JP5533124B2 - Volume hologram and method for manufacturing volume hologram - Google Patents

Description

  The present invention relates to a manufacturing method capable of manufacturing a hologram having excellent resistance to contact copy. The present invention also relates to a hologram having excellent resistance to contact copying.

  Conventionally, a volume hologram is known in which interference fringes generated by interference of two light beams are recorded on a hologram recording material (photosensitive material) (for example, Patent Document 1). The volume hologram is used in various fields as an optical element that diffracts light satisfying a condition related to a wavelength and an optical path direction, so-called Bragg conditions, with high diffraction efficiency. In particular, a hologram can be given high designability to an image to be reproduced, and accordingly, the hologram has high discrimination. As a result, the hologram can provide an excellent authenticity determination index, and is thus used as an authenticity indicator that indicates authenticity.

  As a typical manufacturing method, the volume hologram can be manufactured by irradiating two light beams having coherence to the hologram recording material from different directions. In this manufacturing method, interference fringes (interference patterns) are generated when two light beams interfere with each other, and the hologram recording material having photosensitivity reacts corresponding to the intensity pattern of light forming the interference fringes. As a result, interference fringes are recorded on the hologram recording material as some striped pattern, for example, a change in refractive index, a change in transmittance, or a shape change (formation of an uneven pattern). The light satisfying the Bragg condition is diffracted with high diffraction efficiency by the interference fringes recorded on the photosensitive material.

JP 2000-162952 A

  However, such a volume hologram can be replicated by a method called contact copy as long as it is possible to obtain a laser light source (exposure device) and a hologram recording material that are difficult to obtain. Specifically, a volume hologram to be replicated is laminated on the hologram recording material, and then the hologram recording material is subjected to a condition that satisfies the Bragg reflection condition of the volume hologram from the side opposite to the volume hologram. The exposure light is incident. As a result, the exposure light incident on the hologram recording material and the reproduction light obtained by diffracting the exposure light transmitted through the hologram recording material with a volume hologram interfere with each other to generate an interference fringe. Recorded on the material, the volume hologram is replicated. Naturally, it is not preferable that the volume hologram used as the authentic sign is easily duplicated.

  Patent Document 1 discloses a color hologram formed by multiple recording or superposition of two or more volume holograms that diffract light of different wavelengths. In order to contact copy this color hologram, it is necessary to prepare a plurality of laser light sources corresponding to each wavelength, and the hologram has sensitivity to the wavelength of each laser beam generated by the plurality of laser light sources. Recording materials need to be obtained. Therefore, although replication can be made somewhat difficult, on the other hand, obtaining a plurality of laser light sources having different wavelengths and hologram recording having sensitivity to each of the light from the plurality of laser light sources having different wavelengths As long as the material can be obtained, the hologram disclosed in Patent Document 1 can be duplicated.

  The present invention has been made in view of the above points, and provides a hologram having high resistance against counterfeiting by contact copy, and production of a hologram having high resistance against counterfeiting by contact copy It aims to provide a method.

A method for producing a volume hologram according to the present invention includes:
A first interference fringe that diffracts light having a first wavelength incident from the first direction; and a second interference fringe that diffracts light having a second wavelength different from the first wavelength incident from the first direction. A method for producing a volume hologram, comprising:
The first reference light having the first wavelength is incident on the hologram recording material from the first direction, and the first object light having the first wavelength is incident on the hologram recording material, so that the first interference fringes are incident on the hologram recording material. Recording process;
The second reference light having a first wavelength is incident on the hologram recording material from a second direction different from the first direction, and the second object light is incident on the hologram recording material, so that the second interference fringes are Recording on a hologram recording material.

  In the volume hologram manufacturing method according to the present invention, the step of recording the first interference fringes and the step of recording the second interference fringes may be performed in parallel. Note that the step of recording the first interference fringe and the step of recording the second interference fringe may be performed partially in parallel or may be performed completely simultaneously. In such a volume hologram manufacturing method according to the present invention, the first reference light is generated from a first laser light source, and the second reference light is generated from a second laser light source different from the first laser light source. It may be generated.

  Alternatively, in the method for manufacturing a volume hologram according to the present invention, either one of the step of recording the first interference fringe and the step of recording the second interference fringe is completed, and the other is performed. May be. In such a volume hologram manufacturing method according to the present invention, in the step of recording the first interference fringes, a part of the surface is covered on the surface of the hologram recording material on which the first reference light is incident. In the step of arranging the first mask and recording the second interference fringes, a second portion that covers a portion of the hologram recording material that is different from the portion of the surface on the surface on which the second reference light is incident. A mask may be arranged.

  In the volume hologram manufacturing method according to the present invention, at least the first direction from the direction in which the reproduction light formed by diffracting the light having the second wavelength from the first direction with the second interference fringe is observed. The second direction may be determined so that reproduced light obtained by diffracting the light of the first wavelength from the first interference fringe can be observed.

  Furthermore, in the step of recording the first interference fringes of the volume hologram manufacturing method according to the present invention, the first reference light incident on the hologram recording material from one surface side of the hologram recording material is the hologram After passing through the recording material, the hologram recording material is incident on a first hologram master composed of a reflective volume hologram disposed on the other surface side so as to satisfy the Bragg condition, and is diffracted from the first hologram master. The second incident light enters the hologram recording material from the one surface side in the step of recording the second interference fringes into the hologram recording material as the first object light from the other surface side. A reflective volume hologram disposed on the other surface side of the hologram recording material after the reference light has passed through the hologram recording material So that the Bragg condition is satisfied, and the diffracted light from the second hologram master enters the hologram recording material as the second object light from the other surface side. Good.

  Alternatively, in the step of recording the first interference fringes of the volume hologram manufacturing method according to the present invention, the Bragg is applied to the first hologram master made of a transmission volume hologram disposed on one side of the hologram recording material. Of the light incident so as to satisfy the condition, the diffracted light from the first hologram original plate is used as the first object light, and the 0th-order light from the first hologram original plate of the light is the first reference light. As described above, in the step of entering the hologram recording material from the one surface side and recording the second interference fringes, each of the hologram recording material comprises a transmission type volume hologram disposed on the one surface side Of the light incident on the second hologram original plate so as to satisfy the Bragg condition, the diffracted light from the second hologram original plate is used as the second object light. To, 0-order light is the second reference light from the second hologram master of the light, respectively, it may be incident from the side of the one surface to the hologram recording material.

  In the volume hologram manufacturing method according to the present invention as described above, the first interference fringes in a state in which a laminated original obtained by superimposing the first hologram original and the second hologram original is laminated on the hologram recording material. And the step of recording the second interference fringes may be performed.

Further, the volume hologram manufacturing method according to the present invention further includes a step of manufacturing the second hologram master,
The second object light is configured such that a two-dimensional pattern located on a plane parallel to the surface of the volume hologram is reproduced by diffracting incident light in which the second interference fringes satisfy the Bragg condition. And
The step of manufacturing the second hologram master is:
A step of exposing the hologram recording material for the second hologram original plate from the side on which the mask is arranged in a state where a mask having the same pattern as the two-dimensional pattern is arranged on the hologram recording material for the second hologram original plate When,
In the state where the holographic scattering plate is laminated on the exposed hologram recording material for the second hologram original plate, reference light and object light as diffraction from the holographic scattering plate are incident on the hologram recording material for the hologram original plate. You may make it have a process.
In the case where the hologram master is configured as a reflection type volume hologram, in the step of causing the reference light and the object light to enter the hologram recording material for the hologram master, one of the hologram recording materials for the hologram master is used. Reference light is incident on the hologram recording material from the side of the surface, and after the reference light is transmitted through the hologram recording material for hologram master, the reflection disposed on the other surface of the hologram recording material for hologram precursor Is incident on a holographic scattering plate made of a volume hologram so as to satisfy the Bragg condition, and diffracted light from the holographic scattering plate enters the hologram recording material for hologram master from the other surface side as object light. You may do it. Alternatively, when the hologram master is configured as a transmission type volume hologram, in the step of causing the reference light and the object light to enter the hologram recording material for the hologram master, one surface of the hologram recording material for the hologram master The light is incident on the holographic scattering plate made of a transmission type volume hologram arranged on the side so as to satisfy the Bragg condition, and among the light, the diffracted light from the holographic scattering plate is used as object light, and The 0th-order light from the holographic scattering plate of the light may be incident on the hologram recording material for hologram master from the one side as reference light.

  Further, in the volume hologram manufacturing method according to the present invention, the first object light is configured such that a three-dimensional image is reproduced by diffracting incident light satisfying the Bragg condition by the first interference fringes. It may be.

  Furthermore, in the volume hologram manufacturing method according to the present invention, the second object light may be a parallel light beam. Alternatively, the second object light is reproduced such that a two-dimensional pattern located on a plane parallel to the surface of the volume hologram is reproduced by diffracting incident light in which the second interference fringes satisfy the Bragg condition. It may be configured. More preferably, the second object light is reproduced such that a two-dimensional pattern located on the surface of the volume hologram is reproduced by diffracting incident light in which the recorded second interference fringes satisfy the Bragg condition. , May be configured.

Furthermore, in the method for producing a volume hologram according to the present invention,
The first object light is configured such that a two-dimensional pattern located on a plane parallel to the surface of the volume hologram is reproduced by diffracting incident light in which the first interference fringes satisfy the Bragg condition. ,
The second object light is configured such that a two-dimensional pattern located on a plane parallel to the surface of the volume hologram is reproduced by diffracting incident light in which the second interference fringes satisfy the Bragg condition. And
The position of the two-dimensional pattern reproduced by diffracting the light of the first wavelength from the first direction with the first interference fringe and the light of the second wavelength from the first direction are the second The first object light and the second object light are configured such that the position of the two-dimensional pattern reproduced by diffracting with an interference fringe is shifted in the normal direction to the surface of the volume hologram. Also good.

  Furthermore, in the volume hologram manufacturing method according to the present invention, the two-dimensional pattern is one or more selected from the group consisting of letters, numbers, symbols, and patterns, and one letter, number constituting the two-dimensional pattern. The symbol or pattern may be sized to fall within a 72 μm square area.

The first volume hologram according to the present invention is:
A first interference fringe that diffracts light of a first wavelength incident from a first direction;
A volume hologram comprising: a second interference fringe that diffracts light having a second wavelength different from the first wavelength incident from the first direction;
The first interference fringes diffract light of the first wavelength from the first direction to reproduce a three-dimensional elephant,
The second interference fringe diffracts the parallel light flux having the second wavelength from the first direction as reproduction light composed of the parallel light flux,
The light of the first wavelength from the first direction from the direction in which the reproduction light as a parallel light beam formed by diffracting the parallel light flux of the second wavelength from at least the first direction by the second interference fringe is observed. The first interference fringe reproduces the three-dimensional image so that the three-dimensional image reproduced by diffracting the light with the first interference fringe can be observed.

The second volume hologram according to the present invention is:
A first interference fringe that diffracts light of a first wavelength incident from a first direction;
A volume hologram comprising: a second interference fringe that diffracts light having a second wavelength different from the first wavelength incident from the first direction;
The first interference fringes diffract light of the first wavelength from the first direction to reproduce a three-dimensional elephant,
The second interference fringes diffract light of the second wavelength from the first direction to reproduce a two-dimensional pattern located on a plane parallel to the surface of the volume hologram,
The light of the first wavelength from the first direction from the direction in which the two-dimensional pattern reproduced by diffracting the light of the second wavelength from the first direction with the second interference fringe is observed. The first interference fringe reproduces the three-dimensional image so that the three-dimensional image reproduced by diffracting the light with the first interference fringe can be observed.

The third volume hologram according to the present invention is:
A first interference fringe that diffracts light of a first wavelength incident from a first direction;
A volume hologram comprising: a second interference fringe that diffracts light having a second wavelength different from the first wavelength incident from the first direction;
The first interference fringe diffracts the light of the first wavelength from the first direction to reproduce a first two-dimensional pattern located on a plane parallel to the surface of the volume hologram,
The second interference fringes diffract light of the second wavelength from the first direction to reproduce a second two-dimensional pattern located on a plane parallel to the surface of the volume hologram,
The first two-dimensional pattern reproduced by diffracting the light of the first wavelength from the first direction with the first interference fringe, and the light of the second wavelength from the first direction The second two-dimensional pattern reproduced by diffracting with two interference fringes is observed from the same direction and at a position shifted from each other along the normal direction to the surface of the volume hologram. As described above, the first interference fringe and the second interference fringe reproduce the two-dimensional image.

In any one of the first to third volume holograms according to the present invention,
The two-dimensional pattern is one or more selected from the group consisting of letters, numbers, symbols and patterns,
One character, number, symbol, or pattern constituting the two-dimensional pattern may have a size that falls within a 72 μm square area.

  In any one of the first to third volume holograms according to the present invention, the second interference fringe reproduces the two-dimensional pattern so that the two-dimensional pattern is located on the surface of the volume hologram. May be.

  According to the present invention, it is possible to give a hologram high resistance against forgery by contact copying.

FIG. 1 is a diagram for explaining a volume hologram and its diffraction action in one embodiment of the present invention. FIG. 2 is a view for explaining an image reproduced by the volume hologram shown in FIG. FIG. 3 is a diagram for explaining the optical action by the first interference fringes of the volume hologram shown in FIGS. 1 and 2. FIG. 4 is a diagram for explaining the optical action by the second interference fringes of the volume hologram shown in FIGS. 1 and 2. FIG. 5 is a diagram for explaining an example of a method for manufacturing a hologram, and describes a method for recording the first interference fringe and the second interference fringe of the volume hologram shown in FIGS. 1 and 2 in parallel. FIG. FIG. 6 is a diagram for explaining a method of manufacturing the first hologram master used for recording the first interference fringes shown in FIG. FIG. 7 is a diagram for explaining a method of manufacturing the second hologram master used for recording the second interference fringes shown in FIG. FIG. 8 is a front view showing the second hologram original plate and the mask being manufactured shown in FIG. FIG. 9 is a diagram for explaining a method of manufacturing a second hologram master used for recording the second interference fringes shown in FIG. FIG. 10 is a view for explaining a modification of the hologram manufacturing method, and is a view for explaining a method of recording the first interference fringes of the volume hologram shown in FIGS. 1 and 2. FIG. 11 is a diagram for explaining a modification of the hologram manufacturing method together with FIG. 10, and is a diagram for explaining a method for recording the second interference fringes of the volume hologram shown in FIGS. 1 and 2. It is. FIG. 12 is a diagram showing an optical system in which the presence / absence of interference between laser beams generated from two laser light sources is examined. FIG. 13 is a diagram showing another optical system in which the presence or absence of interference is investigated by Mach-Zehnder interferometry. FIG. 14 is a view showing an image of light projected on the screen by the optical system of FIG. FIG. 15 is a diagram showing an image of light projected on the screen by the optical system of FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to the present specification, for the sake of illustration and ease of understanding, the scale, the vertical / horizontal dimension ratio, and the like are appropriately changed and exaggerated from those of the actual product.

  FIGS. 1-9 is a figure for demonstrating the manufacturing method of the volume type hologram and volume type hologram in one embodiment of this invention. Among these, FIGS. 1 to 4 are diagrams mainly for explaining the volume hologram and its operation, and FIGS. 5 to 9 are diagrams for mainly explaining a method for manufacturing the volume hologram. .

  A volume hologram (hereinafter also simply referred to as a hologram) 10 described below diffracts light L1a and L1b having different wavelengths incident from the same direction, that is, light L1a and L1b having different colors incident from the same direction, respectively. It is configured as a reflective hologram (Lippmann hologram). Reflective volume holograms are recorded with interference fringes, and when the Bragg reflection conditions (Bragg conditions) regarding the interference fringe spacing, incident light wavelength and incident angle are satisfied, the incident light has high diffraction efficiency. Diffracts (reflects). The hologram 10 described below can improve the design of the article to which the hologram is attached or indicate the authenticity of the article by such wavelength selectivity and angle selectivity with respect to incident light. Yes, it can be used by being affixed to articles, especially packaging materials, cards, certificates, securities, gift certificates, etc.

  In the following description, the number of interference fringes may be referred to. In this specification, the number of interference fringes is the number of patterns that are generally configured, and are elements that constitute the patterns. It's not that number. For example, in the case where interference fringes are formed by a group of lines (a group of faces when viewed three-dimensionally) composed of a plurality of lines extending in parallel (a plurality of faces when viewed three-dimensionally), the number of interference fringes Indicates the number of muscle groups, not the number of muscles contained in the muscle groups.

  As shown in FIGS. 3 and 4, the hologram 10 includes first interference fringes 11a (see FIG. 3) that diffract the light L1a having the first wavelength incident on the hologram 10 from the first direction d1 with high diffraction efficiency, A second interference fringe 11b (see FIG. 4) that diffracts light L1b having a second wavelength different from the first wavelength incident from one direction d1 with high diffraction efficiency. That is, as shown in FIG. 3, the light L1a having the first wavelength incident on the hologram 10 from the first direction d1 satisfies the Bragg reflection condition of the first interference fringe 11a, and similarly shown in FIG. As described above, the light L1b having the second wavelength incident on the hologram 10 from the first direction d1 satisfies the Bragg reflection condition of the second interference fringe 11b.

Here, the Bragg reflection condition being satisfied corresponds to the following expression (1) being satisfied.
2 × d × sin θ = λ Formula (1)
D in the formula (1) is a cross section parallel to both the traveling direction of light and the normal direction to each streak pattern (each planar pattern) that forms interference fringes in the region where the light is incident. , The interval (the pitch of the dark and light stripes) between the lines (each surface) constituting the interference fringes. In the equation (1), θ is an angle formed by the incident direction of light (or the diffraction direction of the light interference fringes) with respect to the direction in which each line forming the interference fringes extends in the cross section. Further, λ in the formula (1) is the wavelength of light incident on the interference fringes.

In the present embodiment, since the light L1a having the first wavelength incident on the hologram 10 from the first direction d1 satisfies the Bragg condition of the first interference fringe 11a, the following expression (2) is satisfied. Similarly, since the light L1b having the second wavelength incident on the hologram 10 from the first direction d1 satisfies the Bragg condition of the second interference fringe 11b, the following expression (3) is satisfied.
2 × da × sin θa = λa (2)
2 × db × sin θb = λb (3)
Da and db in the equations (2) and (3) correspond to d in the equation (1), and are intervals between the interference fringes. In addition, θa and θb in the equations (2) and (3) correspond to θ in the equation (1), and the traveling direction of the light incident on each interference fringe (or the light diffracted by each interference fringe) Is an angle formed with respect to the direction in which each interference fringe extends. Further, λa and λb in the equations (2) and (3) correspond to λ in the equation (1) and are wavelengths of light incident on each interference fringe.

The expression (1) indicating the Bragg reflection condition is obtained by appropriately adjusting the incident angle θ of the incident light with respect to the wavelength λ of the incident light, or appropriately By setting the wavelength λ, it is satisfied. That is, it is not only when light of a predetermined specific wavelength is incident on the hologram at a predetermined specific incident angle that the diffraction fringes of a certain volume hologram are diffracted with high diffraction efficiency. For example, as shown in FIG. 4, when the light L2b having the first wavelength is incident on the hologram 10 from the second direction d2 different from the first direction d1, the following equation (4) is satisfied. The Bragg condition is satisfied, and the second interference fringes 11b are diffracted with high diffraction efficiency.
2 × db × sin θb ′ = λa (4)
At this time, as shown in FIG. 4, if the light L1b of the second wavelength from the first direction d1 is diffracted in the third direction d3 by the second interference fringe 11b, the light of the first wavelength from the second direction d2 is assumed. The light L2b is diffracted by the second interference fringes 11b in a direction (fourth direction d4) different from the third direction d3. Note that θb ′ in Expression (4) corresponds to θ in Expression (1), and is an angle formed by the light L2b incident on the second interference fringe 11b with respect to the extending direction of the second interference fringe 11b. .

  Referring back to FIGS. 1 and 2, the first reproduction light L3a formed by diffracting the first illumination reproduction light L1a incident on the first surface 10a of the hologram 10 along the first direction d1 by the first interference fringes 11a. Reproduces the first image 12 a that can be observed from the first surface 10 a side of the hologram 10. In the present embodiment, the first image 12a is configured as a three-dimensional image.

  On the other hand, the second reproduction light L3b obtained by diffracting the reproduction illumination light L1b having the second wavelength incident on the first surface 10a of the hologram 10 along the first direction d1 by the second interference fringe 11b is the first reproduction light L3b of the hologram 10. The second image 12b that can be observed from the side of the surface 10a is reproduced. The second image 12b is configured as a two-dimensional pattern. Here, the two-dimensional pattern is a planar pattern, and can be configured by arranging one or more selected from the group consisting of letters, numbers, symbols, and patterns, for example. However, the planar two-dimensional pattern referred to here is not only a pattern that is positioned on the surface of the hologram 10, for example, as observed or pasted on the surface of the hologram 10, but also the hologram 10. Also included are flat patterns that are observed at positions that are lifted from the surface of the hologram 10 and at positions that are recessed from the surface of the hologram 10. Therefore, the two-dimensional pattern here includes a planar pattern reproduced in a three-dimensional space.

  In the present embodiment, the two-dimensional pattern forming the second image 12 b is reproduced on a plane parallel to the surface of the hologram 10. In particular, in the illustrated example, the two-dimensional pattern as the second image 12b reproduced by the second interference fringe 11b is formed by a character string “GENUINE”, and is located on the surface of the hologram 10. It is observed as a character string formed on the surface of the hologram 10.

  The term “positioned (formed) on the surface of the hologram” here means not only when the two-dimensional pattern is accurately positioned on the surface of the hologram in a strict sense, but also as follows: If the optical action similar to that when the two-dimensional pattern is positioned on the surface of the hologram in a strict sense is within the range that can be obtained by visual judgment, the two-dimensional pattern is the hologram. The case where the surface is slightly deviated from the surface is also included.

  That is, when the hologram 10 is placed under white light, as long as the Bragg reflection condition is satisfied, the second image 12b is reproduced in different directions in different colors. As a result, the second image 12b is reproduced with a different color at a position shifted in a direction parallel to the surface of the hologram 10 (that is, the planar direction), and the planar direction of the image reproduced with the different color Due to the misalignment of the image, the contour of the image is visually perceived as blurred. Then, the amount of positional deviation in the planar direction between images of different colors increases as the reproduction position of the image is far from the position on the surface of the hologram 10. In addition, when a three-dimensional object having a depth is reproduced, image blurring appears prominently. On the other hand, the phenomenon in which the image is observed in a blurred manner is mitigated when the second image 12b is a two-dimensional pattern, and becomes substantially invisible when the second image 12b is reproduced near the surface of the hologram 10, in particular. . Here, the second image 12b is interpreted as being located on the surface of the hologram 10 as long as the second image 12b can be clearly reproduced without blurring the outline of the two-dimensional pattern.

  By the way, as shown in FIG. 1, in the present embodiment, the two-dimensional pattern constituting the second image 12b has only a portion forming the pattern (for example, a character string portion) or does not form the pattern. Only the portion functions as a holographic scattering plate so that an image can be formed and observed by an observer. Here, the holographic scattering plate is a kind of hologram (holographic optical element), and is an optical element that mainly scatters or reflects incident light that satisfies the Bragg condition. In the present embodiment, the reproduction light L3b forming the second image 12a is mainly scattered light traveling in the third direction d3.

  However, the present invention is not limited to this example, and the two-dimensional pattern constituting the second image 12b includes only a portion forming the pattern (for example, a character string portion) or only a portion not forming the pattern as a holographic mirror. As a result, the image may be formed so that it can be observed by an observer. Here, the holographic mirror is a kind of hologram (holographic optical element), and is an optical element that reflects incident light that satisfies the Bragg condition without scattering. Therefore, in this example, when a light beam having a specific wavelength enters the hologram 10 so as to satisfy the Bragg reflection condition of the second interference fringe 11b, the second image 12b is diffracted by the second interference fringe 11b. The second reproduction light L3b becomes a parallel light beam.

  In addition, all or part of the two-dimensional pattern forming the first image 12a and the second image 12b is constituted by letters, numbers, symbols or patterns arranged in a size that fits in a 72 μm square area. Also good. When a human observes an object with the naked eye, the position (near point) at which the object can be clearly seen without blurring is normally considered to be a position 250 mm away from the eye. The resolution is about 1 minute (about 1/60 °) in angle (see page 45 of “Field Guide Geometric Optics” by John E. Greivenkamp). As a result, the minimum resolution at the near point is about 72.7 μm. For this reason, when the size, width, and height of each character, number, symbol, or pattern constituting the two-dimensional pattern is 72 μm or less, typically, a human character, number, The symbol or pattern cannot be identified. That is, it is necessary to take some means such as using a magnifying glass in order to identify a character, number, symbol or pattern of a two-dimensional pattern having such a size. Therefore, according to the first image 12a and the second image 12b having such a two-dimensional pattern, it is possible to impart high discrimination to the hologram 10 and to function the hologram 10 extremely effectively as an authentic sign.

  Further, in the present embodiment, from the direction in which the two-dimensional pattern (second image 12b) reproduced by diffracting the light L1b having the second wavelength from the first direction d1 with the second interference fringes 12b is observed, The first interference fringe 11a has the third order so that a three-dimensional image (first image 12a) reproduced by diffracting the light L1a of the first wavelength from the first direction d1 with the first interference fringe 11a can be observed. Play the original image. That is, at least the second wavelength light L1b from the first direction d1 is mainly diffracted by the second interference fringe 11b in the third direction d3, and the first wavelength light L1a from the first direction d1 is the first interference fringe 11a. Is diffracted by The three-dimensional image (first image 12a) reproduced by diffracting the light L1a having the first wavelength from the first direction d1 with the first interference fringe 11a has a so-called viewing zone and has a certain angular range. Can be observed from the inner direction. The light L1b having the second wavelength from the first direction d1 is mainly diffracted by the second interference fringe 12b in one direction within the viewing zone where the first image 12a can be observed.

  According to the volume hologram 10 according to the present embodiment as described above, the incident lights L1a and L1b from the same direction on the hologram 10 are diffracted by the first interference fringes 11a, thereby generating a three-dimensional image (first image). 12a) is reproduced, and the two-dimensional pattern (second image 12b) is reproduced with a color different from the three-dimensional image (first image 12a) by being diffracted by the second interference fringes 11b. . In addition, a direction in which a three-dimensional image (first image 12a) is observed by diffraction at the first interference fringe 11a and a two-dimensional pattern (second image 12b) are observed by diffraction at the second interference fringe 11b. Is at least partially coincident with the direction in which it is to be done. That is, for example, when white light enters the hologram 10 at a predetermined incident angle, the three-dimensional image (first image 12a) and the two-dimensional pattern (second image 12b) are simultaneously observed in different colors.

  The hologram 10 has both excellent design and high discrimination due to the three-dimensional image (first image 12a) and the two-dimensional pattern (second image 12b) observed in different colors. Accordingly, the hologram 10 can be easily determined for authenticity and can function extremely effectively as an authenticity indicator.

  Next, an example of a method for manufacturing the hologram 10 as described above will be described mainly with reference to FIGS. According to the following manufacturing method, the volume hologram 10 according to the present embodiment that has been described can be manufactured inexpensively and easily.

  The volume hologram 10 is formed from the hologram recording material 20. For this reason, it is assumed that the hologram recording material 20 is arranged in the same positional relationship as the hologram 10 in a corresponding positional relationship, and the direction with respect to the hologram recording material 20 is also specified using the direction used with respect to the hologram 10. . Furthermore, the film-like member is also applied to the film-like member described later (for example, hologram masters 30, 40, laminate master 25, hologram recording material 35, 45 for hologram master) laminated on hologram recording material 20. The direction is specified by using the directions used for the hologram 10 and the hologram recording material 20 as being laminated on the recording material 20.

  In the hologram manufacturing method described below, the first reference light L1r is incident on one surface (second surface) 20b of the hologram recording material 20, and the other surface (first surface) 20a of the hologram recording material 20 is entered. The first object light L3o having the first wavelength is incident on the light source to generate an interference fringe of light formed by the interference between the first reference light L1r and the first object light L3o, thereby producing a first interference fringe (first interference pattern). 11a is recorded on the hologram recording material 20, and the second reference light L2r is incident on one surface 20b of the hologram recording material 20, and the second object light L4o is incident on the other surface 20a of the hologram recording material 20. And causing the second reference light L2r and the second object light L4o to interfere with each other to generate an interference fringe of light to record the second interference fringe (second interference pattern) 11b on the hologram recording material 20. , It contains mainly.

  In particular, in the following hologram manufacturing method, the wavelengths of the first reference light L1r and the first object light L3o and the wavelengths of the second reference light L2r and the second object light L4o are the same. It is said.

  Further, in the following hologram manufacturing method, the step of recording the first interference fringe 11a and the step of recording the second interference fringe 11b are performed at least partially in parallel. Exposure for recording the fringe 11a (exposure of the first reference light L1r and the first object light L3o) and exposure for recording the second interference fringe 11b (exposure of the second reference light L2r and the second object light L4o) ) Is performed in parallel for at least one period.

  First, the exposure when recording the first interference fringe (first interference pattern) 11a on the hologram recording material 20 by generating the interference fringes of the first light will be described.

  In addition, as the hologram recording material 20 in which the interference fringes 11a and 11b are recorded to form the hologram 10, for example, a photopolymer, a silver salt emulsion, dichromated gelatin, a photoresist, or the like can be used.

  In the step of recording the first interference fringes 11a, the wavelengths of the first reference light L1r and the first object light L3o exposed to the hologram recording material 20 that forms the hologram 10 are the first reproduction shown in FIG. The first wavelength is the same as that of the illumination light L1a and the first reproduction light L3a. Therefore, as shown in FIG. 5, the first reference light L1r travels in the opposite direction to the first reproduction illumination light L1a along the first direction d1 and enters the hologram recording material 20 from the one surface 20b side. . The first object light L3o travels in the direction opposite to the first reproduction light L3a from the direction centering on the third direction d3 and enters the hologram recording material 20 from the other surface 20a side.

  The other surface (first surface) 20a of the hologram recording material 20 forms the above-described first surface 10a of the hologram 10, and one surface (second surface) 20b of the hologram recording material 20 is the hologram. Thus, the second surface 10b opposite to the first surface 10a is formed.

  Next, the exposure when the second light interference fringe (second interference pattern) 11b is recorded on the hologram recording material 20 by generating the second light interference fringe will be described. The wavelengths of the second reference light L2r and the second object light L4o exposed to the hologram recording material 20 are different from the wavelengths (second wavelengths) of the second reproduction light L1b and the second reproduction light L3b, and the first reproduction illumination. It is the same wavelength (first wavelength) as the light L1a and the first reproduction light L3a. As described with reference to FIG. 4, the second interference fringe 11b is centered in the third direction d3 with high diffraction efficiency for the light L1b having the second wavelength incident on the first surface 10a of the hologram 10 from the first direction d1. Scattered and reflected in the specified direction. Further, as well shown in FIG. 4, the second interference fringe 11b has a high diffraction efficiency in the fourth direction d4 in the first wavelength light L2b incident on the first surface 10a of the hologram 10 from the second direction d2. Scattered and reflected in the direction centered on. Therefore, the second interference fringes 11b can be recorded on the hologram recording material 20 by using the second reference light L2r and the second object light L4o having the first wavelength.

  Specifically, as shown in FIG. 5, the second reference light L2r travels in the opposite direction to the second reproduction illumination light L2b along the second direction d2 to the hologram recording material 20 on the one surface 20b side. Incident from. The second object light L4o travels in the direction opposite to the second reproduction light L4b from the direction centering on the fourth direction d4 and enters the hologram recording material 20 from the other surface 20a side.

  Further, in the manufacturing method described here, as shown in FIG. 5, the object beam L3o for reproducing the first image 12a made of a three-dimensional image is the first hologram master made of a reflection type volume hologram. 30 is obtained by reproducing. Similarly, the second object light L4o for reproducing the second image 12b composed of a two-dimensional pattern is obtained by reproducing the second hologram original plate 40 composed of a reflection type volume hologram.

  Specifically, as shown in FIG. 5, a laminated original plate 25 formed by laminating a first hologram original plate 30 that generates first object light L3o and a second hologram original plate 40 that generates second object light L4o is a hologram. The recording material 20 is laminated on the first surface 20a side. Thereby, the second hologram original plate 40 and the first hologram original plate 30 are laminated on the hologram recording material 20 in order from the first surface 20 a side of the hologram recording material 20. In this state, the first reference light L1r having the first wavelength is formed on the hologram recording material 20 from the second surface 20b side as a parallel light beam made of coherent light, typically laser light, along the first direction d1. Irradiated. In parallel with the irradiation of the first reference light L1r, the second reference light L2r having the first wavelength is converted into a holographic recording material 20 as a parallel light flux composed of coherent light, typically laser light, along the second direction d2. Is irradiated from the second surface 20b side.

  The first reference light L1r passes through the hologram recording material 20 and the second hologram original plate 40, and then enters the first hologram original plate 30 so as to satisfy the Bragg condition of the first hologram original plate 30. That is, the first reference light L1r is incident on the first hologram original plate 30 as reproduction illumination light, and is diffracted by the first hologram original plate 30. As a result, a three-dimensional image is reproduced by the first hologram master 30, and the diffracted light that forms this three-dimensional image passes through the second hologram master 40, and then the first object light L 3 o is transferred to the hologram recording material 20. Incident from the surface 20a.

  As a result, in the hologram recording material 20, the first reference light L1r and the first object light L3o interfere with each other, and light interference fringes composed of bright and dark stripes are formed. The hologram recording material 20 having photosensitivity reacts corresponding to the bright and dark stripes. As a result, the first interference fringes 11a having a pattern corresponding to the bright and dark stripes are recorded in the hologram recording material 20, and a diffraction function is imparted. As an example, when the hologram recording material 20 is made of a photopolymer, the first interference fringes 11a are recorded as a refractive index modulation pattern.

  On the other hand, after passing through the hologram recording material 20, the second reference light L <b> 2 r is incident on the second hologram original plate 40 so as to satisfy the Bragg condition of the second hologram original plate 40. That is, the second reference light L2r is incident on the second hologram original plate 40 as reproduction illumination light and is diffracted by the second hologram original plate 40. As a result, the two-dimensional character string pattern is reproduced by the second hologram master 40. The diffracted light forming this two-dimensional character string pattern enters the hologram recording material 20 from the other surface 20a as the second object light L4o. As a result, in the hologram recording material 20, the second reference light L2r and the second object light L4o interfere with each other, and light interference fringes composed of bright and dark stripes are formed. The hologram recording material 20 having photosensitivity reacts corresponding to the bright and dark stripes. As a result, the second interference fringes 11b having a pattern corresponding to the bright and dark stripes are recorded in the hologram recording material 20, and a diffraction function is imparted.

  As the coherent light (in this example, the first reference light L1r and the second reference light L2r) for recording the interference fringes 11a and 11b on the hologram recording material 20, helium-neon laser, argon ion laser, krypton ion Light oscillated from a laser light source such as a laser or a neodymium yag laser can be used.

  By the way, as shown in FIG. 5, a light shielding layer 27 is provided on the surface of the laminated original plate 25 that does not face the hologram recording material 20. Thereby, the reference light L1r, L2r is reflected by the surface of the laminated original plate 25 not facing the hologram recording material 20, and the ambient light is incident on the hologram recording material 20 from the first surface 20a side. Is effectively suppressed. As a result, unintentional exposure of the hologram recording material 20 due to stray light or the like, and accordingly, recording of unintended interference fringes is effectively prevented.

  In addition, from the viewpoint of preventing the occurrence of stray light or the like, between the lamination original plate 25 and the hologram recording material 20, between the lamination original plate 25 and the light shielding layer 27, and the first hologram recording original plate 30 of the lamination original plate 25, An index matching layer made of an index matching liquid may be provided at one or more between the second hologram recording original plate 40. According to the index matching layer, reflection due to a sudden change in refractive index between adjacent layers can be effectively prevented, and an air layer that causes a sudden change in refractive index is formed between adjacent layers. Can also be effectively prevented.

  Here, an example of a method for producing the first hologram master 30 made of a reflective volume hologram for reproducing a three-dimensional image and the second hologram master 40 made of a reflective volume hologram for reproducing a two-dimensional pattern will be described. Keep it.

  First, the first hologram original plate 30 can be manufactured as follows. As shown in FIG. 6, a model 32 produced based on the shape (in the illustrated example, a face shape) of a first image 12a composed of a three-dimensional image to be reproduced by the first interference fringes 11a is represented by a first hologram. The original hologram recording material 35 is disposed at a predetermined position with reference.

  As shown in FIG. 6, in this state, the first hologram original plate is obtained by using the coherent light of the first wavelength, typically the laser light of the first wavelength oscillated from the laser light source, as the reference light L61 and the object light L62. Is incident on a hologram recording material 35 for use. Among these, the reference light L61 enters the hologram recording material 35 for the first hologram original plate from the side of the first surface (the other surface) 35a along the first direction d1 as parallel light. On the other hand, the object light L62 is incident on the first hologram master hologram recording material 35 as reflected light from the model 32 from the second surface (one surface) 35b side. At this time, the object light L62 is incident on the hologram recording material 35 for the first hologram master as diffused light that spreads in the angular range centering on the third direction d3. As a result, the hologram recording material 35 for the first hologram master is exposed by the reference light L61 and the object light L62, and interference fringes that can reproduce the same image as the first image 12a are recorded. By applying an appropriate post-process to the hologram recording material 35 for the first hologram master on which the interference fringes are recorded, the first hologram master 30 described above is obtained.

  In addition, the first surface 35a of the hologram recording material 35 for the first hologram original plate in the above description forms a surface facing the light shielding layer 27 of the first hologram original plate 30, and the hologram recording material for the first hologram original plate 30 The second surface 35 b of 35 forms a surface on the side facing the hologram recording material 20 of the first hologram master 30.

  Next, the second hologram master 40 can be produced as follows. First, as shown in FIGS. 7 and 8, a light shielding mask 48 capable of shielding exposure light in the same pattern as the two-dimensional pattern is arranged on the hologram recording material 45 for the second hologram master 40. Next, as shown in FIG. 7, the hologram recording material 45 for the second hologram master is exposed from the side where the light shielding mask 48 is disposed. As a result, a region not covered with the light shielding mask 48 is subjected to a desensitization process (deactivation process) and loses its photosensitivity. The light L72 used for the exposure in the desensitization process is not particularly limited in wavelength, and for example, ultraviolet light can be used. When ultraviolet rays are used, the desensitization process can be more reliably performed in a short time.

  Thereafter, a holographic scattering plate 49 configured to scatter and reflect light of the first wavelength from the second direction d2 in a direction centered on the fourth direction d4 is prepared. Next, as shown in FIG. 9, the prepared holographic scattering plate 49 is laminated on the hologram recording material 45 for the second hologram master from the one surface (second surface) 45 b side. In this state, the reference light L91 having the first wavelength is incident on the hologram recording material 45 for the second hologram master from the other surface (first surface) 45a side. The reference light L91 is applied to the hologram recording material 45 for the second hologram master as a parallel light beam made of coherent light, typically laser light, along the second direction d2. Then, the reference light L 91 transmitted through the hologram recording material 45 for the second hologram master is incident on the holographic scattering plate 49 so as to satisfy the Bragg condition of the holographic scattering plate 49. As a result, the reference light L91 enters the holographic scattering plate 49 as reproduction illumination light and is diffracted by the holographic scattering plate 49, and the scattered reflected light obtained by diffracting the reference light L91 by the holographic scattering plate 49 becomes object light. As L92, the light enters the hologram recording material 45 for the second hologram master from one surface 45b side. At this time, the scattered reflected light, which is the object light L92, enters the hologram recording material 45 for the second hologram master as scattered light that spreads in the angular range centering on the fourth direction d4 described above. As a result, the photosensitive character string pattern region in the hologram recording material 45 for the second hologram master is exposed by the reference light L91 and the object light L92, and the same two-dimensional character as the second image 12b. Interference fringes that can reproduce the column pattern are recorded. The second hologram master 40 described above is obtained by subjecting the hologram recording material 45 for the second hologram master to an appropriate post-treatment.

  In addition, one surface 45b of the hologram recording material 45 for the second hologram original plate in the above description forms a surface on the side facing the hologram recording material 20 of the second hologram original plate 40, and the hologram recording for the second hologram original plate 40 The other surface 45 a of the material 45 forms a surface facing the light shielding layer 47 of the second hologram original plate 40.

  Further, as the hologram recording materials 35 and 45 used for producing the first hologram original plate 30 and the second hologram original plate 40 and the light for exposure, the hologram recording material 20 for producing the hologram 10 and the hologram 10 described above are used. Laser light oscillated from a laser light source for manufacturing can be used. Further, for the same purpose as when recording each interference fringe 11a, 11b, a light shielding layer may be provided on the surface of each holographic scattering plate 39, 49 opposite to the hologram recording material 35, 45 for the hologram master. Alternatively, an index matching layer may be provided between the holographic scattering plates 39 and 49 and the hologram recording materials 35 and 45 for the hologram master and the light shielding layers.

  As described above, the first interference fringes 11a and the second interference fringes 11b can be recorded on the hologram recording material 20. In such a hologram manufacturing method, the first interference fringes 11a and the second interference fringes 11b are formed at the same timing by simultaneous exposure. If the first interference fringes 11a and the second interference fringes 11b are recorded on the hologram recording material 20 in parallel by such a method, the hologram 10 can be produced in a short time, which is preferable from the viewpoint of productivity. . In addition, it is not necessary to prepare the optical system with complicated operations multiple times. Furthermore, the diffraction efficiency in each interference fringe 11a, 11b can be adjusted by a simple operation such as adjusting the amount of each exposure light (in the example shown, the first reference light L1r and the second reference light L2r). . That is, the hologram 10 in which the interference fringes 11a and 11b having desired optical characteristics are accurately formed can be formed inexpensively and easily.

  In addition, according to such simultaneous exposure, both the first interference fringes 11a and the second interference fringes 11b can be recorded in the same region of the hologram recording material. As a result, the first image 12a reproduced by the first interference fringe 11a and the second image 12b reproduced by the second interference fringe 11b can be observed in an overlapping manner. The distinguishability can be further improved.

  By the way, when the 1st interference fringe 11a and the 2nd interference fringe 11b are recorded on the hologram recording material 20 in parallel by simultaneous exposure, the first reference light L1r and the first object light L3o for forming the first interference fringe 11a are recorded. The second reference light L2r and the second object light L4o for forming the second interference fringes 11b are simultaneously incident into the hologram recording material 20. Therefore, there is a possibility that unnecessary interference fringes resulting from interference between either the first reference light L1r or the first object light L3o and the second reference light L2r or the second object light L4o may be recorded. As a specific measure for avoiding such a problem, the first reference light L1r having the first wavelength is oscillated from the first laser light source, and the second reference light L2r having the first wavelength is a second laser different from the first laser light source. What is necessary is just to make it oscillate from a light source.

  Here, in FIGS. 12 to 15, the inventor of the present invention has interference between the laser beams L 121 a and L 121 b generated from two different laser light sources 50 a and 50 b and a laser generated from the same laser light source 50 c. The result of investigating the interference between the separated lights L131a and L131b formed by separating the L131 light is shown. As shown in FIG. 12, two laser beams L121a and L121b oscillated from two different laser light sources 50a and 50b are synthesized by a half mirror HM, then spread by a spatial filter SF, and projected onto a screen 55. . In this case, as shown in FIG. 14, the light 57 is projected on a substantially circular area corresponding to the diffusion direction by the spatial filter SF on the screen 55, and no interference pattern consisting of bright and dark stripes was observed. On the other hand, as shown in FIG. 13, the laser light L131 generated from a single laser light source 50c is once separated by the beam splitter BS, and then the separated lights L131a and L131b are synthesized again by the half mirror HM, and then the spatial filter. It was spread by SF and projected on the screen 55. In this case, as shown in FIG. 15, the light 58 is projected in a circular pattern on the screen 55 corresponding to the diffusion direction by the spatial filter SF, and an interference pattern consisting of bright and dark stripes is clearly observed. It was. That is, the experiments shown in FIGS. 12 to 15 also confirmed that the coherence of the laser beams L121a and L121b having the same wavelength oscillated from different laser light sources 50a and 50b is remarkably reduced. In the experiments shown in FIGS. 12 to 15, a commercially available semiconductor pumped solid state (DPSS) laser that oscillates laser light having a wavelength of 532 nm was used as the laser light sources 50a, 50b, and 50c.

  Therefore, according to the simultaneous exposure using a plurality of laser light sources based on the interference characteristics of the laser light, the light generated from the same laser light source among the plurality of laser light sources (that is, one light source) Only the interference fringes 11a and 11b between the reference light oscillated from the laser light source and the object light as reproduction light obtained by diffracting the reference light as reproduction illumination light are recorded on the hologram recording material 20. Become so. That is, when the laser light generated from each of the plurality of laser light sources is exposed to the hologram recording material as reference light that also functions as reproduction illumination light, the hologram recording material 20 has the same number of laser light sources. Only a number of interference fringes are formed.

  From the above, in the example of FIG. 11, when the first reference light L1r and the second reference light L2r are made of light generated from different laser light sources, the first reference light L1r and the second reference light L2r are Even if the lights have the same wavelength, they do not interfere with each other. That is, light for forming the first interference fringe 11a (first reference light L1r and first object light L3o) and light for forming the second interference fringe 11b (second reference light L2r and second object light) L4o) is generated from another laser light source, the light for forming the first interference fringe 11a (the first reference light L1r and the first object light L3o) and the second interference fringe 11b are formed. Light (second reference light L2r and second object light L4o) do not interfere with each other. Therefore, one of the first reference light L1r and the first object light L3o for forming the first interference fringe 11a, and the second reference light L2r and the second object light L4o for forming the second interference fringe 11b. Unnecessary interference fringes formed by interference with either are not recorded on the hologram recording material 20. This prevents reproduction light that is diffracted in an unintended direction by unnecessary interference fringes, and bright reproduction light can be obtained by diffraction at the first interference fringes 11a and the second interference fringes 11b.

  The hologram recording material 20 on which the first interference fringes 11 a and the second interference fringes 11 b are recorded is then subjected to a post-processing step, and the hologram 10 can be obtained from the hologram recording material 20. The content of the post-processing varies depending on the material forming the hologram recording material 20, but as an example, the ultraviolet recording and the heat treatment can be performed on the hologram recording material 20 as a series of post-processing.

  According to the present embodiment as described above, light of different wavelengths is diffracted by the incident lights L1a and L1b from the same direction d1 to the hologram 10. That is, for example, when white light is incident on the hologram 10 at a predetermined incident angle, the reproduction lights L3a and L3b of a plurality of colors can be observed. In particular, according to the present embodiment, light L3a and L3b having different wavelengths from the same direction d1 are diffracted in the same direction d3, and the reproduction lights L3a and L3b of a plurality of colors can be observed simultaneously.

  The holograms 10 that diffract the reproduction lights L3a and L3b with a plurality of colors are difficult to obtain, but each has a sensitivity to a laser light source capable of generating light of each color and light of each color. By preparing the hologram recording material, replication (counterfeiting) by contact copy becomes possible.

  On the other hand, according to the manufacturing method described above, such a hologram 10 is produced by exposing with laser beams L1r and L2r having a single wavelength. That is, in actual use, the second interference fringes 11b are obtained by using light (first wavelength light) having a wavelength different from that of light (second wavelength light) intended to reproduce the second image 12b. Is recorded. In general, the number of high-power laser light sources that can be used for recording interference fringes is limited. For this reason, the wavelength of laser light generated at high output is also limited to a specific wavelength. Therefore, for example, the wavelength (second wavelength) of light that enters the hologram 10 from the first direction d1 and satisfies the Bragg reflection condition of the second interference fringe 11b cannot be generated from a high-power laser light source. For example, if the light is to display yellow with a wavelength of about 570 to 580 nm, forgery by contact copy of the hologram 10 can be effectively made difficult. The wavelength of the light that enters the hologram 10 from the first direction d1 and satisfies the Bragg reflection condition of the second interference fringe 11b is the hologram of the reference light L2r and the object light L4o when the second interference fringe 11b is recorded. By controlling the incident angle to the recording material 20, it can be adjusted within a range satisfying the Bragg condition.

  Further, according to the present embodiment, the first interference fringe 11a and the second interference fringe 11b are simultaneously recorded by simultaneously exposing the hologram recording material 20 with the light L1r, L2r, L3o, and L4o having a single wavelength. To go. Therefore, the hologram 10 can be efficiently produced by a single exposure process. That is, not only can the hologram 10 be given excellent resistance to counterfeiting by contact copying, but the hologram 10 can be easily and inexpensively manufactured.

  In particular, in the present embodiment, the light L1a having the first wavelength and the light L1b having the second wavelength that are intended to be diffracted at the time of use in the hologram 10 to be manufactured enter the hologram 10 from the same first direction. Therefore, the incident directions of the first reference light L1r and the second reference light L2r having the first wavelength on the hologram recording material 20 for recording the first interference fringe 11a and the second interference fringe 11b are different directions. However, since the first reference light L1r and the second reference light L2r having the same wavelength (first wavelength) are light generated by different laser light sources, they do not interfere with each other. For this reason, when recording the 1st interference fringe 11a and the 2nd interference fringe 11b in parallel by simultaneous exposure, the light for recording the first interference fringe 11a (the first reference light L1r and the first object light L3o) and Unnecessary bright and dark stripes (interference fringes) formed by interference with the light (second reference light L2r and second object light L4o) for recording the second interference fringes 11b are recorded on the hologram recording material 20. Nor.

  Furthermore, according to the present embodiment, since the hologram 10 is produced using the laser beams L1r and L2r having a single wavelength, the hologram recording material 20 for recording the interference fringes 11a and 11b is used as the hologram recording material 20. A material exhibiting photosensitivity in a wavelength region near one wavelength can be selected. Also in this respect, not only can the hologram 10 be provided with excellent resistance to forgery as described above, but the hologram 10 can be easily and inexpensively manufactured.

  In addition, according to the present embodiment, a three-dimensional image is reproduced by the first reproduction light L3a diffracted by the first interference fringes 11a. Therefore, it is possible to impart excellent designability and high discrimination to the first image 12a reproduced by the first interference fringes 11a. Such a hologram 10 can effectively function as an authenticity indicating body for indicating authenticity because determination of authenticity is extremely easy.

  Furthermore, according to the present embodiment, the two-dimensional pattern 12b is different from the image 12a reproduced by the diffracted light L3a at the first interference fringe 11a, and the diffracted light L3b at the second interference fringe 11b It will be played. Design properties, information, and the like can be imparted to the two-dimensional pattern, whereby the hologram 10 can effectively function as an authenticity indicator that indicates authenticity.

  Furthermore, according to the present embodiment, the second image 12b is reproduced as a two-dimensional pattern having no thickness. In addition, the second image 12b reproduced as a two-dimensional pattern is positioned on the surface of the hologram 10. Therefore, the second image 12b is not reproduced with a different color at a position greatly deviated in the plane direction parallel to the hologram 10. As a result, it is possible to prevent the second image 12b from being blurred and viewed even when the hologram is observed from a position far away.

  Note that various modifications can be made to the above-described embodiment. Hereinafter, an example of modification will be described with reference to the drawings. In the drawings used in the following description, the same reference numerals as those used for the corresponding parts in the above-described embodiment are used, and redundant descriptions are omitted.

  In the embodiment described above, the first image 12a reproduced when the first reproduction illumination light L1a having the first wavelength incident from the first direction d1 is diffracted by the first interference fringes 11a, and from the first direction d1. An example in which both the second image 12b reproduced by diffracting the incident second reproduction illumination light L1b having the second wavelength by the second interference fringe 11b is observed from at least one direction, that is, Although an example in which the first image 12a reproduced by the first interference fringe 11a and the second image 12b reproduced by the second interference fringe 11b can be observed at the same time has been shown, the present invention is not limited to this. A direction in which the first reproduction illumination light L1a having the first wavelength incident from the first direction d1 is diffracted by the first interference fringe 11a, and a second reproduction illumination light L1b having the second wavelength incident from the first direction d1 is the second. The direction diffracted by the interference fringes 11b may be different. That is, the first image 12a and the second image 12b are not observed at the same time, and the two images 12a and 12b can be observed from different directions by changing the observation direction. Good.

  In the above-described embodiment, the example in which the second image 12b reproduced by the second interference fringe 11b is formed of a two-dimensional character string pattern is shown, but the present invention is not limited thereto. For example, the second interference fringes 11b may scatter-reflect incident light that satisfies the Bragg condition. That is, the second interference fringes 11b may function as a holographic scattering plate. Alternatively, the second interference fringes 11b may reflect a parallel incident light beam that satisfies the Bragg condition as a parallel light beam. That is, the second interference fringe 11b may function as a holographic mirror. In addition, when the 2nd interference fringe 11b functions as a holographic mirror, the diffracted light by the 2nd interference fringe 11b becomes a parallel light beam irrespective of the diffraction direction. Therefore, the diffracted light at the second interference fringe 11b can be clearly observed without causing the diffracted light at the second interference fringe 11b to cause defects such as image blurring.

  Furthermore, in the above-described embodiment, the example in which the first image 12a reproduced by the first interference fringe 11a is a three-dimensional image has been shown, but the present invention is not limited thereto. The first image 12a reproduced by the first interference fringes 11a may be configured as a two-dimensional pattern in which one or more selected from the group consisting of letters, numbers, symbols, and patterns are arranged, or a holo It may be configured as a graphic scattering plate or a holographic mirror. When the first image 12a is composed of one or more two-dimensional patterns selected from the group consisting of letters, numbers, symbols, and patterns, the letters, numbers, The symbol or pattern may be sized to fall within a 72 μm square area.

  Further, when the first image 12a and the second image 12b are configured as a two-dimensional pattern, a holographic scattering plate, or a holographic mirror, the first reproduction of the first wavelength incident from the first direction d1. The first reproduction light L3b obtained by diffracting the illumination light L1a by the first interference fringe 11a and the second reproduction light L1b having the second wavelength incident from the first direction d1 are diffracted by the second interference fringe 11b. Both the two reproduction lights L3a may be observed from the same direction. Furthermore, when the first image 12a and the second image 12b are configured as a two-dimensional pattern, a holographic scattering plate, or a holographic mirror, the first reproduction of the first wavelength from the first direction d1. By diffracting the first image 12a reproduced by diffracting the illumination light L1a with the first interference fringe 11a and the second reproduction illumination light L1b having the second wavelength from the first direction d1 with the second interference fringe 11b The second image 12b to be reproduced is observed from the same direction and at positions shifted from each other along the normal direction to the surface of the volume hologram 10 (in other words, different heights). It may be played back (as observed at the position in the direction). Even in such a modification, the two-dimensional pattern reproduced by the diffracted light at the first interference fringe 11 and the two-dimensional pattern reproduced by the diffracted light at the second interference fringe 11a are shifted in the height direction. Therefore, the image reproduced by the hologram 10 is observed as a three-dimensional image as a whole, and excellent designability and high discriminability can be imparted to the hologram 10.

  Further, in the above-described embodiment, the example in which the interference fringes 11a and 11b are recorded on the hologram recording material 20 using the reproduction light from the hologram masters 30 and 40 as the object light has been described. However, the present invention is not limited thereto. . For example, the reflected light from the model may be incident on the hologram recording material 20 as object light and the interference fringes 11 a and 11 b may be recorded on the hologram recording material 20.

  Furthermore, in the above-described embodiment, the example in which the first interference fringe 11a and the second interference fringe 11b function as a reflection type volume hologram has been described. However, at least one of the first interference fringe 11a and the second interference fringe 11b is illustrated. One of them may function as a transmission type volume hologram.

  Furthermore, in the above-described embodiment, the first hologram master 30 is not limited to this example in which the first hologram master 30 is made of a reflective volume hologram, and the first hologram master may be made of a transmission volume hologram. When the first hologram master is a transmission volume hologram, the first interference fringes 11a can be recorded on the hologram recording material 20 as follows. First, a first hologram master made of a transmission volume hologram is arranged on one side of the hologram recording material 20, and coherent light is incident on the first hologram master so as to satisfy the Bragg condition. As a result, the first object light as the diffracted light is incident from the first hologram master toward the hologram recording material 20, and the first reference as the zero-order light transmitted through the first hologram master 30 without being diffracted. Light enters. Thereby, the first interference fringes 11a can be recorded on the hologram recording material 20 in correspondence with the bright and dark fringe pattern formed by the interference of the first reference light and the first object light. Further, as in the case of the first hologram master 30, in the above-described embodiment, the example in which the second hologram master 40 is made of a reflection type volume hologram is shown, but the present invention is not limited to this, and the second hologram master is made of a transmission type volume hologram. It may be made to become.

  Further, in the above-described embodiment, the example in which the first interference fringe 11a and the second interference fringe 11 are recorded at the same timing is shown, but the present invention is not limited to this. For example, as shown in FIGS. 10 and 11, the step of recording the first interference fringe 11a and the step of recording the second interference fringe 11b may be performed at different timings. In the modification shown in FIGS. 10 and 11, the first interference fringes 11a are formed in the first region 21a (see FIG. 2) in the hologram recording material 20, and the hologram recording is a region other than the first region. The second interference fringes 11b are formed in the second region 21b (see FIG. 2) in the material 20.

  In the step of recording the first interference fringes shown in FIG. 10, the hologram recording material 20 is irradiated with the first reference light L1r having the first wavelength along the first direction d1 from the one surface 20b side. The first hologram original plate 30 described above is arranged on the other surface 20a side of the hologram recording material 20, and the first reference light L1r transmitted through the hologram recording material 20 is subjected to Bragg conditions to the first hologram original plate 30. Incident so as to satisfy. As a result, as described above, the first object light L3o as reproduction light (diffracted light) from the first hologram master 30 is applied to the hologram recording material 20 along the direction centering on the third direction d3. The first interference fringes 11 a are recorded on the hologram recording material 20.

  In the illustrated modification, as described above, the first interference fringes 11a are formed only in a part of the region of the hologram recording material 20, and other hologram recording materials 20 in which the first interference fringes 11a are not recorded. The second interference fringes 11b are recorded in the area. For this reason, as shown in FIG. 10, while the laser beam from the laser light source is irradiated, the first mask 36 is formed on one surface 20b of the hologram recording material 20 on which the laser beam irradiation is performed. Has been placed. The first mask 36 blocks the incidence of laser light on the second region 21b (see FIG. 2) of the hologram recording material 20 on which the second interference fringes 11b are recorded. As a result, during the process of recording the first interference fringes 11a, photosensitivity proceeds only in the first region 21a (see FIG. 2) of the hologram recording material 20, and photosensitivity in the second region 21b of the hologram recording material 20 is prevented.

  Further, as shown in FIG. 10, a light shielding layer 37 is provided on the surface of the first hologram master 30 that is not facing the hologram recording material 20, as in the above-described embodiment. Recording of interference fringes that are not performed is prevented.

  On the other hand, in the step of recording the second interference fringes shown in FIG. 11, the hologram recording material 20 is irradiated with the second reference light L2r having the first wavelength from the one surface 20b side along the second direction d2. . The second hologram original plate 40 described above is arranged on the other surface 20a side of the hologram recording material 20, and the second reference light L2r that has passed through the hologram recording material 20 is transmitted to the second hologram original plate 40 under Bragg conditions. Incident so as to satisfy. As a result, as described above, the second object light L4o as the reproduction light (diffracted light) from the second hologram master 40 is applied to the hologram recording material 20 along the direction centering on the fourth direction d4. The second interference fringes 11 b are recorded on the hologram recording material 20.

  In the illustrated modification, as shown in FIG. 11, the second surface 20b of the hologram recording material 20 on which the laser light irradiation is performed is irradiated on the second surface 20b while the laser light from the laser light source is irradiated. A mask 46 is arranged. The second mask 46 blocks the incidence of laser light on the first region 21a (see FIG. 2) of the hologram recording material 20 on which the first interference fringes 11a are recorded. As a result, during the process of recording the second interference fringes 11b, photosensitivity proceeds only in the second region 21b (see FIG. 2) of the hologram recording material 20, and photosensitivity in the first region 21a of the hologram recording material 20 is prevented. Further, as shown in FIG. 11, a light shielding layer 47 is provided on the surface of the second hologram master 40 on the side not facing the hologram recording material 20, as in the above-described embodiment. Recording of interference fringes that are not performed is prevented.

  As described above, the first interference fringes 11a and the second interference fringes 11b can be recorded on the hologram recording material 20 at different timings. Note that either the step of recording the first interference fringe 11a and the step of recording the second interference fringe 11b may be performed first.

  In such a modification, the first interference fringes 11a and the second interference fringes 11b are formed at different timings. Accordingly, the first reference light L1r and the first object light L3o for forming the first interference fringe 11a and the second reference light L2r and the second object light L4o for forming the second interference fringe 11b are holograms. The recording material 20 is not exposed simultaneously. Therefore, one of the first reference light L1r and the first object light L3o for forming the first interference fringe 11a, and the second reference light L2r and the second object light L4o for forming the second interference fringe 11b. Unnecessary interference fringes formed by interference with either are not recorded on the hologram recording material 20. This prevents reproduction light that is diffracted in an unintended direction by unnecessary interference fringes, and bright reproduction light can be obtained by diffraction at the first interference fringes 11a and the second interference fringes 11b.

  In addition, the first reference light L1r and the first object light L3o for forming the first interference fringe 11a and the second reference light L2r and the second object light L4o for forming the second interference fringe 11b are the same. It is light of wavelength. Therefore, the second reference light L2r may be generated from the same laser light source that generates the first reference light L1r. As a result, in order to record the two interference fringes 11a and 11b intended to reproduce an image with different colors on the hologram recording material 20, it is only necessary to prepare a single laser light source.

  In addition, according to the hologram manufacturing method described above, by appropriately using the masks 36 and 46 during the production of the first interference fringe 11a and the second interference fringe 11b, the region 21a where the first interference fringe 11a is recorded, A region 21 b where the second interference fringes 11 b are recorded is divided in the hologram recording material 20. Accordingly, during the recording of the interference fringes recorded later (second interference fringe 11b in the above example), the reference fringes and object light for forming the interference fringes are recorded so far (in the above example). Then, it is possible to prevent the first interference fringes 11a) from being diffracted in an unintended direction. Thereby, it is possible to prevent unnecessary interference fringes from being recorded on the hologram recording material 20 due to interference between the reference light or object light and light diffracted in an unintended direction.

  In addition, although the some modification with respect to embodiment mentioned above was demonstrated above, naturally, it is also possible to apply combining several modifications suitably.

10 Volume hologram (hologram)
10a 1st surface 10b 2nd surface 11a 1st interference fringe 11b 2nd interference fringe 12a 1st image 12b 2nd image 20 Hologram recording material 20a 1st surface (one surface)
20b Second surface (the other surface)
21a 1st area | region 21b 2nd area | region 25 Lamination original plate 30 1st hologram original plate 35 Hologram recording material (hologram recording material for 1st hologram original plates)
35a 1st surface (the other surface)
35b 2nd surface (one surface)
36 mask (first mask)
37 Light-shielding layer 40 Second hologram master 45 Hologram recording material (hologram recording material for second hologram master)
45a First surface (the other surface)
45b 2nd surface (one surface)
46 Mask (second mask)
47 Light-shielding layer 48 Mask (light-shielding mask)
49 Holographic scattering plate

Claims (11)

A first interference fringe that diffracts light having a first wavelength incident from the first direction; and a second interference fringe that diffracts light having a second wavelength different from the first wavelength incident from the first direction. A method for producing a volume hologram, comprising:
The first reference light having the first wavelength is incident on the hologram recording material from the first direction, and the first object light having the first wavelength is incident on the hologram recording material, so that the first interference fringes are incident on the hologram recording material. Recording process;
The second reference light having a first wavelength is incident on the hologram recording material from a second direction different from the first direction, and the second object light is incident on the hologram recording material, so that the second interference fringes are Recording on a hologram recording material,
The step of recording the first interference fringe and the step of recording the second interference fringe are performed in parallel;
The first reference light is generated from a first laser light source, and the second reference light is generated from a second laser light source different from the first laser light source,
A method for producing a volume hologram. At least the light of the first wavelength from the first direction from the direction in which the reproduction light formed by diffracting the light of the second wavelength from the first direction by the second interference fringe is observed. The second direction is determined so that the reproduction light diffracted by the stripes can be observed.
The method for producing a volume hologram according to claim 1. In the step of recording the first interference fringes, after the first reference light incident on the hologram recording material from one side of the hologram recording material is transmitted through the hologram recording material, The first hologram master made of a reflective volume hologram arranged on the other surface side is incident so as to satisfy the Bragg condition, and the diffracted light from the first hologram master is incident on the hologram recording material as first object light. Incident from the other surface side,
In the step of recording the second interference fringes, after the second reference light incident on the hologram recording material from the one surface side is transmitted through the hologram recording material, the other surface of the hologram recording material Is incident on a second hologram master composed of a reflection type volume hologram arranged on the side so as to satisfy the Bragg condition, and diffracted light from the second hologram master is incident on the hologram recording material as second object light. Incident from the side of the surface,
The method for producing a volume hologram according to claim 1 or 2. In the step of recording the first interference fringes, out of the light incident so as to satisfy the Bragg condition to the first hologram master composed of a transmission type volume hologram arranged on one side of the hologram recording material, The diffracted light from the first hologram master is used as the first object light, and the zero-order light from the first hologram master of the light is used as the first reference light. Incident from the side of the surface,
In the step of recording the second interference fringes, of the light incident so as to satisfy the Bragg condition to the second hologram master composed of a transmission volume hologram disposed on one side of the hologram recording material, The diffracted light from the second hologram master is used as the second object light, and the 0th-order light from the second hologram master of the light is used as the second reference light. Incident from the side of the surface,
The method for producing a volume hologram according to claim 1 or 2. A step of recording the first interference fringe and a step of recording the second interference fringe in a state in which a laminated original obtained by superimposing the first hologram original and the second hologram original is laminated on the hologram recording material; Carried out,
The method for producing a volume hologram according to claim 3 or 4, wherein: A step of manufacturing the second hologram master,
The second object light is configured such that a two-dimensional pattern located on a plane parallel to the surface of the volume hologram is reproduced by diffracting incident light in which the second interference fringes satisfy the Bragg condition. And
The step of manufacturing the second hologram master is:
A step of exposing the hologram recording material for the second hologram original plate from the side on which the mask is arranged in a state where a mask having the same pattern as the two-dimensional pattern is arranged on the hologram recording material for the second hologram original plate When,
In the state where the holographic scattering plate is laminated on the exposed hologram recording material for the second hologram original plate, the reference light and the object light as the diffracted light from the holographic scattering plate are used as the hologram recording material for the second hologram original plate. And making it incident on
The method for producing a volume hologram according to any one of claims 3 to 5, wherein: The first object light is configured such that a three-dimensional image is reproduced by diffracting incident light in which the first interference fringes satisfy the Bragg condition.
The method for producing a volume hologram according to claim 1, wherein the volume hologram is produced. The second object light is a parallel light beam,
The method for producing a volume hologram according to claim 1, wherein the volume hologram is produced. The second object light is configured such that a two-dimensional pattern located on a plane parallel to the surface of the volume hologram is reproduced by diffracting incident light in which the second interference fringes satisfy the Bragg condition. ing,
The method for producing a volume hologram according to claim 1, wherein the volume hologram is produced. The first object light is configured such that a two-dimensional pattern located on a plane parallel to the surface of the volume hologram is reproduced by diffracting incident light in which the first interference fringes satisfy the Bragg condition. ,
The second object light is configured such that a two-dimensional pattern located on a plane parallel to the surface of the volume hologram is reproduced by diffracting incident light in which the second interference fringes satisfy the Bragg condition. And
The position of the two-dimensional pattern reproduced by diffracting the light of the first wavelength from the first direction with the first interference fringe and the light of the second wavelength from the first direction are the second The first object light and the second object light are configured such that the position of the two-dimensional pattern reproduced by diffracting with interference fringes is shifted in the normal direction to the surface of the volume hologram. ,
The method for producing a volume hologram according to claim 1, wherein the volume hologram is produced. The two-dimensional pattern is one or more selected from the group consisting of letters, numbers, symbols and patterns,
One letter, number, symbol or pattern constituting the two-dimensional pattern is sized to fall within a 72 μm square area.
The method for producing a volume hologram according to claim 9 or 10, wherein:

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