JPH10289295A - Information card - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it easier to enter light into a light guide and to prevent crosstalk from the light guide by composing the light incidence side light guide part of the light guide of a flat plate type light guide and the light projection side light guide part of the light guide of branch light guides which are optically branched. SOLUTION: The light incidence side light guide part 3a of the light guide 3 consists of the flat plate light guide and the light projection side light guide part 3b of the light guide 3 consists of the branch light guides which are optically branched. The flat plate light guide is provided on the light incidence side of the light guide 3, so the core 1 is larger in size than before, so an incidence window can be made large and even when the numerical aperture is made small, light is hardly made incident on the light guide 3. The projection side consists of the branch light guides formed optically branching the flat plate light guide, so the branch light guides are formed to desired size by making the numerical aperture small, thereby suppressing crosstalk on the projection side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information card for recording / reading information.

[0002]

2. Description of the Related Art Conventional information cards, such as prepaid cards, include a magnetic recording type in which information is recorded on a magnetic medium and a light detection type in which the presence or absence of a punch hole is detected by light. By the way, in the case of the magnetic recording system, when the recording system is decrypted, the information to be recorded is rewritten with different contents, so that the information is easily forged or altered. Also,
In the case of the light detection type, if the punched hole through which light passes is filled with a material through which light does not pass, the reader cannot detect the punched hole, so that the reader is easily forged or altered.

Therefore, an idea of an information card in which an optical waveguide such as an optical fiber is embedded has been proposed. As an example, JP-A-7-240089 can be mentioned. As shown in FIG. 6, this information card 41 of the optical waveguide system
An optical waveguide 43 made of an optical fiber in a cover 42
Are interposed at a predetermined number and at a predetermined interval. Recording of information is performed by providing a punch hole 44 in the optical waveguide 43 and dividing the optical waveguide 43, and the presence / absence and arrangement of the punch holes 44 become the contents of the information. The information is read by moving the information card 41 in the direction of the arrow, entering light from one end 43a of the optical waveguide 43 with the light emitting element 45, and detecting light emitted from the other end 43b with the light receiving element 46. Do. When the optical waveguide 43 has the punched holes 44, the emitted light is small, and when the optical waveguide 43 has no punched holes 44, the emitted light is large. Therefore, information is read by detecting the magnitude of the emitted light. In this information card 41 of the optical waveguide system, even if the punch hole 44 is filled with a transparent medium, it is difficult to transmit the original light amount to the light receiving element 46 on the detector side, so that forgery or falsification is difficult. It is.

[0004]

However, in the above-mentioned information card 41 of the optical waveguide system, the optical waveguide 13 is composed of a plurality of optical fibers, and the optical fiber has a numerical aperture (NA: the optical waveguide receives light). However, there is a problem that it is not easy to introduce light into individual optical fibers.

[0005] By the way, when the numerical aperture (NA) is increased, it becomes easier to guide light into the optical waveguide. However, when the NA is increased, the light is emitted in a state of being spread at the emission portion of the optical waveguide. Therefore, when the interval between the optical waveguides is small or when the distance from the exit end face of the optical waveguide to the detector is long, crosstalk occurs and the possibility of malfunctioning increases. Therefore, as a means for avoiding crosstalk, it is conceivable to move the detector closer to the light emitting end face of the optical waveguide.
However, as a result of experiments on an optical waveguide having an NA of 0.5, a core diameter of 80 μm, and an optical waveguide interval of 1 mm, in order to prevent crosstalk, the distance between the detector and the exit end face of the optical waveguide must be suppressed to 0.8 mm or less. I found it. However, the distance between the detector and the exit end face of the optical waveguide is 1 m.
It is difficult to reduce the length to m or less in consideration of the card insertion / removal mechanism of the reader, and the card may hit the detector and damage the detector. As described above, the NA on the optical waveguide output end side must be reduced.

On the other hand, when the NA of the optical waveguide is reduced, it becomes difficult to make light incident on the optical waveguide. That is, the spread part of the light emitted from the light emitting source cannot be coupled to the optical waveguide, and the loss at the time of coupling becomes large. In order to avoid this, there are methods such as focusing the incident light with a lens,
Considering the accuracy required for the incident optical system, the cost is high, so that it is not practical.

The difference between the optical waveguide and the communication optical waveguide in the information card is the relative positional accuracy between the optical waveguide and optical elements provided before and after the optical waveguide. In the case of a communication optical waveguide, the optical axis before and after the optical waveguide, for example, with an optical fiber bar is fixed with an accuracy on the order of μm. However, since the reader of the information card reads the moving information card, if the accuracy of the reader is increased, the cost becomes high and it becomes impractical. SUMMARY OF THE INVENTION An object of the present invention is to provide an information card capable of easily making light enter an optical waveguide and preventing crosstalk of light emitted from the optical waveguide.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the invention according to claim 1 is an information card having an optical waveguide in which both surfaces of a sheet core are covered with cladding layers. Wherein the light incident side optical waveguide portion of the optical waveguide is formed of a plate-shaped optical waveguide, and the light emission side optical waveguide portion of the optical waveguide is formed of a plurality of optically branched optical waveguides. It is characterized by the following. Also,
According to a second aspect of the present invention, in the first aspect of the present invention, the optical waveguide is tapered in the light propagation direction. Further, the invention according to claim 3 is the invention according to claim 1 or 2, wherein the cladding layer of the optical waveguide is two layers, and the outer cladding layer is added with at least a light scattering material or a light absorbing material. It is characterized by having.

According to the first aspect of the present invention, since the light incident side of the optical waveguide forms a flat optical waveguide, the size of the core becomes larger than before and the entrance window can be enlarged. Even if the NA is reduced, light easily enters the optical waveguide. Further, the output side is composed of a plurality of branched optical waveguides obtained by optically branching a flat optical waveguide.
Is reduced, the size of the branch optical waveguide can be set to a desired size, and crosstalk on the emission side can be suppressed. Therefore, when the information card of the present invention is used, it is not necessary to stop the incident light with a lens or the like, and even if the optical axis is slightly shifted, the light can be guided into the optical waveguide. Since there is no need to bring the reader close to the information card, the reader can be made inexpensive.

According to the second aspect of the present invention, since the optical waveguide is thicker on the light incident side than on the light exit side, the coupling loss at the light incidence can be further reduced.

Furthermore, in the third aspect of the present invention, since at least a light scatterer or a light absorber is added to the cladding layer outside the two cladding layers, the cladding layer leaks from the core of the branch optical waveguide. Since the light does not propagate as it is through the cladding layer and exits to the end face on the emission side, or recombines with the core of another branch optical waveguide on the way, errors in reading information are reduced.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. (Embodiment 1) FIGS. 1A to 1C are a light incident side view, a plan view, and a light exit side view of an information card according to an embodiment of the present invention. In the figure, an optical waveguide 3 comprises a core 1 and a cladding layer 2. Reference numeral 4 denotes a white thermosetting epoxy adhesive containing a filler serving as a light scatterer, and reference numeral 5 denotes a surface cover made of a polycarbonate sheet. The adhesive 4 also has a function of a clad layer containing a filler as a light scattering body. The core 1 is obtained by cutting a polycarbonate sheet having a thickness of 80 μm. The end face 1a on the incident side has a rectangular shape with a thickness of 80 μm and a width of 5 cm. The emission side is branched, and the end face 1b has an 80 μm square. The shapes are arranged at 1 mm intervals. In addition, the cladding layer 2
Is a transparent epoxy acrylate paint. That is, the light-incident-side optical waveguide portion 3a of the optical waveguide 3 forms a flat-plate optical waveguide having a rectangular cross section, and the light-emitting-side optical waveguide portion 3b includes a plurality of spatially (and thus optically) branched optical waveguides. Of the branched optical waveguides.

The information card 6 of the embodiment is manufactured as follows. That is, first, as shown in FIG. 2 (a), a polycarbonate sheet having a thickness of 80 μm is punched out at a plurality of locations in a V-shape at intervals of 1 mm to form a branch portion 7 a having a width of 80 μm, thereby forming a core member 7. . This core member 7
Then, a transparent epoxy acrylate paint to be the clad layer 2 is applied to the core member 7, and then the core member 7 is sandwiched by the front cover member 8 while sandwiching the adhesive 4, and the adhesive 4 is cured. Next, as shown in FIG. 2B, the incident side end 6a and the exit side end 6b are cut and formed into an information card 6. The NA of the information card 6 formed in this way
Was 0.2.

(Embodiment 2) FIG. 3 is an exploded perspective view of a second embodiment. In the present embodiment, the thickness of the optical waveguide is tapered in the light propagation direction. That is, in FIG. 3, the core 11 is made of diethylene glycol bisacryl carbonate (CR-3) by a casting polymerization method.
9). The shape of the core 11 is the end face 11 on the incident side.
a is a rectangle having a thickness of 200 μm and a width of 5 cm;
1 has a tapered shape, and the branched emission-side end faces 11b are 80 μm square and arranged at 1 mm intervals. The core 11 is coated with a transparent thermosetting silicone-based paint to be a primary clad layer (not shown). The core 11 is sandwiched by a surface cover 15 made of a polycarbonate sheet while sandwiching a black thermosetting acrylic adhesive 13 containing a carbon filler (light absorber) serving as a secondary clad layer. The NA of this information card 16 was 0.2.

(Embodiment 3) In the present embodiment, the light emitting side optical waveguide portion of the optical waveguide is optically branched, but is not spatially branched. That is, the core 21
As shown in FIG. 4, a ridge waveguide is formed of polycarbonate as a light emitting side optical waveguide portion using a hot press method. The shape of the core 21 is such that the incident-side end face 21a is a rectangle having a thickness of 300 μm and a width of 5 cm, the thickness thereof is tapered, and the cross-section of the optically branched exit-side end face 21b is ridged. Size is 80μ
It is m-square and those of this shape are arranged at 1 mm intervals. The core 21 is coated with an acrylic transparent paint to be a primary clad layer, and then sandwiched with a black thermosetting epoxy adhesive filled with a carbon filler to be a secondary clad layer, with a surface cover made of a polycarbonate sheet. After sandwiching the core 21 and curing the adhesive, the end face was molded to obtain an information card. NA of this information card
Was 0.25.

A reading test was performed on the information cards of the first to third embodiments as follows. That is, a red LED is used as the light emitting element, and the light receiving surface is 5 light receiving elements.
A mmφ PD was used. The optical axes of the LED and the PD were aligned horizontally, and the information card was deviated from the optical axis and intentionally passed through a space 2 mm below the optical axis. The distance between each optical element and the end face of the card is 2 m in the horizontal direction.
m. These information cards were moved at the same speed as a general reader while emitting light from the LED, and the light reception signal at the PD was converted into a voltage and observed using an oscilloscope. As a result, it is possible to count the same number of light receiving pulses as the number of the plurality of branched optical waveguides that are the light emitting side optical waveguide parts, and then punch a hole in an arbitrary position of the branched optical waveguide on the emitting side. When the test was performed in the same manner as described above, the received light pulse at the place where the punched hole was formed was not counted. From this, it was confirmed that even if the information card deviated from the optical axis, the detection light could be introduced into the optical waveguide, and that there was no crosstalk.

In Comparative Example 1, the core shape was changed in the structure of Embodiment 1, and a polycarbonate sheet having a thickness of 80 μm was formed into a blind having a width of 80 μm and cut into a core. . That is, as shown in FIG. 5, the light incident side optical waveguide portion 31a and the output side optical waveguide portion 31
b, the information card 32 having the same cross-sectional shape of 80 μm square
Was prepared. The NA of Comparative Example 1 was 0.2. Also,
As Comparative Example 2, in Comparative Example 1, the paint to be the clad layer was a transparent acrylic paint. The NA of Comparative Example 2 was 0.5. Embodiment 1 for Comparative Examples 1 and 2
A reading test was carried out in the same manner as in Examples 3 to 3. As a result, in Comparative Example 1, no light was received. This is because NA is the first embodiment
This is because the area of the light receiving surface is small. In Comparative Example 2, crosstalk occurred. This is NA
Is larger than in the first to third embodiments.

[0018]

According to the structure of the present invention, there is provided an excellent effect that the detection light can easily enter the optical waveguide and that the crosstalk of the light emitted from the optical waveguide can be prevented. The deviation of the optical axis of the reader can be tolerated to some extent, and the card reader can be made inexpensive.

[Brief description of the drawings]

1 (a) to 1 (c) are a light incident side view, a plan view, and a light exit side view of an embodiment of the present invention, respectively.

FIGS. 2A and 2B are diagrams illustrating a manufacturing process of the embodiment.

FIG. 3 is an exploded perspective view of another embodiment of the present invention.

FIG. 4 is a perspective view of a core used in still another embodiment of the present invention.

FIG. 5 is a plan view of a comparative example.

FIG. 6 is an explanatory diagram of a conventional information card.

[Explanation of symbols]

 1, 11, 21 Core 1a, 1b, 11a, 11b, 21a, 21b End face 2 Cladding layer 3 Optical waveguide 3a, 31a Light incident side optical waveguide section 3b, 31b Light emission side optical waveguide section 4, 13 Adhesive 5, 15 Front cover 6, 16, 32 Information card 6a, 6b End 7 Core member 7a Branch 8 Front cover member

Claims (3)

[Claims] 1. An information card having an optical waveguide in which both surfaces of a sheet-shaped core are covered with cladding layers, wherein a light-incident-side optical waveguide portion of the optical waveguide comprises a flat optical waveguide. An information card, characterized in that the light emitting side optical waveguide section comprises a plurality of optically branched optical waveguides. 2. The optical waveguide according to claim 1, wherein the thickness of the optical waveguide is reduced in a tapered shape in a light propagation direction.
Information card described. 3. The information according to claim 1, wherein the cladding layer of the optical waveguide has two layers, and the outer cladding layer is added with at least a light scatterer or a light absorber. card.