JP4057320B2 - Optical path deflecting device and image display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical path deflecting device and an image display device including the optical path deflecting device and applied to an electronic display device such as a projection display or a head mounted display. More specifically, an image obtained by observing an image obtained by magnifying an optical path deflecting device that shifts the optical axis to increase the number of actual pixels and a small image display element having a plurality of pixels that can control light according to image information with a lens. The present invention relates to a display device, and more particularly to a pixel shift type image display device that uses the optical path deflecting device to shift the optical axis to increase the number of actual pixels.
[0002]
[Prior art]
As a conventional technique related to an image display device, a technique for high-resolution display by apparently multiplying the number of pixels of an image display element is known.
For example, Japanese Patent Laid-Open No. 6-324320 “Image display device, resolution improvement method of image display device, imaging method, recording device, and playback device” displays without increasing the number of pixels of an image display device such as an LCD. It is described that the resolution of an image is apparently improved. Further, each of the plurality of pixels arranged in the vertical direction and the horizontal direction emits light according to the display pixel pattern, so that an optical path is provided between the image display device on which the image is displayed and the observer or the screen. It is described that an optical member for deflecting each of the fields is arranged. Further, it is described that a display pixel pattern whose display position is shifted in accordance with the deflection of the optical path is displayed on the image display device for each field. Further, the optical path may be deflected by causing the portions having different refractive indexes to appear alternately in the optical path between the image display device and the observer or the screen for each field of the image information. Are listed.
[0003]
Japanese Patent Application Laid-Open No. 10-020242 “Projection Display Device” describes that pixel shift is performed by combining an image display element and a microlens array and vibrating the microlens array.
Further, as a content directly related to the present invention, in the text, “in this embodiment, the microlens array 4 corresponding to a plurality of pixels is moved and changed, but light emitted from a plurality of pixels adjacent to the light modulation element is respectively changed. For example, there is a need to have a condensing unit in which a plurality of condensing optical elements included in the aperture of the lens are arranged adjacent to each other and a unit for deflecting the projection area so as to interpolate a projection image made discrete by the condensing unit. (Sato Susumu; Focus-variable lens using liquid crystal, Optical Technology Contact, Vol. 32, No. 11, p. 24 to p. 28, 1994) A liquid crystal lens as disclosed in FIG. The voltage may be selectively applied to change the lens formation position. " However, it is relatively easy to change the focal length in the direction of the optical axis in the liquid crystal microlens array having the circular hole pattern described in the above document, but the focusing position can be changed in the arrangement direction of the lens array. I can't.
[0004]
Therefore, as a technique for controlling the condensing position in the lens array plane direction, a method using divided electrodes is disclosed as in JP-A-11-109304. However, when the liquid crystal lens having the divided electrodes is formed in an array, the electrode wiring becomes complicated, and therefore, the lens formation interval must be set relatively wide. Further, it is suitable when the installation interval may be relatively wide, such as a combination of a semiconductor laser array and a plurality of optical fibers as disclosed in JP-A-11-109304, but the pixel pitch of the image display element is suitable. When the interval is relatively narrow as described above, there is a problem that the aperture ratio of the lens forming portion becomes small.
[0005]
US Pat. No. US Pat. No. 6,082,862 “IMAGE TILING TECHNIQUE BASED ON ELECTRICALLY SWITCHABLE HOLOGRAMS” discloses a projection system using a holographic optical element capable of electrical switching. It is described that the position of the display image is shifted at high speed by changing it at high speed.
[0006]
As a technique for deflecting an optical path, for example, in Japanese Patent Application Laid-Open No. 10-133135, “Light Beam Deflector”, a rotary machine element can be eliminated, and the overall size can be reduced, and high accuracy and high resolution can be realized. We have proposed a light beam deflecting device that is not easily affected by the vibration of the light beam.
This light beam deflecting device includes a translucent piezoelectric element disposed on a traveling path of a light beam, a transparent electrode provided on the surface of the piezoelectric element, a light beam incident surface A of the piezoelectric element, and a light beam emission. Voltage applying means for applying a voltage to the piezoelectric element through the electrode in order to change the optical path length between the surface B and deflect the optical axis of the light beam.
[0007]
For example, IBM Technical Disclosure Bulletin, Vol.15, No.8 (1973) “LIGHT SCANNER EMPLOYING A NEMATIC LIQUID CRYSTAL” is an optical deflection technology that uses liquid crystals, by changing the alignment angle of nematic liquid crystals. The bending of the optical path is described.
Further, ELECTRONICS LETTERS, Vol. 11, No. 16 (1975) “LARGE-ANGLE BEAM DEFLCTOR USING LIQUID CRYSTAL” describes that a non-uniform electric field is applied to a nematic liquid crystal to bend the optical path of linearly polarized light.
However, both are single beam deflectors and cannot be applied to pixel shift of a two-dimensional image as they are.
[0008]
As a technology related to liquid crystal microlenses, O plus E, Vol.20, No.10 (1998) "Liquid crystal microlens" uses a liquid crystal microlens with an electrode division structure to make the electric field distribution asymmetric, It is described that the focal point can be moved in directions other than the optical axis direction.
However, it is suitable for two-dimensional control of the deflection direction of a single beam, but in the case of arraying, the electrode wiring becomes complicated. Therefore, an array beam deflection device such as an image display element is used. Not suitable for application.
[0009]
Japanese Patent No. 0316744 “Liquid Crystal Microlens” describes that a polymer is formed by photopolymerization in a nematic liquid crystal. It also describes that it has memory characteristics and the lens characteristics can be made variable.
Furthermore, the “optical coupler” in JP-A-11-109303 and JP-A-11-109304 uses a liquid crystal microlens in which circular hole pattern electrodes are arranged in an array, and the focal length is variable. It is described that the light coupling efficiency of the optical interconnection element can be made variable, and that the focal position can be controlled by the divided electrodes.
However, in the case of an array, the electrode wiring becomes complicated, so the lens formation interval must be set relatively wide. It is suitable when the installation interval may be relatively wide, such as a combination of a semiconductor laser array and a plurality of optical fibers, but when the interval is relatively narrow, such as the pixel pitch of an image display element, a lens forming portion The aperture ratio of the will become small.
[0010]
[Problems to be solved by the invention]
As an image display device for observing an image obtained by magnifying an image display element having a plurality of pixels capable of controlling light according to image information with a lens, it is widely used under the trade names of front projector, rear projector, head mounted display, etc. Yes. As this image display element, CRT, liquid crystal panel, DMD (trade name: Texas Instruments Inc .: USA) and the like are used as products, and inorganic EL, inorganic LED, organic LED, etc. are also being studied. . In addition to observing an image obtained by magnifying a small image display element with a lens, the image display device for observing at an equal magnification, in addition to the aforementioned CRT, liquid crystal panel, inorganic EL, inorganic LED, and organic LED, Plasma displays, fluorescent display tubes, and the like are used as products, and FED (field emission display), PALC (plasma addressing display), and the like have been studied. These are broadly classified into two types, a self-luminous type and a spatial light modulator type, and each has a plurality of pixels that can control light.
[0011]
A problem common to these image display devices is to increase the resolution, that is, to increase the number of pixels, and a display device for HDTV having about 1000 scanning lines for the purpose of broadcast display has already been commercialized. A development product with about 2000 scanning lines aimed at high-resolution display of computers has been announced with technology using liquid crystal panels (QSXGA 2048 from IBM Japan, '99 electronic display at the '98 flat panel display exhibition) (Toshiba's 2400 UXGA, etc.) However, increasing the number of pixels reduces the yield of the liquid crystal panel and decreases the aperture ratio, thereby increasing costs, decreasing brightness and contrast, and increasing power consumption. .
[0012]
In response to these problems, Japanese Patent Application Laid-Open No. 4-113308, Japanese Patent Application Laid-Open No. 5-289004, Japanese Patent Application Laid-Open No. 6-324320, etc. use an image display element having a double number of pixels. An image display device for displaying a race is described. Japanese Patent Application Laid-Open No. 7-36054 describes a display device having a pixel number four times or more using a single image display element. These are so-called pixel shift methods, in which the optical path emitted from the image display element is deflected at high speed in a time-sharing manner to increase the number of pixels apparently. JP-A-6-324320 describes 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, etc. as means for deflecting the optical path. No. 7-104278 describes means for moving the wedge prism. A combination of a member exhibiting an electro-optic effect and a birefringent crystal is a known technique as a deflecting means that has been conventionally used as an optical switch or an optical switch in the field of optical communication. However, a relatively large birefringent crystal is required, which increases the device cost. In addition, as a lens shift mechanism, that is, a drive system that reciprocates, a voice coil, a piezoelectric element, a bimorph, a step motor, a solenoid coil, and the like are described, but when a reciprocating motion is performed at about several tens to several hundred Hz, Generation of vibration and sound becomes a problem. Since the vari-angle prism also reciprocates the substrate, vibration and sound become a problem. Japanese Patent Laid-Open No. 5-313116 describes a pixel shift method in which the image display element itself is swung at a high speed by a distance smaller than the pixel pitch. In this method, the optical system is fixed and the occurrence of various aberrations is small. However, since the image display element itself must be translated accurately and at high speed, the accuracy and durability of the movable part is required, and vibration and Sound is a problem.
[0013]
Japanese Patent Laid-Open No. 10-133135 proposes a method in which a light-transmitting piezoelectric element is sandwiched between transparent electrodes and a thickness is changed by applying a voltage to shift the optical path. An element is required, and the apparatus cost increases.
JP-A-6-208345 and JP-A-6-324320 disclose a method for changing the shift amount of the optical path by switching the thickness and the inclination angle of a transparent plate-like refracting plate. A configuration in which the thickness and inclination angle of a refracting plate of one circular rotating body are partially different is illustrated. However, there is a problem that the entire optical system becomes large because a single circular rotating body is an optical path shift only in a one-dimensional direction and a relatively large circular rotating body is included.
[0014]
The present invention has been made to solve the above problems, and in an optical path deflecting device that deflects light two-dimensionally using two optical path deflecting means, the alignment direction and lines of the liquid crystal of the optical path deflecting means. By defining the relative positional relationship of the electrodes, it is intended to shorten the time for creating the device and reduce the cost. In addition, the present invention uses the above optical path deflecting device, does not provide a mechanical vibration mechanism, performs optical path shift by an electro-optic effect with a relatively simple electrode configuration, and does not reduce the light utilization efficiency. An object of the present invention is to provide an image display apparatus having a configuration capable of obtaining a high-definition image by apparent pixel multiplication and improving display quality.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is used in an image display device, and the optical path of the emitted light from each pixel provided corresponding to the two-dimensional orientation direction of the pixel of the image display element. An optical path deflecting device having optical path deflecting means composed of a deflecting optical deflecting element, The first optical path deflecting means capable of moving the polarization or focal position of the optical path along the first pixel arrangement direction with respect to the two-dimensional orientation direction of the pixels and the optical path along the second pixel arrangement direction. A pair of optical path deflecting means composed of a second optical path deflecting means capable of deflecting or moving the focal position, and a polarization plane rotating means provided between the pair of optical path deflecting means, Each of the optical deflection elements of the pair of optical path deflecting means is provided between two substrates, a line electrode array formed on at least one substrate corresponding to the pixel pitch, and a voltage applied between the two substrates. A liquid crystal layer capable of controlling the refractive index distribution, and an alignment film that is provided in contact with at least one liquid crystal layer interface and regulates the direction of the liquid crystal molecules, and alignment processing of the alignment film with respect to the line electrode in each light deflection element It is characterized by the same direction.
[0016]
According to a second aspect of the present invention, in the optical path deflecting device according to the first aspect, the alignment treatment direction of the alignment film of the optical deflection element is substantially parallel to the line direction of the line electrode.
According to a third aspect of the present invention, in the optical path deflecting device according to the first aspect, the alignment treatment direction of the alignment film of the optical deflection element is set to 45 ° to 135 ° from the line direction of the line electrode. Yes.
According to a fourth aspect of the present invention, in the optical path deflecting device according to the first aspect, the liquid crystal layer of the optical deflection element includes a polymer.
[0017]
The invention according to claim 5 is the optical path deflecting device according to claim 1, wherein As a polarization plane rotation means The polarization plane of linearly polarized light Said From the first pixel array direction Said A polarization plane rotating means made of a polymer liquid crystal that rotates in the second pixel arrangement direction is provided.
According to a sixth aspect of the present invention, in the optical path deflecting device according to the first aspect, one substrate of the optical deflection element is subjected to a vertical alignment process.
Further, the invention according to claim 7 is the optical path deflecting device according to claim 1, characterized in that the alignment film of the optical deflection element can generate an alignment regulating force by light irradiation.
[0018]
The invention according to claim 8 is 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 and an illumination device for illuminating the image display element, and display on the image display element Corresponding to the two-dimensional orientation direction of the pixels of the image display element, an optical device for observing the image pattern, display driving means formed by a plurality of subfields obtained by temporally dividing the image field, and Set up Kerare The And an optical path deflecting device having an optical path deflecting unit composed of an optical deflecting element that deflects an optical path of light emitted from each pixel, and an image pattern in which the display position is shifted according to the deflected state of the optical path for each subfield. In the image display device which displays by multiplying the apparent number of pixels of the image display element by displaying, the optical path deflecting device according to any one of claims 1 to 7 as the optical path deflecting device. It is characterized by having prepared.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration, operation and action of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory diagram illustrating the configuration of an image display apparatus according to an embodiment of the present invention. The image display device includes a light source 1, a light source driving unit 2, an illumination device 3, an image display element 4, a display driving unit 5, an optical path deflecting device 6, an optical path deflection driving unit 7, an image display control circuit 8, a projection lens 9, and a screen. 10 or the like. Any light source 1 can be used as long as it can turn on / off white light or an arbitrary color light at high speed. For example, a combination of an LED lamp, a laser light source, a white lamp light source and a shutter can be used. The illumination device 3 uniformly irradiates the image display element 4 with the light emitted from the light source 1, and includes a fly-eye lens, a diffusion plate, a condenser lens, and the like. The image display element 4 emits incident uniform illumination light after spatial light modulation, and a transmissive liquid crystal light valve, a reflective liquid crystal light valve, a DMD element, or the like can be used.
[0020]
The light emitted from the light source 1 under the control of the light source driving means 2 becomes illumination light that is made uniform by the diffusion plate of the illumination device 3, and critically illuminates the image display element 4 by the condenser lens. Here, a transmissive liquid crystal light valve is used as an example of the image display element 4. Illumination light spatially modulated by the liquid crystal light valve 4 is enlarged by the projection lens 9 and projected onto the screen 10 as image light. Here, the image light is shifted by an arbitrary distance in the pixel arrangement direction by the optical path deflecting device 6 disposed behind the liquid crystal light valve 4.
[0021]
In the configuration of FIG. 1, the optical path deflecting device 6 is installed immediately after the liquid crystal light valve 4, but is not limited to this position, and may be just before the screen. However, when installed near the screen, the size, electrode pitch, etc. of the optical path deflecting means (for example, liquid crystal light deflecting element) constituting the optical path deflecting device 6 are set according to the screen size and pixel size at that position. In any case, it is preferable that the shift amount is 1 / integer of the pixel pitch. When performing image multiplication twice as much as the pixel arrangement direction, the pixel pitch is set to 1/2. When performing pixel multiplication of 3 times, the pixel pitch is set to 1/3. By using the optical path deflecting means constituting the optical path deflecting device 6 in two dimensions vertically and horizontally in the pixel array direction (for example, by using two optical deflecting elements that perform double image multiplication as the optical path deflecting device 6), As shown in FIG. 2, an effect that is four times as large as an apparent pixel is obtained, and a high-definition image that is higher than the resolution of the used liquid crystal light valve 4 can be displayed. Further, when the shift amount becomes large due to the configuration of the optical path deflecting device 6, the shift amount may be set to a distance of "integer multiple + 1 / integer" of the pixel pitch. In either case, the liquid crystal light valve 4 is driven by the image signal of the subfield corresponding to the pixel shift position.
[0022]
In the configuration of FIG. 1, a single-color image display device using a single-plate transmissive liquid crystal light valve and a single-color LED lamp is shown, but using a three-color light source / illumination device and three image display elements, 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 a single-panel image display element is illuminated with three primary colors in time sequence. At this time, 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 combining a white lamp light source and a rotating color filter.
[0023]
The present invention is characterized in that pixel multiplication is performed in two vertical and horizontal directions by the optical path deflecting device 6. Specifically, the optical path deflecting device 6 having the configuration shown in FIG. 3 is used. The optical path deflecting device 6 includes a first optical path deflecting means 6a for shifting the optical path in a direction perpendicular to the paper surface of FIG. 1 (SX direction in FIG. 3), and a vertical direction of the paper surface in FIG. 1 (SY direction in FIG. 3). The second optical path deflecting means 6b to be shifted to the first and second polarization plane rotating means 6c provided therebetween. In the present invention, as the optical path deflecting device 6, a total of two optical path deflecting means (optical deflecting elements) 6 a, each of which is a liquid crystal cell capable of controlling the refractive index distribution by applying a voltage with respect to the two-dimensional arrangement direction of the pixels. , 6b, and multiplying the apparent number of pixels of the image display element 4 for display. The first and second optical path deflecting means (light deflecting elements) 6a, 6b Two substrates, a line electrode array formed on at least one substrate corresponding to the pixel pitch, a liquid crystal layer capable of controlling a refractive index distribution by applying a voltage between the two substrates, and at least one of them And an alignment film that is provided in contact with the liquid crystal layer interface and regulates the liquid crystal molecule direction. In the image display device of the present invention, the optical path deflection driving means 7 that changes the voltage application state to the line electrode array in synchronization with the display driving means 5 is arranged in the first direction with respect to the two-dimensional arrangement direction of the pixels. The first optical path deflecting means (optical deflecting element) 6a capable of deflecting the optical path or moving the focal position along the pixel array direction, and deflecting the optical path or moving the focal position along the second pixel array direction. A second optical path deflecting means (optical deflecting element) 6b which can be used, and at least one of the substrates constituting the optical path deflecting means (optical deflecting element) is subjected to orientation processing, and the orientation processing direction of the orientation film is set to the first direction. The alignment processing direction for the liquid crystal line electrode in the optical path deflecting means (light deflecting element) 6a and the alignment processing direction for the liquid crystal line electrode in the second optical path deflecting means (light deflecting element) 6b are matched. It is (claim 1,8). In this case, if the alignment films are provided on both sides of the liquid crystal layer in each of the optical path deflecting means (optical deflecting elements) 6a and 6b and the orientation directions thereof are different, the first and second optical path deflecting means (light In the deflection elements 6a and 6b, it means that alignment films corresponding to both sides of the liquid crystal layer are provided, and the alignment treatment directions of the alignment films are set to be the same direction.
[0024]
As the material of the liquid crystal cell substrate, glass, plastic or the like can be used. As the material of the electrode, ITO, Cr, or the like can be used. The electrode layer is installed on the liquid crystal layer side. Moreover, when the board | substrate itself to be used has electroconductivity, a board | substrate can be utilized also as an electrode. On at least one substrate side, the line electrodes are formed in an array corresponding to the pixel pitch. Here, the pitch of the line electrode array is not limited to a one-to-one correspondence with the pixel pitch, but may be made to coincide with an integer multiple or a fraction of the pixel pitch in order to obtain a desired refractive index distribution. . Further, there may be a case where a plurality of line electrodes are set as one set and the set is made to correspond to the pixel pitch.
[0025]
The surface of the line electrode in contact with the liquid crystal layer is processed so that the liquid crystal molecules are aligned. For the alignment process, a normal alignment film such as polyimide used for TN liquid crystal, STN liquid crystal, etc. can be used. It is preferable to perform a rubbing treatment or the like. In addition, the use of photo-alignment as the alignment treatment prevents contamination of the alignment film and generation of static electricity, thus maintaining the cleanliness of the process and increasing the uniformity of the liquid crystal, resulting in a high-definition and clear image. More preferred (claims 7 and 8).
[0026]
The alignment processing direction matches the alignment processing direction for the liquid crystal line electrode in the first optical path deflection means (light deflection element) 6a and the alignment processing direction for the liquid crystal line electrode in the second optical path deflection means (light deflection element) 6b. By doing so, the operation of the liquid crystal with respect to the voltage is the same between the two devices, so that the liquid crystal driving method is simplified. Further, the first and second optical path deflecting means (optical deflecting elements) 6a and 6b may be the same device, so that the device creation time can be shortened and the cost can be reduced. Furthermore, it is preferable to make the alignment treatment direction substantially parallel to the line direction of the line electrode because a necessary refractive index distribution can be achieved at a lower voltage. This is because, as shown in FIG. 4, when a voltage is applied to the liquid crystal, the alignment of liquid crystal molecules that are not directly under the electrode becomes a twisted alignment, so that the refractive index change becomes strong (claims 2 and 8). ). In addition, when the alignment treatment direction is set to 45 ° or more and 135 ° or less from the line direction of the line electrode, the twist direction of the liquid crystal tends to be uniform, so that disclination is reduced and preferable for high-definition images. , 8).
[0027]
In addition, the alignment process is performed so that one side is homogeneous and the other side is vertical. By aligning the liquid crystal in a hybrid type, the twist direction of the liquid crystal tends to be uniform, resulting in less disclination and higher The resolution can be displayed (claims 6 and 8).
[0028]
A general nematic liquid crystal can be used as the liquid crystal material, but it is preferable that the birefringence Δn and the dielectric anisotropy Δε are large. In particular, the ordinary light refractive index of the liquid crystal material is preferably about 1.5 to 1.6 which is close to the refractive index of the glass substrate, and the extraordinary light refractive index is preferably as large as about 1.7 to 1.8. The thickness of the liquid crystal layer is set according to the thickness of the spacer member between the substrates, and is optimized so as to obtain a desired optical path deflection amount and response speed according to Δn and Δε. Further, by including a polymer in the liquid crystal layer, disclination is reduced, and further, the cell driving speed is increased, so that an image element that can cope with a smooth moving image can be obtained. This is because the contact area between the liquid crystal and the polymer is large and the alignment regulating force of the polymer with respect to the liquid crystal is strong, so that the response speed of the liquid crystal to the electric field can be greatly increased. As the liquid crystal, for example, photocurable polymer liquid crystals having a structure as shown in the chemical formulas (a) to (g) listed in FIG. 15 can be used, but normal polymers may be used, and the present invention is not limited to these. 4, 8).
[0029]
The operation of a single optical deflection element used in the optical path deflecting device 6 will be described below. Actually, the optical path deflecting device 6 is constituted by using two light deflecting elements described below, and the pixels are multiplied. FIG. 5 is an explanatory diagram of the configuration and operation of the liquid crystal light deflector, and FIG. 5A schematically shows the liquid crystal alignment state when the liquid crystal cell is not operating. In the example of FIG. 5A, the homogeneous alignment treatment is performed so that the liquid crystal molecules of the liquid crystal layer 13 are parallel along the substrates 11a and 11b in the absence of an electric field. This figure assumes an alignment process in which the major axis of the liquid crystal molecules is in the horizontal direction of the paper. Electrode lines 12b are formed in an array on the upper substrate 11b. In this example, two electrode lines having a wide interval are set as one set and correspond to one pixel. A portion where the distance between the electrodes is narrow corresponds to a boundary portion between the pixels. The lower electrode 12a is formed on the entire surface of the substrate 11a, but may be an array electrode symmetrical to the upper substrate 11b.
[0030]
FIG. 5B (operating state {circle around (1)}) shows a case where a voltage equal to or higher than the threshold is applied only to the electrode line colored and displayed in black. The electrode portion to which voltage is applied is oriented vertically by the electric field, and the electrode portion to which no voltage is applied remains horizontally oriented. Due to the distribution of the alignment direction due to the non-uniform electric field inside the liquid crystal cell, a refractive index distribution with respect to extraordinary light is generated. When linearly polarized light having a polarization plane parallel to the paper surface is incident, the effective refractive index decreases as the liquid crystal molecule long axis is oriented perpendicular to the substrate, as shown by the solid line in FIG. 6 (state (1)). Influenced by refractive index distribution. Polarized light that has entered the center of the pixel in state (1) is deflected to the right in the figure by the refraction effect due to the gradient of the refractive index.
[0031]
Next, when the electrode to which the voltage is applied is switched as shown in FIG. 5C (operation state (2)), the alignment state of the liquid crystal molecules also changes, and the refractive index distribution changes as shown by the broken line in FIG. . Polarized light that has entered the center of the pixel in state (2) is deflected to the left in the figure by the lens effect due to the gradient of the refractive index. The rate of change at this time is optimized by the physical properties of the liquid crystal material and the electric field. In the pixel shift method, since the subframe time is preferably 10 msec or less, the response time is required to be several msec or less. When nematic liquid crystal is used, high-speed response may be achieved by a two-frequency driving method or by mixing a polymer in the liquid crystal layer. When the two-frequency driving method is used, it is necessary to use a driving unit that can apply voltages having different driving frequencies to one electrode line. An apparent pixel multiplication effect can be obtained by switching the states {circle around (1)} and {circle around (2)} according to the driving timing of the sub-frame displayed on the liquid crystal light valve by any method.
[0032]
FIG. 7 shows a schematic diagram when light emitted from four pixels of the liquid crystal light valve enters the liquid crystal cell from the lower side of the drawing. For example, when the four pixels are in the state of (1), (3), (5), and (7) in the first sub-frame, if the liquid crystal cell is set to the operation state (1) in FIG. The light is deflected to the right. In the second sub-frame, when the four pixels are respectively switched to the states (2), (4), (6), and (8), and the liquid crystal cell is switched to the operation state (2) in FIG. Light from each pixel is deflected to the left. The light traveling obliquely in the liquid crystal cell is switched on the subframe from several tens of Hz to several hundreds of Hz, and apparently on the liquid crystal cell (1) (2) (3) (4) (5) (6) Eight pixels lined up with (7) and (8). Further, an optical element may be provided so that light emitted from the liquid crystal cell is parallel to the optical axis of the projection optical system.
[0033]
Next, FIG. 8 is an explanatory diagram of the configuration and operation of a liquid crystal light deflection element having a pixel reduction function. FIG. 8A schematically shows a liquid crystal alignment state when the liquid crystal cell is not operated. In the example of FIG. 8A, the electrode array 12b is formed on the substrate 11b on the upper side of the liquid crystal cell at the same pitch as the pixel pitch of the image display element. The width of each electrode is not particularly limited, but is set according to a desired electric field intensity distribution in the liquid crystal cell. In FIG. 8B (operating state {circle around (1)}), a voltage equal to or higher than the threshold value is alternately applied to the equally spaced electrodes. By applying this voltage, a refractive index distribution is generated in the liquid crystal layer 13 as described above. In this example, the distance between the electrodes to which the voltage is applied is larger than in FIG. 5, and the refractive index distribution is a convex lens having a relatively large pitch as shown by the solid line (state (1)) in FIG. In this case, one convex lens effect is given to two pixels of the image display element.
[0034]
Here, an explanatory view similar to FIG. 7 is shown in FIG. In this embodiment, the size of the incident-side pixel that enters the liquid crystal cell is set to be relatively large. For example, when the liquid crystal cell is in the state (1) in FIG. 8B, the state of (1), (3), (5), and (7) is displayed as the first subframe on four pixels, and the solid line in FIG. (1) and (3), (5) and (7) are reduced by the refractive index distribution. At this time, the pixel pitch is not constant like the output side pixel indicated by the solid line in the upper part of FIG. Next, when the electrode to which the voltage is applied is switched as shown in FIG. 8C (state (2)) in accordance with the display timing of the second subframe, the refractive index distribution is switched as shown by the broken line in FIG. . Here, when the state of (2), (4), (6), and (8) is displayed as the second subframe, the reduced pixel moves to the position indicated by the broken line at the top of FIG. By switching the subframes from several tens of Hz to several hundreds of Hz, it appears irregularly on the liquid crystal cell as (2) (1) (3) (4) (6) (5) (7) (8). It will be eight pixels. The subfield image data is corrected and displayed on the image display element so that a display image by such irregular pixel shift is formed as a normal image. In this configuration, with a simple electrode configuration, a single liquid crystal cell can achieve both a pixel reduction effect by condensing the liquid crystal lens and a pixel shift effect by switching the liquid crystal lens formation position. FIG. 11 is a schematic explanatory diagram of the configuration and operation when the liquid crystal is aligned in a hybrid type.
[0035]
In the configuration of FIG. 10, since the optical path is non-parallel light collected by the liquid crystal lens, the pixel size changes depending on the position from the emission side of the liquid crystal cell. For example, when an image is directly observed by placing a diffusion plate or the like on the emission side of the liquid crystal cell without using a projection optical system, the apparent pixel size changes if the positions of the liquid crystal cell and the diffusion plate are shifted. Even when the magnifying optical system is used, the light emitted from the liquid crystal cell is preferably parallel from the viewpoint of lens design. Therefore, in another configuration of the present invention, an optical element is provided so that light emitted from the liquid crystal cell is parallel to the optical axis of the projection optical system. When the characteristic of the liquid crystal lens array is a convex lens, this optical element is preferably a concave lens array that returns its optical path to parallel light. For example, FIG. 12 is an explanatory diagram showing an example in which a concave lens array is installed on the exit side of the liquid crystal cell of the optical path deflecting means. As shown in FIG. 12, the concave lens array is equal to the incident-side pixel pitch and the incident-side pixel position. It is preferable to install it at a position shifted by half a pixel.
[0036]
5 and 8, only the electrode 12b of the upper substrate 11b is formed in an array, but the electrodes 12a and 12b of the upper and lower substrates 11a and 11b are arranged in an array as in the configuration example of the liquid crystal light deflection element shown in FIG. You may form in a shape. Further, as in the configuration example of the liquid crystal light deflection element shown in FIG. 14, an auxiliary electrode array 14 as indicated by hatching is added between the electrodes 12 a and 12 b of the upper and lower substrates 11 a and 11 b, A voltage may be supplementarily applied to adjust the electric field distribution. In FIG. 14, one auxiliary electrode array 14 is added for each pixel. However, in order to finely adjust the refractive index distribution, a plurality of additional electrode arrays 14 may be added and the applied voltage may be changed stepwise. good.
[0037]
In the configuration so far, description has been given of performing pixel multiplication in one direction using one light deflection element (liquid crystal cell). However, in the present invention, two light deflection elements (liquid crystal cells) are used. The pixel multiplication is performed in the direction, and the alignment process direction of the liquid crystal cell as each optical path deflecting means is the same direction as the line electrode of each liquid crystal cell, so the liquid crystal alignment direction is shifted by 90 ° ing. Therefore, as shown in FIG. 3, the optical path deflecting device 6 needs to be provided with a polarization plane rotating means 6c between the two light deflecting elements (liquid crystal cells) 6a and 6b.
As the polarization plane rotating means 6c, a TN liquid crystal cell, a ferroelectric liquid crystal cell, a half-wave plate, a Faraday rotator, or the like can be used. In the case of a liquid crystal cell, since it is not necessary to perform switching by applying an electric field, an electrode may not be provided, but the alignment treatment and directionality of the substrate surface must be optimized. Further, the use of polymer liquid crystal as the liquid crystal eliminates the need for a substrate, so that the element can be made thin. Here, the polymer liquid crystal refers to a liquid crystal layer containing a polymer and a liquid crystal (claim 5).
[0038]
In addition, when there is wavelength dependency such as a half-wave plate, a half-wave plate for each color may be provided by separating the optical path for each color with a dichroic mirror or the like, and then synthesized again. Thus, by providing the optical path deflecting means (optical deflecting elements) 6a and 6b in two directions and the polarization plane rotating means 6c between them as the optical path deflecting device 6, the apparent number of pixels is multiplied in the two vertical and horizontal directions. High-definition images can be displayed.
[0039]
【Example】
Next, specific examples of the present invention will be described.
Example 1
An image display device having a configuration as shown in FIGS. An LED lamp was used as the light source 1 and a 0.9-inch diagonal XGA (1024 × 768 dots) polysilicon TFT liquid crystal panel was used as the image display element 4. The pixel pitch is about 18 μm both vertically and horizontally. As the first and second optical path deflecting means (optical deflecting elements) 6a and 6b of the optical path deflecting device 6, two liquid crystal microlenses aligned in the same direction with respect to the line electrode are prepared, and the alignment processing directions of each other are the same. Further, the polarization plane rotation means 6c is arranged so as to sandwich the deflection plane rotation element between two optical path deflection means (light deflection elements) 6a and 6b.
As a driving method of the optical path deflecting device 6, in order to perform pixel multiplication of 4 times in the vertical and horizontal directions of the image, it is necessary to switch the switching time at a high speed of 1 millisecond or less. The method was adopted.
Further, the two liquid crystal microlenses serving as the first and second optical path deflecting units 6a and 6b and the deflecting surface rotating element serving as the polarization plane rotating unit 6c were prepared as follows.
[0040]
LCD microlens:
An ITO deposited film on a thin glass substrate (3 cm × 4 cm, thickness 0.10 mm) was etched to form an ITO line having a width of 10 μm and a pitch of 18 μm. Comb electrodes were used so that the same voltage could be applied alternately to the ITO lines. AL3046-R31 (manufactured by JSR) was formed as an alignment film on the ITO side of the glass substrate by spin coating, and alignment treatment was performed with a roller rubbing apparatus. The rubbing direction was parallel to the line direction of the ITO electrode line. An empty cell was produced by sandwiching a 4 μm thick spacer between the two glass substrates and pasting them so that the ITO line positions of the upper and lower substrates coincided. A nematic liquid crystal was injected into the cell under normal pressure to produce a liquid crystal microlens.
[0041]
Deflection surface rotating element:
AL3046-R31 (manufactured by JSR) was formed as an alignment film on a thin glass substrate (3 cm × 4 cm, thickness 0.15 mm) by spin coating, and alignment processing was performed with a roller rubbing apparatus. An empty cell was fabricated by sandwiching a 3 μm thick spacer between the two glass substrates and pasting the upper and lower substrates so that the rubbing directions were orthogonal. A nematic liquid crystal (Merck, ZLI-2471) was injected into the cell under normal pressure to prepare a TN liquid crystal cell in which the orientation of liquid crystal molecules was twisted by 90 degrees.
[0042]
In the image display device of this embodiment, the first optical path deflecting unit 6a and the second optical path deflecting unit 6b of the optical path deflecting device 6 are aligned in the same direction. The optical path deflecting means 6b may be the same device, which is advantageous in terms of shortening device creation time and cost. In addition, since the alignment direction of the liquid crystal with respect to the line electrode is the same in the two cells, the dependency of the focal position of the liquid crystal microlens on the voltage is the same in the two cells, so that the driving voltage can be easily controlled. Further, the rubbing direction is parallel to the line direction of the ITO electrode, and a large change in refractive index was obtained at a relatively low voltage (claims 1, 2, 8).
[0043]
(Example 2)
(1) An image display device was produced in exactly the same manner as in the production of the liquid crystal microlens of Example 1, except that the rubbing direction was set to 40 ° from the line direction of the ITO electrode. This image display device is designated as sample 1.
(2) An image display device was produced in exactly the same manner as in the production of the liquid crystal microlens of Example 1, except that the rubbing direction was set to 45 ° from the line direction of the ITO electrode. This image display device is designated as sample 2.
(3) An image display device was produced in exactly the same manner as in the production of the liquid crystal microlens of Example 1, except that the rubbing direction was set to 75 ° from the line direction of the ITO electrode. This image display device is designated as sample 3.
(4) An image display device was produced in exactly the same manner as in the production of the liquid crystal microlens of Example 1, except that the rubbing direction was 90 ° from the line direction of the ITO electrode. This image display device is designated as sample 4.
[0044]
The images of the image display devices of Samples 1 to 4 were visually evaluated. The images of Samples 2, 3, and 4 whose rubbing direction is 45 ° or more from the ITO electrode line direction have less disclination because the liquid crystal alignment direction is easily fixed, and the rubbing direction is 45 degrees from the ITO electrode line direction. The contrast was better and easier to see than the small sample 1 (claims 3 and 8).
[0045]
(Example 3)
In the production of the liquid crystal microlens of Example 1, the same substrate was spin coated with a polyimide having a benzophenone skeleton as an alignment material, and photoalignment treatment was performed by irradiating polarized light at 330 nm for 5 minutes. A display device was created.
In this example, since the alignment process was performed without performing the rubbing process, the disclination due to impurities did not occur at all, and an extremely uniform liquid crystal alignment was performed, and a high-definition image was obtained (claims 7 and 8).
[0046]
Example 4
An image display device was produced in exactly the same manner except that the method for producing the liquid crystal microlens of Example 1 was changed. The drive method was a normal single frequency drive.
In the production of the liquid crystal microlens, a nematic liquid crystal (Merck, ZLI-2471) was prepared by adding a prepolymer (20% by weight) of a photocurable polymer having a liquid crystalline skeleton as a partial structure to the empty cell produced in Example 1. ) And injected into the cell by capillary method. As a prepolymer of a photocurable polymer having a liquid crystalline skeleton as a partial structure, a mixture of substances represented by chemical formulas (a), (d), and (g) shown in FIG. 15 is used, and the ratio of each is a: d: g = 48: 48: 4. In addition, 1 wt% of a photopolymerization initiator (IRG-651, Ciba Geigy) was mixed with the polymerizable liquid crystal. This prepolymer is 20 mW / cm ² UV was irradiated for 1 minute at room temperature to polymerize.
[0047]
In this embodiment, the rubbing direction is 0 ° from the line direction of the ITO electrode, and a large refractive index change can be obtained at a relatively low voltage, but disclination occurs when only the liquid crystal is used. It is easy to do. However, by mixing the polymer, the regulating force acts in the alignment direction of the liquid crystal and the occurrence of disclination is suppressed, and a high quality image is obtained. In addition, the contact area between the liquid crystal and the polymer is large, and the alignment control force of the polymer with respect to the liquid crystal is strong. Therefore, the response speed of the liquid crystal to the electric field can be greatly increased, and no dual frequency drive is required. With this driving, a sufficient cell response speed was obtained and image display was possible (claims 4 and 8).
[0048]
(Example 5)
An image display apparatus was produced in exactly the same manner except that the production method of the deflecting surface rotating element of Example 1 was changed.
The deflection surface rotating element uses a prepolymer of a photo-curing polymer having a liquid crystalline skeleton as a partial structure as a liquid crystal (a mixture of substances of chemical formulas (a), (d), and (g) in FIG. 15). The ratio was a: d: g = 48: 48: 4. In addition, 1 wt% of a photopolymerization initiator (IRG-651, Ciba Geigy) was mixed with the polymerizable liquid crystal. The prepolymer is 20 mW / cm ² UV was irradiated for 5 minutes at room temperature to polymerize. After the liquid crystal layer was cured, the substrate was removed from the polymer to obtain a deflecting surface rotating element.
In this embodiment, since the substrate can be removed by polymerizing the liquid crystal, the thickness of the device can be reduced (claims 5 and 8).
[0049]
(Example 6)
An image display device was produced in exactly the same manner except that the method for producing the liquid crystal microlens of Example 1 was changed.
AL3046-R31 (manufactured by JSR) was formed as an alignment film on the ITO side of one glass substrate of the liquid crystal microlens by spin coating, and alignment treatment was performed with a roller rubbing apparatus. The rubbing direction was 0 ° from the line direction of the ITO electrode, and vertical alignment treatment was performed using JALS-2021-R2 (manufactured by JSR) on the ITO side of the counter electrode. An empty cell was produced by sandwiching a 4 μm thick spacer between the two glass substrates and pasting them so that the ITO line positions of the upper and lower substrates coincided. A nematic liquid crystal was injected into the cell under normal pressure to produce a liquid crystal microlens.
In this embodiment, since the liquid crystal is oriented in a hybrid type, the twist direction of the liquid crystal when the voltage is applied tends to be uniform, and there is little disclination and a high resolution display can be achieved.
[0050]
【The invention's effect】
As described above, in the optical path deflecting device according to claim 1, the pair of optical path deflecting means (the first optical path deflecting means (optical deflecting element) and the second optical path deflecting means (optical deflecting element) from the light source side). Are aligned in the same direction, the first optical path deflecting means (optical deflecting element) and the second optical path deflecting means (optical deflecting element) may be the same device, which shortens the device creation time. Further, since the alignment direction of the liquid crystal with respect to the line electrode is the same in the two cells, the voltage application in the two cells can be performed in substantially the same manner.
[0051]
In the optical path deflecting device according to the second aspect, in addition to the configuration and effect of the first aspect, the change in the refractive index when an electric field is applied is large, so that the operation can be performed with a small voltage.
In the optical path deflecting device according to the third aspect, in addition to the configuration and effect of the first aspect, the liquid crystal alignment direction is easily determined to be constant, so that disclination hardly occurs, and thus a high-definition image can be obtained. Further, when it is smaller than 45 ° from the line direction or larger than 135 °, disclination is likely to occur.
In the optical path deflecting device according to claim 4, in addition to the configuration and effect of claim 1, a high-speed response is possible, and since it is surrounded by a polymer, disclination is unlikely to occur. Is obtained.
[0052]
In the optical path deflecting device according to the fifth aspect, in addition to the configuration and effect of the first aspect, the device can be made thinner.
In the optical path deflecting device according to the sixth aspect, in addition to the configuration and effect of the first aspect, disclination hardly occurs, so that a high-definition image can be obtained.
In the optical path deflecting device according to the seventh aspect, in addition to the configuration and effect of the first aspect, the alignment film is not contaminated or static electricity is generated, so that the cleanliness of the process can be maintained and the uniformity of the liquid crystal is increased. High-definition and beautiful images can be obtained.
[0053]
In the image display device according to claim 8, by providing the optical path deflecting device according to any one of claims 1 to 7 as the optical path deflecting device, the effect of any one of claims 1 to 7 is obtained. High-definition image by apparent pixel multiplication without lowering light utilization efficiency without optical mechanical shift mechanism and optical path shift by electro-optic effect with relatively simple electrode configuration And the display quality can be improved. Moreover, it can be set as a simple structure as an image display system.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of an image display device according to an embodiment of the present invention.
FIG. 2 is a display example of pixels of the image display device shown in FIG. 1, and shows an example in which the apparent number of pixels is four times that of the original pixels.
3 is a diagram illustrating an arrangement and a configuration example of an optical path deflecting device for bi-directional multiplication in the image display apparatus illustrated in FIG. 1;
FIG. 4 is a diagram showing an example of a liquid crystal cell used for an optical deflection element of an optical path deflecting device, and is an explanatory diagram of a liquid crystal alignment state when alignment processing is performed in a direction 90 ° to the normal direction of a line electrode.
FIG. 5 is a diagram illustrating an example of a liquid crystal light deflecting element used in an optical path deflecting device, and is an explanatory diagram of the configuration and operation of the liquid crystal light deflecting element.
6 is a diagram showing a change in the refractive index distribution in the liquid crystal cell of the liquid crystal light deflecting element shown in FIG.
7 is an explanatory diagram of pixel position shift by the liquid crystal cell of the liquid crystal light deflection element shown in FIG. 5; FIG.
FIG. 8 is a diagram showing another example of a liquid crystal light deflection element used in an optical path deflecting device, and is an explanatory diagram of the configuration and operation of a liquid crystal light deflection element having a pixel reduction function.
9 is a diagram showing a change in the refractive index distribution in the liquid crystal cell in the liquid crystal light deflection element shown in FIG.
10 is an explanatory diagram of a pixel reduction effect and a pixel shift effect by a liquid crystal lens of the liquid crystal light deflection element shown in FIG.
FIG. 11 is a diagram showing still another example of the liquid crystal light deflecting element used in the optical path deflecting device, and is an explanatory diagram of the configuration and operation of the liquid crystal when hybrid alignment is performed.
FIG. 12 is an explanatory diagram of the operation when a concave lens array is installed as a beam collimating unit in the optical path deflecting unit.
FIG. 13 is a configuration explanatory view showing still another example of a liquid crystal light deflecting element used in an optical path deflecting device.
FIG. 14 is a configuration explanatory view showing still another example of a liquid crystal light deflecting element used in an optical path deflecting device.
FIG. 15 is a diagram showing a list of chemical formulas representing structures of photocurable polymer liquid crystals.
[Explanation of symbols]
1: Light source
2: Light source driving means
3: Lighting device
4: Image display element
5: Display drive means
6: Optical path deflecting device
6a: First optical path deflecting means (optical deflecting element)
6b: Second optical path deflecting means (optical deflecting element)
6c: deflection surface rotating means
7: Optical path deflection drive means
8: Image display control circuit
9: Projection lens
10: Screen
11a, 11b: substrate
12a: Electrode (or electrode array)
12b: Electrode array
13: Liquid crystal layer
14: Auxiliary electrode array

Claims (8)

Used in the image display apparatus, the optical path deflecting having an optical path deflecting means consisting of a light deflector for deflecting the optical path of the light emitted from each pixel was set vignetting corresponds to the two-dimensional orientation of the pixel of the image display device A device,
The first optical path deflecting means capable of moving the polarization or focal position of the optical path along the first pixel arrangement direction with respect to the two-dimensional orientation direction of the pixels and the optical path along the second pixel arrangement direction. A pair of optical path deflecting means comprising a second optical path deflecting means capable of deflecting or moving the focal position;
A polarization plane rotating means provided between the pair of optical path deflecting means,
The light deflection elements of the pair of optical path deflecting means are respectively provided between two substrates, a line electrode array formed on at least one substrate corresponding to the pixel pitch, and a voltage applied between the two substrates. And a liquid crystal layer capable of controlling the refractive index distribution, and an alignment film that is provided in contact with at least one liquid crystal layer interface and regulates a liquid crystal molecular direction. The alignment of the alignment film with respect to the line electrode in each light deflection element An optical path deflecting device having the same processing direction. The optical path deflecting device according to claim 1,
An optical path deflecting device, wherein the alignment processing direction of the alignment film of the light deflection element is substantially parallel to the line direction of the line electrode. The optical path deflecting device according to claim 1,
An optical path deflecting device characterized in that an orientation processing direction of an orientation film of the light deflection element is set to 45 ° or more and 135 ° or less from a line direction of a line electrode. The optical path deflecting device according to claim 1,
An optical path deflecting device comprising a polymer in a liquid crystal layer of the light deflecting element. The optical path deflecting device according to claim 1,
As the polarization plane rotating means, the optical path deflecting characterized in that a polarization plane rotating means consisting of a polymer liquid crystal to rotate to the second pixel array direction of the polarization plane of the linearly polarized light from the first pixel array direction apparatus. The optical path deflecting device according to claim 1,
An optical path deflecting device, wherein one substrate of the light deflecting element is subjected to a vertical alignment process. The optical path deflecting device according to claim 1,
The optical path deflecting device according to claim 1, wherein the alignment film of the light deflection element is capable of producing an alignment regulating force by light irradiation. 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 and an illumination device that illuminate the image display element, and an image pattern displayed on the image display element out of the optical device, and a display driving means for forming a plurality of sub-fields obtained by dividing an image field temporally, from each pixel was set vignetting corresponds to the two-dimensional orientation of the pixel of the image display device An optical path deflecting device having an optical path deflecting unit composed of an optical deflecting element that deflects the optical path of the incident light, and displaying an image pattern in which the display position is shifted according to the deflection state of the optical path for each subfield, In an image display device that displays the image by multiplying the apparent number of pixels of the image display element,
An image display device comprising the optical path deflecting device according to claim 1 as the optical path deflecting device.

Images