JP2002341733A - Display body and method for reproducing information from the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display body in which both of information normally visually unrecognizable (latent images) and decorative images with gradation recognizable by normal visual observation are recorded on one medium and the information is recorded without degrading the design for the purpose of use. SOLUTION: A cell consisting of a hologram in which information reproducible with light at specified wavelength is prepared as the structural element and a plurality of the cells are arranged as pixels. The diffraction efficiency or scattering efficiency of each cell is properly varied to represent an image with gradation. The image with gradation acts as a decorative image visually recognized, while other information is reproduced by using the light at specified wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display body having a decorative image composed of cells each composed of a hologram in which information reproducible by light of a specific wavelength is recorded, and the decorative image recorded on the hologram. And a method for reproducing specific information.

[0002]

2. Description of the Related Art As a method of recording specific information on a hologram and reading the information, a method utilizing a Fourier transform hologram is known. When predetermined light enters a hologram that records such information,
The recorded information is reproduced by the first-order diffracted light. But,
Such a hologram is observed as a whitish region when observed with the naked eye, and has no function as a decorative image.
This has been a cause of deteriorating the design of articles using holograms. Further, when concealed information is recorded, there is a problem that the area where the information is recorded can be estimated by visual observation.

[0003]

SUMMARY OF THE INVENTION According to the present invention, information (latent image) which cannot be normally observed or read, and a gradation image which can be recognized by ordinary visual observation are recorded on the same medium. Accordingly, a main object of the present invention is to provide a display body on which information is recorded without impairing the design of an application. In particular, in security applications, the object is to provide a display body that can accurately determine whether the information is true or false by confirming different information in two ways, that is, information reading by a machine and visual observation. I have.

[0004]

According to the present invention, there is provided a display comprising a cell composed of a hologram recording information reproducible by light of a specific wavelength, a plurality of cells arranged as pixels, and a diffraction efficiency of each cell. Alternatively, a gradation image is expressed by appropriately changing the scattering efficiency. The gradation image becomes a decorative image that can be visually recognized, and specific information different from the decorative image that can be read by a machine is recorded in each of the cells formed of holograms that are pixels, such as white light. Under normal observation conditions, only the former is recognized, but the latter is recognized only by irradiation with light of a specific wavelength.

[0005] The diffraction efficiency or the scattering efficiency is the ratio of the diffracted light or the scattered light incident on the pupil of the observer to the incident light under the normal observation condition. , And in a normal indoor lighting environment such as a fluorescent lamp or an incandescent lamp, which means that the observer performs normal observation with the naked eye.)

[0006] Thereby, in normal observation, a gradation image displayed by diffracted light or scattered light on the display of the present invention can be observed.

On the other hand, when light such as laser light is incident on the display of the present invention under predetermined conditions, information is reproduced by being projected on a screen or the like at a predetermined position. Such information can be read with the naked eye,
It is also easy to read with a machine (with a receiver such as a CCD camera at the screen position).

Therefore, the display body of the present invention can display a gradation image arbitrarily designed (observable with the naked eye) and can record information while concealing the information. Further, the information to be recorded may be two-dimensional information or three-dimensional information. Accurate reproduction can be made impossible without knowing the reproduction method, and at the same time, a large amount of information can be recorded / reproduced.

The images and information in the present invention refer to those expressed by spatial light intensity distribution, such as letters, numbers, photographs, figures, patterns, and bar codes. In particular, the information includes three-dimensional information (such as a three-dimensional image).

[0010] Further, the information is characterized by being represented by a group of a plurality of information recording units arranged on a plane. For information arranged in a plane, it is sufficient to display the information in a plane when creating a hologram with an optical system, and when it is generated by a computer such as a computer hologram, the calculation can be simplified, making it very simple You can do it.

In addition, since information is reproduced on a plane during reproduction, accurate reading can be easily performed.

Here, as the hologram, a Fourier transform hologram in which a group of a plurality of information recording units is Fourier-transformed and recorded as object light is used. When a Fourier transform hologram is used as a cell, an optical system captures a Fourier transform image using a lens, and a computer calculates a Fourier transform algorithm.
A hologram can be produced very easily. At the time of reproduction, the reproduction information is projected at infinity, so that if the screen is placed at an arbitrary distance, the reproduction information can be observed. Also, information can be reproduced by projecting a Fourier transform image of the reproduction light on a screen or the like using a lens.

When a gradation image expressed by using a Fourier transform type hologram as a cell is visually observed under normal observation conditions, information is blurred due to the wavelength distribution of illumination light, and information is subjected to Fourier transform. Therefore, it is impossible to recognize the contents of the information.

The hologram may be a Fresnel hologram in which a light intensity distribution corresponding to a group of a plurality of information recording units is recorded as object light arranged at a finite distance from the hologram surface.

When a Fresnel hologram is used as a cell, by placing a screen at the position (including the distance) where the information is to be produced at the time of producing the cell, the reproduced information that has been formed can be clearly observed. That is, only those who know the location of the information can read the accurate information,
Information recording with high security can be realized.

When a gradation image expressed by using a Fresnel hologram as a cell is visually observed under normal observation conditions, the effect of blurring information due to the wavelength distribution of illumination light is great, and the contents of the information are recognized. It is impossible.

The hologram may be a computer generated hologram (including a kinoform). When a cell is manufactured as a computer generated hologram, it is easy to manufacture the display of the present invention by changing information to be recorded for each cell. In addition, not only information but also information reproduction position and hologram method (Fourier transform hologram, Fresnel hologram, etc.) can be easily set for each cell, so that forgery prevention effect can be enhanced and information can be read easily. Can be

In particular, by making the computer generated hologram a kinoform type, the brightness of the reproduced information can be maximized, the error of the information reading can be reduced, and the optical duplication for the purpose of forgery can be achieved. It can be extremely difficult.

In the present invention, it is preferable that the same information is recorded in a plurality of cells in an area of at least 1 mmφ. Thereby, even if the incident position of the light for illuminating the display of the present invention for information reproduction is slightly changed, stable information reproduction is possible.

Since a normal laser beam has a beam diameter of about 1 mmφ, even if the laser beam is used as it is as illumination light, since the beam incident area is a cell for reproducing the same information, the laser beam has a small noise and is accurate. Information reproduction can be realized.

In the present invention, different information may be recorded in a plurality of areas on the display. Since different information can be reproduced from a plurality of regions, the amount of information can be increased, and the forgery prevention effect can be further enhanced by using the plurality of information for authenticity determination.

Alternatively, different information may be recorded for each cell. Thereby, a very large amount of information can be recorded / reproduced. In particular, if the cell is sufficiently small, more information can be recorded per unit area, and the normal laser beam emitted from the laser light source illuminates multiple cells simultaneously, resulting in an information hiding effect. Can be increased.

Alternatively, the same information may be recorded in a plurality of cells arranged in one direction, and the cells in which different information is recorded may be arranged in a direction orthogonal to the one direction. As a result, the tolerance of the incident position of the illumination light at the time of reproducing the information in the cell direction where the same information is recorded is increased, while the information recording density can be increased in the direction orthogonal to the direction.

Therefore, a large amount of information can be easily reproduced by scanning the laser beam or the like in the orthogonal direction, and the requirement for the accuracy of the incident position of the beam or the like in the direction orthogonal to the scanning direction can be reduced. Stable information reproduction can be easily performed.

The present invention is characterized in that a gradation image is expressed by a change in diffraction efficiency or scattering efficiency for each cell. As a result, an image having a gradation can be displayed completely independently of the information recorded in each cell, and a high-design display that does not depend on the recorded information can be displayed under normal observation conditions. In particular, when the display of the present invention is applied to cards, securities, and the like, any design that can be observed with the naked eye can be expressed, and in addition to reading information recorded in cells, it can be used for authenticity determination and the like. Can help.

The diffraction efficiency is the same as the diffraction efficiency due to the hologram. However, when the spatial spread of the reproduced information is large, the diffracted light and the scattered light can be handled in the same way under the ordinary illumination condition. Is proportional to the diffraction efficiency of the hologram.

In the present invention, the size of the cell is preferably 300 μm or less. When the size of the cell is 300 μm or less, when expressing a gradation image using the cell as a pixel, it is difficult for the naked eye to determine the pixel structure, and an image with a sufficient resolution can be displayed.

When it is assumed that the observer looks at the display with the face close, the size of the cell is desirably 100 μm or less. If 100 μm or less, 30 observers with a visual acuity of 1.0
Even when observed at a distance of about cm, the cell structure is difficult to discriminate, and it can be observed as a high-quality image under most practical observation conditions.

Further, by setting the cell size to 300 μm or less, desirably 100 μm or less, there are advantages such as an increase in the amount of information and an improvement in stability of information reproduction (because the area where illumination light is incident is desirably larger than the cell size). is there.

The information recorded in the cell may be an image. This makes it possible to easily determine whether the information is true or false by observing it with the naked eye, for example, by projecting the information onto a screen. Further, by comparing a gradation image in which a cell is represented as a pixel with an image that is information, it is possible to easily determine whether the image is true or false (for example, both images have the same pattern, Or another image that has the meaning of

As a method of reproducing information from any of the above-mentioned display bodies, at least a part or all of the display body is irradiated with a parallel light beam or a beam, or a convergent light beam or a divergent light laser beam. Information recorded from one cell is reproduced, and the information can be read. Since the laser light has good directivity and is light of a single wavelength, accurate information reproduction with less noise and blur can be easily realized.

In particular, when a cell composed of a Fresnel hologram is used, the effect is large because the reproduced information forms a spatial image. When the cell is a Fourier transform type hologram, by using convergent light or divergent light, the apparent size of the reproduced information can be easily changed even if the distance from the display body of the present invention is constant. Can be.

In particular, when information is read by machine, the size and resolution of the information to be reproduced can be appropriately adjusted in accordance with the spatial accuracy (resolution) of machine reading, and the cost is reduced. High-precision reading can be realized even with a simple reading device.

Further, at this time, the illumination light is light from a general light source, and information is reproduced by reading only a specific wavelength. As a result, a light bulb, LED, or the like can be used as a light source, and an inexpensive and simple reader can be realized.

[0035]

FIG. 1 is an explanatory view showing an example of a display according to the present invention. On the display 1, characters and images having gradations are displayed with the cell 2 as a pixel. Each cell 2 is a hologram, and gradation is expressed by a change in the diffraction efficiency or the scattering efficiency of the hologram.

When the change in the diffraction efficiency of the hologram is used, the change in the intensity of the diffracted light (mainly the first-order diffracted light) corresponds to the gradation, and when the change in the scattering efficiency is used, the change in the intensity of the scattered light is different. Corresponding to the key. As described above, the scattered light referred to here is equivalent to diffracted light under normal illumination conditions when information recorded on the hologram is reproduced, and when the spatial spread of the reproduced information is large. Since light and scattered light can be treated similarly, the scattering efficiency is proportional to the diffraction efficiency by the hologram.

For example, in the case of a surface relief hologram, the diffraction efficiency can be controlled by changing the depth of the relief (concavity and convexity) for each cell.

Under normal illumination conditions, the display body of the present invention is illuminated with white light, so that the gradation image 10 looks slightly rainbow-colored as diffracted light and looks whitish as scattered light.

When the gradation image 10 is expressed by a change in the diffraction efficiency, the color at the time of visual observation changes due to the spatial distribution of the information recorded in the hologram. If information is recorded in the same manner, the color at the time of visual observation can be made uniform.

On the other hand, by appropriately designing the spatial distribution range of information, it is possible to set the observation color in each cell at the time of visual observation, and it is also possible to display a color image with gradation.

In the display 1 of the present invention, the information recorded on the hologram and the image 10 displayed with the hologram cell 2 as a pixel can be independent, and each can be arbitrarily designed. Under normal observation conditions, only the characters and images expressed with the cell 2 as pixels can be observed with the naked eye, and the pattern recorded in the hologram cannot be observed. The change in the diffraction efficiency and the scattering efficiency for each cell results in the brightness of information reproduced from each cell at the time of information reproduction, but does not affect the content of the information.

The cells constituting the display of the present invention are as follows:
It may be a surface relief type hologram, and can be in a form suitable for low-cost mass production by embossing technology or the like.

FIG. 2 is an explanatory diagram showing an example of reproducing information from a display according to the present invention. When a laser beam or the like is incident on the display shown in FIG. 1 as illumination light 7, information is reproduced as hologram diffracted light from each cell 2. At this time, if the hologram cell 2 in which the same information is recorded in a certain area or more on the display body 1 is arranged, an allowance for a change in the incident position of the illumination light can be obtained, and the reproduction becomes easy. If only one piece of information is reproduced at a time, S /
Clear information with a high N can be reproduced. In these cases, the size of the area where the same information is recorded is desirably 1 mmφ or more because the ordinary laser beam is about 1 mmφ or more.

FIG. 3 is an explanatory diagram showing another example of reproducing information from the display according to the present invention. Display body 1 of the present invention shown in FIG.
Then, a laser beam or the like is applied to an area other than the area shown in FIG.
This is an example in which light is incident.

As in FIG. 2, information is reproduced as hologram diffracted light from each cell 2. Here, an example is shown in which information different from the area illuminated in FIG. 2 is recorded. In this way, by changing the information to be recorded for each area, much information can be recorded. Recording and reproduction of a lot of information is more effective for forgery prevention and the like.

In order to record the most information, different information may be recorded for each cell. Increasing the information recorded in one cell is also effective in increasing the amount of information.

FIG. 4 is an explanatory view showing an example of a method for manufacturing the cell 2 composed of a Fresnel hologram. Information is displayed as a light transmission pattern on an information display panel (transmission film, LCD panel, or the like) 20, and the object light 21 and the reference light 22 that have passed through the information display panel 20 are allowed to reach a hologram recording surface 27 through a slit 25. In this example, an interference fringe is recorded on a photosensitive material placed on the recording surface 27 to record a hologram of one cell (coherent light is used as the object light and the reference light). At the time of transmission through the information display panel, it is desirable to scatter simultaneously. The size of the slit is the size of the cell.

Thus, the hologram recording medium (2)
7) By recording a plurality of cells while changing the relative position of the slit 25 with respect to the information display panel 20 and changing the exposure amount or the like depending on the gray scale of the display image visually, the present invention Can be manufactured. Of course, the information to be recorded can be selected for each cell by appropriately changing the display information on the information display panel every time a cell is manufactured.

The reference light 22 corresponds to illumination light at the time of reproduction. That is, at the time of reproduction, the illumination light 7 is incident on the display 1 at an angle which has a conjugate relationship with the reference light at the time of cell production.
The position of the information display panel 20 corresponds to the position where the reproduction information forms an image during reproduction. Therefore, by placing the screen at the position of the information display panel 20 at the time of manufacturing the cell, the reproduced information can be clearly observed. If a CCD camera or the like is placed at the position of the screen, machine reading can be performed accurately.

As described above, when the information display panel 20 and the hologram recording surface 27 are at a finite distance, the cell 2 becomes a Fresnel hologram. By using a Fresnel hologram as a cell, clear information can be reproduced only at the position of the information display panel when the cell is manufactured. That is,
Only a person who knows the position of the information display panel can read accurate information, and information recording with high security can be realized.

FIG. 5 is an explanatory view showing an example of a method for producing a cell composed of a Fourier transform type hologram. Information is displayed as a light transmission pattern on an information display panel (transmission film, LCD panel, or the like) 20, and the object light 21 obtained by condensing the transmitted light through a lens 29 and the reference light 22 through a slit 25 are holograms. In this example, interference fringes are recorded on a photosensitive material placed on the hologram recording surface, and a hologram of one cell is recorded (the object light and the reference light use coherent light).

Here, the information display panel 20 and the lens 29
And the distance between the lens 29 and the hologram recording surface 27 are preferably the focal lengths of the lenses. Further, it is desirable that the light is simultaneously scattered when transmitted through the information display panel. The size of the slit is the size of the cell.

In this manner, a plurality of cells can be recorded while changing the relative position between the hologram recording medium and the slit, and changing the exposure amount or the like depending on the gradation of the display image visually. Thus, the display of the present invention can be manufactured. Of course, the information to be recorded can be selected for each cell by appropriately changing the display information on the information display panel every time a cell is manufactured.

The reference light 22 corresponds to illumination light at the time of reproduction. That is, at the time of reproduction, the illumination light 7 is incident on the display 1 at an angle which has a conjugate relationship with the reference light at the time of cell production.

At the time of reproduction, since the reproduction information is projected at infinity, if the screen is placed at an arbitrary distance,
Playback information can be observed. Of course, if the lens 29 is arranged in a reverse relationship to that at the time of manufacturing the cell and the screen is placed at the position of the information display panel 20 at the time of manufacturing the cell, the information formed on the screen can be reproduced. In either case,
If a CCD camera or the like is placed at the position of the screen, machine reading can be performed accurately.

The cell 2 manufactured as described above is composed of a Fourier transform type hologram. In FIG. 4,
When the distance between the information display panel 20 and the hologram recording surface 27 is much larger than the size of the slit, a hologram equivalent to a Fourier transform hologram can be obtained.

By using a Fourier transform type hologram as a cell, reproduced information can be observed at an arbitrary position, thereby facilitating information reproduction. In particular, when the position of the screen or the CCD camera or the like at the time of reproduction is separated from the display of the present invention, the reproduced image becomes large. Therefore, the size of the reproduced image can be appropriately changed to a size suitable for observation or machine reading.

Although the transmissive information display panel 20 has been described with reference to FIGS. 4 and 5, the present invention can be similarly applied to a reflective information display panel. Further, the information display panel is not limited to a planar shape.

FIG. 6 is an explanatory diagram showing information reproduction from the display 1 of the present invention when the wavelength filter 30 is used.

Even if the display 1 is illuminated with parallel white light, if the light passes through a wavelength filter that transmits only light of an appropriate wavelength before the light reaches the screen to be observed or the CCD camera to be read, it is accurate. Information can be reproduced. In addition to white light, an inexpensive and compact information reproducer can be realized by collimating light from an LED or the like as illumination light and transmitting the light through a wavelength filter.

[0061]

As described above, information (latent image) which cannot be normally observed or read and a decorative image having a gradation which can be recognized by ordinary visual observation are recorded on the same medium. Provided is a display body on which concealed information is recorded without impairing designability in an application.
The display body of the present invention can express a gradation image observed visually, and can reproduce information independent of the gradation image by a simple verification method, without impairing the design. Information can be recorded (concealed). Thereby, for security use, a high forgery prevention effect can be exhibited.

[0062]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an example of a display body of the present invention.

FIG. 2 is an explanatory diagram showing an example of information reproduction from a display according to the present invention.

FIG. 3 is an explanatory diagram showing another example of information reproduction from a display according to the present invention.

FIG. 4 is an explanatory view showing an example of a method for manufacturing a cell 2 made of a Fresnel hologram.

FIG. 5 is an explanatory view illustrating an example of a method for manufacturing a cell including a Fourier transform hologram.

FIG. 6 is an explanatory diagram showing information reproduction from the display 1 of the present invention when the wavelength filter 30 is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Display body 2 ... Cell 7 ... Reproduction illumination light 10 ... Image 20 ... Information display panel 21 ... Object light 22 ... Reference light 25 ... Slit 27 ... Hologram recording surface 29 ... Lens 30 ... Wavelength filter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09F 19/12 G09F 19/12 L

Claims (14)

[Claims] 1. A display body for displaying an image by arranging a plurality of cells and using the cells as pixels, wherein the cells comprise a hologram recording information reproducible by light of a specific wavelength, and the diffraction efficiency of the cells Alternatively, a display body which expresses a gradation image by scattering efficiency. 2. The display according to claim 1, wherein the information is represented by a group of a plurality of information recording units arranged on a plane. 3. The display according to claim 2, wherein the hologram is a Fourier transform hologram obtained by Fourier transforming a group of the plurality of information recording units and recording the object beam. 4. The Fresnel hologram according to claim 1, wherein said hologram is a Fresnel hologram in which a light intensity distribution corresponding to a group of said plurality of information recording units is recorded as object light arranged at a finite distance from a hologram surface. 2. The display according to 2. 5. The display according to claim 1, wherein the hologram is a computer generated hologram. 6. The display according to claim 1, wherein the hologram is a kinoform. 7. The display according to claim 1, wherein the same information is recorded in a plurality of cells within an area of at least 1 mmφ. 8. The method according to claim 1, wherein different information is recorded in each of a plurality of areas on the display.
The display according to any one of claims 1 to 7. 9. The display according to claim 1, wherein different information is recorded for each of said cells. 10. The cell according to claim 1, wherein the same information is recorded in a plurality of cells arranged in one direction, and the cells in which different information is recorded are arranged in a direction orthogonal to the one direction. The display according to any one of claims 1 to 8, wherein 11. The display according to claim 1, wherein the size of the cell is 300 μm or less. 12. The display according to claim 1, wherein the information recorded in the cell is an image. 13. When reading information from any one of the display bodies according to any one of claims 1 to 12, light or a beam substantially parallel to the whole or a part of the display body, or convergent light or divergent light. Reproducing information recorded in at least one cell by irradiating a laser beam in a shape of a circle. 14. In reading information from any one of the display bodies according to claim 1, the whole or a part of the display body is irradiated with substantially parallel light, or convergent light or divergent light. And reproducing information recorded in at least one cell by using light of a specific wavelength included in the irradiation light.