JPH05203812A - Hologram - Google Patents

Abstract

PURPOSE:To provide a hologram where a noise image is suppressed. CONSTITUTION:A hologram element 1a is formed on one surface of substrate glass 2. A reflection preventive film 5 is formed on a cover plate 3 and a scatter absorbing film 6 is formed on a cover plate 4. The light which is made incident on the hologram 1 from a light source travels in the hologram 1 and is diffracted by interference fringes as a subject recorded on the hologram element 1a and projected as reproduction light from the hologram 1. The reflection preventive film 5 prevents the light from being reflected by the border surface between the surface of the cover plate 3 and an atmosphere and reflected light, therefore, never travels as noise light in the same direction with the reproduction light. Further, light which is transmitted through the hologram element 1a is scattered by the border surface between the surface of the cover plate 4 and atmosphere and travels in the hologram 1 again to reach the same direction with the reproduction light, but the reflection is suppressed by the scatter preventive film 6.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to holograms.

[0002]

2. Description of the Related Art Conventionally, there is an increasing need for a head-up display for automobiles which improves visibility by, for example, enlarging and displaying a speed display in front of a windshield using a hologram. Then, with the increase in this need, a hologram with less noise has been desired.

Therefore, in the prior art, Japanese Patent Laid-Open No. 62-806 has been used.
As described in Japanese Patent Publication No. 87, when a hologram is exposed, a good hologram element in which noise is not recorded is obtained by forming an antireflection film on the surface of the hologram element facing the substrate and exposing the hologram element. It is known to remove the protective film to obtain a good reproduced image.

[0004]

However, in recent years,
Although it is necessary to further reduce noise, there is a tendency that the configuration of the hologram itself becomes more complicated and noise is likely to occur. It wasn't easy to get.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a hologram having a configuration capable of obtaining a reproduction light of a hologram in which noise is sufficiently reduced.

[0006]

Therefore, according to the present invention, an optically transparent substrate having one surface and the other surface facing each other, and a recording medium provided on the one surface of the substrate are provided. A hologram element having interference fringes recorded thereon, and one surface and the other surface facing each other,
It is provided on one surface side of the substrate on which the hologram element is formed, and light incident from the other surface side of the substrate passes through the hologram element, and at the boundary surface between one surface of the member and the atmosphere. When a light reflection occurs, a technical means called a hologram, which is composed of a member configured so that the reflection of the light does not enter the hologram element again, is adopted.

In the embodiment of the present invention, the above member may be called a cover member because it covers the substrate having the hologram element, and this member and the substrate are generally made of soda glass or the like. Examples thereof include glass and various plastic materials. It is desirable that the first member has an anti-scattering film on the surface side in contact with the atmosphere, and the second member has an anti-reflection film on the surface side in contact with the atmosphere.

The anti-scattering film prevents the light at the boundary surface between the surface of the first member and the atmosphere from going to the hologram element again when the light passes through the hologram element of the substrate and goes to the surface of the first member. Has a function of absorbing the light. Further, the antireflection film has a function of preventing reflection of light at the boundary surface between the surface side of the second member and the atmosphere when light is incident from the surface of the second member toward the substrate.

As the anti-scattering film, in order to form a film capable of absorbing black or dark light, for example, a synthetic resin binder such as epoxy, melanin or acrylic is used.
Examples include pigments such as black pigments added. Further, the anti-scattering film may be formed of black paint or a tape-like film if there is no problem in terms of durability and use environment. On the other hand, as the antireflection film, MgF ₂ , TiO ₂ ,
ZrO _{2 and the} like may be mentioned, and a single layer or a combination thereof may be formed into a multi-layer.

It is desirable that each member and the substrate have the same refractive index as that of the dichromated gelatin film constituting the hologram element, and the refractive index is preferably in the range of 1.5 to 1.6.

As the sealant, it is desirable to use an ultraviolet or thermosetting optical organic resin such as epoxy or acryl which is the same as or close to these members and the substrate. The sealant is set to improve the moisture resistance of the hologram element, and the seal width is set according to the water absorbability of the sealant itself and the environmental conditions of use of the hologram. The seal width refers to a portion filled with only the sealant and is shown in FIG.

The hologram element is formed by sensitizing a photosensitizer such as photopolymer, emboss, dichromated gelatin, agar and egg white. Of these, dichromate gelatin is particularly desirable. As a recording medium to be recorded in the hologram element, when the element has a function as a magnifying glass, as in Examples described later,
Of course, it may be a lens and other characters, numbers, or pictures may be recorded as a recording medium.

Laser light is used during exposure to the photosensitive agent, and the pitch of the interference fringes of the subject recorded on the photosensitive agent can be changed by changing the incident angle of the laser beam with respect to the photosensitive agent. As a result, the wavelength reproduced by the hologram element can be changed according to the Bragg reflection relationship. As a result, the hologram element
A filter function can be added. Further, by recording interference fringes having different pitches on the photosensitive material, it is possible to reproduce several kinds of colors by making white light incident on the hologram element.

In the present invention, of course, it may be semitransparent or opaque, as well as being completely transparent optically.
In this case, the condition is that light can be transmitted.

[0015]

According to the present invention, by adopting the above-described structure, the first member (first cover member) and the second member (first cover member) are prevented from causing surface reflection that causes hologram noise and scattering of transmitted light of the hologram element. It can be suppressed by the second cover member).

[0016]

According to the present invention, it is possible to obtain a high-quality display image with sufficiently reduced noise.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a cross-sectional view of a hologram 1 according to the present invention, and FIG. 2 is a plan view of FIG. In FIGS. 1 and 2, 2 is a transparent glass substrate having large surfaces facing each other, and a hologram element 1a is provided on one surface thereof. On the element 1a, a recording medium composed of interference fringes is recorded by exposing a photosensitive agent to light.
Although the recording medium will be described later, it is a concave lens as a magnifying glass. It should be noted that the hologram element 1a is changed to 290n by changing the incident light of the laser light to the photosensitive agent.
Interference fringes with two different pitches of m and 320 nm are recorded. That is, as the shape of the interference fringes, two types of interference fringes having a curvature are recorded because the concave lens and the color information are simultaneously recorded.

Reference numeral 3 is a cover plate made of transparent glass which is the second member, and has large surfaces facing each other. The cover plate 3 is arranged such that one surface side thereof faces the surface side of the substrate glass 2 which is in contact with the other atmosphere of the substrate glass 2 to which the hologram element 1a is not provided, and the other surface side is entirely antireflection. The film 5 is formed.

Reference numeral 4 is a cover plate made of transparent glass which is the first member, and has large surfaces facing each other. The cover plate 4 is arranged such that one surface side thereof faces the one surface side of the substrate glass 2 to which the hologram element 1a is provided, and the other surface side in contact with the atmosphere is prevented from scattering. The film 6 is formed.

A sealant 7 is filled between the substrate glass 2 and the cover plate 3 facing each other, and between the hologram element 1a of the substrate glass and the cover plate 4 facing each other. The element 1a is protected against the humidity of the surrounding environment.

Light is incident on the hologram 1 of the present invention on the side of the cover plate 5 as shown in FIG. 1, and the incident light passes through the antireflection film 5, the cover plate 3, and the substrate glass 2 as shown by an arrow, and then enters the hologram element 1a. To the element 1a
Is diffracted by the interference fringes. Then, the diffracted light follows the reverse path as reproduction light and is emitted.

The hologram shown in FIG. 1 is used as a head-up display for automobiles as shown in FIGS. 3 and 4, and its structure will be described.
3, an incandescent lamp 8, a liquid crystal panel 9 arranged in front of the incandescent lamp 8, a reflecting mirror 10, and a hologram 1 are assembled. The function of the liquid crystal panel 9 displays information such as speed, master warning, direction indication, and map. The display 13 is generally the instrument panel 1
It will be installed near 5.

The light emitted from the incandescent lamp 8 is the liquid crystal panel 9
Of light, is reflected by the reflecting mirror 10, and is incident on the surface of the hologram 1. The hologram element 1a of the hologram 1 (see FIG.
The reproduction light reflected by (see) is reflected by the vapor deposition film 11 vapor-deposited on the windshield 12 of the automobile, and the driver can visually recognize the display image 14 as a virtual image displayed at a distance. The display image 14 is displayed on the liquid crystal panel 9.

A hologram having the configuration shown in FIG. 8 may be used instead of the configuration shown in FIG. Explaining the hologram of FIG. 8, in this example, the size of the substrate glass 2 is set smaller by the seal width of the sealant 7.

Further, instead of FIG. 1, the hologram having the configuration of FIG. 9 may be used. Explaining the hologram of FIG. 9, in this example, the antireflection film 5 is formed directly on the other surface side of the substrate without providing the cover plate 3. With such a configuration, it is possible to obtain a miniaturized hologram having a small thickness.

Further, instead of FIG. 1, a hologram having the configuration of FIG. 10 may be used. Explaining the hologram of FIG. 10, the scattering prevention layer 6 may be formed on the surface of the cover plate 4 provided with the hologram element 1a opposite to the surface on which the hologram element 1a is formed in this example.

The hologram of FIG. 1 can be manufactured, for example, by the method shown in FIG. First, as shown in FIG. 5, dichromated gelatin (DCG) as a photosensitizer.
Is formed on the surface of the substrate glass 2 to have a film thickness of 10 μm to 40 μm, and after gelling or drying, it is stabilized in an atmosphere of 20 ° C. and about 50 RH%. Then, a concave lens as a magnifying glass is recorded on the above-mentioned photosensitive agent, and after development and drying, the substrate glass 2 provided with the hologram element 1a is sandwiched between the cover plates 3 and 4 by the sealant 7 as shown in FIG. , Fix it.

Here, in order to record an object on a photosensitive material, generally, as shown in FIG. 5, a substrate glass 2 provided with a photosensitive material, a lens 16 having a certain focal length, and a prism 1 are used.
It is sandwiched with the silicone oil 15 as a refraction adjusting liquid interposed therebetween.

Argon laser light having a wavelength of 514.5 nm is made incident as incident light from the prism 17 side. Since the refractive index is uniform after the incidence, the laser light linearly advances toward the lens 16 side, and the reflected light reflected by the reflection film 18 formed on the surface of the copying lens 16 on the atmosphere side passes through the photosensitizer. When passing, it interferes with the light directly irradiated from the laser light and before being reflected by the lens 16, and forms interference fringes in the photosensitive agent.

Part of the light reflected by the lens 16 is not reflected by the substrate glass 2 but passes through the substrate glass 2 by the refractive index adjusting liquid 15 and is incident on the prism 17, and a part is reflected by the incident surface of the prism 17. .. In this case, as shown in FIG. 5, the angle α of the incident surface of the prism 17 (30 ° in Example 1 described later) is adjusted with respect to the incident light, and the reflected light of the incident surface of the prism 4 is directed toward the photosensitive agent 1a. Do not proceed to. By disposing the prism 4 as described above, it is possible to remove display noise due to reflected light from the interface that causes noise. In addition, it is possible to prevent the reflected light from the incident surface of the prism 17 from advancing toward the photosensitive agent 1a by applying a black coating that absorbs light to the side surface of the prism 17.

With such a structure, on one surface of the substrate 2 holding the hologram element 1a, on the other surface of the substrate 1, the refractive index adjusting liquid 15 is interposed.
Since the prism 17 having substantially the same refractive index as that of No. 1 is provided, when the light reflected by the prism 16 enters the substrate 1 and is emitted again, part of the light is not reflected on the other surface of the substrate 1. Since all the light can be made incident on the prism 17, no noise image is recorded at the time of copying or recording the lens 16 on the photosensitive agent 1a.

Example 1 A substrate glass of 112 mm × 46 mm × 1.8 mm (made of soda glass, having a refractive index of about 1.52) and a thickness of 25 μm
To form a dichromated gelatin film as a photosensitizer. The photosensitizer was added to 100 ml of 4% gelatin solution at 0.6%.
It is a solution of g of ammonium dichromate and has a refractive index of about 1.55. The substrate glass provided with this photosensitizer was left for 72 hours in a dryer maintained in an atmosphere of 20 ° C. and 50% RH. Then, with the configuration of FIG.
4.5 nm argon laser light is used as the reproduction light (incident angle 3
The incident angle was changed so that the two colors of 540 nm and 600 nm were obtained (at 3.5), and the photosensitive agent was exposed to a laser power of 500 mJ in total. The focal length of the lens 16 in FIG. 5 was 1000 mm.

After the exposure, the substrate glass was washed with water until the color disappeared, and a commercially available photographic hardener fixing solution (Rapid.
It was immersed in a fixer) for 10 minutes. After washing with water, it was immersed in a 90% isopalopanol solution for 10 minutes and dried with hot air.
After that, heat aging was performed at 150 ° C. for 4 hours so that the wavelength did not change in the actual vehicle environment.

After that, the periphery of the hologram element 1a is removed so that the seal width shown in FIG. 4 is 5 mm. MgF ₂ and T
A cover plate (112 mm × 46 mm × 1.0 mm) having a structure in which four layers of iO ₂ were alternately laminated and an antireflection film having a luminous reflectance of 0.3% was formed on the surface was prepared.
On the other hand, a cover plate (1) having an anti-scattering film with a thickness of 10 μm formed by adding 5% of a black pigment (Glasslite 500 manufactured by Cashew) to an epoxy resin and mixing them
12 mm × 46 mm × 1.0 mm) was prepared. Epoxy thermosetting resin (made by Cemedine, trade name CS-23
40-5) of a sealant having a refractive index of 1.55 was applied to the surfaces of the two cover plates so as to have a thickness of 50 μm. Both cover plates were arranged on the substrate glass as shown in FIG. 1, and the substrate glass was sandwiched between both cover plates via a sealant.

The luminous reflectance was calculated by the following formula.

[0036]

[Equation 1] Y% is the luminous reflectance, λ is the wavelength of light (10 mm step),
S (λ) = 1 (flat light source), R (λ) is a spectral reflection spectrum, and y (λ) is a 1931 CIE col-or mat.
Indicates a ching function.

Example 2 The same as Example 1 except that the recording of the subject on the photosensitizer was carried out by the method shown in FIG.

Here, the method of FIG. 11 will be described. In FIG. 11, an antireflection film 5 is formed on the surface of the substrate glass 2 on the opposite side to which the hologram element 1a is provided, and a concave lens 16 for copying is provided on the hologram element 1a side via silicon oil as a refractive index adjusting liquid. The arrangement is such that two incidence angles θ of the argon laser light, 20 ° and 39 °, are selected and incident.

Example 3 The same as Example 1 except that the antireflection film was not formed. Example 4 The same as Example 1 except that the anti-scattering film was not formed.

Example 5 The same as Example 1 except that a sealant made of an epoxy thermosetting resin having a refractive index of 1.41 was used.

Regarding Examples 1 to 5 described above, the normal image brightness of 3000 cd / m ^{2 was obtained with} the head-up display configuration of FIG.
The noise image brightness at the time of was measured (the display distance was 1.9 m
And the noise rate (see below). The noise image brightness was measured at the highest brightness other than the normal image.
The hologram characteristics at this time were as shown in FIG.

[0042]

[Equation 2] From the above results, as shown in FIG. 7, in Example 1, the noise ratio was small and the displayed image was beautiful. Thus, it can be understood that the hologram of Example 1 has extremely small noise during reproduction and recording. Also in terms of environmental resistance, by setting the seal width to 5 mm, 65 ° C and 9
The hologram element did not disappear even when left for 1000 hours in an atmosphere of 5% RH.

[Brief description of drawings]

FIG. 1 is a sectional view of a hologram.

FIG. 2 is a plan view of FIG.

FIG. 3 is a schematic diagram showing a schematic configuration of a head-up display.

FIG. 4 is a schematic diagram showing the vehicle-mounted layout of FIG.

FIG. 5 is a cross-sectional view showing a method of manufacturing a hologram.

FIG. 6 is a graph showing hologram characteristics in the example.

FIG. 7 is a graph showing a noise ratio in an example.

FIG. 8 is a sectional view showing another example of a hologram.

FIG. 9 is a sectional view showing another example of a hologram.

FIG. 10 is a cross-sectional view showing another example of a hologram.

FIG. 11 is a cross-sectional view showing a method of manufacturing a hologram as a comparative example.

[Explanation of symbols]

 1 Hologram 2 Substrate glass 3 Cover plate 4 Cover plate 5 Antireflection film 6 Scattering absorption film 7 Sealant

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Mizutani, 1-1, Showa-machi, Kariya city, Aichi Prefecture, Nihon Denso Co., Ltd. (72) Inventor, Tetsuya Kato, 1-1, Showa-cho, Kariya city, Aichi prefecture Within the corporation

Claims (17)

[Claims] 1. An optically transparent substrate having one surface and the other surface facing each other, and a hologram element having an interference fringe as a recording medium recorded on the one surface of the substrate. And the one surface and the other surface facing each other, which are provided on the one surface side of the substrate on which the hologram element is formed, and the light incident from the other surface side of the substrate passes through the hologram element. However, when reflection of light occurs at the boundary surface between one surface of the member and the atmosphere, it is composed of an optically transparent member configured so that the reflection of the light does not enter the hologram element again. Characteristic hologram. 2. The hologram according to claim 1, wherein the first member has an anti-scattering film on the one surface in contact with the atmosphere. 3. The hologram according to claim 2, wherein the anti-scattering film is a film capable of absorbing light by adding a desired pigment to a binder made of synthetic resin. 4. Between the substrate and the first member,
The hologram according to claim 1, wherein the hologram element is interposed and the substrate and the first member are adhered to each other with a sealant. 5. The hologram according to claim 4, wherein the sealing agent is made of at least one of an ultraviolet curable organic resin and a thermosetting organic resin. 6. An optically transparent substrate having one surface and the other surface facing each other, and a hologram element provided on the one surface of the substrate and recording interference fringes as a recording medium. And the light incident on the other surface side of the substrate from the other surface side of the substrate is reflected light at the boundary surface between the other surface of the substrate and the atmosphere is reproduction light of the hologram element. And an optically transparent first reflection control layer that does not face the same direction, and one surface and the other surface that face each other, and the one surface side on which the hologram element of the substrate is formed. When the light incident from the other surface side of the substrate is transmitted through the hologram element and the light is reflected at the boundary surface between the one surface of the member and the atmosphere, the reflection of the light is again performed. Holog A hologram comprising a member having a second reflection control layer that prevents the light from entering the Ram element. 7. The hologram according to claim 6, wherein an antireflection film is provided on the other surface side of the first member which is in contact with the atmosphere. 8. The antireflection film is formed of MgF ₂ , Ti.
The hologram according to claim 7, which is composed of at least one of O ₂ , ZrO _2, and SiO. 9. The substrate and the second member are bonded by a sealant.
The hologram described. 10. The hologram according to claim 9, wherein the sealant is made of at least one of an ultraviolet curable organic resin and a thermosetting organic resin. 11. An optically transparent substrate having one surface and the other surface facing each other, and a hologram element having an interference fringe recorded as a recording medium recorded on the one surface of the substrate. And the one surface and the other surface facing each other, which are provided on the one surface side of the substrate on which the hologram element is formed, and the light incident from the other surface side of the substrate passes through the hologram element. However, when light is reflected at the boundary surface between one surface of the member and the atmosphere, the optically transparent first member configured so that the reflected light does not enter the hologram element again, It is provided with one surface and the other surface facing each other, and one surface is provided so as to face the other surface side of the substrate, and the light incident from the other surface side of the member is Holograms, characterized in that and a second member that reflection of light at the interface between the other surface and the atmosphere of the member is configured to not suitable in the same direction as the reproduction light of the hologram element. 12. A hologram according to claim 11, further comprising an anti-scattering film on the surface of the one surface of the first member which is in contact with the atmosphere. 13. The hologram according to claim 11, wherein an antireflection film is provided on the other surface side of the second member which is in contact with the atmosphere. 14. The hologram according to claim 11, wherein the substrate and the first member and the substrate and the second member are adhered to each other with a sealant. 15. The hologram according to claim 14, wherein the sealing agent is made of at least one of an ultraviolet curable organic resin and a thermosetting organic resin. 16. The interference fringe is composed of two interference fringes having different pitches.
The hologram described in. 17. The antireflection film is provided after the hologram element is exposed.
The hologram described.