KR940011671B1 - Authenticity identifying system for information strorage card - Google Patents

Abstract

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Description

Verity Verification System for Information Storage Cards

1 is a perspective view of an essential part of a card and a card reader / writer in accordance with the first embodiment of the card authenticity determination system according to the present invention.

2 and 3 show similar perspective views showing second and third embodiments of the present invention, each having holographic regions.

4 and 5 are similar perspective views showing a fourth embodiment of the present invention in two different conditions.

FIG. 6 is a view similar to FIGS. 4 and 5 showing a fifth embodiment of the present invention for additional features of breaking certain portions of the confirmation area as required.

7 to 9 are partial cross-sectional views showing the operation of the fifth embodiment.

FIG. 10 is a view similar to FIG. 8 showing a sixth embodiment of the present invention. FIG.

11 to 13 are perspective views showing seventh to ninth embodiments of the present invention each having diffraction grating regions.

14 is a perspective view showing a tenth embodiment of the present invention having a large number of fine grooves formed in an information storage card.

15 is an enlarged plan view of a confirmation region of FIG.

FIG. 16 is an enlarged cross sectional view taken along the line VI-VI of FIG. 15; FIG.

FIG. 17 is a sectional view seen from the direction of arrows VII-VII of FIG. 14; FIG.

FIG. 18 is a view similar to FIG. 17 showing an eleventh embodiment of the present invention. FIG.

19 is a view similar to FIG. 15 showing a twelfth embodiment of the invention.

FIG. 20 is a view similar to FIG. 17 showing a light receiving element for a twelfth embodiment of the invention.

21 and 22 are views similar to those of FIG. 20 showing a light receiving element for a thirteenth embodiment of the present invention having a plurality of parallel grooves under two different conditions.

Figures 23 and 24 are similar figures 21 and 22, respectively, for a thirteenth embodiment of the present invention in which a diffraction grating region is used instead of a number of parallel grooves.

* Explanation of symbols for main parts of the drawings

1: Magnetic card 1a: Main surface

2: magnetic stripe 3: magnetic head

4 hologram area 5 light emitting element

6 lens 7 light receiving element

8: confirmation area

The present invention relates to a system for determining or verifying the authenticity of information storage cards by a reader / writer to prevent illegal manufacture or modification of the card. These information storage cards non-exclusively include magnetic cards capable of exchanging information with readers / writers, IC cards, optical cards, and the like. The invention also relates to cards with a confirmation area which cannot be easily duplicated, does not require unnecessary complexity of card readers / writers and can be easily identified.

Background Art Conventionally, for example, use of a lamination structure in a magnetic layer for the purpose of preventing forgery of a magnetic card, and drilling holes in a magnetic card when the magnetic card is not intended for repeated use has been performed. However, these structures are relatively easily copied or deceived by hijackers and are not sufficient to deter attempts to illegally copy or alter the card. The internal structure of the card may be further complicated by known means, resulting in increased complexity and cost of readers / writers for reading and writing into or from the card.

An additional problem that is expected to be met in preventing the forgery of such information storage cards is that the hijacker may be completely consumed and get a discarded information storage card, and because the remaining amount of the card is recorded as part of the information, the thief tries to cheat. May intentionally attempt to rewrite the extent stored on the card. In such a case, it is impossible in any conventional way to prevent illegal or unauthorized use of the card.

In view of these problems of the prior art, the main object of the present invention is to store information by means of specific identification which can be easily identified with a card reader / writer without increasing the complexity while making it difficult to duplicate by any unauthorized person. It is to provide a system for determining the authenticity of the card.

A second object of the present invention is to provide a system for determining the authenticity of an information storage card that prevents illegal rewriting of information contained in a true card with the intention of deceiving.

It is a third object of the present invention to provide an information storage card suitable for use in such a system.

These and other objects of the present invention can be achieved by providing a system for determining the authenticity of an information storage card, which system can store information in encoded form so that it can be accessed by the reader / writer of the card. An information carrier; A card having a confirmation area having unique optical characteristics in addition to the information carrier; And a reader / writer, the reader / writer comprising: light emitting means for projecting incident light onto a confirmation area of the card; Light-receiving means for detecting light reflected and transmitted by the confirmation region; And a confirmation circuit for evaluating the light received by the light receiving means and for generating a signal indicative of the authenticity of the card. The identification circuit may consist of a surface with special reflectivity as opposed to normal mirror reflections and diffuse reflections.

Thus, forgery of these cards has previously been so difficult that analysis or duplication of the confirmation area, which may consist of areas with inherent reflection or transmission optical properties such as holograms, diffraction gratings and multiple parallel grooves, is required. This is incredibly difficult. However, since the authenticity of the card can be easily achieved by providing one or more photosensitive light receiving means, it can be realized without increasing the complexity of the process for identifying the card.

To increase the complexity of the confirmation area to more effectively frustrate attempts to duplicate the confirmation area, the confirmation area may be comprised of multiple parts that may have different reflective properties or reflect incident light in multiple directions. Even if a single hologram confirmation area is used, if it contains two wavelengths of incident light from the light emitting device, the hologram area may reflect the incident light in two directions.

Practical procedures for determining or verifying the authenticity of a card can be accomplished by detecting the intensity received by the light receiving means, which can consist of a simple device such as a photodiode. If the reflected light is divided into multiple directions, a corresponding number of light receiving parts will be needed. According to a preferred embodiment of the present invention, the light receiving portions are arranged around the light emitting means along a common circle centered around the light emitting means. According to another embodiment of the present invention, the light receiving portions are arranged around the light emitting means along at least two circles concentric with the light emitting means.

In particular, if the card is a card that stores a certain value that is reduced by the use of the card to purchase goods or to receive a service, it is illegal for the card to be used up and discarded by rewriting information held by the card indicating the value remaining on the card. It is required to prevent the use of phosphorus. According to another embodiment of the present invention, the illegal use of such a spent card can be prevented by piercing, melting or otherwise destroying the verification area. If the confirmation area consists of multiple parts, for example, it is slow to destroy them successively depending on the degree of depreciation. Alternatively, the color destruction of other parts of the confirmation area can be used to code the information desired on the card.

The present invention also provides information storage cards comprising a confirmation area having inherent optical properties that can be detected by an optical sensor for use in the aforementioned system.

1 shows a schematic perspective view of a magnetic card 1 processed by a card reader / writer with means for verifying the authenticity of the card. The card 1 is conveyed by a conveyor roller or the like not shown in the direction indicated by the arrow as shown in FIG. 1, that is, substantially in the transverse direction, and when the magnetic head 3 has reached a certain position, the main portion of the card 1 Writing and reading are performed on the magnetic stripe 2 provided on the surface 1a.

The hologram area 4 is provided at a suitable position of the main surface 1a of the card 1. This hologram area 4 is composed of a reflective hologram having a specific wavelength and having reflective characteristics such that incident light transmitted perpendicular to the hologram is reflected in a specific predetermined direction.

The reader / writer includes a light emitting element 5 as a means for projecting a laser beam on the main surface 1a of the card 1, in particular perpendicularly to the hologram area 4, from a distance away. The lens 6 is interposed between the hologram area 4 and the light emitting element 5 to convert light emitted from the light emitting element 5 into a parallel beam directed towards the hologram area 4. Moreover, the light receiving element 7 composed of the photodiode is placed at a position to receive light emitted from the light emitting element 5 and reflected by the hologram area 4. The confirmation circuit 8 is connected to the light receiving element 7 to identify the authenticity of each card.

In performing this card checking process, the card 1 inserted into the card reader / writer is kept perpendicular to the illumination light from the light emitting element 5, and the illumination light or incident light from the light emitting element 5 is transferred to the hologram area ( 4) is projected on. The authenticity of the card 1 can be confirmed when the light reflected by the hologram area 4 is collected by the light receiving element 7 and its intensity is detected by the identification circuit 8 to be at a certain level. Thus, even if a counterfeiter gets such a card, it will be difficult for him to analyze and replicate the hologram, and it will be expensive to manufacture the same hologram. Therefore, this gives the counterfeiters a strong deterrent effect.

2 is a view showing a second embodiment of the present invention similar to that of FIG. 1, in which like parts are represented by like reference numerals without repeating their description in detail. Also, in the following description, some of the parts of the system, such as the magnetic head 3 and the confirmation circuit 8, are not shown to avoid complexity in the figures.

According to this embodiment, the hologram area 14 provided on the main surface 11a of the card 11 reflects the light emitted from the light emitting element 5 and directs it to two points. The light receivers 17 and 18 are provided at the positions of the card reader / writer corresponding to these points. Incident light emitted from the light emitting element 5 consists of simple divergent light in this case, but may also consist of light of parallel beams. According to this embodiment, the illumination light emitted from the light emitting element 5 and projected onto the hologram area 14 is received by the light receiving elements 17 and 18, and the card 11 receives the light receiving element 17 ( It is confirmed that it is true only when the intensities of the light received by 18 are each higher than a certain predetermined level. Therefore, this embodiment is similar to the first embodiment except that this embodiment is more effective than the first embodiment in preventing card forgery.

3 is a view similar to FIGS. 1 and 2, illustrating a third embodiment of the present invention. In this embodiment, the light emitting element 25 synthesizes a pair of light sources having different wavelengths, for example a device comprising a plurality of chips such as a laser device of two wavelengths having two light emitting surfaces in one package. Can be configured. The hologram area 24 on the major surface 21a of the card 21 is likewise designed to converge light at two different points according to the difference in wavelength. Furthermore, the light receiving element 27 is composed of a separate diode, for example, and has a pair of light receiving surfaces 27a and 27b positioned to correspond to two points at which light converges. Thus, according to this embodiment, the illumination light emitted from the light emitting element 25 and projected onto the hologram area 24 is received by the respective light receiving surfaces 27a and 27b, and the card 21 receives the light receiving surfaces. It is confirmed as true only when the intensities of the lights respectively received by (27a) and (27b) are all higher than a certain predetermined level. Otherwise this embodiment is similar to that shown in FIG. 1 and FIG.

4 and 5 show a fourth embodiment of the present invention. According to this embodiment, four hologram areas 34 to 37 are provided on the main surface 31a of the card 31. These hologram regions 34 to 37 are arranged such that each of the hologram regions 34 to 37 reflects the illumination light from the light emitting element 5 and converges it into two different points, each of which is per hologram region. It may be different. And four light receiving elements 38 to 41 are located at these points. For example, as shown in FIG. 4, the first hologram area 34 reflects the illumination light from the hologram area 5 to converge to the light receiving elements 38 and 39, or to FIG. As shown, the second hologram area 35 reflects the illumination light from the light emitting element 5 and converges to the light receiving elements 39 and 41 instead of the light receiving elements 38 and 39. Similarly, each of the other hologram regions 36, 37 reflects illumination light, converging the two reflected light associated among the light receiving elements 38-41.

According to this embodiment, not only is the forgery of the card more difficult, but also other applications are possible. For example, the reflected light from the hologram areas can be used as a coded signal associated with the state of the card, or other hologram areas can be used as camouflage or cover while one of the hologram areas confirms the authenticity of the card. May be used substantially.

Although the light receiving elements 38 to 41 have been composed of individual light receiving elements in the above embodiment, they may also be composed of one multi-region photodiode. The number of hologram areas and the number of light receiving elements are not limited to four, and the number of light receiving elements corresponding to the side of the card reader / writer and the desired number of hologram areas having different reflective properties on the surface of the card may also be provided. It is also possible.

Thus, according to the first to fourth embodiments, a hologram area having inherent reflection characteristics was formed on the surface of the card, the illumination light was projected onto this hologram area via a reader / writer, and the reflected light was at a predetermined position. Accepted by light-receiving means, the authenticity of the card was determined by the intensity of the reflected light. Therefore, the analysis of the hologram is very difficult, the duplication of the card is very expensive, and the forgery of the card is practically impossible. Moreover, since the identification of the card can be performed by simply projecting the illumination light onto the hologram area and sensing the intensity of the reflected light, the device required to be added to the reader / writer does not increase its size or complexity to a great extent.

6 to 9 show a fifth embodiment of the present invention which is similar to the fourth embodiment shown in FIGS. 4 and 5 but with additional features. In this embodiment, the punching machine 41 is placed in such a position that it can face each of the confirmation areas 34-37 when the card 31 is transported, and as required, Drill holes in each. The additional light receiving element 43 is provided so as to face the light emitting element 5 on the other side of the card 31 in cooperation with the light emitting element 5 to check whether the hole is drilled by the punching machine 41.

In this embodiment, the card 31 consists of a card whose value is reduced by each use until its value is completely consumed and the card becomes unusable. Information on the value held by the card is recorded as part of the information stored in the magnetic stripe 2. When the card 31 is used in a certain amount, for example, when purchasing an item having a certain amount of value, the hole 44 is opened by the punch 41a of the punching machine 41 shown in FIG. It drills in the confirmation area | region 34 of (31). Thereafter, the card 31 is moved to a position where the hole 44 and the light receiving element 5 oppose each other as shown in FIG. 9, and receives the illumination light from the light emitting element 5 through the hole 44. FIG. By projecting onto the element 43, it is identified whether or not a hole has been drilled in the confirmation area 34 to erase this confirmation area 34. When the value of the card is reduced by each predetermined value, the associated confirmation areas 34 to 37 are successively erased. FIG. 7 shows the light receiving elements 38 to 41 receiving light reflected by the hologram area, but the light receiving element 43 does not receive light from the light emitting element 5 due to the obstruction of the hologram area.

Thus, even if an attempt is made to rewrite the contents of the information stored on the magnetic card exhausted with the intention of increasing the value, the confirmation areas are already erased, and therefore are not confirmed as a reliable card, and thus cannot be used. Since the erased portions include holographic areas that are not easy to duplicate, the tricky use of the card is not possible by simply joining the erased portions, and it is possible to effectively prevent such rewriting of information storage cards.

FIG. 10 is a view similar to FIG. 8 showing a sixth embodiment of the present invention. In this embodiment, the confirmation areas 34-37 are erased by heating or melting them with the thermal head 45. This embodiment is similar to the fifth embodiment otherwise.

Therefore, according to the fifth and sixth embodiments of the present invention, illegal rewriting of the information carrier of the card can be effectively prevented by using a simple structure because the card can be made unavailable when the card is exhausted and discarded. And illegal rewriting of information stored on the card is not sufficient to make the card usable.

Referring to FIG. 11 showing the seventh embodiment of the present invention, the card 51 is conveyed in the direction indicated by the arrow, ie substantially laterally, as shown in FIG. 11 by a conveyor roller or the like not shown, and the magnetic head ( 53 writes to and reads from the magnetic stripe 52 provided on the main surface 51a of the card 51 when a certain position is reached. The diffraction grating region 54 is provided at an appropriate position on the main surface 51a of the card 51. The diffraction grating region 54 consists of many grooves having a density of hundreds of grooves per mm to thousands of grooves per mm, and is projected at an angle of incidence of θ1 and reflected incident light having a specific wavelength at a reflection angle of θ2 with respect to the incident light. Reflect with light.

The reader / writer includes a light emitting element 55 as a means for projecting laser light perpendicular to the main surface 51a on the diffraction grating region 54 from a certain distance away. This hologram area 55 projects the illumination light to the diffraction grating area 54 at an angle of θ1 when the card 51 is at the position indicated by solid lines in FIG. The lens 56 is interposed between the diffraction grating region 54 and the light emitting element 55 to convert light emitted from the light emitting element 55 into light of a parallel beam directed to the diffraction grating region 54. Moreover, the light receiving element 57 composed of the photodiode is placed at a position for receiving the light emitted from the light emitting element 55 and reflected by the diffraction grating region 54. The confirmation circuit 58 is connected with the light receiving element 57 to determine the authenticity of each card.

In carrying out this card verification process, the card 51 is inserted into the card reader / writer, and the illumination light from the light emitting element 55 is projected onto the diffraction grating area 54. The authenticity of the card 51 can be confirmed when the light reflected by the diffraction grating region 54 is collected by the light receiving element 57 and its intensity is detected by the identification circuit 58 as being of a certain level. Therefore, even when a counterfeit acquires such a card, not only is it difficult for him to analyze the diffraction grating, but also requires a huge cost to forge the same diffraction grating. Thus, it has a strong frustrating effect on potential counterfeiters.

FIG. 12 shows an eighth embodiment of the present invention and is similar to FIG. 11, in which like parts are denoted by like reference numerals without repeating the detailed description. According to this embodiment, the light emitting element 55 collects a pair of light sources having different wavelengths, for example, may be composed of a laser device of two wavelengths in which a plurality of chips are put in a single package. Moreover, a pair of light receiving elements 57 'and 58' are provided at positions angular at θ3 and θ4 with respect to the central axis of the illumination light, respectively, at a distance from the diffraction grating region 54 and at each wavelength of the illumination light. Corresponds to the Thus, according to this embodiment, the card 51 is confirmed to be authentic only when the intensities of the light respectively received by the light receiving elements 57 'and 58' are all higher than a certain predetermined level.

FIG. 13 shows a ninth embodiment of the present invention and is similar to FIG. 11 and FIG. In this embodiment, the diffraction grating region 54 provided on the main surface 51a of the card 51 is separated into two diffraction grating portions 54a and 54b having different reflection characteristics. The light receiving elements 57 ″ and 58 ″ respectively correspond to the diffraction grating portions 54 a and 54 b and have angles of θ 5 and θ 6 with respect to the central optical axis of the illumination light, respectively, and are separated from the diffraction grating region 54.

Thus, according to this embodiment, the illumination light emitted from the light emitting element 55 and reflected by the diffraction grating region 54 is received by the light receiving elements 57 "and 58", and the card 51 is Reliability is confirmed only when the luminosities received by the photoreceptors 57 "and 58" are all higher than a certain predetermined level, respectively. Thus, this embodiment has a stronger frustrating effect on potential thefters of the card. Otherwise, this embodiment is unique to the seventh and eighth embodiments.

Referring to FIG. 14 showing the tenth embodiment of the present invention, the card 61 is moved in the direction of the arrows shown in FIG. 14, that is, substantially in the lateral direction, by a conveyor roller or the like not shown in the drawings. The head 63 writes to and reads from the magnetic stripe 62 provided on the main surface 61a of the main surface 61 of the card 61 when it reaches a position. The confirmation area 64 is provided at an appropriate position of the main surface 61a of the card 61. As shown in FIG. 15 and FIG. 16, this confirmation area 64 consists of a large number of parallel V-shaped grooves 66 extending in the direction indicated by the dotted line R at a density of several grooves to several hundred grooves per mm. It is composed.

The reader / writer is a light emitting element 69 as a means for projecting laser light perpendicular to the main surface on the confirmation area 64 from a certain distance when the card 61 reaches the position shown by the solid line in FIG. ). A light receiving element 70 composed of a multi-region photodiode including a large number of light receiving surfaces 70a to 70h surrounding the light emitting element 69 is provided as shown in FIG. The confirmation circuit 71 is connected to the light receiving element 70 to determine the authenticity of each card.

In performing this card checking process, the card 61 inserted into the card reader / writer is kept perpendicular to the light emitting element 69, and the illumination light from the light emitting element 69 is projected onto the confirmation area 64. The authenticity of the card 61 is when the light reflected by the confirmation area 64 impinges on the light receiving surfaces 70a and 70e of the light receiving element 70 as shown in FIG. Since it is an elliptical extending perpendicular to the direction (of the dashed line R), it can be confirmed by comparing the positional relations of these light receiving surfaces (light receiving surfaces 70a and 70e) that receive high intensity light. Thus, even when a hijacker gets such a card, it is not only difficult for him to analyze the verification area, but also requires a huge cost to produce the same verification area. Thus, it is a strong frustration for potential thieves.

18 shows an eleventh embodiment of the present invention. In this embodiment, the confirmation region consists of a diffraction grating region having a large number of grooves at a density of thousands of grooves per mm, and the light from the light emitting element 69, for example on the portions 70a and 70e. It is designed to converge to light spots. This embodiment may be conveniently used for the embodiments shown in FIGS. 11 to 13.

19 and 20 illustrate a twelfth embodiment of the present invention and are similar to FIGS. 15 and 16, respectively. In this embodiment, the confirmation area 84 is the first set 85 of parallel V-shaped grooves 86 extending in the direction of the dotted line S and parallel V-shaped grooves extending in the direction of the dotted line T different from the preceding direction ( 88, which is a combination of the second set 87. Therefore, the authenticity of the card 61 is that the light reflected by the confirmation area 64 extends perpendicular to the directions (dotted lines S and T) of the grooves 86, 88 as shown in FIG. These light receiving surfaces (light receiving surfaces 70a, 70e, 70b, 70f) which collide with the light receiving surfaces 70a to 70h of the light receiving element 70 as a pair of elliptical patterns, which receive high intensity light. Can be identified by comparing the positional relationships of)). Otherwise, this embodiment is similar to the eleventh embodiment.

21 to 24 show a thirteenth embodiment of the present invention. According to this embodiment, the light receiving element 90 includes a first set 91 of light receiving surfaces 91a-91h and a second set 92 of light receiving surfaces 92a-92h surrounding the light emitting device 99. Include. Thus, this embodiment not only confirms the same identification patterns as those of the twelfth and twelfth embodiments as shown in FIGS. 21 and 22 by using multiple parallel grooves, but also addresses the difficulty in forging cards. Allow for larger changes in the verification patterns to increase. When the diffraction grating region is used instead of the grooves, corresponding spots of light are formed. For example, the light receiving surfaces 92a and 92e of the second set 92 on or around the light receiving elements 91a and 91e of the first set 91 of the light receiving element 90. Is formed as shown in FIG. 23 or FIG.

This embodiment also allows a certain amount of information to be individually written to and read from the identification area of the card from the normal carrier of the information of the information storage card.

Apparently, the present invention is not limited by the always embodiments, and there are other possible changes. For example, although illumination light is projected from the light emitting element in a confirmation area having a lens interposed in the above-described embodiments, mirrors and prisms may be located in the light path to change the direction of the light path. Although the photodiode has been used as the light receiving element in the above embodiments, a position sensing device PSD may also be used. The position sensing device is composed of a semiconductor device composed of i layer of high resistance Si, P layer formed on one surface or the light receiving surface, and n layer formed on the other surface of the i layer, and the position of the optical spot projected on the light receiving surface. Current proportional to is supplied from the electrodes provided on the light receiving surface. Furthermore, although the reflecting confirmation area is formed on the main surface of the card in the above embodiments, it is necessary to form a transmissive confirmation area by placing a similar area on both card faces or providing a transparent part of the card. It is possible.

Although the present invention has been described with respect to particular embodiments, it is possible to modify or change its details without departing from the spirit of the invention.

Claims (13)

A system for determining the authenticity of an information storage card comprising an information carrier capable of storing information in a form encoded to be accessed by a card reader / writer, wherein the information storage card is in addition to the information carrier and specified therein. A confirmation area composed of a hologram or a diffraction grating for reflecting / transmitting incident light in the direction of?, Wherein the reader / writer includes light emitting means for projecting incident light onto the confirmation area on the card; Light-receiving means having a plurality of light-receiving portions disposed separately in the circumferential direction of the light-emitting means capable of individually detecting the light intensity of the light reflected or transmitted by the confirmation region; And a confirmation circuit for evaluating the light received by any one of said light receiving means of said light receiving means and for generating a signal indicative of the authenticity of said card. 2. The system according to claim 1, wherein said confirmation circuit judges the authenticity of said card when the luminous intensity of light received by said light receiving means is higher than a predetermined level. 10. The system of claim 1, wherein the identification area is comprised of a plurality of parts that may have different reflective properties. The light emitting means and the light receiving means are positioned relative to the confirmation region so that light emitted from the light emitting means and reflected by the confirmation region can be selectively captured by the light receiving means. System. The system according to claim 1, wherein said light receiving means comprises a corresponding number of light receiving surfaces arranged to receive light reflected by said confirmation region. 2. The light emitting apparatus according to claim 1, wherein the incident light from the light emitting means carries at least four wavelengths, and the confirmation region has a reflection directivity for reflecting the incident light in different directions according to its wavelength, and the light receiving means has the confirmation light. And a corresponding number of light receiving surfaces arranged to receive light reflected by the region. 2. The system of claim 1, wherein the light receiving portions are disposed around the light emitting means along at least two concentric circles concentric with the light emitting means. 10. The system of claim 1, wherein the reader / writer is further provided with means for destroying the verification area if necessary. 9. A system according to claim 8, wherein said destroying means consists of a punching device. 9. A system according to claim 8, wherein said destroying means consists of a thermal head. 4. The system of claim 3, wherein the card reader / writer is further provided with means for destroying the confirmation areas one by one in accordance with the contents of the information stored in the information carrier. An information storage card having an information carrier capable of storing information in a form encoded to be accessed by a card reader / writer, and further having a confirmation area composed of holograms or diffraction gratings for reflecting / transmitting incident light in a specific direction. 13. The information storage card according to claim 12, wherein said confirmation area is composed of at least two parts which may have different reflectivity.

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