JP3987346B2 - Optical deflection element, optical deflection device, and image display apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical deflection element, an optical deflection device, and an image display apparatus using the optical deflection element or the optical deflection device that change the direction of light according to an electric signal.
[0002]
[Definition]
In this specification, “light deflecting element” refers to whether the optical path of light is deflected by an external electric signal, that is, the outgoing light is shifted in parallel to the incident light, or is rotated at a certain angle. Alternatively, it means an optical element capable of switching the optical path by combining both of them.
[0003]
In this description, the “light deflection amount” is the amount of movement when the optical path or the optical axis is shifted in parallel or rotated. In particular, the magnitude of the shift is referred to as the “optical path shift amount” or simply “shift amount” for the optical deflection operation of the parallel shift, and the rotation amount is referred to as “optical path rotation angle” or simply “shift amount” for the optical deflection operation by rotation. It shall be called “rotation angle”. The “light deflection device” means a device that includes such a light deflection element and is a set of devices that shift or rotate an incident optical path in parallel.
[0004]
Further, the “pixel shift element” means an image display element in which a plurality of pixels that can control light according to image information is two-dimensionally arranged, a light source that illuminates the image display element, and an image displayed on the image display element An optical member for observing the pattern, and a light deflecting means for deflecting the optical path between the image display element and the optical member for each of a plurality of subfields obtained by dividing the image field in time. Means light deflecting means in an image display device that displays an image pattern in which the display position is shifted according to the deflection of the optical path for each field, thereby increasing the apparent number of pixels of the image display element. To do. Therefore, basically, it can be said that the optical deflection element and the optical deflection device defined above can be applied as the optical deflection means.
[0005]
[Prior art]
Conventionally, KH has been used as an optical element as a light deflection element₂PO₄(KDP), NH₄H₂PO₄(ADP), LiNbO₃, LiTaO₃, GaAs, CdTe, and other materials having a large primary electro-optic effect (Pockels effect), KTN, SrTiO₃, CS₂Electro-optical devices using materials with large secondary electro-optic effect such as nitrobenzene, glass, silica, TeO₂Acoustooptic devices using materials such as these are known (for example, Shoji Aoki; “Optoelectronic Device”, Shosodo). In general, in order to obtain a sufficiently large amount of light deflection, it is necessary to take a long optical path length, and the use is limited because the material is expensive.
[0006]
On the other hand, various types of optical elements, which are light deflecting elements using a liquid crystal material, have been proposed, and several examples thereof are as follows.
[0007]
For example, according to Japanese Patent Laid-Open No. 6-18940, a light beam shifter made of an artificial birefringent plate is proposed for the purpose of reducing the light loss of the optical space switch. Specifically, a light beam shifter in which two wedge-shaped transparent substrates are arranged in opposite directions, a liquid crystal layer is sandwiched between the transparent substrates, and the light beam shifter is connected to the rear surface of the matrix-type deflection control element. A beam shifter has been proposed. At the same time, two wedge-shaped transparent substrates are arranged in opposite directions, and a matrix drive is possible between the transparent substrates. There has been proposed a light beam shifter in which multiple stages are shifted by half a cell.
[0008]
Japanese Patent Laid-Open No. 9-133904 proposes an optical deflection switch that can obtain a large deflection, has a high deflection efficiency, and can arbitrarily set a deflection angle and a deflection distance. Yes. Specifically, two transparent substrates are arranged opposite to each other at a predetermined interval, a vertical alignment process is performed on the opposed surfaces, and a smectic A phase ferroelectric liquid crystal is sealed between the transparent substrates. The liquid crystal element includes a driving device that is vertically aligned with respect to the electrode pair, the electrode pair is arranged so that an AC electric field can be applied in parallel with the smectic layer, and the AC electric field is applied to the electrode pair. In other words, the refraction angle and the direction of displacement of the polarized light incident on the liquid crystal layer can be changed by the birefringence due to the inclination of the liquid crystal molecules by using the electroclinic effect of the smectic A phase ferroelectric liquid crystal.
[0009]
In the former Japanese Patent Application Laid-Open No. 6-18940, nematic liquid crystal is used as the liquid crystal material, so it is difficult to increase the response speed to sub-milliseconds. Can not.
[0010]
In the latter example of JP-A-9-133904, a smectic A-phase ferroelectric liquid crystal is used. However, since the smectic A-phase does not have spontaneous polarization, high-speed operation cannot be expected.
[0011]
Next, several techniques that have been conventionally proposed for the pixel shift element will be described.
[0012]
For example, as disclosed in Japanese Patent No. 2939826, in a projection display apparatus that projects an image displayed on a display element on a screen by a projection optical system, transmitted light is transmitted in the middle of an optical path from the display element to the screen. Means for shifting a projection image having at least one optical element capable of rotating the polarization direction of the light and at least one transparent element having a birefringence effect, and effectively reducing the aperture ratio of the display element And a means for discretely projecting the projection area of each pixel of the display element on the screen.
[0013]
In the example of the publication, a projection having at least one optical element (referred to as an optical rotatory element) capable of rotating the polarization direction and at least one transparent element (referred to as a birefringent element) having a birefringence effect. Pixel shift is performed by the image shift means (pixel shift means). However, the problem is that the optical rotation element and the birefringence element are used in combination, so the loss of light amount is large, and the pixel shift amount varies depending on the wavelength of light. The resolution tends to decrease, optical noise such as ghost due to leaked light tends to occur at positions outside the pixel shift where images are not originally formed due to mismatch in optical characteristics between the optical rotation element and the birefringence element, and for elementization. The cost of In particular, the KH as described above for the birefringent element₂PO₄(KDP), NH₄H₂PO₄(ADP), LiNbO₃, LiTaO₃This is remarkable when a material having a large primary electro-optic effect (Pockels effect) such as, GaAs, CdTe is used.
[0014]
In the projector disclosed in Japanese Patent Application Laid-Open No. 5-313116, the image to be originally displayed stored in the image storage circuit is sampled in a checkered pattern in the pixel selection circuit by the control circuit and sequentially displayed on the spatial light modulator. Then, the control circuit controls the panel rocking mechanism in correspondence with the display and moves the adjacent pixel pitch distance of the spatial light modulator by an integer by one. Is reproduced by temporal synthesis. As a result, an image can be displayed with a resolution that is an integral multiple of the pixels of the spatial light modulator, and a projector can be constructed at low cost by using a spatial light modulator with coarse pixels and a simple optical system.
[0015]
However, the example of the publication describes a pixel shift method in which the image display element itself is swung at a high speed by a distance smaller than the pixel pitch. In this method, the optical system is fixed, and various aberrations are thus eliminated. Although the occurrence is small, since the image display element itself needs to be translated accurately and at high speed, the accuracy and durability of the movable part is required, and vibration and sound become a problem.
[0016]
Further, according to Japanese Patent Laid-Open No. 6-324320, in order to improve the resolution of a display image apparently without increasing the number of pixels of an image display device such as an LCD, they are arranged in the vertical and horizontal directions. Each of the plurality of pixels emits light according to the display pixel pattern, and an optical member that changes the optical path for each field is disposed between the image display device on which the image is displayed and the observer or the screen. In addition, for each field, a display pixel pattern whose display position is shifted in accordance with the change of the optical path is displayed on the image display device. Here, the optical path is changed by causing the portions having different refractive indexes to appear alternately in the optical path between the image display device and the observer or the screen for each field of the image information. It is.
[0017]
In this example, a combination mechanism of an electro-optic element and a birefringent material, a lens shift mechanism, a vari-angle prism, a rotating mirror, a rotating glass, and the like are described as means for changing the optical path. In addition to the method of combining refractive elements, a method of switching optical paths by displacing (translating, tilting) optical elements such as lenses, reflectors, birefringent plates, etc. by voice coils, piezoelectric elements, etc. has been proposed. In this method, the configuration is complicated to drive the optical element, and the cost is increased.
[0018]
Further, according to Japanese Patent Laid-Open No. 10-133135, a light beam deflecting device that can eliminate the need for a rotating machine element, can achieve overall downsizing, high accuracy and high resolution, and is hardly affected by external vibrations. Has been proposed. Specifically, a translucent piezoelectric element disposed on the traveling path of the light beam, a transparent electrode provided on the surface of the piezoelectric element, a light beam incident surface A and a light beam emitting surface B of the piezoelectric element. Voltage applying means for applying a voltage to the piezoelectric element through the electrode in order to change the optical path length between and the electrode to deflect the optical axis of the light beam.
[0019]
In the example of the publication, a method is proposed in which a light-transmitting piezoelectric element is sandwiched between transparent electrodes and a thickness is changed by applying a voltage to shift the optical path. However, a relatively large transparent piezoelectric element is required. However, there is a problem similar to the case of the above-mentioned Japanese Patent Laid-Open No. 6-324320, such as an increase in apparatus cost.
[0020]
In JP-A-7-20417, the optical axis of emitted light is set in a predetermined direction by combining a ferroelectric liquid crystal cell exhibiting a chiral smectic C phase within a temperature range of −40 ° C. to 80 ° C. and a birefringent medium. There has been proposed an optical modulation element used for wobbling for shifting. According to this proposal, since the temperature range of the chiral smectic C phase is wide, it can be used in a wide range of temperature conditions and can be used even if the temperature difference is large, but the shift amount of the optical axis is controlled. There is a problem that it cannot be done.
[0021]
[Problems to be solved by the invention]
When the above-mentioned problems of the prior art are arranged, the problem with the conventional pixel shift element is that
(1) High cost due to the complicated structure, large equipment, light loss, ghost and other optical noise or resolution reduction
(2) Problems with position accuracy, durability, vibration and sound, especially in the case of configurations with moving parts
(3) Response speed in nematic liquid crystal
It is.
[0022]
Regarding the response speed of (3), the speed of light deflection required for pixel shift in the image display device can be estimated as follows. Image field (time t_Field) Is divided into n parts in time, and the optical path between the image display element and the optical member is deflected for each of n subfields to determine pixel shift shift positions at n locations. Time t_SFIs
t_SF= T_Field/ N
It is represented by This time t_SFThe light is deflected during the period of time t_shiftAnd this t_shiftSince the display cannot be performed during this period, the light use efficiency is reduced by an amount corresponding to this period.
[0023]
The light utilization efficiency E is expressed by the following formula.
E = (t_{science fiction}−t_shift) / T_SF
If the pixel shift position n is n = 4, the image field t_FieldIn order to ensure the light use efficiency E of 90% or more when is 16.7 ms,
0.9 <(16.7 / 4-t_shift) / (16.7 / 4)
t_shift<0.42 (ms)
Therefore, it is necessary to perform light deflection in 0.42 ms. Since a normal nematic liquid crystal has a response speed of several ms or more, it cannot be used as an optical element for high-speed pixel shift as shown here.
[0024]
In Japanese Patent Application Laid-Open No. 6-18940, nematic liquid crystal is used as the liquid crystal material, so it is difficult to increase the response speed to sub-milliseconds, and it cannot be used for pixel shift. On the other hand, the response speed of a ferroelectric liquid crystal composed of a chiral smectic C phase can be sufficiently set to 0.42 ms or less.
[0025]
In Japanese Patent Laid-Open No. 9-133904, a smectic A-phase ferroelectric liquid crystal is used. However, since the smectic A-phase does not have spontaneous polarization, high-speed operation as seen in the chiral smectic C-phase cannot be expected. .
[0026]
The object of the present invention is to solve the problems in the conventional optical deflection element, that is, the high cost, the size of the apparatus, the light loss and the optical noise due to the complicated structure, and the relatively large area with a simple structure. It is an object to provide an optical deflection element that can be realized.
[0027]
An object of the present invention is to provide an optical deflection device capable of obtaining a uniform optical path shift amount regardless of the location in the liquid crystal layer.
[0028]
An object of the present invention is to provide an optical deflection device capable of reliably performing optical switching by optical path deflection.
[0029]
An object of the present invention is to provide an optical deflection device capable of shifting light to a total of four positions.
[0030]
An object of the present invention is to provide an image display apparatus capable of obtaining a good image while maintaining an appropriate pixel shift amount.
[0031]
[Means for Solving the Problems]
An optical deflecting element according to the first aspect of the present invention is provided between a pair of transparent substrates, a liquid crystal layer filled between the two substrates to form a chiral smectic C phase under no electric field, and the two substrates. And a pair of electrode plates for generating an electric field with respect to the liquid crystal layer, wherein the pair of electrode plates are formed on the liquid crystal layer. The liquid crystal layer is provided substantially parallel to the thickness direction and is disposed opposite to the liquid crystal layer in a substantially central portion. The thickness of the liquid crystal layer is d, and the width of the electrode plate in the thickness direction of the liquid crystal layer is L. In this case, the liquid crystal layer thickness d and the electrode width L are
L> d
It is a relationship.
[0032]
Therefore, when the electrode width L is larger than the liquid crystal layer thickness d, the ratio of the electrode width L to the electrode spacing increases, so the electric field on the high voltage side decreases and an electric field is generated on the ground side. As a result, even when the effective area of the optical deflecting element is relatively large, the electric field strength of the horizontal electric field in the liquid crystal layer located substantially at the center of the electrode plate becomes relatively uniform, so that the area is relatively large with a simple configuration. It becomes possible to realize the optical deflection element.
[0033]
According to a second aspect of the present invention, in the optical deflection element according to the first aspect, when the interval between the electrode plates is D, the electrode interval D and the electrode width L are:
L ≧ D
It is a relationship.
[0034]
Therefore, when the electrode width L is greater than or equal to the electrode interval D, the uniformity of the electric field strength is improved, and the electric field difference is within 10%. As a result, the electric field strength of the horizontal electric field in the liquid crystal layer located substantially at the center of the electrode plate becomes substantially uniform, so that even when the effective area of the optical deflection element is large, the deflection amount of the optical path can be made substantially constant. It becomes possible.
[0035]
An optical deflection device according to a third aspect of the invention includes the optical deflection element according to the first or second aspect, and voltage applying means for applying a voltage between a pair of electrode plates provided in the optical deflection element. When the electric field strength at which the increasing tendency of the optical path deflection amount saturates with respect to the increase is defined as the saturation electric field Es, the voltage application is performed so that the electric field strength in the entire liquid crystal layer of the optical deflection element is equal to or higher than the saturation electric field Es Set the output of the means.
[0036]
Therefore, even if there is some non-uniformity in the electric field strength of the horizontal electric field in the liquid crystal layer located at the approximate center of the electrode plate, a uniform optical path shift amount can be obtained regardless of the location in the liquid crystal layer. Become.
[0037]
According to a fourth aspect of the present invention, in the optical deflection device according to the third aspect, the optical deflection device is disposed on a light incident side of the optical deflection element so that a light deflection direction of the light deflection element coincides with a polarization direction of incident light. And a polarization direction control means for controlling the polarization direction of the incident light.
[0038]
Therefore, even when the incident light is non-polarized light components that are not subjected to the optical path deflection action due to the tilt of the liquid crystal molecules are cut, so that optical switching by the optical path deflection can be performed reliably.
[0039]
According to a fifth aspect of the present invention, in the optical deflection device according to the third or fourth aspect, the polarization plane rotating means for rotating the polarization plane of the outgoing light of the light deflection element substantially at right angles, and the polarization plane by the polarization plane rotating means A second optical deflection element that uses the rotated outgoing light as incident light, and the optical deflection element and the second optical deflection element substantially coincide with the normal direction of the liquid crystal layer of both optical deflection elements The electric field directions of both optical deflection elements are arranged so as to be substantially orthogonal.
[0040]
Therefore, two light deflecting elements capable of deflecting in one direction are combined and arranged by rotating the electric field application direction by 90 degrees, and the deflection surface of the light emitted from the light deflecting element on the incident side is rotated by 90 degrees. And is incident on the second optical path deflecting element. As a result, the optical deflection element is shifted in two positions in the vertical direction (Z-axis direction) and in the second optical deflection element in the horizontal direction (Y-axis direction). It is possible to shift the light.
[0041]
According to a sixth aspect of the present invention, there is provided an image display device in which a plurality of pixels capable of controlling light according to image information are two-dimensionally arranged, a light source that illuminates the image display device, and the image display device. An optical member for observing a displayed image pattern, display driving means formed by a plurality of subfields obtained by temporally dividing an image field, and deflecting an optical path between the image display element and the optical member. And an optical deflecting means which is the optical deflecting device according to any one of claims 3 to 5.
[0042]
Therefore, an image pattern in which the display position is shifted according to the deflection state of the optical path for each of the plurality of subfields obtained by temporally dividing the image field by the light deflection unit is displayed, and the apparent number of pixels of the image display element By multiplying and displaying the image, it is possible to provide an image display device that apparently has high definition and high light utilization efficiency using an image display element having a small number of pixels. Further, in particular, the optical deflection element which is the optical deflection element according to claim 1 or 2 or the optical deflection device according to any one of claims 3 to 5 is used, and the optical deflection position control is performed by an electrode pair in the optical deflection unit. By performing according to the electric field application direction and electric field strength, it is possible to maintain an appropriate pixel shift amount and obtain a good image.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS.
[0044]
1A and 1B are explanatory views showing an example of the basic configuration of the optical deflection element 1 according to the present embodiment, wherein FIG. 1A is a longitudinal side view, FIG. 1B is a longitudinal front view, and FIG. 1C is a top view. . As shown in FIG. 1 (a), in this optical deflection element 1, first, a pair of transparent substrates 2 are provided so as to face each other with a spacer 3 interposed therebetween. A vertical alignment film 4 is formed on the inner surface of at least one of the substrates 2 (in this embodiment, the substrate 2 side positioned on the light incident side). The vertical alignment film 4 and the other substrate 2 are formed. (In this embodiment, a liquid crystal that is a ferroelectric liquid crystal having a thickness d (several tens of μm to several hundreds of μm) capable of forming a chiral smectic C phase with the substrate 2 positioned on the light emission side). Layer 5 is filled.
[0045]
As shown in FIG. 1B, for a structure having such a pair of substrates 2 and liquid crystal layer 5, a pair of electrodes 6 by electrode plates 6a and 6b corresponding to the intended light deflection direction. Is connected to a power source 7 that functions as voltage applying means for applying a voltage between the electrode plates 6a and 6b. As shown in FIG. 1C, the electrode thickness of the electrode plates 6a and 6b is t, and the electrode width of the electrode plates 6a and 6b is L. Further, the electrode interval between the electrode plates 6a and 6b is D (about several mm to several tens mm). The electrode plates 6 a and 6 b are installed so that the electric field vector is oriented in a direction substantially perpendicular to the deflection direction of the optical deflection element 1. When the traveling direction of light by light deflection is desired to be swung in three or more directions, the polarization direction of incident light is rotated corresponding to the deflection direction, and a plurality of electrode pairs 6 are also provided corresponding to them.
[0046]
In the present embodiment, the electrode width L of the electrode plates 6a and 6b is made larger than the liquid crystal layer thickness d of the liquid crystal layer 5, and the position of the liquid crystal layer 5 is approximately the center with respect to the thickness direction of the liquid crystal cell. 6b was placed. With this configuration, the ratio of the electrode width L of the electrode plates 6a and 6b to the electrode interval D between the electrode plates 6a and 6b becomes relatively large, so that the electric field strength between the electrodes becomes relatively uniform. The relationship between the electrode width L and the electric field uniformity will be described in detail later.
[0047]
The incident light is deflected by the direction of the electric field formed by the electrode pair 6 (indicated by the white arrow in FIG. 1) based on the principle of operation described later, and either the first emitted light or the second emitted light is obtained. Take the light path.
[0048]
Here, the liquid crystal layer 5 will be described. A “smectic liquid crystal” is a liquid crystal phase in which the major axis directions (liquid crystal director directions) of liquid crystal molecules are substantially aligned, and the molecules are arranged in layers while maintaining the same direction. With regard to such a liquid crystal, a liquid crystal phase in which the major axis direction of the liquid crystal molecules coincides with the normal direction (layer normal direction) of the layer is referred to as “smectic A phase”, and the major axis direction of the liquid crystal molecules is the layer direction. A liquid crystal phase that does not coincide with the normal direction (layer normal direction) of the liquid crystal and is tilted is called a “smectic C phase”. This tilt angle of the liquid crystal director is called a tilt angle θ. The liquid crystal directors in each layer face the same direction of the tilt angle θ. In the case of having a permanent dipole component in a direction perpendicular to the major axis of the liquid crystal molecule, it is considered that ferroelectricity is manifested because the spontaneous polarization Ps exists due to this tilt angle θ. Optical characteristics are controlled by rearranging liquid crystal molecules in a direction determined by the spontaneous polarization Ps and the external electric field E.
[0049]
In general, since a liquid crystal material that exhibits ferroelectricity has asymmetric carbon in its molecular structure, the direction of the azimuth angle of the liquid crystal director is helically rotated for each layer in a state where the external electric field E does not work. It has a so-called helical structure, and is called “chiral smectic C phase”. In addition, in the antistimulable liquid crystal of the chiral smectic C phase, the azimuth angles of the liquid crystal directors face each other in the respective layers.
[0050]
In the present embodiment and the like, the light deflection element 1 will be described by taking a ferroelectric liquid crystal as an example of the liquid crystal layer 5, but the same can be used for an anti-ferroelectric liquid crystal.
[0051]
The molecular structure of the liquid crystal material capable of forming the “chiral smectic C phase” is composed of a main chain, a spacer, a skeleton, a bonding part, a chiral part, and the like. As the main chain structure, polyacrylate, polymethacrylate, polysiloxane, polyoxyethylene and the like can be used. The spacer is for linking a skeleton, a bonding part, and a chiral part responsible for molecular rotation to the main chain, and a methylene chain having an appropriate length is selected. In addition, a —COO— bond or the like is selected as a bond portion that bonds the chiral portion and a rigid skeleton such as a biphenyl structure.
[0052]
The liquid crystal material used in this embodiment transitions from a crystalline phase to a chiral smectic C phase at a temperature of about room temperature or lower, and from a chiral smectic C phase to a smectic A phase at a relatively high temperature range of about 50 ° C. to 100 ° C. Metastasize. When the temperature is further increased, an isotropic phase is obtained via a chiral nematic phase. Alternatively, a material that directly transitions from a chiral smectic C phase to a chiral nematic phase at about 50 ° C. to 100 ° C. can be used. In order to set a wide usable temperature range of the optical deflecting element 1 of the present embodiment, it is preferable that the temperature range of the chiral smectic C phase is wide, but if it is too wide, the isotropic phase transition point and the like are also increased in temperature. The processing temperature of the substrate when the liquid crystal layer 5 is injected into the light deflection element 1 becomes too high, which is not preferable. Considering the operating temperature range of the light deflection element 1, it was determined that the upper limit temperature of the chiral smectic C phase is preferably between 50 ° C and 100 ° C.
[0053]
When a conoscopic image is observed with a polarizing microscope from the normal direction of the chiral smectic C phase liquid crystal layer 5 under no electric field, the cross image is located in the center and has a uniaxial optical axis. Can be confirmed. Here, FIG. 2 shows a model of a helical structure change caused by an electric field of liquid crystal molecules. As shown in FIG. 2A, in the electric field E = 0, the liquid crystal director direction is spatially averaged by the symmetrical spiral structure. The averaged optical axis of the liquid crystal layer 5 faces the normal direction of the layer, and is optically isotropic with respect to incident light parallel to the optical axis. Next, when a relatively small electric field 0 <E <Es is applied in the horizontal direction of the liquid crystal layer 5, as shown in FIG. 2B, a rotational moment is generated in the liquid crystal molecules by the action of the electric field E on the spontaneous polarization Ps. Therefore, the helical structure is distorted and asymmetric, and the average optical axis is tilted in one direction. At this time, distortion increases as the electric field strength increases, and the average tilt angle of the optical axis also increases. This can be confirmed from the movement of the cross image of the conoscopic image. When the electric field strength is further increased, as shown in FIG. 2C, the spiral structure disappears at a certain threshold electric field Es or more and becomes optically uniaxial. The tilt angle of the optical axis at this time is equal to the tilt angle θ of the liquid crystal director. Further, even if the electric field is increased, the tilt angle θ does not change, and the tilt angle of the optical axis becomes constant.
[0054]
In the light deflecting element 1 of the present embodiment, the liquid crystal layer 5 made of a chiral smectic C phase has a rotation axis of molecular helix rotation perpendicular to the surface of the substrate 2 by the vertical alignment film 4 and has a so-called homeotropic alignment. . As an alignment method for such homeotropic alignment, a conventionally performed method can be applied. (1) shear stress method, (2) magnetic field orientation method, (3) temperature gradient method, (4) SiO oblique deposition method, (5) photo-alignment method, etc. (for example, Takezoe, Fukuda "Structure and physical properties of dielectric liquid crystals", see Corona, p235).
[0055]
One of the features of the optical deflection element 1 of the present embodiment is that the configuration is simple and the manufacturing cost can be suppressed. Further, the chiral smectic C phase has an extremely high speed response compared to the smectic A phase and nematic liquid crystal, and is characterized in that switching in sub-milliseconds is possible. In particular, since the liquid crystal director direction is uniquely determined with respect to the electric field direction, control of the director direction is easier and easier to handle than a liquid crystal composed of a smectic A phase.
[0056]
In addition, the liquid crystal layer 5 made of the homeotopic-oriented chiral smectic C phase used in the present embodiment has a liquid crystal structure as compared with a case where the liquid crystal layer 5 has a homogeneous orientation (a state in which the liquid crystal director is oriented parallel to the surface of the substrate 2). The operation of the director is less susceptible to the regulation force from the substrate 2, the light deflection direction can be easily controlled by adjusting the direction of the external electric field, and the required electric field is relatively low. Further, when the liquid crystal directors are homogeneously oriented, the liquid crystal directors strongly depend not only on the direction of the electric field but also on the substrate surface, so that more positional accuracy is required for the installation of the light deflection element 1. Conversely, in the case of homeotopic orientation as in the present embodiment, the setting margin of the optical deflection element 1 increases with respect to optical deflection. In making use of these features, it is not necessary that the spiral axis be strictly oriented perpendicular to the substrate surface, and it may be tilted to some extent. It suffices if the liquid crystal director can face two directions without receiving the regulating force from the substrate 2.
[0057]
Next, the principle of operation of the optical deflection element 1 of the present embodiment will be described with reference to FIGS. FIG. 3 schematically shows the alignment state of the liquid crystal molecules shown in FIG. 1 in order to explain the operation principle of the optical deflection element. In FIG. 3, for the sake of convenience, a voltage is applied in the front and back direction of the paper, and the electric field is generated in the front and back direction of the paper. The electric field direction is switched by the power source 7 in accordance with the target light deflection direction.
[0058]
In addition, the incident light with respect to the light deflection element 1 is linearly polarized light, and the polarization direction thereof is the vertical direction as shown by the upper and lower arrows in FIG. 3, and the electrode plates 6a, 6a, 6b is oppositely arranged. Although not shown, it is preferable to provide an electromagnetic shield so that the leakage electric field from the electrodes 6a and 6b does not adversely affect the devices around the optical deflection element 1.
[0059]
When the XYZ orthogonal coordinate system is taken as shown in FIG. 3 and a sufficiently large electric field is applied in the Y-axis direction, the liquid crystal director 8 as shown in FIG. Depending on the electric field direction, the first orientation state or the second orientation state (see FIG. 4B) is distributed. Here, it is considered that the liquid crystal director 8 can rotate along a virtual cone shape by the tilt angle θ. Assuming that the spontaneous polarization Ps of the liquid crystal is positive and the electric field E is applied in the positive Y-axis direction (upward on the paper surface), the rotation axis of the liquid crystal director 8 is in the XZ plane because it is substantially perpendicular to the substrate. When the refractive index in the major axis direction of the liquid crystal molecules is ne and the refractive index in the minor axis direction is no, as the incident light, linearly polarized light having the polarization direction in the Y axis direction is selected, and when the incident light advances in the X axis positive direction, In the liquid crystal layer 5, light undergoes a refractive index no as ordinary light and travels straight in the direction a in FIG. That is, no light deflection is received.
[0060]
On the other hand, when linearly polarized light whose polarization direction is the Z-axis direction is incident, the refractive index in the incident direction is obtained from both the direction of the liquid crystal director 8 and the refractive indexes no and ne. More specifically, the refractive index ellipsoid having refractive indexes no and ne as main axes is obtained from the relationship with the direction of light passing through the center of the ellipsoid, but the description thereof is omitted here. The light is deflected corresponding to the refractive indexes no and ne and the direction of the average liquid crystal director 8 (averaged tilt angle = tilt angle θ of the optical axis), and b (first alignment) in FIG. Shift in the direction shown in the case of the state).
[0061]
In the above description, the case where the electric field strength is Es or more and the spiral structure is unwound and the tilt angle θ is equal to the tilt angle of the optical axis has been described. However, when the electric field strength is equal to or less than Es, the θ is the liquid crystal director direction. May be treated as the averaged tilt angle of the optical axis.
[0062]
Next, the relationship between the tilt angle θ (optical axis tilt angle) and the optical path shift amount will be described. When the thickness (gap) of the liquid crystal layer 5 is d, the shift amount S is expressed by the following equation (see, for example, “Crystal Optics” Applied Physics Society, Optical Society, p198).
S = [(1 / no)²− (1 / ne)²] sin (2θ · d) ÷ [2 ((1 / ne)²sin²θ + (1 / no)²cos²θ)] ……… Equation 1
When the electric field direction is reversed, the liquid crystal director 8 takes a line-symmetrical arrangement (second alignment state) about the X axis in FIG. 4 and the traveling direction of linearly polarized light whose polarization direction is the Z axis direction. Is as shown by b 'in FIG.
[0063]
Therefore, by controlling the direction of the electric field applied to the liquid crystal layer 5 with respect to this linearly polarized light, it is possible to deflect light at two positions b and b ′, that is, 2S. For example, in Equation 1
no = 1.60
ne = 1.80
d = 32 μm
FIG. 5 shows the result of calculating the change in the optical path shift amount S with respect to the tilt angle θ. As shown in FIG. 5, when the tilt angle θ of the liquid crystal director 8 is 22.5 °, a deflection amount of 2S = 5 (μm) can be obtained.
[0064]
In the optical deflecting element 1 of the present embodiment, the electrode interval D between the electrode plates 6a and 6b is several mm to several tens with respect to a relatively thin liquid crystal layer 5 having a thickness d of about several tens to several hundreds of μm. Since it is sufficiently wide as mm, it is difficult to apply a uniform electric field between the electrodes when the electrode width L in the element thickness direction is small. In such a configuration, the electric field strength in the horizontal direction in the liquid crystal layer tends to be a high electric field in the vicinity of the electrode on the high voltage side and a low electric field in the vicinity of the electrode on the ground side. It is suggested from the results.
[0065]
Here, an example of the electric field simulation result is shown in FIG. Here, the calculation was performed assuming that the two glass substrates 2 were 3 mm thick, the liquid crystal layer 5 was d = 40 μm, the relative dielectric constant of the glass substrate 2 was 8, and the dielectric constant of the liquid crystal layer 5 was 20. In FIG. 6, three types of configurations ((1) to (3)) are compared. In any case, the electrode distance D between the electrode plates 6a and 6b is 18 mm, and the electrode thickness t of the electrode plates 6a and 6b is It is 1 mm, and the electrode width L is changed. The horizontal axis in FIG. 6 indicates the position between the electrodes, a high voltage of 2000 V is applied to the 0 mm position, and the 18 mm position is grounded. The vertical axis represents the horizontal electric field strength at the center of the liquid crystal layer.
[0066]
In the configuration example (1), the electrode plate is also used as a spacer, and the electrode width L is 40 μm which is equal to the liquid crystal layer thickness d. In this way, when D >> L = d, as described above, the high voltage electrode side has a high electric field, and the ground side has almost no electric field.
[0067]
Configuration example (2) is an example of this embodiment, and an electrode plate of L = 6 mm is provided on the side surface of the element. Here, the spacer 3 is omitted. When the electrode width L is larger than the liquid crystal thickness d and the ratio of the electrode width L to the electrode spacing D is increased, the electric field on the high voltage side decreases and an electric field is generated on the ground side. Here, an example in which the electrode width L is equal to the thickness of the element is shown, but if L> d, an effect of improving the uniformity of the electric field strength can be obtained.
[0068]
The configuration example (3) is another example of the present embodiment, and an electrode plate of L = 18 mm is provided on the side surface of the element. Thus, when L = D, the uniformity of the electric field strength is improved, and the difference in electric field depending on the location is about 10%. Since uniformity is further improved when L> D, if L ≧ D, the difference in electric field is within 10%, and a substantially uniform optical path shift amount can be obtained even if the area of the optical deflection element is large.
[0069]
By the way, when the optical path shift amount has electric field dependency, the optical path shift amount varies depending on the position in the element. Here, FIG. 7 is a graph showing a measurement example of the electric field strength dependence of the optical path shift amount of the optical deflection element 1. As shown in FIG. 7, in the optical deflection element 1, the optical path shift amount increases as the electric field strength increases, and the optical path shift amount is substantially constant at the saturation electric field Es = 100 V / mm or more. Therefore, in the present embodiment, when the electric field intensity at which the increasing tendency of the optical path shift is saturated with respect to the increase in the electric field is defined as the saturated electric field Es, the electric field intensity in the entire liquid crystal layer 5 of the optical deflection element 1 is greater than Es. The output of the voltage applying means is set so that
[0070]
That is, the configuration example (3) shown in FIG. 6 will be described as an example. In the configuration example (3), the electric field strength on the right side in FIG. 6 is relatively small, but the electric field strength at this position is the saturation electric field Es. By setting the voltage value to be applied to the whole so as to be equal to or higher than 100 V / mm, a uniform optical path shift amount can be obtained regardless of the location.
[0071]
In the above description, the temperature of the liquid crystal layer 5 is described under a constant condition. However, depending on the type of the liquid crystal layer 5, the temperature dependence of the optical path shift amount may be large. For example, in a liquid crystal composed of a chiral smectic C phase, the tilt angle θ changes with temperature T, and the phase transition point is Tc.
θ∝ (T−Tc)^β                                  ......... Formula 2
There is a relationship. β varies depending on the material, but takes a value of about 0.3 to 0.5.
[0072]
Therefore, in such a case, it is preferable to provide temperature control means for controlling the temperature of the optical deflection element 1 uniformly and uniformly. As temperature control of the liquid crystal layer 5, it is only necessary to monitor the temperature of the light deflection element 1 and provide feedback so as to operate a heating source or a cooling source for reducing the difference from the set temperature. Further, the heating / cooling source may be operated so as to reduce the difference from the normal position by monitoring the light deflection position instead of monitoring the temperature. As a heating source, a heating source may be provided outside the optical deflection element 1, but in order to reduce the size, a resistance wire is formed in contact with the inside or the surface of the optical deflection element 1 and obtained by passing a current through the resistance line. Preferably, Joule heat is used. A Peltier element or the like is preferably used as the cooling source.
[0073]
Here, when the electrode width L becomes larger than the liquid crystal layer thickness d, the ratio of the electrode width L to the electrode spacing increases, so the electric field on the high voltage side decreases and an electric field is generated on the ground side. As a result, even when the effective area of the optical deflection element 1 is relatively large, the electric field strength of the horizontal electric field in the liquid crystal layer 5 located at the substantially central portion of the electrode plate 6 becomes relatively uniform. It is possible to realize a light deflection element 1 having a large area.
[0074]
In addition, when the electrode width L is greater than or equal to the electrode spacing D, the uniformity of the electric field strength is improved, and the electric field difference is within 10%. As a result, the electric field strength of the horizontal electric field in the liquid crystal layer 5 positioned substantially at the center of the electrode plate 6 becomes substantially uniform. Therefore, even when the effective area of the optical deflection element 1 is large, the deflection amount of the optical path is made substantially constant. It becomes possible to do.
[0075]
In the present embodiment, the electrode plates 6a and 6b have been described as being in the form of a single plate. However, the present invention is not limited to this, and an electrode plate group in which a plurality of electrodes are arranged is an electrode plate 6a, It may be 6b. The plurality of electrode plates constituting the electrode plate group may be in contact with each other or may be installed at a desired interval. In this case, the total length of the electrode plate group in which a plurality of electrodes are arranged is handled as the electrode width L.
[0076]
Next, a second embodiment of the present invention will be described with reference to FIG. Portions that are the same as or correspond to those in the above-described embodiment are denoted by the same reference numerals, and description thereof is also omitted (the same applies to subsequent embodiments).
[0077]
FIG. 8 is a schematic perspective view showing the optical deflection device 10 of the present embodiment together with the schematic liquid crystal alignment of the optical deflection element. As shown in FIG. 8, the present embodiment is a combination of two light deflection elements 1A and 1B configured as in the above-described embodiment and a half-wave plate 9 which is a polarization plane rotating means. The optical deflection device 10 is configured as follows. In FIG. 8, the substrate 2, the spacer 3, the vertical alignment film 4 and the like are omitted.
[0078]
As shown in FIG. 8, the light deflection elements 1A and 1B are arranged in series in the light traveling direction with the electric field generation directions by the respective electrode pairs 6 orthogonal to each other, and 1 between these light deflection elements 1A and 1B. A / 2 wavelength plate 9 is disposed. As the half-wave plate 9, a commercially available one for visible light can be applied as it is.
[0079]
As shown in FIG. 8, the light incident on the optical deflection device 10 is deflected in the vertical direction (Z-axis direction) in the optical deflection element 1A on the front stage side with respect to the light traveling direction, and then the half-wave plate 9, the polarization direction is rotated by 90 ° to obtain the polarization direction in the Y-axis direction, so that it is deflected in the left-right direction (Y-axis direction) by the subsequent optical deflection element 1B.
[0080]
According to such an optical deflection device 10, the optical deflection is performed at two positions in the vertical direction (Z-axis direction) in the optical deflection element 1A and at two positions in the horizontal direction (Y-axis direction) in the optical deflection element 1B. As a whole device, light can be shifted to a total of four positions.
[0081]
In the optical deflecting device 10 of the present embodiment, only the linearly polarized light in the polarization direction parallel to the direction of the optical path deflection, that is, the tilt direction of the liquid crystal molecules when an electric field is applied, is subjected to the optical path deflection, and the straight line orthogonal thereto. The polarization remains straight. Therefore, when non-polarized light is incident, since the outgoing light includes a component that is not deflected, the contrast with respect to the presence or absence of optical path deflection is lowered. Therefore, a polarization direction control unit that matches the polarization direction of the incident light to the optical deflection element 1A with the average tilt direction of the optical axis of the liquid crystal layer may be provided. As the polarization direction control means, a linear polarizing plate can be used. The linear polarizing plate is placed on the incident surface side of the light deflection element 1A so that the polarization direction of the linear polarizing plate is aligned parallel to the longitudinal direction of the transparent electrode line or the electrode plate 6. Even when the incident light is non-polarized light, the light component that is not subjected to the optical path deflection action due to the tilt of the liquid crystal molecules is cut, so that the optical switching by the optical path deflection can be surely performed.
[0082]
A third embodiment of the present invention will be described with reference to FIG. This embodiment shows an application example to an image display device.
[0083]
Here, FIG. 9 is a schematic side view showing a configuration example of the image display device 41. In FIG. 9, reference numeral 42 denotes a light source in which LED lamps are arranged in a two-dimensional array. In the traveling direction of light emitted from the light source 42 toward the screen 43, a diffusion plate 44, a condenser lens 45, and an image display element are used. A transmissive liquid crystal panel 46 and a projection lens 47 as an optical member for observing the image pattern are sequentially arranged. Reference numeral 48 denotes a light source drive unit for the light source 42, and 49 denotes a drive unit for the transmissive liquid crystal panel 46.
[0084]
Here, on the optical path between the transmissive liquid crystal panel 46 and the projection lens 47, an optical deflecting unit 50 functioning as a pixel shift element is interposed and connected to the drive unit 51. As such an optical deflection means 50, the optical deflection element 1, the optical deflection device 10, or the like as described above is used.
[0085]
The illumination light that is controlled by the light source drive unit 48 and emitted from the light source 42 becomes illumination light that is made uniform by the diffusion plate 44, and is controlled by the condenser lens 45 in synchronization with the illumination light source by the liquid crystal drive unit 49. The liquid crystal panel 46 is critically illuminated. The illumination light spatially modulated by the transmissive liquid crystal panel 46 enters the light deflecting unit 50 as image light. The light deflecting unit 50 shifts the image light by an arbitrary distance in the pixel arrangement direction. In this case, since the effective area of the light deflection means 50 needs to be relatively large, it is important to apply a uniform horizontal electric field. That is, according to the image display device 41 of the present embodiment, the light deflection element 1 described in the first embodiment and the light deflection device 10 described in the second embodiment are used as the light deflection means 50. It is possible to apply a uniform horizontal electric field with a relatively large area. The light transmitted through the light deflecting means 50 is enlarged by the projection lens 47 and projected onto the screen 43.
[0086]
Although not described in detail because it is a well-known technique, the control unit (not shown) of the image display device 41 has a function (display driving means) for forming an image field by a plurality of subfields divided in time. ing.
[0087]
An image pattern in which the display position is shifted in accordance with the deflection of the optical path for each of a plurality of subfields obtained by temporally dividing the image field by the light deflecting unit 50 is displayed. The number of apparent pixels is multiplied and displayed. Thus, the shift amount by the light deflecting means 50 is set to ½ of the pixel pitch because the image multiplication is performed twice in the pixel arrangement direction of the transmissive liquid crystal panel 46. By correcting the image signal for driving the transmissive liquid crystal panel 46 according to the shift amount by the shift amount, an apparently high-definition image can be displayed. At this time, since the light deflection element or the light deflection device as in each of the above-described embodiments is used as the light deflection means 50, the light utilization efficiency is improved, and the observer can increase without increasing the load on the light source. Bright and high quality images can be provided. By performing the optical deflection position control based on the electric field application direction and electric field intensity by the electrode pair 6 in the optical deflection element 1, an appropriate pixel shift amount can be maintained and a good image can be obtained.
[0088]
【Example】
Some examples configured according to the above-described embodiments will be listed below. However, the present invention is not limited to these.
[0089]
[Example 1]
The vertical alignment film 4 was formed by treating the surface of the glass substrate 2 having a size of 2 cm × 2.5 cm and a thickness of 3 mm with a silane coupling agent. Two mylar sheets having a thickness of 40 μm, a width of 1 mm, and a length of 2 cm were used as spacers 3, and the two glass substrates 2 were bonded to each other with the vertical alignment film 4 as an inner surface and shifted by 5 mm in one direction. The spacer 3 was disposed at the edge of the substrate at the shifted portion. The shifted portion was fixed with an adhesive. While the substrate 2 was heated to about 90 degrees, a ferroelectric liquid crystal (Chisso CS1029) 5 (not shown) was injected between the two substrates 2 by a capillary method. After cooling, an aluminum electrode plate 6 was attached to both side portions of the cell that became the injection portion with an adhesive, and the liquid crystal layer 5 was sealed and the electrode was formed. The aluminum electrode plate 6 had a thickness of 1 mm, a length of 20 mm, and a width of 6 mm, and the light deflection element 1 as shown in FIG. 10 was prepared.
[0090]
A mask pattern having a line / space width of 24.5 μm was provided on the incident surface side of the light deflection element 1, and illumination was performed with linearly polarized light collimated from the mask pattern side. The direction of linearly polarized light was set to be the same as the longitudinal direction of the aluminum electrode plate 6. In the state where the temperature of the light deflection element 1 is 25 ° C., the light transmitted through the mask pattern was observed through the light deflection element 1 with a microscope.
[0091]
When a rectangular voltage of ± 4 kV was applied between the aluminum electrode plates 6 using a pulse generator and a high-speed power amplifier, the mask pattern was observed to be shifted by about 8 μm in parallel at the center of the element. Since the mask pattern, the light deflection element 1, and the microscope are mechanically stationary, it has been confirmed that the optical path shifts electro-optically. When the shift amount was measured at a plurality of locations in the optical deflection element 1, the shift amount was constant at about 8 μm in the area of about 10 mm square at the center of the element, but the shift amount was about 5 mm from the periphery of the element. Was 8 μm or less, and about 4 μm at the end of the device.
[0092]
In the present embodiment, the light deflection element 1 having a simple configuration and an effective area of the optical path shift of about 10 mm square is obtained.
[0093]
[Example 2]
The light deflection element 1 was produced in the same manner as in Example 1 except that the width of the aluminum electrode plate 6 was changed. As shown in FIG. 11, the aluminum electrode plate 6 has a thickness of 1 mm, a length of 20 mm, and a width of 20 mm. That is, in this embodiment, the electrode interval D = the electrode plate width L = 20 mm.
[0094]
A mask pattern having a line / space width of 24.5 μm was provided on the incident surface side of the light deflection element 1, and illumination was performed with linearly polarized light collimated from the mask pattern side. The direction of linearly polarized light was set in the same manner as in Example 1. In the state where the temperature of the light deflection element 1 is 25 ° C., the light transmitted through the mask pattern was observed through the light deflection element 1 with a microscope.
[0095]
When a rectangular voltage of ± 3 kV was applied between the aluminum electrode plates 6 using a pulse generator and a high-speed power amplifier, the mask pattern was observed to be shifted by about 8 μm in parallel at the center of the element. Since the mask pattern, the light deflection element 1, and the microscope are mechanically stationary, it has been confirmed that the optical path shifts electro-optically. When the shift amount was measured at a plurality of locations in the optical deflection element 1, the shift amount was constant at about 8 μm over the entire area of the element.
[0096]
In this embodiment, the size of the element is relatively large, but the light deflecting element 1 having a wide optical path shift effective area of about 20 mm square is obtained.
[0097]
[Example 3]
An image display device as shown in FIG. 9 was created. A diagonal TFT 0.9 inch XGA (1024 × 768 dots) polysilicon TFT liquid crystal light valve was used as an image display element. The pixel pitch is about 18 μm both vertically and horizontally. The aperture ratio of the pixel is about 50%. Further, a microlens array is provided on the light source side of the image display element to increase the collection rate of illumination light. In this embodiment, an RGB three-color LED light source is used as a light source, and a so-called field sequential method is adopted in which color display is performed by switching the color of light irradiated to the one liquid crystal panel at a high speed. In this embodiment, it is assumed that the frame frequency of image display is 60 Hz, and the subfield frequency for pixel multiplication by 4 times by pixel shift is 240 times, which is 4 times. In order to further divide one subframe into three colors, an image corresponding to each color is switched at 720 Hz. A full color image can be seen by an observer by turning ON / OFF the LED light source of the corresponding color in accordance with the display timing of each color image on the liquid crystal panel.
[0098]
The basic configuration of the light deflection element is the same as that of Example 2, but the thickness of the mylar sheet is 45 μm and the thickness of the liquid crystal layer is about 45 μm. Also, an air blowing fan was provided, and air cooling was performed so that the temperature of the light deflection element was 25 ° C., which is the same as the outside air temperature.
[0099]
Two sets of light deflection elements were used, the incident side being the first light deflection element and the emission side being the second light deflection element. The transparent electrode lines are arranged so that the directions of the transparent electrode lines are orthogonal to each other and coincide with the arrangement direction of the pixels of the image display element. In this embodiment, the light emitted from the liquid crystal light valve is already linearly polarized light and the direction of polarization is arranged so as to coincide with the light path deflection direction of the first light path deflecting element. In order to ensure the degree of polarization, a linearly polarizing plate was provided as a polarization direction control means on the incident surface side of the optical path deflecting element.
[0100]
Further, a polarization plane rotating element is provided between the first and second optical path deflecting elements. For the polarization plane rotation element, a polyimide alignment material was spin-coated on a glass substrate (3 cm × 4 cm, thickness 3 mm) to form an alignment film of about 0.1 μm. A rubbing treatment was performed after the annealing treatment of the glass substrate. An empty cell was fabricated by sandwiching an 8 μm thick spacer between the two glass substrates and pasting the upper and lower substrates so that the rubbing directions were orthogonal. Into this cell, a nematic liquid crystal having a positive dielectric anisotropy and an appropriate amount of a chiral material mixed was injected under normal pressure to produce a TN liquid crystal cell in which the orientation of liquid crystal molecules was twisted by 90 degrees. Since this cell is not provided with an electrode, it functions as a simple polarization rotation element. In addition, discharge between the aluminum electrodes of both optical deflection elements is prevented. The polarizing plate of light emitted from the first optical path deflecting element and the incident surface of the polarization rotating element are arranged so as to be sandwiched between two optical path deflecting means so that the rubbing directions of the incident surface of the polarizing rotating element coincide with each other. The polarization plane of the light emitted from the first optical path deflection element is rotated by 90 degrees by the polarization plane rotation element, and coincides with the deflection direction of the second optical path deflection element. A light deflecting device comprising a first light deflecting element, a polarization plane rotating element, and a second light deflecting element was installed immediately after the liquid crystal light valve.
[0101]
The light deflection element is cooled to about 25 ° C. with a blower fan, the voltage of the rectangular wave voltage for driving the light deflection element is ± 3 kV (average electric field is ± 150 V / mm), the frequency is 120 Hz, and the two light deflection elements are The drive timing was set so that the vertical and horizontal phases were shifted by 90 degrees and the pixels were shifted in four directions. With this driving voltage, the optical path shift amount is about 9 μm, and the pixels are displayed by being shifted by ½ pixel. By rewriting the subfield image displayed on the image display device at 240 Hz, an image in which the apparent number of pixels in the vertical and horizontal directions was quadrupled could be displayed. The pixel shift amount was uniform from the center to the edge of the image, and a high-definition image was obtained. The switching time of the optical path deflecting element was about 0.2 msec, and sufficient light utilization efficiency was obtained. Also, no flicker was observed.
[0102]
【The invention's effect】
According to the optical deflecting element of the first aspect of the present invention, a pair of transparent substrates, a liquid crystal layer that is filled between the two substrates and forms a chiral smectic C phase under no electric field, and between the two substrates An optical deflection element comprising: an alignment film that is provided and homeotropically aligns the liquid crystal molecules of the liquid crystal layer; and a pair of electrode plates that generate an electric field with respect to the liquid crystal layer. The liquid crystal layer is provided substantially parallel to the thickness direction of the layer and is opposed to the liquid crystal layer positioned at a substantially central portion. The thickness of the liquid crystal layer is d, and the width of the electrode plate in the thickness direction of the liquid crystal layer is In the case of L, the liquid crystal layer thickness d and the electrode width L are:
L> d
When the electrode width L is larger than the liquid crystal layer thickness d, the ratio of the electrode width L to the electrode spacing increases, so that the electric field on the high voltage side is reduced and the electric field is also generated on the ground side. Even when the effective area of the light deflection element is relatively large, the electric field strength of the horizontal electric field in the liquid crystal layer located at the approximate center of the electrode plate can be made relatively uniform, so that the structure is relatively large with a simple configuration. An optical deflecting element having an area can be realized.
[0103]
According to the invention of claim 2, in the optical deflection element of claim 1, when the distance between the electrode plates is D, the electrode distance D and the electrode width L are:
L ≧ D
When the electrode width L is greater than or equal to the electrode spacing D, the uniformity of the electric field strength is improved, the electric field difference is within 10%, and the horizontal in the liquid crystal layer located at the approximate center of the electrode plate. Since the electric field strength of the electric field becomes substantially uniform, the deflection amount of the optical path can be made substantially constant even when the effective area of the optical deflection element is large.
[0104]
According to a third aspect of the present invention, there is provided the optical deflection device according to the first or second aspect, and voltage applying means for applying a voltage between a pair of electrode plates provided in the optical deflection element. When the electric field strength at which the increasing tendency of the optical path deflection amount is saturated with respect to the increase in the electric field is defined as the saturated electric field Es, the electric field strength in the entire liquid crystal layer of the optical deflection element is equal to or higher than the saturation electric field Es. By setting the output of the voltage application means, even if there is some non-uniformity in the electric field strength of the horizontal electric field in the liquid crystal layer located at the approximate center of the electrode plate, it is uniform regardless of the location in the liquid crystal layer. An optical path shift amount can be obtained.
[0105]
According to a fourth aspect of the present invention, in the optical deflection device according to the third aspect, the optical deflection device is disposed on a light incident side of the optical deflection element, and a light deflection direction of the light deflection element coincides with a polarization direction of incident light. Thus, by further comprising a polarization direction control means for controlling the polarization direction of the incident light, even when the incident light is non-polarized, it is possible to cut a light component that is not subjected to the optical path deflection action due to the tilt of the liquid crystal molecules. Therefore, the optical switching by the optical path deflection can be surely performed.
[0106]
According to a fifth aspect of the present invention, in the optical deflection device according to the third or fourth aspect, the polarization plane rotating means for rotating the polarization plane of the emitted light of the light deflection element substantially at right angles, and the polarization plane rotating means A second optical deflection element that uses the outgoing light after rotation of the polarization plane as incident light, and the optical deflection element and the second optical deflection element have a normal direction of a liquid crystal layer of both the optical deflection elements. By arranging them so that the electric field directions of both optical deflection elements are substantially orthogonal, the optical deflection element has two positions in the vertical direction (Z-axis direction), and the second optical deflection element has a horizontal direction (Y-axis). The light is shifted in two directions in the direction), so that the light as a whole can be shifted to a total of four positions.
[0107]
According to the image display device of the sixth aspect of the present invention, an image display element in which a plurality of pixels capable of controlling light according to image information are two-dimensionally arranged, a light source that illuminates the image display element, and the image display An optical member for observing an image pattern displayed on the element, display drive means formed by a plurality of subfields obtained by temporally dividing the image field, and a light path between the image display element and the optical member is deflected An optical deflection element according to claim 1 or 2, or an optical deflection means which is an optical deflection device according to any one of claims 3 to 5, and a plurality of time fields divided by the optical deflection means. By displaying an image pattern in which the display position is shifted according to the deflection state of the optical path for each subfield, the apparent number of pixels of the image display element is multiplied and displayed. , Using less image display device number of pixels, in apparently high definition it is possible to provide an image display apparatus with high light utilization efficiency. Further, in particular, the optical deflection element which is the optical deflection element according to claim 1 or 2 or the optical deflection device according to any one of claims 3 to 5 is used, and the optical deflection position control is performed by an electrode pair in the optical deflection unit. By performing according to the electric field application direction and electric field strength, an appropriate pixel shift amount is maintained and a good image can be obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an example of the basic configuration of an optical deflection element according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a model of a helical structure change due to an electric field of liquid crystal molecules.
3 is an explanatory view schematically showing the alignment state of the liquid crystal molecules shown in FIG. 1 in order to explain the operation principle of the optical deflection element. FIG.
4A and 4B show a relationship between a liquid crystal director and light deflection, in which FIG. 4A is a cross-sectional structure diagram, and FIG. 4B is an explanatory diagram of an alignment state of the liquid crystal director.
FIG. 5 is a graph showing a relationship between a tilt angle and an optical path shift amount.
6A and 6B show examples of electric field simulation results, where FIG. 6A is a graph showing the relationship between the position between electrodes and the electric field strength, and FIG. 6B is an explanatory diagram showing a simulation example for comparison.
FIG. 7 is a graph showing an example of measurement of the electric field strength dependence of the optical path shift amount of the optical deflection element.
FIG. 8 is a schematic perspective view showing an optical deflection device according to a second embodiment of the present invention together with schematic liquid crystal alignment of an optical deflection element.
FIG. 9 is a schematic side view illustrating a configuration example of an image display device according to a third embodiment of the present invention.
10 is an explanatory diagram illustrating a configuration example of an optical deflection element according to Embodiment 1. FIG.
FIG. 11 is an explanatory diagram illustrating a configuration example of an optical deflection element according to a second embodiment.
[Explanation of symbols]
1,1A Optical deflection element
1B Second optical deflection element
2 Substrate
4 Alignment film
5 Liquid crystal layer
6 Pair of electrode plates
7 Voltage application means
9 Polarization plane rotation means
10 Optical deflection device
41 Image display device
42 Light source
46 Image display element
47 Optical members
50 Light deflection means

Claims (6)

A pair of transparent substrates, a liquid crystal layer filled between both the substrates to form a chiral smectic C phase under no electric field, and liquid crystal molecules of the liquid crystal layer provided between the two substrates are homeotropically aligned. In the optical deflection element including an alignment film and a pair of electrode plates that generate an electric field parallel to the substrate with respect to the liquid crystal layer, the pair of electrode plates are substantially parallel to the thickness direction of the liquid crystal layer. The liquid crystal layer thickness d is set so that the liquid crystal layer is disposed opposite to the liquid crystal layer at a substantially central portion, the thickness of the liquid crystal layer is d, and the width of the electrode plate in the thickness direction of the liquid crystal layer is L. And the electrode width L are in a relationship of L> d. When the interval between the electrode plates is D, the electrode interval D and the electrode width L are:
L ≧ D
The optical deflection element according to claim 1, wherein: The light deflection element according to claim 1 or 2,
Voltage applying means for applying a voltage between a pair of electrode plates provided in the light deflection element,
When the electric field strength at which the increase tendency of the optical path deflection amount is saturated with respect to the increase in the electric field is defined as the saturated electric field Es, the voltage is set so that the electric field strength in the entire liquid crystal layer of the optical deflection element is equal to or higher than the saturation electric field Es. An optical deflection device characterized by setting an output of an applying means. A polarization direction control unit that is disposed on a light incident side of the light deflection element and controls a polarization direction of the incident light so that a light deflection direction by the light deflection element and a polarization direction of the incident light coincide with each other; The optical deflection device according to claim 3. A polarization plane rotating means for rotating the polarization plane of the outgoing light of the light deflection element substantially at right angles;
A second light deflection element that makes the outgoing light after the polarization plane rotation by the polarization plane rotation means the incident light,
The light deflection element and the second light deflection element are arranged so that the normal directions of the liquid crystal layers of both the light deflection elements are substantially coincided and the electric field directions of both the light deflection elements are substantially orthogonal to each other. The optical deflection device according to claim 3 or 4. An image display element in which a plurality of pixels capable of controlling light according to image information are two-dimensionally arranged;
A light source for illuminating the image display element;
An optical member for observing an image pattern displayed on the image display element;
Display driving means for forming an image field by a plurality of subfields divided in time, and
An optical deflecting device that deflects an optical path between the image display element and the optical member, or an optical deflecting device that is an optical deflecting device according to any one of claims 3 to 5,
An image display device comprising:

Images