JP4849252B2 - Method for producing security hologram - Google Patents

Description

  The present invention relates to a method for producing a security hologram, and more particularly to a method for producing a hologram in which authentication information that is difficult to observe in a normal observation state is recorded.

  A small object, which is the authentication information, is placed behind a shielded object that can be easily recognized by the naked eye.In the observation in a predetermined direction, the authentication information is shielded by the shielding object and cannot be observed. Patent Document 1 proposes a security hologram recorded so as to be observable from the direction.

  In the security hologram described in Patent Document 1, a minute object placed behind a shielding object is recorded as a computer-generated hologram (CGH) that has been subjected to hidden surface removal processing. In order to record this minute object by two-beam interference, the incident range of the object light from the minute object on the hologram surface is restricted by a mask, but the details are not disclosed.

By the way, when recording a hologram of an actual subject, it is common to irradiate illumination light obliquely forward of the subject, for example, from the celestial direction, and record reflected diffused light from the subject as object light.
JP 2003-228270 A JP-A-9-319289

  When the subject is illuminated by the conventional method as described above, the subject becomes a shadow on a minute object placed at a position hidden behind the subject, and the minute hidden behind the subject by illumination light obliquely forward from the subject. The object cannot be illuminated.

  It is known to illuminate a subject with a plurality of illumination lights in order to reduce shadows due to unevenness of the subject (Patent Document 2), and illuminate a minute object at a position that is a shadow of the subject with another illumination light. However, it is necessary to use as many illumination lights as the number of minute objects. In this case, since the minute object is illuminated from the recording material side, the entire minute object is irradiated with illumination light, and reflected diffused light is also generated from the black portion of the minute object, and the recorded hologram The contrast of the image of the minute object reproduced from the image becomes worse.

  The present invention has been made in view of such a situation in the prior art. The purpose of the present invention is to place a minute object, which is authenticity determination information, behind a shielding object, and for observation in a predetermined direction, the minute object is a shielding object. It is an object of the present invention to provide a method for producing a security hologram which is shielded and cannot be observed and is recorded so as to be observable from another direction different from the predetermined direction.

In the method for producing a security hologram of the present invention that achieves the above object, a minute object is placed behind a shielding object having a size that can be easily recognized with the naked eye. It is not possible to create a security hologram that is recorded so as to be observable from another direction different from the predetermined direction,
A hologram photosensitive material is disposed on the opposite side of the shielding object from the minute object,
The shielding object is illuminated with illumination light incident from the hologram photosensitive material side,
The minute object is recorded as a transmissive or reflective hologram by illuminating with illumination light incident from the opposite side of the hologram photosensitive material.

  In this case, it is desirable that the minute object is drawn as a transparent pattern on an opaque background or drawn as an opaque pattern on a transparent background.

  Moreover, it is desirable that the maximum dimension of the minute object is 300 μm or less.

  In addition, a reproduction image of the minute object and the shielding object is reproduced from the hologram recorded as the transmission type or reflection type hologram, and a volume hologram photosensitive material is arranged in the vicinity of the reproduction image position so that it can interfere with reproduction illumination light. Reference light from the same light source can be incident from any direction and recorded as a volume hologram in the volume hologram photosensitive material.

  According to the method for producing a security hologram of the present invention, a minute object as authentication information is placed behind a shielding object having a size that can be easily recognized by the naked eye, and the authentication information is shielded by the shielding object in observation in a predetermined direction. Thus, a security hologram recorded so as to be observable from a different direction different from the predetermined direction can be easily produced using an actual real object. Since the minute object is illuminated with illumination light incident from the opposite side of the hologram photosensitive material, the minute object can be recorded as a high-contrast hologram, and a minute object such as a micro character that requires more contrast can be easily obtained. Can be recorded.

  In the present invention, a micro object such as a micro character that is difficult to resolve with the naked eye is placed behind an opaque large object such as a model, and the micro object is shielded by a large object when viewed from the front of the large object, for example. This is a method for producing a hologram, in which an object is arranged as a hologram by actual light beam interference so that the minute object can be observed without being shielded by the large object when viewed from an oblique front, for example. The hologram thus produced can be used as a security hologram.

  Hereinafter, a method for producing a security hologram according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a method for producing a hologram according to the present invention. The hologram photosensitive material 1 made of a silver salt material or a photopolymer faces a large opaque object 2 such as a model, and the hologram photosensitive material 1 side. The minute objects 2 ′ and 2 ″ are arranged behind the large object 2 so that they can be seen from obliquely forward. The large object 2 is illuminated by the illumination light 4 from obliquely forward on the hologram photosensitive material 1 side. The objects 2 ′ and 2 ″ are illuminated from the back direction opposite to the hologram photosensitive material 1 by another illumination light 4 ′. When the hologram is manufactured as a transmission type, the object 2 is viewed from the upper oblique direction on the side where scattered light from the objects 2, 2 ′, 2 ″ is incident (in the case of FIG. 1). Reference light 3 is incident from the side opposite to 2 ′, 2 ″, light reflected and scattered from the large object 2, and light that is transmitted and scattered through the minute objects 2 ′, 2 ″ and is not shielded by the large object 2 Is recorded in the hologram photosensitive material 1. The reference beam 3 and the illumination beams 4, 4 'are coherent beams branched from the same beam.

  Here, the large object 2 may be any opaque object such as a model that can be visually observed. For example, the large object 2 may be a cube as shown in FIG. When producing a hologram for security, it consists of micro characters etc. that are difficult to resolve with the naked eye, but is drawn as a transparent pattern on an opaque background, for example, as shown in FIGS. 2 (b) and 2 (c) Or micro characters drawn as an opaque pattern on a transparent background.

  Such a large object 2 and minute objects 2 ′, 2 ″ are arranged as shown in FIG. 1 and illuminated with illumination light 4, 4 ′, respectively, and hologram 1 photographed as a transmission type or a reflection type on hologram photosensitive material 1. When the reproduction illumination light 6 that travels in the same direction as the reference light 3 at the time of photographing is incident from the same side as at the time of photographing the hologram 1, the diffraction light from the hologram 1 As shown in FIG. 3, the reproduced image 7 of the large object 2 is positioned at the relative position of the large object 2 with respect to the position of the hologram 1, and the small objects 2 ′ and 2 ″ are reproduced at the relative positions of the small objects 2 ′ and 2 ″. Images 7 ′ and 7 ″ are reproduced as virtual images.

  When the hologram 1 is observed from the direction of the large arrow in FIG. 3, reproduced images as shown in FIGS. 4 (1) to 4 (5) are observed according to the observation positions (1) to (5). . That is, when viewed from the front position (3) of the hologram 1 produced, the reproduced images 7 ′ and 7 ″ of the minute objects 2 ′ and 2 ″ are hidden behind the reproduced image 7 of the large object 2 and cannot be seen. 1 (upward in FIG. 3) from the front of FIG. 1 to the position (2) → (1), the reproduced image 7 ″ (“ B ") appears and the whole becomes visible. On the other hand, when going from the front of the hologram 1 downward (downward in FIG. 3) to the position (4) → (5), the reproduced image of the minute object 2 ′ on the lower side from the reproduced image 7 of the large object 2 is reproduced. 7 ′ (“A”) appears, and the whole becomes visible.

  Therefore, by using micro characters having a maximum dimension of 300 μm or less that are difficult to resolve with the naked eye as the minute objects 2 ′ and 2 ″, the minute objects 2 ′ and 2 ″ cannot be seen from the normal observation direction (front direction). In addition, since it is not visually recognized that such a minute object 2 ′, 2 ″ is recorded even if it goes around in the left-right direction or the up-down direction, it is a minute information that is authentication information from the normal observation direction, for example, from the front. Since it is difficult to notice the presence of the images 7 ′ and 7 ″ of the objects 2 ′ and 2 ″, the confidentiality of the authenticity determination information is further increased and the risk of forgery is reduced. Then, the authenticity of the hologram 1 is determined. When illuminating, the hologram 1 is irradiated with appropriate illumination light 6 and magnified using a loupe or the like, and in a predetermined direction other than the front (directions (1), (2), (4), (5) above) ) If you observe from), authenticity judgment information (Images 7 ′, 7 ″ of the minute object 2 ′, 2 ″) appear, and when the observation position is moved to the front in the normal direction, the authenticity determination information is hidden behind the image 7 of the large object 2. It can be confirmed by disappearing.

  Here, in the hologram manufacturing method of the present invention, the minute object 2 ′, 2 ″ that is blocked by the large object 2 and cannot be observed in the normal observation state is not illuminated from the front in the same manner as the large object 2, but the minute object. 2 ', 2 "itself is composed of micro characters drawn using an opaque pattern on a material that transmits the hologram recording wavelength, and recording is performed with light transmitted and scattered forward by irradiating illumination light 4' from the back side. Thus, it is possible to record the minute objects 2 ′, 2 ″ as a high-contrast hologram. Further, in this way, the minute objects 2 ′, 2 ″ arranged at a position that is a shadow of the large object 2 can be recorded. By illuminating from the back, it is also possible to record the minute objects 2 ′ and 2 ″ arranged at a hidden position on the back of the shielding object (large object) 2.

  By the way, the hologram 1 recorded as a transmission type or a reflection type as described above may be used as a security hologram, but the reproduced images 7, 7 ′, 7 ″ reproduced from the hologram 1 are again used as volume holograms. By recording, a hologram with higher security can be obtained, and one example of the manufacturing method is shown in FIG.

  In FIG. 5, the hologram 1 is the hologram 1 photographed in the arrangement of FIG. 1, and when the reproduction illumination light 6 ′ traveling in the opposite direction to the reference light 3 at the time of recording is recorded on the hologram 1. Is incident from the side opposite to the side on which the reference beam 3 is incident, the diffracted light from the hologram 1 at the same position as the relative position of the objects 2, 2 ′, 2 ″ at the time of recording with respect to the surface of the hologram 1 Reconstructed images 7, 7 ′, 7 ″ are reproduced as real images. A volume hologram photosensitive material 10 such as a photopolymer is arranged in the vicinity of the position where the reproduced images 7, 7 ′, 7 ″ are formed, and a reference light composed of parallel light from the same light source that is coherent with the reproduced illumination light 6 ′. 11 is simultaneously incident at an arbitrary incident angle from the side opposite to the side where the diffracted light from the hologram 1 is incident (in the case of FIG. 5) or the same side, and is exposed as a second-stage hologram in the volume hologram photosensitive material 10. Here, the photosensitive material 10 and the second-stage volume hologram 10 are denoted by the same reference numeral 10.

  As shown in FIG. 6, the reproduction illumination light 12 traveling in the opposite direction to the reference light 11 at the time of recording on the second-stage volume hologram 10 recorded as described above is referred to at the time of recording on the volume hologram 10. When incident from the side opposite to the light 11, the reconstructed image 7 of the large object 2 and the reconstructed images 7 ′ and 7 ″ of the minute objects 2 ′ and 2 ″ are relative to the original objects 2, 2 ′ and 2 ″ by the diffracted light. It is played while keeping the position.

  When the volume hologram 10 is observed from the direction of the large arrow in FIG. 6, a reproduced image as shown in FIG. 4 is observed according to the observation position, as in the case of FIG. Therefore, similarly to the hologram 1, since it is difficult to notice the presence of the images 7 ′ and 7 ″ of the minute objects 2 ′ and 2 ″ that are normal determination directions from the front, for example, from the front, Confidentiality is further increased and the risk of counterfeiting is reduced. Then, when trying to determine the authenticity of the hologram 1, it is magnified using a magnifying glass or the like, and is observed from a predetermined direction other than the front, and authenticity determination information (the image 7 ′ of the minute object 2 ′, 2 ″, 7 ″) appears, and when the observation position is moved to the front in the normal direction, it can be confirmed that the authentication information is hidden behind the image 7 of the large object 2 and cannot be seen.

  In the case of the volume hologram 10, since it is recorded as a volume hologram, the reproduced images 7, 7 ′, 7 ″ can be observed even under natural light, and forgery is more difficult than the normal relief type. There is an advantage that security is higher than that of the hologram 1.

  As described above, the method for producing a security hologram of the present invention has been described based on the embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made.

It is a figure which shows the preparation methods of the hologram of this invention. It is a figure which shows the example of the big object and minute object which are used by arrangement | positioning of FIG. It is a figure which shows the object reproduced | regenerated from the produced hologram, and an observation position. It is a figure which shows the reproduction | regeneration image observed according to the observation position of FIG. It is a figure which shows one Example of the method of recording as a volume hologram again. It is a figure which shows the object reproduced | regenerated from a volume hologram.

Explanation of symbols

1. Hologram photosensitive material (hologram)
2 ... Large object (shielded object)
2 ', 2 "... micro object (authentication judgment information)
3 ... Reference light 4 ... Illumination light 4 'for large objects ... Illumination light 6 and 6' for minute objects ... Reproduction illumination light 7 ... Reconstructed image 7 ', 7 "for large objects ... Reconstructed image 10 for minute objects ... Volume hologram photosensitivity Material (volume hologram)
11 ... Reference light 12 ... Reproduction illumination light

Claims (4)

A minute object is placed behind a shielded object with a size that can be easily recognized by the naked eye, and in a predetermined direction, the minute object cannot be observed because it is shielded by the shielded object, and can be observed from a different direction from the specified direction. A method for producing a security hologram,
A hologram photosensitive material is disposed on the opposite side of the shielding object from the minute object,
The shielding object is illuminated with illumination light incident from the hologram photosensitive material side,
A method for producing a security hologram, wherein the minute object is recorded as a transmission type or a reflection type hologram by illuminating with illumination light incident from the opposite side of the hologram photosensitive material. 2. The method for producing a security hologram according to claim 1, wherein the minute object is drawn as a transparent pattern on an opaque background, or drawn as an opaque pattern on a transparent background. The method for producing a security hologram according to claim 1 or 2, wherein a maximum dimension of the minute object is 300 µm or less. The reproduction image of the minute object and the shielding object is reproduced from the hologram recorded as the transmission type or the reflection type hologram, and a volume hologram photosensitive material is disposed in the vicinity of the reproduction image position so as to be coherent with the reproduction illumination light. 4. The method for producing a security hologram according to claim 1, wherein a reference beam from a light source is incident from an arbitrary direction and recorded as a volume hologram in a volume hologram photosensitive material.

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