JP2006058588A - Optical device, optical apparatus, display apparatus and stereoscopic image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical device capable of temporally switching a polarization state and obtaining polarized light which has little wavelength dependency and has excellent polarization purity, to provide an optical apparatus provided with the optical device, and to provide a display apparatus capable of performing pixel shift simply and precisely and realizing high definition. <P>SOLUTION: The optical device has a rotation axis and is provided with a surface which is parallel to the rotation axis and has transparency, at least a part of the surface is formed with a optical anisotropic medium and the polarization state of light rays passing through the surface accompanying the rotation are temporally switched and emitted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical device, an optical device, a display device, and a stereoscopic image display device, and more particularly to a projection display device, particularly a projection display device using a digital micromirror device (hereinafter abbreviated as DMD). The present invention relates to a technology for improving definition.

  First, terms used in this specification are defined as follows. First, the “pixel shift technology” 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 displayed on the image display element. Using a pixel shift element having an optical member for observing a pattern and a light deflecting means for deflecting an optical path between the image display element and the optical member for each of a plurality of subfields obtained by dividing the image field in time, The technique refers to a technique in which the apparent number of pixels of the image display element is multiplied and displayed by displaying an image pattern in which the display position is shifted in accordance with the deflection of the optical path for each subfield by the light deflecting means. The “polarization direction of linearly polarized light” refers to the vibration direction of the electric field vector in linearly polarized light.

  The conventional pixel shift technique is a method of oscillating an optical element of an image display element or a projection optical system, or using a light polarization element such as a liquid crystal. However, the former oscillating method involves mechanical vibration. Therefore, the durability of the image display element and the optical element is impaired, and problems such as heat generation and noise occur. The latter liquid crystal method is excellent in terms of mechanical reliability. However, when the liquid crystal alignment control is insufficient, the image contrast is deteriorated, and the cost for elementization is high.

  On the other hand, projection display devices using DMD have been developed. The projection display device using the DMD includes a device that is colorized by a field sequential color system using a color wheel. This device will be described below with reference to the drawings. FIG. 21 is a schematic diagram showing a configuration of a conventional projection display device. In the figure, a light beam emitted from a lamp unit 1 having a white light source such as a high-pressure mercury lamp or a xenon lamp has a configuration as shown in FIG. R, green (G), and blue (B). The light emitted from the color wheel 2 is guided by the lens 3 to the rod integrator 4 for improving the uniformity of the light intensity, and irradiated to the DMD 6 through the condenser lens 5. The DMD 6 is an image display element in which pixels made of micromirrors are two-dimensionally arranged. By switching the mirror angle for each pixel according to the image signal corresponding to each pixel, and controlling the length of time reflected in the direction of the projection lens 7 and the length of time reflected in the direction other than the projection lens, A predetermined brightness is obtained.

  Here, a technique similar to pixel shift is disclosed in Patent Document 1 as a technique for achieving high definition and smoothing of the DMD. Patent Document 2 discloses a technique using a rotating prism in a display device. This rotating prism is used to move multiple color light bands (bands of light from the illumination system) within the image display element for the purpose of improving light utilization efficiency when performing color display with a single-plate image display element. It is used.

Moreover, as a prior art regarding a three-dimensional image display system, it is disclosed by patent document 3, patent document 4, etc., for example. Patent Document 3 discloses a three-dimensional display device in which light source light is separated into S and P polarized light by a polarization beam splitter, and these lights are incident on right-eye and left-eye liquid crystal panels and projected onto a screen by a projection lens. Has been proposed. Further, Patent Document 4 discloses a stereoscopic display in which a polarization switching unit for switching the polarization direction in a time-division manner is disposed in front of the lenticular screen, and a polarizing plate array in which orthogonal polarization filters are provided in stripes as the lenticular screen. A device has been proposed.
Japanese Patent Laid-Open No. 2004-070365 Patent No. 3,352,100 Japanese Patent Laid-Open No. 08-068963 JP 09-159971 A

  However, since Patent Document 1 is accompanied by mechanical vibration, the durability of the image display element and the optical element is impaired, and problems such as heat generation and noise occur. In addition, the above-mentioned Patent Document 2 is effective for colorization, but has not yet switched polarization, so that it is not possible to achieve high definition of DMD. Furthermore, since Patent Document 3 prepares two sets of image display elements and projection lenses corresponding to the left eye and the right eye, there is a problem that the apparatus becomes large. Further, according to Patent Document 4, there are problems of image deterioration due to passing through the polarization switching means, and light utilization efficiency reduction due to halving the actual light amount by the polarizing plate array.

  The present invention is intended to solve these problems, and an optical device, an optical apparatus, and a pixel shift capable of switching a polarization state with time and obtaining a polarized light with less wavelength dependency and excellent polarization purity. It is an object of the present invention to provide a display device that can be easily performed with high accuracy and can achieve high definition, and a stereoscopic image display device that displays a small and favorable stereoscopic image.

  In order to solve the above problems, an optical device of the present invention includes a surface having a rotation axis, parallel to the rotation axis and having a light transmitting property, and at least a part of the surface is optically anisotropic. It is characterized by the fact that it is formed by a medium and is emitted by switching the polarization state of the light beam passing through the surface with rotation. Therefore, compared with conventional polarization conversion using liquid crystal or the like, polarized light having less wavelength dependency and excellent polarization purity can be obtained. By combining with a birefringent plate, the traveling direction of light can be switched periodically, the projection display can be made high definition, and pixel shift can be easily performed with high accuracy.

  The optical device of the present invention is a polygonal column having a rotation axis, a surface parallel to the rotation axis and having a light transmitting property, and at least a part of the side surface is made of an optically anisotropic medium. Is formed. Therefore, by setting the surface on which the optically anisotropic medium is formed as a flat surface, the polarization state within a predetermined unit time can be homogenized in the polarization state that changes over time. It is easy to design and a multilayer film structure can be easily adopted.

  Furthermore, the optical device of the present invention is a cylinder having a rotation axis, and at least a part of the side surface is formed of an optically anisotropic medium. Therefore, the temporal change in the optical path length can be eliminated in the polarization state that changes over time.

  Further, the optically anisotropic medium is a polarizer formed at a predetermined interval along the rotation direction of the optical device, so that non-polarized light is incident and linearly polarized light having different states in time is obtained. Can be simplified and downsized.

  Further, the optical system can be simplified and miniaturized by arranging a plurality of polarizers having different polarization directions of the emitted light along the rotation direction of the optical device.

  In addition, by arranging two polarizers whose polarization directions are orthogonal to each other along the rotation direction of the optical device, emission light in two states whose polarization directions are orthogonal can be obtained. Pixel shift in the case of using a mirror device can be easily performed with high accuracy.

  Further, the optically anisotropic medium is a half-wavelength element formed at a predetermined interval along the rotation direction of the optical device, so that when the incident light is linearly polarized light, the linearly polarized light whose state is temporally different Can be emitted.

  In addition, an optically isotropic medium that matches the optical path length when transmitting through the half-wavelength element is provided in the gap between the half-wavelength elements along the rotation direction of the optical device. Therefore, aberration due to optical path length mismatch can be prevented, and temporal changes in light distribution can be eliminated when used in an illumination system for a digital micromirror device.

  Furthermore, an optically isotropic medium having a transmittance equal to the transmittance at the time of transmission through the half-wavelength element is provided in the gap between the half-wavelength elements along the rotation direction of the optical device. Therefore, a temporal change in transmittance can be prevented, and a temporal change in the amount of light can be eliminated when used in an illumination system for a digital micromirror device.

  Further, since the optical anisotropic medium is a quarter wavelength element formed at a predetermined interval along the rotation direction of the optical device, the wavelength dispersion of the emitted light can be easily aligned.

  Furthermore, by arranging alternately the quarter wavelength elements having different phase directions along the rotation direction of the optical device, when the incident light is circularly polarized light, the orthogonal linearly polarized light can be switched in time and emitted. .

  In addition, a color filter is provided along the rotation direction of the optical device, and at least one color filter also serves as an optically anisotropic medium, so that the color can be switched over time as well as the polarization state. I can plan.

  Further, the color filter includes at least three colors of red (R), green (G), and blue (B), and emits polarized light orthogonal to each color in at least six polarization states during one rotation. Therefore, while obtaining three colors of light for display, it is possible to switch the polarization state for higher definition, and pixel shift technology shifts the pixel to two positions during one rotation of the optical device and doubles it. High definition can be achieved.

  In addition, the color break can be prevented by setting the colors of the adjacent polarization states in the six polarization states to different colors.

  Further, the color filter is composed of red (R), green (G), blue (B), and green (G), and each green (G) emits polarized light orthogonal to each other during one rotation. The polarization state for high definition can be switched while obtaining the outgoing light, and since it is only the polarization change of green, there are four state changes and the time to take the polarization state is 1.5 times longer It is possible to increase the light utilization efficiency when used in a projection display.

  In addition, red (R) and blue (B) outgoing light is set to a polarization state in which linearly polarized light parallel to the polarization direction of any green (G) is emitted, so that red and blue light rays other than green are emitted. Can be linearly polarized, and the pixel position can be prevented from forming a double image. Therefore, it is possible to provide an image display device with excellent resolution performance when displaying thin lines.

  Further, since the red (R) and blue (B) color filter transmittances are higher than the transmittance of any green (G) color filter, it passes through the green color filter twice, resulting in twice the amount of light. However, it is possible to increase the transmittance of the red and blue color filters and to adjust the color balance, thereby obtaining a projection image with high definition and excellent color reproduction performance.

  In addition, the width in the rotation direction of the red (R) and blue (B) color filters is wider than the width of any green (G) color filter. However, it is possible to adjust the color balance by widening the width of the red and blue color filters and making the light passage time longer than green, thus obtaining a projection image with high definition and excellent color reproduction performance. Can do.

  Furthermore, an optical apparatus according to another invention includes at least one of the above-described optical devices, allows light rays to enter the optical device from a predetermined direction, and temporally switches light beams having a polarization state different from the polarization state of incident light. It is characterized by exiting. Therefore, it is possible to provide an optical device that can switch the polarization state with extremely high accuracy.

  In addition, since the optical axis of the light beam transmitted through the optical anisotropic medium formed in the optical device is perpendicular to the rotation axis, a good polarization state of the emitted light can be obtained. When applied to pixel shift, it is possible to suppress a double image at each pixel shift position and obtain a high-quality image.

  Furthermore, a straight line including the optical axis of the light beam passing through the optically anisotropic medium passes through the rotation axis of the optical device, so that a good polarization state of the emitted light can be obtained and applied to the pixel shift of the projection apparatus. In this case, a double image at each pixel shift position can be suppressed and a high quality image can be obtained.

  In addition, the light beam incident on the optically anisotropic medium is convergent light, and the convergence point coincides with the portion where the optically anisotropic medium is formed. The diameter can be reduced and the apparatus can be downsized.

  Furthermore, by passing once through the surface on which the optically anisotropic medium is formed while passing through the optical device, it is possible to prevent the polarization state from deteriorating due to multiple passes.

  In addition, since the fixed mirror is provided inside the optical device and on the optical path of the light beam that passes through the optical anisotropic medium, the optical device can be realized with a very simple configuration.

  Furthermore, since the traveling direction of the light beam in the optical device is a direction from the fixed mirror toward the optically anisotropic medium, it is possible to avoid polarization disturbance caused by providing a reflecting surface after switching the polarization state. Generation of multiple images can be suppressed.

  Further, since the optically anisotropic medium is a circularly polarized light beam incident on the optical device that is a quarter wavelength element formed at a predetermined interval along the rotation direction of the optical device, the wavelength dispersion of the emitted light, etc. Can be easily arranged.

  Furthermore, while passing through the optical device, it passes through the surface on which the optically anisotropic medium is formed twice, so that the optical axis is on a common straight line before and after the light beam passes through the optical device. Since it can be configured, optical design and adjustment become easy.

  In addition, the optical anisotropic medium is a polarizer formed at predetermined intervals along the rotation direction of the optical device. Easy to do.

  Furthermore, since the optically anisotropic medium is a linearly polarized light beam incident on an optical device that is a half-wavelength element formed at predetermined intervals along the rotation direction of the optical device, it is polarized from non-polarized light in the previous stage. The light utilization efficiency can be improved when linearly polarized light is obtained by the conversion technique and is incident on the optical device.

  In addition, since the polarization state of the outgoing light that changes over time is two linearly polarized lights that are orthogonal to each other, when applied to the pixel shift of the projection device, a double image at each pixel shift position is suppressed and a high-quality image is obtained. Obtainable.

  Furthermore, a display device as another invention is characterized by comprising the optical device. Therefore, compared to the pixel shift method in which the optical elements of the image display element and the projection optical system are swung or the light polarization element such as liquid crystal is used, the light is controlled on the illumination side. A good pixel shift can be performed without applying and without increasing the back focus of the projection optical system.

  In addition, since the digital micromirror device is provided, the pixel shift can be easily performed with high accuracy.

  Furthermore, by installing the optical device on the illumination light side of the digital micromirror device, the back focus can be shortened, and when it is arranged on the projection optical system side, image distortion caused by the flatness of the mirror can be avoided.

  In addition, the polarization direction of the light emitted from the optical device included in the optical apparatus and incident on the digital micromirror device while switching the polarization direction in time is perpendicular or parallel to the diagonal direction of the pixels in the digital micromirror device. By being in the direction, it is possible to shift the pixel to a position for interpolation between four adjacent pixels, and high definition can be achieved efficiently.

  Furthermore, the polarization direction of the light beam that exits the optical device included in the optical apparatus and enters the digital micromirror device while switching the polarization direction in time is perpendicular or parallel to the side direction of the pixels in the digital micromirror device. Direction. Therefore, it is possible to shift the pixel to the position for interpolating between the scanning lines in the vertical and horizontal directions, and high definition can be achieved efficiently.

  In addition, a projection type that can periodically switch the traveling direction of light by installing a birefringent element having an optical axis in a direction inclined with respect to the optical axis on the light output side from the digital micromirror device. Can be provided.

  Furthermore, the polarization direction of the light beam that is emitted from the optical device included in the optical apparatus and enters the birefringent element while switching the polarization direction with respect to time is perpendicular to the plane including the optical axis and the optical axis of the birefringent element. Alternatively, it is possible to provide a projection-type display device that can switch the traveling direction of light periodically without generating a double image due to the parallel direction.

  In addition, when the polarization direction of the light beam incident on the birefringence element is parallel to the plane including the optical axis and the optical axis of the birefringence element, the amount of polarization due to the birefringence of the light beam is a digital micromirror device in the polarization direction. Because of the half pitch of the pixel array in, a high-definition image can be obtained by shifting to a position corresponding to the half pitch of the pixel array.

  Furthermore, since the display switching timing of the digital micromirror device and the polarization state switching timing of the optical device included in the optical device are synchronized, a double image due to timing failure can be prevented, and a good high-definition image can be obtained. It is done.

  In another aspect of the present invention, there is provided a stereoscopic image display device for the left and right eyes of an observer, comprising the above display device and a polarizing filter having a transmission axis that matches the polarization direction of each linearly polarized light emitted from the display device. It has a feature in that it has a corresponding polarization selection means. Therefore, polarized light with less wavelength dependency and excellent polarization purity can be obtained, and a high-quality stereoscopic image can be formed. Further, by providing an optical device in the illumination system, an increase in the back focus of the projection lens can be avoided and the apparatus can be miniaturized. The cost can be reduced along with the downsizing of the apparatus, and the rear projection type can be reduced in thickness and the number of optical components in the projection system can be reduced to improve the image quality. Furthermore, since a new component for forming a stereoscopic image is not required, the projection optical system can be easily designed.

  Furthermore, since the polarization selection means is a spectacle type and the polarizing filter is provided on the spectacles corresponding to each eye, a good stereoscopic image can be observed regardless of the position of the observer.

  Further, in the time zone in which the digital micromirror device is displaying an image for the right eye or the left eye, it is parallel to the transmission axis of the polarizing filter provided at the position of the right eye or the left eye of the spectacle-type polarization selection means. A good stereoscopic image can be formed by controlling the polarization direction so that the linearly polarized light reaches the observer.

  According to the optical device of the present invention, the polarization state can be switched with time, and polarized light with less wavelength dependency and excellent polarization purity can be obtained.

  FIG. 1 is a perspective view showing a configuration of an optical device according to a first embodiment of the present invention. The optical device 10 according to the present embodiment shown in the figure is a quadrangular prism having a rotation axis 11 and includes four surfaces 12 that are parallel to the rotation axis 11 and have translucency. At least a part is formed of an optically anisotropic medium, and the polarization state of the light beam passing through the surface 12 is switched with time and emitted with rotation.

  FIG. 2 is a perspective view showing the configuration of another example of the optical device according to the first embodiment of the present invention. The optical device 20 shown in FIG. 1 has a hexagonal column having a rotation axis 21 and includes six surfaces 22 that are parallel to the rotation axis 21 and have translucency. At least a part of the surface 22 is optical. It is formed by a magnetically anisotropic medium, and changes the polarization state of the light beam passing through the surface 22 with rotation, and emits it while switching.

  The optical device according to the present embodiment is not limited to the quadrangular column as shown in FIG. 1 or the hexagonal column as shown in FIG. The rotation axes 11 and 21 are selected to coincide with the rotational symmetry axis. The optically anisotropic medium is formed on the side surface of the polygonal column.

  FIG. 3 is a perspective view showing the configuration of the optical device according to the second embodiment of the present invention. The optical device 30 according to this embodiment shown in the figure is a cylinder having a rotation axis 31, and an optically anisotropic medium in the optical device 30 is formed on a side surface 32 of the cylinder. Further, the optical device 30 can be formed by, for example, avoiding a portion through which light passes, forming a frame from metal, resin, or the like, and bonding an edge of an optical anisotropic medium to the frame. In addition, the substrate is molded from glass, transparent resin, or the like, or a transparent and optically isotropic material, and an optically anisotropic medium is printed thereon or formed by vacuum film formation or the like. Also good.

  As described above, the optically anisotropic medium in the first and second embodiments is a linear polarizer that transmits only polarized light in a certain predetermined direction and shields light beams in other directions, and the polarization direction. Therefore, a phase shifter that makes a difference in the propagation speed of the light beam is used. In particular, as the phase shifter, a ½ wavelength element that gives a phase difference corresponding to a half wavelength between incident light and outgoing light, and a ¼ wavelength element that gives a phase difference equivalent to ¼ wavelength are selected. Each anisotropic medium preferably has a uniform characteristic in the entire visible light range, but is preferably one that functions well in the green range. As the material, those generally used as optical parts can be used. For example, a resin such as polyvinyl alcohol, polypropylene, polyethylene, polycarbonate, polyarylate, polysulfone, polyolefin, etc. is stretched to give optical anisotropy. Can be used.

  Further, in the first embodiment shown in FIGS. 1 and 2, it is possible to control the polarization direction for each surface by arranging linear polarizers in different directions for each surface. In the second embodiment shown in FIG. 3, the polarization direction can be controlled by forming linearly polarized light at predetermined intervals in the rotational direction on the side surface 32. Furthermore, in the pixel shift using DMD, it is necessary to switch orthogonally polarized light in terms of time. For this reason, as the polarization direction, two polarizers in which the polarization direction of outgoing light is orthogonally arranged are alternately arranged. This structure is useful. In any case, it is desirable that the wavelength characteristics of the light beams emitted from the polarizer are uniform, and it is preferable to arrange the same type of polarizer in a state where it is inclined by 90 degrees. As shown in FIG. 4, it is possible to prepare a configuration in which a linear polarizer is formed on the surface 41 of a transparent disk, and it is possible to switch the polarization state temporally by rotating the disk 40, but the light passing through A linearly polarized light in a uniform direction cannot be obtained in the entire region 42.

  FIG. 5 is a perspective view showing the configuration of the optical apparatus according to the first embodiment of another invention. The optical apparatus 50 according to the present embodiment shown in the figure is configured by installing a fixed mirror 51 on the optical path of a light beam that passes through an optically anisotropic medium inside the optical device 30 shown in FIG. Yes. The light beam 52 passes only once through the surface 32 provided with the optically anisotropic medium. This optically anisotropic medium is composed of two orthogonal polarizers. When incident light is non-polarized light, the orthogonally polarized light is emitted while being temporally switched as shown in FIG. In this case, directional linearly polarized light that is uniform over the entire region through which light passes can be obtained as compared with FIG. In FIG. 5, the traveling direction of the light beam is set in the direction from the fixed mirror 51 toward the optically anisotropic medium. By setting in this way, for example, as shown in FIG. 6, the light beam is reflected on the optical path to the DMD. There is no need to provide a surface, and polarization disturbance due to the surface accuracy of the reflecting surface can be avoided. In FIG. 6, the light emitted from the lamp unit 61 is once condensed on the surface of the color wheel 62, and the color is temporally divided into RGB and emitted. The light emitted from the color wheel 62 is guided to the rod integrator 64 by the lens 63 and the light quantity distribution is homogenized. The light emitted from the rod integrator 64 is guided to the optical device 50 of FIG. 5 as described above. The polarization state is changed at the timing when the polarization direction is switched by the optical device 50 for each period of the color wheel 62. Thereafter, the DMD 66 is illuminated through the condenser lens 65. The DMD 66 performs modulation in the traveling direction for each pixel. When a light beam traveling in the direction of the projection lens 68 passes through the birefringent element 67, it is possible to control a light beam that travels straight and a light beam that is deflected by a difference in polarization state, which will be described later. Is obtained. Finally, a color image is formed on a screen (not shown) via the projection lens 68. In FIG. 6, the optical device 50 can be disposed on the projection side of the DMD 66, but the back focus of the projection lens 68 becomes long, and therefore, it is more preferably disposed on the illumination side.

  FIG. 7 is a perspective view showing a configuration of an optical apparatus according to a second embodiment of another invention. The optical device 70 shown in FIG. 3 includes a color filter 73 along the rotation direction of the optical device 30 shown in FIG. 3, and at least one color filter 73 also serves as an optically anisotropic medium. . In particular, here is an example of a configuration in which non-polarized light is incident and both color and polarization direction are switched over time. By using this optical device 30, when the color wheel 62 is removed from the optical system of FIG. 6, that is, the configuration shown in FIG. 8, the same function can be obtained, and the apparatus can be reduced in size and cost. Can be planned. In FIG. 8, a relay lens 81 is provided after the rod integrator 64, and the optical anisotropic medium portion and the emission portion of the rod integrator 64 are in a conjugate relationship, which is the convergence point of the light beam.

  Here, in FIGS. 6 and 8, it is desirable that the optical axis of the light beam transmitted through the optically anisotropic medium is perpendicular to the rotation axis in order to obtain a good polarization state. It is even more desirable that the straight line including the optical axis of the light beam passing through the medium passes through the rotation axis of the optical device. Further, it is preferable that the light beam incident on the optically anisotropic medium is convergent light, and the convergent point coincides with the optically anisotropic medium part.

  Next, consider the following two pixel shift modes. One is a case where each pixel takes two positions (SP1, SP2) as shift positions, and brightness corresponding to each color position of RGB is obtained at each position. In this case, as shown in FIGS. 9A and 9C, one image field is divided into six subfields, and six polarization / color states are set for each subfield. In order to achieve this mode, the color filter 73 provided along the rotation direction with respect to the optical device 30 in the optical apparatus 70 shown in FIG. 7 includes at least three of red (R) green (G) blue (B). What is necessary is just to comprise so that the polarization | polarized-light orthogonal to each color may be radiate | emitted in one rotation including a color. In this case, the colors of the adjacent subfields are preferably set to different colors in order to suppress a color break, that is, a phenomenon in which a human feels a temporal color change and feels uncomfortable. The other pixel shift mode is a case where each pixel takes two positions as shift positions, each color of RGB is displayed at one position, and only green is displayed at the other position. In this case, as shown in FIGS. 9B and 9D, one image field is divided into four subfields. For the optical device 30 of the optical apparatus 70 shown in FIG. 7, the color filter 73 provided along the rotation direction is made of red (R), green (G), blue (B), and green (G). Each green (G) may be configured to emit orthogonally polarized light.

  FIG. 10 is a side view of the optical device of FIG. Each color has a polarizer in the direction shown in the figure. In this case, it is desirable to set red (R) and blue (B) to a polarization state that coincides with one of the polarization directions, and further to set the direction to become ordinary light when passing through a birefringent plate described later. It is preferable for suppressing color deterioration due to wavelength dispersion. Further, as shown in FIG. 10B, the transmittance of the red (R) and blue (B) color filters is higher than the transmittance of any of the green (G) color filters (green (G in the figure)). ) Is set to be low), or the width of the rotation direction of the red (R) and blue (B) color filters is set to any green (as shown in FIG. 10C). The color balance can be kept good by taking it wider than the width of the color filter of G).

  FIG. 11 is a schematic configuration diagram showing the configuration of the display device according to the first embodiment of another invention. The display device 110 according to the present embodiment shown in the figure is a projection type display device having an optical system provided with a polarization conversion element 111 instead of the rod integrator 64 shown in FIGS. Thus, the polarization of the light incident on the optical device of the optical apparatus 50 can be controlled, and for example, linearly polarized light and circularly polarized light can be incident. The optically anisotropic medium is composed of ½ wavelength elements formed at predetermined intervals along the rotation direction of the optical device, and the slow axis direction of the ½ wavelength element with respect to the incident linearly polarized light Can be extracted from the polarization direction by a predetermined angle to extract linearly polarized light in an arbitrary polarization direction. By providing an optically isotropic medium that matches the optical path length during transmission of the half-wavelength element in the gap between the half-wavelength elements along the rotation direction of the optical device, When the light passes, the polarization state is maintained, and the polarization direction can be switched when the light passes through the optically anisotropic medium. Further, if the optical path lengths are set equal, the imaging position does not change. Furthermore, the color balance can be maintained by setting both transmittances equal. It is preferable to set the same transmittance at each wavelength, and in the case of a projection type display device, it is necessary to set green particularly equally. Further, the optically anisotropic medium can be composed of quarter wavelength elements formed at predetermined intervals along the rotation direction of the optical device. By alternately arranging quarter wavelength elements having different phase directions with respect to incident circularly polarized light, orthogonal linearly polarized light can be extracted. Further, a ½ wavelength element or a ¼ wavelength element can be used in combination with a color filter in the same manner as a linear polarizer. An optical device can be configured to obtain linearly polarized light that changes over time in combination with the polarization conversion element.

  FIG. 12 is a schematic configuration diagram showing a configuration of a display device according to a second embodiment of another invention. A display device 120 according to the present embodiment shown in the figure is a projection type display device that passes through a surface provided with an optically anisotropic medium twice while passing through an optical device of the optical device. In this optical apparatus, a quadrangular prism optical device 10 shown in FIG. 1 is used. In the same figure, by appropriately setting the power of the condenser lens in the subsequent stage of the optical device, the polarization direction of the illumination light reaching the image display element changes sequentially from top to bottom.

  FIG. 13 is a diagram schematically showing an operation when light is transmitted through the optical device in the optical apparatus of FIG. 12. Here, the light beam is unpolarized and proceeds from the left to the right in the drawing. The optical device 10 is located in the optical path and is rotated as shown. In the state of FIG. 13A, the polarizer and the optical axis positioned on the light incident surface and the light emission surface are perpendicular to each other, and all the light is incident on one surface and is emitted from one surface. By providing a polarizer having a transmission axis in the vertical direction on the incident surface and the output surface, only polarized light in the vertical direction is emitted. Similarly, in the state of FIG. 13C, only the component in the horizontal direction is emitted. In the state of FIG. 13B, both the entrance surface and the exit surface span two surfaces. On the entrance surface 1, the polarizer has a longitudinal transmission axis so that only the longitudinal component is transmitted, but this light is refracted by the refractive index of the transparent material inside the polygonal polarizing filter and guided to the exit surface 1. Since the exit surface 1 transmits polarized light in the vertical direction like the entrance surface 1, the exit light has only a longitudinal polarization component. Since the polarizer has a horizontal transmission axis on the incident surface 2, only the horizontal component is transmitted. Similarly, this light is refracted by the refractive index of the polygonal polarizing filter and guided to the output surface 2. Since the outgoing surface 2 transmits the polarized light in the horizontal direction like the incident surface 2, this outgoing light has only the laterally polarized light component.

  In the above case, an example in which unpolarized light is incident on the polygonal polarizing filter has been described. However, it is possible to use a polygonal polarizing filter even for linearly polarized incident light. FIG. 14 shows an example of this. A quarter wavelength element is provided as an optically anisotropic medium on the surface located on the entrance surface 1 and the exit surface 1, and 1 is provided on the surface located on the entrance surface 2 and the exit surface 2. An isotropic medium equivalent to the transmittance of the / 4 wavelength element is provided. As a result, light incident from the incident surface 1 becomes circularly polarized light in the optical device, and after passing through the output surface 1, becomes linearly polarized light whose polarization plane differs from that of the incident light by 90 degrees. Light incident from the incident surface 2 is emitted from the emission surface 2 without changing its state. A method of converting non-polarized illumination light such as a lamp light source into linearly polarized light has been proposed as a polarization conversion element, and can also be used in the projection type image display apparatus.

  Next, the direction and position of pixel shift will be described. In FIG. 15A, the pixel shift direction is the diagonal direction of the pixel in the DMD. In this case, the polarization direction of the light beam that exits the optical device and enters the DMD while switching the polarization direction in time is The direction is perpendicular or parallel to the diagonal direction of the pixel. In FIG. 15B, the direction of the pixel shift is the side direction of the pixel in the DMD. In this case, the polarization direction of the light beam that exits the optical device and enters the DMD while switching the polarization direction in time is the DMD pixel. The direction is perpendicular or parallel to the side direction. Therefore, it is possible to shift the pixel to the position for interpolating between the scanning lines in the vertical and horizontal directions, and high definition can be achieved efficiently. For example, even if the number of pixels in the sub-scanning direction of DMD is half of 360 for 720 scanning lines that are the D4 standard of HDTV, an image equivalent to 720 is obtained by pixel shift.

FIG. 16 is a diagram showing the structure of a birefringent element used in the present invention. As shown to (a) of FIG. 16, it has an optical axis in the direction inclined with respect to the optical axis. Here, for simplicity, it is assumed that the optical axis and the surface of the birefringent element are perpendicular to each other. Further, in the orthogonal coordinate system shown in FIG. 16, when the light ray has a polarization direction in the x direction, as shown by the light ray 1 in FIG. 16B, that is, a plane including the optical axis and the optical axis of the birefringent element. The polarized light behaves as ordinary light and travels straight through the birefringent element. On the other hand, as shown in the light beam 2, when the light beam has a polarization direction in the y direction, that is, in a state parallel to the plane including the optical axis and the optical axis of the birefringent element, this polarization behaves as extraordinary light. Go straight through the refractive element. When there is a direction of linearly polarized light in other directions, a straight traveling component and a polarizing component are generated. Therefore, the polarization direction of the light incident on the birefringent element is parallel to and perpendicular to the plane including the optical axis and the optical axis of the birefringent element while switching the polarization direction in time after exiting the optical device. By switching with, straight travel and polarization can be controlled. Moreover, since the amount of abnormal light shift s is set to a half pitch of the DMD pixel array, the pixels are equally interpolated, so that a high-quality image can be obtained. Further, as the material of the birefringent plate, KH ₂ PO ₄ (KDP), NH ₄ H ₂ PO ₄ (ADP), LiNbO ₃ , LiTaO ₃ , GaAs, CdTe and the like have a large primary electro-optic effect (Pockels effect). Materials, materials having a large secondary electro-optic effect such as KTN, SrTiO ₃ , CS ₂ , nitrobenzene, and the like can be used.

  FIG. 17 is a time chart showing an example of time distribution in one field of DMD drive signal and polarization state in the optical apparatus of the present invention. As can be seen from the figure, the display switching timing and the polarization state switching timing of the optical device are synchronized, and image degradation can be suppressed. This synchronization may be performed, for example, by forming a mark for optical detection at a predetermined position of the optical device and obtaining a synchronization signal by reflected light from the mark.

  FIG. 18 is a schematic configuration diagram showing a configuration of a stereoscopic image display system according to an embodiment of another invention. For example, a projection display device similar to that shown in FIG. 8 is used in the stereoscopic image display system according to this embodiment shown in FIG. From this projection type display device, orthogonal polarized light is alternately emitted during one frame by the optical device of the optical device 70. Polarization selection means is provided in which a polarization filter having a transmission axis corresponding to the polarization direction of linearly polarized light is formed corresponding to the right and left eyes so that the orthogonal polarized light can be recognized independently by the right eye and the left eye. In the three-dimensional image display system of FIG. 18, an observer wears spectacles-type polarization selection means 180.

  FIG. 19 is a time chart showing an example of time distribution in one field of DMD drive signal and polarization state in a stereoscopic image display system of another invention. As can be seen from the figure, the display switching timing and the polarization state switching timing of the optical device are synchronized as described above, and image degradation can be suppressed. As the stereoscopic image signal input to the DMD, for example, as shown in FIG. 20, an image obtained by photographing the subject 200 with the two cameras 201 and 202 corresponding to both eyes can be used. The respective frame images 203 and 204 obtained at the same timing in the respective cameras 201 and 202 are decomposed into RGB to obtain six subfield images 205 to 210. The polarization direction and the color of the light emitted from the optical device of the optical device 70 in FIG. 18 are, for example, [Right R] → [Left G] → [Right B] → [Left R] → [Right G] as shown in FIG. ] → [Left B], and in accordance with this, image signals corresponding to six subfield images are transmitted to the DMD 66 in FIG. As a result, a color stereoscopic image can be visually recognized by the left and right eyes during one field. In order to suppress flicker, it is desirable to set different polarization directions and colors in adjacent subfield images.

  Note that it is also possible to configure a stereoscopic image display system without using the glasses-type polarization selection means 180 as shown in FIG. For example, a lenticular screen is used as the screen 181 in FIG. 18, and a polarizing plate array in which orthogonal polarizing filters are formed in stripes is provided in the lenticular screen. The lenticular lens is designed so that all the light passing through one of the stripes is guided to the right eye and all the light passing through the other is guided to the left eye. In addition, the polarization direction of the light emitted from the DMD 66 is switched in a time-division manner by the optical device of the optical device 70, so that the light passing through the striped polarization filter is alternately shielded. Therefore, by switching the image of the DMD 66 corresponding to the eye to which light that is not shielded is guided, an image independent of the left and right eyes can be formed, and a stereoscopic image can be formed. However, there is a problem that the light use efficiency is lowered by halving the actual light amount by the polarizing plate array.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications and substitutions are possible as long as they are described within the scope of the claims.

It is a perspective view which shows the structure of the optical device which concerns on the 1st Example of this invention. It is a perspective view which shows the structure of the other example of the optical device which concerns on the 1st Example of this invention. It is a perspective view which shows the structure of the optical device which concerns on the 2nd Example of this invention. It is a top view which shows the structural example which formed the linear polarizer in the surface of a transparent disk. It is a perspective view which shows the structure of the optical apparatus which concerns on the 1st Embodiment of another invention. It is a schematic block diagram which shows the structure of the display apparatus using the optical apparatus of the 1st Example. It is a perspective view which shows the structure of the optical apparatus which concerns on the 2nd Embodiment of another invention. It is a schematic block diagram which shows the structure of the display apparatus using the optical apparatus of the example of 2nd Embodiment. It is a figure which shows the relationship between a pixel shift position and each RGB color position. FIG. 4 is a side view of the optical device of FIG. 3. It is a schematic block diagram which shows the structure of the display apparatus which concerns on the 1st Embodiment of another invention. It is a schematic block diagram which shows the structure of the display apparatus which concerns on the 2nd Embodiment of another invention. It is the figure which showed typically the operation | movement when light permeate | transmits the optical device in the optical apparatus of FIG. It is the figure which showed typically the operation | movement in case light permeate | transmits the optical device using a polyhedral polarizing filter. It is a figure which shows another example of the direction and position of a pixel shift. It is a figure which shows the structure of the birefringent element used by this invention. It is a time chart which shows the example of time distribution in 1 field of a DMD drive signal and a polarization state. It is a schematic block diagram which shows the structure of the stereo image display system which concerns on one embodiment of another invention. It is a time chart which shows the example of time allocation in 1 field of a DMD drive signal and a polarization state in the stereo image display system of another invention. It is a figure which shows the stereo image signal input into DMD obtained using two cameras. It is a schematic block diagram which shows the structure of the conventional projection type display apparatus. It is a figure which shows the structural example of a color wheel.

Explanation of symbols

10, 20, 30; optical device, 11, 21, 31; rotating shaft,
12, 22; surface, 32; side surface, 50, 70; optical device,
51, 71; fixed mirror, 110, 120; display device,
180; glasses-type polarization selecting means; 181; screen.

Claims (42)

  A surface having a rotation axis, parallel to the rotation axis and having translucency, wherein at least part of the surface is formed of an optically anisotropic medium, An optical device characterized in that the polarization state is switched temporally and emitted.   2. A polygonal column having a rotation axis, having a surface parallel to the rotation axis and having translucency, wherein at least part of the side surface is formed of an optically anisotropic medium. Optical devices.   The optical device according to claim 1, wherein the optical device is a cylinder having a rotation axis, and at least a part of the side surface is formed of an optically anisotropic medium.   The optical device according to claim 1, wherein the optically anisotropic medium is a polarizer formed at a predetermined interval along the rotation direction of the optical device.   The optical device according to claim 4, wherein a plurality of polarizers having different polarization directions of the emitted light are arranged along the rotation direction of the optical device.   The optical device according to claim 5, wherein two polarizers in which the polarization direction of the emitted light is orthogonal are alternately arranged along the rotation direction of the optical device.   The optical device according to claim 1, wherein the optically anisotropic medium is a ½ wavelength element formed at a predetermined interval along a rotation direction of the optical device.   The optical device according to claim 7, wherein an optical isotropic medium that matches an optical path length when the half-wavelength element is transmitted is provided in a gap between the half-wavelength elements along the rotation direction of the optical device.   The optically isotropic medium having a transmittance equal to the transmittance at the time of transmitting a half-wavelength element is provided in a gap between the half-wavelength elements along the rotation direction of the optical device. Optical device.   The optical device according to claim 1, wherein the optically anisotropic medium is a ¼ wavelength element formed at a predetermined interval along a rotation direction of the optical device.   The optical device according to claim 10, wherein quarter wavelength elements having different phase directions are alternately arranged along the rotation direction of the optical device.   The optical device according to claim 1, further comprising a color filter along a rotation direction of the optical device, wherein at least one of the color filters also serves as an optically anisotropic medium.   13. The color filter according to claim 12, wherein the color filter includes at least three colors of red (R), green (G), and blue (B), and emits polarized light orthogonal to each color in at least six polarization states during one rotation. Optical device.   The optical device according to claim 13, wherein in six polarization states, adjacent colors are set to different colors.   The said color filter consists of red (R), green (G), blue (B), and green (G), and each green (G) emits the polarization | polarized-light to which each green (G) orthogonally crosses in 1 rotation. Optical device.   16. The optical device according to claim 15, wherein the emitted light of red (R) and blue (B) is set to a polarization state that emits linearly polarized light parallel to the polarization direction of any green (G).   The optical device according to claim 15 or 16, wherein the red (R) and blue (B) color filter transmittances are higher than the transmittance of any green (G) color filter.   The optical device according to claim 15 or 16, wherein the width of the red (R) and blue (B) color filters in the rotation direction is wider than the width of any of the green (G) color filters.   It comprises at least one optical device according to any one of claims 1 to 18, and a light beam is incident on the optical device from a predetermined direction, and a light beam having a polarization state different from the polarization state of incident light is switched over time. An optical device that emits light.   The optical apparatus according to claim 19, wherein an optical axis of a light beam transmitted through an optically anisotropic medium formed in the optical device is perpendicular to a rotation axis.   The optical apparatus according to claim 19 or 20, wherein a straight line including an optical axis of a light beam transmitted through the optically anisotropic medium passes through a rotation axis of the optical device.   The optical device according to any one of claims 19 to 21, wherein a light beam incident on the optically anisotropic medium is convergent light, and a convergence point coincides with a portion where the optically anisotropic medium is formed.   The optical apparatus according to any one of claims 19 to 22, wherein the optical apparatus passes once through the surface on which the optically anisotropic medium is formed while passing through the optical device.   24. The optical apparatus according to claim 23, wherein a fixed mirror is installed inside the optical device and on an optical path of a light beam that passes through the optically anisotropic medium.   25. The optical apparatus according to claim 24, wherein a traveling direction of the light beam in the optical device is a direction from the fixed mirror toward an optically anisotropic medium.   The optical apparatus according to any one of claims 23 to 25, wherein a light beam incident on the optical device according to any one of claims 7 to 9 is linearly polarized light.   The optical apparatus according to any one of claims 19 to 22, wherein the optical apparatus passes through the surface on which the optically anisotropic medium is formed twice while passing through the optical device.   The optical apparatus according to any one of claims 23 to 25 and 27, wherein a light beam incident on the optical device according to any one of claims 4 to 6 is non-polarized light.   The optical device according to any one of claims 23 to 25 and 27, wherein a light beam incident on the optical device according to claim 10 or 11 is linearly polarized light.   The optical device according to any one of claims 19 to 29, wherein the polarization state of the outgoing light that changes over time is two linearly polarized light beams orthogonal to each other.   A display device comprising the optical device according to claim 19.   32. The display device according to claim 31, comprising a digital micromirror device.   The display device according to claim 31 or 32, wherein the optical device is installed on an illumination light side of the digital micromirror device.   A polarization direction of a light beam emitted from the optical device included in the optical apparatus and incident on the digital micromirror device while temporally switching a polarization direction is perpendicular to a diagonal direction of pixels in the digital micromirror device or The display device according to claim 32 or 33, wherein the display device is in a parallel direction.   The polarization direction of light emitted from the optical device included in the optical apparatus and incident on the digital micromirror device while temporally switching the polarization direction is perpendicular or parallel to the side direction of the pixels in the digital micromirror device. The display device according to claim 32 or 33, wherein the display device is in a different direction.   The display device according to any one of claims 32 to 35, wherein a birefringent element having an optical axis in a direction inclined with respect to an optical axis is installed on a side of light emitted from the digital micromirror device.   The optical device included in the optical device emits light, and the polarization direction of light incident on the birefringent element while temporally switching the polarization direction is relative to the plane including the optical axis and the optical axis of the birefringent element. 37. A display device according to claim 36, wherein the display device is in a vertical or parallel direction.   The digital micromirror in which the amount of polarization due to the birefringence of light when the polarization direction of the light incident on the birefringence element is parallel to the plane including the optical axis and the optical axis of the birefringence element is in the polarization direction. 38. A display device according to claim 37, which is a half pitch of a pixel array in the device.   The display device according to any one of claims 32 to 38, wherein a display switching timing of the digital micromirror device is synchronized with a polarization state switching timing of an optical device included in the optical device.   36. A display device according to any one of claims 33 to 35 and a polarizing filter having a transmission axis that coincides with the polarization direction of each linearly polarized light emitted from the display device, corresponding to the left and right eyes of an observer. A stereoscopic image display device comprising polarization selection means.   41. The stereoscopic image display apparatus according to claim 40, wherein the polarization selection unit is a glasses type, and the polarization filter is provided in glasses corresponding to each eye. Parallel to the transmission axis of the polarizing filter provided at the position of the right eye or left eye of the polarized light selecting means of the glasses type in the time zone in which the digital micromirror device is displaying an image for the right eye or the left eye 42. The stereoscopic image display device according to claim 40, wherein the direction of polarization is controlled so that simple linearly polarized light reaches an observer.

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