JP2003295744A - Optical information recording medium constituted of computer hologram - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an information recording medium which is adapted to a plurality of information reproducing conditions, by which information quantity is increased, information reading of high precision can be attained and forgery preventing effect is increased and further which has visual effect (decorative effect) under a usual observation condition, in an optical information recording medium having a computer hologram as a constitutional element. <P>SOLUTION: The optical information recording medium having an optical information recording section constituted by forming a plurality of regions composed of computer holograms on a base material surface, is characterized in that the computer hologram has each cell as a constitutional unit, specific information is independently recorded in each cell, and ≥2 kinds of the computer holograms having transportation waves different from each other are arranged in a small region. Difference between the transportation waves is larger than a frequency band width which reproduced information from the computer hologram has. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium capable of optically reproducing information, and more particularly to an optical information recording medium having a large amount of information, which corresponds to visual observation or machine reading of reproduced information.

[0002]

2. Description of the Related Art Conventionally, there is known an information recording medium which is recorded by using a holographic photographing method such as a Fourier transform hologram and which can read information spatially projected by a beam of light. However, most of such optical information recording media recorded one piece of information as a whole, and it was not possible to reproduce a plurality of pieces of information. Also, the incident angle of the reproducing beam to the optical information recording medium
The direction was limited to the conditions corresponding to that of the reference light during hologram recording.

On the other hand, there is also known an optical information recording medium having a similar effect by the method of computer generated hologram formed by calculating interference fringe data by a computer or the like. But,
In this regard as well, only the production of the optical information recording medium according to the above-mentioned photographing method has been performed.

In the above-mentioned conventional technique, since information can be simply reproduced, forgery and imitation can be facilitated, leaving a problem in security. Moreover, the amount of information per unit area could not be increased.

On the other hand, a display body for displaying an image or the like using a hologram or a diffraction grating is known, which is not used for information recording. These display bodies have the effect of improving the decorativeness and security of the attached products (for example, credit cards and gift certificates), and have been useful in preventing counterfeiting and imitation. However, even for holograms and diffraction gratings, further improvement in security is desired.

For this reason, there has been considered a method of complicating the manufacturing method of the display body to make counterfeiting or imitation difficult. As an example, by utilizing the two-beam interference of coherent light, a plurality of microscopic cells (dots) composed of a diffraction grating are arranged on the surface of a substrate, and a display composed of a diffraction grating pattern (hereinafter referred to as “display” or “display”). Body) may be mixed and used), and the applicant of the present invention has disclosed those disclosed in JP-A-60-156004 and JP-A-2-7231.
Methods represented by Japanese Patent Laid-Open No. 9-72406 and Japanese Patent Laid-Open No. 5-72406 are known.

In these methods, two laser beams are made to intersect each other on a photosensitive material, and the two laser beams are made to interfere with each other by exposing in a cell unit, so that diffraction is formed by minute interference fringes formed in each cell. The grid with its spatial frequency
Exposures are recorded one after another while changing the direction and light intensity as appropriate.
This is a method of producing a pattern composed of a collection of diffraction grating cells. When observing the created pattern, the spatial frequency is related to the visible color and the direction is related to the visible direction. Further, the light intensity at the time of exposure changes the depth of interference fringes and the like, and is related to the brightness at the time of observation.

FIG. 1 shows an example of a diffraction grating pattern having cells as constituent units in a conventional display. The display image (pattern) is composed of a collection of square cells. Each pixel cell is filled with a diffraction grating suitable for displaying a pattern.

The method for producing the diffraction grating pattern is not limited to the above method using the two-beam interference, and the diffraction grating is directly drawn on the surface of the substrate by an electron beam (electron beam = EB), A method of arranging the diffraction grating cells may be adopted. The method is known from Japanese Patent Application Laid-Open No. 2-72320 by the present applicant. In such a method, the grating line forming the diffraction grating is not limited to a straight line, and a curved line may be used, but in any case, the grating line is formed by arranging simple grating lines. A cell composed of such a simple diffraction grating can generate first-order diffracted light having a relatively simple property such as a beam shape or a divergent light shape when a beam-shaped illumination light enters.

Since the display body composed of the diffraction grating pattern manufactured by the above method is composed of a simple diffraction grating, it is possible to express an image with higher brightness and saturation than a conventional rainbow hologram or the like. The eye-catching effect was high, and the authenticity determination by visual observation was easier. However, since the display made up of such a diffraction grating pattern is the reference for true / false judgment only with the observation result with the naked eye, there is a risk of erroneous true / false judgment with respect to objects having a similar visual impression. there were. In addition, since only the visual check serves as a criterion for determination, it is not impossible to make a counterfeit object having a similar appearance by observing the details visually.

On the other hand, there has been proposed an invention in which the diffraction grating pattern having the cell structure as described above is used not for image display but for recording machine-readable information (for example, Japanese Patent Laid-Open No. 3-211096 by the present applicant). ). In such a conventional method of recording information for machine reading, an image or the like cannot be displayed in the machine reading information part, the information recording part can be clearly confirmed visually, and the amount of recorded information is small. , Counterfeiting / imitation is not impossible. Further, when such an information recorded area is arranged side by side with a display body or the like made of a diffraction grating pattern, there is a problem that the diffracted light from the information recording area makes it difficult to read other display information. It was a cause of degrading the display quality. Further, the conventional simple diffraction grating has a problem that the amount of information that can be recorded is small.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to adapt an optical information recording medium to a plurality of information reproduction conditions, increase the amount of information, enable highly accurate information reading, and enhance the counterfeit prevention effect. And Another object of the present invention is to realize an information recording medium that also has a visual effect (decorative effect) under normal observation conditions.

[0013]

The optical information recording medium according to the present invention has been made in order to achieve the above-mentioned object, and has an optical information recording portion having a computer hologram formed on the surface of a base material. In the medium, the computer generated holograms are cells each having a size of 300 μm square or less,
Specific information is independently recorded in each cell, and two or more types of computer hologram cells each having a different carrier wave are arranged in a small area. It is characterized in that it is larger than the frequency bandwidth of the reproduction information.

Further, the computer generated hologram is characterized in that it is a Fourier transformed hologram which is obtained by subjecting two-dimensional information to Fourier transform to obtain an object light component. Further, it is characterized by having both the visual effect of the diffraction grating cell and the information recording function of the computer generated hologram.

In the present invention, the term "diffraction grating cell" means that a diffraction grating composed of relatively simple grating lines covers the inside of the cell, and the computer generated hologram uses the original information as object light. It was obtained. As the object light of the computer generated hologram, for example, information may be a two-dimensional pattern, and the light intensity distribution on the cross section of the object light may correspond to this two-dimensional pattern.

When reading information from the optical information recording medium of the present invention, mainly the first-order diffracted light from the computer generated hologram becomes the information reproducing light. As the computer generated hologram of the present invention, a computer generated hologram including a kinoform in a broad sense can be applied. Reconstructed light (mainly first-order diffracted light) from the computer generated hologram is illuminated with illumination light under preset conditions (generally, light having a narrow wavelength band such as laser light, and the light that is beam-shaped or converges or diverges). By doing so, it is possible to project or form an image on a screen or the like arranged at a preset distance, and it is possible to easily and reliably perform information recognition with the naked eye or information reading with a light receiving element. (The light receiving element may be placed at the position of the screen). Furthermore, it is easy to make the reproduction light from the computer generated hologram into a two-dimensional distribution of light intensity at the screen position, and it is possible to reproduce a lot of information including images, character information, bar codes and the like at once. it can.

In such information reproduction, the computer generated hologram can be made very small, but it is generally difficult to use the information reproduction illumination light while keeping the information reproduction stability and accuracy small. From this fact, it was meaningless to make the computer hologram too small, and it was not possible to increase the amount of recorded information per unit area.

On the other hand, in the optical information recording medium of the present invention, two or more types of computer generated holograms, which are information recording units, are used to enable the amount of recorded information to be increased. Moreover, in the optical information recording medium of the present invention, since the carrier wave of each computer generated hologram is larger than the frequency bandwidth of the recorded information, even if two or more computer generated holograms are simultaneously illuminated, they are reproduced. The information does not overlap spatially and can be read independently, and it is possible to reproduce a large amount of information with high accuracy (low noise) and stably from an optical information recording medium having a small area. 1-2).

Further, since the type of computer generated hologram corresponds to the number of reproduction conditions, all the information cannot be reproduced unless these plural reproduction conditions are known, so that it also has a high forgery prevention effect. In particular, if a plurality of reproduced images obtained under a plurality of reproducing conditions are associated with each other to reproduce complete information, the forgery prevention effect can be further enhanced.

At this time, since it is not necessary to particularly narrow down the illumination light, even a reproducing apparatus in which a laser beam of about 1 to 3 mmφ emitted from a light source such as an ordinary semiconductor laser is directly incident is provided within an area of 1 mmφ. Since the computer generated hologram sufficiently exhibits the above-mentioned effect, no special optical parts are required, and inexpensive and easy information reproduction can be realized (claim 4).

If the information recorded in two or more types of computer generated holograms is the same information, a certain amount of information can be always read under a plurality of reproduction conditions corresponding to the computer generated holograms. Item 3). Here, it is possible to increase the amount of recorded information by preparing more types of computer generated holograms and recording different information.

If two kinds of computer generated holograms are used and the carrier waves are in substantially the same direction and orthogonal to each other, the optical information recording medium of the present invention can be used while keeping the relationship between the illumination light and the screen, the light receiving element and the like during reproduction. Different information can be reproduced only by changing the relative angle between them by 90 # (claim 5).

Of course, when the same information is recorded on two types of holograms, the same information is reproduced. For example, when the optical information recording medium of the present invention is attached to the surface of a card, different information can be reproduced by changing the direction of inserting the card into the reading machine (portrait or landscape), or It is possible to always perform stable information reproduction regardless of the direction. Besides cards
When applying the optical information recording medium of the present invention to a medium having a substantially rectangular outer shape such as securities, the angle of 90 # can be easily and accurately changed, so that the structure is simple and inexpensive. It is possible to easily reproduce a plurality of pieces of information even with various information reading devices, and since the two reproduction conditions are greatly different, it is possible to significantly improve the forgery prevention effect.

At this time, since + 1st-order diffracted light and -1st-order diffracted light are emitted in contrast to each other in a normal computer-generated hologram, it is preferable to use two types of computer-generated holograms. In the case of a computer generated hologram capable of emitting only the next-order diffracted light, four pieces of information having the same effect as described above can be recorded corresponding to four types of carrier waves which differ by 90 #.

On the other hand, by using a plurality of computer generated holograms in which the carrier waves have the same directional component and different spatial frequencies, it is possible to obtain different reproduced images by changing the angle of the illumination light. (Claim 6). In the case of claims 5 and 6, it is possible to change the information reproduced on the light receiving element or the screen by changing the angle of the illumination light or the like while keeping the position of the light receiving element or the screen constant, and reading a large amount of information. Is easy. Especially, if a plurality of illumination light sources are arranged in advance so that the reproduction information can be instantly switched by switching ON / OFF of each light source,
It is also possible to read a large amount of information at high speed.

In the above, by using a Fourier transform hologram as the computer generated hologram, it is possible to record information easily and to reproduce information easily and surely (claim 7).

At this time, by arranging the same computer generated hologram in a certain area, when the beam-shaped illumination light is used, it becomes stable no matter which position in the area the information reproduction illumination light enters. Information can be reproduced. Regarding the stability of this reproduction (information reading), when beam-shaped light is used as the illumination light for information reproduction, the density of computer hologram arrangement is set so that at least one computer hologram falls within the beam diameter. It is desirable to do.
In particular, if a plurality of identical computer generated holograms are recorded in a small area, a plurality of computer generated holograms will be included within the beam diameter of the illumination light, and the brightness of the reproduced image can be increased (claim 8).

Further, by arranging computer generated holograms having the same carrier wave and different information recorded at different positions on the base material, the optical information recording of the present invention with respect to illumination light or the like can be performed while the reading condition remains constant. Different information will be reproduced when the relative position of the medium is changed. Therefore, the amount of recorded information can be increased (claim 9).

A display body formed by arranging a plurality of cells each composed of a diffraction grating as a pixel changes the color, the observable direction and the brightness at the time of observation for each pixel depending on the spatial frequency, angle and diffraction efficiency of the diffraction grating. As a result, it is possible to display an image, characters, etc. that can be visually observed under normal observation conditions. At this time, the first-order diffracted light from the diffraction grating is mainly used for observation. By arranging the cell composed of such a diffraction grating and the computer hologram on which information is recorded on the same substrate, the visual effect by the former and the information recording by the latter can be compatible (claim 1).
1-13).

In particular, if the main 1st-order diffracted light from the cell and the main 1st-order diffracted light from the computer generated hologram are prevented from overlapping with each other, the images and information reproduced from them are observed and read under different reproduction conditions. Therefore, it is possible to realize low noise reproduction of the displayed image and information without disturbing each other, and it is also effective for concealing recorded information (claim 12). This is the diffraction grating that makes up the cell,
With respect to the carrier wave of the computer generated hologram, both can be easily realized if they have sufficiently different spatial frequencies and / or sufficiently different angles. In order to satisfy the “sufficient” condition, the carrier frequency of the computer generated hologram and the frequency bandwidth of the recorded information may be taken into consideration with respect to the spatial frequency and direction of the diffraction grating.

Depending on the spatial frequency and the direction of the diffraction grating in the cell, the observation color and the observable direction of the pixel of the display image can be set and the various colors can be expressed while maintaining the above effects. It is possible to realize a display in which the observed image changes depending on the viewpoint position (claim 13). It is also possible to hide the computer generated hologram (make the diffracted light from the computer generated hologram unnoticeable) by setting many observable directions in a complicated manner.

In the above, when the information recorded on the computer generated hologram is machine read data, the recorded information cannot be read even when observed with the naked eye, and more information can be read by the machine. There are effects such as concealment and facilitation of authenticity determination (claim 1
0, 14).

Further, by making the information recorded on the computer generated hologram into a two-dimensional pattern, it becomes easy to judge the authenticity by observing with the naked eye. Various patterns such as images, characters and logo marks can be recorded as patterns. On the other hand, in machine reading, by reading two-dimensional information, it becomes possible to read a lot of information at once. Furthermore, even in the recording of computer generated holograms, 2
By setting the dimensional pattern as the light intensity distribution on the cross section of the object light, the pattern of the computer generated hologram can be easily calculated.

When used in combination with a diffraction grating cell, the size of the cell and the size of the computer generated hologram are each set to 300 μm or less so that the cell structure is made inconspicuous under normal observation conditions and a high quality image is obtained. In addition to enabling display, it is possible to make the computer generated hologram less noticeable to the naked eye. Further, when the optical information recording medium is relatively small and the observation distance is small, it is desirable to use a cell and a computer generated hologram having a size of 100 μm or less. When the cells and the computer generated holograms are arranged in a checkered pattern or the like, if they are each set to 50 μm or less, the effect of hiding the computer generated holograms with the naked eye and the resolution of the display image by the cells are sufficient.

In particular, in order to make it difficult for the naked eye to identify the presence of a cell composed of a computer generated hologram, it is preferable to hide the optical information recording section in the display pattern of the decorative image, as described above. The reason for defining the size of the diffraction grating cell and the computer generated hologram is based on the following grounds regarding the size (resolution) that can be discriminated by the naked eye.

In determining the size of a cell (dot) that is difficult to identify with the naked eye, consider the case where, for example, a person with a visual acuity of 0.7 views a pattern at a distance of 70 cm. The resolution of the human eye with a visual acuity of 0.7 is 1.4 minutes (= 1.4 ° / 60), and two points separated by 70 cm or more and 300 μm or more can be identified. Therefore, when viewing the diffraction grating pattern at a distance of 70 cm, cells (dots) whose size is 300 μm square or less
, Its existence (and of course its shape) cannot be recognized. The case where a person with better eyesight than the above case approaches and visually recognizes the pattern will be considered below.

(1) The resolution of the human eye with a visual acuity of 1.0 is 1.0 min = (1.0 / 60) °, and it is 150 cm at a distance of 50 cm.
It is possible to identify two points separated by at least μm. (2) The resolution of the human eye with a visual acuity of 1.5 is 0.66 minutes =
It is (0.66 / 60) °, and it is possible to identify two points separated by 30 cm and 58 μm or more.

In the case of the above (1), if it is 150 μm square or less and in the case of the above (2) it is 58 μm square or less,
The observer cannot distinguish the shape of the cell (dot), and if the size of the cell (dot) is made much smaller than 300 μm square, the object of the present invention is further met. The case is general and within a reasonable numerical range.

[0039]

FIG. 1 is an explanatory diagram showing an embodiment of an optical information recording medium according to the present invention, which is used as a display body having not only information recording (reproduction) but also a display function by a decorative image. It shows the case of taking the form of. In the example shown in FIG. 1, the optical information recording medium 10 has a decoration image (mountain) formed by a collection of cells composed of simple diffraction gratings and computer holograms. Diffraction grating cells and cells composed of computer generated holograms 1 and 2 are arranged close to each other in a small area which constitutes a part of the mountain. Since the computer generated holograms 1 and 2 each have a carrier wave larger than the frequency bandwidth of the recorded information, even if they are illuminated at the same time, the reproduced information does not spatially overlap and can be read independently. Therefore, it is possible to reproduce information with less noise without adversely affecting each other. Further, by forming a decorative image by using the diffraction grating cells together, the optical information recording medium 10 can also have a visual effect with the naked eye.

FIG. 2 is an explanatory diagram showing how information is reproduced from the optical information recording medium 10 of FIG. In FIG. 2A, a beam emitted from a light source is incident on a small area, and two types of computer generated holograms 1 and 2 are arranged close to each other in the small area.
Shows that different information is being reproduced from each. The xy plane is a screen plane (or a light receiving element plane), and the information reproduced on this plane is actually observed or mechanically read.

FIG. 2B is a conceptual diagram showing the spatial arrangement of two types of reproduced images on the screen surface (or the light receiving element surface). The carrier of the computer generated hologram corresponds to the center position of each reproduced image. That is, the spatial frequency of the carrier wave corresponds to A1 and A2, and the direction is
Equivalent to B1 and B2. C1x and C1y are frequency bandwidths of the reproduced image 1 in the x and y directions. "The difference in carrier wave is larger than the frequency bandwidth of the reproduction information from the computer generated hologram" defined in the present invention means that the reproduced images 1 and 2 do not spatially overlap with each other as shown in FIG. Means

These frequency band widths correspond to the width of the distribution of the actually recorded information. Therefore, in the optical information recording medium of the present invention, even when different information is reproduced at a time because a plurality of types of computer generated holograms are present in a small area, each information is sufficiently separated, so there is little noise, It is possible to obtain a very good reproduced image. That is, high image quality is realized when the reproduced image is observed with the naked eye, and highly accurate information reading is realized when mechanical reading is performed.

FIG. 3 is an explanatory view showing an observation example of the optical information recording medium 10 of FIG. 1 (which is also referred to as a display body in the figure because it also has a decorative image) under normal observation conditions. FIG. 3 shows a state of being illuminated with illumination light from a light source in the yz plane. Each diffraction grating cell on the optical information recording medium 10 emits first-order diffracted light, and
The first-order diffracted light distributed in the vicinity of the axis is incident on the pupil, and the display image is viewed. In the above optical information recording medium 10, (simple)
The spatial frequency and direction of the diffraction grating constituting the diffraction grating cell are made different from the carrier wave of the computer generated hologram (in consideration of the frequency bandwidth of recorded information). Therefore, in the observation as shown in FIG. 3, the first-order diffracted light from the computer generated hologram does not interfere with the display image in normal observation, and it is possible to display a desirable image independent of the existence of the computer generated hologram.

FIG. 4 is an explanatory view showing another example of information reproduction from the computer generated hologram arranged on the optical information recording medium. In the figure, light from a light source with a narrow wavelength band such as a semiconductor laser diode is collimated and made incident on the optical information recording medium of the present invention, and the first-order diffracted light from the computer generated hologram on the optical information recording medium is converted into parallel light. The information is reproduced by receiving it on the screen. The recorded information can be easily read by observing the pattern on the screen with the naked eye or by directly receiving light with a CCD or the like without placing the screen. For example, if an object having a two-dimensional pattern (recording information) is previously arranged at the screen position during reproduction and a computer generated hologram is generated as object light, the two-dimensional pattern is imaged on the screen during reproduction and the contrast is increased. Highly accurate reproduction of information becomes possible. Further, at this time, the information cannot be reproduced unless the position of the screen or the like is known, which is further effective in hiding the information and preventing forgery. Note that the computer generated hologram corresponding to the reproduction method as shown in FIG. 4 has a plurality of computer generated holograms forming one reproduction information as a whole in terms of the quality of reproduction information (brightness, contrast, resolution, etc.). It is desirable to reproduce these at once with parallel light.

By using a Fourier transform type computer generated hologram obtained by subjecting the recorded information to a two-dimensional light intensity pattern and subjecting it to Fourier transform, and using it as a computer generated hologram in the optical information recording medium of the present invention. Therefore, it becomes possible to easily record / reproduce information. Figure 5
It is explanatory drawing which shows an example of the information reproduction from the computer generated hologram (Fourier transform hologram) on an optical information recording medium.
In the figure, a beam from a light source with a narrow wavelength band such as a laser diode in the xz plane is incident on the optical information recording medium of the present invention, and the first-order diffracted light from the computer generated hologram on the optical information recording medium. Is optically Fourier transformed by a lens and projected on a screen to reproduce information. Similar to FIG. 4, information can be read by observing the pattern on the screen with the naked eye or by directly receiving light with a CCD or the like without placing the screen. At this time, by arranging the distance between the optical information recording medium and the lens and the distance between the lens and the screen to be equal to the focal length of the lens, an optical "Fourier transform" is performed during reproduction.
Can be realized.

On the other hand, even without the lens, since the Fraunhofer diffraction image equivalent to the Fourier transform image is projected on the screen placed at a certain distance, the same information reading can be easily realized. FIG. 6 is an explanatory diagram showing an example of information reproduction from a computer generated hologram (Fourier transform hologram) on the optical information recording medium of the present invention without a lens in the same case as FIG. Observation and reading of an image as a Fraunhofer diffraction image as shown in FIG. 6 is characterized in that the projection size changes depending on the distance between the optical information recording medium of the present invention and the screen, and the projection size is changed to a size suitable for reading or the like. Easy to do.

FIG. 7 is an explanatory diagram showing how information is reproduced from the optical information recording medium when computer generated holograms having different carrier waves are arranged in a small area. That is, both FIG. 7A and FIG. 7B show the case where the illumination light is in the xz plane, but the incident angles to the optical information recording medium are different. Even in this case, the reproduction light from the computer generated hologram whose conditions match each other (the carrier wave corresponds to the incident condition of the illumination light) produces a reproduction image (+ 1st order diffracted light) in the screen (or light receiving element) direction. FIG. 7C shows
When the illumination light exists in the y-z plane and the reproduction conditions are different from those in FIG. 7A and FIG. 7B, the reproduction light from the computer generated hologram which meets the conditions is the screen (or the light receiving element). ) Direction, a reproduced image (+ 1st order diffracted light) is generated. Here, the difference in the spatial frequency of the carrier in FIG. 2 corresponds to the difference between FIGS. 7A and 7B, and the difference in the direction (angle) of the carrier is shown in FIGS. 7A and 7B. And Fig. 7
This corresponds to the difference from (c). Of course, these figures are typical examples, and in practice, the spatial frequency and direction of the carrier wave can be arbitrarily selected, so that various reproduction conditions can be set.

In the above description, the case of the reflection type diffraction grating and the computer generated hologram has been mainly described, but the transmission type can be handled in the same manner.
Further, the number of computer generated holograms may be two or more, and the amount of information can be further increased by arranging many types of computer generated holograms in a small area. The diffraction grating cell and the computer generated hologram forming the optical information recording medium of the present invention can be applied to any type of diffraction element such as a phase type represented by surface relief and an amplitude type represented by density expression.

[0049]

As described above, according to the present invention,
Even when reproducing multiple pieces of information from a small area by adapting to multiple pieces of reproducing conditions, the reproduced information can be recognized separately without overlapping, and highly accurate information reproduction with less noise is possible. Provided is an optical information recording medium capable of recording high density information. In addition, since the cell formed of the computer generated hologram that constitutes the optical information recording unit has a size of 300 μm square or less, the presence of the cell is difficult to be visually recognized under normal observation conditions and forms a decorative image. When the above-mentioned cells (computer hologram) are mixed inside a group of diffraction grating cells, a visual effect (decorative effect)
Therefore, it is possible to realize an information recording medium which is suitable for hiding specific information by a computer generated hologram without impairing the above, and which also has a design property.

[0050]

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of an optical information recording medium according to the present invention, and an explanatory diagram according to an embodiment as a display body in which cells made of computer generated holograms are incorporated inside a decoration image made of diffraction grating cells.

2 is an explanatory diagram showing how information is reproduced from the optical information recording medium 10 of FIG. 1. FIG.

FIG. 3 is an explanatory diagram showing an observation example of the optical information recording medium 10 of FIG. 1 (which is also referred to as a display body in the figure because it also has a decorative image) under normal observation conditions.

FIG. 4 is an explanatory diagram showing another example of information reproduction from a computer generated hologram arranged on an optical information recording medium.

FIG. 5 is an explanatory diagram showing an example of information reproduction from a computer generated hologram (Fourier transform hologram) on the optical information recording medium.

FIG. 6 is an explanatory diagram showing an example of information reproduction from a computer generated hologram (Fourier transform hologram) on the optical information recording medium of the present invention without a lens in the same case as in FIG. 5;

FIG. 7 is an explanatory diagram showing how information is reproduced from the optical information recording medium when computer generated holograms having different carrier waves are arranged in a small area.

[Explanation of symbols]

1,2 ... Computer hologram 10 ... Optical information recording medium

Claims (14)

[Claims] 1. An optical information recording medium having an optical information recording section composed of a computer generated hologram on the surface of a substrate, wherein each computer generated hologram is a cell having a size of 300 μm square or less, and each cell has a specific Information is recorded, and two or more types of computer hologram cells, each of which has a different carrier wave, are arranged in a small area, and the difference between the carrier waves of the cells is larger than the frequency bandwidth of the reproduction information from the computer hologram. An optical information recording medium characterized by being large. 2. An optical information recording medium according to claim 1, wherein the computer generated holograms, which are composed of carrier waves different from each other in the small area, record reproduction information different from each other. 3. The optical information recording medium according to claim 1, wherein the computer generated holograms having different carrier waves in the small area are recorded with the same reproduction information. 4. The optical information recording medium according to claim 1, wherein the small area is 1 mmφ or less. 5. The computer generated holograms existing in the small area are composed of two carrier waves having substantially the same spatial frequency components, and are set in directions substantially orthogonal to each other. 4. The optical information recording medium according to any one of 4 to 4. 6. A computer generated hologram in a small area, two types of which are composed of carrier waves having substantially the same directional components, and are set to different spatial frequency components from each other. 4. The optical information recording medium as described in 4 above. 7. The computer generated hologram is a Fourier transform hologram in which two-dimensional information prepared in advance is Fourier transformed and recorded as an object light component.
6. The optical information recording medium according to any one of 6. 8. The same computer generated hologram includes a plurality of small areas, each of which is arranged.
An optical information recording medium according to any one of 1. 9. The light according to claim 1, wherein a computer generated hologram having the same carrier wave and different reproduction information is recorded at different positions on the surface of the base material. Information recording medium. 10. The optical information recording medium according to claim 1, wherein the reproduction information recorded on the computer generated hologram is data suitable for machine reading. 11. A pattern is obtained by arranging a plurality of cells made of a diffraction grating as pixels in addition to cells made of a computer generated hologram on the surface of the substrate having the computer generated hologram according to claim 1. A display body characterized by expressing patterns such as characters and symbols. 12. The display according to claim 10, wherein the reproduction directions of the main 1st-order diffracted light from the cell made of the diffraction grating and the main 1st-order diffracted light from the computer generated hologram do not overlap. 13. An observation color and an observable direction of a pixel included in a displayed pattern are set according to a spatial frequency and / or a direction of a diffraction grating included in a cell including the diffraction grating. Claim 11 or 12
Display body described in. 14. The display according to claim 11, wherein the reproduction information recorded on the computer generated hologram is data suitable for machine reading.