JP2898912B2 - Hologram recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus which is very suitable for recording and reproducing holograms.

[0002]

2. Description of the Related Art Holography has been applied to interference measurement, optical information processing, optical elements, three-dimensional displays, etc. as a complete wavefront reproduction technique. In order to perform hologram recording and hologram interference, a silver halide photosensitive material is generally used. However, since a silver halide photosensitive material requires development processing, a real-time hologram cannot be realized. On the other hand, single crystals (photorefractive crystals) having a light-induced refraction effect, such as Bi ₁₂ SiO ₂₀ single crystals, have been studied as real-time hologram (RH) elements (for example, “Laser Science Research Report”).
1990, Mar. See pages 1-9, "About the holographic recording characteristics of BSO single crystals." In this document, object light and reference light are made incident on the (110) plane of the crystal orientation of the Bi ₁₂ SiO ₂ single crystal, electrodes are attached to both end faces of the (110) plane, and a number An electric field of kV / cm is applied.

[0003] Regarding the dimensions of the hologram, interference measurement,
In each application of optical information processing and optical elements, although there are restrictions depending on the purpose of use, an element having a large size is not necessarily required. However, in three-dimensional display applications, which are expected to be put to practical use recently, it is absolutely necessary to increase the dimensions of the hologram element to a certain extent or more. This is because in a three-dimensional display application, it is necessary to utilize the binocular parallax of a person in order to enable the three-dimensional recognition of the person. For this purpose, the dimension of the hologram element is set to a distance between both eyes (about 50 mm). That is because it must be at least.

However, the upper limit of the size of the real-time hologram element is Bi _{1 2} which is a recording member for recording interference fringes.
It was physically limited by the shape and dimensions of the SiO _{2 O} single crystal, and specifically, it was at most a dozen mm × a dozen mm. Because of this dimensional limitation, the use of real-time hologram elements is currently limited to only interferometry and optical information processing. However, the real-time hologram is a technology that is strongly desired to be put to practical use in the future. Specifically, application as an output device of a three-dimensional image display system such as a three-dimensional CAD system is expected. Therefore, it is strongly desired to increase the size of the real-time hologram element.

[0005]

The present inventor has been studying to develop a large-sized hologram element applicable to such a three-dimensional display, but encountered the following problems in the course of this research. . That is, when recording the interference fringes by irradiating the object light to the flat recording portion made of the optical single crystal, the diffraction efficiency was reduced due to reflection on the surface of the recording portion. In addition, the reconstructed image is observed by directing both eyes to the hologram recording element and irradiating the recording portion with the reconstructed light from the opposite side of the both eyes. Since the image is brightly reflected on the surface of the element and is reflected, it may be difficult to observe the reproduced image. Further, the present inventor has considered that the flat plate-shaped element is inclined at a predetermined angle from an angle perpendicular to the reproduction light as described later, but in this process, only the reflection of the object light on the surface of the element is considered. Instead, the diffraction efficiency was significantly reduced due to refraction of the object light.

It is an object of the present invention to provide a novel hologram recording / reproducing apparatus which can prevent a reduction in diffraction efficiency and a disturbance of a reproduced image due to reflection and refraction on the surface of the hologram recording element.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a recording section made of an optical single crystal exhibiting a photo-induced refraction effect, and an electrode for applying a voltage to the recording section. A hologram recording element comprising: an insulating transparent medium in contact with an element surface through which recording / reproducing light of the hologram recording element passes, wherein the difference between the refractive index and the refractive index of the optical single crystal is 0.50 or less. A hologram recording / reproducing apparatus, characterized by having a medium which is located on the side opposite to the element side of the medium and having a light-transmitting partition wall in contact with the medium.

The present invention provides a conceptually completely new hologram recording / reproducing apparatus in which the hologram recording / reproducing element itself is accommodated in an insulating medium having a refractive index relatively close to the hologram recording / reproducing element. Accordingly, a change in light intensity and speed on the surface of the optical single crystal constituting the recording portion of the hologram recording / reproducing element, that is, a change in light energy state can be minimized.

[0009] Particularly preferably, the hologram recording / reproducing element can be accommodated in a medium having insulating properties and fluidity. In this case, the medium can be filled or contained in the container.

[0010] Here, the medium has insulating properties by 1k
This means that no discharge occurs for an applied voltage of V / mm. Further, that the medium has fluidity means that the injected medium can be filled in the container without generating bubbles or voids. Further, that the medium is transparent means that remarkable absorption and scattering do not occur in the used wavelength band.

In order to make the effect of the hologram recording / reproducing apparatus of the present invention more remarkable, the difference in the refractive index between the medium and the recording section is preferably 0.5 or less, and more preferably 0.1 or less. More preferred. Further, it is particularly preferable to make the difference between the two refractive indexes substantially the same.

The type of medium that can be specifically used depends on the combination with the refractive index of the recording section, but a refraction liquid composed of the following materials can be preferably used. Silicon-based oil, arsenic tripromide, disulfide / selenium compounds, formulations containing selenium compounds, arsenic tripromide / disulfide-based formulations, etc.

Such a refraction liquid has a refractive index of 1.30.
Although those having about 0 to 2.31 are available,
When it is formed of a birefringent single crystal as described later, it is usually preferable that the refractive index is in the range of 1.9 to 2.31. From this point of view, Cargille standard refraction fluids available from Moritex, Inc.
H "," Series EH "and" Series FH "are particularly preferred. This “Series H” is an arsenic tripromide / disulfide-based formulation, and “Series H”
“EH” is a formulation containing a selenium compound, and “Series FH” is a arsenic tribromide / disulfide / selenium compound-based formulation.

In the present invention, the refraction liquid may be solidified or gelled after the refraction liquid is contained between the partition walls or in a container. This makes it easier to handle the device of the present invention.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be sequentially described. Examples of the optical single crystal having the photo-induced refraction effect include Bi ₁₂ SiO ₂₀ single crystal and Bi ₁₂ Ge
O _{2 0} single crystal, but LiNbO ₃ single crystal or the like is preferred, the sensitivity of the out light induced effect is greater Bi _{1 2} SiO _{2 0} monocrystalline particularly preferred. Either a transparent electrode or an opaque electrode can be used as an electrode formed in each recording section. Examples of the material of the transparent electrode include a tin oxide film and an indium tin oxide film. Also,
As the material of the opaque electrode, called a metal paste,
Examples thereof include a conductive adhesive containing a conductive material such as silver powder, and a metal film such as aluminum, gold, chromium, and titanium.

The object light and the reference light that can be used in the hologram recording / reproducing apparatus are not particularly limited. At present, argon ion laser light having a wavelength of 488 nm, which shows a photoconductive effect of a Bi ₁₂ SiO ₂₀ single crystal, is preferable. use can, as a reproduction light, Bi _{1 2} SiO _{2 0} single crystal a helium-neon laser light having a wavelength of 633nm which does not exhibit photoconductivity effect can be preferably used.

FIGS. 1 (a) and 1 (b) are cross-sectional views schematically showing a hologram recording / reproducing apparatus according to an embodiment of the present invention, and FIG. 1 (c) is a sectional view of FIG. 1 (b). It is a top view which shows a hologram recording / reproducing apparatus. FIG. 2 (a), (b)
FIG. 3 is a schematic diagram for explaining a problem when a three-dimensional display is manufactured using a conventional hologram recording / reproducing apparatus. FIG. 3 is a perspective view showing the hologram recording / reproducing apparatus studied by the present inventors. It is.

The inventor has manufactured a hologram recording / reproducing element using a so-called (110) wafer. B
The i ₁₂ SiO ₂₀ single crystal belongs to the cubic system, and <1
The 00> axis, the <010> axis, and the <001> axis are equivalent.
At present, (11)
0) A recording unit is cut out from a wafer. In order to form a three-dimensional display using this element, as shown in FIG.
Is housed in the dark box 9, and the element 4 is attached to the edge of the dark box 9. Then, the reproduction light 11 is irradiated in a direction substantially perpendicular to the (110) plane of the element 4 to obtain a reproduction image. Optical system 1
An observer 8 on the side opposite to 0 observes this reproduced image.
The line of sight 7 of the observer 8 is (11
0) The direction is perpendicular to the plane.

The optical system 10 is housed in the dark box 9 in order to prevent extra light from irradiating the element 4. Also, in a three-dimensional display, as shown in FIG. 2, it is necessary to observe a reproduced image from the outside.
The body of the element 4 needs to be exposed outside the dark box.

A laser light source is used as a light source for object light for writing interference fringes on the element 4 and for reproducing light. However, there is an upper limit to the amount of laser light, and it is not possible to increase the brightness without limit. In particular, it is necessary to use a laser light source that is as small as possible in order to prevent the entire apparatus from becoming large. Therefore, there is a limit to the brightness of the reproduced image. on the other hand,
When used as a stereoscopic display element, preferably, as schematically shown in FIG. 2B, it can be used even in an environment where the observer 8 is under normal bright indoor lighting 12. Want to.

However, the light directly radiated from the indoor lighting 12 and the reflected light 13 from the indoor object are radiated to the surface of the element 4 and reflected there, so that the reflected light 14 is observed. Will be. On the other hand, the reproduced image advances toward the observer as indicated by arrow 15. For this reason, a reflected image such as indoor lighting appears to be superimposed on the three-dimensional reproduced image as it is. Then, while the brightness of the laser light in the dark box is limited, the room illumination is relatively bright, so that the reflected image reflected on the surface of the element 4 becomes brighter than the reproduced image. It has been found to interfere with the observation of the image.

The inventor studied an element as shown in FIG. 3 in order to prevent reflection on the surface of the element 4. Here, the recording portion 5 of the element 4 has a rectangular flat plate shape, and electrodes 18 are formed on a pair of end surfaces of the recording portion 5, and each electrode 18 is connected to a DC power supply 16 by an electric wire 17. Have been. Here, a transparent antireflection film 19 is formed so as to cover the main surface of the recording unit 5 on the viewer 8 side.
I tried to form. Such an antireflection film 19 is generally formed of a dielectric film, and the resistivity of such a film is at most about 10 ⁹ Ω · cm. On the other hand, the resistivity of the recording portion is usually about 10 ¹⁴ Ω · cm, and the resistivity of the antireflection film is relatively relatively low. When a hologram is recorded or reproduced, a high voltage is applied to the element. Therefore, it has been found that the antireflection film 19 prevents application of a predetermined voltage or causes dielectric breakdown.

In the present invention, the reflection on the surface of such an element can be significantly reduced, and the change in the refractive index can be minimized. By utilizing this, it is possible to minimize a reflection image of an external scenery or the like that overlaps with the reproduced image of the hologram even under bright illumination or sometimes even outdoors.

More specifically, in each of the hologram recording / reproducing apparatuses 1A and 1B shown in FIGS. 1A to 1C, for example, a transparent material having insulating properties and fluidity is placed in a rectangular parallelepiped container 2 respectively. A medium 3 is accommodated therein, and a hologram recording / reproducing element 4 is accommodated in the medium 3. In this element 4, the main surface of the recording section 5 is (11)
The electrodes 18 are respectively formed on a pair of (001) surfaces of the recording unit 5, and these electrodes 18 are connected to the DC power supply 16. The reproduction light 11 enters the (110) plane of the recording unit 5. Of course, the shape of the container 2 is not particularly limited.

The reproduction light sequentially passes through the wall surfaces 2d, 2c, 2b, and 2a of the container 2 from the light source side of the reproduction light toward the observer. In the apparatus shown in FIG. 1A, an antireflection film 6A is formed on the inner wall surface 2b on the observer side. In the apparatus shown in FIG. 1B, the observer is further provided in addition to the antireflection film 6A. Anti-reflection film 6 on outer side wall 2a
B is formed. Here, in the apparatus of the present invention, the difference in the refractive index between the medium 3 and the container 2 is usually relatively large, and the difference in the refractive index between the container 2 and the atmosphere is relatively small. In addition, the reflection on the wall surface on the observer side was more affected by the reflected light from the scenery outside the apparatus.
Therefore, it is most effective to form an antireflection film on the inner wall surface 2b on the observer side, and it is particularly effective to form an antireflection film on the outer wall surface 2a on the observer side. However, it is possible to further form an antireflection film on the inner wall surface 2c and the outer wall surface 2d on the light source side of the reproduction light,
Even more preferred.

According to these embodiments, not only can the reflection on the surface of the element be minimized, but also the disturbance of the reproduced image caused by the reflection on the wall surface of the container is prevented by the antireflection films 6A and 6B on the wall surface of the container. It is particularly preferable because it can be effectively prevented. Moreover, none of these antireflection films are formed directly on the element.
Since it is formed on the wall of the container 2, the voltage from the DC power supply is insulated by the medium 3 and is not applied to these antireflection films. Therefore, there is no difficulty in controlling the applied voltage or dielectric breakdown caused by the anti-reflection film as described above.

As the material of the container for accommodating the medium, a transparent, easily polished and striae-free material such as optical quartz glass is preferable. Further, the difference between the refractive index of the medium and the refractive index of the container is preferably 1.0 or less, more preferably 0.5 or less. Examples of the material of the antireflection film include SiO ₂ , TiO ₂ , and ZrO ₂ . These can be similarly applied to the following embodiments.

FIG. 4 is a sectional view schematically showing a hologram recording / reproducing apparatus 1C according to another embodiment of the present invention.
This device is also attached to the outer edge of the dark box 9. The medium 3 is accommodated in the container 20, and in the medium 3,
The hologram recording / reproducing element 4 is accommodated. In the element 4, the main surface of the recording section 5 is the (110) plane,
Electrodes 18 are respectively formed on a pair of end surfaces of the recording unit 5. The reproduction light 11 emitted from the optical system in the dark box 9 is
Outer wall surface 20d on the optical system side of container 20, inner wall surface 20c
, The recording portion 5, and the inner wall surfaces 20b and 20a on the observer side sequentially.

Here, in the present example, the peripheral wall 21 of the container 20 on the observer side has a predetermined angle with respect to a plane perpendicular to the optical axis of the reproduction light (with respect to the (110) plane of the recording unit 5). It is inclined by α. At the same time, the wall surfaces 20a and 20b
A light-shielding plate 22 is installed at a position facing the light source, for example, so as to extend in a direction parallel to the reproduction light. Thus, since the reflected light 50 from the outside, which should travel in the direction of the observer, is blocked by the light shielding plate 22, it is possible to prevent the reproduced image from being disturbed by the reflected image from the outside. This shading plate,
It is preferable to use a non-glossy material. FIG.
Also in the device of the above, the wall surfaces 20a, 20b, 20c, 20
An antireflection film can be formed on each of d.

It is particularly preferable that α is 30 to 60 °. By setting α to 30 ° or more, the effect of preventing reflection can be remarkable. Also, α
Increases, the length of the light-shielding plate needs to be increased accordingly, and the size of the element increases.
Is set to 60 ° or less, a relatively compact and small element can be provided.

In the element described above, the recording unit 5
The object light and the reproduction light are made to enter in a direction perpendicular to the (110) plane, and a voltage is applied in the <01-1> direction. It is known that this provides the highest diffraction efficiency. However, such a hologram recording / reproducing element has the following problems mainly from the viewpoint of manufacturing.

As an optical single crystal for a hologram recording / reproducing element, bismuth silicate and bismuth germanate are considered to be particularly suitable, but these single crystals are usually prepared by a pulling method (Czochralski method). Have been. At this time, as shown in FIG. 5 (a), the boule 24, which is usually a columnar single crystal, is pulled up from the melt, and the direction of the pulling axis of this boule is the <100> direction. When cutting the (110) wafer 25 from this boule, the wafer 25 is cut in the vertical direction so that the main surface of the wafer 25 has the <011> orientation. This boule currently has a diameter of 80
mm and a length of about 100 mm are obtained.

As described above, depending on the cutting direction,
It is possible to cut out a large-sized wafer having an orientation with the highest diffraction efficiency. However, in order to cut a wafer 25 having a form as shown in FIG.
It is necessary to perform a complicated cutting process. In addition, the number of wafers of a predetermined size that can be cut out from one boule was very small, and the remaining material remaining after cutting was large.

Therefore, the present inventor has developed a novel hologram element having a form as shown in FIG. The manufacturing process of this element and the hologram recording / reproducing method will be sequentially described. As shown in FIG. 5B, after the column-shaped boule 24 is manufactured, the boule is pulled up, that is, in the direction perpendicular to the crystal orientation of <100>.
By cutting the boule 24, a disk-shaped wafer 26 is cut out. The main surface of the wafer 26 is (100)
Plane. Since the original boule shape can be used as it is, the cutting step for cutting out the wafer 26 is very simple and the number of steps is small. Also,
Since the residual material remaining after cutting is extremely small, it is extremely advantageous in manufacturing.

As shown in FIGS. 6 (a) and 6 (b), the present inventor manufactured each element by using a disk-shaped wafer 26 cut out from a boule as a recording unit as it is. The main surface 26a of the recording unit 26 is a (100) plane. In the elements 27A and 27B shown in FIGS. 6A and 6B, a pair of electrodes 2 are provided on the outer peripheral surface 26b of the recording unit 26, respectively.
8A and 28B are formed. Each electrode 28A and 28B
Are formed symmetrically with respect to the center of the recording unit 26 so as to face each other. However, in the element 27A, each electrode is formed in a fan shape so as to be symmetric about the <010> axis.
In the element 27B, each electrode is formed in a fan shape so as to be symmetric about the <011> direction. The angle of each electrode when viewed from the center of the circular recording unit 26 is
2β.

The relationship between the incident light and the optical axis when such an element was used was also examined. These (100)
When a wafer or a recording section cut out from the wafer is used as a hologram recording / reproducing element, the main surface of the recording section becomes the (100) plane, but even if object light or reproduction light is incident on the (100) plane, Since no photorefractive effect can be obtained, it has been considered that it cannot be used for hologram applications. However, the inventor of FIG.
As shown in (a) and (b), the degree of the photorefractive effect obtained when the recording unit is inclined with respect to the object light or the like and an electric field is applied was examined for the first time. Here, the optical axis of the incident light 30 is inclined by θ with respect to the <100> direction, and the direction of the electric field E is inclined by φ with respect to a plane formed by the <100> direction and <001>. .

In this state, when the inclination angle θ between the optical axis of the incident light and the (100) direction is changed, for example, as shown in the graph of FIG. 8, the diffraction efficiency (arbitrary unit) significantly changes. confirmed. Here, the diffraction efficiency is such that θ is 30 to 60.
° in the range of 40 ° to 50 °. In order to obtain a bright reproduced image, it has been found that it is necessary to maximize the diffraction efficiency, and for this purpose, it is necessary to set the above-mentioned predetermined inclination angle θ.

Further, the present inventor has proposed that the recording section has the form
As shown in FIG. 6, the present inventors have conceived of using a disk-shaped wafer as it is. This makes it possible to provide an element that is particularly suitable for a real-time hologram. This is because, in the real-time hologram element, it is necessary to increase the width of the recording part in order to utilize binocular parallax.However, when a rectangular recording part is cut out from a circular wafer, the outer peripheral part of the circular wafer is greatly reduced. This is because the width of the recording portion is significantly reduced because it is necessary to cut off the recording portion.

However, in the conventional hologram recording / reproducing element, a rectangular recording portion is used, and by forming parallel plate electrodes on opposite end faces of the recording portion, the electric field inside the crystal is reduced. I try to make it even. However, even if the electrodes are formed on the outer peripheral portion of the circular wafer, the distribution of the electric field inside the wafer is unlikely to be uniform, and it is considered that the diffraction efficiency becomes non-uniform. However, the present inventor has performed a simulation by a computer and a measurement test of an actual diffraction efficiency. As a result, by forming a pair of electrodes in a form as shown in FIG. Uniform and
It has been found that variations in diffraction efficiency inside the crystal can be significantly reduced.

However, the present inventor has further found the following problem. In other words, from the above examination results,
As schematically shown in FIG. 9, it was necessary to install the element 27A (27B) with the <100> direction (normal 31) inclined with respect to the optical axis 30. This inclination angle is defined as γ. However, while the refractive index of the atmosphere is usually 1.0, the refractive index of the optical single crystal constituting the hologram recording / reproducing element is usually 2.4 to 2.6. Are very different. For this reason, the incident light 30 is refracted, propagates through the recording portion of the element as 32, and emerges again as 33 from the other main surface 26a. The incident light 30 and the outgoing light 33 are parallel to each other.

The upper limit of θ is only 0 ° to 25 ° due to the difference in refractive index described above. As described above, since the angle between the light actually incident on the crystal and the <100> direction of the crystal is small, even if the incident angle γ is set to around 45 °, the diffraction efficiency decreases, and in particular, the real-time hologram Is not practical for use in three-dimensional displays.

Therefore, the present inventor has conceived a technique of including a device using a (100) wafer in a medium according to the present invention. FIG. 10A is a cross-sectional view schematically showing a device 32A according to the embodiment of the present invention.
(B) is a plan view of this device. For example, a transparent medium 3 having insulating properties and fluidity is accommodated in a rectangular parallelepiped container 2, and a hologram recording / reproducing element 27A (27B) is accommodated in the medium 3. Each electrode 2
8A and 28B are connected to the DC power supply 16, respectively. The incident light 30 is incident on the (100) plane of the recording unit 5. At this time, the angle γ between the normal 31 of the main surface 26 a and the optical axis of the incident light 30 is preferably set to 30 to 60 °. Set.

When the incident light 30 is a reproduction light, the reproduction light is applied to the walls 2 d and 2 c of the container 2, the recording section 26, and the wall 2.
b and 2a are sequentially transmitted. At this time, by making the difference in the refractive index between the medium 3 and the recording section 26 small, and particularly preferably substantially the same, the angle of refraction of the incident light 30 on the surface of the recording section 26 becomes extremely small. The difference between γ and the angle θ of the optical axis in the crystal with respect to the <100> orientation of the crystal can be significantly reduced. As a result, the diffraction efficiency of the optical single crystal was significantly increased.

FIGS. 11A and 11B are cross-sectional views schematically showing hologram recording / reproducing devices 32B and 32C, respectively. The same members as those shown in FIG. 10 are denoted by the same reference numerals, and description thereof will be omitted. In the hologram recording / reproducing device 32B shown in FIG. 11A, an antireflection film 6A is formed on the inner wall surface 2b of the container 2 on the viewer side. In the device 32C of FIG. 11B, an antireflection film 6B is further formed on the outer wall surface 2a of the container 2 on the viewer side.

FIG. 12 is a sectional view schematically showing a hologram recording / reproducing apparatus 32D according to still another embodiment of the present invention. This device is also attached to the outer edge of the dark box 9. The medium 3 is contained in the container 20, and the medium 3
In the hologram recording / reproducing element 27A (27
B) is accommodated. The reproduction light 30 emitted from the optical system in the dark box 9 is applied to the outer wall surface 20 d on the optical system side of the container 20,
The light passes through the inner wall surface 20c, the recording unit 26, and the inner wall surfaces 20b and 20a on the observer side sequentially.

Here, in the present embodiment, the peripheral wall 21 of the container 20 on the observer side is inclined by a predetermined angle α with respect to the normal line of the reproduction light 30. At the same time, a light shielding plate 22 is installed at a position facing the wall surfaces 20a and 20b so as to extend, for example, in a direction parallel to the reproduction light. by this,
Since the reflected light 50 from the outside, which should travel in the direction of the observer, is blocked by the light shielding plate 22, it is possible to prevent the reproduced image from being disturbed by the reflected image from the outside. It is preferable to use a light-shielding plate having no gloss. In the apparatus of FIG. 12, the wall surfaces 20a, 20b, 2
An anti-reflection film can be formed on each of 0c and 20d.

[0047]

[Example 1]

(Manufacture of hologram recording / reproducing device) First, diameter 80m
A boule of Bi ₁₂ SiO ₂₀ single crystal having a length of 100 mm and a length of 100 mm was manufactured. As the crucible, a cylindrical platinum crucible having a diameter of 150 mm and a height of 150 mm was used. In a crucible, 14 kg of a sintered body of Bi ₁₂ SiO ₂₀ was accommodated and heated to 900 ° C. to generate a melt. By using a platinum afterheater, the temperature gradient up to 10 mm above the lifting direction of the boule is adjusted to 50-75 ° C./cm, followed by 15 ° C.
The temperature gradient up to 0 mm was adjusted to 10 ° C./cm. The lifting speed was 1 to 1.5 mm / hour, and the rotation speed of the lifting shaft was 10 rpm. The properties of the obtained single crystal are shown in Table 1 below.

[0048]

Table 1 Lattice constant 10.103 × 10 ⁻¹⁰ m Density 9.2 g / cm ³ Dielectric constant 56 (100 kHz) Refractive index 2.53 (λ = 633 nm) 2.3 (λ = 850 nm) Dark resistance 10 ¹⁴ Ω · cm Photoconductivity 10 ⁸ Ω / cm (λ = 458 nm, 2.5 mW / cm ² ) Half-wave voltage 3900 V (λ = 633 nm) Verde constant 3.67 × 10 ⁻³ / Oe · cm (λ = 633 nm) ^{9.33 × 10 - 4 / Oe ·} cm (λ = 1150nm)

The recording section 5 was cut out from the boule 1 as shown in FIG. The dimensions of the recording section 5 were 50 mm × 50 mm × 3 mm. The pair of main surfaces of the recording unit 5 are polished by a plane polisher, and the flatness thereof is set to 0.
The thickness was 6 μm. Next, a transparent electrode film 18 made of indium tin oxide and having a thickness of 1000 angstroms was formed on each end face by a vacuum vapor deposition method, and an element 5 was produced.

An arsenic tripromide / disulfide / selenium compound is contained as a medium 3 in a container 2 made of synthetic quartz, and the element 5 is fixed in the medium 3 as shown in FIGS. 1 (a) and 1 (b). An apparatus as shown was prepared.

(Measurement of diffraction efficiency)
A voltage of kV was applied. The device was irradiated with two argon ion laser beams crossing at a crossing angle of 3 ° as object light. The wavelength of each laser beam was 488 nm, and the beam diameter was 100 mm. 100 elements / m on the element 5
Interference fringes having a fringe interval of m were formed and recorded in the device.
The energy of the irradiated laser beam was 4 mJ / cm ² .

With respect to the interference fringes recorded in the element in this manner, at an incident angle satisfying the Bragg diffraction condition, a wavelength of 63
A 3 nm helium-neon laser beam was irradiated to the light irradiation surface to obtain a first-order diffracted light. Here, Bi ₁₂ SiO
_{Since the 20} single-crystal hologram is a thick volume hologram, the angle selectivity of the incident light for reproduction is strict, and diffraction does not occur unless the light is incident in a direction satisfying the Bragg condition. As a result, the ratio of the intensity of the first-order diffracted light to the incident light (diffraction efficiency) was 0.7%.

(Hologram Recording and Reproduction Experiment) FIG.
Using the optical system schematically shown in FIG. 3, hologram recording and reproduction experiments were performed by the hologram recording and reproduction apparatus 1A or 1B. The above device 34 was installed at a predetermined position. An argon ion laser beam having a wavelength of 488 nm was emitted from the light source 38, and the laser beam was split into two by a half mirror 39. One of the divided laser beams passes through the lens 41 and the diffusion plate 42, is scattered by the diffusion plate 42, and has a size of 50 mm × 5 on which the original image is printed.
It passes through a 0 mm transparent film 43. This film 4
The light emitted from No. 3 was used as object light, which was irradiated to the element.

On the other hand, of the argon ion laser light, the light that has passed through the half mirror 39 is reflected by the mirror 40, passes through the condenser lens 44 and the collimating lens 45, and is irradiated as reference light onto the light irradiation surface. The object light and the reference light cross each other at a cross angle of 3 °. As a result, an original image could be recorded in the element. The irradiated light energy was 4 mJ / cm ² .

Next, when the wavelength is 633 mm and the diameter is 1
Helium-neon laser light having a uniform light amount distribution of 00 mm was emitted from the light source 35, passed through the condenser lens 36 and the collimator lens 37, and made incident on the light irradiation surface of the element. The incident angle of the laser beam was an incident angle that satisfies the Bragg diffraction condition with respect to the interference fringes recorded in the element.

When this reproduced image was observed in a room having a brightness of 100 lux, the reproduced image was reproduced at a position corresponding to the original image, whereby the depth of the original image was reproduced also in the reproduced holography. I knew it was. Then, the depth of the holography could be confirmed using binocular parallax. As described above, according to the present invention, it is possible to faithfully reproduce and confirm the depth and stereoscopic effect of an original image using binocular parallax.
Succeeded in providing a dimensional display. Moreover,
Almost no disturbance of the reconstructed image due to the surrounding scenery was observed.

The image recorded in the element in this manner is erased by irradiating uniform blue light over the entire light irradiation surface of the element with the voltage applied to the element being 0 V. I was able to.

(Experiment 2) An apparatus 1C shown in FIG. 4 was manufactured. However, the method of manufacturing the materials of the element 5, the container 2, and the medium 3 was the same as that in Experiment 1. In addition, a black nonwoven fabric was used as a light shielding plate. The angle α was 45 °. Under these conditions, when the diffraction efficiency was measured in the same manner as in Experiment 1,
0.7%. Also, in the recording and reproduction experiments of the hologram image, the same results as in Experiment 1 were obtained.

[0059]

As described above, according to the hologram recording / reproducing apparatus of the novel form of the present invention, in the hologram recording element, a reduction in diffraction efficiency and a disturbance of a reproduced image due to reflection and refraction on the surface of the element are prevented. Can be prevented.

[Brief description of the drawings]

FIGS. 1A and 1B are cross-sectional views schematically showing a hologram recording / reproducing apparatus according to an embodiment of the present invention, and FIG. 1C is a hologram recording / reproducing apparatus shown in FIG. It is a top view which shows an apparatus.

FIGS. 2A and 2B are schematic diagrams for explaining a problem when a three-dimensional display is manufactured using a conventional hologram recording / reproducing apparatus.

FIG. 3 is a perspective view showing a hologram recording / reproducing apparatus studied by the present inventors.

FIG. 4 is a sectional view schematically showing a state in which a hologram recording / reproducing apparatus according to another embodiment of the present invention is mounted on a dark box 9.

FIG. 5A is a perspective view showing a state in which a (011) wafer 25 is cut out from a single crystal boule 24;
(B) Single crystal boule 24 to (100) wafer 2
FIG. 6 is a perspective view showing a state in which 6 is cut out.

FIGS. 6A and 6B are plan views each showing a hologram recording / reproducing element used in another embodiment of the present invention.

FIGS. 7 (a) and (b) are FIGS. 6 (a) and 6 (b), respectively.
It is a schematic diagram for illustrating the direction of incidence of light when each element of (b) is used.

FIG. 8 shows an example of the relationship between the diffraction efficiency and the angle θ of the optical axis of the incident light with respect to the <100> direction of the optical single crystal when each of the elements shown in FIGS. 6A and 6B is used. It is a graph.

FIG. 9 is a front view for explaining the progress of light when the incident light is directly incident on the elements of FIGS. 6 (a) and 6 (b).

FIG. 10A is a cross-sectional view schematically showing a hologram recording / reproducing apparatus according to an embodiment of the present invention, which is manufactured using the elements of FIGS. 6A and 6B; ) Is (a)
It is a top view of the apparatus of FIG.

11 (a) and (b) are FIGS. 6 (a) and 6 (b), respectively.
It is sectional drawing which shows typically the hologram recording / reproducing apparatus which concerns on the Example of this invention produced using the element of (b).

FIG. 12 is a cross-sectional view schematically showing a hologram recording / reproducing apparatus according to an embodiment of the present invention, which is manufactured using the elements of FIGS. 6 (a) and 6 (b).

FIG. 13 is a schematic diagram showing an optical system used in a hologram recording / reproduction experiment.

[Explanation of symbols]

1A, 1B Hologram recording / reproducing device 2, 20
Container 2a, 20a Outside wall surface 2b, 20b on the viewer side
Inside wall surface 2c, 20c on the observer side Inside wall surface 2d, 2 on the light source side of the reproduction light
0d outer wall surface on the light source side of the reproduction light 3 medium 4
27A, 27B Hologram recording / reproducing element 5 Recording section 6A, 6B Antireflection film 7 Line of sight 8 Observer 9 Dark box 10 Optical system 12 Indoor lighting 18, 28A, 2
8B electrode 21 peripheral wall 24 columnar single crystal boule 24 25 (110) wafer 26 (100) wafer 30 incident light

Claims (5)

(57) [Claims] 1. A hologram recording device comprising: a recording portion made of an optical single crystal exhibiting a photo-induced refraction effect; and an electrode for applying a voltage to the recording portion. An insulating transparent medium that is in contact with the element surface passing therethrough, wherein a medium having a refractive index difference of 0.50 or less between the refractive index of the optical single crystal and a medium opposite to the element side of the medium; A hologram recording / reproducing apparatus having a light-transmitting partition wall in contact with a medium. 2. The optical single crystal is an optical single crystal selected from the group consisting of bismuth silicate and bismuth germanate, the crystal orientation of the incident surface of the incident light in the recording section is (100), and < 2. The hologram recording / reproducing apparatus according to claim 1, wherein the angle θ between the <100> axis and the optical axis of the incident light in the crystal is 30 ° to 60 °. 3. The hologram recording / reproducing apparatus according to claim 2, wherein said recording section has a disk shape, and said electrode is formed along an outer peripheral edge of said recording section. 4. An anti-reflection film is formed on at least one of the partition walls on the side from which reproduction light for reproducing a hologram is emitted. A hologram recording / reproducing apparatus according to claim 1. 5. The partition wall, at least on the side from which the reproduction light for reproducing the hologram is emitted, is inclined with respect to a plane perpendicular to the optical axis of the reproduction light, and the inclined wall is inclined. The hologram recording / reproducing apparatus according to any one of claims 1 to 3, wherein a light shielding plate is provided at a position facing the partition wall surface.