JP2000232661A - Holography television element and holography television receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a practical holography television element and a practical holography television receiver based on the reproduction principle of the phase modulation type L ippmann holograph. SOLUTION: The holography television receiver is provided with a holography television element 6 that has a transparent board 1 and very small optical elements 2 that are arranged in the form of a two dimensional matrix in the directions in parallel with and perpendicular to an incident plane 10 of the transparent board 10 and with a control section 3 that can individually control a control signal 11 applied to the optical elements 2. The transparent board 1 has a refractive index of 'n' with respect to an incident light 20 from the incident plane 10 and each optical element 2 has a refractive index of nearly 'n' with respect to the incident light 20. However, when the control signal 11 is applied to the optical elements 2 in the direction perpendicular to the incident light 20, the refractive index is modulated and a difference of the refractive index of the optical element 2 by 'Δn' is caused with respect to the refractive index of the transparent board 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a real-time holographic television for reproducing a three-dimensional image in real time,
In particular, the present invention relates to a holographic television using the reproduction principle of Lippman holography.

[0002]

2. Description of the Related Art Conventionally, in holographic television,
Reproduction of a three-dimensional moving image was realized using the transmission principle of a hologram.

FIG. 10 is a diagram showing the principle of a display unit (also referred to as a receiving unit or a reproducing unit) of a holographic television system which has been reported conventionally (“Sato, Higuchi, Katsuma:” using a liquid crystal display device). Basic Study of Holographic Television ", Journal of the Institute of Television Engineers of Japan, Vol. 45, No. 7, pp. 873-875, issued on July 20, 1991.

In this conventional holographic television system, a high-definition liquid crystal display panel 60 composed of pixels as high as light diffraction is transmitted from a transmission unit (or a generation unit by a computer) 62 to a transmission path 71 and a liquid crystal driving unit. A hologram 70, which is a striped pattern sent as a television picture signal (NTSC format) via 63, is displayed. By irradiating the high-definition liquid crystal display panel 60 on which the hologram 70 is displayed with interference from the laser light source 64, that is, by irradiating coherent illumination light 72 for reproduction, the observer 421 can observe a holographic stereoscopic moving image reproduced image.

[0005] Various inventions utilizing the above-described reproduction principle have been disclosed, and as an example, Japanese Patent Application Laid-Open No. 6-282213 has been disclosed.
FIG. 11 shows an application example disclosed in the official gazette.

As a display element of the high-definition liquid crystal display panel 60, a simple matrix liquid crystal display element 65 capable of driving pixels with a repetition cycle shorter than that of a normal TV frame, and capable of reducing the pixel size to the order of light diffraction is used. .

[0007] One normal video frame of a TV is about 30 Hz. For this reason, when the ordinary matrix pixel arrangement type liquid crystal element 61 shown in FIG. 10 is used as the high-definition liquid crystal display panel 60, when driving the last scanning line in one video frame, As a result, data written to the pixels is almost lost with the passage of time, so that a reproduced image is lost or lost. However, since the holographic television reproduces an image by using a light diffraction phenomenon by a pattern of all interference fringes displayed on the liquid crystal display panel surface, if a part of the displayed interference fringes disappears, it is correct. No image is obtained.

Therefore, in the application example shown in FIG. 11, the video data recorded in the video memory 66 can be reused by A / D-converting the television picture signal and recording it once in the video memory 66. It is like that. Since the video data written in the simple matrix liquid crystal display element 65 is rewritten in a cycle shorter than the erasing time of the video data, the video data is not lost, and thus the reproduced image is not lost or lost.

The above-mentioned hologram is two-dimensionally reproduced on a panel surface of a liquid crystal display panel using a television image signal, and belongs to a so-called transmission hologram as a type.

[0010]

However, since the principle of reproducing a transmission type hologram is used in a holographic television, there are the following problems.

The first problem is that the reproduced image is uncomfortable and requires familiarity. This is because observing a reproduced image with transmitted light from a holographic television is situationally different from observing an ordinary object.

The second problem is that the visual field is narrow and a reproduced image can be observed only from a certain direction. This is because the interference fringes displayed on the liquid crystal display panel surface are regarded as diffraction gratings, and the diffraction light generated when the illumination light for reproduction passes through the diffraction grating is observed as a virtual image.

A third problem is that the reproduced image is darker than the brightness of the liquid crystal display panel. This is because the diffracted light used for observing the virtual image is only a small part of the energy of the illumination light for reproduction, and most of the remaining energy is wasted.

A fourth problem is that since a laser beam is used as illumination light for reproduction, it is difficult to colorize a reproduced image. This is because a coherent light beam is required as illumination light for reproduction. Because the laser beam is monochromatic, colorization involves technical and cost difficulties.

The fourth problem is that the hologram to be transmitted is changed to a transmission type image hologram or a rainbow hologram, and the illumination light for reproduction is changed from laser light to white illumination light, so that a color reproduction image is reproduced. Observation becomes possible.
Although this solution cannot be read from the principle diagram of the display unit of the holographic television system of FIG. 2, it is within a range that can be inferred.

As described above, the transmission hologram has several problems.

By the way, the types of holograms are roughly classified into the above-mentioned transmission holograms and reflection holograms (edited by Tsujiuchi: “Holographic Display”, pp. 51-52, pp. 211-219; 2 years (1
990) issued on December 7, 2008)).

Here, the principle of forming a hologram between a transmission hologram and a reflection hologram will be compared.

First, the principle of the transmission hologram will be described.

FIGS. 12 (a) to 12 (c) are explanatory views of a transmission hologram.

FIG. 12A is a plan view showing a diffracted light emitting direction, FIG. 12B is a diagram for explaining the principle of forming a hologram, and FIG. It is a figure showing the state of the formed interference fringes.

As shown in FIG. 12A, the transmission hologram has a reproduction illumination light 7 with the hologram 70 surface as a boundary.
This is a hologram from which diffracted light 73 exits on the side opposite to 2.
Representative examples include a Fresnel hologram and a rainbow hologram. As shown in FIG. 12 (b), two luminous fluxes of the reference light 74 and the object light 75 emitted from the point object light source 67 are incident on one side of the recording material to form a hologram as shown in FIG. As shown in c), the interference fringes are formed in a direction substantially perpendicular to the recording material surface. By using these recording characteristics, it was possible to use a high-definition liquid crystal display panel as a reproduction material of a transmission hologram.

Next, the principle of the reflection hologram will be described.

FIGS. 13 (a) to 13 (c) are illustrations of a reflection hologram.

FIG. 13A is a plan view showing the emission direction of the diffracted light, FIG. 13B is a diagram for explaining the principle of forming a hologram, and FIG. It is a figure showing the state of the formed interference fringes.

The reflection type hologram is a hologram in which the diffracted light 73 exits on the same side as the reproduction illumination light 72, as shown in FIG. A typical example is a Lippmann hologram. This is because, as shown in FIG. 13B, two luminous fluxes of the reference beam 74 and the object beam 75 are incident from both sides of the recording material to form a hologram.
As shown in (1), interference fringes are formed as a number of layers substantially parallel to the recording material surface.

Symbols used in FIGS. 12 (a) to 12 (c) and FIGS. 13 (a) to 13 (c) are the wavelength λ of the reference light 74, the reference light 74 and the object light. 75, and the wavefront 76 of the reference light 74 and the object light 75 is represented using a grid-like line.

Here, the Lippmann hologram will be described.

The Lippmann hologram is a hologram of a system in which the reference light and the object light enter the recording material surface from opposite directions and interfere with each other. The interference fringes are recorded as multiple layers parallel to the recording material surface. When light is applied to the Lippmann hologram, Bragg reflection due to the interference fringes is induced, so that a reproduced image of the recorded object can be three-dimensionally observed.

Bragg reflection is a phenomenon in which light of a specific wavelength is selectively reflected in a specific direction according to the interval and direction of interference fringes. At this time, light of other wavelengths not reflected is absorbed by the recording material in the case of the amplitude modulation hologram, and transmits through the recording material in the case of the phase modulation hologram. For this reason, the Lippmann hologram has a feature that white light can be used as illumination light for reproduction, and that a three-dimensional reproduced image can be observed in color.

The amplitude modulation type hologram is a light intensity distribution associated with the periodic structure of the interference fringes formed as a light transmittance distribution or an absorptivity distribution. As a typical example, blackened silver particles are used. A silver salt sensitive material hologram which has not been subjected to bleaching treatment is exemplified.

The phase modulation type hologram is obtained by forming a light intensity distribution as a phase difference distribution. A method of realizing a phase distribution corresponding to the light intensity distribution of the interference fringes by changing the refractive index inside the photosensitive layer. And a method of realizing a phase distribution by surface irregularities.

The features of the Lippmann hologram which is an example of the reflection hologram with respect to the transmission hologram are listed below.

First, since the reproduced image is observed by the reflected light from the hologram, the situation is the same as when an ordinary object is observed, and the reproduced image can be observed in a very natural atmosphere.

Second, there is parallax not only in the horizontal direction but also in the vertical direction. Further, a viewing area close to 180 ° can be ensured, and a reproduced image can be viewed from a wide range.

Third, even if the observation position is changed, the color of the reproduced image does not change.

Fourth, the brightness of the image is evaluated by the diffraction efficiency. In the case of the phase modulation type hologram, the efficiency theoretically reaches 100% at the maximum, so that a bright reproduced image can be obtained.

Fifth, by superposing a plurality of phase modulation holograms, it is possible to selectively reflect transmitted light. Further, since each hologram has excellent wavelength selectivity, a crosstalk image does not occur. According to this method, (a) chromatic dispersion is compensated, and a clear reproduced image can be obtained.

(B) A natural color hologram can be obtained using three laser beams of red, green and blue.
For example, commercially available photosensitive materials are different for red and green / blue, so the hologram of the red component is recorded on the photosensitive material for red with red light, and the hologram of the green and blue components is green / blue. A blue-sensitive photosensitive material can be used as a color hologram by recording by double exposure with green and blue light and superimposing them. Since the red component hologram is superior in terms of the brightness of the reconstructed image, the hologram of the green and blue components should be closer to the observer and the hologram of the red component should be closer to the observer. To balance.

Due to the above-mentioned features, the following characteristics were further required for the recording material (photosensitive material) of the Lippmann hologram as compared with the recording material of the transmission hologram. First, regarding the thickness of the recording material, from the viewpoint of reproduction, the limit length required for diffracted light to be mixed with each other is exceeded, the reflectance is further increased, and the reflected light is made steep. It is necessary to have a sufficiently thick reflective layer, that is, an interference fringe. On the other hand, from the viewpoint of recording, the reproduction wavelength width is widened, and the eye feels bright. For reference, the thickness of a photosensitive material (emulsion) used in a general Lippmann hologram is about 5 to 7 μm.

Second, a resolution of at least about 5000 lines / mm is required. The larger the value, the better. This is because a resolving power equal to or greater than the reciprocal value of the interference fringe interval is required. Also, in air, interference fringes are generated at intervals of about half of the recording wavelength. 0.5 to 1.6)
A resolution of about the above value is required.

Third, a hologram having a modulation method with high diffraction efficiency should be used. That is,
Ideally, a phase modulation hologram that can obtain a diffraction efficiency of 100% due to a change in refractive index or the like should be used. Thereby, the reproduced image becomes bright. Therefore, it is better that the phase modulation amplitude (refractive index difference and the like) is as large as possible.

The phase modulation type Lippmann hologram having the above-mentioned features can be said to be suitable for holographic television.

Accordingly, an object of the present invention is to provide a practical holographic television element and a practical holographic television device based on the principle of reproducing a phase modulation type Lippmann hologram.

[0045]

In order to achieve the above object, a holographic television element according to the present invention comprises: a transparent substrate having an incident surface on which incident light is incident and which is observed by an observer; A plurality of optical elements that are periodically arranged in the transparent substrate with respect to the direction, the refractive index for the incident light is substantially equal to the refractive index of the transparent substrate, and is changed by application of a signal. Have.

In the holographic television element of the present invention having the above-described configuration, a plurality of optical elements are periodically embedded in a transparent substrate having an index of refraction n, and the index of refraction of n is changed with respect to n by application of a signal. When the incident light enters the optical element changed by Δn, only light having a wavelength satisfying the Bragg condition is reflected, and the other light passes through the holographic television element. At this time, by modulating the refractive index of the optical element individually, interference fringes of the refractive index can be formed in the transparent substrate as a number of layers substantially parallel to the incident surface, and as a result, the holographic television element Then, a phase modulation type Lippmann hologram is formed.

In the holographic television element of the present invention, the plurality of optical elements may be composed of liquid crystal, or the plurality of optical elements may be composed of piezoelectric crystals.

The transparent substrate may be made of an isotropic polymer, or may be made of an anisotropic polymer. In particular, when a plurality of optical elements are made of liquid crystal and the transparent substrate is made of an anisotropic polymer, a long-range interaction acting between the molecules of the anisotropic polymer causes an alignment direction of the liquid crystal molecules having anisotropy. Since the holographic television elements can be naturally aligned in the same direction, opaque or cloudy appearance during observation of the holographic television element is largely suppressed.

The signal may be applied to the plurality of optical elements at a position which does not hinder the progress of the incident light.

A holographic television apparatus according to the present invention includes a holographic television element according to the present invention and a control unit capable of individually controlling the refractive index of each optical element in real time by individually applying a signal. And

Further, the holographic television device of the present invention comprises a plurality of laminated holographic television elements stacked in a direction perpendicular to the traveling direction of incident light so that the incident surface of the holographic television element is coplanar. Was formed by arranging in parallel so that the incidence surfaces of the laminated holographic television elements are coplanar,
The holographic television screen may have at least one holographic television screen, a plurality of holographic television screens may be arranged in the traveling direction of incident light, or adjacent holographic television elements. May be arranged such that the lamination directions are substantially orthogonal.

Further, the holographic television set of the present invention may have a receiving section for receiving a control signal sent from the outside and transmitting the control signal to the control section. Further, the control unit may have a signal restoring unit that decompresses or decodes the compressed or encrypted control signal and transmits it to the control unit.

[0053]

Next, embodiments of the present invention will be described in detail with reference to the drawings. (First Embodiment) FIG. 1A is a schematic configuration diagram of a holographic television element 6 for explaining the principle of the present invention, and FIG. 1B is a holographic television shown in FIG. Sectional views of a portion C of the John element 6 are shown.

The basic configuration of a holographic television is as follows:
It comprises a holographic television element 6 having a transparent substrate 1 and a minute optical element 2, and a control unit 3 capable of individually controlling a control signal 11 applied to the optical element 2.

The transparent substrate 1 has a refractive index of “n” with respect to the incident light 20 incident from the incident surface 10 and has a shape of
As long as it has a thickness sufficient to embed at least one optical element 2, the thickness may be sufficient to secure the minimum structural strength thereafter. Also,
The depth is on the order of 10 μm, which is the minimum required length, as described above with respect to the characteristics required for the recording material of the Lippmann hologram. The incident surface 10 on which the incident light 20 is incident is one side surface of the transparent substrate 1 and is a surface perpendicular to the plane 12 of the transparent substrate 1.

The optical element 2 has a size smaller than the wavelength of light, and is formed into a two-dimensional matrix in a direction parallel to and perpendicular to the incident surface 10 of the transparent substrate 1. A plurality of the recording materials are periodically embedded at intervals of about the resolution required for the recording material. Although the refractive index of the optical element 2 with respect to the incident light 20 is “nearly n”, when the control signal 11 is applied from a direction perpendicular to the incident light 20, the refractive index is modulated, and the refractive index of the transparent substrate 1 is reduced. A difference in refractive index “Δn” occurs between the two. It is necessary to prevent the control signal 11 from leaking out and adversely affecting the adjacent optical element 2 such as malfunction. In FIG. 1, as an example, a structure in which the control signal 11 is applied directly and individually to each optical element 2 is provided.

The control unit 3 detects that the incident light 20 is incident on the transparent substrate 1 from the incident surface 10, and the light reflected by the Bragg in the transparent substrate 1 jumps out of the incident surface 10 to the outside of the transparent substrate 1 again. It is placed in a position that does not interfere with the series of optical systems until it reaches 21.

The observer 21 observes the incident surface 10 of the holographic television having the above structure from the incident direction of the incident light 20.

Next, the operation principle of the holographic television element 6 will be described.

The optical element 2 controls the control signal 11 from the control unit 3.
Is not applied, the refractive index of the optical element 2 substantially matches the refractive index of the transparent substrate 1, so that the incident light 20 incident on the incident surface 10 of the transparent substrate 1 While passing through the transparent substrate 1 (see FIG. 1).
(A) and the right side in FIG. 1 (b)).

On the other hand, when the control signal 11 from the control unit 3 is applied to the optical element 2, the refractive index of the optical element 2 causes a difference “Δn” between the refractive index of the transparent substrate 1 and the refractive index.
When the optical element 2 located at a certain spatial period is continuously selected with respect to the traveling direction of the incident light 20 and the control signal 11 is applied only to the selected optical element 2, a series of selected Since the refractive index difference “Δn” occurs only in the optical element 2, the refractive index distribution at the spatial period is continuously generated in the transparent substrate 1. When the incident light 20 enters the holographic television element 6 having the refractive index distribution, only light having a wavelength satisfying the Bragg condition is reflected by an interference phenomenon, and other light is transmitted. The direction of the reflected light is specified by the wave vector of the incident light 20 and the reciprocal lattice vector of the refractive index distribution.

By individually modulating the refractive index of the optical element 2 of the transparent substrate 1 by the control unit 3, interference fringes of the refractive index are formed in the transparent substrate 1 as a number of layers substantially parallel to the incident surface 10. Can be. In addition, depending on the application method of the control signal 11, the layer spacing of the interference fringes of the refractive index can be controlled, and furthermore, the formation angle and the position of the layer can be freely controlled. As a result, a Lippmann hologram is formed in the holographic television element 6, and light of an arbitrary wavelength can be reflected in an arbitrary direction in a plane parallel to the substrate plane of the transparent substrate 1.

By performing the refractive index modulation of the optical element 2 from the control unit 3 in real time, the Lippmann hologram formed in the holographic television element 6 can also be controlled in real time. Can be used as a television.

The optical element 2 is embedded in the holographic television element 6 only in one direction (horizontal direction in FIGS. 1A and 1B) when viewed from the observer 21. Not. Therefore, parallax occurs only in that direction.

Next, a holographic polymer dispersed liquid crystal (HPDLC) applicable as the optical element 2 will be described.

Conventionally, holographic polymer dispersed liquid crystal (HPDLC) has been used in a color reflection type liquid crystal display such as a computer or a color projection system.
In order to produce RGB light beams with high color purity, research and development have been advanced as a new reflective material without using a conventional light absorbing material such as a color filter, a dye and a polarizing plate.
For example, "Date, Tanaka, Kato, Sakai:" Reflection-type display device using holographic polymer dispersed liquid crystal (HPDLC) ", The Institute of Television Engineers of Japan, Vol. 20, No. 9,
131-136, published on February 21, 1996 (1996), that the liquid crystal layer and the polymer layer in the HPDLC cell are separated into individual wavelengths of RGB by injecting laser beams from both sides of the HPDLC cell. 3 can be selectively reflected by dispersing the light into a period corresponding to
Prototypes of various types of cells have been successfully manufactured. Moreover, three types of H
By overlapping the PDLC cells and applying an electric field to each HPDLC cell, color mixing of reflected light is confirmed.

The operation principle of such an HPDLC cell will be described with reference to FIGS. 2 (a) and 2 (b).

FIG. 2A shows the ON state of the HPDLC cell, and FIG. 2B shows the OFF state of the HPDLC cell.

In the HPDLC cell, the liquid crystal layer 31 in a liquid crystal droplet state is dispersed in the polymer layer 30 so as to have a one-dimensional period approximately equal to the wavelength of light, and the surface on the back side of the polymer layer 30 is dispersed. A light absorbing layer 82 is attached to the surface (the surface opposite to the surface on which the incident light 120 is incident), and a transparent cell electrode 81 is sandwiched between the front and back surfaces of the light absorbing layer 82, and the outside is sandwiched between glass 80.

When the incident light 120 enters the refractive index distribution, only light having a wavelength satisfying the Bragg condition is reflected by the interference phenomenon, and other light is transmitted. The direction of the reflected light, that is, the direction of the diffracted light 173 is specified by the wave vector of the incident light 120 and the reciprocal lattice vector of the refractive index distribution. The state in which the specific wavelength is reflected in the specific direction is used as the display of the ON state (bright state) shown in FIG.

Next, when a voltage is applied to this element, the orientation direction of the liquid crystal layer 31 is inclined in the direction of the electric field, and the refractive index changes accordingly. When the changed refractive index of the liquid crystal layer 31 matches the refractive index of the polymer layer 30, the refractive index distribution disappears, and all the incident light 120 is transmitted. This transmitted light is absorbed by the light absorbing layer 82 disposed on the back surface of the cell. Such a state is used as an OFF state (dark state) shown in FIG.

Further, "Date, Takeuchi, and Kato:" Reflective display device using memory holographic polymer dispersed liquid crystal (HPDLC) ", ITE Technical Report, No. 21.
Vol. 73, pp. 31-36, 1997 (1997)
According to the “Issued on November 28”, a laser beam is incident on the front side of the HPDLC cell, and scattered light from a stationary object is incident on the rear side of the HPDLC cell to form a Lippmann hologram inside the HPDLC cell. Successful, HPD
It was confirmed that the LC cell could be used as a recording material for Lippman holograms.

Also, "Mimura, Sumiyoshi:" Optical Numerical Calculation of Holographic PDLC (HPDLC) ", ITE Technical Report, Vol. 22, No. 5, 57-62.
Page, issued on January 30, 1998 (1998) ", the numerical calculation of the optical characteristics of HPDLC is performed,
Even the prediction of the optical characteristics of the PDLC element has been performed.

Next, the holographic television element 106 of the first embodiment using the HPDLC will be described with reference to FIGS. 3 (a) to 3 (e).

FIG. 3A is a sectional view of the holographic television element 106.

The holographic television element 106 of the present embodiment is composed of isotropic polymer molecules on which the incident light 120 first enters, and has a polymer layer 130 having a refractive index of “n”.
And a liquid crystal layer 131 composed of liquid crystal molecules 134 (see FIG. 3B) and having a refractive index of “nearly n”. The liquid crystal layer 131 is sandwiched by the alignment layer 133 from above and below, and further sandwiched by the electrode 132 to which the control signal 111 is applied from above and below. By forming the alignment layer 133 from a polished polymer layer or the like, a homogeneous ground boundary state is formed between the alignment layer 133 and the liquid crystal layer 131.
It is oriented in the same direction as 20.

A one-dimensional periodic refractive index structure is formed by dispersing the liquid crystal layer 131 and the polymer layer 130 having different refractive indices in a cycle of about the wavelength of visible light.

Note that the sectional view of the holographic television element 106 shown in FIG. 3A corresponds to the sectional view of the holographic television element 6 shown in FIG. That is, the polymer layer 130 corresponds to the transparent substrate 1, and the liquid crystal layer 131 corresponds to the optical element 2.

Next, the change in the holographic television element 106 due to the application of the control signal 111 is shown in FIG.
This will be described with reference to FIGS. 3C, 3D, and 3E.

FIG. 3B shows the state of the liquid crystal molecules 134 in the liquid crystal layer 131 when the control signal 111 is not applied.
Shows the distribution of the refractive index from the polymer layer 130 to the liquid crystal layer 131 in this state.

FIG. 3D shows the state of the liquid crystal molecules 134 in the liquid crystal layer 131 when the control signal 111 is applied.
(E) shows the state in which the polymer layer 130 and the liquid crystal layer 13 are in this state.
The distribution of the refractive index over 1 is shown.

The section indicated by arrow B in FIGS. 3C and 3E corresponds to the polymer layer 130, and the section sandwiched by the dashed line indicated by arrow A corresponds to the liquid crystal layer 131, respectively.

As shown in FIG. 3B, when the switch 135 is OFF with respect to the power supply 136, no electric field is generated between the electrodes 132. In this state, the liquid crystal molecules 134 in the liquid crystal layer 131 are oriented in the same direction as the incident light 120 because the alignment layer 133 forms a homogeneous ground boundary state, and the refractive index of the liquid crystal layer 131 is “nearly n”.
Becomes Accordingly, the distribution of the refractive index from the polymer layer 130 to the liquid crystal layer 131 has a substantially constant value as shown in FIG.

On the other hand, when the switch 135 is turned on, as shown in FIG. 3D, the electric field generated between the electrodes 132 causes the liquid crystal molecules 134 in the liquid crystal layer 131 to be oriented in the direction of the electric field. A refractive index difference “Δn” occurs between the liquid crystal layers 131. That is, the distribution of the refractive index from the polymer layer 130 to the liquid crystal layer 131 is as shown in FIG.

Here, the above-mentioned “Mimura, Sumiyoshi:“ Optical Numerical Calculation of Holographic PDLC (HPDLC) ””, Technical Report of the Institute of Image Information and Television Engineers, Vol. 22, No. 5, 57
-62 pages, published on January 30, 1998 "
, The refractive index dispersion period required for Bragg reflection is estimated below.

When the refractive index of the polymer layer 130 at a wavelength of 500 nm is 1.51, the refractive index of the liquid crystal layer 131 at a wavelength of 500 nm when no electric field is applied is 1.54, and the refractive index when an electric field is applied is 1.70. , And the refractive index difference “Δn” is 0.
19, which is a refractive index dispersion sufficient to induce Bragg reflection. At this time, for a light beam having a wavelength of 500 nm in the air, the period of the refractive index dispersion required in the holographic television element 106 having this characteristic is 500 ÷ 2.
÷ 1.51 = about 166 nm (resolution: about 6000 lines / m)
m), and an electric field is selectively applied only to the liquid crystal layer 131 located at this interval, so that the wavelength is 500 nm.
Can be reflected by Bragg.

If the minimum wavelength of light is set to 400 nm, the refractive index dispersion period required in the holographic television element 106 having the above characteristics is 132 nm (resolution: about 750).
0 / mm), and the individual liquid crystal layers 131 need to be arranged at even smaller intervals (166 Å even if it is assumed to be 1/8). For faithful image reproduction,
Further research is needed on the materials to be selected and the fine processing technology.

It is also possible to orient the liquid crystal molecules 134 in that direction by making a cut in the surface of the electrode 132 in one direction or by rubbing the surface in one direction with cotton or the like. It is. By performing such a surface treatment on the electrode 132, the above-described alignment layer 133 can be made unnecessary.

As described above, the Bragg reflection is caused by changing the refractive index of the liquid crystal layer 131 so that a refractive index difference is generated with respect to the refractive index of the polymer layer 130.
A practical holographic television element 6 using the phase modulation type Lippmann hologram reproduction principle can be provided.

As described above, by using the reproduction principle of the Lippmann hologram, white light can be used as the reproduction illumination light, and a very natural reproduced image can be obtained even when the observation position is changed without changing the color of the reproduced image. it can.

Since the Lippmann hologram of this embodiment is of the phase modulation type, a bright reproduced image can be observed.

Note that the electrode 132 does not necessarily have to be transparent in order to apply the control signal 111 from a direction perpendicular to the incident light 120. (Second Embodiment) Next, a holographic television element 206 according to a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIGS.

The holographic television element 206 of the present embodiment is obtained by replacing the isotropic polymer layer 130 of the holographic television element 106 of the first embodiment with an anisotropic polymer layer 240. Since the configuration is the same as that of the first embodiment, a detailed description is omitted.

By forming the anisotropic polymer layer 240 so that the anisotropic polymer molecules 241 (see FIG. 4B) are aligned in the same direction as the incident light 220, the liquid crystal molecules 234 in the liquid crystal layer 231 are also formed. It is aligned in the same direction as the incident light 220.
This is because the use of the anisotropic polymer molecules 241 allows the liquid crystal molecules 234, which also have anisotropy, to be naturally aligned in the same direction by a long-range interaction acting between the molecules.

When an isotropic polymer is used for the polymer layer, the alignment of the polymer molecules becomes random, and the polymer molecules and the liquid crystal molecules are not aligned. As a result, the reflectance of the reflection type display decreases from a certain angle. In addition, it sometimes looked opaque or cloudy. To greatly suppress this, the use of anisotropic polymers as described above makes it possible to naturally align liquid crystal molecules that also have anisotropy in the same direction due to the long-range interaction that acts between the molecules. Was. As a result, opaque or cloudy appearance is greatly suppressed.

Next, the change in the holographic television element 206 due to the application of the control signal 211 is shown in FIG.
This will be described with reference to FIGS. 4C, 4D, and 4E.

FIG. 4B shows the state of the liquid crystal molecules 234 in the liquid crystal layer 231 when the control signal 211 is not applied, as shown in FIG.
Indicates that the anisotropic polymer layer 240 in this state
The distribution of the refractive index over 1 is shown.

FIG. 4D shows the state of the liquid crystal molecules 234 in the liquid crystal layer 231 when the control signal 211 is applied.
(E) shows the state in which the polymer layer 240 and the liquid crystal layer 23 are in this state.
The distribution of the refractive index over 1 is shown.

4C and 4E, the section indicated by the arrow B corresponds to the polymer layer 240, and the section between the dashed lines indicated by the arrow A corresponds to the liquid crystal layer 231.

As shown in FIG. 4B, when the switch 235 is turned off with respect to the power source 236, no electric field is generated between the electrodes 232. In this state, the liquid crystal molecules 234 in the liquid crystal layer 231 are aligned in the same direction as the incident light 220 because the anisotropic polymer molecules 241 in the anisotropic polymer layer 240 are aligned. Incident light 220
And the refractive indices of the anisotropic polymer molecules 241 and the liquid crystal molecules 234 are almost the same. Therefore,
The distribution of the refractive index from the anisotropic polymer layer 240 to the liquid crystal layer 231 has a substantially constant value as shown in FIG.

On the other hand, when the switch 235 is turned on, as shown in FIG. 4D, the electric field generated between the electrodes 232 causes the liquid crystal molecules 234 in the liquid crystal layer 231 to be oriented in the direction of the electric field. A refractive index difference “Δn” occurs between the polymer layer 240 and the liquid crystal layer 231. That is, the anisotropic polymer layer 2
The distribution of the refractive index from 40 to the liquid crystal layer 231 is as shown in FIG.

As described above, in the present embodiment, as in the first embodiment, white light can be used as illumination light for reproduction, and a very natural reproduced image can be observed, and the color of the reproduced image can be observed even when the observation position is changed. Can be observed without change, and a bright reproduced image can be observed.

Further, by using an anisotropic polymer for the polymer layer, the opacity and fogging of the image to be observed can be eliminated.

Note that, since the control signal 211 is applied from a direction perpendicular to the incident light 220, the electrode 232 is not necessarily required to be transparent. (Third Embodiment) Next, a holographic television element 306 according to a third embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIGS.

The holographic television element 306 of this embodiment shown in FIG. 5A uses a piezoelectric crystal called a Pockels cell 351 as an optical element.
An electrode 332 is attached to the c-plane 353 (see FIGS. 6A and 6B) of the Pockels cell 351. Further, the transparent substrate 350 has the same refractive index as the Pockels cell 351 when no electric field is applied.

The remaining configuration is basically the same as that of the holographic television element shown in the first and second embodiments, and therefore, detailed description is omitted.

As shown on the right side of FIG. 5A, the x-axis is in the traveling direction of the incident light 320, the y-axis is in the depth direction in the direction normal to the plane of the drawing, and is perpendicular to the x-axis and the y-axis. It is assumed that a coordinate system having the z-axis in the upward direction is used.

Here, the Pockels effect will be described (see “Ogawa:“ Crystal Physics Engineering ”, pp. 128-133, issued November 15, 1976 (1976))).

The Pockels effect is also called a linear electro-optic effect. When the refractive index is n and the electric field is E, 1 / n
The relationship that ² is proportional to the electric field E is established. this is,
This effect is found only in piezoelectric crystals. A typical crystal is a KDP crystal (KH ₂ PO ₄ ). The KDP crystal is a transparent crystal, and its outer shape has a tetragonal system as shown in FIG. KDP crystals are also uniaxial crystals. The main axes of the index ellipsoid are x1, x2 and x
Taking three axes (= c-axis), the refractive index in the x1-axis and x2-axis directions is no (ordinary ray refractive index), and the refractive index in the x3-axis direction is n
e (abnormal light refractive index). For this KDP crystal, K
When an electric field E is applied in parallel to the c-axis of the DP crystal, the Pockels effect occurs, and the KDP crystal becomes a biaxial crystal. If the main axes of the new index ellipsoid are taken as the X axis, Y axis and Z axis,
The Z axis is parallel to the x3 axis, and the X and Y axes make an angle of 45 ° with the x1 and x2 axes. The refractive index nx in the X-axis direction and the refractive index ny in the Y-axis direction are represented by nx = no−0.5 × no ³ × r × E ny = no + 0.5 × no ³ × r × E You.

Here, the proportionality constant r is called a Pockels coefficient.

With respect to this KDP crystal, the KDP crystal is cut on a plane perpendicular to the Z axis. This cut surface is generally
The “c-plane”, in which the c-plane 353 is provided with electrodes, is generally called a “Pockels cell”.

In this embodiment, as shown in FIG. 6B, the KDP crystal is cut on a plane parallel to the X-axis, the Y-axis and the Z-axis, and cut on the C-plane 353 which is a cut noodle perpendicular to the Z-axis. The Pockels cell provided with the electrode 332 is used as the optical element 2.

Next, changes in the refractive index in each direction in the holographic television element 306 due to the application of the control signal 311 will be described with reference to FIGS. 5 (b), 5 (c), 5 (d) and 5 (c). (E). Here, the traveling direction of the incident light 320 is x
The axial direction and the application direction of the control signal 311 are defined as the z-axis direction (see FIG. 5A).

The section indicated by the arrow B in FIGS. 5B to 5E corresponds to the substrate 350, and the section sandwiched by the dashed line indicated by the arrow A corresponds to the Pockels cell 351.

FIGS. 5B and 5C show the Pockels cell 351 from the substrate 350 when the control signal 311 is not applied.
3 shows the distribution of the refractive index over the range. That is, the control signal 31
Since no 1 is applied, no electric field is generated between the electrodes 332. For this reason, the main axes of the refractive index ellipsoid point in the x1, x2, and x3 axes, and the refractive index in the y-axis direction is
Both the Pockels cells 351 have no (ordinary light refractive index), and the refractive indexes in the z-axis direction both have ne (excessive light refractive index). That is, the refractive index takes a constant value regardless of the depth coordinate x.

FIGS. 5D and 5E show the distribution of the refractive index from the substrate 350 to the Pockels cell 351 when the control signal 311 is applied. That is, the control signal 311
As a result, an electric field is generated between the electrodes 332, so that the main axis of the refractive index ellipsoid changes to the X axis (= x axis), the Y axis (= y axis), and the Z axis (= z axis). The refractive index in the y-axis direction is no + on the substrate 350 side, but no + 0.5 × no ³ × r × E on the Pockels cell 351 side, and the refractive index difference “Δn = 0.5 × no ³ × r × E ”has occurred. The refractive index in the z-axis direction remains unchanged at ne, and does not change.

As a result, light having an electric field component in the y-axis direction travels in the refractive index dispersion, and can generate a predetermined Bragg reflection.

In the present invention, KD is used as the piezoelectric crystal.
Although a P crystal was used, another piezoelectric crystal (ADP (NH ₄ H ₂ P
Pockels cell may be created using O ₄ ).

As described above, in the present embodiment using a crystal, white light can be used as illumination light for reproduction similarly to the first and second embodiments using liquid crystal, and a very natural reproduced image can be observed. Even when the observation position is changed, the color of the reproduced image can be observed without change, and a relatively bright reproduced image can be observed.

Note that, since the control signal 311 is applied from a direction perpendicular to the incident light 320, the electrode 332 does not necessarily have to be transparent. (Fourth Embodiment) Next, FIGS. 7A and 7B are schematic structural views of a holographic television 7 according to a fourth embodiment of the present invention.

The holographic television 7 shown in FIGS. 7A and 7B uses the holographic television element 6 shown in the first embodiment.

The holographic television 7 shown in FIG.
Is constituted by stacking a plurality of holographic television elements 6 in a direction perpendicular to the incident light 20. The holographic television element 6 has a structure in which the holographic television elements 6 are merely stacked in a plane, and can be said to be structurally the same as a multi-slit rainbow hologram having multiple slits in the vertical direction.

Thus, the holographic television 7
Can be expanded in the up, down, left, and right directions, and in particular, in the left and right directions, a reproduced image can be observed from a wide range near 180 °. Furthermore, since the interval between the stacked holographic television elements 6 is very narrow, the observer 21 can observe the reproduced image as one holographic television 7.

The holographic television 7 shown in FIG.
Is constructed by not only overlapping the holographic television element 6 in a plurality of stages in a direction perpendicular to the incident light 20 but also overlapping a plurality of stages in the traveling direction of the incident light 20.

As described above, as a feature of the Lippmann hologram, selective reflection of transmitted light becomes possible, and compensation of chromatic dispersion, clarification of a reproduced image, and naturalization of a reproduced color can be realized.

In this embodiment, the holographic television element 6 is used. However, the holographic television element shown in the second and third embodiments may be used.

As described above, the holographic television of this embodiment uses the holographic television elements described in the first to third embodiments, so that the viewing area can be widened in the up, down, left, and right directions, and observation can be performed from a wide range. In addition, white light can be used as the illumination light for reproduction, and a very natural reproduction image can be observed from a wide range, and the color of the reproduction image can be observed even when the observation position is changed. Can be observed. (Fifth Embodiment) Next, a schematic configuration diagram of a holographic television 17 according to a fifth embodiment of the present invention is shown in FIG.
And FIG. 8 (b).

The holographic television 17 shown in FIGS. 8A and 8B uses the holographic television element 6 shown in the first embodiment.

The holographic television set 17 shown in FIG. 8A has a receiving section 4 for receiving a control signal sent from the outside and transmitting the control signal to the control section 3, thereby providing a hologram of a Lippmann hologram. Enables remote transmission and reproduction of information.

The holographic television set 17 shown in FIG. 8B further includes, in addition to the configuration shown in FIG. 8A, the compressed or encrypted control signal received by the receiving section 4. It has a signal restoring unit 5 which expands or decodes and transmits it to the control unit 3.

Since transmission of hologram information requires a huge amount of information, compression transmission is essential. In addition, it becomes possible to transmit the data after scrambling, so that security measures can be taken. This makes it possible to realize a holographic broadcast system compatible with Lippmann holograms in the future.

Although the holographic television element 6 is used in this embodiment, the holographic television element shown in the second and third embodiments may be used.

Further, as shown in FIG. 7B, the holographic television may be constituted by superposing a plurality of stages in the traveling direction of the incident light 20.

As described above, in the holographic television according to the present embodiment, when a signal received from an external device is received as a reproduced image, as in the fourth embodiment, the holographic television according to the first to third embodiments has the same structure. By using the described holographic television element, the viewing area can be expanded in the up, down, left, and right directions, and observation can be performed from a wide range, and white light can be used as illumination light for reproduction, and a very natural reproduced image can be observed from a wide range. In addition, even if the observation position is changed, the color of the reproduced image can be observed without change, and a bright reproduced image can be observed. (Sixth Embodiment) Next, FIG. 9 shows a schematic configuration diagram of a holographic television 27 according to a sixth embodiment of the present invention.

The holographic television 27 shown in FIG.
The holographic television element 6 shown in the first embodiment is used.

The holographic television 2 of the present embodiment
Reference numeral 7 indicates that the arrangement direction of the holographic television elements 6 shown in the fourth and fifth embodiments is only superimposed in the vertical direction, while the direction of the incident surface 10 of some holographic television elements 6 Is a unit, and the holographic television cell 8 formed by regularly superimposing the holographic television elements 6 in the same direction is used as a unit. It is configured by overlapping several stages in order.

The direction of the parallax of the holographic television cell 8 coincides with the cell direction 9.

In the case of the present embodiment, the holographic television cell 8 having only one direction of parallax is replaced with the cell direction 9.
Are alternately overlapped vertically and horizontally, so that a reproduced image can be viewed in a pseudo manner in the vertical and horizontal directions, that is, in a two-dimensional direction.

In this embodiment, the holographic television cell 8 is rectangular, and the holographic television cell 8 is, for example, a hexagonal cell in which the cell directions 9 are vertically and horizontally alternately stacked in several stages. And the like, and all the holographic television elements 6 constituting the holographic television cell 8 do not have to face in the same direction.

In this embodiment, the holographic television element 6 is used, but the holographic television element shown in the second and third embodiments may be used.

Further, as shown in FIG. 7 (b), it may be constituted by superposing a plurality of stages in the traveling direction of the incident light 20, or as shown in FIGS. 8 (a) and 8 (b). Some may include a receiving unit or a signal restoring unit.

As described above, the holographic television of the present embodiment uses the holographic television element described in the first to third embodiments, as in the fourth embodiment, so that white light can be used as reproduction illumination light. Light can be used, and a very natural bright reconstructed image can be observed without changing the color of the reconstructed image even if the observation position is changed, a wide viewing area can be secured, and the reconstructed image is observed so that there is parallax in the vertical and horizontal directions. be able to.

[0143]

As described above, according to the present invention, a phase modulation type Lippmann hologram is formed in a holographic television element. As a result, white light can be used as illumination light for reproduction, the reproduced image can be observed in a very natural atmosphere, the reproduced image can be viewed from a wide range, and even if the observation position is changed, the color of the reproduced image does not change. A clear natural color hologram can be obtained in which a bright reproduced image is obtained and a crosstalk image is not generated.

In particular, when a plurality of optical elements are made of liquid crystal and the transparent substrate is made of an anisotropic polymer, a long-range interaction acting between the molecules of the anisotropic polymer causes the liquid crystal molecules having anisotropy to be aligned in the alignment direction. In contrast, they can be naturally aligned in the same direction. As a result, the holographic television element is largely prevented from appearing opaque or cloudy when observed.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of holographic television.

FIG. 2 is a diagram illustrating an operation principle of an HPDLC cell.

FIG. 3 is a diagram illustrating a holographic television element according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a holographic television element according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a holographic television element according to a third embodiment of the present invention.

FIG. 6 is a view showing a KDP crystal.

FIG. 7 is a schematic configuration diagram of a holographic television according to a fourth embodiment of the present invention.

FIG. 8 is a schematic configuration diagram of a holographic television according to a fifth embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of a holographic television according to a sixth embodiment of the present invention.

FIG. 10 is a diagram illustrating the principle of a display unit of a conventional holographic television system.

11 is a diagram showing an application example of the conventional holographic television system shown in FIG.

FIG. 12 is a diagram illustrating the principle of a transmission hologram.

FIG. 13 is a diagram illustrating the principle of a reflection hologram.

[Explanation of symbols]

Reference Signs List 1 transparent substrate 2 optical element 3 control unit 4 receiving unit 5 signal restoring unit 6, 106, 206, 306 holographic television element 7, 17, 27 holographic television 8 holographic television cell 9 cell direction 10 incidence plane 11, 111, 211, 311 control signal 12 plane 20, 120, 220, 320 incident light 21, 421 observer 30, 130 polymer layer 31, 131, 231 liquid crystal layer 132, 232, 332 electrode 133 alignment layer 134, 234 liquid crystal molecule 135, 235 Switch 136, 236 Power supply 240 Anisotropic polymer layer 241 Anisotropic polymer molecule 350 Substrate 351 Pockels cell 60 High definition liquid crystal display panel 61 Normal matrix arrangement type liquid crystal element 62 Transmitting unit 63 Liquid crystal driving unit 64 Laser light source 65 Simple matrix Liquid crystal display element 66 image memory 67 point object light source 70 hologram 71 transmission path 72 reproduction illumination light 73,173 diffracted light 74 reference light 75 object light 76 wavefront 80 glass 81 cell electrode 82 light absorption layer 353 c-plane

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H049 CA01 CA05 CA08 CA22 CA30 2K008 AA00 BB04 BB05 CC01 CC03 DD02 DD23 FF03 FF07 HH19 HH26 5C061 AA29 AB11 AB12 AB14 AB17 AB24 5C094 AA01 AA08 AA12 BA43 BA65 DA03 DB EB02 ED11 ED14 FA01 FA02 FB01 FB20

Claims (12)

[Claims] 1. A transparent substrate on which incident light is incident and having an incident surface on which an observer observes, and the incident light periodically arranged in the transparent substrate with respect to a traveling direction of the incident light. And a plurality of optical elements having a refractive index substantially equal to the refractive index of the transparent substrate and changing with the application of a signal. 2. The holographic television element according to claim 1, wherein the plurality of optical elements are made of liquid crystal. 3. The holographic television element according to claim 1, wherein the plurality of optical elements are made of a piezoelectric crystal. 4. The holographic television device according to claim 1, wherein the transparent substrate is made of an isotropic polymer. 5. The holographic television device according to claim 1, wherein the transparent substrate is made of an anisotropic polymer. 6. The holographic television device according to claim 1, wherein application of a signal to the plurality of optical elements is provided at a position that does not hinder the progress of the incident light. 7. The holographic television element according to claim 1, wherein the refractive index of each optical element is individually controlled in real time by individually applying the signal. A holographic television device comprising: 8. A multi-layer holographic television device, comprising: a plurality of multi-layer holographic television elements stacked in a direction perpendicular to a traveling direction of the incident light so that the incident surface of the holographic television element is coplanar. 8. The holographic television apparatus according to claim 7, comprising at least one holographic television screen formed by arranging the entrance surfaces of the television elements in parallel so as to be on the same plane. 9. The holographic television apparatus according to claim 8, wherein the plurality of holographic television screens are arranged also in a traveling direction of the incident light. 10. The holographic television device according to claim 8, wherein the laminated holographic television elements adjacent to each other are arranged so that the laminating directions thereof are substantially orthogonal. 11. The holographic television apparatus according to claim 7, further comprising a receiving unit that receives a control signal sent from outside and transmits the control signal to the control unit. 12. The holographic television according to claim 11, further comprising: a signal restoring unit that decompresses or decodes the compressed or encrypted control signal received by the receiving unit and transmits the decompressed or encrypted control signal to the control unit. apparatus.