JP4961152B2 - Optical element, light deflection element, and image display apparatus - Google Patents

Description

  The present invention relates to an optical element that modulates light by applying an electric signal to a plurality of pattern electrodes, an optical deflection element that changes the direction of the light using the optical element, a projection display that uses the optical deflection element, a head-mounted display, etc. The present invention relates to an image display apparatus.

  For example, Patent Document 1 discloses an optical deflection element that deflects light by changing the arrangement of liquid crystal molecules by an electric field generated along the plane of an electrode substrate. This optical deflection element is provided with a plurality of parallel transparent line electrodes only on one substrate surface of a transparent substrate with a liquid crystal layer sandwiched therebetween, and a plurality of resistors for dividing a voltage supplied from a power source outside. Connected to each line electrode, a stepped voltage value is applied to each line electrode, and an electric field along the substrate plane, that is, a horizontal electric field is generated between each line electrode due to a potential difference between the line electrodes. A potential gradient is forcibly created inside the layer so as to obtain a relatively uniform electric field strength over the entire surface of the device.

In order to reduce the light diffraction of this optical deflection element, the optical deflection element disclosed in Patent Document 1 is provided with a filler between a plurality of line electrodes formed on a transparent substrate, and the optical path between the line electrode and the filler The difference is limited to a small size.
Japanese Patent Laid-Open No. 2004-286562

  In order to reduce diffraction caused by the optical path difference caused by the line electrode and the filler, there are methods of reducing the refractive index of the line electrode, reducing the film thickness of the line electrode, or increasing the refractive index of the filler. is there.

  However, as for the film thickness of the line electrode, it is necessary to ensure a certain degree of surface resistivity so as not to cause a problem in generating an electric field to be applied to the liquid crystal. Therefore, the film thickness cannot be extremely reduced. In addition, from the viewpoints of heat resistance to the optical element manufacturing process and durability and light resistance of the manufactured optical element, there are many characteristics required for the filler in addition to the refractive index. For this reason, if the higher refractive index is prioritized, these characteristics are often sacrificed, and when trying to reduce diffraction, the line electrode material, film thickness, filler material, etc. are significantly restricted, Other characteristics of the optical element are deteriorated.

  This invention pays attention to such a problem, and an optical element capable of further reducing the influence of diffraction while leaving the degree of freedom of material selection when forming an optical element, and using the same It is an object of the present invention to provide an optical deflection element and an image display device that change the direction of light.

The optical element of the present invention includes a plurality of electrode forming portions each including a substrate, a refractive index adjusting portion formed on at least one surface of the substrate, and an electrode superimposed on the refractive index adjusting portion, and the plurality of electrodes. an optical element having an electrode non-formation portions to be filled between the forming section, the refractive index of the electrode n1, the refractive index of the electrode non-formation portions n2, the refractive index of the refractive index adjusting unit and n3 when, characterized and Turkey to satisfy n3 <n2 <n1.

The thickness of the electrode d1, when the thickness of the refractive index adjuster has a d 2, an optical path difference caused by the refractive index difference between the refractive index adjuster the electrode non-formation portion (n3-n2) × d2 is ,
0.6 × (n1-n2) × d1 <| (n3-n2) × d2 | <1.4 × (n1-n2) × satisfy d1 score and is desirable.

  The refractive index adjusting unit may be formed by etching the substrate.

  Furthermore, the electrode non-formation part may be formed of an adhesive layer.

  The electrode non-formation part may be formed of a dielectric film.

  The optical deflection element of the present invention has a pair of any one of the optical elements described above, and the chiral smectic C phase is disposed within an interval in which the surfaces on which the line electrodes of the pair of optical elements are formed are opposed to each other at a constant interval. A liquid crystal layer to be formed is provided.

  Another optical deflection element according to the present invention has a pair of optical elements each having a plurality of dielectric films, and the plurality of layers are arranged with the surfaces on which the line electrodes of the pair of optical elements are formed facing each other at regular intervals. Of the above dielectric films, the uppermost dielectric film is used as an alignment film, and a liquid crystal layer for forming a chiral smectic C phase is provided between the alignment films.

  The image display device of the present invention is an image display device having the light deflection element, wherein the image display element in which a plurality of pixels capable of controlling light according to image information is two-dimensionally arranged, and the image display element An illumination optical system for illuminating, the light deflection element, and a projection optical system for projecting image light emitted from the image display element, wherein the light deflection element is between the image display element and the projection optical system. It is characterized by being arranged in.

This invention suppresses diffraction that occurs when light passes through an optical element by reducing the optical path difference between an electrode forming portion having electrodes superimposed on a refractive index adjusting portion formed on a substrate and an electrode non-forming portion. Thus, it is possible to prevent deterioration of optical characteristics.

  Further, the diffraction can be sufficiently suppressed by determining the refractive index and thickness of the electrode non-forming part by the optical path difference caused by the refractive index difference between the refractive index adjusting part and the electrode non-forming part.

  Furthermore, the refractive index adjusting unit can be easily manufactured by forming the refractive index adjusting unit by etching the substrate.

  In addition, by forming the electrode non-forming part with an adhesive layer or dielectric film, it is possible to select the optimal filler material for determining the refractive index of the electrode non-forming part, stabilizing the diffraction suppression effect Can be increased.

  By forming an optical deflection element with this optical element and a liquid crystal layer that forms a chiral smectic C phase, it is possible to suppress diffraction and deflect a stable optical path.

  By using the dielectric film of the optical element as the alignment film of the light deflecting element, it is possible to ensure good alignment of the liquid crystal and to deflect light stably.

  In addition, this light variable deflection element is used in an image display device, and image light emitted from an image display element in which a plurality of pixels capable of controlling light according to image information is two-dimensionally arranged is deflected and projected. Therefore, even if an image display element having a small number of pixels is used, a high-definition and stable performance image can be displayed.

  1A and 1B show a configuration of an optical element according to the present invention, in which FIG. 1A is a front view, FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A, and FIG. The optical element 1 includes a substrate 2 formed of a material that is less absorbed or transparent when light passes through the substance, and a low refractive index layer 3 that is a refractive index adjusting unit that adjusts a plurality of refractive indexes. And the line electrode 4, the resistance film 5, the adhesive layer 6, and the dielectric substrate 7. The plurality of low-refractive index layers 3 are made of a material having a small degree of absorption when light passes through a substance and is formed in parallel with one surface of the substrate 2. Although the case where the low refractive index layer 3 is formed on one surface of the substrate 2 is shown, it may be formed on both surfaces of the substrate 2. The plurality of line electrodes 4 are made of a transparent conductive film, are formed so as to overlap each low refractive index layer 3, and the substrate 2 is divided into a plurality of sections by each low refractive index layer 3 and the line electrode 4. A portion that is latticed by the low refractive index layer 3 and the line electrode 4 is referred to as an electrode forming portion, and a portion that is formed between the line electrodes 4 is referred to as an electrode non-forming portion. At the ends of the line electrodes 4 at both ends, there are connecting portions 9 to the voltage applying means 8. The resistance film 5 is disposed in a band shape along the end surface of each line electrode 4 and is formed by being laminated. The surface of the substrate 2 on which the line electrode 4 is provided is made of a material that is less absorbed or transparent when light passes through the substance through an adhesive layer 6 such as a photocurable resin or a thermosetting resin. The formed dielectric substrate 7 is adhered. The adhesive layer 6 for adhering the dielectric substrate 7 is also filled between each low refractive index layer 3 and the line electrode 4. In addition, although the adhesive agent of the adhesive layer 6 is comprised as a filler, what is necessary is just the member which permeate | transmits light not only an adhesive agent.

  When a voltage is applied from the voltage applying means 8 between the line electrodes 4 at both ends of the optical element 1, the voltage attenuation occurs between the adjacent line electrodes 4 due to the resistance of the resistance film 5. Different potentials are applied, a potential gradient is formed in a direction orthogonal to the longitudinal direction of the line electrode 4, and a horizontal electric field along the surface of the substrate 2 is generated in the direction in which the potential changes. If the polarity of the voltage applied to the line electrodes 4 at both ends is reversed, the direction of the electric field can be reversed. Therefore, when an AC power supply is used as the voltage application means 8, the direction of the electric field can be switched periodically or at an arbitrary timing.

  Thus, when a voltage is applied between the line electrodes 4 at both ends of the optical element 1 to generate an electric field, different potentials are applied to each line electrode 4 in stages, thereby generating a potential gradient. 4 has a constant potential, and the potential between the line electrodes 4 is floating. Therefore, the direction and magnitude of the electric field are locally modulated according to the arrangement of the line electrodes 4. Has been. The influence of such local modulation of the electric field can be reduced through the dielectric substrate 7.

The line electrode 4 of the optical element 1 includes tin-doped indium oxide (ITO), indium oxide (In ₂ O ₃ ), indium oxide / zinc oxide (IZO), tin oxide (SnO ₂ ), zinc oxide (ZnO), aluminum Added zinc oxide (ZnO: Sb), antimony-added tin oxide (ATO), or the like is used. As a material for forming the line electrode 4, it is common to use a transparent oxide having a high transmittance to visible light. Indium oxide has a refractive index of about 1.8 to 2.0 with respect to light having a wavelength of 500 to 550 nm. Zinc oxide has a relatively high refractive index of about 2.1 and tin oxide has a refractive index of about 1.9, and all of the materials doped with these materials have a relatively high refractive index. The refractive index of the adhesive layer 6 such as a photocurable resin or a thermosetting resin filled between the line electrodes 4 is about 1.5, and the refractive index is 1.6 even with a high refractive index material.

When the refractive index of the line electrode 4 is n1 and the refractive index of the adhesive layer 6 is n2, n1> n2, and when there is no low refractive index layer 3, the refractive index n1 of the line electrode 4 and the refractive index of the adhesive layer 6 Due to the difference in the rate n2, diffraction occurs in the light that is incident on and transmitted through the optical element 1. Therefore, a low refractive index layer 3 having a refractive index n3 smaller than any of the refractive index n1 of the line electrode 4 and the refractive index n2 of the adhesive layer 6 is provided between the substrate 2 and the line electrode 4. The influence of the difference between the refractive index n1 of the first layer and the refractive index n2 of the adhesive layer 6 is reduced. That is, since a difference in refractive index occurs between the electrode forming portion and the electrode non-forming portion, the refractive index is controlled by the low refractive index layer 3, and the influence of the difference in refractive index between the electrode forming portion and the electrode non-forming portion is affected. Make it smaller.

That is, as shown in FIG. 2, when the thickness of the line electrode 4 is d1 and the thickness of the low refractive index layer 3 is d2, the light and thickness (d1 + d2) passing through the low refractive index layer 3 and the line electrode 4 The optical path difference of light passing through the adhesive layer 6 is
{(N3 * d2 + n1 * d1) -n2 * (d1 + d2)}
= {(N1-n2) * d1 + (n3-n2) * d2}
Since n2> n3, the entire optical path difference can be reduced, and diffraction can be suppressed.

Since the diffraction intensity is proportional to sin (optical path difference / wavelength × π), diffraction can be sufficiently suppressed when the optical path difference is sufficiently smaller than the wavelength, for example, 1% or less. For example, when the refractive index n1 of the line electrode 4 for light having a wavelength of 546 nm is 2.0, the thickness d1 is 30 nm, and the refractive index n2 of the adhesive layer 6 is 1.56, the optical path difference is 5.46 nm or less, which is 1% of the wavelength 546 nm. Therefore, since (n1−n2) × d1 = 13.2 nm, the optical path difference (n3−n2) × d2 caused by the difference in refractive index between the low refractive index layer 3 and the adhesive layer 6 is set to −18.66 nm ≦ (n3− n2) × d2 ≦ −7.74 nm (1)
It should be satisfied. This condition is
0.6 * (n1-n2) * d1 <| (n3-n2) * d2 | <1.4 * (n1-n2) * d1
It corresponds to.
Thus, when the absolute value of the optical path difference between the light passing through the low refractive index layer 3 and the line electrode 4 and the light passing through the adhesive layer 6 is 1% or less of the transmitted light wavelength, the diffraction reduction effect can be visually recognized. Degradation of optical characteristics can be sufficiently suppressed.

  In the above description, the case where the line electrode 4 is formed on the surface of the low refractive index layer 3 after the low refractive index layer 3 is formed on the substrate 2 has been described. However, when the refractive index of the substrate 2 is smaller than that of the adhesive layer 6, a conductive film is formed on the surface of the substrate 2 and patterned into a line shape as shown in FIG. The substrate 2 may also be etched to the depth of 2 to form the line electrode 4 and the low refractive index layer 3, and a part of the substrate 2 may be used as the low refractive index layer 3.

  An optical deflection element using the optical element 1 will be described. 4A and 4B show a configuration of an optical deflecting element 10 using the optical element 1, wherein FIG. 4A is a front view, FIG. 4B is a cross-sectional view taken along line AA in FIG. 4A, and FIG. It is sectional drawing. The optical deflection element 10 includes a pair of optical elements 1, four spacers 11, an alignment film 12, and a liquid crystal layer 13. An alignment film 12 is formed on the surface of the dielectric substrate 7 of each optical element 1, and the pair of substrates 2 of the optical element 1 are bonded to each other by a spacer 11 with the alignment film 12 side inside. Yes. This pair of optical elements 1 is configured with the line electrodes 4 of each substrate 2 shifted by a half pitch in order to improve the uniformity of the generated electric field. A liquid crystal layer 13 capable of forming a chiral smectic C phase is provided between the alignment films 12 arranged to face each other. The alignment film 12 is a vertical alignment film for aligning liquid crystal molecules in a direction perpendicular to the alignment film 12, and the layer normal direction of the layer structure of the liquid crystal molecules forming the chiral smectic C phase is substantially the plane of the substrate 2. It is configured to be vertical. As the alignment film 12, a silane coupling agent, a commercially available vertical alignment agent for liquid crystal, or the like can be used.

  Here, the liquid crystal layer 13 will be described in detail. A smectic liquid crystal is a liquid crystal layer in which major axis directions of liquid crystal molecules are arranged in layers. With respect to such a liquid crystal, a liquid crystal in which the normal direction of the layer (layer normal direction) and the major axis direction of the liquid crystal molecules coincide with each other is called a smectic A phase, and a liquid crystal that does not coincide with the normal direction is called a smectic C phase. . A ferroelectric liquid crystal composed of a smectic C phase generally has a so-called spiral structure in which the direction of the liquid crystal director is spirally rotated for each layer in a state where an external electric field does not work, and is called a chiral smectic C phase. Further, the chiral smectic C phase antiferroelectric liquid crystal is oriented in the direction in which the liquid crystal directors face each other. Since the liquid crystal composed of these chiral smectic C phases has an asymmetric carbon in the molecular structure and is spontaneously polarized by this, the liquid crystal molecules are rearranged in a direction determined by the spontaneous polarization Ps and the external electric field E. Optical properties are controlled.

  Here, a case where a ferroelectric liquid crystal is used as the liquid crystal layer 13 of the light deflection element 10 will be described. However, an antiferroelectric liquid crystal can also be used in the same manner. The structure of a ferroelectric liquid crystal composed of a 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 the skeleton responsible for molecular rotation, the bonding portion, and the chiral portion with 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 part that bonds the chiral part and a rigid skeleton such as a biphenyl structure. The ferroelectric liquid crystal layer 13 composed of a chiral smectic C phase has a rotational axis of molecular helix rotation perpendicular to the surface of the substrate 2 by the alignment film 12 and has a so-called homeotropic alignment.

  When a voltage is applied between the line electrodes 4 at both ends of the optical element 1 constituting the optical deflecting element 10, a current flows through the resistance film 5, and the voltage value is attenuated between the adjacent line electrodes 4 by the resistance film 5. A potential gradient is generated between the line electrodes 4. Due to this potential gradient, a horizontal electric field along the surface is obtained in the vicinity of the surface of the substrate 2 on which the line electrode 4 is formed. The horizontal electric field is modulated in the direction and magnitude of the electric field corresponding to the arrangement of each line electrode 4, but the influence of the modulation is reduced by the dielectric substrate 7, and the liquid crystal layer 13 is substantially parallel to the surface of the substrate 2. A uniform horizontal electric field can be obtained. That is, since the liquid crystal layer 13 is sandwiched through the dielectric substrate 7, a uniform horizontal electric field that is substantially parallel to the substrate 2 can be obtained. The dielectric substrate 7 may be made of a transparent material. For example, glass, sapphire, or ceramics can be used. By switching the polarity of the voltage applied between the line electrodes 4 at both ends of the optical element 1, a reverse potential gradient can be given between the line electrodes 4, and the direction of the horizontal electric field inside the liquid crystal layer 13 can be changed. Can be switched. When the direction of the horizontal electric field is switched in this way, the inclination direction of the average optical axis of the liquid crystal layer 13 changes, and the incident light linearly polarized in the direction parallel to the line electrode 4 has the thickness of the liquid crystal layer 13 and As shown in FIG. 4B, the incident light takes an optical path between the first outgoing light and the second outgoing light as a result of being deflected by receiving an optical path shift corresponding to the ordinary light / abnormal light refractive index of the liquid crystal molecules. When the light is deflected in this way, the number of line electrodes 4, the line width, the line interval, the potential difference between the line electrodes 4, etc. may be appropriately set based on the desired optical path size, optical path deflection amount, liquid crystal material, and the like.

  In the above description, the case where the dielectric substrate 7 of the optical element 1 is bonded to the substrate 2 with the adhesive layer 6 and the surface of the dielectric substrate 7 is not uneven has been described. The body layer may be formed directly.

  For example, in the optical deflection element 10 a shown in the cross-sectional view of FIG. 5, a plurality of line electrodes 4 are formed in parallel on one surface of the substrate 2, and a resistance film 5 is stacked on the end portion. A low refractive index layer 3 is laminated. Two dielectric layers 14 and 15 are formed on the surface having the low refractive index layer 3, and the surface dielectric layer 15 is used as an alignment film. By using the dielectric layer 15 in contact with the liquid crystal layer 13 as an alignment film, good alignment of the liquid crystal can be secured. Here, the number of dielectric layers may be one to provide the function of an alignment film. Further, since the optical element 1a does not need to be bonded to the dielectric substrate 7 via the adhesive layer 6, it is manufactured in comparison with the optical deflection element 1 having a structure in which the dielectric substrate 7 is bonded via the adhesive layer 6. There is an advantage that the process is simple and there is no deterioration of wavefront aberration due to uneven thickness of the adhesive layer 6 or warping of the dielectric substrate 7, and the number of interfaces can be reduced, so there is no extra scattering. As a result, the contrast is improved.

  The two dielectric layers 14 and 15 of the optical element 1a are formed by vacuum film formation such as sputtering, vapor deposition, or ion plating, or by coating, dipping, or sol-gel. When the two dielectric films 14 and 15 are formed as described above, depending on the width and pitch of the line electrode 4, in many cases, as shown in FIG. It appears on the surfaces of the films 14 and 15 and is in a state in which line-shaped convex portions exist. Therefore, not only the refractive index difference between the line electrode 4 and the dielectric layer 14 but also the refractive index difference between the first dielectric layer 14 and the second dielectric layer 15, and the second dielectric layer 15 and the liquid crystal layer 13. Diffraction also occurs due to the difference in refractive index. In order to suppress the occurrence of this diffraction, the refractive index and thickness of the low refractive index layer 3 are optimized to suppress the optical path difference of light passing through the electrode forming portion and the electrode non-forming portion as small as possible.

For example, as shown in FIG. 6A, the line electrode 4 is formed on the substrate 2, the dielectric layer 14 is formed with a SiO ₂ layer without providing the low refractive index layer 3, and the alignment film is formed on the surface thereof. It is assumed that the dielectric layer 15 is formed. The refractive index n1 of the line electrode 4 is 2.0, the thickness is 30 nm, the refractive index n4 of the dielectric layer 14 made of SiO ₂ is 1.46, the refractive index n5 of the dielectric layer 15 is 1.41, and the refractive index of the liquid crystal layer 13 Let n6 be 1.54. When the dielectric layer 14 was deposited from the surface of the substrate 2 with a thickness d4 = 100 nm, the thickness d41 of the dielectric layer 14 on the line electrode 4 was slightly smaller and became 97 nm. When the dielectric layer 15 is formed on the surface of the dielectric layer 14 with a thickness d5 = 50 nm, the thickness d51 of the dielectric layer 15 on the line electrode 4 becomes 47 nm, and the height of the protruding portion protruding to the liquid crystal layer 13 is increased. The d6 became 24 nm. The optical path length of the electrode forming part calculated based on the measured thickness value and each refractive index is 253.46 nm, the optical path length of the electrode non-forming part is 253.46 nm, and the electrode forming part and the electrode non-forming part The optical path difference of the light passing through was 14.43 nm. This optical path difference is greatly influenced by the refractive index difference between the line electrode 4 and the dielectric layer 14 made of SiO ₂ . Therefore, as shown in FIG. 6B, even if the dielectric layer 14 having the same refractive index as that of the line electrode 4 is used instead of the dielectric layer 14, the refractive indexes of the dielectric layer 14 and the dielectric layer 15 are used. Since the difference becomes large, the optical path difference of the light passing through the electrode forming part and the electrode non-forming part is 12.81 nm, and no significant improvement is observed.

On the other hand, as shown in FIG. 6C, a low refractive index layer 3 is formed of a MgF ₂ film having a refractive index n3 of 1.38 with a thickness d2 of 100 nm, and a dielectric layer 14 is formed from the surface of the substrate 2. When the film was formed with a thickness d4 = 100 nm, the thickness d41 of the dielectric layer 14 on the line electrode 4 was 90 nm. When the dielectric layer 15 is formed on the surface of the dielectric layer 14 with a thickness d5 = 50 nm, the thickness d51 of the dielectric layer 15 on the line electrode 4 becomes 40 nm, and the height of the protruding portion protruding to the liquid crystal layer 13 is increased. The d6 became 110 nm. The optical path length of the electrode forming part calculated based on the measured thickness value and each refractive index is 385.8 nm, the optical path length of the electrode non-forming part is 385.9 nm, and the electrode forming part and the electrode non-forming part The optical path difference of the light passing through was 0.1 nm, and a sufficiently small optical path difference with respect to the wavelength of 546 nm corresponding to green could be obtained. Therefore, the low refractive index layer 3 can be formed by patterning a film such as SiO ₂ having a refractive index of 1.46, MaF ₂ having a refractive index of 1.38, or Na ₃ AiF ₆ having a refractive index of 1.35 in a line shape. By selecting the material of the rate layer 3, it can be controlled to a desired thickness, and a high diffraction suppression effect can be obtained. Note that either the low refractive index layer 3 or the line electrode 4 may be formed on the substrate 2 first.

Further, when there are N dielectric layers, the optical path difference X of the light passing through the electrode forming part and the electrode non-forming part is
X = n1 * d1 + n3 * d2 + Σ _{i = 1, N} {ni * (di1-di)}-n6 * d6
It can be expressed as Here, ni and di indicate the refractive index and thickness of the N dielectric layer, di1 indicates the thickness of the N dielectric layer on the line electrode 4, and the thickness d6 protrudes into the liquid crystal layer 13. It is the height of the convex part. Diffraction is suppressed by selecting the refractive index and thickness of the low refractive index layer 3 and the refractive index and thickness of the dielectric layer so that the optical path difference X is, for example, 5.46 nm or less which is 1% of the wavelength of 546 nm. can do.

  Next, an image display apparatus using the light deflection element 10 or the light deflection element 10a will be described. As shown in the configuration diagram of FIG. 7, the optical system of the image display device 20 includes a light source 21, a diffusion plate 22, a condenser lens 23, and an image display element 24 arranged along the optical path of light emitted from the light source 21. The light deflection means 25 having the light deflection element 10 or the light deflection element 10a and the projection lens 26 are arranged in this order. The drive unit includes a light source drive control unit 27 that drives the light source 21, a display drive control unit 28 that drives the image display element 24, a light deflection drive control unit 29 that drives the light deflection unit 25, and a main control unit 30.

  As long as the light source 21 can turn on / off white light or an arbitrary color light at high speed, any type or type of light source can be used. For example, an LED lamp, a laser light source, a white lamp light source, or the like arranged in a two-dimensional array and combined with a shutter that operates at high speed is used. The image display element 24 spatially modulates incident uniform illumination light based on image information for each of a plurality of image subfields obtained by further subdividing the image field in time, and emits the image light as image light. Yes, a transmissive liquid crystal light valve, a reflective liquid crystal light valve, a DMD element, or the like can be used. The light deflecting means 25 deflects the optical path of the image light emitted from the image display element 24 for each image subfield and emits it as deflected image light. The light deflecting unit 24 can display an image pattern in which the image display position projected on the screen 31 is shifted according to the deflection amount of the optical path for each image subfield. An image can be displayed as the actual number of pixels multiplied.

  When an image is projected onto the screen 31 by the image display device 20, the light emitted from the light source 21 controlled by the light source drive control unit 27 becomes illumination light that is made uniform by the diffusion plate 22. The image display element 24 composed of, for example, a transmissive liquid crystal light valve controlled by a display drive control unit 28 that operates in synchronization with the light source drive control unit 27 is critically illuminated. The image display element 24 spatially modulates the incident illumination light and enters the light deflecting means 25 as image light. The light deflecting means 25 shifts the incident image light by an arbitrary distance in the pixel arrangement direction and projects a projection lens. 26 is incident. The projection lens 26 enlarges the incident light and projects it onto the screen 31. By using the light deflecting element 10 having little influence of diffraction in this way, a high-contrast image with high contrast and sharpness can be projected onto the screen 31.

  The amount of shift (deflection) of the optical path of the deflected image light is desirably 1 / integer of the pixel pitch. That is, when the pixel multiplication is performed twice in the pixel arrangement direction, the shift amount of the optical path of the deflected image light is ½ of the pixel pitch, and the pixel multiplication is three times in the arrangement direction. When performing, it is desirable to set to 1/3 of the pixel pitch. Further, when the optical path shift amount of the deflected image light is larger than the pixel pitch due to the configuration of the light deflecting means 25, the optical path shift amount is set to a distance of (integer multiple + 1 / integer) of the pixel pitch. You may do it.

  Using this light deflecting means 25 in two dimensions vertically and horizontally in the pixel array direction, for example, by using two light deflecting elements 10 that perform image multiplication of twice, an effect of four times the apparent pixel can be obtained and used. A high-definition image higher than the resolution of the transmissive liquid crystal light valve can be displayed.

  The image display apparatus shown in FIG. 7 has been described with respect to the case where a single color image is displayed using the image display element 24 formed of a single-plate transmissive liquid crystal light valve and the single color light source 21, but the three primary color light sources 21 and Using the three image display elements 24, it is also possible to display a full-color image by mixing three primary color images. A full-color image can also be displayed by a field sequential method in which the single-panel image display element 24 is illuminated with the three primary colors in time sequence. In this case, the light paths from the three color light sources may be mixed and illuminated by a cross prism, or time-sequential three primary color lights may be generated by a combination of a white lamp light source and a rotating color filter.

A glass plate having a size of 70 mm × 50 mm and a thickness of 1 mm was used as the substrate 2, SiO ₂ was sputtered to a thickness of 120 nm, and a 30 nm ITO film was sputtered thereon. The refractive index of SiO ₂ is 1.46 at a wavelength of 546 nm, and the refractive index of the ITO film is 2.00. Next, a line pattern is formed by applying, exposing, and developing a photoresist, and etching is performed to form 400 low-refractive index layers 3 of SiO ₂ and ITO line electrodes 4 each having a width of 10 μm and a pitch of 100 μm. The connection part was formed in the end of the line electrode 4 of both ends. Next, a Cr—SiO resistance film 5 was formed by a sputtering method in a region where the line electrodes 4 were electrically connected in series. The thickness of the resistive film 5 was 100 nm, and the surface resistivity was 4 × 10 ⁷ Ω / □.

  Next, a cover glass having a thickness of 150 μm was attached to the entire surface with an optical UV adhesive having a thickness of 10 μm in an area of 50 mm × 50 mm excluding the power connection portion. The refractive index of this adhesive is 1.56. Next, the surface of the cover glass was treated with a vertical alignment agent, and then two substrates 2 were bonded with an adhesive mixed with a spacer having a particle diameter of 50 μm. Next, a ferroelectric liquid crystal (CS1029 manufactured by Chisso) was injected between the two substrates 2 to form the light deflection element 10. As a result of applying an AC voltage of ± 2 kV and 60 Hz to the line electrodes 4 at both ends and confirming the optical path shift, measurement was performed at each measurement point over the entire effective area, and an optical path shift amount of 5 μm on average was obtained. The optical path difference at this time was 1.2 nm, and | (n3−n2) × d2 | ≈0.9 × (n1−n2) × d1.

  This light deflecting element 10 is used for the light deflecting means 25 of the image display device 20, and the light deflecting element 10 is arranged in the direction in which the line electrode 4 is vertical, and the image display element 24 makes the right half black and the left half A white image was displayed. As a result of checking whether black floating occurs near the displayed black-white boundary, that is, whether the luminance increases in the black area, the luminance in the black area near the white-black boundary is 100% of the luminance of white. It was 3.58%. When a glass plate having the same optical path length as that of the optical deflection element 10 is placed in place of the optical deflection element 10, the luminance in the black region near the boundary between white and black is 3.59%, and the optical deflection element 10 is used. The luminance was within the range of measurement error, and no increase in luminance due to diffraction could be observed, and no black float due to diffraction was observed.

Four types of optical deflection elements 10 were produced in the same manner as in Example 1 except that the thickness of SiO ₂ was changed to 40 nm, 60 nm, 80 nm, and 100 nm. When the luminance of black was measured in the same manner as in Example 1, the black float decreased as the SiO ₂ film thickness increased. When the film thickness of SiO ₂ was 80 nm, the black float due to diffraction was about 0.3%, which was found to be less than or equal to one gradation in 256 gradation display. Visually, the influence of diffraction was not visually recognized in the optical deflector 10 having a SiO ₂ film thickness ₂ of 80 nm or more. When the film thickness _{2 of} SiO ₂ is 80 nm, the optical path difference is 5.2 nm, and it was shown that the influence of diffraction can be sufficiently reduced if the optical path difference is 1% or less of the wavelength 546 nm. At this time, it was | (n3−n2) × d2 | ≈0.6 × (n1−n2) × d1.

ITO was sputtered on a glass substrate 2 having the same shape as in Example 1 to a thickness of 30 nm. After coating / exposure / development of the photoresist, the ITO was dry etched into a line shape. At that time, the substrate 2 itself was etched by a depth of 200 nm following ITO, so that a configuration similar to that shown in FIG. 3 was obtained. Thereafter, an optical deflection element 10 was produced in the same manner as in Example 1. The refractive index of the glass as the substrate 2 is 1.52 at a wavelength of 546 nm. At this time, the optical path difference is 5.2 nm. When the black luminance was measured in the same manner as in Example 1, the black luminance was 3.88%, which was the same as that in Example 2 when the SiO ₂ film thickness was 80 nm. I couldn't see it.

A CrSiO resistance film 5 was formed on a glass substrate 2 having the same shape as in Example 1 by sputtering. The thickness of the resistive film 5 was 100 nm, and the surface resistivity was 4 × 10 ⁷ Ω / □. Next, MgF ₂ was sputtered to a thickness of 100 nm, and then a 30 nm ITO film was sputtered thereon. The refractive index of MgF ₂ is 1.38 and that of ITO is 2.00. After applying, exposing and developing the photoresist, both ITO and MgF ₂ were dry etched to form a line-shaped MgF ₂ low refractive index layer 3 and a line electrode 4. Here, the resistance film 5 is formed in a region where the line electrodes 4 are electrically connected in series. On the surface on which the line electrode 4 and the low refractive index layer 3 were formed, SiO ₂ was sputtered about 100 nm so as to cover them, and an alignment film having a thickness of about 50 nm was formed on the surface. The two substrates 2 were bonded with spacers 11 so that the surfaces face each other, so that the effective area of the element was 40 mm × 40 mm or more. A ferroelectric liquid crystal (CS1029 manufactured by Chisso) was injected between the two substrates 2 to form the light deflection element 10. As a result of applying an AC voltage of ± 2 kV and 60 Hz to the line electrodes 4 at both ends of each substrate 2 and confirming the optical path shift, it was confirmed that an average shift amount of 5 μm was obtained at each measurement point over the entire effective area. did it.

As a result of incorporating the light deflection element 10 into the image display device 20 and projecting a black and white image, an increase in luminance due to diffraction cannot be observed, and no black float due to diffraction was observed. The thickness of each layer at this time is as shown in FIG. 6C, and the optical path difference is 0.1.
nm.

It is a block diagram of the optical element of this invention. It is a fragmentary sectional view which shows the structure of an electrode formation part and an electrode non-formation part. It is a block diagram of the low refractive index layer formed by etching a board | substrate. It is a block diagram of an optical deflection element. It is sectional drawing which shows the structure of a 2nd light deflection | deviation element. It is a schematic diagram which shows the optical path difference of the electrode formation part in a 2nd optical deflection | deviation element, and an electrode non-formation part. It is a block diagram of the image display apparatus of this invention.

Explanation of symbols

1; optical element, 2; substrate, 3; low refractive index layer, 4; line electrode, 5;
6; adhesive layer, 7; dielectric substrate, 8; voltage applying means, 9; connection portion, 10;
11; spacer, 12; alignment film, 13; liquid crystal layer, 14; dielectric layer, 15; dielectric layer,
20; Image display device, 21; Light source, 22; Diffuser plate, 23; Condenser lens,
24; Image display element; 25; Light deflecting means; 26; Projection lens;
27; light source drive control unit; 28; display drive control unit; 29; light deflection drive control unit;
30: Main control unit, 31: Screen.

Claims (9)

A plurality of electrode forming portions each having a substrate, a refractive index adjusting portion formed on at least one surface of the substrate, and an electrode superimposed on the refractive index adjusting portion, and a space between the plurality of electrode forming portions are filled. An optical element having an electrode non-forming portion,
When the refractive index of the electrode n1, the refractive index of the electrode non-formation portions n2, the refractive index of the refractive index adjuster was n3, wherein the optical element and Turkey to satisfy n3 <n2 <n1 . The thickness of the electrode d1, when the thickness of the refractive index adjuster has a d 2, an optical path difference caused by the refractive index difference between the refractive index adjuster the electrode non-formation portion (n3-n2) × d2 is ,
0.6 × (n1-n2) × d1 <| (n3-n2) × d2 | <1.4 × (n1-n2) optical element 請 Motomeko 1, wherein satisfying the × d1.   The optical element according to claim 1, wherein the refractive index adjusting unit is formed by etching the substrate.   The optical element according to claim 1, wherein the electrode non-forming portion is formed of an adhesive layer.   The optical element according to claim 1, wherein the electrode non-forming portion is formed of a dielectric film.   The optical element according to claim 5, wherein the dielectric film is formed in a plurality of layers.   A pair of optical elements according to any one of claims 1 to 6, wherein the pair of optical elements has a chiral smectic C phase within an interval in which the surfaces on which the line electrodes are formed are arranged to face each other at a constant interval. An optical deflecting element provided with a liquid crystal layer for forming.   7. A pair of optical elements according to claim 6, wherein surfaces of the pair of optical elements on which the line electrodes are formed are arranged to face each other at a constant interval, and the uppermost dielectric layer of the plurality of dielectric films is disposed. An optical deflecting element comprising a liquid crystal layer that forms a chiral smectic C phase between dielectric films having an alignment film as an alignment film and an alignment film. An image display device comprising the light deflection element according to claim 7 or 8,
An image display element in which a plurality of pixels that can control light according to image information are arranged two-dimensionally, an illumination optical system that illuminates the image display element, the light deflection element, and the image display element An image display apparatus comprising: a projection optical system that projects image light, wherein the light deflection element is disposed between the image display element and the projection optical system.

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