JPH11234705A - Stereoscopic display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To converge an output picture at the position of an observer even when the observer changes a distance from a display screen by converting an illuminating light inputted to a liquid crystal element into an almost parallel light by a parallel converting element, and providing a direction converting element for varying an outputting direction for each picture element. SOLUTION: A diffused light from an illuminating light source 1 is converted into an almost parallel light by a parallel converting element 2 and made incident to a liquid crystal element 3. The parallel light is converted into picture information by a liquid crystal element 3, and the picture information is outputted in a specific direction by a direction converting element 4. The position information of an observer 8 is detected as spatial information by cameras 1 and 2, and a direction converting element 4 is operated based on the spatial information, and right and left stereoscopic picture information is inputted to the right and left eyes of the observer 8. When the observer 8 moves, the position information is detected according to the movement of the observer 8, and the outputting direction of the stereoscopic picture information is obtained by a controller 7 based on the position information, and the outputting direction of the stereoscopic picture information is changed by the direction converting element 4, and the stereoscopic picture information is inputted to both eyes of the observer 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional display device capable of three-dimensional display.

[0002]

2. Description of the Related Art The parallax barrier method and lenticular method have been conventionally used as methods for observing left and right images having stereoscopic binocular parallax without using glasses. In this method, independent binocular parallax images are observed at right and left eyes at specific positions, but the positions of eyes that can be stereoscopically viewed are limited. That is, when the eye is shifted to the right or left at the same distance from the eye, a phenomenon occurs in which the front and rear of the solid are reversed.

In order to improve this phenomenon, a method has been developed in which the barrier of the parallax barrier is inverted by using a liquid crystal so as to follow a change in the eye position. This method
This is a method in which the liquid crystal is inverted using information from an infrared sensor that detects the position of the eye to cope with a change in the position of the eye (Japanese Unexamined Patent Publication No. Hei 7-261119).
Items related to parallax barrier, Japanese Patent Application Laid-Open No. 9-1526
No. 68: Matters concerning an observer position tracking method).

[0004]

In the conventional parallax barrier system and lenticular system, the positions of the eyes that can be viewed with both eyes are fixed in all directions. Also, as described above, the method of inverting the parallax barrier using liquid crystal can improve the left-right direction, but this method only inverts the liquid crystal barrier, and the barrier interval is set in advance. Since the display screen is fixed at intervals, the display screen follows the horizontal movement of the display screen discontinuously, but does not follow the vertical movement. That is, the position at which the stereoscopic image can be observed is improved in the horizontal direction with respect to the display screen, but not in the vertical direction. Even though the observer can shake his / her head, it is necessary to keep the distance from the display screen constant at all times. As a result, a long-time observation of the display screen does not allow the observer to have a high degree of positional freedom and causes fatigue.

[0005]

According to the present invention, a parallel conversion element converts illumination light input to a liquid crystal element into substantially parallel light, and provides a direction conversion element for changing the output direction for each pixel. Even if the observer changes the distance from the display screen, it is possible to converge the output image at the position of the observer.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. First, the configuration of the present invention will be described. FIG. 1 shows a principle diagram of the present invention.

In FIG. 1, a general backlight or the like used for a liquid crystal display element can be used as an illumination light source 1. Although the light output from the illumination light source 1 is diffuse light, it is converted by the parallel conversion element 2 into substantially parallel light. The light converted into parallel light enters the liquid crystal element 3, is converted into image information by the liquid crystal element 3, and is output as substantially parallel light. The image information output as substantially parallel light outputs pixel information in a specific direction by the direction conversion element 4 and is output to the position of the observer.

The position information of the observer includes two cameras 1 and 2
Is detected as spatial information. The direction conversion element is operated based on the spatial information obtained from the camera, and the left and right stereoscopic image information is input to the left and right eyes of the observer 8. When the observer moves, position information is detected in accordance with the movement of the observer, the output direction of the pixel signal is obtained by the controller 7 based on the information, and the direction is changed by the direction conversion element 4 to change the direction of the observer 8. Input to both eyes.

FIG. 2A shows the principle of the parallel conversion element.
As the illumination light source 11, a generally used light source for a liquid crystal element is used. The parallel conversion element 12 includes two sets of cylindrical lenses and a slit. The distance between adjacent lenses of the cylindrical lens is equal to the distance between pixels of the liquid crystal element, the lens thickness is equal to the lens focal length, and one surface is flat. A slit is provided on the plane side of one of the cylindrical lenses. The slit has an opening on the center line of each cylindrical lens.

The width of the aperture is related to the accuracy of the obtained parallelism. The narrower the parallel light component, the more the parallel light component increases. However, the light quantity decreases, so it is necessary to determine the width in consideration of the output intensity of the illumination light source 11. The parallelism used here is a parallelism on a plane parallel to the paper surface, a direction perpendicular to the paper surface,
That is, there may be no parallelism in the axial direction of the cylindrical lens.

The light output from the illumination light source 11 has a random traveling direction. Random light is condensed by the cylindrical lens, and a light ray passing through only the opening of the slit 14 enters the other cylindrical lens. Since the opening is located at the focal point of the cylindrical lens, light transmitted through the opening and the cylindrical lens is output as substantially parallel light. The material of the slit 14 is not limited as long as it is a material that blocks light, but is preferably a metal. As an example, a deposited film of aluminum can be used.

On the output side, it is desirable that reflection is small because return light affects contrast, crosstalk and the like. As an example, it can be realized by a laminated film of chromium and aluminum. In addition, in order to effectively use light that does not pass through the slit, it is preferable to function as a mirror having a high reflectance in order to return to the illumination light source side. As an example, aluminum has a reflectivity of 90% and is a preferred material. In order to further enhance the reflection efficiency, it is desirable to use a dielectric multilayer film reflection mirror. The light that has been reflected and returned to the illumination light source 11 is reflected and scattered several times again, and is again applied to the parallel conversion element 12.

FIG. 2B shows a combination of parallel conversion elements having improved parallelism. The hatched portion in (b) is a hologram element, which is a transmission type hologram element in which a random wavefront of an illumination light source and a wavefront of parallel light interfere with each other to produce a hologram. By inserting this hologram element between the illumination light source and the parallel conversion element, most of the light components from the illumination light source are converted into parallel light in advance, so that the light can be converted into parallel light with high conversion efficiency. Furthermore, components that are not converted into parallel light by the hologram element are cut by the parallel conversion element, so that the illumination light source that has passed through both becomes a light source with higher parallelism.

Next, the direction change element will be described. FIG. 3 shows a cross section of the direction change element. The direction changing element is provided between a first transparent substrate 21 having a divided first transparent electrode and a second transparent substrate 25 having a divided taper opposed to the divided first transparent electrode 22. Is formed by filling liquid crystal. The common electrode 24 is formed on the second transparent substrate 25. In the drawing, since the light transmitted through the liquid crystal element is incident on the first transparent substrate almost perpendicularly, the refractive index of the material of the first transparent substrate does not affect the trajectory of the light beam. The light transmitted through the first transparent substrate 21 transmits the liquid crystal, and the second transparent substrate 2
5 is reached.

Since the second transparent substrate 25 has a taper and has an inclination with respect to the light beam, if a difference in refractive index occurs between the liquid crystal 23 and the second transparent substrate 25, the trajectory of the light beam is bent. Become. When an electric field is applied to the liquid crystal, the orientation direction of the liquid crystal molecules changes, and the change in the orientation direction causes a change in the refractive index for polarized light.

FIG. 3 is a diagram schematically illustrating a refraction direction of a light beam. nair is the refractive index of air, n0 is the second transparent substrate 2
Assuming that the refractive index of No. 5 and n1 to n4 are the refractive indices of the liquid crystal in a state where electric fields having different intensities are applied, the refractive index of the second transparent substrate is calculated based on the following (Equation 1) Is large, it can be converged in a specific direction as shown in FIG.

Nair <n1 <n2 <n3 <n4 <n0 (Equation 1) Conversely, when the condition of (Equation 2) described below, that is, when the refractive index of the liquid crystal is larger than the refractive index of the second transparent substrate, 5, it is possible to converge in the opposite direction.

Nair <n0 <n1 <n2 <n3 <n4 (Equation 2) In order to obtain the effects as shown in FIGS. 3 and 5, the refractive index of the second transparent substrate exists within the variable range of the refractive index of the liquid crystal. do it. This principle will be described with reference to FIG. The refractive index of the liquid crystal material is n
1. The refractive index of the second transparent substrate is n2, and the refractive index of air is n.
3, the angle of the bonding interface between the liquid crystal material and the second transparent substrate is θ0, and the refraction angle to the second transparent substrate at the bonding interface is θ.
1. If the emission angle from the second transparent substrate to the air is θ2, the following relational expression is obtained.

N1 sin θ1 = n2 sin θ2 (Equation 3) n2 sin (θ1-θ2) = n3 sin θ3 (Equation 4) The values of individual parameters are substituted into the above equation. The refractive index of a typical liquid crystal generally used changes in a range of 1.4 to 1.7 by applying a voltage. Assuming that polyvinyl chloride is used as the material of the second transparent substrate, and the inclination of the taper used in the evaluation is 30 degrees, the refractive index of polyvinyl chloride is 1.55, and each parameter is as follows. Become.

Θ0 = 30 n1 = 1.4 to 1.7 n2 = 1.55 n3 = 1 (air) By substituting the maximum value 1.7 and the minimum value 1.4 for the value of n1,
The following value is obtained for θ2.

Θ2max = −5.7 degrees θ2min = 5.0 degrees As described above, it is possible to swing right and left five degrees with respect to the normal line of the second transparent substrate. The values of θ2max and θ2min can be further increased by changing the taper angle θ0. Materials that can be used for the second transparent substrate include acrylic resin (n = 1.5), polystyrene (n = 1.6), and polyamide (n = 1.5 to
1.6) can be used.

However, as shown in FIGS. 3 and 5, when the inclination of the taper is large and the distance between the electrodes of the liquid crystal is largely different, the distribution of the electric field intensity applied to the liquid crystal is large, and the refractive index of the liquid crystal is large. And the direction of refraction becomes non-uniform.

There are two approaches to this solution. 1
First, instead of forming a transparent electrode on a tapered surface, a transparent common electrode is formed on a flat surface, and a taper is formed on the transparent electrode, so that the electric field is evenly applied to both the tapered material and the liquid crystal material. Take it. At this time, the taper material may be selected for the distribution of the dielectric constant.

The dielectric constant of a general TN liquid crystal is approximately 3.3 with respect to a direction perpendicular to the direction of liquid crystal molecules, and the above-mentioned resin for a transparent substrate is made of acrylic resin (3.0) and polystyrene (n = 2.5), polyamide (3.4) and polyvinyl chloride (3.25).

Polyamide (3.4), polyvinyl chloride (3.25), and the like can match the liquid crystal.

Another method is to shorten the period of the taper. According to this method, the difference in the distance between the liquid crystal and the counter electrode can be reduced, and the gradient of the electric field strength can be reduced.

One example is shown in FIG. Next, a second embodiment of the direction change element will be described with reference to FIG.
FIG. 7 shows a direction change element that can change the direction of transmitted light by a periodic structure instead of reducing the period of the taper of the second transparent substrate. Due to a periodic groove structure called a grating, light can be diffracted to change the traveling direction.

However, light diffracted by the periodic groove structure generally occurs on both sides symmetrically with respect to the incident direction, and thus causes crosstalk. Therefore, if a periodic structure having a step in one direction is used as shown in FIG. 6, the diffracted light has only one direction component if the period of the step is reduced. Such a periodic structure is called binary optics, and can be formed by a multiple exposure process using an exposure apparatus called photolithography. This diffraction is shown in FIGS.
It is possible to make the diffraction angle larger than the refraction at the interface shown by.

The bending of light by the diffractive optical element follows the law of diffraction. Here, n is the refractive index of the medium on the light incident side with respect to the diffraction surface, θ is the incident angle, n ′ · θ ′ is the refractive index and the outgoing angle of the medium on the outgoing side, m is the order of the diffracted light, and λ is Wavelength, p
Is the pitch of the diffraction surface.

N sin θ−n ′ sin θ ′ = mλ / p (Equation 5) Assuming that the incident angle θ is 0 degree and the order m of the diffracted light is 1, the above equation is as follows.

Sin θ ′ = λ / n ′ · p (Equation 6) θ ′ = sin ⁻¹ (λ / n ′ · p) (Equation 7) Thus, the angle θ ′ is the wavelength of the transmitted light, It is determined by the refractive index of the medium and the pitch of the diffraction surface. here,
Assuming that the incident angle θ is 0 degree, ns on the left side of (Equation 5)
The value of inθ becomes 0, and the diffraction direction does not depend on the refractive index on the incident side. However, due to the difference between the refractive index n on the incident side and the refractive index n ′ on the output side, the direction of the angle of diffraction is It is known to reverse.

That is, (Equation 7) shows that the refractive index n ′ of the material (liquid crystal) on the emission side changes from a small value to a large value with respect to the refractive index n of the material on the incident side (substrate side), and thus, is positive or negative. The values are opposite, indicating that the values change to both sides with respect to the angle of incidence.

The direction conversion using refraction and diffraction has been described above, but all have wavelength dependence. When the transmissive liquid crystal element has three colors of red (R), green (G), and blue (B), the chromatic aberration increases as the conversion direction is increased.
In order to eliminate the chromatic aberration, the periodic structure of the taper or binary optics may be optimized for each of R, G, and B.

FIG. 8 is a schematic configuration diagram of a three-dimensional display device in which an illumination light source, a parallel conversion element, a liquid crystal element, and a direction conversion element are superimposed. FIG. 8 does not show a camera for obtaining the position information of the observer, but detects the position information of the observer in advance.

When the observer is present at the position of the observer 1, the voltage applied to each line of the direction change element is changed by the controller, and the odd and even pixels (parallax corresponding to the right eye and the left eye) of the liquid crystal element are changed. The light beam direction is moved to the right and left eye positions of the observer corresponding to (image). In addition, when the position of the observer changes and is at the position of the observer 2, the voltage applied to each line of the direction change element is changed so that the light beam direction moves in the direction indicated by the dashed line.

As described above, according to this embodiment, the illumination light in a random direction can be converted into substantially parallel illumination light by the parallel conversion element, and the substantially parallel illumination light is applied to the liquid crystal element. In addition, the light beam transmitted through the liquid crystal element can be changed in the output direction for each pixel by the polarization conversion element, and can be made incident on both eyes of the observer.

Further, by changing the output direction of the light beam in accordance with the change in the position of the observer, a stereoscopic image can be viewed without wearing glasses without depriving the observer of the degree of freedom.

[0038]

As described above, the present invention has the following effects.

1. The parallel conversion element can convert illumination light in a random direction into substantially parallel illumination light.

2. The illumination light is irradiated on the liquid crystal element in a substantially parallel manner, and the light transmitted through the liquid crystal element is polarized by the polarization conversion element.
The emission direction can be changed for each pixel so that the light is incident on both eyes of the observer.

3. Furthermore, by changing the output direction of the light beam in accordance with the change in the position of the observer, a stereoscopic image can be provided without wearing glasses without depriving the observer of the degree of freedom.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of a stereoscopic display device of the present invention.

FIGS. 2A and 2B are views showing a polarization conversion element according to the present embodiment.

FIG. 3 is a diagram showing a direction change element according to the embodiment;

FIG. 4 is a diagram showing the principle of the same-direction conversion.

FIG. 5 is a view showing a direction changing element when the refractive index is changed.

FIG. 6 is a diagram showing a second direction change element in the present embodiment.

FIG. 7 is a diagram showing a third direction change element according to the present embodiment;

FIG. 8 is a diagram illustrating a principle of providing a parallax image to an observer according to the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Illumination light source 2 Parallel conversion element 3 Liquid crystal element 4 Direction conversion element 5 Camera 6 Camera 7 Controller 8 Observer

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification code FI G09F 9/00 361 G09F 9/00 361 (72) Inventor Katsumi Adachi 1006 Kazuma Kazuma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 72) Inventor Kenya Uomori 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (18)

[Claims] An illumination light source for irradiating illumination light, a parallel conversion element for converting the illumination light into substantially parallel light, a transmission type liquid crystal element, and a direction conversion element for changing a traveling direction of the light, A three-dimensional display device, comprising: irradiating illumination light converted into parallel light by a conversion element to the transmissive liquid crystal element, and converging the transmitted parallel light to a specific position using the direction conversion element. 2. A parallel conversion element comprising two sets of cylindrical lens plates and a slit disposed at an intermediate position between the two sets of cylindrical lens plates. Light incident on the parallel conversion element is condensed by a first cylindrical lens plate. 2. The three-dimensional display device according to claim 1, wherein only light transmitted through the slit is converted into parallel light by the second cylindrical lens plate. 3. A mirror, wherein a side of the slit used for the parallel conversion element facing the first cylindrical lens plate is a mirror, and illumination light not transmitted through the slit is returned to the illumination light source by the mirror. 3. The stereoscopic display device according to 2. 4. A parallel conversion element comprising two sets of microlens plates and a pinhole plate arranged at an intermediate position between them, and light incident on said parallel conversion element is condensed by a first microlens plate. The stereoscopic display device according to claim 1, wherein only light transmitted through the pinhole plate is converted into parallel light by a second microlens plate. 5. A mirror, wherein a side of the slit used for the parallel conversion element facing the first microlens plate is a mirror, and illumination light not transmitted through the slit is returned to the illumination light source by the mirror. 4. The stereoscopic display device according to 4. 6. The three-dimensional display device according to claim 1, wherein the parallel conversion element comprises a hologram element for converting random light into parallel light. 7. A three-dimensional display device according to claim 1, wherein the parallel conversion element is a combination of a hologram element and the parallel conversion element according to any one of claims 1 to 5. 8. A first transparent substrate having a transparent electrode in which a direction change element is divided, and a transparent electrode which is tapered in one direction to face the divided transparent electrode, and has a thickness inclined in one direction. 2. The three-dimensional display device according to claim 1, wherein a liquid crystal is arranged in a gap between the second transparent substrate and the second transparent substrate. 9. A first transparent substrate having a transparent electrode in which a direction change element is divided, and a transparent electrode which is inclined in one direction in a stepwise manner facing the divided transparent electrode and has a transparent electrode over the entire surface. 2. The three-dimensional display device according to claim 1, wherein a liquid crystal is arranged in a gap between the second transparent substrate and the second transparent substrate. 10. A gap between a first transparent substrate having a transparent electrode in which a direction change element is divided and a second transparent substrate having a grating facing the divided transparent electrode and having a transparent electrode on the entire surface. The three-dimensional display device according to claim 1, wherein a liquid crystal is arranged. 11. A first transparent substrate having a transparent electrode in which a direction change element is divided, and a second transparent substrate having a stepwise periodic structure opposed to the divided transparent electrode and having a transparent electrode on the entire surface. 2. The three-dimensional display device according to claim 1, wherein a liquid crystal is disposed in a gap between the three-dimensional display device. 12. The direction of transmitted light is changed for each of the divided transparent electrodes by changing the voltage applied to each of the divided transparent electrodes of the first transparent substrate of the direction change element. 12. The method according to claim 8, wherein:
The stereoscopic display device according to any one of the above. 13. The divided transparent electrodes of the first transparent substrate of the direction change element are divided into odd and even pairs, and voltages applied to the odd and even pairs of transparent electrodes are changed independently. 13. The three-dimensional display device according to claim 8, wherein the direction of transmitted light is divided into two sets. 14. The divided transparent electrodes of the first transparent substrate of the direction change element are divided into odd and even sets, and each of the odd and even sets intersects linearly at a specific distance from the display device. The stereoscopic display device according to any one of claims 8 to 12, wherein a voltage applied to each of the odd-numbered and even-numbered transparent electrodes is controlled. 15. An illumination light source that emits illumination light, a parallel conversion element that converts the illumination light into substantially parallel light, a transmissive liquid crystal element that transmits the converted parallel light, and a transmissive liquid crystal element. A display element having a direction changing element for changing the traveling direction of the emitted light, a three-dimensional position detector for detecting a three-dimensional position of the detected part, and an output from the display element at a position detected by the three-dimensional position detector A stereoscopic display device comprising: a controller that performs control so as to converge an image to be reproduced. 16. A three-dimensional position detector comprising two cameras, three-dimensionally detecting an observer's face or eye position, and controlling a direction outputted from a direction change element of a display element by a controller. The stereoscopic display device according to claim 15, wherein the three-dimensional display device converges on the position of the observer detected by the detection. 17. The liquid crystal display device according to claim 1, wherein the change in the refractive index of the liquid crystal used in the direction change element changes in the range of 1.4 to 1.7 with respect to the polarized light. 3D display device. 18. A material used for the second transparent substrate used in the direction change element is made of acrylic resin (PMMA), polyamide, polyvinyl chloride or polystyrene. Item 13. The stereoscopic display device according to any one of Items 8 to 11.