JP2002357809A - Picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection type picture display device realizing a bright, high definition and uniform display and further suited for miniaturization and cost reduction. SOLUTION: A picture shifting element is provided with at least one liquid crystal element 10 switching a polarized state of light to another state responding to voltage application, at least one birefringent element 11 making an optical axis position shift corresponding to the polarized state of the light and a voltage applying part to selectively supply voltages of a plurality of levels to the liquid crystal element 10. Each of the voltages of a plurality of the levels has a value other than zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image shift element suitably used for a head-mounted display (hereinafter referred to as "HMD"), a projection type image display device (projector), and the like, and the image shift element. And an image display device having the same.

[0002]

2. Description of the Related Art A liquid crystal display device has a pair of substrates and a liquid crystal layer sandwiched between these substrates. The substrate has a plurality of pixel electrodes regularly arranged in rows and columns (matrix), and a driving voltage corresponding to an image signal is applied to each of the pixel electrodes. The application of this voltage changes the optical characteristics (light transmittance and reflectance) of the liquid crystal layer for each pixel, so that images and characters can be displayed.

[0003] There are a "simple matrix system" and an "active matrix system" for applying an independent drive voltage to each pixel electrode on the substrate.

In the case of the active matrix system, switching elements corresponding to each pixel electrode are arranged on a substrate. A substrate on which such switching elements are arranged is called an active matrix substrate. A switching element on the active matrix substrate functions to switch between an electrically conductive state and a non-conductive state between a corresponding pixel electrode and a signal wiring. Such switching elements include a metal-insulator-metal (MIM) element and a thin film transistor (TF).
T) and the like are preferably used.

When the switching element is in a non-conductive state,
It is required to exhibit as high an electrical resistance as possible. However, when strong light enters the non-conducting switching element, the electrical resistance of the switching element decreases,
Since a leak current is generated, there is a problem that charges stored in the pixel electrodes are discharged. In addition, an appropriate level of drive voltage is not applied to the pixel electrode, so that the original display operation is not performed. Even in a black state, light leaks and the contrast ratio is reduced.

When the liquid crystal display element is of a transmission type, a light shielding layer called a black matrix is provided on an active matrix substrate or on a counter substrate facing the active matrix substrate with a liquid crystal layer interposed therebetween in order to solve the above problem. Be placed. The presence of the black matrix reduces the area ratio (opening ratio) of the pixel opening. In order to achieve high definition by reducing the occupation area of the black matrix, it is necessary to make the switching elements and wiring finer. However, if the switching elements and wiring are made finer, the driving force decreases and the wiring resistance increases. Will be. Also, it is difficult to miniaturize the switching elements and wirings due to restrictions on manufacturing technology.

A technique for optically moving a display image by about a pixel pitch for the purpose of achieving higher definition using a non-display area on a black matrix is disclosed in US Pat.
091. According to this technique, an image corresponding to the moved pixel position is displayed in synchronization with the movement of the pixel. As a result, the apparent number of pixels increases, so that the same display as that using a high-definition display panel can be performed even when a display element with a low resolution is used.

US Pat. No. 6,061,103 discloses red,
A method is disclosed in which pixels of green and blue (hereinafter, referred to as “RGB”) are optically sequentially shifted by a shift element, and the shifted pixels are displayed in a superimposed manner. In this method, RGB pixels are displayed in a time-division manner in a region corresponding to one pixel. As a result, the apparent resolution can be tripled without reducing the pixel pitch on the display panel.

US Pat. No. 6,061,103 discloses an image shift element combining a liquid crystal element and a birefringent element as means for optically shifting an image. The birefringent element is formed of a material whose light refraction direction changes depending on the polarization direction of incident light. If the polarization direction of the light incident on the birefringent element is changed by the liquid crystal element, the optical axis of the light emitted from the birefringent element can be shifted.

FIG. 1 shows a known image shift element. This image shift element includes a liquid crystal element 10 and a birefringent element 11 arranged in series along the propagation direction of light rays. The liquid crystal element 10 switches between a state in which an incident electric field vector vibration plane of linearly polarized light (hereinafter, referred to as a “polarization plane”) is rotated by 90 ° and a state in which the plane is transmitted without being rotated. The birefringent element 11
The light beam can be shifted according to the direction of the plane of polarization of the linearly polarized light that enters.

In the example shown in FIG.
The electric field vector direction (polarization direction) of the light incident on is perpendicular to the paper surface. Since the liquid crystal element 10 uses a TN mode liquid crystal (TN liquid crystal), when no voltage is applied to the liquid crystal element 10 (OFF state), the plane of polarization of the incident light is rotated by 90 °, and When a voltage higher than the level is applied (ON state), the polarization plane of the incident light is emitted while being perpendicular to the paper surface. The birefringent element 11 transmits the light whose polarization plane is perpendicular to the paper surface as it is, but shifts the light parallel to the paper surface.

[0012]

However, the above-mentioned image shift element has the following problems.

The liquid crystal element in the image shift element as shown in FIG. 1 emits a first linearly polarized light according to the magnitude of the applied voltage, and a second state having a polarization plane perpendicular to the first linearly polarized light. It is required to switch appropriately and promptly to a state of emitting linearly polarized light. In the case of a liquid crystal element using a TN liquid crystal, when no voltage is applied to the TN liquid crystal, the linearly polarized light incident on the liquid crystal element is emitted as a linearly polarized light having a plane of polarization rotated by 90 °, but the light is always perfect. It cannot be linearly polarized light but becomes elliptically polarized light due to residual optical rotation dispersion. When the analyzer is arranged on the emission side of the liquid crystal element so as to block the linearly polarized light and the "voltage transmittance characteristic" of the combination of the liquid crystal element and the analyzer is measured, a curve shown in FIG. 2 is obtained. Originally, if the voltage applied to the liquid crystal is zero, the light emitted from the liquid crystal element should be linearly polarized light, which is almost 100% cut off by the analyzer. However, the component transmitted through the analyzer due to the residual optical rotation dispersion described above. Will exist. The value α in the graph of FIG. 2 indicates the presence of a polarization component that passes through the analyzer.

As shown in FIG.
If the switching between the states in which the polarization direction of the linearly polarized light is accurately rotated by 90 ° can be performed by turning OFF, the optical axis of the light emitted from the birefringent element 11 moves to the position A in FIG. But,
When the linearly polarized light is broken by the residual optical rotation dispersion and the elliptically polarized light is incident on the birefringent element, a part of the light emitted from the birefringent element 11 is not shifted to the position A but moves to the position B. . Therefore, the same image is displayed twice at both the position A and the position B, and the resolution is reduced.

The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide an image shift element capable of suppressing an inappropriate shift of an image due to residual optical rotation dispersion of a liquid crystal element, Another object of the present invention is to provide an image display device using the image shift element.

[0016]

An image shift element according to the present invention comprises at least one liquid crystal element capable of switching the polarization state of light in response to application of a voltage, and an optical axis position according to the polarization state of light. At least one birefringent element that can be shifted; and a voltage application unit that selectively supplies a plurality of levels of voltages to the liquid crystal element, wherein each of the plurality of levels has a non-zero value. are doing.

In a preferred embodiment, the liquid crystal element emits a first polarized light when a first voltage included in the plurality of levels of voltage is applied, and outputs a second polarized light included in the plurality of levels of voltage. Is applied, the plane of polarization is substantially 90 ° rotated with respect to the first polarized light.
Out of the polarized light.

In a preferred embodiment, the liquid crystal element has a liquid crystal layer sandwiched between a first surface and a second surface, and the liquid crystal layer is applied with the first voltage. When the second voltage is applied, the first state in which the plane of polarization of the linearly polarized light incident from the first surface is rotated by about 90 ° with respect to the optical axis and emitted is adopted. A second light beam that is emitted without substantially rotating the plane of polarization of linearly polarized light
Take the state of.

In a preferred embodiment, when the first voltage is applied, the liquid crystal layer has a polarization state in which an electric field vector oscillates in a direction parallel to a plane of polarization of linearly polarized light incident from the first plane. It is designed to minimize the proportion of the component in the emitted light.

In one preferred embodiment, the first
Is smaller than the absolute value of the second voltage.

In one preferred embodiment, the first
Is the smallest of the absolute values of the voltages of the plurality of levels.

In one preferred embodiment, the first
Has an offset value controlled according to the temperature of the liquid crystal element.

In one preferred embodiment, an offset value of the first voltage is adjusted according to a temperature of the liquid crystal element, thereby increasing a ratio of a linearly polarized light component included in the first polarized light. Means are further provided.

The image shift element according to the present invention has at least one liquid crystal element that can switch the polarization state of light in response to voltage application, and at least can shift the optical axis position according to the polarization state of light. A single birefringent element, and a voltage application unit for selectively supplying a plurality of levels of voltages to the liquid crystal element, wherein at least the absolute value of the plurality of levels of the voltage has a minimum level. It has a value that changes according to the temperature of the element.

In a preferred embodiment, a voltage adjusting means for adjusting a value of the voltage according to a temperature of the liquid crystal element to increase a ratio of a linearly polarized light component included in polarized light emitted from the liquid crystal element is further provided. Have.

In one preferred embodiment, the first
Has an offset value set based on the voltage transmittance characteristic of visible light transmitted through the liquid crystal element.

In a preferred embodiment, the offset value is set based on a voltage transmittance characteristic of green light transmitted through the liquid crystal element.

In a preferred embodiment, the number of the liquid crystal element and the number of the birefringent elements are both plural, and the optical axis position is shifted so as to move at three or more different positions.

An image display device according to the present invention is an image display device comprising: an image display unit for displaying an image; and the image shift element according to claim 1. By using the light, the light emitted from the image display unit is shifted while being synchronized with the display of the image display unit.

In a preferred embodiment, light emitted from the image display section and incident on the image shift element is linearly polarized light.

In one preferred embodiment, the number of the liquid crystal element and the number of the birefringent elements included in the image shift element are both plural, and the image moves at three or more different positions in a certain plane. To be shifted.

In a preferred embodiment, pixels constituting the image are observed in a superimposed manner due to the shift of the image.

An image display device according to the present invention comprises: a light source; an image display panel having a plurality of pixel regions each of which can modulate light; and a light source for converting the light from the light source into a plurality of pixels according to a wavelength range. A projection-type image display device, comprising: a light control unit that focuses light on a corresponding pixel region of a region; and an optical system that forms an image on a projection target surface by light modulated by the image display panel. A circuit for generating data of a plurality of sub-frame images from the data of each frame image constituting the image, displaying the plurality of sub-frame images in a time-division manner by the image display panel, and displaying the image by the image display panel. Any one of the image shift elements described above, which shifts a selected sub-frame image among the plurality of sub-frame images on the plane to be projected. Wherein a light belonging to different wavelength ranges that have been modulated in different pixel regions of the panel sequentially illuminating the same area on the projection surface.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image display device according to the present invention will be described below with reference to the drawings.

Embodiment 1 First, reference is made to FIG. FIG. 3 is a schematic diagram of the image display device of the present invention.

The illustrated image display apparatus of the present embodiment includes a backlight 1, a liquid crystal display element 2, an image shift element 3, and an observation optical system 4. Backlight 1
Is a light source for illuminating the transmissive liquid crystal display device 2. The liquid crystal display element 2 can receive a drive signal and a video signal from the drive circuit 5 and display an image having contents corresponding to the video signal. The observation optical system 4 is an optical system for optically enlarging an image displayed on the liquid crystal display element 2.
An observer can observe an image displayed on the liquid crystal display device 2 via the image shift element 3 and the observation optical system 4.

In the present embodiment, a transmissive liquid crystal display element requiring a backlight is used. However, as long as it can display an image, not only a reflective liquid crystal display element but also an organic EL element can be used.
A self-luminous display element such as an L element or a plasma display panel (PDP) can also be used.

The operation of the image shift element 3 is controlled by a drive circuit 6 for the image shift element. This drive circuit 6
Supplies a drive signal synchronized with the image display of the liquid crystal display element 2 to the image shift element 3. The drive circuit 6 has a voltage application unit for applying a plurality of levels of voltages to the liquid crystal element included in the image shift element 3.

Of the above constituent elements, the backlight 1, the liquid crystal display element 2, the observation optical system 4, and the drive circuit 5 have the same configuration as the elements and circuits used in the conventional image display device. The feature of the display device according to the present embodiment lies in the configuration and operation of the image shift element 3. Less than,
Referring to FIGS. 4A to 4D, the image shift element 3
Will be described in detail.

The illustrated image shift element 3 is manufactured using two liquid crystal elements 7 and three birefringent elements 8. Each of the two liquid crystal elements 7 includes a liquid crystal layer and a pair of transparent electrodes sandwiching a light incident surface and a light exit surface of the liquid crystal layer. Each liquid crystal element 7 in the present embodiment is:
Switching between a state in which the polarization plane of the incident light is rotated by about 90 ° (first state) and a state in which the polarization plane of the incident light is emitted as it is without substantially rotating (second state); Either state can be selectively taken according to the magnitude of the applied voltage. The liquid crystal element 7 in the present embodiment is manufactured using, for example, a TN liquid crystal. The type of liquid crystal that can be used for the liquid crystal element 7 is not limited to the TN liquid crystal, and may be any type of liquid crystal that can control the polarization direction. For example, a ferroelectric liquid crystal, a vertical alignment mode liquid crystal, an OCB mode liquid crystal, or the like can be used.

The birefringent element 8 is made of a uniaxial crystal material (for example, quartz). The material used for the birefringent element 8 is not limited to quartz, but may be any material as long as it is a uniaxial crystal. For example, lithium niobate, calcite, mica, rutile (TiO ₂ ), chile saltpeter (NaNO ₃ )
Such a material can be used. However, when it is necessary to reduce the total weight of the display device as in the case of the HMD,
It is preferable to use lithium niobate or rutile having a relatively large refractive index anisotropy (△ n). If the material has a large Δn, the thickness of the birefringent element 8 required to obtain a required image shift amount can be reduced, and thus it is suitable for miniaturization and weight reduction.

As described above, by adjusting the voltage applied to the liquid crystal element 7, the polarization direction of the linearly polarized light emitted from the liquid crystal display element 2 can be rotated by 90 °. The birefringent element 8 has an optical axis inclined from the light incident surface of the birefringent element 8. The birefringent element 8 can separate an incident light into an ordinary light and an extraordinary light in a plane including a traveling direction and an optical axis of the incident light (hereinafter, referred to as a “principal section”). Therefore, if the polarization direction of the light incident on the birefringent element is perpendicular to the “principal section”, the incident light becomes ordinary light for the birefringent element 8 and propagates straight through the principal section. On the other hand, if the polarization direction of the light incident on the birefringent element 8 is parallel to the main section, the incident light becomes extraordinary light for the birefringent element 8 and is refracted in the main section.

As described above, by changing the voltage level applied to the liquid crystal element 7 to switch the polarization direction of the incident light in a direction perpendicular or horizontal to the main section of the birefringent element 8, the birefringent element 8 can shift the incident light beam. As a result, the image displayed on the display element 2 can be shifted in a direction perpendicular to the incident optical axis.

In FIG. 4A, the light is guided to the position A on the virtual plane by turning off both the two liquid crystal elements 7. In FIG. 4B, by setting the two liquid crystal elements 7 to the “ON” state and the “ON” state, light rays are guided to the position B on the virtual plane. In FIG. 4C, the two liquid crystal elements 7 are turned on and off, respectively, to guide light to a position C on the virtual plane. FIG.
In (d), the two liquid crystal elements 7 are both set to “OFF”.
By setting the state, the light ray is guided to the position D on the virtual plane.

As described above, by controlling the voltage applied to the two liquid crystal elements 7, the image on the display
→ B → C → D → A →... Such an image shift is executed in synchronization with the timing of switching the image displayed on the display element 2.

FIG. 5A shows a pixel arrangement when the shift operation by the image shift element is not performed.
(B) shows a pixel array when a shift operation is performed by the image shift element. It can be seen that the number of pixels of the liquid crystal display element 2 is effectively quadrupled by using the image shift element.

In this specification, when a voltage for controlling the polarization plane is applied to the liquid crystal element 7 and the polarization plane of the light emitted from the liquid crystal element 7 rotates about 90 ° as compared with the case where no voltage is applied, It is referred to as "the liquid crystal element is in the ON state". Then, a voltage sufficiently smaller than the magnitude (absolute value) of the voltage required to turn the liquid crystal element into the “ON state” is applied to the liquid crystal of the liquid crystal element 7, and as a result, the liquid crystal element
When the liquid crystal element 7 emits light having a polarization plane substantially orthogonal to the polarization plane of the emitted light obtained in the “N state”, the liquid crystal element is in an “OFF state”.

Conventionally, in order to turn off the liquid crystal element, the magnitude of the voltage applied to the liquid crystal layer of the liquid crystal element has been reduced to zero. On the other hand, the present invention is characterized in that when the liquid crystal element 7 in the image shift element is turned off, a voltage (offset voltage) having a non-zero value (for example, 2.5 volts) is applied. Have.

As described above, in the present embodiment, the magnitude of the voltage applied to each of the liquid crystal elements 7 in the image shift element is switched between a relatively high level and a relatively low level. , One pixel is sequentially shifted to four different positions of A → B → C → D on a certain virtual plane. Since the applied voltage for rotating the polarization plane of the incident light by 90 ° is optimized based on the voltage transmittance characteristics of the liquid crystal layer, it is possible to solve the problem caused by the residual optical rotation dispersion of the TN liquid crystal. it can. Hereinafter, optimization of the voltage applied to the liquid crystal will be described.

Like the liquid crystal element used in the conventional image shift element, the liquid crystal element 7 used in the present embodiment also has a voltage transmittance characteristic as shown in FIG. 2 for light of 550 nm (green light). Is shown. For this reason, when the magnitude of the applied voltage is set to zero, light whose polarization direction differs from the originally required linearly polarized light by 90 ° by the value α in FIG. 2 is incident on the birefringent element. At this time, for example, all the two liquid crystal elements are O
In the FF state (FIG. 4A), the pixels of the display element 2 appear not only at the position A but also at the position B, and the resolution is significantly reduced.

However, in this embodiment, the offset voltage E of 2-3 volts is applied to the liquid crystal element 7 even in the OFF state.
, The light of the component corresponding to the value α is reduced. As a result, the image of the pixel appearing at the position B can be almost eliminated, and a decrease in resolution can be prevented.

In this embodiment, the display pixels are sequentially shifted to four positions. However, the shift direction and the number of shift positions of the image shift element according to the present invention are not limited to these. Further, the display device of the present embodiment can be suitably used as an HMD, but the present invention is not limited to this. The present invention can also be applied to a projection type image display device. In this case, a directional illumination light source may be used instead of the backlight 1 that emits diffused light, and a projection lens may be used instead of the observation optical system.

After shipment from the factory, a function of adjusting the magnitude of the offset voltage may be given to the voltage applying unit.

(Embodiment 2) Next, another embodiment of the image display apparatus according to the present embodiment will be described with reference to FIG.

In the image display device according to the present embodiment, the light (light including at least RGB components) emitted from the light source 501 is reflected by the parabolic mirror 502 to be substantially parallel light, and then the fly-eye lens 503 Incident. The fly-eye lens 503 is used to uniformly illuminate the liquid crystal panel 504. On the exit side of the fly-eye lens 503,
An aperture 505 for controlling the parallelism of the illumination light incident on the liquid crystal panel 504 is provided. Aperture 5
05 has a rectangular opening, the shape of which is designed according to the pixel shape. After passing through the aperture 505, the light passes through the lens 506, and is separated into RGB light by dichroic mirrors 507R, 507G, and 507B. The liquid crystal panel 504 is irradiated with light that has been made substantially parallel by the lenses 506 and 508, and each of the RGB lights separated by the dichroic mirror enters the liquid crystal panel 504 at a different angle. In addition,
In this embodiment, a 0.9-inch panel (768 × 1024 dots) is used as the liquid crystal panel 504.

FIG. 7 is a cross-sectional view showing how RGB light enters the liquid crystal panel 508. As shown in FIG. 7, on the light incident side of the liquid crystal panel 504, three pixels (R
Pixel, G pixel, and B pixel), an array of microlenses 509 is arranged at one ratio. Each microlens 509 has a different angle of RGB
Light is incident on a corresponding pixel. Since each pixel is driven independently, the RGB light is independently modulated.

Referring again to FIG. LCD panel 504
The light modulated by transmission passes through the image shift element 510 and enters the projection lens 511. The light passing through the projection lens 511 forms an image on a screen.
The screen image is periodically shifted by the image shift element.

Next, the image shift element 510 of this embodiment will be described in detail with reference to FIG. As shown in FIG. 8, the image shift element 510 has a configuration in which two liquid crystal elements 10 and two birefringent elements 11 are alternately arranged in series, and has a plane intersecting the optical axis (“ The image can be shifted to three different positions (A, B, C) within the "main section"). What is the combination of the liquid crystal element 10 and the birefringent element 11 respectively? It has a configuration similar to the configuration shown in FIG.

FIG. 9 shows the image shift element 510 shown in FIG.
2 schematically shows how the sub-frame image shifted up and down moves up and down. By the function of the image shift element 510, the sub-frame image forming the image is sequentially shifted in the vertical direction (or the horizontal direction) by one pixel pitch, and as a result, the band of light illuminating the same pixel area on the screen is, for example, B → G → R → B → G → R... By adopting such a configuration, it is possible to achieve a resolution equivalent to that of a three-panel projection image display apparatus using three liquid crystal display panels, even if it is a single-panel type.

The liquid crystal element constituting the image shift element 510 is formed using a TN liquid crystal having the same characteristics as those of the display device according to the first embodiment. Also in the present embodiment, an offset voltage is applied to the liquid crystal element. In the present embodiment, the offset voltage is adjusted according to the temperature of the liquid crystal element. In the case of a projection display device, since high-intensity light from a high-output lamp is incident on the liquid crystal element, the temperature of the liquid crystal element tends to increase, for example, to 60 ° C. or higher. Since the voltage transmittance characteristic of the liquid crystal changes depending on the temperature, it is preferable that the magnitude of the offset voltage is also adjusted according to the temperature of the liquid crystal element. The liquid crystal element in the image shift element used in the present embodiment has a temperature characteristic as shown in FIG. For this reason, in the present embodiment, the temperature of the liquid crystal element 10 is detected by a temperature sensor or the like. When the temperature of the liquid crystal element 10 changes from 25 ° C. → 40 ° C. → 60 ° C., the magnitude of the offset voltage is set to E according to the detected temperature.
→ F → G is automatically changed (see FIG. 10). As a result, it is possible to eliminate the adverse effect due to the temperature dependence of the liquid crystal and achieve high resolution in a wide temperature range. Specifically, a temperature compensation circuit (not shown) is provided, and the output of the temperature sensor is always or periodically provided to the temperature compensation circuit. The temperature compensation circuit sends a control signal to the drive circuit for the image shift element based on the output of the temperature sensor and based on a previously stored calculation formula or table. The drive circuit for the image shift element adjusts the value of the offset voltage applied to the liquid crystal element based on the control signal. Since the value of the offset voltage changes according to the temperature of the liquid crystal element, it may have a magnitude of zero under certain conditions. The applied voltage in this case is also referred to as “offset voltage” in this specification.

The image display device of the present embodiment is a projection display device for projecting a display image on a screen.
By using an observation optical system, it is also possible to apply to an HMD.

In any of the above embodiments, the offset voltage is set so that the value α for the G light (green light) is minimized. However, the voltage transmittance characteristic of liquid crystal is
It depends on the wavelength range of the incident light. FIG. 11 shows the wavelength dependence of the voltage transmittance characteristic obtained in the same manner as the graph of FIG. As can be seen from FIG. 11, the magnitude of the voltage for minimizing the value α differs depending on the wavelength range.

The reason why the offset voltage is determined so that the value α for the G light becomes minimum in the above embodiment is as follows.
This is because human visual sensitivity is highest for G light. For this reason, it is usually preferable to set the offset voltage based on the voltage transmittance characteristic of the G light. But,
The offset voltage may be set so that the value α for the R light (red light) or the B light (blue light) is minimized, or the offset voltage is set so that the difference in the value α between RGB is minimized. May be set.

In this embodiment, a Philips UHP lamp having an output of 120 W and an arc length of 1.4 mm is used as the light source 501. Other light sources include a halogen lamp, a xenon lamp, and a metal halide lamp. Etc. can be used.

[0065]

According to the image shift element of the present invention,
Inappropriate shift of an image due to residual optical rotation dispersion of a liquid crystal element can be suppressed. By using such an image shift element, an image display device that displays a high-resolution image is provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of an image shift element in which a liquid crystal element and a birefringent element are combined.

FIG. 2 is a graph showing a liquid crystal applied voltage-transmittance characteristic in a case where a pair of polarizing plates are arranged in parallel Nicols and a liquid crystal element is arranged between the polarizing plates.

FIG. 3 is a diagram showing a first embodiment of the image display device according to the present invention.

FIG. 4 is a diagram illustrating an operation of the image shift element used in the first embodiment.

5A and 5B are diagrams showing an increase in resolution of an image by the image shift element in FIG. 4, wherein FIG. 5A shows an image when the image shift element is not operating, and FIG. FIG.

FIG. 6 is a diagram showing a second embodiment of the image display device according to the present invention.

FIG. 7 is a sectional view showing a liquid crystal display panel used in a second embodiment.

FIG. 8 is a cross-sectional view illustrating an image shift element used in the second embodiment.

FIG. 9 is a diagram schematically showing a shift of an image.

FIG. 10 is a graph showing that the voltage transmittance characteristics of FIG. 2 change depending on the liquid crystal temperature.

FIG. 11 is a graph showing that the voltage transmittance characteristics of FIG. 2 change depending on the wavelength of light.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 backlight 2 liquid crystal display panel 3 image shift element 4 observation optical system 5 liquid crystal element panel drive circuit 6 image shift element drive circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 9/30 H04N 9/30 (72) Inventor Takeshi Shibatani 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka 2H088 EA10 EA12 EA18 EA37 EA47 HA08 HA13 HA14 HA24 HA28 JA05 MA03 2H093 NC01 NC14 NC63 ND42 ND54 NE06 NF05 NG02 2H099 AA11 BA09 CA00 CA05 5C058 AA08 AB03 BA01 BA35 DA07 DA05 DB03 DB13 DB15 HC16 JA20

Claims (18)

[Claims] At least one liquid crystal element capable of switching a polarization state of light in response to voltage application, and at least one birefringent element capable of shifting an optical axis position according to a polarization state of light. An image shift element, comprising: a voltage applying unit that selectively supplies a plurality of levels of voltages to the liquid crystal element, wherein each of the plurality of levels has a non-zero value. 2. The liquid crystal element emits a first polarized light when a first voltage included in the plurality of levels of voltage is applied, and applies a second voltage included in the plurality of levels of voltage. The image shift element according to claim 1, wherein, when the light is emitted, a second polarized light having a plane of polarization substantially rotated by 90 ° with respect to the first polarized light is emitted. 3. The liquid crystal element has a liquid crystal layer sandwiched between a first surface and a second surface, wherein the liquid crystal layer has a structure that, when the first voltage is applied, In the first state, the plane of polarization of the linearly polarized light incident from the first surface is rotated by about 90 ° with respect to the optical axis and emitted, and when the second voltage is applied, the polarization of the linearly polarized light is changed. The image shift element according to claim 2, wherein the image shift element is in a second state of emitting light without substantially rotating the surface. 4. The emitted light of a polarization component in which an electric field vector oscillates in a direction parallel to a plane of polarization of linearly polarized light incident from the first plane when the first voltage is applied to the liquid crystal layer. 4. The image shift element according to claim 3, wherein the image shift element is designed to minimize the ratio in the above. 5. The image shift element according to claim 2, wherein an absolute value of said first voltage is smaller than an absolute value of said second voltage. 6. The image shift element according to claim 5, wherein the absolute value of the first voltage is the smallest among the absolute values of the voltages of the plurality of levels. 7. The image shift element according to claim 2, wherein the first voltage has an offset value controlled according to a temperature of the liquid crystal element. 8. An offset value of the first voltage is adjusted according to a temperature of the liquid crystal element, thereby adjusting the first voltage.
The image shift element according to claim 7, further comprising a voltage adjusting means for increasing a ratio of a linearly polarized light component included in the polarized light. 9. At least one liquid crystal element capable of switching a polarization state of light in response to voltage application, and at least one birefringent element capable of shifting an optical axis position according to a polarization state of light. A voltage application unit for selectively supplying a plurality of levels of voltages to the liquid crystal element, wherein at least the absolute value of the plurality of levels of the voltage has a minimum level according to the temperature of the liquid crystal element Image shift element having a value that varies with time. 10. A voltage adjusting means for adjusting a value of the voltage according to a temperature of the liquid crystal element to increase a ratio of a linearly polarized light component included in polarized light emitted from the liquid crystal element. 10. The image shift element according to 9. 11. The liquid crystal device according to claim 2, wherein the first voltage has an offset value set based on a voltage transmittance characteristic of visible light transmitted through the liquid crystal element. Image shift element. 12. The image shift element according to claim 11, wherein the offset value is set based on a voltage transmittance characteristic of green light transmitted through the liquid crystal element. 13. The liquid crystal device and the birefringent device each having a plurality of numbers, and the optical axis position is shifted so as to move at three or more different positions. An image shift element according to any one of the above. 14. An image display device comprising: an image display unit for displaying an image; and the image shift element according to claim 1, wherein the image shift element includes: An image display device that shifts light emitted from an image display unit while synchronizing the display with the image display unit. 15. The image display device according to claim 14, wherein light emitted from the image display unit and incident on the image shift element is linearly polarized light. 16. The image shift element includes a plurality of liquid crystal elements and a plurality of birefringent elements, each of which includes a plurality of liquid crystal elements and a plurality of birefringent elements, wherein the image is shifted so as to move at three or more different positions within a certain plane. Claim 14 or 1
6. The image display device according to 5. 17. The image forming apparatus according to claim 14, wherein pixels constituting the image are observed in a superimposed manner due to the shift of the image.
7. The image display device according to any one of 6. 18. An image display panel having a light source, a plurality of pixel regions each of which can modulate light, and a corresponding pixel of the plurality of pixel regions according to a wavelength range, which converts light from the light source into a wavelength range. A projection type image display device comprising: light control means for converging light on an area; and an optical system for forming an image on a projection surface by light modulated by the image display panel, wherein the image is formed. A circuit for generating data of a plurality of sub-frame images from data of each frame image, and causing the image display panel to display the plurality of sub-frame images in a time-division manner; and the plurality of sub-frames displayed by the image display panel The image shift element according to any one of claims 1 to 13, wherein a sub-frame image selected from images is shifted on the projection target surface. An image display device that sequentially irradiates the same area on the projection surface by the light belonging to different wavelength ranges that have been modulated in different pixel regions of the display panel.