JP2010044152A - Anti-forgery volume hologram - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission type anti-forgery volume hologram excellent in wavelength selectivity. <P>SOLUTION: The transmission type anti-forgery volume hologram having wavelength selectivity includes a first hologram 1', having a first surface 1a and a second surface 1b and comprising a Lippmann hologram; and a second hologram 2' having a third surface 2a and a fourth surface 2b and comprising a Lippmann hologram, disposed with the first surface 1a of the first hologram 1' and the third surface 2a of the second hologram 2' arranged opposite thereto, in which a first light beam 5' having a first wavelength is made to enter the first hologram 1' from the side of the second surface 1b, and is transmitted through the first hologram 1', exit the first hologram 1' from the side of the first substrate 1a, enter the second hologram 2' from the side of the third surface 2a and is diffracted by the second hologram 2'. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hologram, and more particularly to a transmission observation type forgery-preventing volume hologram imparted with wavelength selectivity suitable for forgery prevention.

  Holography is a technology that records both the amplitude and phase of a light wave on a surface, and a hologram produced by this technology is a three-dimensional image viewed from a different angle compared to a normal photograph that only captures an image viewed from a single point. It is possible to reproduce the image. Furthermore, because holograms are sophisticated in manufacturing technology, and the manufacturing equipment is complicated and expensive, it is generally difficult to forge or alter the hologram itself. Attempts have been made to use it as a means to prevent counterfeiting of securities.

  In addition, as a characteristic of general holograms, Lippmann holograms (volume type / reflection type holograms) have high angle selectivity and wavelength selectivity, and transmission type holograms (volume type and surface relief type) cause large color dispersion. Are known. FIG. 8 is a diagram showing the spectral transmittance distributions of the reflection type and transmission type holograms. As shown in FIG. 8, the reflection hologram has a high wavelength selectivity, and the transmission hologram has a low wavelength selectivity.

In order to replicate a hologram, advanced optical design technology and expensive equipment are required. However, a volume hologram is used as a master and the photosensitive material for replication is brought into close contact. In this case, replication is possible by irradiating a laser beam from the original side. Regarding this, for example, it has been proposed that duplication for counterfeiting can be prevented by dividing a hologram into element regions and changing the angle of reference light in each region (see Patent Document 1).
JP-A-8-123305

  However, the technique described in Patent Document 1 has a problem that it is difficult to mass-produce by volume irradiation with laser light or the like in order to distribute volume holograms to the market, and that it takes a lot of time for production.

  The present invention has been made in view of the above-described problems of the prior art, and its purpose is a transmission type forgery that is compact and inexpensive, has a simple structure but has high wavelength selectivity and is difficult to forge. It is to provide a volume hologram for prevention.

  The present invention that achieves the above object is a transmission-type anti-counterfeit volume hologram having wavelength selectivity, and includes a first hologram having a first surface and a second surface, comprising a Lippmann hologram, a third surface, and a fourth surface. A first hologram having a surface and a second hologram made of a Lippmann hologram, wherein the first surface of the first hologram and the third surface of the second hologram are arranged to face each other and have a first wavelength Light enters the first hologram from the second surface side, passes through the first hologram, exits the first hologram from the first surface side, and emits the second hologram from the third surface side. Entering the hologram, diffracted by the second hologram, exiting the second hologram from the third surface side, entering the first hologram from the first surface side, diffracted by the first hologram, First side The first hologram is emitted, incident on the second hologram from the third surface side, transmitted through the second hologram, and emitted from the fourth surface side, and the first wavelength. Second light having a different second wavelength is incident on the first hologram from the second surface side, passes through the first hologram, and exits the first hologram from the first surface side, The light enters the second hologram from the third surface side, passes through the second hologram, exits the second hologram from the fourth surface side, and the first light and the second light are: When the incident angles with respect to the first hologram are equal, the exit angles with respect to the second hologram are different.

  According to the present invention, it is possible to provide a transmission type anti-counterfeit volume hologram that is compact, inexpensive, has a simple structure, has excellent wavelength selectivity, and is difficult to forge.

  Hereinafter, a volume hologram having excellent wavelength selectivity and difficult to counterfeit while having a compact, inexpensive and simple structure will be described with reference to the drawings.

  In order to manufacture the forgery-preventing volume hologram of the present embodiment, first, the first Lippmann-type hologram 1 ′ is prepared. FIG. 1 is a diagram showing a method of producing a Lippmann-type first hologram 1 ′.

  The anti-counterfeit volume hologram 10 of the present invention is composed of two opposed Lippmann holograms. As the Lippmann hologram, a first hologram 1 'produced as shown in FIG. 1 and a second hologram 2' described later are used.

  First, as shown in FIG. 1, first object light 3 having a first wavelength is incident on a first hologram recording photosensitive material 1 such as a photopolymer or a silver salt material at a predetermined incident angle from the first surface 1a side. Make it incident. At the same time, the first hologram recording photosensitive material 1 is the same as the first object light 3 emitted from the same light source as the first object light 3 from the second surface 1 b side opposite to the incident side of the first object light 3. First reference light 4 composed of parallel light having a first wavelength or substantially parallel light is incident at a predetermined incident angle different from that of the first object light 3.

  Thus, the first object light 3 and the first reference light 4 interfere with each other by causing the first object light 3 and the first reference light 4 to enter the first hologram recording photosensitive material 1. Thereafter, the first hologram recording photosensitive material 1 is post-processed to produce a first hologram 1 '.

  In order to produce such a first hologram 1 ′, as the first hologram recording photosensitive material 1, a photopolymer was used for green. The laser and wavelength used for imaging are 532 nm of DPSS laser.

  FIG. 2 is a diagram showing a method for reproducing the first Lippmann-type hologram 1 '. When the first reproduction illumination light 5 traveling in the opposite direction to the first reference light 4 shown in FIG. 1 and including the first wavelength at the time of recording is incident from the produced first hologram 1 ′ first surface 1a side, The first reproduction light 6 traveling in the opposite direction to the first object light 3 in FIG. 1 is diffracted and emitted from the first surface 1a side.

  FIG. 3 is a diagram illustrating a method of manufacturing the Lippmann-type second hologram 2 ′. The second hologram recording photosensitive material 2 has a first wavelength of substantially the same incident angle as the first reference light 4 of the first hologram 1 ′, a second object light 3 ′ having substantially the same wavelength, and substantially parallel light, and a second object light. Second reference light 4 ′ having the same first wavelength as that used when recording the first hologram 1 ′ from the side opposite to the incident side of 3 ′ and substantially parallel light from the same light source as the second object light 3 ′. Then, the second object light 3 ′ and the second reference light 4 ′ are caused to interfere with each other, and the second hologram recording photosensitive material 2 is post-processed to produce a second hologram 2 ′.

  FIG. 4 is a diagram for explaining the configuration of the manufactured forgery prevention volume hologram 10 according to the first embodiment. The forgery-preventing volume hologram 10 is arranged such that the first surface 1a of the first hologram 1 'and the third surface 2a of the second hologram 2' face each other.

  When the second reproduction illumination light 5 ′ is incident from the second surface 1 b side of the first hologram 1 ′, the second reproduction illumination light 5 ′ passes through the first hologram 1 ′ and is secondly transmitted by the second hologram 2 ′. Diffracts the reproduction light 6 '. Here, since the emission angle of the second reproduction light 6 ′ is designed to be substantially equal to the incident angle of the reproduction illumination light 5 of the first hologram 1 ′, the first reproduction light is again emitted from the first hologram 1 ′. 6 is diffracted. The first reproduction light 6 is transmitted through the second hologram 2 'and emitted.

  As described above, the forgery-preventing volume hologram has a function as a transmission hologram that diffracts the second reproduction illumination light 5 ′ in the direction of the first reproduction light 6, and also has the wavelength selectivity of the Lippmann hologram. .

  Next, a design method of the forgery prevention volume hologram 10 of the present embodiment will be described. FIG. 5 is a diagram illustrating a design method of the volume hologram 10 for preventing forgery.

  First, as shown in FIG. 5A, a desired final emission angle of the present embodiment is determined. Next, as shown in FIG. 5B, an incident angle is selected such that it is not diffracted to the first hologram 1 ', which is the front hologram when viewed from the incident side.

  FIG. 6 is a diagram showing the incident angle dependence of the diffraction efficiency when the designed incident angle is 0 °. As shown in FIG. 6, the first hologram 1 ′ is diffracted to about ± 10 ° of the designed incident angle. Therefore, when selecting the incident angle to the first hologram 1 ′, the counterfeit-preventing volume hologram 10 is used. It is preferable to avoid within ± 10 ° of the desired emission angle.

  Next, as shown in FIG. 5C, a folding angle is selected such that the second hologram 2 ', which is a hologram at the back when viewed from the incident side, does not diffract the emitted light. Also in this case, as shown in FIG. 6, the second hologram 2 ′ is diffracted to about ± 10 ° of the designed incident angle. Therefore, when selecting the folding angle of the second hologram 2 ′, forgery prevention It is preferable to avoid ± 10 ° of the desired exit angle of the volume hologram 10.

  Thus, the produced forgery-preventing volume hologram 10 has the same function as a transmission hologram, is compact, inexpensive, has a simple structure, has excellent wavelength selectivity, and is counterfeit. It is excellent in prevention.

  Next, the case where it is going to forge this volume hologram 10 for forgery prevention is demonstrated.

  FIG. 7 is a diagram showing a case where the forgery-preventing volume hologram 10 is to be forged. As shown in FIG. 7, a replica hologram sensitive material 20 is arranged on the opposite side of the first hologram 1 ′ with respect to the second hologram 2 ′ of the forgery-preventing volume hologram 10, and reproduction illumination is performed from the first hologram 1 ′ side. A forged hologram was produced by irradiating with light 5 ′. Interference fringes generated by the reproduction light 6 and the transmitted light 8 are recorded on the counterfeit hologram sensitive material 20.

  The counterfeit hologram produced in this way becomes a conventional transmission hologram with large chromatic dispersion, and the difference between the counterfeit prevention volume hologram 10 with high wavelength selectivity according to the present invention can be recognized at a glance.

  With the hologram according to the present invention, for example, when recording was performed at a wavelength of 532 nm, it was possible to observe a green (near 532 nm) transmission reproduction image within a range of approximately ± 10 ° from the designed incident angle. In the case of a normal transmission hologram, since the angle selectivity is low, a transmission reproduction image can be seen at a wider range of incident angles, but a rainbow transmission transmission image was observed due to the influence of chromatic dispersion.

  As described above, the forgery-preventing volume hologram 10 of the present invention has been described based on the embodiments. However, the present invention is not limited to these embodiments, and various modifications are possible. For example, an adhesive layer or the like may be provided on the first hologram 1 ′ or the second hologram 2 ′ so that it can be attached to an adherend.

  When used as a label, for example, it has a structure such as a protective layer / hologram layer / adhesive layer, and is fixed by a desired substrate and adhesive layer. When used as a transfer foil, for example, it has a structure such as a protective layer / hologram layer / HS layer, and is fixed by a desired substrate and HS layer.

It is a figure which shows the method of producing the 1st Lippmann type hologram 1 '. It is a figure which shows the method of reproducing | regenerating the 1st Lippmann-type hologram 1 '. It is a figure which shows the method of producing the 2nd Lippmann type hologram 2 '. It is a figure for demonstrating the structure of Example 1 of the volume hologram for forgery prevention to which the produced wavelength selectivity was provided. It is a figure which shows the design method of the volume hologram for forgery prevention. It is a figure which shows the incident angle dependence of the diffraction efficiency when a design incident angle is 0 degree. It is a figure which shows the case where it is going to forge the volume hologram for forgery prevention. It is a figure which shows the spectral transmittance distribution of a reflection type and a transmission type hologram.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st hologram recording photosensitive material 1 '... 1st hologram 2 ... 2nd hologram recording photosensitive material 2' ... 2nd hologram 3 ... 1st object light 3 '... 2nd object light 4 ... 1st reference light 4 '... second reference light 5 ... first reproduction illumination light 5' ... second reproduction illumination light (first light)
6 ... 1st reproduction light 6 '... 2nd reproduction light 8 ... Transmission light (2nd light)
10 ... Volume hologram 20 for preventing counterfeiting ... Hologram sensitive material for counterfeiting

Claims (1)

In a transmission-type counterfeit volume hologram having wavelength selectivity,
A first hologram having a first surface and a second surface and comprising a Lippmann hologram;
A second hologram having a third surface and a fourth surface and comprising a Lippmann hologram;
Have
The first surface of the first hologram and the third surface of the second hologram are arranged to face each other,
The first light having the first wavelength is
Entering the first hologram from the second surface side, transmitting through the first hologram, and emitting the first hologram from the first surface side;
Entering the second hologram from the third surface side, diffracted by the second hologram, and emitting the second hologram from the third surface side;
Incident into the first hologram from the first surface side, diffracted by the first hologram, and exits the first hologram from the first surface side,
Entering the second hologram from the third surface side, transmitting the second hologram, and emitting the second hologram from the fourth surface side;
The second light having a second wavelength different from the first wavelength is
Entering the first hologram from the second surface side, transmitting through the first hologram, and emitting the first hologram from the first surface side;
Entering the second hologram from the third surface side, transmitting the second hologram, and emitting the second hologram from the fourth surface side;
The first light and the second light are:
An anti-counterfeit volume hologram, wherein when the incident angle with respect to the first hologram is equal, the emission angle with respect to the second hologram is different.

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