JP4282263B2 - Optical path switching device and image display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical deflection element that changes the direction of light according to an electric signal, an optical path switching device, and an image display apparatus using the optical deflection element or optical path switching device, and can be applied to electronic display devices such as projection displays and head mounted displays. The present invention relates to an optical path switching device and an image display device.
[0002]
[Prior art]
The optical path of light is deflected by an external signal such as an electrical signal, that is, the optical axis of the outgoing light is shifted in parallel to the incident light, rotated at a certain angle, or a combination of both to switch the optical path. As an optical deflection element capable of₂PO_Four(KDP), NH_FourH₂PO_Four(ADP), LiNbO_Three, LiTaO_Three, GaAs, CdTe, and other materials having a large primary electro-optic effect (Pockels effect), KTN, SrTiO_Three, CS₂, Nitrobenzene and other electro-optic devices using large secondary electro-optic effects, 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.
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.
[0003]
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. In detail, 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 a 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, matrix drive is possible between the transparent substrates, and a light beam shifter sandwiching a liquid crystal layer that shifts the incident light beam by a half cell is provided. There has been proposed a light beam shifter in which multiple stages are shifted by half a cell.
However, in the above-mentioned 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.
[0004]
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.
However, in the example of the above-mentioned 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.
[0005]
Next, several techniques that have been conventionally proposed for the pixel shift element will be described. The pixel shift element here is 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 pattern displayed on the image display element And an optical deflector for deflecting the optical path between the image display element and the optical member for each of a plurality of subfields obtained by temporally dividing the image field. It means an optical deflecting means in an image display device that displays an image pattern in which the display position is shifted in accordance with the deflection of the optical path for each field, thereby doubling the apparent number of pixels of the image display element.
[0006]
For example, as shown in Japanese Patent No. 2939826, in a projection display apparatus that enlarges and projects an image displayed on a display element into a screen shape 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 the projected image comprising at least one optical element capable of rotating the polarization direction of the light, at least one transparent element having a birefringence effect, and effectively reducing the aperture ratio of the display element And a projection display device provided with means for discretely projecting the projection area of each pixel of the display element on the screen.
[0007]
In the example of the publication, a projected image 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. The pixel shift is performed by the shift means (pixel shift means). However, since the optical rotation element and the birefringence element are used in combination, the problem is that the light loss is large and the pixel shift amount varies depending on the wavelength of light. Due to the low resolution, optical mismatch between optical rotator and birefringent element, optical noise such as ghost due to leaked light is likely to occur at positions outside the pixel shift where no image is originally formed. It is mentioned that the cost for this is large. In particular, the KH as described above for the birefringent element₂PO_Four(DKP), NH_FourH₂PO_Four(ADP), LiNbO_ThreeLiTaO_ThreeThis is remarkable when a material having a large primary electro-optic effect (Pockels effect) such as GaAs, CdTe, or the like is used.
[0008]
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 by the control circuit to the image selection 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.
[0009]
However, in the example of this publication, a pixel shift method is described 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 system and durability of the movable part are required, and vibration and sound become a problem.
[0010]
Further, according to Japanese Patent Laid-Open No. 6-324320, a plurality of pixels arranged in the vertical direction and the horizontal direction are provided 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. An optical member that changes an optical path for each field is disposed between an image display device that displays an image by emitting light according to a display pixel pattern and an observer or a screen, Every time, a display pixel pattern in which the display position is shifted in accordance with the change in the optical path is displayed on the image display device. Here, the optical path is changed by causing 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.
[0011]
In the example of this publication, as a means for changing the optical path, 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. In addition to the method of combining refracting elements, a method of switching optical paths by displacing (translating or tilting) optical elements such as lenses, reflectors, and birefringent plates by means of voice coils, piezoelectric elements, etc. has been proposed. In this method, since the optical element is driven, the configuration becomes complicated and the cost increases.
[0012]
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 less susceptible to 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 them and deflect the optical axis of the light beam.
[0013]
In the example of this publication, a method is proposed in which a light-transmitting piezoelectric element is sandwiched between transparent electrodes, and the thickness is changed by applying a voltage to shift the optical path. However, a relatively large transparent piezoelectric element is required. There is a problem similar to the case of the above-mentioned JP-A-6-324320.
[0014]
In order to improve the high speed, which was insufficient with the above-described conventional technology, and to simplify the structure and reduce the cost, the present inventors previously made a pair of transparent substrates and a homogeneous filled between these substrates. The liquid crystal comprising an aligned chiral smectic C phase is provided with an electric field applying means using an electrode pair formed between the one-handed substrate and the liquid crystal, and the incident direction of light is different from the normal direction of the substrate surface An optical deflecting element set in a direction, a pair of transparent substrates, a liquid crystal composed of a chiral smectic C phase filled between the substrates, and at least one set of electric field applying means. The present invention provides an optical deflection element in which the both substrate surfaces sandwiched are inclined to face each other in accordance with the optical deflection direction, and an optical path switching device including two sets of the above optical deflection elements at a predetermined distance in the optical traveling direction.
[0015]
In the optical deflecting element and the optical path switching device submitted by the present inventors, a chiral smectic C phase liquid crystal is used as the liquid crystal material, so that switching can be performed at a higher speed than in the prior art. Therefore, polarization conversion is required, which increases the size and cost of elements and devices. Further, the chiral smectic C phase is difficult to be uniformly oriented, particularly when the substrate spacing is non-parallel. Furthermore, although the chiral smectic C-phase liquid crystal operates at high speed, its operation speed is sub-millisecond (several hundred μs), which may not be sufficient.
[0016]
[Problems to be solved by the invention]
  The present invention solves the above-mentioned problems and achieves high speed.LightRoad switchingapparatusAndLightRoad switchingapparatusAn object of the present invention is to provide an image display device using the. More specifically,lightProvided is an optical path switching device capable of shifting a path in two orthogonal directions.AndUsing an image display element with a small number of pixels, it is possible to provide an image display device that apparently has high definition and high light utilization efficiency.When,Is the purpose.
[0017]
[Means for Solving the Problems]
  The invention of claim 1An optical path switching device that switches an optical path of incident light according to an electrical signal, the optical path switching device changing an angle of deflection of outgoing light with respect to incident light in accordance with a change in refractive index of a liquid crystal / polymer composite The first optical path switching device and the second optical path switching device each having two, each of the optical deflection element provided in each of the optical path switching device,A liquid crystal / polymer composite in which a liquid crystal material is dispersed and held in a polymer matrix; and a light transmissive electrode for applying a voltage for changing the refractive index of the liquid crystal / polymer composite. An optical deflection element in which the deflection angle of outgoing light with respect to incident light changes in accordance with the change in the refractive index of the polymer composite, wherein the liquid crystal / polymer composite is one of two surfaces facing each other on the optical path. And the electrode is disposed on the surfaces of the two opposing surfaces.Each of the optical path switching devices is configured so that the light deflected by the first light deflecting element is parallel to the incident light by the second light deflecting element installed at a constant interval. Element and the second light deflection element are arranged so that the maximum inclination direction of the inclined region of the first optical path switching device and the maximum inclination direction of the inclined region of the second optical path switching device are orthogonal to each other Be doneIt is characterized by that.
[0018]
According to a second aspect of the invention, in the first aspect of the invention, the liquid crystal is a droplet having a particle size equal to or smaller than the wavelength of incident light.
[0019]
The invention of claim 3 is characterized in that in the invention of claim 1 or 2, all the liquid crystal molecules in the liquid crystal / polymer composite are aligned in one direction when no voltage is applied.
[0020]
The invention of claim 4 is the invention according to any one of claims 1 to 3, wherein the inclined region has a periodic structure having a sawtooth cross section.
[0021]
According to a fifth aspect of the present invention, in any one of the first to fourth aspects of the present invention, a holding substrate is provided on the two opposite surfaces of the liquid crystal / polymer composite.
[0023]
  Claim6The invention of claim5In the invention of,in frontThe exit-side holding substrate of the first light deflection element and the incident-side holding substrate of the second light deflection element are integrally formed by a single substrate.
[0024]
  Claim7The invention of claim1The present invention is characterized by having a voltage control mechanism for controlling a voltage applied to the first light deflection element and the second light deflection element in accordance with the wavelength of incident light.
[0027]
  Claim8According to the invention, at least an image display element in which a plurality of pixels capable of controlling light in accordance with image information are two-dimensionally arranged, a light source that illuminates the image display element, and the image display element are displayed. The optical member for observing the image pattern and the optical path between the image display element and the optical member are deflected for each of a plurality of subfields obtained by temporally dividing the image field.1 to 7The optical path switching described in any one ofapparatusBy optical path switching handStepIt is characterized by having.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
(Configuration / Operation)
  A feature of the present invention is that the two opposing surfaces of a liquid crystal / polymer composite (hereinafter referred to as a liquid crystal / polymer composite) in which a liquid crystal material is dispersed and held in a polymer matrix are inclined at a predetermined angle. An optical deflecting element having a region and provided with an electrode that transmits light on the two surfaces facing each other.The
[0029]
When light is incident from one surface (denoted as an incident surface) of two surfaces facing each other at a predetermined angle (referred to as α) of the liquid crystal / polymer composite, and emitted from the opposite surface (denoted as an exit surface). Since the two surfaces face each other at a predetermined angle, incident light is deflected by an angle determined by the refractive index of the liquid crystal / polymer composite, the refractive index of air, and the incident angle at the time of incidence. Considering the case where incident light is incident perpendicularly to the incident surface, there is a relationship of the following equation (1).
n · sin α = sin (θ + α) (1)
[0030]
Here, n is the refractive index of the liquid crystal / polymer composite, and θ is the deflection angle of the outgoing light with respect to the incident light. As can be seen from the equation (1), when the refractive index of the liquid crystal / polymer composite changes, the deflection angle θ changes. As will be described later, the liquid crystal / polymer composite can change the refractive index at high speed without depending on the polarization state of incident light when an electric field is applied perpendicularly to the optical path.
[0031]
  Examples of the liquid crystal / polymer composite include a liquid crystal material in which a microcapsule including a polymer film is joined using a binder resin, or a mixture of a liquid crystal material and a polymer material (or a precursor thereof). There are so-called polymer-dispersed liquid crystals in which materials are phase-separated. In any case, the structure is obtained by dispersing liquid crystal droplets in a polymer matrix, and it has been experimentally found that the response speed increases as the particle size of the liquid crystal droplets decreases. It is preferable to use a particle size of about the wavelength or less because scattering is reduced and light transmittance is increased, that is, light loss is significantly reduced.Yes.
[0032]
  All liquid crystal molecules may be aligned in one direction when no voltage is applied. A large refractive index difference can be obtained by making this direction substantially orthogonal to the direction in which liquid crystal molecules are aligned (electric field direction) when a voltage is applied. At this time, the refractive index difference depends on the polarization direction of the incident light, but it is possible to obtain a large change in the deflection angle by matching the polarization direction of the incident light with the alignment direction of the liquid crystal molecules when no voltage is applied. NaThe
[0033]
  The inclined region is preferably a periodic structure having a sawtooth cross section. This makes it easy to form a large-area optical deflecting element because the spacing between the entrance surface and the exit surface is substantially constant even when the inclined region is large.The
[0034]
  Furthermore, by providing a holding substrate on the two opposite surfaces of the liquid crystal / polymer composite as an optical path, the retention of the liquid crystal / polymer composite and the surface accuracy of the surface can be improved. Because the body is protected, high reliability is obtained.The
[0035]
  According to another aspect of the present invention, the two light deflection elements described above are used, and the light deflected by the first light deflection element is incident on the second light deflection element installed at a constant interval. The first light deflection element and the second light deflection element are arranged so that the light emitted from the second light deflection element is parallel to the original incident light.LightRoute switching deviceIn the optical path switching device equipped withAhTheAs a result, the optical paths can be switched in parallel.
[0036]
  Further, in the optical path switching device using the optical deflection element provided with the holding substrate among the optical path switching devices, the emission side holding substrate of the first optical deflection element and the incident side holding substrate of the second optical deflection element are: It is characterized by being composed of a single board.TheThis enables a low-cost optical path switching deviceOptical path switching device withCan be provided.
[0037]
  Another embodiment is characterized in that the optical path switching device has a voltage control mechanism for controlling a voltage applied to the first light deflection element and the second light deflection element in accordance with the wavelength of incident light.TheAs a result, an optical path switching device capable of obtaining a constant optical path shift amount even when the wavelength of incident light changes.Optical path switching device withCan be provided.
[0038]
  Further, in another embodiment, the optical path switching device includes a fluctuation mechanism that varies a distance between the first light deflection element and the second light deflection element according to a wavelength of incident light.TheAs a result, an optical path switching device capable of obtaining a constant optical path shift amount even when the wavelength of incident light changes.Optical path switching device withCan be provided.
[0039]
  Still another embodiment of the present invention uses two optical path switching devices described above, and the maximum inclination direction of the inclined area of the first optical path switching device and the maximum inclination direction of the inclined area of the second optical path switching device are An optical path switching device characterized by being arranged so as to be substantially orthogonal.TheThis makes it possible to switch the optical path independently in two orthogonal directions.
[0040]
  Furthermore, the number of pixels of the image display element is obtained by switching the optical path of the image of the two-dimensional image display element for each of a plurality of subfields obtained by time-dividing the image field using the optical path switching device or the optical path switching device. It becomes possible to form the above imageTheAs the number of pixels increases, it becomes difficult to manufacture an image display element due to yield and other problems. However, by using the present invention, the number of pixels can be increased relatively easily.
[0041]
Embodiment1
  FIG. 1 is a diagram for explaining a first embodiment of the present invention.
  A light beam 20 is incident on the incident surface 11 of the liquid crystal / polymer composite 14 in which the incident surface 11 and the emitting surface 12 face each other with a predetermined angle α. As shown in the above formula (1), the light beam 20 is emitted from the light exit surface 12 at the refractive index n of the liquid crystal / polymer composite 14, the refractive index of the surrounding atmosphere (usually air), and the entrance surface 11 and the exit surface. The incident light is deflected by an angle θ determined by an angle α formed by 12. When the refractive index of the liquid crystal / polymer composite changes, the deflection angle θ changes accordingly. In order to change the refractive index of the liquid crystal / polymer composite, light-transmitting electrodes 13 are provided on the incident surface 11 and the output surface 12.
[0042]
The liquid crystal / polymer composite 14 of the present invention is a liquid crystal / polymer composite in which a liquid crystal material is dispersed and held in a polymer matrix. More specifically, as shown in FIG. A polymer-dispersed liquid crystal dispersed therein. The polymer dispersed liquid crystal will be described in more detail below.
[0043]
As the liquid crystal material, nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, or the like can be used, and a single or two or more kinds of liquid crystal compounds or a mixture containing substances other than liquid crystal compounds may be used. The polymer matrix material is preferably a transparent polymer, and may be any of a thermoplastic resin, a thermosetting resin, and a photocurable resin. The polymer-dispersed liquid crystal can be produced by (1) a polymer phase separation method in which a solution is made from a liquid crystal and a heat or photocurable (polymerization) monomer, oligomer or prepolymer, and phase separation is carried out by polymerization. (2) liquid crystal and polymer Solvent evaporation phase separation method in which a solution is made with a solvent and the solvent is evaporated, phase separation is performed by evaporating the solvent, and (3) a thermal phase separation method in which liquid crystal and thermoplastic polymer are dissolved by heating and then phase separation is performed by cooling. be able to.
[0044]
As the polymer, it is preferable to use an ultraviolet curable resin from the viewpoints of the ease of the production process and the separability from the liquid crystal phase. Specific examples include ultraviolet curable acrylic resins, and those containing acrylic monomers and acrylic oligomers that are polymerized and cured by ultraviolet irradiation are particularly preferred. Examples of such a monomer or oligomer include (poly) ester acrylate, (poly) urethane acrylate, epoxy acrylate, polybutadiene acrylate, silicone acrylate, melamine acrylate, and (poly) phosphazene methacrylate. As another example, a thiol-ene system can be suitably used because of its high photocuring speed.
[0045]
Photopolymerization initiators may be used for rapid polymerization, and examples include acetophenones such as dichloroacetophenone and trichloroacetophenone, 1-hydroxycyclohexyl phenyl ketone, benzophenone, Michler ketone, benzoyl, benzoin alkyl ether, benzyldimethyl ketal. And monosulfide, thioxanthones, azo compounds, diallyl iodonium salts, triallyl sulfonium salts, bis (trichloromethyl) triazine compounds, and the like. For the light transmissive electrode, a known material such as a metal thin film deposition film or ITO can be used.
[0046]
As shown in FIG. 2, when no electric field is applied, the liquid crystal droplets 15 in the liquid crystal / polymer composite 14 have liquid crystal molecule directors oriented in a random direction, and are not oriented as a whole. In other words, the refractive index is isotropic. When an electric field 17 is applied as shown in FIG. 2B, the directors of the liquid crystal molecules in the liquid crystal droplets 15 are arranged in almost one direction. In the figure, an example of liquid crystal aligned in the electric field direction is shown. At this time, the refractive index is large in the direction in which the liquid crystal director is aligned, and is small in the direction perpendicular to the liquid crystal director. If the optical path is taken in parallel with the electric field, the refractive index in a plane perpendicular to the optical path is isotropically reduced. As described above, when the optical path is taken in a direction parallel to the electric field, the refractive index can be changed without depending on the deflection of the light by applying the electric field to the liquid crystal / polymer composite. Molding of the liquid crystal / polymer composite may be performed by transferring the shape of the mold by filling an ultraviolet transparent mold and irradiating with ultraviolet rays, or may be processed into a desired shape by post-processing. .
[0047]
The size of the liquid crystal droplets in the polymer-dispersed liquid crystal can be changed by changing the composition of the prepolymer, the mixed concentration of the liquid crystal, the ultraviolet intensity during curing, and the like. FIG. 3 is a graph showing an example of the relationship between the liquid crystal droplet size and the response speed. E7 and BL24 (Merck) were used as liquid crystal materials, and NOA 60, 65 and 81 (Noland) were used as prepolymers as appropriate.
[0048]
FIG. 4 is a diagram showing a configuration example of an apparatus for measuring the response speed of the polymer dispersed liquid crystal, in which 31 is a laser, 32 is a polarizer, 33 is a lens, 34 is a sample, 35 is an Au electrode, 36 is a polymer dispersed liquid crystal layer, 37 is a Si substrate, 38 is a lens, 39 is an analyzer, and 40 is a power meter. Regarding the measurement of the response speed, the rise time (Ton) and the fall time (Toff) of the optical output when the pulse voltage (200 V) was applied to the sample 34 were measured using the apparatus shown in FIG. However, FIG. 3 shows only the fall time (time when the voltage is turned off from on) that is more significantly affected by the size of the liquid crystal droplets. The rise time (the time when the voltage is turned on from off) mainly depends on the electric field strength, and the rise time is faster than the fall time for the electric field strength that drives this optical deflection element. The response characteristic of the deflection element can be expressed. In the sample 34, the thickness of the polymer-dispersed liquid crystal layer 36 was 20 μm, and the optical path length was 1 mm.
[0049]
The state when the electric field is not applied to the polymer dispersed liquid crystal layer 36 and when it is applied are as shown in FIG. Since the orientation of the liquid crystal droplets is random when no electric field is applied, the refractive indexes in the x-axis, y-axis, and z-axis directions are all equal, and the entire layer is an optically isotropic medium. When an electric field is applied in the z direction, the molecular axes of the liquid crystal molecules are aligned in this direction, so the refractive index in the z axis direction increases, and the refractive indexes in the x axis and y axis directions remain the same, but the size is small. Become. As shown in FIG. 4, when light is incident from the x direction perpendicular to the electric field direction, birefringence occurs in the yz plane, so that the polarization state can be changed, and the light output through the analyzer changes. In the present invention, such a birefringence phenomenon is not used, but the response speed of FIG. 3 can be similarly applied to the present invention because the behavior of liquid crystal molecules and the accompanying change in refractive index are applied when an electric field is applied. FIG. 3 shows that the response speed increases as the liquid crystal droplet size decreases.
[0050]
Furthermore, it is preferable from the viewpoint of light transmittance that the particle size of the liquid crystal droplets is about equal to or less than the wavelength of incident light, and more desirably 1/2 or less. The result of calculating the light transmittance from the Rayleigh scattering theory is shown below. When a spherical scatterer having a volume V is present at a number density N, the light transmittance T of a medium having a thickness L is expressed by the following formula (2).
T = exp (−NRL), R = 24π^Three((M²-1) / (m²+2))²V²/ Λ^Four... (2)
[0051]
Here, R is the scattering cross section, m is the ratio of the refractive index of the scatterer to the refractive index of the medium, and λ is the wavelength of the light used. The transmittance T when m = 1.05 and L = 3 μm was calculated using the particle size d, volume fraction (= NV) and wavelength λ of the scatterer, ie, liquid crystal droplets, as parameters. As can be seen from equation (2), T decreases as d increases (that is, V increases) and as λ decreases. In addition, the transmittance is preferably 80% (T = 0.8) or more from the viewpoint of light utilization efficiency. FIG. 5 shows particle diameters for which T = 0.8 with volume fractions of 10% (d (0.1)), 30% (d (0.3)) and 50% (d (0.5)). The case is plotted against wavelength. If the volume fraction is small, the amount of change in the refractive index is small and the deflection angle is small. Therefore, the volume fraction is preferably 10% or more, more preferably about 30 to 50%. If the volume fraction is higher than this, the production becomes extremely difficult. From this point of view, as shown in FIG. 5, it is preferable that d is less than or equal to the wavelength λ for the wavelength in the visible to infrared region applied as the light deflection element (when d (0.1)), λ It can be seen that the ratio is more preferably / 2 or less (when d (0.5)). In this calculation, m and L are fixed. However, since it is considered that the actual device has a smaller value, there is no problem as long as the particle size is within the above range.
[0052]
A specific example is shown. Nematic liquid crystal BL24 (no = 1.513, ne = 1.717, Merck) was dissolved in UV curable prepolymer NOA81 (Norland) (liquid crystal weight concentration 45%), and UV (400 mW / cm²) (The average particle size of the liquid crystal droplets is about 60 nm), the thickness of the liquid crystal / polymer composite is 3 μm where it is thin, 6 μm where it is thick, and the angle between the entrance surface and the exit surface is 1 A light deflection element of ° was formed. When an unpolarized laser beam (He-Ne laser: wavelength 0.6328 μm) is incident, when no electric field is applied, the deflection angle is 0.57 ° and a voltage of 300 V (average electric field strength 20 V / μm) Was applied, the refraction angle became 0.54 °, and an optical path deflection of 0.03 ° could be performed by turning the electric field on and off. At this time, the time required for the optical path deflection was on the order of 10 μs, and the optical path deflection could be performed at a very high speed. Furthermore, even if the incident light is polarized using a polarizer and the polarization direction is changed in various directions, the light path can be deflected in the same manner as when non-polarized light is incident.
[0053]
FIG. 6 is a diagram for explaining a second embodiment of the present invention.
The liquid crystal molecules contained in the liquid crystal droplets 15 in the liquid crystal / polymer composite 14 are arranged in approximately one direction (FIG. 6A). This arrangement direction is set to a direction substantially orthogonal to the direction (electric field direction) in which liquid crystal molecules are aligned when an electric field is applied (in the case of FIG. 6B). In FIG. 6A, it is oriented in a direction perpendicular to the optical path and parallel to the paper surface (z direction in FIG. 6). At this time, the refractive index of the liquid crystal / polymer composite 14 is large in the direction perpendicular to the optical path and small in the optical path direction. When an electric field is applied (in FIG. 6A), the liquid crystal molecules are aligned in the electric field direction (x direction in FIG. 6). At this time, the refractive index of the liquid crystal / polymer composite 14 is large in the optical path direction and small in the direction perpendicular to the optical path. Therefore, when the incident light is linearly polarized and the polarization direction is the orientation direction of the liquid crystal molecules when no voltage is applied (the z direction in FIG. 6), the refractive index change with respect to the incident light due to the on / off of the electric field is implemented. Since the value is larger than that in the first embodiment, the amount of change in the deflection angle θ can be increased. A specific example is shown. Liquid crystal droplets as shown in FIG. 6 (A) are obtained by applying an electric field in the z direction of FIG. 6 when polymerizing by irradiating ultraviolet rays using polymer liquid crystal of the same material and formulation as in the first embodiment. The liquid crystal molecules in 15 were aligned. When a laser beam polarized in the z direction (He-Ne laser, wavelength 0.6328 μm) is incident, the deflection angle is 0.61 ° when no electric field is applied, and a voltage of 300 V (average electric field strength 20 V / μm). ) Was applied, the deflection angle became 0.54 °, and the optical path deflection of 0.07 ° could be performed by turning the electric field on and off.
[0054]
Embodiment3
  FIG. 7 is a diagram for explaining a third embodiment of the present invention, and shows a different configuration example of the optical deflection element in FIGS. 7A and 7B, respectively. Here, a region formed by the emission surface 12 provided to be inclined with respect to the incident surface 11 of the light deflection element is defined as an inclined region. When the incident surface 11 is used as a reference, the angle between the reference surface and the inclined surface is α, the length of the inclined surface in the direction parallel to the reference surface is L, and the maximum difference in the distance from the reference surface on the inclined surface is When the maximum step d is used, as shown in FIG. 7A, the maximum step d is Ltanα and the length L of the tilt region is increased when the slope is formed with one slope as shown in FIG. The maximum step d is also increased. Since the electrode for applying an electric field to the liquid crystal / polymer composite is provided on the surface of the liquid crystal / polymer composite, when the maximum step d increases, the electric field strength decreases and the refractive index change amount of the liquid crystal / polymer composite decreases. Thus, the amount of change in refractive index is insufficient. Alternatively, a very high voltage must be applied to obtain a sufficient refractive index change. In addition, since the electrode interval varies depending on the location, the intensity of the applied electric field varies depending on the location, and a distribution occurs in the refractive index change. Therefore, in order to apply an electric field uniformly at a lower voltage, a periodic structure having a sawtooth cross section is provided as shown in FIG. As a result, even when the area is increased, the maximum step d can be reduced, and thus it is possible to drive at a low voltage.
[0055]
A specific example is shown. An optical deflecting element having a thick portion of 2 μm, a thin portion of 1 μm, a sawtooth-shaped pitch of 57 μm, and an angle between the incident surface and the exit surface of 1 ° was formed by the same material and method as in the first embodiment. Optical path deflection of 0.03 ° could be performed in the same manner as in the first embodiment with applied voltages of 0 V and 30 V (average electric field strength of 20 V / μm).
[0056]
Embodiment4
  FIG. 8 is a schematic configuration diagram for explaining a fourth embodiment of the present invention.
  The optical deflection element 50 is configured by providing a holding substrate 18 on the surfaces of the incident surface 11 and the emitting surface 12 of the liquid crystal / polymer composite 14. Thereby, the retainability of the liquid crystal / polymer composite 14 is improved, the surface accuracy of the entrance surface 11 and the exit surface 12 is improved, and the directionality of the light beam is stabilized. In addition, since the liquid crystal / polymer composite 14 is protected, the reliability is improved.
[0057]
A specific example is shown. The surface of the optical glass BK7 (refractive index: nd = 1.517) was etched into a sawtooth shape having a depth (step d) = 1 μm, an inclination angle (α) = 1 °, and a pitch (p) = 57 μm. Thereafter, ITO was vapor-deposited on the sawtooth-shaped surface, and the peripheral part was held with a 1 μm spacer and bonded to another flat plate of BK7 with ITO. A material similar to that in the first embodiment was injected into a space formed inside, and an optical deflection element was formed by irradiating ultraviolet rays under the conditions of the first embodiment. An optical path deflection of 0.03 ° was confirmed by applying voltages of 0V and 30V. Since the holding substrate is provided, the handling is easy, and the reliability of the deflection amount of the optical path is better than that in the second embodiment.
[0058]
Embodiment5
  FIG. 9 is a diagram for explaining a fifth embodiment of the present invention, and shows a configuration example of an optical path switching device using the optical deflection element of the present invention.
  The optical path switching device 60 prepares two light deflecting elements shown in the fourth embodiment (light deflecting elements 50a and 50b), and the light deflected by entering the first light deflecting element 50a is the second light. The second light deflection element 50b is arranged and configured so as to be emitted in parallel with the incident light to the first deflection element 50a by passing through the deflection element 50b. Specifically, the second light deflection element 50b has an incident surface opposite to the first light deflection element 50a (for example, when the first light deflection element 50a has the plane side as the incident surface). The second light deflection element 50b has a sawtooth-shaped side as an entrance surface, and the tilt direction of the tilt region is the same as that of the first light deflection element 50a (the tilt surfaces of the first and second light deflection elements are mutually aligned). (Parallel). The distance between the two light deflection elements is set so as to obtain a necessary optical path shift amount. The optical path shift amount is Δ, the average distance between the tilt region of the first light deflection element 50a and the tilt region of the second light deflection element 50b is D, and the liquid crystal / polymer composite in the first light deflection element 50a is The deflection angle corresponding to the refractive index change is θ₁And θ₂Then, it becomes like the following formula.
      Δ = D (tan θ₂−tan θ₁(3)
[0059]
Deflection angle θ₁And θ₂Is related to the refractive index of the liquid crystal / polymer composite 14 by the equation (1), the distance between the light deflection elements 50a and 50b from the required optical path shift amount Δ by the equations (1) and (3). Can be determined. The optical path switching device 60 configured as described above simultaneously applies the same voltage to both the first optical deflection element 50a and the second optical deflection element 50b. As a result, the light deflected by the first light deflection element 50a passes through the second light deflection element 50b and becomes parallel to the incident light, thereby realizing a parallel optical path shift element.
A specific example is shown. The light deflection element of the third embodiment was installed so that D = 19 mm in the arrangement of FIG. An optical path shift of 10 μm was obtained by simultaneously applying a voltage of 0 V or 30 V to the two optical deflection elements.
[0060]
Embodiment6
  FIG. 10 is a diagram for explaining a sixth embodiment of the present invention and shows another configuration example of the optical path switching device. In the optical path switching device 60 ′, the liquid crystal / polymer composite 14 is provided in the same manner as in the fourth embodiment. However, the first optical deflection element 50a and the second optical deflection shown in the fourth embodiment are used. One intermediate substrate 19 is integrally provided between the liquid crystal / polymer composite 14 corresponding to the element 50b. At this time, the optical path shift amount is Δ, the length of the intermediate substrate 19 is D ′, and the first optical deflection element section (the deflection angle between the liquid crystal / polymer composite 14 on the incident side and the intermediate substrate 19) is used. The deflection angle is θ₁And θ₂Then, it becomes like the following formula.
  Δ = D ′ (tan θ₂−tan θ₁(4)
  Deflection angle θ₁And θ₂Is related to the refractive index of the liquid crystal / polymer composite by the equation (1), the thickness of the intermediate substrate 19 can be determined from the required optical path shift amount by the equations (1) and (4). It becomes.
[0061]
A specific example is shown. Both surfaces of a 29 μm-thick optical glass BK7 (refractive index: nd = 1.517) are formed on the intermediate substrate 19 shown in FIG. 10 in shape (depth (d) 1 μm, tilt angle (α) 1 °, pitch (p ) 57 [mu] m sawtooth shape). Thereafter, ITO was vapor-deposited on the sawtooth-shaped surface to form an electrode 13, and the peripheral part was held with a 1 μm spacer, and another flat plate of BK7 with ITO was bonded to both surfaces of the intermediate substrate 19. The same material as in the first embodiment was injected into the space formed inside, and ultraviolet light was irradiated under the conditions of the first embodiment to form the optical path switching device 60 '. By simultaneously applying a voltage of 0 V or 30 V to the two liquid crystal / polymer composites 14, an optical path shift of 10 μm was obtained.
[0062]
Embodiment7
  FIG. 11 is a diagram for explaining the seventh embodiment of the present invention, and shows still another configuration example of the optical path switching device. In the present embodiment, a voltage is applied to the optical path switching device 60 ′ shown in the fifth embodiment via the voltage control mechanism 61 that can control the voltage according to the wavelength of incident light. In general, since the refractive index of a liquid crystal / polymer composite, a holding substrate, air, and the like varies depending on the wavelength of light, in the configuration shown in the fourth embodiment, the deflection angle changes when the wavelength of incident light changes, and therefore the optical path shift. The amount Δ may change depending on the wavelength. The voltage control mechanism 61 controls the refractive index of the liquid crystal / polymer composite 14 to correct the deviation of the optical path shift amount Δ due to this wavelength, so that a constant optical path shift amount Δ is always obtained.
[0063]
Embodiment8
  FIG. 12 is a diagram for explaining the eighth embodiment of the present invention and shows still another configuration example of the optical path switching device. In this embodiment, in the optical path switching device 60 shown in the fifth embodiment, the first light deflection element 50a is caused to vary the distance D between the first light deflection element 50a and the second light deflection element 50b. The fluctuation mechanism 62 is provided. The variation mechanism 62 changes the distance D between the first light deflection element 50a and the second light deflection element 50b in accordance with the wavelength of the incident light 20. The variation mechanism 62 varies the optical deflection element interval D so as to compensate for the shift of the optical path shift amount Δ due to this wavelength, so that a constant optical path shift amount is always obtained. Examples of the deflection mechanism 62 include various existing methods such as a method using electrostatic force, a method using magnetism, and a method using electrostriction or magnetostriction.
[0064]
Embodiment9
  FIG. 13 is a diagram for explaining a ninth embodiment of the present invention and shows a configuration example of an optical path switching device. Two optical path switching devices 60 ′ described above are prepared (optical path switching devices 60′a and 60′b), the maximum tilt direction of the tilt region of the first optical path switching device 60′a, and the second optical path switching device 60. It arrange | positions so that the largest inclination direction of 'b inclination area may be orthogonally crossed substantially. The incident light 20 undergoes a vertical optical path shift by the first optical path switching device 60'a, and a lateral optical path shift by the second optical path switching device 60'b. As a result, optical path shifts in both the X and Y directions can be realized.
[0065]
A specific example is shown. Two optical path switching devices 60 ′ of the sixth embodiment are arranged as shown in FIG. 13 (optical path switching devices 60′a and 60′b), and a voltage is applied to each optical path switching device in the sequence shown in FIG. . At this time, an optical path shift as shown in FIG. 15 was performed at timings A to D in the figure, and a two-dimensional optical path shift was realized.
[0066]
Embodiment 10
  FIG. 16 is a view for explaining the tenth embodiment of the present invention, and shows a configuration example of an image display apparatus using the optical path switching device of the present invention. In the image display device 70, reference numeral 71 denotes a light source in which LED lamps are arranged in a two-dimensional array, and in the traveling direction of light emitted from the light source 71 toward the screen 76, a diffusion plate 72, a condenser lens 73, an image display element. And a projection lens 75 as an optical member for observing the image pattern. In the figure, reference numeral 77 denotes a light source drive unit for the light source 71, and 78 denotes a liquid crystal drive unit for the transmissive liquid crystal panel 74.
[0067]
Here, on the optical path between the transmissive liquid crystal panel 74 and the projection lens 75, optical path switching means 80 functioning as a pixel shift element is interposed and connected to the drive unit 79. As such an optical path switching means 80, an optical path switching device or an optical path switching device as exemplified in the above-described embodiment is used.
[0068]
The illumination light that is controlled by the light source drive unit 77 and emitted from the light source 71 becomes illumination light that is made uniform by the diffusion plate 72, and is controlled by the condenser lens 73 in synchronization with the illumination light source by the liquid crystal drive unit 78. The liquid crystal panel 74 is critically illuminated. The illumination light that has been spatially modulated by the transmissive liquid crystal panel 74 enters the optical path switching unit 80 as image light, and the optical path switching unit 80 shifts the image light by an arbitrary distance in the pixel arrangement direction. This light is magnified by the projection lens 75 and projected onto the screen 76.
[0069]
An image pattern in which the display position is shifted in accordance with the deflection of the optical path for each of the plurality of subfields obtained by temporally dividing the image field by the optical path switching unit 80 is displayed. The number of apparent pixels is multiplied and displayed. Thus, the shift amount by the optical path switching means 80 is set to ½ of the pixel pitch because the pixel multiplication is performed twice as much as the pixel arrangement direction of the transmissive liquid crystal panel 74. By correcting the image signal for driving the transmissive liquid crystal panel 74 by the shift amount according to the optical path shift amount, an apparently high-definition image can be displayed. At this time, since the optical path switching device or the optical path switching device as in each of the above-described embodiments is used as the optical path switching means 80, the light use efficiency is improved and the observer can increase without increasing the load of the light source. Bright and high quality images can be provided.
[0070]
Further, in the case of a configuration in which non-polarized light can be used as incident light, the image display element is not limited to the above-described transmissive liquid crystal panel, and any image such as a light scattering liquid crystal panel or a DMD (digital micromirror device). The display element can be used as it is.
[0071]
【The invention's effect】
  As is clear from the above explanation,According to the present invention, two optical path switching devices are provided, and the maximum inclination direction of the inclined area of the first optical path switching device and the maximum inclination direction of the inclined area of the second optical path switching device are arranged so as to be substantially orthogonal to each other. By doing so, an optical path switching device capable of shifting the optical path in two orthogonal directions can be provided. Also,Main departureClearlyAccording to the present invention, the liquid crystal / polymer composite in which the liquid crystal material is dispersed and held in the polymer matrix has an inclined region where the two opposing surfaces face each other at a predetermined angle, and light is transmitted through the surfaces of the two opposing surfaces. By providing the electrodeThe light deflection element,Simple configuration that does not depend on polarization and operates at high speedWhencan do. In addition to the above, by making the liquid crystal a droplet having a particle size equal to or smaller than the wavelength of incident light,Optical deflection elementOperates at high speedLetCan.
[0072]
  Also, by ensuring that all liquid crystal molecules are aligned in one direction when no voltage is applied,Optical deflection elementChange in deflection angleThebigThecan do.
[0073]
  In addition to the above, the optical path can be shifted even in a large area by making the inclined region of the optical deflection element a periodic structure with a sawtooth cross section.Optical deflection elementCan be driven at low voltageWhencan do. Also, by providing a holding substrate on the two opposite surfaces of the liquid crystal / polymer composite,Optical deflection elementStabilityTheHighDullCan.
[0074]
lightThe first light deflecting element has two deflecting elements, and the light deflected by the first light deflecting element is parallel to the incident light by the second light deflecting element installed at a predetermined interval. And by arranging the second light deflection element,Optical path switching deviceDeflect the optical path in parallelRukoYou can.
[0075]
  An optical deflection element provided with a holding substrate is used as the first optical deflection element and the second optical deflection element, and the emission side holding substrate of the first optical deflection element and the incident side holding of the second optical deflection element. By integrally configuring the substrate with a single substrate,Optical path switching devicelow costIncan do.
[0076]
  In addition, by having a voltage control mechanism that changes the voltage applied to the first light deflection element and the second light deflection element according to the wavelength of the incident light,Optical path switching deviceEven if the wavelength of incident light changes, a certain amount of optical path shift can be obtained.likecan do. Also, by providing a variation mechanism that varies the distance between the first light deflection element and the second light deflection element according to the wavelength of the incident light,Optical path switching deviceEven if the wavelength of incident light changes, a certain amount of optical path shift can be obtained.likecan do.
[0078]
  At least 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 an image pattern displayed on the image display element The present invention deflects the optical path between the image display element and the optical member for each of an optical member for observation and a plurality of subfields obtained by temporally dividing the image field.Light ofBy providing the optical path switching means by the path switching device, 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.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a first embodiment of the present invention.
FIG. 2 is a diagram conceptually showing a polymer-dispersed liquid crystal used as a liquid crystal / polymer composite.
FIG. 3 is a graph showing an example of a relationship between a liquid crystal droplet size and a response speed.
FIG. 4 is a diagram showing a configuration example of an apparatus for measuring the response speed of a polymer dispersed liquid crystal.
FIG. 5 is a graph in which the particle diameter at which the transmittance is 80% is plotted against the wavelength.
FIG. 6 is a diagram for explaining a second embodiment of the present invention.
FIG. 7 is a diagram for explaining a third embodiment of the present invention.
FIG. 8 is a schematic configuration diagram for explaining a fourth embodiment of the present invention.
FIG. 9 is a diagram for explaining a fifth embodiment of the present invention.
FIG. 10 is a diagram for explaining a sixth embodiment of the present invention.
FIG. 11 is a diagram for explaining a seventh embodiment of the present invention and shows still another configuration example of the optical path switching device.
FIG. 12 is a view for explaining an eighth embodiment of the present invention and shows still another configuration example of the optical path switching device.
FIG. 13 is a view for explaining a ninth embodiment of the present invention and shows a configuration example of an optical path switching device.
FIG. 14 is a diagram illustrating an example of a sequence of voltages applied to an optical path switching device.
15 is a diagram for explaining an optical path shift corresponding to the sequence of FIG. 14;
FIG. 16 is a diagram for explaining a tenth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Incident surface, 12 ... Output surface, 13 ... Electrode, 14 ... Liquid crystal / polymer composite, 15 ... Liquid crystal droplet, 16 ... Polymer, 17 ... Electric field, 18 ... Holding substrate, 19 ... Intermediate substrate, 20 ... Light 31 ... Laser, 32 ... Polarizer, 33 ... Lens, 34 ... Sample, 35 ... Au electrode, 36 ... Polymer dispersed liquid crystal layer, 37 ... Si substrate, 38 ... Lens, 39 ... Analyzer, 40 ... Power meter, 50, 50a, 50b ... optical deflection element, 60, 60 '... optical path switching device, 60'a ... first optical path switching device, 60'b ... second optical path switching device, 61 ... voltage control mechanism, 62 ... fluctuation Mechanism: 70 ... Image display device, 71 ... Light source, 72 ... Diffuser, 73 ... Condenser lens, 74 ... Transmission type liquid crystal panel, 75 ... Projection lens, 76 ... Screen, 77 ... Light source drive unit, 78 ... Liquid crystal drive unit, 9 ... drive unit, 80 ... optical path switching means.

Claims (8)

An optical path switching device that switches an optical path of incident light by an electrical signal,
The optical path switching device includes a first optical path switching device and a second optical path switching device each including two optical deflecting elements that change the deflection angle of outgoing light with respect to incident light in accordance with a change in refractive index of the liquid crystal / polymer composite. An optical path switching device,
Each of the optical deflection elements provided in each of the optical path switching devices includes a liquid crystal / polymer composite in which a liquid crystal material is dispersed and held in a polymer matrix, and a voltage for changing the refractive index of the liquid crystal / polymer composite. A light deflecting element that changes a deflection angle of outgoing light with respect to incident light in accordance with a change in refractive index of the liquid crystal / polymer composite. The composite has an inclined region where one surface is inclined at a predetermined angle with respect to the other surface on two surfaces facing each other on the optical path, and the electrode is disposed on the surfaces of the two facing surfaces ,
Each of the optical path switching devices includes a first optical deflecting element so that the light deflected by the first optical deflecting element is parallel to the incident light by the second optical deflecting element installed at a predetermined interval. And the second light deflection element is disposed,
And the maximum inclination direction of the inclined region of the first optical path switching device, the second optical path switching device and the maximum inclination direction of the inclined region of the optical path switching device is characterized by comprising arranged to be orthogonal. The optical path switching device according to claim 1, wherein the liquid crystal is a droplet having a particle diameter equal to or smaller than a wavelength of incident light. 3. The optical path switching device according to claim 1, wherein all liquid crystal molecules in the liquid crystal / polymer composite are aligned in one direction when no voltage is applied. 4. The optical path switching device according to claim 1, wherein the inclined region has a periodic structure having a sawtooth cross section. 5. The optical path switching device according to any one of claims 1 to 4, wherein a holding substrate is provided on the surfaces of the two opposing surfaces of the liquid crystal / polymer composite. Of claim 5 in which the incident-side holding the substrate before Symbol first light deflecting element and the second the exit side holding the substrate of the optical deflecting device is characterized in that it is integrally formed by a single substrate Optical path switching device . 2. The optical path switching device according to claim 1 , further comprising a voltage control mechanism that controls a voltage applied to the first light deflection element and the second light deflection element in accordance with a wavelength of incident light. At least 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 an image pattern displayed on the image display element are observed. An optical path according to any one of claims 1 to 7 , wherein an optical path between the image display element and the optical member is deflected for each of a plurality of subfields obtained by temporally dividing an image field and an optical member for performing the operation. the image display apparatus comprising the optical path switching hands stage by switching device.

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