JP2002372701A - Picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a picture display device in which the utilization efficiency of the light of illumination rays is enhanced by enhancing a switching speed for deflecting optical paths and reducing turbulence of a picture. SOLUTION: In this picture display device, electrode arrays are formed at least on the substrate of one side of two sheets of transparent substrates in correspondence with the pitch of pixels and a liquid crystal layer of which the refractive index profile can be controlled by applying a voltage between the two sheets of substrates is provided and the display device displays a picture while doubling the apparent number of pixels by displaying a picture pattern whose display position is shifted in accordance with deflection states of optical paths for every sub-field while deflecting optical paths of exit rays of light from respective pixels by changing the voltage application state to the electrode arrays in synchronization with a display driving signal while setting the voltage to have a waveform which is different at the time of changing over sub-fields and in displaying sub-fields.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device for observing an image by enlarging a small image display element having a plurality of pixels whose light can be controlled in accordance with image information with a lens, and more particularly to an image display device having an optical axis. A pixel shift type image display device in which the number of actual pixels is increased by shifting at a higher speed is suitable for application to an electronic display device such as a projection display or a head mounted display.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 6-32432 discloses a technique for apparently multiplying the number of images on an image display element to display a high resolution image.
No. 0, "Image display device, resolution improvement method of image display device, imaging method, recording device and reproducing device". This technique apparently improves the resolution of a display image without increasing the number of pixels of an image display device such as an LCD. For this purpose, an optical path is provided between an image display device and an observer or a screen on which an image is displayed by each of a plurality of pixels arranged in a vertical direction and a horizontal direction emitting light according to a display pixel pattern. An optical member that changes for each field is provided. In addition, a display pixel pattern in a state where the display position is shifted according to the change of the optical path is displayed on the image display device for each field. By configuring the image display device in this way, portions having different refractive indices are alternately provided for each field of image information.
This change in the light path is made by appearing in the light path between the image display device and the observer or screen.

In the "projection display device" disclosed in Japanese Patent Laid-Open No. Hei 10-20242, a pixel shift is performed by combining an image display element and a microlens array and vibrating the microlens array. When using a liquid crystal microlens array with a circular hole pattern and selectively applying a voltage in synchronization with a field signal to change the lens formation position, change the focal length in the optical axis direction. Is relatively easy, but it is not possible to change the condensing position in the arrangement direction of the lens array. Therefore, in the "optical coupler" disclosed in Japanese Patent Application Laid-Open No. H11-109304, which is a technique for controlling the condensing position in the direction of the lens array plane, a liquid crystal microlens in which circular hole-shaped pattern electrodes are arranged in an array is used. In addition, a lens with a variable focal length is used, the light coupling efficiency of the optical interconnection element is made variable, and the focal position can be controlled by the divided electrodes. However, in this optical coupler, when a liquid crystal lens having divided electrodes is formed in an array, the electrode wiring becomes complicated, so that the interval of lens formation must be set relatively wide. It is suitable when the installation interval is relatively wide such as optical fiber coupling, but when the interval is relatively narrow like the pixel pitch of the image display device, the aperture ratio of the lens forming portion becomes small. Would.

Also, in US Pat. No. 6,082,862, "a projection system using a holographic optical element capable of electrical switching", the angle of an optical path is changed at high speed by a holographic optical element made of a liquid crystal material, and a display image is displayed. Is shifted at high speed.

As a technique for deflecting the optical path, there is a "light beam deflecting device" disclosed in JP-A-10-133135. According to this technique, a translucent piezoelectric element disposed on a traveling path of a light beam, a transparent electrode provided on a surface of the piezoelectric element, and a light-beam incident surface and a light-beam exit surface of the piezoelectric element. Voltage applying means for applying a voltage to the piezoelectric element via an electrode to change the optical path length of the light beam and deflect the optical axis of the light beam, eliminating the need for a rotating mechanical element, miniaturizing the whole, and achieving high precision.・ Provides a light beam deflecting device that can achieve high resolution and is not easily affected by external vibration.

[0006] Further, as a light deflection technique using a liquid crystal,
“LIGHT SCANNER EMPLOYING A NEMATIC LIQUID CRYSTA
L ”(IBM Technical Disclosure Bulletin, Vol. 15, N
o.8 (1973)), changing the orientation angle of nematic liquid crystal to bend the optical path of linearly polarized light, and “LARGE-ANGLE”
BEAM DEFLCTOR USING LIQUID CRYSTAL ”(ELECTRONICSL
ETTERS, Vol.11, No.16 (1975)), there is a technology to bend the optical path of linearly polarized light by applying a non-uniform electric field to the nematic liquid crystal. However, all of these technologies are single beam deflectors. It is not applicable to the pixel shift of a two-dimensional image.

[0007] As a technique related to a liquid crystal microlens, "Liquid crystal microlens" (Oplus E, Vol. 20, No.
10 (1998)), the focus can be moved in directions other than the optical axis direction by making the electric field distribution asymmetric using a liquid crystal microlens having an electrode division structure. This technique is suitable for controlling the deflection direction of a single beam two-dimensionally. However, in the case of arraying, the electrode wiring becomes complicated, so that an array of beams such as an image display element is used. It is not suitable for application to deflection devices. Patent No. 0316774
In the “Liquid Crystal Microlens” of JP-A No. 4 (1994), a polymer is formed by photopolymerization in a nematic liquid crystal, which has a memory property and can change lens characteristics.

[0008]

As an image display device for observing an image obtained by enlarging an image display element having a plurality of pixels whose light can be controlled in accordance with image information with a lens, a front projector, a rear projector, and a head mounted device Widely used for product names such as displays. This image display element includes a CRT, a liquid crystal panel, a DM
D (trade name of Texas Instrument Co., USA) is used as a product, and inorganic EL, inorganic LED,
Organic LEDs are also being studied. Also, instead of observing an image obtained by enlarging a small image display element with a lens,
As the image display device for observation at the same magnification, the above-mentioned CR is used.
In addition to T, liquid crystal panel, inorganic EL, inorganic LED, organic LED, plasma display, fluorescent display tube, etc. are used as commodities, and FED (field emission display), PALC (plasma addressing display), etc. have been studied. I have. These are broadly classified into two types, a self-luminous type and a spatial light modulator type, each of which has a plurality of pixels capable of controlling light.

A problem common to these image display devices is to increase the resolution, that is, to increase the number of pixels, and to provide an HDTV having about 1000 scanning lines for broadcast display.
Scan line 2000 for high resolution display of a workstation computer is already commercialized.
About this developed product has been announced by using a liquid crystal panel technology (2048 QSXGA by IBM Japan at the '98 Flat Panel Display Exhibition, 2400 QUXGA by Toshiba at the '99 Electronic Display Exhibition, etc.). However, increasing the number of pixels lowers the yield of the liquid crystal panel, and also increases the cost, lowers the brightness and contrast due to the decrease in the aperture ratio,
And power consumption was increasing.

To solve these problems, Japanese Patent Application Laid-Open No. 4-113
Japanese Patent Application Publication No. 308, Japanese Patent Application Laid-Open No. 5-289004, Japanese Patent Application Laid-Open No. 6-324320, and the like disclose an image display apparatus that performs interlaced display having twice the number of pixels using a single image display element. ing. Also, Japanese Patent Laid-Open No. 7-360
No. 54 discloses a display device having four or more times the number of pixels using a single image display element. These are so-called pixel shift methods in which the optical path emitted from the image display element is changed at high speed in a time-division manner to increase the apparent number of pixels. JP-A-6-324320 describes a mechanism for changing an optical path, such as a mechanism for combining an electro-optical element and a birefringent material, a lens shift mechanism, a variangle prism, a rotating mirror, and a rotating glass. JP-A-104278 describes means for moving a wedge prism. Among these, the combination of a member exhibiting an electro-optic effect and a birefringent crystal is a technique known as a deflection means conventionally used as a light distribution and optical switch in the field of optical communication, but has a relatively large birefringence. Crystals are required, which increases the equipment cost. Also, as a lens shift mechanism, that is, as a driving system for reciprocating motion, a voice coil, a piezoelectric element, a bimorph, a step motor, a solenoid coil, etc. are described, but when reciprocating at about several tens to several hundreds Hz, The generation of vibration and sound becomes a problem. Also, the vari-angle prism has a problem of vibration and noise because the substrate reciprocates.

Japanese Patent Application Laid-Open No. Hei 5-313116 describes a pixel shift method in which an image display element itself is swung at a high speed by a distance smaller than a pixel pitch. In this method, the optical system is fixed and various aberrations are less generated, but since the image display element itself needs to be translated accurately and at high speed, accuracy and durability of the movable part are required.
Vibration and sound become problems.

Japanese Patent Application Laid-Open No. 10-133135 proposes a system in which a light-transmitting piezoelectric element is sandwiched between transparent electrodes, and the optical path is shifted by changing the thickness by applying a voltage. A large transparent piezoelectric element is required, which increases the cost of the device.

JP-A-6-208345 and JP-A-6-208345
JP-A-324320 describes a method of changing the shift amount of the optical path by switching the thickness and inclination angle of a transparent plate-like refraction plate. As a switching method, the thickness of the refraction plate of one circular rotating body is described. A configuration in which the sheath angle is partially different is illustrated. However, a single circular rotator shifts the optical path only in the one-dimensional direction, and has a problem that the entire optical system becomes large because of the relatively large circular rotator.

[0014] On the other hand, Japanese Patent Application No. 2000-
No. 3,520,090, “image display device” uses a Bragg diffraction element made of polymer dispersed liquid crystal as an optical path deflecting means, and is characterized by high-speed response based on a fine liquid crystal droplet structure. However, there are problems that the wavelength dependence of the deflection angle is large and that a pixel reduction element is separately required to improve the light use efficiency.

[0015] Further, Japanese Patent Application No. 2001-210, filed by the present applicant.
In the "image display device" of No. 12397, the optical path is shifted by an electro-optical effect with a relatively simple electrode configuration without providing a mechanical vibration mechanism, and apparently without lowering the light use efficiency. Has proposed an image display device capable of obtaining a high-definition image by multiplying pixels of the above. In this image display device, a liquid crystal microlens that forms a lens-shaped refractive index distribution and can electrically control a focal position is used, and by switching a voltage application position, a light path from a pixel is condensed, and The focusing position can be shifted. That is, an efficient pixel shift function and a pixel reduction function can be compatible with one element, and even if an image display element having a high aperture ratio and a large pixel pitch is used, the pixel increase without reducing the light use efficiency is achieved. The resolution can be increased by doubling. Here, the “pixel shift” is as shown in FIG.
This technique shifts the optical path of light (projection light) from the light valve pixel temporally so that the observer can see and double the apparent pixel.
Is a technique for reducing the light from each pixel of the light valve to a desired ratio with respect to the pixel arrangement pitch. The pixels arranged in the light valve usually have a narrow interval, that is, a wide aperture, to increase the light use efficiency of the illumination light. If the light projected from the light valve is simply shifted in this state in this state, the adjacent pixels may overlap and become difficult to see (FIG. 23). Therefore, it is desirable to reduce the light from each pixel of the light valve to a desired size (pixel reduction) before shifting the pixels. For example, when doubling the number of pixels by performing a pixel shift, it is preferable to reduce the ratio to approximately 1/2. However, in this image display device, the voltage application state to the electrode array corresponding to the pixel pitch is, as shown in FIG. 4, a so-called On mode in which a predetermined voltage (3 V in the embodiment) is applied and a mode in which no voltage is applied. Since it is impossible to cope with high-speed switching because it is / Off 2 value, it is desirable to adopt a dual frequency driving method or the like for applications requiring higher speed switching. There is a problem such as heat generation.

An object of the present invention is to provide an image capable of displaying a high-resolution image using a low-resolution image display element by performing a predetermined optical path deflection for each subfield in view of the above-described problem. It is an object of the present invention to provide an image display device capable of improving the switching speed of optical path deflection, reducing image disturbance, and improving the light use efficiency of illumination light.

[0017]

In order to solve the above problems, an image display apparatus according to a first aspect of the present invention is an image display apparatus in which a plurality of pixels capable of controlling light in accordance with image information are two-dimensionally arranged. An element, a light source and an illumination device for illuminating the image display element, an optical device for observing an image pattern displayed on the image display element, and a display for forming an image field by a plurality of time-divided subfields A driving unit, and an optical path deflecting unit that deflects an optical path of light emitted from each pixel, and displays an image pattern in which a display position is shifted according to a deflection state of the optical path for each subfield. An image display apparatus for displaying an image by multiplying an apparent number of pixels of an image display element, wherein the optical path deflecting unit is formed on two transparent substrates and at least one of the substrates in correspondence with a pixel pitch. Electrode array, a liquid crystal layer capable of controlling the refractive index distribution by applying a voltage between these two substrates, and changing the voltage application state to the electrode array in synchronization with the display driving means at the time of subfield switching. An optical path deflecting drive unit is provided, which is configured to set and change a waveform to be different from that during subfield display.
Therefore, at the time of subfield switching, a voltage enabling high-speed operation of the liquid crystal is applied, and at the timing approaching a predetermined liquid crystal distribution state, the voltage waveform is switched to a subfield display voltage at which the liquid crystal distribution state is maintained. Switching can be achieved, and image disturbance due to subfield switching can be improved, and light use efficiency can be improved.

According to a second aspect of the present invention, in the image display device according to the first aspect, the optical path deflection driving means includes:
The absolute value of the applied voltage at the time of subfield switching is set to be larger than the absolute value of the voltage at the time of subfield display. Therefore, the liquid crystal can operate at high speed by increasing the absolute value of the applied voltage at the time of subfield switching.

According to a third aspect of the present invention, there is provided an image display device in which a plurality of pixels capable of controlling light in accordance with image information are two-dimensionally arranged, a light source for illuminating the image display device, and an illumination. A device, an optical device for observing an image pattern displayed on the image display element, a display driving means for forming an image field by a plurality of sub-fields divided in time, and an optical path of light emitted from each pixel. Light path deflecting means for deflecting the light, and displaying an image pattern in a state where the display position is shifted according to the deflecting state of the light path for each subfield, thereby increasing the apparent number of pixels of the image display element. An image display device, wherein the optical path deflecting means, two transparent substrates, an electrode array formed on at least one of the substrates corresponding to the pixel pitch,
A liquid crystal layer whose refractive index distribution can be controlled by applying a voltage between these two substrates, and a voltage application state to the electrode array in synchronism with the display driving means. Optical path deflection driving means for alternately switching and applying a voltage in synchronization with the switching voltage, wherein the low voltage side of the switching voltage is an AC voltage having an amplitude (non-zero) equal to or smaller than a liquid crystal rising threshold voltage. It is characterized by the following. In the case where the optical path deflecting means made of nematic liquid crystal is driven by the strength of the electric field of the AC voltage, the amplitude of the switching voltage on the low voltage side is conventionally set to the complete OFF state, that is, the state where no voltage is applied. Compared to changing from a state where no voltage is applied to a state where a high voltage is applied, setting the voltage in advance near the liquid crystal rising threshold voltage can speed up liquid crystal inversion and achieve high-speed operation with respect to optical shift. To be peeled off.

According to a fourth aspect of the present invention, there is provided an image display device in which a plurality of pixels capable of controlling light in accordance with image information are two-dimensionally arranged, a light source for illuminating the image display device, and an illumination. A device, an optical device for observing an image pattern displayed on the image display element, a display driving means for forming an image field by a plurality of sub-fields divided in time, and an optical path of light emitted from each pixel. Light path deflecting means for deflecting the light, and displaying an image pattern in a state where the display position is shifted according to the deflecting state of the light path for each subfield, thereby increasing the apparent number of pixels of the image display element. An image display device, wherein the optical path deflecting means, two transparent substrates, an electrode array formed on at least one of the substrates corresponding to the pixel pitch,
A liquid crystal layer whose refractive index distribution can be controlled by applying a voltage between these two substrates, and a voltage application state to the electrode array in synchronization with the display driving means is set to a subfield display timing between adjacent electrode arrays. An optical path deflection driving means for alternately switching and applying a voltage in synchronization with each other, wherein the optical path deflection driving means forms a voltage application state in which the AC phase is inverted by approximately 180 degrees corresponding to the pixel pitch of the electrode array. It is characterized by doing. Therefore, the switching speed of the optical path deflection can be increased by utilizing the horizontal electric field from the adjacent electrode array to align the liquid crystal molecules from the normal direction to the in-plane direction of the substrate surface.

According to a fifth aspect of the present invention, in the image display device according to any one of the first to fourth aspects, the optical path deflecting means corresponds to the pixel pitch corresponding to the pixel pitch on both substrates. And the voltage application state of the optical path deflection drive means generates an AC voltage between the electrode arrays that do not overlap with the liquid crystal layer interposed therebetween. Therefore, only the liquid crystal molecules contributing to the optical path deflection are changed in orientation, and the amount of change in the orientation of the liquid crystal molecules can be reduced, so that the switching speed of the optical path deflection can be increased.

According to a sixth aspect of the present invention, in the image display device according to any one of the first to fourth aspects, the optical path deflecting means is configured to set the electrode array in the liquid crystal layer in accordance with a pixel pitch. And the voltage application state of the optical path deflection driving means is alternately switched and applied to adjacent electrode arrays in synchronization with the subfield display timing. Therefore, pixel reduction is performed favorably, deterioration of image quality can be reduced, and high-speed switching can be performed.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration and operation of an image display device according to the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of the image display device of the present invention. According to FIG. 1, the present image display device includes at least a light source 1, a light source driving unit 2, an illuminating device 3, an image display element 4, a display driving unit 5, an optical path deflecting unit 6, an optical path deflecting driving unit 7, an image display control circuit. 8, a projection lens 9, and a screen 10. As the light source 1, any light source that can turn on / off white or arbitrary color light at high speed can be used. For example, LE
A combination of a D lamp, a laser light source, a white lamp light source, and a shutter can be used. Lighting device 3
Is for uniformly irradiating the light emitted from the light source 1 to the image display element 4, and includes a fly-eye lens, a diffusion plate 31, a condenser lens 32 and the like. Image display element 4
Is a device for spatially modulating incident uniform illumination light and emitting the light. A transmissive liquid crystal light valve, a reflective liquid crystal light valve, a DMD element, or the like can be used.

The light emitted from the light source 1 under the control of the light source driving means 2 becomes illumination light uniformed by the diffusion plate 31 and critically illuminates the image display element 4 by the condenser lens 32. Here, a liquid crystal light valve which is a transmissive liquid crystal panel is used as an example of the image display element 4. The illumination light spatially modulated by the image display element 4 (liquid crystal light valve) is enlarged as image light by a projection lens 9 and projected on a screen 10. Here, the image light is shifted by an arbitrary distance in the pixel arrangement direction by the optical path deflecting means 6 disposed behind the image display element 4.
In FIG. 1, the optical path deflecting unit 6 is provided immediately after the image display element 4, but the position is not limited to this position.
It may be immediately before zero. However, when the optical path deflecting device 6 is installed near the screen 10, the size of the optical path deflecting means 6, the electrode array pitch, and the like are set according to the screen size and the pixel size at that position. In any case, it is preferable that the shift amount is an integer fraction of the pixel pitch. For example, when performing double image multiplication in the pixel arrangement direction, the pixel pitch is set to １ ／, and when triple pixel multiplication is performed, the pixel pitch is set to ３. Further, when the shift amount is increased by the configuration of the optical path deflecting unit 6, the shift amount may be set to a distance of (integer multiple + 1 / integer) of the pixel pitch.
In any case, by driving the image display element 4 with the image signal of the subfield corresponding to the shift position of the pixel,
As shown in FIG. 2, an apparent pixel multiplication effect is obtained, and a high-definition image having a resolution equal to or higher than the resolution of the used image display element 4 can be displayed.

Here, the terms "subfield", "when subfield is switched" and "when subfield is displayed" in the present invention are defined as follows. Normally, in an image display device such as a liquid crystal projector, images are sequentially rewritten and displayed at a certain cycle, and an image per sheet is called a field. In the present invention, pixels are doubled and displayed by performing an optical path shift in a time-division manner, and an image displayed in a time-division manner is called a subfield. For example, when the number of divisions is 2, that is, when the optical path shift is switched at two positions, an image of one field is formed by two subfields. Also, “at the time of subfield switching” indicates the time during which the optical path is shifted, and “at the time of subfield display” indicates the time during which the optical path shift is completed and one subfield is displayed.

In the image display device shown in FIG. 1, a single-plate transmission type liquid crystal light valve and a light source 1 are used as the image display element 4.
Although a single-color image display device using a single-color LED lamp has been described above, a full-color image can be displayed by mixing three-primary-color images using a three-primary-color light source / illumination device and three image display elements. Also, a full-color image can be displayed by a field sequential method in which a single-plate image display element is illuminated with light of three primary colors in time order. At this time, the light paths from the three color light sources may be mixed and illuminated by a cross prism, or the three primary color lights may be generated in chronological order by combining a white lamp light source and a rotating color filter.

The optical path deflecting means 6 uses a liquid crystal cell whose refractive index distribution can be controlled by applying a voltage. This liquid crystal cell comprises two transparent substrates, an electrode array formed on at least one of the substrates corresponding to the pixel pitch, and a liquid crystal layer whose refractive index distribution can be controlled by applying a voltage between the two substrates. And an optical path deflection driving means 7 for changing the state of voltage application to the electrode array in synchronization with the display driving means 5.
Glass, plastic, or the like can be used as the material of the transparent substrate. As a material of the electrode array, ITO or the like can be used for a transparent electrode, and Al or Cr can be used for a metal electrode. The electrode array is placed on the liquid crystal layer side. When the substrate used has conductivity, the substrate can be used as an electrode. On at least one substrate side, the electrodes are formed in an array corresponding to the pixel pitch. The surface of the electrode in contact with the liquid crystal layer is preferably treated so that liquid crystal molecules are aligned. For the alignment treatment, a normal alignment film such as polyimide used for TN liquid crystal, STN liquid crystal and the like can be used. Further, it is preferable to perform a rubbing treatment or a photo-alignment treatment. Further, an insulating film may be provided on the surface of the electrode.

As the liquid crystal material, a general nematic liquid crystal can be used, but it is preferable that the birefringence Δn and the dielectric anisotropy Δε are large. In particular, it is preferable that the ordinary light refractive index of the liquid crystal material is about 1.5 to 1.6 close to the refractive index of the glass substrate, and the extraordinary light refractive index is as large as about 1.7 to 1.8. The thickness of the liquid crystal layer is set by the thickness of the spacer member between the substrates, and is optimized according to Δn and Δε so as to obtain a desired optical path deflection amount and response speed. The spacer member is preferably provided only on the periphery of the liquid crystal layer so as not to hinder light transmission.

In general, it is preferable to make the subfield switching coincide with the timing of rewriting the image signal of the light valve in terms of light use efficiency and image quality. Since this switching time causes the projected image to move and causes the observer to observe a substantially deteriorated image, measures such as blocking the projection light may be taken, and also from the viewpoint of image display quality. It is preferable to perform the reaction in a short time from the viewpoint of light use efficiency.

On the other hand, in the optical path deflecting means 6, it is necessary to maintain the driving voltage at the time of subfield display in the most appropriate shape for the alignment state of the liquid crystal so that the displayed image does not fluctuate. The subfield switching for changing the state is not particularly limited by this restriction. In consideration of the considerations made by the present applicant, the optical path deflection driving means 7 has a waveform shape suitable for high-speed switching of the liquid crystal alignment state at the time of subfield switching, separately from the voltage for maintaining the above-mentioned alignment state. It has been found that the quality can be further improved.

FIG. 3 is a schematic diagram showing the relationship between a conventional field, subfield, optical path deflecting means, and light valve image signal. A field pulse (FP) and a subfield pulse (SFP) are generated by a controller in the image display device based on the reference clock. FIG. 3 shows a case where there are two subfields. Prior to the subfield display time, the subfield switching time is set, and at this subfield switching time, the light valve rewrite signal is updated, and the light valve display is rewritten. The optical path deflection drive signal indicates a drive waveform of the (n + 1) th electrode array adjacent to the nth electrode array. Conventionally, as shown here, a so-called On / Off 2 value of a mode in which a predetermined (AC) voltage is applied and a mode in which no voltage is applied, which is not suitable for applications requiring higher-speed switching. In the optical path deflection driving means 7 of the present invention, different waveforms are set at the time of subfield switching and at the time of subfield display. In particular, the absolute value of the applied voltage at the time of subfield switching is larger than the voltage absolute value at the time of subfield display. By setting, higher-speed switching becomes possible. For example, as shown in FIG. 17, the absolute value of the applied voltage at the time of subfield switching is set to be larger than the absolute value of the voltage at the time of subfield display. However, it is preferable to change the applied voltage at an early stage of switching the subfield. For example, it is better to change the applied voltage in a shorter time as the voltage difference from the display time is larger. This is because if the time is taken longer than the proper time, the liquid crystal molecules move more than the alignment state of the liquid crystal set at the time of subfield display, and it may take time to be stabilized. . Even when a DC voltage is used instead of an AC voltage, a similar effect can be obtained by increasing the amplitude at the time of subfield switching.

FIG. 4 is a diagram for explaining the operation of the optical path deflecting means 6. FIG. 4A schematically shows a liquid crystal alignment state when the liquid crystal cell is not operated. In the absence of an electric field, a homogeneous alignment treatment is performed so that the liquid crystal molecules are parallel along the substrate. Here, it is assumed that the alignment process is performed such that the major axis of the liquid crystal molecules is in the horizontal direction of the drawing. As the characteristics of the liquid crystal shown here, it is assumed that the liquid crystal has a dielectric constant characteristic in which the long axis direction of the liquid crystal molecules is oriented with respect to the direction of the electric field, and the refractive index for extraordinary light is larger than the refractive index for ordinary light.
Electrode lines are formed in an array on the upper transparent substrate. In this example, two electrode lines with a wide interval are set as one set and correspond to one pixel. The portion where the distance between the electrodes is small corresponds to the boundary between pixels. On the other hand, the lower electrode is formed on the entire surface, but may be an array electrode symmetrical to the upper substrate. At this time, the optical path deflection driving means 7 alternately switches the voltage applied to the electrode arrays adjacent to each other in synchronization with the subfield display timing. The low voltage side of the switching voltage is a liquid crystal rising threshold voltage VRth.
An AC voltage having the following amplitude V1 (V1 ≠ 0) is used.

Here, the liquid crystal rising threshold voltage VRth and the liquid crystal falling threshold voltage VDth are defined as follows.
That is, in the shaded electrode line of FIG.
When a voltage was gradually applied from a state in which no voltage was applied to the electrode array, the refractive index of linearly polarized light passing through this portion began to change due to a change in the orientation of the liquid crystal located below the electrodes. Saturates. At this time, the change rate of the refractive index obtained from the difference in the refractive index is 10%.
Is defined as a liquid crystal rising threshold voltage VRth, and a voltage corresponding to a change rate of 90% is defined as a liquid crystal falling threshold voltage VDth (see FIG. 5).

For example, in FIGS. 4 and 9, the shaded electrode array applies a high voltage V2 and the unshaded electrode array applies V1. I have. Conventionally, V1 was not set and no voltage was applied, but setting V1 can increase the speed. When V1 is applied, the alignment state of the liquid crystal molecules is slightly changed by the voltage (in FIGS. 4 and 9, the liquid crystal molecules are slightly tilted from the state parallel to the substrate), but the liquid crystal molecules are set to such a degree that the actual light shift does not cause image deterioration. Is preferred. Also, when using a DC voltage instead of an AC voltage,
A similar effect can be obtained by reversing the polarity. Note that V1 is preferably set to be equal to or higher than the liquid crystal falling threshold voltage VDth.

Now, the operation state 1 (see FIG. 4B)
The figure shows a case where a voltage equal to or higher than the liquid crystal falling threshold voltage VDth is applied only to the shaded electrode lines. In the electrode part where voltage is applied, it is oriented vertically by the electric field,
The electrode portion without application remains horizontally oriented. The distribution of the alignment direction due to the non-uniform electric field inside the liquid crystal cell generates a refractive index distribution for extraordinary light. When linearly polarized light having a plane of polarization parallel to this drawing is incident, the effective refractive index decreases as the long axis of the liquid crystal molecules is oriented perpendicular to the substrate, and the refraction as shown by the solid line (state 1) in FIG. Affected by rate distribution. The polarized light that has entered the central part of the pixel in this operation state 1 is deflected to the left side in the figure by the refraction effect due to the gradient of the refractive index.

Next, when the electrode to which the voltage is applied is switched as in the operation state 2 (see FIG. 4C), the alignment state of the liquid crystal molecules also changes, and the refractive index distribution changes as shown by the broken line in FIG. I do. The polarized light that has entered the central part of the pixel in the operation state 2 is deflected to the right in the drawing by the lens effect due to the gradient of the refractive index. The change speed at this time is optimized by the physical properties of the liquid crystal material and the electric field. In the pixel shift method, since the subframe time is preferably 10 msec or less, a response time of several msec or less is required. Image display element 4 (liquid crystal light valve) for operating state 1 and operating state 2
By switching in accordance with the drive timing of the sub-frame to be displayed, an apparent pixel multiplication effect can be obtained. FIG. 7 is a schematic diagram for explaining the operation of the image display element when light emitted from four pixels of the image display element 4 (liquid crystal light valve) enters the liquid crystal cell from below the figure. For example, when four pixels are in the states A, C, E, and G in the first sub-frame, respectively, when the liquid crystal cell is set to the operation state 1 in FIG. 4, light from each pixel is deflected to the right. In the second sub-frame, the four pixels are B,
When the liquid crystal cell is switched to the operation state 2 in synchronization with the states of D, F, and H, light from each pixel is deflected to the left. The light traveling obliquely in the liquid crystal cell is apparently lined up with A, B, C, D, E, F, G, and H on the liquid crystal cell by switching the subframe from several tens Hz to several hundred Hz. There are eight pixels. Further, an optical element may be provided so that the light emitted from the liquid crystal cell becomes parallel to the optical axis of the projection optical system. FIG. 8 is a schematic diagram showing the arrangement of the optical path deflecting means 6 of the present invention. The (transparent) electrode array 61 is formed in a line in the vertical direction in the drawing. When the light emitted from the image display element 4 is linearly polarized light in the horizontal direction in the drawing, the entire image display element 4 can be pixel-shifted in the horizontal direction in the drawing. Therefore, a high-definition image display device having a high resolution in the horizontal direction of the screen can be realized with a relatively simple electrode configuration.

When only the direction of light is changed by the liquid crystal cell as shown in FIG. 7, it is necessary to adjust the size of the pixel on the incident side to be small in accordance with the size of the pixel on the emitting side. As a method of adjusting the pixel size on the incident side, a method of regulating an optical path through a mask having an opening corresponding to a pixel position, a method of condensing light with a microlens array corresponding to a pixel position, and the like can be applied. However, the method using a mask lowers the light use efficiency, and the cost increases if a microlens array is newly provided. Therefore, in another configuration of the present invention, one liquid crystal cell has both the function of reducing the pixel size and the function of deflecting the optical path.

FIG. 9 schematically shows a liquid crystal light deflecting element having a pixel reduction function. The basic configuration such as the material used and the processing method is the same as that of FIG. 4, but the pitch and width of the electrode array are different. In FIG. 9, an electrode array is formed on the upper substrate at the same pitch as the pixel pitch of the image display element 4. The width of each electrode is not particularly limited, but is set according to a desired electric field intensity distribution in the liquid crystal cell. Operating state 1
In FIG. 9A, a voltage equal to or higher than a threshold is applied alternately to electrodes at regular intervals. By this voltage application, a refractive index distribution is generated in the liquid crystal layer as described above. The distance between the electrodes to which the voltage is applied is larger than that in FIG.
It has a convex lens shape with a relatively large pitch as shown by the solid line of 0.

In this case, the feature is that one convex lens effect is given to two pixels of the image display element 4. FIG. 11 is an explanatory diagram for explaining the image reduction effect and the image shift effect by the liquid crystal lens. Indicated. In the present invention, the size of the incident side pixel that enters the liquid crystal cell is set relatively large. For example, when the state of A, C, E, and G is displayed as the first sub-frame on the four pixels when the liquid crystal cell is in the operation state 1, when A, C, and E are shown by the solid line refractive index distribution in FIG.
And G are respectively reduced. At this time, the pixel pitch is not constant, as shown by the output-side pixel indicated by the solid line in the upper part of FIG. Next, when the electrodes to which a voltage is applied are switched as in the operation state 2 (see FIG. 9B) in accordance with the display timing of the second sub-frame, the refractive index distribution switches as shown by the broken line in FIG. . Here, when the states of B, D, F, and H are displayed as the second subframe, the reduced pixel moves to the position indicated by the broken line in the upper part of FIG. By switching the sub-frame from several tens Hz to several hundreds Hz, eight pixels appearing irregularly as B, A, C, D, F, E, G and H on the liquid crystal cell.

The sub-field image data is corrected and displayed on the image display element 4 so that the display image due to such an irregular pixel shift is formed as a normal image. With this configuration, with a simple electrode configuration, a single liquid crystal cell can achieve both the pixel reduction effect by condensing the liquid crystal lens and the pixel shift effect by switching the liquid crystal lens formation position.
Therefore, it is possible to prevent a decrease in light use efficiency with a simple element configuration.

In the configuration shown in FIG. 11, since the optical path is non-parallel light condensed by the liquid crystal lens, the pixel size changes depending on the position from the emission side of the liquid crystal cell. For example, in the case of directly observing an image with a diffusion plate or the like on the exit side of the liquid crystal cell without using the projection optical system, an apparent pixel size changes if the position of the liquid crystal cell and the diffusion plate are shifted. In addition, even when the magnifying optical system is used, it is preferable that light emitted from the cell is parallel from the viewpoint of lens design. Therefore, in another configuration of the present invention, an optical element is provided such that light emitted from the liquid crystal cell is parallel to the optical axis of the projection optical system. When the characteristic of the liquid crystal lens array is a convex lens, this optical element is preferably a concave lens array that returns its optical path to parallel light. For example, as shown in FIG.
It is preferable to dispose it at a position shifted by a half pixel from the incident side pixel position.

By arranging the liquid crystal cell of FIG. 11 in the same manner as in FIG. 8, when the light emitted from the image display element 4 is linearly polarized in the horizontal direction in the drawing, the entire image display element 4 is moved in the horizontal direction in the drawing. Pixel shift can be performed. Therefore, a high-definition image display device having high resolution in the horizontal direction of the screen and high pixel position accuracy can be realized.

In FIGS. 4 and 9, only the electrodes of the upper substrate are formed in an array, but as shown in FIG. 13, the electrodes of both the upper and lower substrates are formed in an array, and a voltage is applied to the electrode at the position where the upper and lower electrodes overlap. This shows a structure in which the liquid crystal is vertically aligned by applying a voltage. In this case, when the operation of switching from the voltage On state to the Off state is performed in accordance with the subfield switching, the inversion speed (falling speed) of the liquid crystal tends to be lower than the rising speed. Can improve this. FIG. 19 shows n-1 of the electrode array.
The voltage application state is shown for the four lines from the nth to the (n + 2) th. Conventionally, the AC voltage application timings of the (n−1) th and (n + 1) th and the (n) th and (n + 2) th are equal to each other, so that a single power supply supplies voltages having the same phase. Therefore, for example, when the (n-1) th and (n + 1) th are generating AC voltages having the same phase, an equal electric field is applied from these electrodes to the liquid crystal molecules directly below the nth electrode array, and a horizontal electric field is generated. Did not.

On the other hand, in the present invention, these AC phases are set to 1
By inverting by 80 degrees, a horizontal alternating electric field having the same frequency is applied from these electrodes to the liquid crystal molecules immediately below the n-th electrode array. The state in which the AC voltage is applied to the nth and n + 2th, that is, the nth and n + 2
After the (n-1) th and (n + 1) th AC voltages are applied from the state where the liquid crystal at the bottom is oriented in the substrate vertical direction (see FIGS. 4 and 9), the liquid crystal molecules are oriented in the horizontal direction. The lateral electric field acts on the liquid crystal alignment, and a higher speed liquid crystal alignment can be achieved.

Even when a DC voltage is used instead of an AC voltage, the same effect can be obtained by reversing the polarity. When an auxiliary electrode is provided between these electrode arrays (see FIG. 14), a similar lateral electric field can be generated by appropriately setting the phase difference in accordance with the electrode interval.

When the two-frequency driving method is not used, an electric field is generated in an oblique direction with the liquid crystal layer interposed therebetween, and the electric field is inverted in accordance with the subfield switching to prevent the fall speed from decreasing. It is possible. In the optical path deflection driving means 7 in this case, an AC voltage whose phase is inverted by 180 degrees is applied to each of the shaded electrode arrays, and the unshaded electrode arrays are floating or It is preferable that the voltage is set to be equal to the voltage at the time of floating. By this setting, the strongest electric field is generated between the shaded electrode arrays sandwiching the liquid crystal, and along the direction connecting the electrode arrays corresponding to the positive or negative of the dielectric constant of the liquid crystal molecules, or with this. The liquid crystal molecules are aligned along the vertical direction. On the other hand, a large electric field is not generated between the electrodes opposed to the overlapping position with the electrodes interposed therebetween so as to cause a change in the alignment of the liquid crystal molecules, so that the liquid crystal molecules do not change the alignment. FIG. 20 shows a case where the liquid crystal molecules are initially formed in a state of being oriented vertically or horizontally to the substrate surface, but are oriented vertically.

In another case that is not based on the dual frequency driving method, the electrode array in the optical path deflecting means 6 is formed in the liquid crystal layer corresponding to the pixel pitch. The voltage application state to the electrode array is alternately switched and applied to the adjacent electrode arrays in synchronization with the subfield display timing in synchronization with the display driving means 5. As a result, a horizontal electric field is generated in the liquid crystal molecules, and the orientation is changed by the electric field near the electrode where the liquid crystal molecules are generating an alternating current, thereby changing the optical path (see FIG. 21). The alternating voltage is applied to the shaded electrode array and the shaded electrode array alternately in synchronization with the subfield.

In the above-described configuration, pixel multiplication in one direction can be performed using one liquid crystal cell. However, in order to perform higher-definition display, pixel multiplication must be performed in two directions in the vertical and horizontal directions. There is. Therefore, an optical path deflecting unit 6 as shown in FIG. 15 is used. The optical path deflecting means 6 includes a first optical path deflecting means 62 for shifting the optical path in a direction perpendicular to the drawing, a second optical path deflecting means 63 for shifting the light path in the vertical direction in the drawing, and a polarization plane rotating means 64 provided therebetween. Has become. The first optical path deflecting means 62 and the second optical path deflecting means 63 are the same as those described above, and their respective deflecting directions are determined by the image display element 4.
In two directions. Generally, since the directions of the pixel array are orthogonal, the direction of the electrode array and the direction of the alignment processing are set so that the operation directions of the first optical path deflecting means 62 and the second optical path deflecting means 63 are also orthogonal as shown in FIG. Is set. Here, in the liquid crystal cell as the optical path deflecting means 6 used in the present invention, since the direction of shifting the optical path and the direction of the linearly polarized light of light need to coincide, the polarization plane rotating means 64 is provided between the two liquid crystal cells. It is necessary to provide.

As the polarization plane rotating means 64, a TN liquid crystal cell, a ferroelectric liquid crystal cell, a half-wave plate, a Faraday rotator or the like can be used. In the case of a liquid crystal cell, since there is no need to perform switching by applying an electric field, no electrodes need be provided, but it is necessary to optimize the alignment treatment and the directionality of the substrate surface. When there is wavelength dependence such as a half-wave plate, the optical path may be separated for each color by a dichroic mirror or the like, and a half-wave plate for each color may be provided, and then combined again. By providing the optical path deflecting means (62, 63) in two directions and the polarization plane rotating means 64 between them, a high-definition image with an apparent number of pixels multiplied in two directions is displayed. Can be. By combining elements having a relatively simple electrode configuration, an optical path shift in two directions can be realized.

(Embodiment) Hereinafter, an image display apparatus according to a best mode for carrying out the present invention will be described.

Example 1 As Example 1 of the present invention, an image display device as shown in FIG. 1 was prepared. In this image display device, a 0.9-inch diagonal XGA (1
(024 × 768 dots) polysilicon TFT liquid crystal panel is used, the pixel pitch is about 18 μm both vertically and horizontally, and the pixel aperture ratio is about 50%. Further, a microlens array is provided on the light source 1 side of the image display element 4 to increase the light collection rate of the illumination light. In the first embodiment, RG is used as the light source 1.
A so-called field-sequential system is used in which color light is displayed by switching the color of light illuminating one liquid crystal panel at high speed using LED light sources of three colors B.
Generally, when the frame frequency of image display is 60 Hz, an image corresponding to each color is switched at 180 Hz in order to further divide one frame into three colors. By turning ON / OFF the LED light source of the corresponding color in accordance with the display timing of the image of each color on the liquid crystal panel, the observer can see the full color image. Since this method does not use a color filter and requires only one liquid crystal panel, it is advantageous for high definition of an image and miniaturization of an apparatus. In the first embodiment, the pixel shift method is combined with the field sequential method.

To perform double pixel multiplication in the horizontal direction of the image, the pixel position is shifted at 120 Hz, and the display time of the subfield image is within 8.3 milliseconds. This time includes a time (optical path switching time) Δt required for switching the optical path and a time during which the liquid crystal panel can be used for image display. The longer the time available for displaying images,
Since the LED emission time of the field sequential system can be extended, the emission luminance of the LED can be reduced, and the burden on the LED light source is reduced. Therefore, it is preferable that the optical path switching time Δt is as short as possible.

(Preparation of Liquid Crystal Microlens Array ) In order to prepare a liquid crystal microlens array, first, the IT
Glass substrate with O-deposited film (3 cm x 4 cm, thickness 0.
15 mm) are prepared, one glass substrate is left with ITO as it is, and the other substrate is
Etch the TO deposited film to a width of 10 μm and a pitch of 18
A μm ITO line was formed, and a comb-shaped electrode was formed so that the same voltage could be applied alternately to the ITO line. Then, a polyimide-based alignment material was spin-coated on the ITO side of the two glass substrates to form an approximately 0.1 μm alignment film, and a rubbing process was performed after annealing the glass substrates. At this time, the etched substrate is ITO
Rubbing was performed at right angles to the line. An empty cell was produced by sandwiching an 8 μm thick spacer between the two glass substrates so that the rubbing directions of the upper and lower substrates coincided with each other. A nematic liquid crystal having a positive dielectric anisotropy was injected into the cell under normal pressure to prepare a liquid crystal cell. Since the rubbing directions of the upper and lower substrates are the same, the liquid crystal molecules are all oriented in the same direction as shown in FIG. In order to confirm the operation of the liquid crystal cell, a light-shielding mask simulating a liquid crystal light valve with an opening width of 13 μm square and a vertical and horizontal pitch of 18 μm was attached to the incident side of the liquid crystal cell so as to be aligned with the electrode. When the collimated light was irradiated from above and observed from the emission side, the shape of the opening of the light shielding mask was observed as it was. When a voltage of about 3 V was applied to the alternate electrode lines as shown in FIG. 9, a lens effect appeared in the liquid crystal layer. When a diffuser having a thin diffusion layer is aligned with the exit side of the liquid crystal cell and the diffused light is observed at the exit surface, the aperture width is reduced to about 4 μm × 13 μm, and the aperture is arranged as shown by the solid line in the upper part of FIG. Was confirmed. Next, it was confirmed that when the electrode line to which the voltage was applied was switched, the position of the reduced optical path moved as shown by the broken line in the upper part of FIG.

This liquid crystal cell was placed immediately after the liquid crystal light valve (image display element 4), and the alignment between the pixel position and the electrode line was adjusted. Using a small white lamp as the light source 1, an observation experiment of black-and-white display using a transmission type liquid crystal light valve was performed. The liquid crystal light valve was driven by a subfield image signal of 120 Hz, and in synchronization with this, the waveform of the voltage applied to the electrode lines of the liquid crystal cell was switched. Table 1 shows the results. A rectangular wave having a frequency of 1 kHz is prepared by using the optical path deflection driving means 7 according to claim 1 and the voltage amplitude is changed between the subfield switching and the subfield display (see FIG. 17). (The average value of the liquid crystal rise time and the liquid crystal fall time) was improved, and the image quality was also improved.

[0055]

[Table 1]

In the first embodiment, since the shift direction of each pixel is not common as shown in FIG. 11, the subfield image is corrected and driven, and a diffusion plate having a thin diffusion layer on the exit side of the liquid crystal lens cell is used. In addition, when the diffused light on the emission surface was observed under magnification, a high-definition display image with twice the pixel density in the horizontal direction was obtained. However, there was a portion where the pixel size was uneven near the periphery of the image. This is presumably because the distance between the exit surface of the liquid crystal lens cell and the diffusion plate was not uniform, and the pixel size was changed due to light focusing on the optical path.

<Embodiment 2> In Embodiment 2 of the present invention, a liquid crystal lens cell is prepared in the same manner as in Embodiment 1, and a rectangular wave having a frequency of 1 kHz is prepared by using the optical path deflection driving means 7 according to Claim 3. did. The liquid crystal rising threshold voltage of the present liquid crystal lens cell is 0.3 V, and the liquid crystal falling threshold voltage is 2.3 V.
It was 8V. Table 2 shows the results. When the voltage is changed by applying an AC voltage having an amplitude V1 (V1 ≠ 0) equal to or smaller than the liquid crystal rising threshold voltage and applying an AC voltage having an amplitude V2 equal to or larger than the liquid crystal falling threshold voltage (see FIG. 18), the inversion speed is improved. Image quality has also been improved. However, when a voltage of 0.5 V was applied as V1, a decrease in contrast was observed. This is because the amplitude was equal to or higher than the rising threshold voltage of the liquid crystal, the orientation state of the liquid crystal molecules was not good, and the desired lens effect could not be obtained.

[0058]

[Table 2]

Third Embodiment In a third embodiment of the present invention, a liquid crystal lens cell is prepared in the same manner as in the first embodiment, and a rectangular wave having a frequency of 1 kHz and a voltage of 3 V is formed by using the optical path deflection driving means 7 according to the fourth embodiment. Was prepared. As a result, a voltage application state was obtained in which the AC phase was inverted by approximately 180 degrees corresponding to the pixel pitch of the electrode array (see FIG. 19 and Table 3). According to the third embodiment, by inverting the AC phase by approximately 180 degrees corresponding to the pixel pitch of the electrode array, the inversion speed is improved and the image quality is also improved.

[0060]

[Table 3]

<Embodiment 4> In Embodiment 4 of the present invention, a thin glass substrate (3 cm × 4 cm, thickness 0.15 mm) is used.
Etch the TO deposited film to a width of 10 μm and a pitch of 18
A μm ITO line was formed. Comb electrodes were formed so that the same voltage could be applied alternately to the ITO lines. A polyimide-based alignment material was spin-coated on the ITO side of the glass substrate to form an approximately 0.1 μm alignment film. After the annealing of the glass substrate, a rubbing treatment was performed in a direction perpendicular to the ITO line. Two glass substrates having this ITO line electrode are prepared, an 8 μm-thick spacer is provided around each of the glass substrates, and the two substrates are bonded together so that the ITO line positions of the upper and lower substrates coincide with each other to produce an empty cell. Was performed in the same manner as in Example 1 to produce a liquid crystal microlens array. With respect to the obtained cell, an AC voltage is generated between the electrode arrays that do not overlap with the liquid crystal layer interposed therebetween by using the optical path deflection driving means 7 according to claim 5 (FIG. 20). Reference) A rectangular wave having a frequency of 1 kHz and 3 V was applied. The electrode lines to which the AC voltage was applied were alternately switched in synchronization with the subfield switching timing, and the liquid crystal inversion time and the display image quality were evaluated. Example 4
, The liquid crystal inversion time was 1.6 μs, and it was confirmed that a faster response than before was possible, and the display image quality was also good.

(5) Example 5 In Example 5 of the present invention, the following liquid crystal microlens array was produced in place of the liquid crystal microlens array shown in Example 1. Thin glass substrate (3cm x 4cm, thickness of 0.
15 mm), a polyimide-based alignment material was spin-coated to form an approximately 0.1 μm alignment film, which was annealed and then rubbed. A Cr mask having an opening formed in the form of a stripe line with a width of 8 μm and a pitch of 18 μm is brought into close contact with the rubbed glass substrate in a direction perpendicular to the rubbing direction and the stripe line direction. 5 μm Al was formed on the substrate by vapor deposition to form an electrode. This Al line was a comb-shaped electrode so that the same voltage could be applied alternately. The other glass substrate facing this substrate was spin-coated with a polyimide-based alignment material to form an approximately 0.1 μm alignment film. After the annealing of the glass substrate, a rubbing treatment was performed in a direction perpendicular to the Al line. An empty cell was fabricated by sandwiching an 8 μm-thick spacer between the two glass substrates at the periphery. A nematic liquid crystal having a positive dielectric anisotropy was injected into the cell under normal pressure to prepare a liquid crystal cell. Since the rubbing directions of the upper and lower substrates are the same, the liquid crystal molecules are all oriented in the same direction in a direction perpendicular to the line electrodes. As shown in FIG. 21, when a voltage of about 3 V was alternately applied (every other electrode) to adjacent electrode arrays in synchronization with the subfield display timing, a lens effect appeared in the liquid crystal layer. When a diffusion plate having a thin diffusion layer is aligned with the exit side of the liquid crystal cell and the diffused light is observed on the exit surface, the opening width is about 4 μm × 13 μm.
It was confirmed that the array was reduced to m. next,
When the electrode line to which the voltage was applied was switched, it was confirmed that the position of the reduced optical path moved. Example 5
, The liquid crystal inversion time was 1.6 μs, and it was confirmed that a higher speed response was possible than before, and the display image quality was also good.

In each of the above embodiments, the image display element 4 is observed directly or through a magnifying lens system. However, the same effect can be obtained by observing the image display element 4 on a screen through a projection lens.

[0064]

As described above, according to the present invention,
By performing a predetermined optical path deflection for each subfield, in an image display device capable of displaying a high-resolution image using a low-resolution image display element, the switching speed of the optical path deflection is improved, and the image is distorted. And the light use efficiency of the illumination light can be improved.

Further, according to the first aspect of the present invention, a sub-field which applies a voltage enabling high-speed operation of the liquid crystal at the time of sub-field switching and maintains this liquid crystal distribution state at a timing approaching a predetermined liquid crystal distribution state. By switching to the voltage waveform at the time of display, disturbance of an image due to switching of subfields can be improved, and light use efficiency can be improved.

According to the second aspect of the present invention, high speed operation of the liquid crystal becomes possible by increasing the absolute value of the applied voltage at the time of subfield switching.

According to the third aspect of the present invention, when the optical path deflecting means made of a nematic liquid crystal is driven by the strength of an electric field of an AC voltage, conventionally, the rising threshold voltage of the liquid crystal is completely Off, that is, the voltage application is performed. Although it was set to a state in which no voltage is applied, compared to changing from a state in which no voltage is applied to a state in which a high voltage is applied, the liquid crystal inversion can be accelerated by setting the voltage in advance near the liquid crystal rising threshold voltage, High-speed operation can be performed for optical shift.

According to the fourth aspect of the present invention, the liquid crystal molecules are oriented from the normal direction of the substrate surface to the in-plane direction by utilizing the horizontal electric field from the adjacent electrode array to reduce the switching speed of the optical path deflection. Speed up.

According to the fifth aspect of the present invention, since only the liquid crystal molecules contributing to the optical path deflection are changed, the amount of change in the alignment of the liquid crystal molecules can be reduced, so that the switching speed of the optical path deflection can be increased. Can be

Further, according to the sixth aspect of the present invention, the pixel reduction can be performed favorably, the deterioration of the image quality can be reduced, and the high-speed switching can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an image display device according to the present invention.

FIG. 2 is a diagram for explaining that an apparent pixel multiplication effect can be obtained when an image display element is driven by an image signal of a subfield corresponding to a pixel shift position.

FIG. 3 is a schematic diagram showing the relationship between a conventional field, subfield, optical path deflecting means, and a light valve image signal.

FIG. 4 is a schematic diagram for explaining the operation of the liquid crystal optical path deflecting element of the present invention.

FIG. 5 is a diagram for explaining the relationship between the rate of change of the refractive index of linearly polarized light passing through the liquid crystal and the rise threshold voltage of the liquid crystal and the fall threshold voltage of the liquid crystal when a voltage is applied to the liquid crystal.

FIG. 6 is a diagram for explaining a change in a refractive index distribution in a liquid crystal cell of the liquid crystal optical path deflecting element of FIG.

FIG. 7 is a schematic diagram for explaining the operation of the image display element when light emitted from four pixels of the image display element (liquid crystal light valve) enters the liquid crystal cell from below in the figure.

FIG. 8 is a schematic view showing an arrangement of an optical path deflecting means of the present invention.

FIG. 9 is a schematic diagram for explaining the operation of the liquid crystal deflecting element having the pixel reduction function of the present invention.

FIG. 10 is a diagram for explaining a change in a refractive index distribution in a liquid crystal light deflecting element having a pixel reduction function.

FIG. 11 is an explanatory diagram for explaining a pixel reduction effect and a pixel shift effect by a liquid crystal lens.

FIG. 12 is an example in which a concave lens array is installed as an optical element that causes light emitted from a liquid crystal cell to be parallel to the optical axis of a projection optical system.

FIG. 13 is a diagram showing another configuration of the liquid crystal optical path deflecting element.

FIG. 14 is an example in which an auxiliary electrode is provided in an optical path deflecting unit.

FIG. 15 is a diagram illustrating another configuration of the image display device of the present invention that performs pixel multiplication in two directions vertically and horizontally.

FIG. 16 is a schematic diagram showing an arrangement of optical path deflecting means for two-way multiplication.

FIG. 17 is an example of driving waveforms that are different between the subfield switching and the subfield display of the first embodiment.

FIG. 18 is an example of driving waveforms that are different between subfield switching and subfield display according to the second embodiment.

FIG. 19 is an example of an optical path deflection drive signal for obtaining a voltage application state in which the AC phase is inverted by approximately 180 degrees corresponding to the pixel pitch of the electrode array in the third embodiment.

FIG. 20 is a diagram for explaining an effect when an electric field is generated in an oblique direction with a liquid crystal layer interposed therebetween in Example 4.

FIG. 21 is a diagram for explaining an effect when a voltage is applied to adjacent electrode arrays alternately in synchronization with a subfield display timing in the fifth embodiment.

FIG. 22 is a schematic explanatory diagram of a pixel shift function.

FIG. 23 is a schematic explanatory diagram of a pixel reduction function.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light source, 2 ... Light source drive means, 3 ... Illumination device, 31 ... Diffusion plate, 32 ... Condenser lens, 4 ... Image display element, 5
... display driving means, 6 ... optical path deflecting means, 62 ... first optical path deflecting means, 63 ... second optical path deflecting means, 64 ... polarization plane rotating means, 7 ... optical path deflecting driving means, 8 ... image display control circuit, 9
... projection lens, 10 ... screen.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/20 641 G09G 3/20 641E 5C058 660 660E 5C080 680 680 680 3/34 3/34 J 3/36 3 / 36 H04N 5/66 H04N 5/66 B 5/74 5/74 E (72) Inventor Ero Nimura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Yumi Matsuki Tokyo 1-3-6 Nakamagome, Ota-ku, Ricoh Co., Ltd. (72) Inventor Masanori Kobayashi 1-3-6, Nakamagome, Ota-ku, Tokyo In Ricoh Co., Ltd. (72) Inventor Yasuyuki Takiguchi Nakamagome, Ota-ku, Tokyo 1-3-6, Ricoh Co., Ltd. F term (reference) 2H088 EA33 EA37 EA45 GA02 HA06 MA03 MA10 MA13 2H089 HA33 QA05 QA11 QA12 TA03 TA04 TA07 2H093 N A07 NA21 NA34 NA36 NA43 NA80 NC42 NC90 ND52 ND54 NE04 NE07 NF04 2K002 AA07 AB06 BA06 DA14 EA14 EA30 GA07 HA02 5C006 AA01 AA14 AA22 AC28 AF44 AF47 BB16 BB29 EA01 EC11 EC13 FA11 FA21 5C058 BA25 EA02 EA02 DD08 JJ04 JJ05 JJ06

Claims (6)

[Claims] An image display device in which a plurality of pixels capable of controlling light in accordance with image information are two-dimensionally arranged, a light source and a lighting device for illuminating the image display device, and an image pattern displayed on the image display device An optical device for observing an image, a display driving unit for forming an image field by a plurality of sub-fields divided in time, and an optical path deflecting unit for deflecting an optical path of light emitted from each pixel. An image display device for displaying an image pattern in a state where a display position is shifted in accordance with a deflection state of an optical path for each field so as to increase an apparent number of pixels of an image display element and display the image pattern. The deflecting means comprises two transparent substrates, an electrode array formed on at least one of the substrates corresponding to the pixel pitch, and the refractive index distribution can be controlled by applying a voltage between these two substrates. Liquid crystal layer, and an optical path deflecting drive unit configured to change and set a voltage application state to the electrode array to a different waveform between subfield switching and subfield display in synchronization with the display driving unit. An image display device comprising: 2. The image display device according to claim 1, wherein said optical path deflection driving means sets an absolute value of an applied voltage at a time of subfield switching to be larger than an absolute value of a voltage at the time of subfield display. An image display device characterized by the above-mentioned. 3. An image display element in which a plurality of pixels capable of controlling light in accordance with image information are two-dimensionally arranged, a light source and a lighting device for illuminating the image display element, and an image pattern displayed on the image display element. An optical device for observing an image, a display driving unit that forms an image field by a plurality of subfields divided in time, and an optical path deflecting unit that deflects an optical path of light emitted from each pixel. An image display device which displays an image pattern in a state where a display position is shifted according to a deflection state of an optical path for each field to increase an apparent number of pixels of an image display element and display the image pattern. The deflecting means comprises two transparent substrates, an electrode array formed on at least one of the substrates corresponding to the pixel pitch, and the refractive index distribution can be controlled by applying a voltage between these two substrates. Liquid crystal layer, and optical path deflection driving means for alternately switching and applying the voltage to the electrode arrays in synchronization with the subfield display timing to the electrode arrays adjacent to each other in synchronization with the display driving means. The image display device, wherein the optical path deflection driving means has an alternating voltage whose amplitude (non-zero) is equal to or lower than a liquid crystal rising threshold voltage on the low voltage side of the switching voltage. 4. An image display device in which a plurality of pixels capable of controlling light in accordance with image information are two-dimensionally arranged, a light source and a lighting device for illuminating the image display device, and an image pattern displayed on the image display device An optical device for observing an image, a display driving unit for forming an image field by a plurality of sub-fields divided in time, and an optical path deflecting unit for deflecting an optical path of light emitted from each pixel. An image display device which displays an image pattern in a state where a display position is shifted according to a deflection state of an optical path for each field to increase an apparent number of pixels of an image display element and display the image pattern. The deflecting means comprises two transparent substrates, an electrode array formed on at least one of the substrates corresponding to the pixel pitch, and the refractive index distribution can be controlled by applying a voltage between these two substrates. And a light path deflection driving means for alternately switching and applying a voltage to the electrode arrays adjacent to each other in synchronization with the subfield display timing in synchronization with the display driving means. An image display device, wherein the optical path deflection driving means forms a voltage application state in which the AC phase is inverted by approximately 180 degrees corresponding to the pixel pitch of the electrode array. 5. The image display device according to claim 1, wherein the optical path deflecting unit forms the electrode array on both substrates at a position substantially overlapping with a pixel pitch. The voltage application state of the optical path deflection driving means is:
An image display device, wherein an AC voltage is generated between the electrode arrays that do not overlap with the liquid crystal layer interposed therebetween. 6. The image display apparatus according to claim 1, wherein said optical path deflecting means forms said electrode array in said liquid crystal layer corresponding to a pixel pitch, and said optical path deflecting drive is performed. An image display device wherein voltage application states of the means are alternately switched and applied to electrode arrays adjacent to each other in synchronization with a subfield display timing.