latent image mark. An optical reader for latent image marks and a latent image for projecting light to a latent image mark containing a phosphor to excite the phosphor, and then stopping the projection to optically detect the afterglow of the phosphor. In the mark optical reading system, the total projected area S1 for the latent image mark is larger than the total received light area S2 for receiving the light emitted from the latent image mark (S1> S2).

[0022]

As described above, according to the present invention, under the condition that the detection area (light emitting area + light receiving area) facing the latent image mark is limited, by setting S1> S2, which is contrary to the conventional one, fluorescence can be obtained. Since the amount of light projected onto the body can be increased and sufficient excitation can be performed, a large output can be taken out, reading errors are reduced, and as a result, reliability can be improved.

[0023]

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 is a side view of an optical reading device according to an embodiment, and FIG.
FIG. 3 is an enlarged cross-sectional view taken along line AA, FIG. 3 is a diagram for explaining output states of a light emitting element and a light receiving element in the optical reading device, FIG. 4 is a block diagram of the optical reading device, and FIG. 5 is an emission spectrum diagram. Is.

For example, a latent image mark 2 having information such as a bar code, a number, a character, a symbol, a pattern, and a pattern, which cannot be recognized by the naked eye, is printed on the object 1 to be detected such as a sheet, a label, and a part by printing. There is.

The latent image mark 2 is composed of phosphor fine particles that emit light when irradiated with infrared rays including near infrared rays, and a binder that has a property of transmitting infrared rays and holds the phosphor fine particles in a dispersed state.

Examples of the phosphor include neodymium (Nd), ytterbium (Yb) and eurobium (E).
u), thulium (Tm), praseodymium (Pr), dysprosium (Dy), and other rare earth elements, or a mixture thereof, as emission centers, and these emission centers are fluorides, phosphates, molybdates, and tungstates. Inorganic compounds whose oxides such as are contained in the matrix, specifically,
NdP ₅ O ₁₄ , LiNdP ₄ O ₁₂ , NaY _0.69 Yb _0.3
There are inorganic compounds such as Er _0.01 F ₄ .

Further, an inorganic compound represented by the following general formula can also be used. General formula Ln _1-XY Nd _X Yb _Y Z Ln in the formula is Bi, Ge, Ga, Gd, In, La, L
Represents one or more elements selected from the group of u, Sb, Sc, Y. In the formula, Z represents A ₅ (MO ₄ ) ₄ A represents one or more elements selected from the group K and Na, and M represents one or more elements selected from the group W and Mo. D ₃ (BO ₃ ) ₄ D represents one or more elements selected from the group consisting of Al and Cr. _{P 5 O 14 A 3 (PO} 4) 2 A represents one or more elements selected K, from the group of Na. Na ₂ Mg ₂ (VO ₄ ) ₃ A ′ (MO ₄ ) ₂ A ′ is one or more elements selected from the group of Li, K, and Na, and M is one or more elements selected from the group of W and Mo. Represents the element.

In the formulas x and y, Z is A ₅ (M
When O ₄ ) ₄ , 0.25 ≦ x ≦ 0.99 and 0.1
Numerical value in the range of 1 ≦ y ≦ 0.75, Z is D ₃ (BO ₃ ) ₄
Then 0.10 ≦ x ≦ 0.99 and 0.01 ≦ y ≦
Numerical value in the range of 0.90, when Z is P ₅ O ₁₄ , 0.
Numerical value in the range of 0.05 ≦ x ≦ 0.98 and 0.02 ≦ y ≦ 0.95, and when Z is A ₃ (PO ₄ ) ₂ , 0.02 ≦ x
Numerical value in the range of 0.02 ≦ y ≦ 0.98 and ≦ 0.98, Z
Is Na ₂ Mg ₂ (VO ₄ ) ₃ , 0.57 ≦ x
Numerical value in the range of 0.01 ≦ y ≦ 0.43 when ≦ 0.90, Z
Is A ′ (MO ₄ ) ₂ , 0.20 ≦ x ≦ 0.9
5, the numerical value in the range of 0.05 ≦ y ≦ 0.80, specifically, the following values can be used.

Nd _0.8 Yb _0.2 Na ₅ (WO ₄ ) ₄ , N
d _0.9 Yb _0.1 Na ₅ (Mo ₄ ) ₄ , Y _0.1 Nd _0.75 Y
b _0.15 (WO ₄ ) ₄ , Nd _0.8 Yb _0.2 Na ₅ (Mo
_0.5 W _0.5 O ₄ ) ₄ , Bi _0.1 Nd _0.75 Yb _0.15 K
₅ (MoO ₄ ) ₄ , La _0.1 Nd _0.8 Yb _0.1 (Na
_0.9 K _0.1 ) ₅ (WO ₄ ) ₄ , Nd _0.9 Yb _0.1 Al ₃
(BO ₃ ) ₄ .

Further, an inorganic compound represented by the following general formula can also be used.

General formula EF _1-XY Nd _X Yb _Y P ₄ O ₁₂ E in the formula is at least one element selected from the group of Li, Na, K, Rb and Cs, and F in the formula is Sc and Y. , La,
Represents one or more elements selected from the group of Ce, Gd, Lu, Ga, In, Bi and Sb.

X and y in the formula are numerical values in the following range.

0.05 ≦ x ≦ 0.999 0.001 ≦ y ≦ 0.950 x + y ≦ 1.0 Specifically, the following can be used.

LiNd _0.9 Y _0.1 P ₄ O ₁₂ , LiBi
_0.2 Nd _0.7 Y _0.1 P ₄ O ₁₂ , NaNd _0.9 Y _0.1 P ₄
O ₁₂ .

Furthermore, an oxygen-containing acid such as a phosphate, borate, molybdate, or tungstate containing Yb and at least one element selected from the group of Y, La, Gd and Bi. Salts, specifically inorganic compounds having the following general formula, can also be used.

A in the general formula A (Y, La, Gd, Bi) _X Yb _1-X P _Y O _Z is one or more elements selected from the group of Li, Na, K, Rb and Cs, Not necessarily required.

X is a numerical value in the range of 0.1 to 0.9, y is a numerical value in the range of 4.2 to 5, and z is a numerical value in the range of 11 to 14.

The content of the fine phosphor powder is 10 to 80% by weight.
Is suitable, and particularly preferably 25 to 70% by weight. If the content of the phosphor fine powder is less than 10% by weight, the emission output of the latent image mark 2 is too weak, while the content of the phosphor fine powder is 80.
If the content exceeds 5% by weight, it is difficult to print and the adhesive strength is weak, so that the latent image mark 2 may be peeled off.

As the binder, a solventless type such as an ultraviolet curable resin, a solvent type such as polyurethane,
Alternatively, any water-soluble type such as polyvinyl alcohol (PVA) can be used, and the printing method or the detected object 1
It is appropriately selected according to the material of the. In addition, a plasticizer, a surfactant and the like are appropriately added as necessary.

In FIG. 1, 3 is a light emitting element such as an LED, 4 is a light projecting side optical fiber, 5 is a light receiving side optical fiber, 6 is an optical filter, and 7 is a light receiving element. The light emitting side optical fiber 4 and the light receiving side optical fiber 5 are integrally connected at the detection side facing the latent image mark 2 to form a coaxial cable.

In the case of this embodiment, the projection side optical fiber 4
The optical fiber made of glass having the same diameter is used for both the optical fiber 5 on the receiving side and the optical fiber element 4a on the projecting side is used more than the optical fiber element 5a on the receiving side as shown in FIG. The total area S1 is 1.2 to 4 times larger than the total light receiving area S2 (S1
> S2). Further, in the case of the present embodiment, a large number of light emitting side optical fiber elements 4a and light receiving side optical fiber elements 5a are arranged at random.

The following table shows the fluorescence when the detection area (total projected area S1 + total received area S2) is kept constant and the ratio (S1 / S2) of the total projected area S1 and the total received area S2 is variously changed. It shows the results of examining the output voltage of the body, the output voltage due to reflection, and the S / N.

Table S1 / S2 Output Voltage of Phosphor Output Voltage by Reflection S / N (mV) (mV) 0.2 8.8 4.16 2.1 0.3 0.3 10.4 4.36 2.4 0 .5 11.5 4.43 2.6 1.0 12.7 4.53 2.8 1.2 13.8 4.57 3.0 2.0 2.0 14.3 4.64 3.1 3.0 13.7 4.57 3.0 5.0 9.3 4.11 2.3 As is clear from this table, when S1 / S2 is less than 1.2, the phosphor is not sufficiently excited and fluorescence is emitted. Body output voltage and S / N are low, but S1 / S2 is 1.2-3.0
Then, the phosphor is sufficiently excited to obtain a high output voltage, and stable reading can be performed (S / N of 3 or more). Further, it is understood that when S1 / S2 is 5.0 or more, the total light receiving area S2 is substantially insufficient, and a sufficient output voltage cannot be obtained.

FIG. 5 is an emission spectrum diagram showing a curve a in the figure.
Is the emission spectrum of the light emitted from LiNdP ₄ O ₁₂ used as a phosphor, the curve b is the emission spectrum of the light emitting element 3 for exciting this phosphor, and the curve c is the light emitted from the light emitting element 3. 3 is a characteristic curve of the optical filter 6 having a property of cutting off and transmitting light emitted from a phosphor.

FIG. 7 shows the light emitting element 3 and the light receiving element 7.
In the figure, (a) of the figure shows the light emission timing of the light emitting element 3, and (b), (c) and (d) of the figure respectively show the output state of the light receiving element 7. It should be noted that FIGS. 7C and 7D are for explaining an afterglow detection method which will be described later, and the description thereof is omitted here, and a normal detection method using the filter 6 is shown in FIGS. This will be described using b).

As shown in (a) of FIG.
Both the lighting time T ₁ and the extinguishing time T ₂ are turned on and off at a time interval that is equal to a minute time (for example, 500 μsec), and the latent image mark 2 is intermittently irradiated with infrared rays. S ₁ in the figure indicates a lighting signal of the light emitting element 3.

Irradiation of infrared rays from the light emitting element 3 excites the fluorescent fine particles in the latent image mark 2 almost at the same time, and the fluorescent light emitted from the latent image mark 2 is received by the light receiving element 7, and the rectangular signal S ₂ Is obtained. The rectangular signal S ₂ is amplified by the amplifier 8 as shown in FIG.

Therefore, the light-emitting element 3 is turned on every minute time.
By repeatedly turning off the light, the barcode reading determination unit 9 can optically read the barcode information of the latent image mark 2.

FIG. 6 is an emission spectrum chart different from that of FIG. 5, and (d) in the figure is an emission spectrum when a light emitting element having a central wavelength of 805 nm is used. When a light emitting device having such a spectrum (d) is used, the optical filter 6 cannot be used because it partially overlaps with the emission spectrum (a) of the phosphor. In such a case, the afterglow detection method is suitable.

This afterglow detection method is shown in FIG.
This will be described with reference to (c) and (d). As described above, the light emitting element 3 is turned on and off at a time interval in which the lighting time T ₁ and the extinction time T ₂ are both very short, and intermittently irradiates the latent image mark 2 with infrared rays.

Irradiation from this light emitting element 3 causes latent image mark 2
The fluorescent fine particles therein are excited, and the light receiving element 7
Output increases. Even after the irradiation from the light emitting element 3 is stopped, the afterglow is emitted from the latent image mark 2, and the light receiving element 7 detects it. Since this afterglow S ₃ decreases with the passage of time as shown in FIG. 7C, a reference value Vs is set in advance, and a rectangle is formed immediately after the light emitting element 3 is turned off based on this reference value Vs. The signal S ₄ is obtained.

When such an afterglow detection method is adopted, the afterglow sharply decreases with the passage of time. Therefore, in order to reliably detect the afterglow, the amount of infrared rays projected onto the latent image mark 2 should be as large as possible. The means for increasing the light projecting area as in the present invention is particularly suitable for the afterglow detection method.

FIGS. 7 to 9 show the optical fiber 4 on the projecting side.
It is a figure which shows the modification of the light-receiving side optical fiber 5.

In the case of the first modified example shown in FIG. 7, a large-diameter light-receiving side optical fiber element 5a is arranged in the central portion of the coaxial cable, and a plurality of diameters smaller than the light-receiving side optical fiber element 5a are arranged on the outer periphery thereof. (Nine in this embodiment) the light emitting side optical fiber strands 4a are provided.

In the case of the second modification shown in FIG. 8, the light emitting side optical fiber element wire 4a and the light receiving side optical fiber element wire 5a having the same diameter are used.
Is used, three light receiving side optical fiber strands 5a are arranged in the central portion of the coaxial cable, and nine light emitting side optical fiber strands 4a are arranged around the light receiving side optical fiber strands 5a.
Is provided.

In the case of the third modification shown in FIG. 9, 1 is provided at the center.
The light-receiving side optical fiber strands 5a are arranged side by side, and the light-emitting side optical fiber strands 4a are arranged side by side in front and behind thereof.
The overall shape is rectangular.

Also in each of the above-mentioned modifications, the total projected area S1 for the latent image mark is designed to be larger than the total received area S2 for receiving the light emitted from the latent image mark (S1> S2). .

When an optical fiber is used as in this embodiment, it has the following features.

.. Due to the flexibility of the optical fiber itself, it can be easily inserted and installed even in a narrow space.

.. The latent image mark can be brought as close as possible.

.. The latent image mark can be detected even if the ambient temperature is relatively high.

.. Not affected by noise induction.

Materials for the light emitting side optical fiber element 4a and the light receiving side optical fiber element 5a include, for example, quartz (glass) type, quartz (glass) / plastic clad type, multi-component type, plastic type and the like.

FIG. 10 is a characteristic diagram showing the absorption band of the OH chemical bond in the optical fiber.
If there is an absorption band as shown in the same figure in the infrared region of 0 nm, the amount of transmitted infrared rays will decrease, resulting in a decrease in S / N when detecting a latent image mark. The absorption of this OH chemical bond is mainly found in plastic optical fibers,
As shown in FIG. 11, a quartz (glass) optical fiber has no infrared absorption band, has a high transmittance, and is almost constant, so that a quartz (glass) optical fiber is used for detecting latent image marks with a particularly small amount of fluorescent light. The optical fiber of is used.

In the above embodiment, the case of the infrared excitation type phosphor which is excited by irradiating infrared rays has been described. However, the present invention is applicable to an optical reading apparatus using an ultraviolet excitation type phosphor which is excited by irradiating ultraviolet rays. Is also applicable.

When comparing the ultraviolet-excited phosphor with the infrared-excited phosphor, the former is visible light while the latter is not visible light, which is advantageous in terms of security. Moreover, since the phosphor has a long life, the infrared-excitation type phosphor can be used as a prize.

[0067]

As described above, according to the present invention, under the condition that the detection area (light emitting area + light receiving area) facing the latent image mark is limited, the total projected area S1 of the latent image mark is set to the latent image mark. By making it larger than the total light receiving area S2 for receiving the light emitted from (S1> S2), the amount of light projected onto the phosphor can be increased and the phosphor can be sufficiently excited, so that a large output can be taken out and the reading error is reduced. As a result, the reliability can be improved.

[Brief description of drawings]

FIG. 1 is a side view of an optical reading device according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view taken along the line AA of FIG.

FIG. 3 is a diagram for explaining output states of a light emitting element and a light receiving element in the optical reading device.

FIG. 4 is a block diagram of the optical reading device.

FIG. 5 is an emission spectrum diagram.

FIG. 6 is an emission spectrum diagram.

FIG. 7 is a diagram showing a first modification of the light projecting side optical fiber and the light receiving side optical fiber.

FIG. 8 is a diagram showing a second modification of the light projecting side optical fiber and the light receiving side optical fiber.

FIG. 9 is a diagram showing a third modification of the light projecting side optical fiber and the light receiving side optical fiber.

FIG. 10 is a characteristic diagram showing an absorption band of OH chemical bond in an optical fiber.

FIG. 11 is a transmittance characteristic diagram of a silica-based optical fiber.

FIG. 12 is a side view of an optical reading device showing a first conventional example.

FIG. 13 is an enlarged plan view showing a relationship between a light projecting surface and a light receiving surface of the optical reading device.

FIG. 14 is a side view of an optical reading device showing a second conventional example.

FIG. 15 is an enlarged plan view showing the relationship between the light projecting surface and the light receiving surface of the optical reading device.

[Explanation of symbols]

 1 Object to be detected 2 Latent image mark 3 Light emitting element 4 Light emitting side optical fiber 4a Light emitting side optical fiber wire 5 Light receiving side optical fiber 5a Light receiving side optical fiber wire 6 Optical filter 7 Light receiving element 8 Amplifier 9 Bar code reading judgment section

Claims (9)

[Claims] 1. An optical reader for a latent image mark, which projects excitation light onto a latent image mark containing a fluorescent substance to optically detect light emitted from the latent image mark, wherein the latent image mark is projected onto the latent image mark. An optical reading device for latent image marks, wherein a total area S1 is larger than a total light receiving area S2 for receiving light emitted from the latent image marks (S1> S2). 2. The optical reading device for a latent image mark according to claim 1, wherein the light emitting element that projects light onto the latent image mark is an element that emits infrared light. 3. The optical reading device for a latent image mark according to claim 1, wherein the light projecting surface is provided on an outer periphery of the light receiving surface. 4. The optical reading device for a latent image mark according to claim 1, wherein the light projecting surface and the light receiving surface are randomly arranged. 5. The optical fiber is arranged between the latent image mark and a light emitting element that projects light to the latent image mark and a light receiving element that receives light emitted from the latent image mark. An optical reader for latent image marks, which is characterized in that 6. The optical reading device for a latent image mark according to claim 5, wherein the optical fiber has no light absorption band in a wavelength range of infrared rays. 7. The method according to claim 5 or 6,
An optical reader for a latent image mark, wherein the optical fiber is made of glass. 8. An optical reading of a latent image mark in which light is projected onto a latent image mark containing a phosphor to excite the phosphor, and then the projection is stopped to optically detect the afterglow of the phosphor. In the system, the total area S1 of light projected onto the latent image mark is larger than the total light receiving area S2 for receiving the light emitted from the latent image mark (S1> S2). 9. The latent image mark optical reading system according to claim 8, wherein the light emitting element that projects light onto the latent image mark is an element that emits infrared light.