JP5407603B2 - Hologram and article with hologram attached - Google Patents

Description

  The present invention relates to a hologram that reproduces a color image, and more particularly to a hologram that includes information that is difficult to read under normal viewing conditions as a hidden image. The present invention also relates to an article to which a hologram including a hidden image containing information that is difficult to read under normal observation conditions is attached.

  Conventionally, as an anti-counterfeiting measure for cards, passports, identification cards, gift certificates, etc., a hologram (hologram label) has been attached to these articles. In recent years, it has become possible to record a complicated three-dimensional image reproduced in color on a hologram. By using a hologram, the design of an article to which the hologram is attached can be improved. It is like that.

  When a hologram is used for the purpose of preventing counterfeiting, it is difficult for the hologram to be counterfeited, and it is necessary to make it possible to easily determine the authenticity of the hologram itself. Unfortunately, however, hologram counterfeiting techniques have improved in recent years. In addition, materials for producing holograms are becoming easier to obtain. From such a situation, a counterfeit hologram that looks similar may be distributed and the counterfeit hologram may be overlooked.

  In order to deal with such a problem, a display body (hidden image) that displays authentication information can be displayed under special conditions separately from an image (visualized image) observed in a normal observation state ( Studies on recording media have also been conducted (for example, Patent Document 1 and Patent Document 2).

JP 2002-254546 A JP-A-5-262086

  However, in the display disclosed in Patent Document 1, a latent image forming structure layer in which a hidden image is recorded is provided separately from a hologram layer in which an image (a visible image) that is normally observed is recorded. Therefore, the thickness of the display body becomes very thick as compared with a display body made of a single-layer hologram, and the manufacturing cost of the display body becomes extremely expensive.

  On the other hand, the display body disclosed in Patent Document 2 is configured as a printed matter formed using special ink. On this display body, a visible image that can be observed in a normal observation state and a hidden image that can be observed only under specific observation conditions are printed. And when observing a hidden image, a visible image cannot be observed. Further, in the display body of Patent Document 2, printed images (a visible image and a latent image) are observed, and the image cannot be reproduced three-dimensionally like a hologram. That is, the display body of Patent Document 2 cannot display an image in a floating manner, and even if the observation direction is changed, the appearance of the observed image changes according to the observation direction. No. Furthermore, in the display body of Patent Document 2, the area for printing the visible image and the area for printing the latent image cannot overlap, thereby limiting the design of the visible image and the latent image. In other words, the image displayed on the display body of Patent Document 2 can have a design property significantly lower than the design property of the image reproduced by the hologram, and is compared with the design property of the image reproduced by the hologram. Cannot be a target.

  The present invention has been made in consideration of such points, and relates to a hologram for reproducing a color image, and in particular, it is difficult to read under normal viewing conditions apart from an image observed under normal viewing conditions. Hidden images containing information also provide recorded holograms.

  The hologram according to the present invention is a hologram in which interference fringe data for reproducing a color image is recorded. The color image is a first color component image and a second color different from the first color component. The first color component image includes a hidden image that displays information, and the second color component image includes the first color component image and the first color component image. A noise image that makes it difficult to read the hidden image in the color image including at least an image of the second color component is included.

  In the hologram according to the present invention, the color image further includes an image of a third color component different from both the first color component and the second color component, and the image of the third color component is A color image may include a noise image that makes it difficult to read the hidden image.

  In the hologram according to the present invention, the peak wavelength of the light that displays the image of the first color component that constitutes the color image is that of the light that displays the image of the second color component that constitutes the color image. It may be shorter than the peak wavelength and longer than the peak wavelength of the light for displaying the image of the third color component constituting the color image.

  Further, in the hologram according to the present invention, the image of the first color component constituting the color image is displayed in green, the image of the second color component constituting the color image is displayed in red, The image of the third color component constituting the color image may be displayed in blue.

  Furthermore, in the hologram according to the present invention, the noise image included in the second color component image is obtained by superimposing the first color component image and the second color component image on the first color component image. The information of the hidden image included in the image of one color component is configured to be difficult to read, and the noise image included in the image of the third color component includes the image of the first color component and the image of the first color component. When the image of the third color component is superimposed, the information of the hidden image included in the image of the first color component may be difficult to read.

  Furthermore, in the hologram according to the present invention, the noise image may be formed as a random gradation pattern.

  Furthermore, in the hologram according to the present invention, the information of the hidden image may be readable through a member that transmits only light in a specific wavelength band.

  Furthermore, in the hologram according to the present invention, the color image may be a three-dimensional image.

  Furthermore, in the hologram according to the present invention, the information may be authentication information.

  Further, in the hologram according to the present invention, the color image includes an image having some meaning, and the region where the hidden image and the noise image are formed in the color image is colored with a random coloring pattern. You may make it.

  Furthermore, the hologram according to the present invention may be formed as a computer-generated hologram.

  Furthermore, an article according to the present invention is characterized in that any one of the above-described holograms according to the present invention is attached.

FIG. 1 is a front view showing a color image reproduced by a hologram. FIG. 2 is a front view showing an image of the first color component constituting the color image of FIG. FIG. 3 is a front view showing an image of a second color component constituting the color image of FIG. FIG. 4 is a front view showing an image of the third color component constituting the color image of FIG. FIG. 5 is a diagram illustrating a state when a hologram is used. In FIG. 5, the hologram is shown in a cross section parallel to both the traveling direction of the illumination light to the hologram and the normal direction to the surface of the hologram. FIG. 6 is a flowchart for explaining a method of calculating interference fringe data recorded on a hologram. FIG. 7 is a diagram illustrating a hidden image, a noise image, and a superimposed image of the hidden image and the noise image, which are planarized. FIG. 8 is a diagram for explaining the relationship between the traveling direction of the illumination light and the traveling direction of the reproduction light (the diffraction direction of the illumination light). In FIG. 8, the hologram is shown in a cross section parallel to both the traveling direction of the illumination light to the hologram and the normal direction to the surface of the hologram. FIG. 9 is a diagram for explaining a correspondence relationship between a unit area defined on the hologram recording surface and a unit area defined on the original image. In FIG. 9, the hologram is shown in a cross section parallel to both the traveling direction of the illumination light to the hologram and the normal direction to the surface of the hologram. FIG. 10 is a diagram for explaining the correspondence between calculation points defined on the hologram recording surface and point light sources defined on the original image. In FIG. 10, the hologram is shown in a cross section parallel to both the direction orthogonal to the traveling direction of the illumination light to the hologram and the normal direction to the surface of the hologram. FIG. 11 is a plan view showing a holographic film-like medium. FIG. 12 is a diagram for explaining the operation of the hologram, and is a diagram showing the hologram in the same cross section as FIG. FIG. 13 is a view for explaining the operation of the hologram, and is a view showing the hologram in the same cross section as FIG. FIG. 14 is a view for explaining the operation of the hologram, and is a view showing the hologram in the same cross section as FIG. FIG. 15 is a view for explaining the operation of the hologram, and is a view showing the hologram in the same cross section as FIG. FIG. 16 is a view for explaining the operation of the hologram, and is a view showing the hologram in the same cross section as FIG. FIG. 17 is a diagram for explaining the operation of the hologram, and shows the hologram in the same cross section as FIG. FIG. 18 is a view for explaining the operation of the hologram, and shows the hologram in the same cross section as 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.

  1 to 18 are diagrams for explaining an embodiment according to the present invention. Among these, FIG. 1 is a diagram showing an example of a color image reproduced by a hologram, and FIGS. 2 to 4 are diagrams showing a decomposition image of the color image of FIG. FIG. 5 is a diagram illustrating an example of a situation in which a hologram is used. 6 to 11 are diagrams for mainly explaining an example of a method for producing a hologram. 12-18 is a figure for demonstrating the effect | action of a hologram.

  In this embodiment described below, an example in which the hologram according to the present invention is produced as a computer-generated hologram will be described. However, as will be described later, the hologram according to the present invention does not necessarily have to be a computer-generated hologram, and can be produced, for example, by a normal hologram photographing method as a volume hologram. That is, the present invention can be applied to other types of holograms without being restricted to the application to the computer-generated holograms exemplified below.

  The hologram 20 according to the present embodiment is a hologram 20 on which interference fringe data related to the color image 30 is recorded. Then, as shown in FIG. 5, when white light, for example, illumination light La from the luminaire 12 is illuminated on the hologram, in a specific direction determined according to the illumination direction of the light La to the hologram 20. The image 30 is reproduced in color by the reproduction light Lb, and the observer 20 can observe the color image 30.

  In the hologram 20 according to the present embodiment, as shown in FIG. 1, the image 30 reproduced by the hologram 20 includes a sphere 36 and two rings 38 extending around the sphere 36 in a band shape. A portion of the sphere 36 hidden by the ring 38 is also hidden by the ring 38 in the reproduced image. That is, when viewed from a certain viewpoint, a hidden surface erasing process is performed such that the portion hidden by the object in front is not visible, and the hologram reproduces the recorded image in three dimensions. For details on the hidden surface removal processing, refer to “3D Image Conference '99 -3D Image Conference'99” Lecture Collection CD-ROM (June 30-July 1, 1999 at Kogakuin University Shinjuku Campus), paper See "Image type binary CGH (3) by EB drawing-Improvement of stereoscopic effect by hidden surface removal and shading".

  The surface of the sphere 36 is divided into a number of areas. Many areas forming the surface of the sphere 36 are colored with a random coloring pattern. The term “coloring with a random coloring pattern” as used herein means that the object to be colored is irregularly or regularly divided into a large number of areas, and the color that colors each of the large numbers of areas is different for each colored area. It means that it is determined irregularly without depending on the position, that is, without being associated with the position of each colored area.

  On the other hand, each ring 38 is constituted by a character string formed by continuously arranging the characters “GENUINE”. The character string forming each ring 38 is colored white.

  The hologram 20 functions as a display body that displays authenticity as related to a character string such as “GENUINE” of a ring forming a part of the color image 30 to be reproduced. That is, the hologram 20 shows its authenticity by authenticity determination information to be described later, and an article 15 (two-dot chain line in FIG. 5) to which the hologram 20 is attached, such as banknotes, stock certificates, cards, documents, etc. Works to show authenticity.

  Since the image 30 reproduced by the hologram 20 can be displayed in color, it naturally has a plurality of separated images 31, 32, 33 of color components displayed in different colors. As described above, in the present embodiment, the hologram 20 is configured as a relief-type rainbow hologram of a computer-generated hologram that hardly exhibits wavelength selectivity. Accordingly, the interference fringe data related to the color component images 31, 32, and 33 are displayed in various colors depending on the illumination direction and the observation direction. However, when viewed from any one viewing direction, the images 31, 32, and 33 of the plurality of color components are displayed in different colors without being displayed in the same color.

  In the present embodiment, when the color image 30 in FIG. 1 is reproduced in a specific direction corresponding to the illumination direction of the illumination light, the image 30 is an additive color mixture of the three primary color component images 31, 32, and 33. Consists of. That is, the color image 30 reproduced by the hologram 20 includes the first color component image 31 displayed in green shown in FIG. 2 and the second color component displayed in red shown in FIG. And an image 33 of the third color component displayed in blue shown in FIG. In each of the color component images 31, 32, and 33, each color is expressed by, for example, 256 gradations from 0 to 255. As a result, the hologram 20 can reproduce the image 30 in full color.

  The image 31 of the first color component that is displayed in green and that constitutes the color image 30 is composed of light in a first wavelength band having a peak wavelength in the range of 495 nm to 565 nm, for example. The image 32 of the second color component that is displayed in red and that constitutes the color image 30 is constituted by light of a second wavelength band having a peak wavelength in the range of 600 nm to 780 nm, for example. The image 33 of the third color component that is displayed in blue and forms the color image 30 is configured by light in a third wavelength band having a peak wavelength in the range of 380 nm to 490 nm, for example. Therefore, the peak wavelength of the light forming the first color component image constituting the color image 30 is shorter than the peak wavelength of the light forming the second color component image forming the color image 30, and the color image 30 It is longer than the peak wavelength of the light that forms the image of the third color component.

  When the hologram 20 is produced as a computer-generated hologram, the wavelength band of light forming each color component image 31, 32, 33 is a narrow range centered on the peak wavelength. In particular, when a computer-generated hologram produced with high accuracy is measured with high accuracy, the light that forms each color component image 31, 32, 33 is theoretically only light of a specific wavelength (light of a peak wavelength). Thus, it is configured.

  In the present embodiment, the first color component image 31 includes an image representing the sphere 36 and the two rings 38 around the sphere 36 described above by overlapping with the other color component images 32 and 33. Yes. As shown in FIG. 2, the first color component image 31 includes an image 31 a formed at a position corresponding to the surface of the sphere 36 by changing the gradation of the color component. The image 31a formed on the surface of the sphere 36 is configured as an image 31a that displays specific information. Specifically, in the first color component image 31, a letter “real” is present on the surface of the sphere 36. That is, the image 31 of the first color component includes an image 31a that displays authenticity determination information that the hologram is “real”.

  However, as shown in the figure, in the color image 30 displayed by superimposing the images of the first to third color components, it is difficult to read the authentication information of the image 31a formed on the surface of the sphere 36. That is, the image 31a displaying the authenticity determination information is formed as a hidden image 31a.

  On the other hand, each of the second color component image 32 and the third color component image 33 is also overlapped with the other color component images, and the two rings 38 around the sphere 36 and the sphere 36 described above. The image which expresses is included. The second color component image 32 and the third color component image 33 are each an area including an area in which the above-described image for displaying the authentication information is reproduced, that is, a sphere in the present embodiment. The noise image 32a, 33a reproduced on the surface of 36 is included.

  The noise image 32a included in the second color component image 32 includes a hidden image 31a formed of the first color component by overlapping the first color component image 31 and the second color component image 32. When simultaneously observed, it is configured to make it difficult to read the authenticity determination information of the hidden image 31a. In the present embodiment, the noise image 32a of the second color component is a random floor formed with only the second color component on the area occupied by the noise image, that is, on the surface of the sphere 36 in the present embodiment. It is configured as a key pattern. Specifically, the surface of the sphere 36 is divided into a number of areas, and the gradation of the second color component for each of the many areas forming the surface of the sphere 36 is the position on the sphere 36 of the area. It is set regardless.

  Similarly, the noise image 33a included in the third color component image 33 is a hidden image 31a composed of the first color component by overlapping the first color component image 31 and the third color component image 33. At the same time, it is configured to make it difficult to read the authentication information of the hidden image 31a when observed. In the present embodiment, the noise image 33 a of the third color component is formed as a random gradation pattern of only the third color component on the surface of the sphere 36. Specifically, the surface of the sphere 36 is divided into a number of areas, and the gradation of the third color component for each of the many areas forming the surface of the sphere 36 is the position on the sphere 36 of the area. It is set regardless.

  The hidden image 31a of the first color component image 31, the noise image 32a of the second color component image 32, and the noise image 33a of the third color component image 33 as described above are superimposed. By the combination, a random coloring pattern is formed on the surface of the sphere 36 in the color image 30 reproduced by the hologram 20.

  Incidentally, in order to reproduce the color image 30 described above, the hologram 20 has interference fringe data recorded on the film-like medium 22. Here, the interference fringe data refers to the intensity of the interference wave between the reference light composed of parallel light and the object light from the object forming the original image 30 to be reproduced, at each position on the film medium 22 of the hologram 20. It is data related to interference fringes specified by calculation at (calculation points described later). The computer-generated hologram 20 is typically produced by recording a concavo-convex shape as interference fringe data on a film-like medium 22. In the computer-generated hologram 20, the illumination light is diffracted by the uneven shape, and the image 30 is reproduced. Note that the recording medium 22 for recording interference fringe data is made of, for example, resin.

  As shown in FIG. 5, the hologram 20 according to the present embodiment includes a film-like medium 22 on which interference fringe data is recorded, and a reflection layer 24 that specularly reflects incident light. Light La from a lighting fixture or the like on which a hologram is incident from the observer 10 side (medium 22 side) passes through the medium 22 and is then specularly reflected by the reflective layer 24 and enters the medium 22. The light re-entering the medium 22 functions as the illumination light Lc and is diffracted by the medium 22 to form the diffracted light Lb.

  Next, a method for producing the hologram 10 as described above will be described.

  Usually, in mass production of computer-generated holograms, a master plate having an uneven shape is first produced. A large number of holograms are mass-produced by using this master plate as a prototype. Specifically, first, the surface of the master plate on which the concavo-convex shape is formed is coated with an ionizing radiation curable resin (for example, an ultraviolet curable resin) having fluidity. Next, the ionizing radiation curable resin is cured in a state in which the ionizing radiation curable resin having fluidity has entered the irregular shape of the master plate. In this way, an uneven shape obtained by transferring the uneven shape of the master plate by inverting the undulation is formed in the ionizing radiation curable resin as the medium. Thereafter, the cured ionizing radiation curable resin is peeled off from the master plate to obtain a hologram medium made of the cured ionizing radiation curable resin. By forming a reflective layer made of, for example, an aluminum vapor deposition film on one surface of the medium, the hologram 20 shown in FIG. 5 is obtained. Note that the uneven shape formed on the hologram may be referred to as an embossed pattern due to such a method for producing a hologram.

  Incidentally, as described above, the hologram in the present embodiment is formed as a computer-generated hologram (also called a computer-generated hologram (CGH)). Therefore, the fringe data is calculated by computing the defined model with a computer without actually irradiating the photosensitive material with the reference light and the object light and shooting on the medium made of the photosensitive material. And the uneven | corrugated shape of the master plate formed initially is determined based on the interference fringe data calculated by the computer. This uneven shape is very fine, and in many cases today, it is formed (recorded) using an electron beam drawing apparatus. Note that details of a method for forming a concavo-convex shape by electron beam drawing based on interference fringe data calculated by a computer are disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-191540, and a detailed description thereof is omitted here. To do.

  On the other hand, the calculation of the interference fringe data by the computer is performed according to the method shown in the flowchart of FIG. However, the method of calculating interference fringe data shown in FIG. 6 is merely an example, and interference fringes may be calculated by a method different from the method described below. Note that the general method for calculating interference fringe data in the production of a computer-generated hologram according to the flowchart of FIG. 6 is also referred to in known patents and non-patent documents. Therefore, here, the points that can be said to be characteristic in relation to the configuration or operational effects of the image reproduced by the hologram 20 of the present embodiment will be mainly described.

  Japanese Patent Laid-Open No. 2000-214751 is an example of a patent publication that refers to a rough calculation method of interference fringe data. In addition, as an example of a non-patent publication that refers to a rough calculation method of interference fringe data, “3D Image Conference '99 -3D Image Conference'99” Lecture Proceedings CD-ROM (June 30, 1999-7) May 1, Kogakuin University Shinjuku Campus), paper "Image-type binary CGH (3) by EB drawing-Improvement of stereoscopic effect by hidden surface removal and shading".

  As shown in FIG. 6, first, an image to be recorded on the hologram 20 is specified (step S1). Ideally, the original image defined in this step matches the image 30 reproduced by the hologram 20 shown in FIG.

  In the computer-generated hologram, generally, interference fringe data is calculated by calculating the intensity of the interference wave between the object light composed of monochromatic light and the reference light. In the following description, the first original image 41 is defined by modeling the image 31 of FIG. 2 displayed in green in the computer, and the image 32 of FIG. 3 displayed in red is modeled in the computer. Assume that the second original image 42 is defined, and the third original image 42 is defined by modeling the image 42 of FIG. 4 displayed in blue in the computer. In the following example, when the hologram 20 is illuminated with illumination light, the three color component images 31, 32, and 33 displayed in three primary colors are reproduced in specific directions. At this time, the observer can observe the full-color image 30 shown in FIG. 1 by the additive color mixture of the three color component images 31, 32 and 33 displayed in the three primary colors.

  As described above, the color image 30 shown in FIG. 1 includes the sphere 36 and the ring 38 that are three-dimensionally reproduced. Similarly, as shown in FIG. 9, the original images 41, 42, and 43 of the three primary color components are also defined to have a sphere 46 and a ring 48 that are three-dimensionally reproduced. Although the gradation patterns on the surface of the sphere 46 are different between the original images 41, 42, and 43 displayed in the three primary colors, the three-dimensional images represented by the three original images 41, 42, and 43 are the same. It has become. Therefore, in this process, it is necessary to define three original images 41, 42, 43. However, while preparing one stereoscopic image data (3DCG model), each original image 41, 42, It is possible to define three original images 41, 42, and 43 by texture mapping the three gradation patterns corresponding to 43.

  That is, when specifying the original image, the hidden image 31a of the first color component, the noise image 32a of the second color component, and the noise image 33a of the third color component to be reproduced are displayed on the three-dimensional surface. There is no need to design as a gradation pattern. As shown in FIG. 7, the hidden image 31a of the first color component, the noise image 32a of the second color component, the noise image 33a of the third color component, and further these images 31a, 32a, 33a What is necessary is just to design the color image which overlaps as a coloring pattern on a simple plane. Thereafter, by using a texture mapping technique, it is possible to define a stereoscopic original image 41, 42, 43 to be recorded on the hologram by converting into a colored pattern on the stereoscopic image. According to such a method, it is possible to very easily model the hidden image 31a that can display specific information and the noise images 32a and 33a that make the hidden image 31a invisible.

  Next, as shown in FIG. 6, a spatial arrangement relating to reproduction of the color image 30 is specified (step S2). Specifically, the position of the image 30 to be reproduced, the illumination direction of the illumination light illuminated on the hologram 20 to reproduce the image 30, and the reproduction direction for reproducing the image 30 constitute the hologram 20 The recording medium 22 is specified as a reference. The reproduction direction for reproducing the image 30 is, in other words, the traveling direction of the reproduction light for reproducing the image, and corresponds to the direction in which the illumination light that illuminates the hologram 20 in the defined illumination direction is diffracted by the hologram 20. Furthermore, it corresponds to the observation direction in which the reproduced image is observed. Further, a traveling direction of reference light described later is determined according to the illumination direction of the illumination light defined here, and a traveling direction of object light described later is determined in relation to the reproduction direction defined here. .

  The position at which the image 30 is reproduced can be appropriately set with respect to the recording surface of the medium 22. However, to reproduce the image 30 in three dimensions, it is effective to secure a large parallax. From the viewpoint of securing a large parallax, that is, from the viewpoint of increasing the change in the image that can be observed when the observation direction is changed, the image may be reproduced in the vicinity of the recording surface of the medium 22. It is valid.

  In addition, as for the illumination direction and the observation direction, a direction with high probability may be selected in consideration of the application of the hologram 20. For example, when the hologram 20 is used as an authentic display as in the present embodiment, the hologram 20 is an authentic display that is affixed to a relatively small article 15 (eg, a credit card) as an example. When used, it is expected that the observation direction is often substantially parallel to the normal direction to the surface of the hologram 20, as shown in FIG. At this time, as illumination light, it is expected that illumination light composed of white light is often illuminated on the hologram 20 from a direction inclined by approximately 45 ° with respect to the normal direction to the surface of the hologram 20. When such an expectation holds, the observation direction may be parallel to the normal direction to the hologram 20 and the illumination direction may be inclined by 45 ° with respect to the normal direction to the hologram 20. FIG. 5 shows the hologram 20 in a cross section parallel to the normal direction to the surface of the hologram 20 and the illumination direction of the illumination light to the hologram 20.

  By the way, in many cases, a reflective layer made of an aluminum vapor deposition layer or the like is formed on the back surface (surface opposite to the observer side) of the medium 22 on which interference fringe data is recorded. As described above and as shown in FIG. 5, also in the present embodiment, the reflective layer 24 is formed on the back surface of the medium 22. In such a case, the illumination direction of the illumination light for reproducing the image recorded on the hologram 20 is actually centered on the film-like recording medium 22 with respect to the traveling direction of the white light La from the luminaire 12. As a symmetric direction. That is, in the situation shown in FIG. 5, the illumination light for the hologram 20 actually corresponds to the light Lc illuminated from the hologram 20 from the side opposite to the observer. In the following description, it is assumed that a specular reflection layer (omitted in the attached drawings) is provided during actual use.

Note that a computer-generated hologram has a very weak angle selectivity compared to a volume hologram or the like. That is, in step S2, the illumination direction and the observation direction (diffraction direction) are specified, but in order to reproduce the image 30 recorded on the hologram 20, the computer-generated hologram is not necessarily generated by the illumination light from the defined illumination direction. It does not need to be illuminated and the computer-generated hologram need not be observed by the observer from a defined viewing direction. By satisfying the following relational expression (1), the reproduced image 30 can be observed.
N = | sin (θ2) −sin (θ1) | / λ (1)

  The angle θ1 in the equation (1) is an angle formed by the illumination direction with the illumination light with respect to the normal direction to the surface of the hologram, and the angle θ2 in the equation (1) is an image reproduction direction (observation). (Direction) is an angle formed with respect to the normal direction to the surface of the hologram. As shown in FIG. 8, the values of these angles θ1 and θ2 are on the surface of the hologram in a plane parallel to the normal direction to the hologram surface and the illumination direction by the illumination light (corresponding to the surface shown in FIG. 8). Defined by an angle that travels counterclockwise from the normal direction to the illumination direction. Therefore, in the example shown in FIG. 8, the angle θ2 is 360 ° (0 °), and the image can be observed from the normal direction of the hologram. Further, N in the expression (1) is a positive constant determined with respect to the defined spatial arrangement.

  That is, as shown in FIG. 8, not only the light Lc illuminating the hologram 20 from the illumination direction defined in this step S2, but also the lights Lc1 and Lc2 illuminating the hologram 20 from a direction different from the defined illumination direction. Also, the image 30 recorded on the hologram 20 is reproduced. However, in this case, the traveling directions of the reproduction lights Lb1 and Lb2 by these lights Lc1 and Lc2 are different from the traveling direction (that is, the observation direction) of the reproduction light Lb defined in this step S2. That is, the image 30 reproduced by the hologram 20 is observed from a direction different from the defined observation direction.

  Further, λ in the formula (1) is the wavelength of the illumination light. Therefore, when the illumination direction of the illumination light is kept the same, if the wavelength of the illumination light changes, the direction in which the illumination light is diffracted, in other words, the traveling direction of the reproduction light changes. That is, even if the illumination direction of the illumination light is the same, the direction in which the image is observed changes if the wavelength of the illumination light is different. As will be described later, the hologram 20 according to the present embodiment is configured so as to exhibit excellent operational effects by utilizing such characteristics of the computer-generated hologram.

  Next, as shown in FIG. 6, the calculation point on the recording surface of the medium 22 is specified (step S3). The calculation point is defined in consideration of the resolution required for the hologram 20 to be produced. Next, the intensity of the interference wave between the object light and the reference light is calculated for each calculation point, and interference fringe data is calculated (step S4). As for the object light, first, the surface of the image 30 to be recorded is handled as a set of many point light sources. Then, the light traveling from each point light source to the calculation point to be calculated is handled as object light considered in the calculation of the interference wave intensity at the calculation point.

  When calculating the interference wave intensity for each calculation point, it is not necessary to consider that object light is emitted from all point light sources to the calculation point to be calculated. In the present embodiment, as shown in FIG. 9, the original images 41, 42, 43 to be recorded and the recording medium 22 are each divided into a plurality of M unit areas. Here, the M unit areas Ab1 to Abm defined on the original images 41, 42, and 43 and the M unit areas Aa1 to Aam defined on the recording medium 22 are in a one-to-one relationship. It is made to correspond. Each unit region Ab1 to Abm of the original images 41, 42, and 43 includes a large number of point light sources that are assumed to emit object light. Each unit area Aa1 to Aam of the recording medium 22 includes a large number of calculation points. When calculating the intensity of the interference wave for one calculation point, the unit areas Ab1 to Ab1 on the original images 41, 42, and 43 corresponding to the unit areas Aa1 to Aam on the recording medium 22 to which the calculation point belongs. The calculation is performed in consideration of only the light source in Abm.

  FIG. 9 shows a recording medium 22 that forms the hologram 20 in the same cross section as FIG. 5 described above. That is, FIG. 9 shows the recording medium 22 (hologram 20) in a plane parallel to the normal direction to the surface of the recording medium 22 and the illumination direction of the defined illumination light. In the present embodiment, the recording medium 22 (hologram 20) is divided into M pieces from one side to the other side in the cross section shown in FIG. 9, and M unit areas Aa1 to Aam are formed. Has been.

  Therefore, as shown in FIG. 11, each of the unit areas Aa1 to Aam of the recording medium 22 is formed in an elongated shape, and the M unit areas Aa1 to Aam are arranged in parallel. The longitudinal directions of the unit areas Aa1 to Aam of the recording medium 22 are orthogonal to the illumination direction of the illumination light defined in the above step S2. The width (corresponding to the arrangement pitch) of the unit areas Aa1 to Aam of the recording medium 22 is set to such an extent that it cannot be visually recognized by human eyes (for example, 300 μm or less), and the interference fringes can function as a hologram. (For example, 5 μm or more). In the present embodiment, the M unit areas Aa1 to Aam defined on the recording medium 22 have the same width.

  Similarly, the original images 41, 42, and 43 to be recorded are also divided into M pieces from one side to the other side in the cross section shown in FIG. 9 to form unit areas Ab1 to Abm. . That is, the direction in which the unit areas Ab1 to Abm of the original images 41, 42, and 43 to be recorded are arranged is parallel to the direction in which the unit areas Aa1 to Aamg of the recording medium 22 are arranged. One unit area Aa1 to Aam of the recording medium 22 (hologram 20) is one unit of each of the original images 41, 42, and 43 arranged at positions facing each other along the normal direction of the recording medium 22. The areas Ab1 to Abm are associated with each other.

  FIG. 10 shows a cross section taken along line XX of FIG. In each of the unit areas Aa1 to Aam of the recording medium 22 (hologram 20), a large number of calculation points Pa1 to Pak arranged in the longitudinal direction are defined. As described above, the number of calculation points Pa1 to Pak can be determined according to the quality required for the hologram to be produced. For example, a plurality of columns of calculation points Pa1 to Pak arranged in the longitudinal direction may be defined in each unit region Aa1 to Aam.

  Although not all are shown in FIG. 10, as described above, the surfaces of the original images 41, 42, and 43 to be recorded are configured as a set of point light sources. When the interference wave intensity is calculated for one calculation point Pai included in one unit area Aan of the recording medium 22 (hologram 20), the original images 41, 42, 43 corresponding to the one unit area Aan are calculated. Of the point light sources Pb belonging to the unit region Abn, only the point light source Pb that can enter the calculation point Pai to be calculated is considered. As a result, the hidden surface process is performed on the image 30 reproduced by the hologram 20 so that the image 30 can be expressed in three dimensions.

  Note that it is preferable that the longitudinal direction of each of the unit areas Aa1 to Aamg of the recording medium 22 (direction orthogonal to the arrangement direction of the unit areas: see FIGS. 9 and 11) be parallel to the horizontal direction when the hologram 20 is used. . In this case, the hologram 20 has a large parallax in the horizontal direction. That is, it is possible to reproduce the image 30 expressed more three-dimensionally for a human having two eyes that are separated in the horizontal direction in a normal state.

  Interference fringe data is calculated as described above. However, as described above, when the hologram 20 is mass-produced, a master plate is often first prepared. Then, the master plate is used as an embossing original plate, and the hologram 20 having a concavo-convex shape whose undulation is reversed from that of the master plate is mass-produced. On the other hand, the interference fringe data calculated by the method described so far is the interference fringe data to be recorded on the medium 22 that constitutes the hologram 20. Therefore, when the master plate is first formed, it is necessary to appropriately perform conversion processing on the interference fringe data calculated by the method described above. Or you may make it calculate the interference fringe data which should be recorded on the medium which makes the master version by the method mentioned above.

  Incidentally, as described above, in the present embodiment, the color image 30 is reproduced by the hologram 20. On the other hand, when calculating interference fringe data, the wavelengths of the light that forms the object light and the reference light must be specified. Therefore, in the present embodiment, the interference fringe data related to the original image 41 that displays the first color component image 31 shown in FIG. 2 in green, and the second color component image 32 shown in FIG. 3 in red. Interference fringe data relating to the original image 42 to be displayed and interference fringe data relating to the original image 43 displaying the third color component image 33 shown in FIG. 4 in blue are recorded on the medium 22.

  At this time, as shown in FIG. 11, each of the unit areas Aa1 to Aam of the medium 22 is divided into three along the arrangement direction of the unit areas, and the first divided areas Aa1r to Aamr, the second divided areas Aa1g to Aam1g, and the second It is composed of three divided areas Aa1b to Aam1b. Each divided region is elongated in the longitudinal direction of the unit regions Aa1 to Aam, and the above-described calculation points Pa are defined side by side along the longitudinal direction. As described above, the number of calculation points Pa1 to Pak included in each divided region can be determined according to the quality required for the hologram 20 to be produced. Then, a plurality of rows of calculation points arranged in the longitudinal direction may be defined in each divided region.

  Then, according to the above-described method, the intensity of the interference wave of the object light and the reference light is calculated for the calculation point Pa belonging to the second divided areas Aa1g to Aam1g, thereby making the first color component image 31 green. Interference fringe data relating to the original image 41 to be displayed is calculated. When performing this calculation, the wavelengths of the object light and the reference light are set to the wavelengths in the wavelength band of the green light described above.

  Further, by calculating the intensity of the interference wave of the object beam and the reference beam at the calculation point Pa belonging to the first divided areas Aa1r to Aam1r according to the above-described method, the second color component image 32 is displayed in red. Interference fringe data relating to the original image 42 to be displayed is calculated. When performing this calculation, the wavelengths of the object light and the reference light are set to the wavelengths in the wavelength band of the red light described above.

  Further, according to the above-described method, the intensity of the interference wave of the object light and the reference light is calculated for the calculation point Pa belonging to the third divided areas Aa1b to Aam1b, thereby making the third color component image 33 blue. Interference fringe data relating to the original image 43 to be displayed is calculated. At this time, the wavelengths of the object light and the reference light are set to wavelengths in the above-described blue light wavelength band.

  When calculating the intensity of the interference wave for one calculation point belonging to a certain divided area in the calculation relating to the above three original images 41, 42, 43, the unit area of the recording medium 22 to which the divided area belongs. The calculation is performed considering only the point light sources Pb in the unit areas Ab1 to Abm on the image 30 corresponding to Aa1 to Aam.

  Further, in the calculation of the interference fringe data regarding the above three original images 41, 42, 43, the spatial arrangements specified in the above-described interference fringe data calculation method are set to be the same. As a result, as described later, when white light is irradiated onto the hologram 20 from a certain illumination direction, the first color component image 31 displayed in green and the second color component displayed in red are displayed. The image 32 and the image 33 of the third color component displayed in blue are reproduced in one direction specified corresponding to the illumination direction. Then, in the one direction specified corresponding to the illumination direction, a color image 30 formed by combining three reproduced images can be observed.

  The hologram 20 produced by the method as described above is recorded with a plurality of interference fringe data. The plurality of interference fringe data are for different original images 41, 42, 43. That is, the interference fringe data for reproducing a color image includes interference fringe data relating to a plurality of original images 41, 42, 43. The plurality of interference fringe data are formed in different areas on the surface of the recording medium 22 of the hologram 20.

  Next, the operation of the hologram 20 as described above will be described.

  As shown in FIG. 12, the hologram 20 is illuminated with light from the illumination direction defined when calculating the interference fringe data of the hologram 20. For the illumination of the hologram 20, normally, white light emitted from sunlight or the indoor lighting device 12 can be used. The white light Lw is reflected by the reflective layer 24 and functions as illumination light for the hologram 20. Then, as shown in FIG. 12, the white light Lw is diffracted in a predetermined direction in the medium 22 of the hologram 20. The predetermined direction diffracted at this time is the observation direction (the traveling direction of the reproduction light) defined when the interference fringe data of the hologram 20 is calculated. The diffracted white light Lw functions as reproduction light Lbr, Lbg, Lbb and reproduces the image 30 recorded on the hologram 20. That is, the observer can observe an image reproduced from a predefined observation direction.

  In the hologram 20 described above, as shown in FIG. 11, the surface of the medium 22 is divided into a number of areas that belong to one of three groups. Interference fringe data relating to the image 31 of the first color component displayed in green is recorded in the second divided areas Aa1g to Aamg, which is one of the three groups. Therefore, the reproduction light diffracted in the second divided areas Aa1g to Aamg of the medium 22 that is incident on the hologram 20 from the predefined illumination direction and forms the hologram 20 produces the first color component image 31 shown in FIG. Display in green.

  Further, interference fringe data relating to the second color component image 32 displayed in red is recorded in the first divided areas Aa1r to Aamr. Then, the reproduction light incident on the hologram 20 from the predefined illumination direction and diffracted by the first divided regions Aa1r to Aamr of the medium 22 displays the second color component image 32 shown in FIG. 3 in red. .

  Similarly, interference fringe data relating to the image 33 of the third color component displayed in blue is recorded in the third divided areas Aa1b to Aamb. Then, the reproduction light incident on the hologram 20 from the predefined illumination direction and diffracted by the third divided regions Aa1b to Aamb of the medium 22 displays the third color component image 33 shown in FIG. 4 in blue. .

  As shown in FIG. 11, each unit area of the medium 22 and further each divided area of the medium 22 are designed to be elongated, and the width thereof is so narrow that it cannot be recognized by human eyes. For this reason, the observer 10 who observes the hologram 20 from the observation direction is provided with the first color component image 31, the second color component image 32, and the third color component image 33 independently. It becomes impossible to recognize. As a result, the color image 30 of FIG. 1 is observed as an additive color mixture of the images 31, 32, and 33 of these different color components.

  As shown in FIG. 2, the first color component image 31 includes a hidden image 31 a that displays specific information, in this embodiment, authenticity determination information of the hologram 20 itself. Specifically, the first color component image 31 includes a hidden character “real”. Then, when the reproduction light Lb from the hologram 20 is observed through the member 18 that selectively transmits only the light (that is, green light) forming the first color component image 31 constituting the color image 30 ( 13) or reproduced light obtained by diffracting the illumination light Lc that has passed through the member 18 that selectively transmits the light forming the first color component image constituting the color image 30 by the hologram 20. When observing Lb, the observer 10 can observe only the image 31 of the first color component alone. Here, the member 18 that selectively transmits the light forming the first color component image constituting the color image 30 is similar to the color of the light forming the first color component image forming the color image 30. Cellophane having a color or the like can be used. Such cellophane is inexpensive and easily available.

  That is, the first image including the hidden image 31a is very easily operated by interposing a member 18 that selectively transmits only light forming the first color component image constituting the color image 30 in the optical path. The color component image 31 can be observed, and the authentication information included in the hidden image 31 can be read. As described above, it is possible to very easily and accurately determine that the hologram 20 is genuine and that the article 15 to which the hologram 20 is attached, such as a card, is genuine.

  On the other hand, as described above, in normal observation, it is impossible for the human eye to decompose and visually recognize only the first color component image 31. The second color component image 32 and the third color component image 33 superimposed on the first color component image 31 include noise images 32a and 33a, respectively. When the second color component image 32 or the third color component image 33 is superimposed on the first color component image 31, the noise images 32 a and 33 a are the first color component image 31. It is configured to make it difficult to read the authentication information displayed by the hidden image 31a. That is, the hidden image 31a of the first color component 31 is generated by the noise image 32a of the image 32 of the second color component, the noise image 33a of the image 33 of the third color component, or the second color. Both the noise image 32a of the component image 32 and the noise image 33a of the third color component image 33 are difficult to read during normal observation.

  That is, the hologram 20 includes a hidden image 31a that is not observed in a normal observation mode. As described above, since the hidden image 31a has high confidentiality (secret property), it is difficult to forge the hologram 20.

  In particular, in the present embodiment, the image 30 reproduced by the hologram 20 is configured as an image having a certain meaning (significant image). Specifically, the image 30 includes a sphere 36 and two rings 38 extending around the sphere 36. The ring 38 is configured by arranging character strings “GENUINE”. Therefore, a person who has the hologram 20 will recognize that the hologram 20 is a display body for displaying the authenticity simply by the character string “GENUINE”. In addition, for the sphere 36, a combination with the character string “GENUINE” expresses the reproduced image more three-dimensionally, and further, a geometrical shape for improving the design of the reproduced image. You will recognize it as a shape.

  Thus, when the image 30 reproduced by the hologram 20 is an image having some meaning, it is difficult to conceive that the hidden image 31a is further included in the reproduced image 30 itself. . Therefore, it is extremely difficult to come up with a method for making the color image 31a latent, such as the hidden image 31a being formed by the separated image 31 of one color component constituting the color image 30. . Since the hidden image 31a having high confidentiality is recorded on the hologram 20, the hologram 20 is very difficult to forge. Therefore, according to the hologram 20, it is possible to accurately determine the authenticity.

  In addition, the hologram 20 according to the present embodiment includes an original image displayed in three primary colors, that is, an original image 41 displayed in green, an original image 42 displayed in red, and an original image 43 displayed in blue. Interference fringe data is recorded. The full-color image 30 is reproduced by the additive color mixture of the original images 41, 42, and 43 displayed in the three primary colors. That is, the hologram 20 can accurately reproduce a full color image displayed in a desired color. Furthermore, according to the hologram 20 according to the present embodiment, a remarkable parallax in the horizontal direction can be ensured. That is, when the observer changes the observation direction along the horizontal direction, the image 30 reproduced by the hologram 20 changes greatly according to the change in the observation direction. Thereby, a desired three-dimensional shape can be accurately reproduced by the hologram 20. Thus, according to the hologram 20 which can reproduce a desired image very accurately, it is possible to ensure excellent design. In the first place, such an elaborate hologram 20 can also enjoy the advantage that it is difficult to forge.

  In the above description, the operation of the hologram 20 has been described on the premise that the hologram 20 is illuminated with white light from a predetermined illumination direction and the hologram 20 is observed from a predetermined observation direction. However, as described with reference to FIG. 8, even when the hologram 20 is illuminated with white light from a direction different from the predetermined illumination direction defined at the time of calculating the interference fringe data, it is reproduced by the hologram 20. The image 30 can be observed. Further, even when the hologram 20 is observed from a direction different from the predetermined observation direction defined when calculating the interference fringe data, the image 30 reproduced by the hologram 20 can be observed. Specifically, the illumination light that illuminates the hologram 20 is diffracted in a predetermined direction specified in relation to the illumination direction of the illumination light so as to satisfy the above-described formula (1).

  In this way, the color image 30 is not observed as a superposition of the first to third color component images 31, 32, 33 only under a single condition, but the orientation of the hologram 20 (as a result, illumination By appropriately changing the illumination direction) and the observation direction, the color image 30 is observed as a superposition of the first to third color component images 31, 32, 33. . Further, the light forming the first color component image 31 constituting the color image 30 under the condition that the color image 30 is observed as an overlay of the first to third color component images 31, 32, 33. By using the member 18 that selectively transmits only green light (that is, green light), it is possible to read the authentication information from the hidden image 31a included in the first color component image 31. That is, the hologram 20 according to the present embodiment has weak angle selectivity, and the authenticity of the hologram 20 and the authenticity of the article 15 to which the hologram 20 is attached can be accurately and easily determined under various conditions as described above. Judgment can be made.

  By the way, satisfying the above-described expression (1) means that interference fringe data corresponding to the first color component image 31 (strictly speaking, the first original image corresponding to the first color component image 31). The color image 30 is formed in the second divided areas Aa1g to Aamg in the medium 22 in which the interference fringe data relating to 41 and the interference fringe data calculated in consideration of the green object light and the reference light) are recorded. The light having a wavelength λ different from the light forming the first color component image 31 (green light in the present embodiment), for example, the second and third color components constituting the color image 30 This means that the light forming the images 32 and 33 (in this embodiment, red light and blue light) can also be diffracted. And if the light which forms the image 32 of the 2nd color component which comprises the color image 30 is diffracted in 2nd division area Aa1g-Aamg, the said diffracted light will contain the hidden image 31a which displays authenticity determination information The reproduced image, that is, the first color component image 31 is reproduced with the light color (red in the present embodiment) forming the second color component image 32 constituting the color image 30. . Similarly, when the light forming the image 33 of the third color component constituting the color image 30 is diffracted in the second divided areas Aa1g to Aamg, the diffracted light is converted into the hidden image 31a displaying the authentication information. The included image, that is, the first color component image 31 is reproduced with the light color (blue in the present embodiment) forming the third color component image 33 constituting the color image 30. Become.

  However, in this case, the condition is that the above-described expression (1) is satisfied. Therefore, when the directions in which the light of each wavelength band illuminates the hologram 20 are the same, for example, white light from a luminaire or the sun is used as the illumination light, and light of various wavelength bands is in the same direction. When illuminating the hologram 20, the images recorded in the second divided areas Aa1g to Aamg are reproduced in different directions with different colors.

  Note that when white light is used as illumination light, a phenomenon in which the same image is reproduced in different directions by light of different colors is a phenomenon called so-called chromatic dispersion, and the second divided regions Aa1g to Aamg. The light is not limited to the light incident on the first divided regions Aa1r to Aamr and the light incident on the third divided regions Aa1b to Aamb.

  According to the hologram 20 according to the present embodiment, as described below, it is possible to obtain high confidentiality of the hidden image 31a without being affected by chromatic dispersion.

  In the following, as an example, a situation in which light or sunlight from an indoor lighting device enters the hologram 20 is considered. Under this situation, the hologram 20 is irradiated with white light including light of various colors (various light having different wavelengths) with respect to the hologram 20 at a fixed illumination angle.

  14 to 18 show directions in which red light, green light, and blue light incident on the hologram 20 according to the present embodiment described above at the same incident angle are diffracted, respectively. Has been. In FIG. 14, the diffraction direction of the light incident on the first divided area Aar in the unit area Aa of the recording medium 22 of the hologram 20 is shown. Similarly, FIG. 15 shows the diffraction direction of light incident on the second divided region Aag, and FIG. 16 shows the diffraction direction of light incident on the third divided region Aab. On the other hand, FIG. 17 and FIG. 18 show the diffraction directions of the light incident on the three divided regions Aar, Aag, and Aab that form the unit region Aa.

  14 to 18 show the hologram 20 in a cross section parallel to both the normal direction to the surface of the hologram 20 and the illumination direction of the illumination light. 14 to 18, red light is indicated by a short dotted line, green light is indicated by a solid line, and blue light is indicated by a long dotted line. 14 to 18, the diffracted light for reproducing the first color component image 31 is indicated by a straight line, the diffracted light for reproducing the second color component image 32 is indicated by a wavy line, and the third color component is shown. The diffracted light for reproducing the image 33 is indicated by a broken line.

  As described above, in the hologram 20 according to the present embodiment, the second divided region Aag has the interference wave intensity between the green reference light and the green object light traveling in the normal direction of the hologram 20. The interference fringe data obtained by the calculation and for reproducing the image 31 of the second color component shown in FIG. 2 is recorded. Similarly, the first divided area Aar includes interference fringe data obtained by calculating the intensity of the interference wave of the red reference light and the red object light traveling in the normal direction of the hologram 20. Thus, interference fringe data for reproducing the image 32 of the second color component shown in FIG. 3 is recorded. Further, the third divided area Aab is interference fringe data obtained by calculating the intensity of the interference wave of the blue reference light and the blue object light traveling in the normal direction of the hologram 20. Interference fringe data for reproducing the image 33 of the third color component shown in FIG. 4 is recorded.

  Therefore, when the incident angle of the illumination light coincides with the incident angle of the reference light, as shown in FIG. 15, among the white light incident on the second divided region Aag of the hologram 20, the diffracted light of the green component (reproduced light) Lbgg reproduces the green component image 31 shown in FIG. 2 in the normal direction of the hologram 20. Under the same conditions, as shown in FIG. 14, among the white light incident on the first divided area Aar of the hologram 20, the diffracted light (reproduced light) Lbrr of the red component is in the normal direction of the hologram 20. The red component image 32 shown in FIG. 3 is reproduced. Furthermore, of the white light incident on the third divided area Aab of the hologram 20 under the same conditions, the diffracted light (reproduced light) Lbbb of the blue component is the normal direction of the hologram 20 as shown in FIG. Then, the blue component image 33 shown in FIG. 4 is reproduced.

  As a result, as shown in FIG. 17, the first color component image 31 of FIG. 2 displayed in green, the second color component image 32 of FIG. 3 displayed in red, and the blue display The image 33 of the third color component shown in FIG. 4 is reproduced in the normal direction of the hologram 20. Accordingly, from the front direction of hologram 20 (observation direction d1 in FIG. 17), color images 30 shown in FIG. 1 are represented by decomposition images 31, 32, and 33 in FIGS. As a superposition, it can be observed.

  On the other hand, as shown in FIG. 15, among the white light incident on the second divided region Aag of the hologram 20, the diffracted light (reproduced light) Lbgr of the red component is higher than the normal direction of the hologram 20. Proceed in an inclined direction. Then, the red diffracted light Lbgr reproduces the image 31 of FIG. 2 represented by the red component in the traveling direction. Similarly, as shown in FIG. 16, of the white light incident on the second divided area Aa1 of the hologram 20, the diffracted light (reproduced light) Lbgb of the blue component is inclined downward from the normal direction of the hologram 20. Proceed in the direction you did. Then, the blue diffracted light Lbgb reproduces the image 31 of FIG. 2 represented by the blue component in the traveling direction. That is, the image 31 in FIG. 2 including the hidden image 31a is a range r1 that is inclined up and down at a certain angle with respect to the direction expressed by the green component (the normal direction of the hologram 20) (see FIG. 17). Will be played.

  Such chromatic dispersion occurs when light of each wavelength is diffracted so as to satisfy the above formula (1). The wavelength of the green component light is shorter than the wavelength of the red component light and longer than the wavelength of the blue component light. As a result, the traveling direction of the diffracted light of the green component is the traveling direction of the diffracted light of the red component having the longest wavelength of visible light and the traveling direction of the diffracted light of the blue component having the shortest wavelength of visible light. And come to be located between. Then, the same image 31 is reproduced in a color other than green in a range r1 inclined at a certain inclination angle up and down with respect to the reproduction direction in which the image is reproduced in green.

  A similar phenomenon is diffracted by the diffracted lights Lbrr, Lbrg, and Lbrb (see FIGS. 14 and 17) diffracted by the first divided region Aar of the hologram 20 and the third divided regions Aa1b to Aamb of the hologram 20. It also occurs in the diffracted beams Lbbr, Lbbg, Lbbb (see FIGS. 16 and 17).

  Specifically, as shown in FIG. 14, among the white light incident on the first divided area Aar of the hologram 20, the diffracted light (reproduced light) Lbrg of the green component is lower than the normal direction of the hologram 20. Proceed in the direction of the slope. Of the white light incident on the first divided area Aar of the hologram 20, the diffracted light (reproduced light) Lbrb of the blue component is tilted further downward than the traveling direction of the diffracted light (reproduced light) Lbrg of the green component. Then proceed. That is, the image 32 in FIG. 3 is reproduced in various colors in a range r2 (see FIG. 17) from the normal direction of the hologram 20 to a direction inclined downward at a large angle with respect to the normal direction. It becomes like this.

  Similarly, as shown in FIG. 16, among the white light incident on the third divided area Aab of the hologram 20, the diffracted light (reproduced light) Lbbg of the green component is inclined upward from the normal direction of the hologram 20. Then go in the direction. Of the white light incident on the third divided area Aab of the hologram 20, the diffracted light (reproduced light) Lbbb of the blue component is inclined further upward than the traveling direction of the diffracted light (reproduced light) Lbbg of the green component. Then proceed. That is, the image 33 in FIG. 4 is reproduced in various colors in a range r3 (see FIG. 3) from the normal direction of the hologram 20 to a direction inclined upward at a large angle with respect to the normal direction. It becomes like this.

  In the present embodiment, interference fringe data relating to three original images 41, 42, and 43 corresponding to the first to third color component images 31, 32, and 33 are recorded. When calculating these interference fringe data, the spatial arrangement was defined to be the same, and the colors of the original images were set to different colors. As a result, the first to third color component images 31, 32, and 33 are reproduced with different colors at the same position according to the interference fringe data, whereby the color image 30 shown in FIG. 1 is observed. It is like that.

  The interference fringe data for reproducing the first color component image 31 including the hidden image 31a is calculated by calculating the intensity of the interference wave of the green object light and the green reference light. On the other hand, the interference fringe data for reproducing the image 32 of the second color component including the noise image 32a is calculated by calculating the intensity of the interference wave of the red object light and the red reference light. The interference fringe data for reproducing the third color component image 33 is calculated by calculating the intensity of the interference wave of the blue object light and the blue reference light. That is, the peak wavelength of the wavelength band of the light used for calculating the interference fringe data related to the first color component image 31 is used to calculate the interference fringe data related to the second color component image 32. It is shorter than the peak wavelength in the wavelength band of the light and longer than the peak wavelength in the wavelength band of the light used for calculating the interference fringe data related to the third color component image 33.

  As a result, as shown in FIG. 17, in the range r1 in which the first color component image 31 is reproduced using white light, the second color component image 32 uses white light. At least one of the range r2 in the direction to be reproduced and the range r3 in the direction in which the third color component image 33 is reproduced using white light overlaps. That is, there is no observation direction in which the first color component image 31 including the hidden image 31a is observed alone. The first color component image 31 including the hidden image 31a is always at least one of the second color component image 32 including the noise image 32a and the third color component image 33 including the noise image 33a. It will be observed in a state of being superimposed.

  Specifically, when observed from the normal direction of the hologram 20, as described above, an image obtained by superimposing the three color component images 31, 32, and 33, that is, the full-color image 30 shown in FIG. Observed.

  As an example, when the hologram 20 is observed from a direction in which the hologram 20 is looked down obliquely (observation direction d2 in FIG. 17), the first color component image 31 displayed in red and a green image are displayed. An image obtained by superimposing the third color component image 33 is observed. At this time, the hidden image 31a of the first color component image 31 displayed in red is superimposed on the noise image 33a of the third color component image 33 displayed in green and displayed by the hidden image 31a. Authentication information (letters “real”) cannot be read.

  Similarly, when the hologram 20 is observed from the direction in which the hologram 20 is viewed obliquely upward (observation direction d3 in FIG. 17), the first color component image 31 displayed in blue and the first image displayed in green. An image obtained by superimposing the image 32 of the two color components is observed. At this time, the hidden image 31a of the first color component image 31 displayed in blue is superimposed on the noise image 32a of the second color component image 32 displayed in green and displayed by the hidden image 31a. Authentication information (letters “real”) cannot be read.

  On the other hand, as shown in FIG. 17, the image 32 of the second color component displayed in blue can be observed independently from the direction inclined downward (observation direction d5 in FIG. 17). Further, the image 33 of the third color component displayed in red can also be observed independently from the direction inclined upward (observation direction d4 in FIG. 17).

  In the present embodiment, the noise images 32a and 33a of the second and third color component images 32 and 33, which can be observed alone, are common between the first and third color component images 32 and 33. This is a random gradation pattern (random shading pattern) on the image (the sphere 36 in the present embodiment). Therefore, according to the present embodiment, in all the ranges r1, r2, and r3 where the reproduced images 30, 31, 32, and 33 of the hologram 20 can be observed, the common stereoscopic images 36 and 38 and the surface of the image 36 are displayed. And a random pattern formed on the surface. That is, when observing with normal attention, even if the illumination direction or the observation direction of the illumination light is changed, it can be recognized only that the color of the reproduced image is changed. And since such a change in hue is a typical phenomenon seen in a rainbow hologram, it can be said that the concealment of the hidden image 31a is extremely high.

  As shown in FIG. 18, when the reproduction light or illumination light is transmitted through the member 18 that selectively transmits only the green component light, the direction in which the hologram 20 is looked down obliquely downward (FIGS. 17 and From the observation direction d2) at 18, only the third color component image 33 is observed. Further, when the reproduction light or the illumination light is transmitted through the member 18 that selectively transmits only the green component light, from the direction in which the hologram 20 is looked up obliquely upward (observation direction d3 in FIGS. 17 and 18). Only the image 32 of the second color component is observed.

  Furthermore, as already described, by using the member 18 that selectively transmits only the light (green light in the present embodiment) that forms the image 31 of the first color component constituting the color image 30, When the image 31 of the first color component including the hidden image 31a is made visible, the hidden image 31a can be observed from one direction specified according to the illumination direction of the illumination light. On the other hand, for example, by using a member that can selectively transmit only the light (in this embodiment, red light) forming the image 32 of the second color component constituting the color image 30. The image 31 of the first color component can be made visible. As can be understood from FIG. 17, the image 31 of the first color component displayed in red is observed from the direction in which the hologram 20 is looked down obliquely (observation direction d2 in FIG. 17). The authenticity determination information of the image 31a can be read. Similarly, the first color component can also be obtained by using a member that selectively transmits only the light (blue light in the present embodiment) forming the image 33 of the third color component constituting the color image 30. The image 31 can be revealed. The image 31 of the first color component displayed in blue is observed from a direction in which the hologram 20 is looked up obliquely upward (observation direction d3 in FIG. 17), whereby the authenticity determination information of the hidden image 31a can be read. . That is, by using a member (bandpass filter) that selectively transmits only light of a specific color component, the hidden image 31a can be observed only from a limited direction.

  According to the hologram 20 of the embodiment as described above, by receiving the illumination light, the color image 30 is reproduced in a specific direction corresponding to the illumination direction of the illumination light. And the color image 30 reproduced | regenerated in a specific direction with illumination light contains the image 31,32,33 displayed with a mutually different color component. Among them, the image 31 of one color component includes a hidden image 31a that displays specific information, and the images 32 and 33 of other color components are regions in which the hidden image 33 is reproduced (in this embodiment, The noise images 32a and 33a to be reproduced are included in an area including the surface area of the sphere 36). When observing the color image 30 reproduced using the noise images 32a and 33a using normal illumination light, that is, white light such as light from indoor lighting equipment or sunlight, a hidden image of a specific color component Specific information included in 31a (in the present embodiment, authenticity determination information) cannot be read. On the other hand, when the hologram is observed through a filter 18 that selectively transmits only light of the color component forming the hidden image 31a, for example, a color cellophane that is inexpensive and easily available, the color for displaying the hidden image 31a. Color components other than the components are absorbed by the filter 18, and only the color component image that displays the hidden image 31a is observed. That is, the information of the hidden image 31a can be clearly read by a simple method such as using the filter 18 that selectively transmits only the light of the color component forming the hidden image 31a. As described above, according to the hologram 20 according to the present embodiment, if the existence of the hidden image 31a is known in advance, the information of the hidden image 31a can be clearly read by an inexpensive and easy method, and the hidden image 31a. If the existence of the hidden image 31a is not known in advance, it becomes difficult to notice the existence of the hidden image 31a. Thereby, the possibility that the information of the hidden image 31a is unintentionally read can be extremely reduced.

  Therefore, such a hologram 20 can function extremely effectively as a display body that displays authenticity. In this application, the hidden image 31a displays information indicating the authenticity of the hologram 20 and the authenticity of the article 15 to which the hologram 20 is attached, that is, authenticity determination information, as specific information. . As described above, since the presence of the authenticity determination information is difficult to notice, the effect of preventing forgery of the hologram 20 as the authenticity display body is extremely high. On the other hand, the authenticity of the hologram 20 as an authentic display can be determined very easily and accurately.

  Further, according to the present embodiment, the reproduced image 30 of the hologram 20 is displayed in color using three types of color components. In particular, the reproduced image 30 of the hologram 20 can be expressed in full color by the three primary colors of red, green and blue. Thereby, the design which was excellent in the reproduced image of the hologram 20 can be provided.

  Furthermore, according to the present embodiment, the peak wavelength of the light that has the hidden image 31a and reproduces the image 31 of the first color component that constitutes the color image is that of the other two color components that constitute the color image. It is shorter than the peak wavelength of light for reproducing one of the images and longer than the peak wavelength of light for reproducing the other image of the other two color component images. Specifically, the first color component image 31 having the hidden image 31 a is displayed in green when forming the color image 30, and the other two color component images 32 and 33 are displayed in the color image 30. Are displayed in red and blue. In a computer-generated hologram in which interference fringe data is recorded as an uneven shape that diffracts illumination light in a specific direction, the diffraction direction changes depending on the wavelength. Specifically, the traveling direction of light having a long wavelength is greatly changed by diffraction. Therefore, in such a hologram 20, when white light becomes illumination light, so-called chromatic dispersion occurs, so that the diffraction direction of green light is located between the diffraction direction of red light and the diffraction direction of blue light. become. That is, the direction in which the green reproduction image is observed exists between the direction in which the blue reproduction image is observed and the direction in which the red reproduction image is observed. For this reason, the color image 30 as a superposition of the three images 31, 32, 33 is generated, for example, when the incident direction of the illumination light deviates from the planned direction or the direction in which the reproduction light is observed deviates from the predetermined direction. Even when the hologram 20 is observed from a direction other than the observed direction, the image 31 including the hidden image 31a is observed alone without being superimposed on the other color component images 32 and 33. There is no end. That is, it is possible to effectively prevent unexpected reading of specific information included in the hidden image 31a.

  Further, in the present embodiment, the color image 30 reproduced by the hologram 20 includes an image having a certain meaning (a meaningful image, in this embodiment, a sphere 36 and a ring 38 made up of character strings). In the color image 30, the region (the surface of the sphere 36) where the hidden image 31a and the noise images 32a and 33a are formed is colored with a random coloring pattern. According to the present embodiment as described above, it is difficult to notice that the hidden image 31a is contained by the meaningful image, so that the forgery prevention function is further improved. On the other hand, since the region where the hidden image 31a and the noise images 32a and 33a are formed is colored with a random coloring pattern, the design of the noise images 32a and 33a becomes extremely easy. As a result, the manufacturing cost of the hologram 20 can be reduced.

  As described above, the present invention has been described based on one embodiment shown in the drawings, but the present invention is not limited to the above embodiment, and the present invention can be implemented in various other modes. Is possible.

  For example, in the above-described embodiment, the first color component image 31 including the hidden image 31a is the same image as the second and third color component images 32 and 33 including the noise images 32a and 33a, respectively. (Specifically, an example including a sphere 36 and a ring 38 made of a character string) is shown, but the present invention is not limited to this. For example, similarly to the display body disclosed in Patent Document 2, when a hidden image is observed, the normal image is not visually recognized, that is, only one of the hidden image and the normal image is changed by changing the observation condition. May be observed.

  In the above-described embodiment, the example in which only the first color component image 31 has the hidden image 31a has been described, but the present invention is not limited thereto. For example, instead of the first color component image 31 having the hidden image 31a, or in addition to the first color component image 31 having the hidden image 31a, the second color component image 32 is provided. May have a hidden image. In this example, a noise image that makes it difficult to read a hidden image included in the first color component image 31 is included in the second and third color component images 32 and 33, and further, the second color A noise image that makes it difficult to read a hidden image included in the component image 32 may be included in the first and third color component images 31 and 33. Further, in this example, the hidden image included in the first color component image 31 and the hidden image included in the second color component image 32 are displayed so that one information can be read. You may do it. As an example, the hidden image included in the first color component image 31 displays only “book” of the character string “real”, and the hidden image included in the second color component image 32 is “real”. Only "things" in the character string "" may be displayed.

  Furthermore, in the above-described embodiment, the example in which the color image 30 including the hidden image 31a is configured by the images 31, 32, and 33 displayed in the three primary colors has been described, but the present invention is not limited thereto. A color image may be composed of a large number of images displayed by light of a large number of wavelength bands. Conversely, a color image may be composed of only two-color images.

  Furthermore, as described above, the hologram including the hidden image does not need to be formed as a computer-generated hologram, and can be manufactured as various types of holograms. If the hologram including the hidden image is a hologram that exhibits a color separation phenomenon such as a rainbow hologram, the reproduced color image includes three or more color component images as described above. It is preferable that a hidden image is included in an image other than the image displayed by the light having the shortest wavelength and the image displayed by the longest wavelength.

10 observer 12 lighting fixture 15 article 18 member (filter)
20 Hologram 22 Medium (Recording medium)
24 reflective layer 30 color image 31 first color component image 31a hidden image 32 second color component image 32a noise image 33 third color component image 33a noise image 36 sphere 38 ring 41 original image 42 original image 43 Original image 46 Sphere 48 Ring

Claims (10)

A hologram in which interference fringe data for reproducing a color image is recorded,
The color image includes a first color component image, a second color component image different from the first color component, and a first color component different from both the first color component and the second color component. At least three color component images ,
The image of the first color component includes a hidden image that displays information;
The image of the second color component look including the noise image making it difficult to read the hidden image in the color image including at least an image of an image and the second color component of said first color component,
The image of the third color component includes a noise image that makes it difficult to read the hidden image in the color image;
The peak wavelength of light that displays the image of the first color component that constitutes the color image is shorter than the peak wavelength of light that displays the image of the second color component that constitutes the color image, and the color A hologram characterized by being longer than a peak wavelength of light for displaying an image of the third color component constituting the image . A hologram in which interference fringe data for reproducing a color image is recorded,
The color image includes a first color component image, a second color component image different from the first color component, and a first color component different from both the first color component and the second color component. At least three color component images ,
The image of the first color component includes a hidden image that displays information;
The image of the second color component look including the noise image making it difficult to read the hidden image in the color image including at least an image of an image and the second color component of said first color component,
The image of the third color component includes a noise image that makes it difficult to read the hidden image in the color image;
The image of the first color component constituting the color image is displayed in green,
The image of the second color component constituting the color image is displayed in red,
The hologram according to claim 1, wherein the image of the third color component constituting the color image is displayed in blue .   The image of the first color component constituting the color image is displayed in green,
  The image of the second color component constituting the color image is displayed in red,
  The image of the third color component constituting the color image is displayed in blue.
The hologram according to claim 1.   The noise image included in the image of the second color component is included in the image of the first color component when the image of the first color component and the image of the second color component are superimposed. Configured to make it difficult to read the information of the hidden image
  The noise image included in the image of the third color component is included in the image of the first color component when the image of the first color component and the image of the third color component are superimposed. The information of the hidden image is configured to be difficult to read
The hologram according to any one of claims 2 to 3, wherein:   The noise image is formed as a random gradation pattern.
The hologram according to any one of claims 1 to 4, wherein:   The information of the hidden image can be read through a member that transmits only light in a specific wavelength band.
The hologram according to any one of claims 1 to 5, wherein:   The color image is a three-dimensional image.
The hologram according to any one of claims 1 to 6, wherein:   The information is authenticity determination information.
The hologram according to claim 1, wherein:   It is formed as a computer-generated hologram
The hologram according to any one of claims 1 to 8, wherein:   The hologram according to any one of claims 1 to 9 is attached.
Article characterized by that.