JP2009129433A - Optical stealth bar code - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stealth bar code, which is not visible with visible light but is visible by making a phosphor emit light with invisible light such as ultraviolet rays, capable of being easily realized by using visible light instead of invisible light since a bar code record can be added without damaging design for an external appearance of a target object. <P>SOLUTION: To realize a record such as a bar code, a fine retro-reflective element to be used as a prism reflective sheet is dispersed and arranged on an invisible information record layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an invisible information recording body provided with an invisible information recording layer that is provided above a base layer and is difficult to view but is readable by a specific device.

Some conventional invisible information recording bodies are realized as a stealth barcode by a combination of invisible light such as ultraviolet rays and a phosphor (for example, see Patent Document 1). This is because the barcode is recorded with a phosphor that emits light by ultraviolet rays, and the barcode is not visible with visible light, thereby preventing the appearance of the barcode from being deteriorated.
JP-A-6-3095334

In the present invention, a stealth barcode is realized in visible light by using a retroreflective element in a barcode recording portion and reflecting light collected in a specific direction. Many retroreflective elements have been developed for prism sheets such as a corner cube type and a triangular prism type (refer to Patent Documents 2 and 3 in order), and micro-sized retroreflective elements that are difficult to view are also manufactured without problems.
JP-A-10-153701 Japanese Patent Publication No. WO 98/18028

In the conventional method, the phosphor is excited by invisible light to emit a recording pattern, so that an invisible light generator is necessary and expensive, and the short life of the phosphor is also a problem.

The present invention realizes reading of information such as a bar code with a specific device by dispersing minute prism retroreflective elements (hereinafter referred to as reflective elements) used for prism sheets and the like, making it difficult to visually recognize information recording such as barcodes. . Normally, the bar code display reads the diffusely reflected light, so the amount of light to be read is very small. On the other hand, if several percent of the area of the display portion is totally reflected, light stronger than the diffuse reflection can be read. Further, the reflecting elements are sufficiently small, and these are arranged in a white portion in accordance with the barcode pattern, so that only the background can be seen with the naked eye, and the reading device can read the barcode.
When light is incident, as shown in FIG. 1, there are regular reflections Va and Vb on the upper and lower surfaces of the transparent layer 13 having the reflective element 12, and the printed layer 11 having a pattern printed on the base layer 10 such as paper. There is diffuse reflection Vc, and there is total reflection Vd from the reflection element 12 applied to the lower surface of the transparent layer 13. Among these, the light returning to the incident light side is total reflection Vd by the reflection element 12 and diffuse reflection Vc of the printing layer 11. If there is a reading device on the incident light side and the light amount due to total reflection of the reflective element 12 is sufficiently larger than the light amount from diffuse reflection of the print layer 11, the reflection is performed as shown in FIG. If there is no element, the light does not return, so black, and if there is a reflective element, the light returns and is recognized as white.

Comparing the amount of diffused light from the printing layer 11 of FIG. 1 and the reflected light from the reflective element, the diffuse reflection N with respect to the point light source by the laser is the total luminous flux P, the reading area S, the distance L, the diffused light is Assuming uniform reflection in all directions, N = SP / πL ²
On the other hand, the reflected light M from the reflecting element that reflects in the range of the angle θ ° is D as the density of the reflecting element.
M = SPD / π (θ / 180) ² L ²
Therefore, the light quantity ratio N / M for contrast is N / M = (θ / 180) ² / D
For example, when the angle of the reflected light is focused within a range of ± 10 °, if the density D is 2.5% or more, the contrast N / M is 0.1 or less, that is, 2. on the white portion of the barcode. If the reflective elements are dispersed and arranged at a density of 5% or more, it functions as a barcode.

The condensing degree of the reflecting element is determined by the angle between the surface of the reflecting element and its accuracy, and the flatness of the surface. Conversely, if the angle between the surfaces is slightly shifted from 90 °, or the surface is uneven, the reflected light spreads.

Further, when the reflecting elements are arranged in a size of 0.1 mm or less and dispersed, they cannot be recognized with the naked eye. Actually, the minimum discrimination distance is determined by the density of light receiving nerve elements on the human retina and the angle with respect to the object, and a single object of 0.1 mm or less cannot be recognized with the naked eye even at a high density at a distance of 10 cm or more.

FIG. 3 shows a configuration diagram of the first embodiment. The laser beam from the laser light source 20 scans the barcode by the laser reflector 22. The reflective element 12 below the recording medium 13 with the stealth bar code is a corner cube type and is reflected toward the incident direction. The reflection from the reflective element 12 is “white” as a record, and there is no reflective element 12. However, it is determined as “black”. In general, the light receiver 20 is in the vicinity of the optical axis of the laser beam, and it is not necessary to reduce the light collection degree of the reflecting element 12 so much, and a corner prism having an apex angle of 90 ± 1 ° may be used.

FIG. 4 shows a part of the bar code, where the reflection element 12 is read as “white” and the absence is read as “black”. The pitch of the reflective elements 12 is 42.3 μm, the base of the triangular pyramid at the cube corner is 10.9 μm, the density is 2.5%, and it functions even if the reflected light from the reflective elements 12 returns to a wide range of ± 10 °. To do.

FIG. 6 shows a side view of the configuration of the barcode reader using the LED light source and the CCD sensor of the second embodiment, and FIG. 7 shows a front view thereof. Light that is not so concentrated from the plurality of LED light sources 20 is applied to the bar code, and reflected light from the reflecting element 12 is read by the CCD sensor 22 through the lens 23. Since the LED light source 20 has a plurality of LED light sources 20 in the horizontal direction, the reflection element may be formed by spreading the reflected light in the horizontal direction in order to maintain continuity and narrowed reflected light in the vertical direction. Therefore, the 90 ° triangular prism reflecting element 12 is horizontally arranged. Assuming that the condensing degree on the long axis side is ± 15 °, the condensing degree on the short axis side is ± 5 °, and the printed layer 11 is irradiated from an average of three LEDs, the contrast N / M has a density D of 6%. The above is 0.5 or less. Therefore, if the bottom surface of the reflective element 12 in FIG. 5 is a square and one side is 7.9 μm, it functions.

4 and 5, the pitch of the array of the reflective elements 12 is 42.3 μm, but there is no problem even if the pitch is further reduced. When the pitch is rough and the beam diameter of the laser beam is small, detection of the edge of the barcode becomes ambiguous.

Also, in order to support both LED barcode readers and laser beam barcode readers, it is also possible to mix the laser-compatible reflective element of FIG. 4 and the LED-compatible reflective element of FIG. It is.

As a barcode recording means, instead of forming a reflective element in the barcode pattern on the sheet from the beginning, a reflective element is placed on the entire surface of the barcode part, and the black part of the barcode is transparently cured in the subsequent process. It is effective to record a bar code by applying an agent or the like and invalidating the reflective function of the reflective element.

The invention's effect

Since the invisible recording medium according to this method cannot be seen, a barcode can be attached without damaging the appearance.

The present invention provides an invisible bar code display technology, and allows bar codes to be added to places where design is important, such as transparent objects, small objects, and display surfaces. Also, it is possible to provide a label in which a barcode function is added to a different design such as a logo instead of a barcode stripe pattern.

It is sectional drawing of the recording medium with a stealth barcode with respect to the laser beam of 1st Example according to the invisible information recording material of this invention. It is the figure which matched the reflective element of the white and black part of the barcode in the recording medium with a stealth barcode of FIG. It is a block diagram of the recording medium with a stealth barcode with respect to the laser beam of a 1st Example. It is a layout view of cube corner type reflective elements in the first embodiment. It is a layout view of a triangular prism type reflecting element in the second embodiment. FIG. 6 is a configuration diagram from the side in the second embodiment, showing the angle of light and the direction of the prism that can be used in the processing of vertical data of a barcode. In the block diagram from the front in a 2nd Example, the angle of the light and prism direction which can be put in the process of the horizontal data of several LED and barcode are shown.

Explanation of symbols

10. . . 10. Underlayer, . . Underprinting layer, 12. . . 12. prism retroreflective element; . . Transparent recording medium with stealth barcode,
20. . . Emission source, 21. . . Barcode reading optical system, 22. . . Laser reflector,
30. . . Barcode reader housing 31. . . LED light source, 32. . . CCD reading, 33. . . Condenser lens.

Claims (5)

A recording body in which more retroreflective elements are arranged in the white portion of the binary (monochrome) recording code. The recording body according to claim 1, wherein the retroreflective element is sufficiently small and the distribution thereof is sufficiently sparse so as not to impair the appearance design. A recording body and a method for manufacturing the same, wherein a retroreflective element is disposed on one surface of a recording code, and then the black retroreflective element is disabled, and the claim 1 or 2 is realized. A recording label having a transparent sheet structure using the recording code display technique according to claim 1. A recording label formed on paper using the recording code display technique according to claim 1.

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