JP2005215602A - Optical shift element and projection type picture display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical shift element restraining the difference of optical path length to be small. <P>SOLUTION: The optical shift element is equipped with a 1st optical shift part capable of selectively shifting the position of the optical axis of incident light to 1st and 2nd positions and emitting the light. The 1st optical shift part includes a modulation part g1 modulating the direction of polarization of the incident light, and 1st and 2nd light guide parts g2 and g3 respectively having a base plate 101 provided with a plurality of minute prisms 101b having an inclined surface 101a on one principal plane and double refraction material 102 arranged to come into contact with the plurality of minute prisms and having a refractive index different according to the direction of polarization of the light. Then, the 1st and the 2nd light guide parts g2 and g3 are arranged so that the light transmitted through the modulation part g1 may be made incident on the 1st light guide part g2 and the inclined surfaces 101a of the minute prisms 101b of the 1st and the 2nd light guide parts g2 and g3 may be parallel with each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image display device, and more particularly to a single-plate projection image display device that performs color display using a single image display panel without using a color filter, and an optical shift element suitable for the device.

  As an image display device, a projection type image display device using a liquid crystal display panel is conventionally known. In a projection type image display apparatus using a liquid crystal display panel, the liquid crystal display panel itself does not emit light, so that it is necessary to provide a separate light source. However, compared with a projection type image display apparatus using a CRT, the projection type image display apparatus has very excellent features such as a wide color reproduction range, a small size and a light weight, and no need for convergence adjustment. .

  In order to perform full color display by a projection type image display apparatus using a liquid crystal display panel, there are a three-plate type using three liquid crystal display panels according to three primary colors and a single-plate type using only one sheet.

  In the three-plate projection type image display device, an optical system that divides white light into three primary colors of red (R), green (G), and blue (B), and R, G, and B light respectively Full-color display is realized by optically superimposing R, G, and B color images using three liquid crystal display panels that modulate to form images. In the three-plate projection type image display device, light emitted from a white light source can be effectively used. However, since the optical system is complicated and the number of parts increases, generally, a single-plate projection is performed from the viewpoint of cost and size. This is disadvantageous compared to the type image display device.

  A single-plate projection-type image display apparatus uses a single liquid crystal display panel provided with color filters of three primary colors arranged in a mosaic shape or a stripe shape. Then, the full color image displayed on the liquid crystal display panel is projected onto a projection surface such as a screen by the projection optical system. Such a single-plate projection-type image display device is disclosed in, for example, Patent Document 1. In the case of the single plate type, since one liquid crystal display panel is used, the optical system has a simple configuration compared to the case of the three plate type, and is suitable for providing a small projection type image display device at a low cost. .

  However, in the case of a single plate type using a color filter, light absorption occurs in the color filter, so that the brightness of the image is reduced to about 1/3 compared to the case of a three plate type using an equivalent light source. . In addition, since it is necessary to display one pixel as a set of three pixel areas corresponding to R, G, and B of the liquid crystal display panel, the resolution of the image is reduced to 1/3 of the resolution of the three-plate type. End up.

  Brightening the light source is one solution to the reduction in brightness, but it is not preferable to use a light source with high power consumption when used for consumer use. In addition, when an absorption type color filter is used, the energy of light absorbed by the color filter changes to heat, so if the light source is brightened unnecessarily, the temperature of the liquid crystal display panel not only rises, but the color filter fades. Accelerated. Therefore, how to effectively use the given light is an important issue in improving the utility value of the projection type image display apparatus.

  For example, Patent Document 2 discloses a liquid crystal display device that performs full-color display without using a color filter in order to improve image brightness by a single-plate projection image display device. In this liquid crystal display device, white light emitted from a light source is divided into R, G, and B light fluxes by a dielectric mirror such as a dichroic mirror, and each light flux is arranged on the light source side of the liquid crystal display panel. Enter the array at different angles. Each light beam incident on the microlens passes through the microlens and is condensed on the corresponding pixel region according to the incident angle. Therefore, the separated R, G, and B light fluxes are modulated in separate pixel areas and used for full-color display.

  Patent Document 3 discloses a display device that uses a transmissive hologram element corresponding to R, G, and B light instead of using the above-described dielectric mirror to improve the light utilization rate. Further, Patent Document 4 discloses an apparatus in which a transmission hologram element is provided with a periodic structure corresponding to a pixel pitch and functions of a dielectric mirror and a microlens are provided.

  As for resolution, which is another problem of the single-plate type, by adopting field sequential display, a single liquid crystal display panel can obtain a resolution equivalent to that of the three-plate type. The field sequential method uses a phenomenon (continuous additive color mixture) in which the colors of each image displayed in a time-division manner are formed by additive color mixture by switching the color of the light source at a speed that cannot be resolved by human vision.

  A projection-type image display device that performs full-color display by a field sequential method has, for example, the configuration shown in FIG. In this display device, a disk 501 composed of R, G, B color filters is rotated at high speed in accordance with the vertical scanning period of the liquid crystal display panel 502, and an image signal corresponding to the color of the color filter is displayed on the liquid crystal display panel 502. Are sequentially input to the driving circuit. The human eye recognizes a composite image 504 of the images 503r, 503g, and 503b for each color.

  According to such a field sequential display device, unlike the single-plate method, R, G, and B images are displayed in a time-sharing manner on each pixel of the liquid crystal display panel. .

  As another field sequential display device, Non-Patent Document 1 discloses a projection type image display device that irradiates different regions of a liquid crystal display panel with R, G, and B light fluxes. In this display device, white light emitted from a light source is separated into R, G, and B light fluxes by a dielectric mirror, and different regions of the liquid crystal display panel are irradiated with the R, G, and B light fluxes. The R, G, and B light irradiation positions on the liquid crystal display panel are sequentially switched by rotating a cube-shaped prism.

  According to the devices disclosed in Patent Document 2, Patent Document 3, Patent Document 4, and the like, the brightness is improved, but the resolution remains 1/3 of the three-plate type. The reason is that three pixels for R, G, and B, which are spatially separated, are used as one set to display one pixel (dot).

  On the other hand, in the case of the normal field sequential method, the resolution is improved to the same level as the resolution of the three-plate type. However, since a color filter is used, there are problems similar to those of the conventional single plate type in terms of image brightness and color filter deterioration.

  On the other hand, in the case of the above-described display device described in Non-Patent Document 1, it is necessary to use illumination light having a very high parallelism so that the light irradiation positions of R, G, and B do not overlap each other. is there. However, in order to obtain such illumination light, it is necessary to remove non-parallel components from the light generated by the light source. For this reason, the illumination light with a very high parallelism obtained will have low utilization efficiency with respect to the light generated by the light source.

  As described above, none of the above-described conventional technologies achieves improvement of both brightness and resolution, which are problems of a single plate type.

  On the other hand, the applicant has proposed a single-plate projection type image display device shown in Patent Documents 5 and 6.

  In the projection type image display device described in Patent Document 5, a liquid crystal display device similar to the liquid crystal display device described in Patent Document 2 is used, and white light is divided into luminous fluxes for each color in the same manner. Each light beam is incident on the pixel region at a different angle. In this projection-type image display device, each frame image is time-divided into a plurality of sub-frame images and synchronized with the vertical scanning period of the liquid crystal display panel in order to improve the light utilization efficiency and realize high-resolution display. Thus, the incident angle of the light beam is periodically switched.

  Moreover, in the projection type image display apparatus shown in Patent Document 6, white light is divided into R, G, and B light beams using a dichroic mirror, and the obtained light beams are displayed at different angles using a microlens array. The light is incident on different pixel areas of the panel. On the image display panel, data of a plurality of subframe images generated from the data of each frame image constituting the image is displayed in a time division manner. Then, by sequentially shifting these sub-frame images on the projection surface, light (R, G, B light) belonging to different wavelength regions modulated in different pixel regions of the image display panel is projected on the projection surface. Irradiate the same area sequentially.

  According to these projection type image display devices, since no color filter is used, high light use efficiency can be achieved, and a high-resolution image can be displayed.

  In the projection-type image display device disclosed in Patent Document 6, an optical shift element is used to sequentially shift subframe images on a projection surface and synthesize the subframe images on a predetermined projection surface. As shown in FIG. 2, the optical shift element includes a first optical shift unit g3 and a second optical shift g4. As shown in FIG. 3, each optical shift unit includes a first element g1 made of a liquid crystal layer that modulates the polarization direction of light and a second birefringent plate (quartz plate) having a refractive index that varies depending on the polarization direction of light. Element g2. Here, the “polarization direction” means the vibration direction of the electric field vector of light. The polarization direction is perpendicular to the light propagation direction k. A plane including both the electric field vector and the light propagation direction k is referred to as a “vibration plane” or a “polarization plane”.

  In the illustrated example, it is assumed that light exiting the image display panel is polarized in the vertical direction (polarization direction = screen vertical direction). When no voltage is applied to the liquid crystal layer of the liquid crystal element g1, the polarization plane of the light exiting the image display panel does not rotate in the process of light passing through the liquid crystal element g1, as shown in FIG. On the other hand, when an appropriate level voltage is applied to the liquid crystal layer of the liquid crystal element g1, as shown in FIG. 3, the polarization plane of light exiting the image display panel is rotated by 90 ° by the liquid crystal layer. . Although the case where the rotation angle is 90 ° is illustrated here, the rotation angle can be arbitrarily set depending on the design of the liquid crystal layer.

  The quartz plate g2 is a uniaxial crystal (positive crystal) and has birefringence, and therefore exhibits a different refractive index depending on the orientation. The quartz plate g2 is arranged so that its light incident surface is perpendicular to the optical axis of incident light (parallel to the propagation direction k). The optical axis of the quartz plate g2 is included in a vertical plane in FIGS. 2 and 3, but is inclined from the light incident surface of the quartz plate g2. Therefore, as shown in FIG. 2, when light having a perpendicular polarization direction is incident on the quartz plate g2, the light is refracted in a plane including the optical axis in accordance with the inclination of the optical axis in the quartz plate g2, and the light Shifts vertically. In this case, a plane including both the optical axis of the quartz plate g2 and the optical axis of the incident light (hereinafter referred to as “main cross section”) is in a parallel relationship with the polarization plane of the incident light. Thus, the incident light whose polarization plane is parallel to the main cross section is “abnormal light” for the quartz plate g2.

  On the other hand, as shown in FIG. 3, when the light whose polarization plane is in the horizontal horizontal direction is incident on the quartz plate g2, the polarization plane is orthogonal to the optical axis (or main cross section) of the quartz plate g2, so that the light is not refracted, There is no shift of the luminous flux. In this case, the light incident on the quartz plate g2 is “ordinary light” for the quartz plate g2.

  Thus, the polarization direction of the light incident on the crystal plate g2 can be controlled and the shift of the light flux can be adjusted depending on whether or not a voltage is applied to the liquid crystal element g1.

Here, it is assumed that the thickness of the quartz plate g2 is t and the refractive indexes of the extraordinary light and the ordinary light of the quartz plate g2 are _ne1 and _no1 , respectively. When the optical axis is inclined 45 ° from the incident surface in the main cross section, the light flux shift amount ΔD is expressed by the following equation.

t = ΔD · (2 · n e1 · n o1) / (n e1 2 -n o1 2)

  From this equation, it can be seen that the shift amount ΔD of the luminous flux is proportional to the thickness t of the quartz plate g2. By adjusting the thickness t of the crystal plate g2, the shift amount of the subframe image can be set to an arbitrary value.

In another example of the optical shift element disclosed in Patent Document 6, in each of the two optical shift units, a micro prism or a diffraction grating is provided on the liquid crystal side surface of one of the two substrates sandwiching the liquid crystal layer. The incident light is shifted by forming and applying a voltage to the liquid crystal layer. As shown in FIGS. 5 and 6, the optical shift unit i6 has a liquid crystal layer i5 and two transparent substrates sandwiching the liquid crystal layer i5, and a minute amount is formed on the liquid crystal side surface of one of the transparent substrates. A prism array i3 is formed. More specifically, the optical shift unit i6 includes a transparent substrate on which a microprism array i3 whose surface is covered with the transparent electrode i1 and the alignment film i2 is formed, and a transparent substrate whose surface is covered with the transparent electrode i1 and the alignment film i2. And a nematic liquid crystal layer i5 sandwiched between them. The liquid crystal layer i5 is homogeneously aligned. When a voltage is applied between the two transparent electrodes i1, the liquid crystal layer i5 is aligned in a direction perpendicular to the substrate as shown in FIG. As shown in FIG. 6, a homogeneous alignment state is obtained. The refractive index of the liquid crystal layer i5 in the case where no voltage is applied to n _e2, the refractive index of the liquid crystal layer i5 when the application of the voltage to n _o2. Micro prism array i3 is made of a material consisting of a refractive index n ₂ near the n _o2 value.

  When no voltage is applied to the liquid crystal layer i5, a difference in refractive index is generated between the liquid crystal layer i5 and the microprism array i3. Therefore, the light beam incident on the microprism array i3 is refracted according to Snell's law. On the other hand, when a voltage is applied, the refractive index difference between the liquid crystal layer i5 and the minute prism array i3 decreases according to the magnitude of the applied voltage. As the refractive index difference decreases, the refraction angle of the light beam incident on the microprism array i3 also decreases.

When the apex angle of the minute prism is θ ₄ , the refraction angle δ of the light beam when no voltage is applied to the liquid crystal layer i5 is expressed by the following equation.

δ = (n _e2 −n ₂ ) × θ ₄

  If two optical shift portions i6 are combined and arranged as shown in FIG. 7, an optical shift element is formed. The image shift amount ΔD by the optical shift element is expressed by the following equation, where L is the distance between the two microprism arrays.

ΔD = L · tan δ
JP 59-230383 A Japanese Patent Laid-Open No. 4-60538 JP-A-5-249318 JP-A-6-222361 Japanese Patent Laid-Open No. 9-214997 International Publication No. 01/96932 Pamphlet 6th International Display Workshop (IDW) Proceedings, December 1999, P989-P992

  In the optical shift element shown in FIGS. 2 to 4 and FIGS. 5 to 7 of Patent Document 6 described above, the optical path length when passing through the optical shift element for each shift position of the optical axis of the emitted light is shown in FIG. So different. For this reason, in the image display device disclosed in Patent Document 6, the light that has passed through the optical shift element has a different condensing state due to the difference in optical path length, and the focus position by the projection lens is also different. That is, on the screen, the size (blurring method) of each pixel differs for each shift position of the optical axis. As a result, adjacent pixels overlap and a periodic dot-like pattern appears in the screen of the projection surface, causing a problem that the image quality of the projected image is impaired.

  Further, for example, in the optical shift element shown in FIGS. 2 to 4, a crystal plate having birefringence such as crystal or lithium niobate is used as the birefringence plate. However, it takes a long time to grow a single crystal of such a material. Further, it is necessary to optically polish the surface of the grown substrate. For example, in the case of a crystalline substrate made of quartz, it takes several months for crystal growth. Therefore, once crystal growth is started, it is not easy to change the specifications of the substrate halfway. Therefore, it is difficult to industrially mass-produce the optical shift element shown in FIGS. 2 to 4 and it is difficult to reduce the manufacturing cost.

  In the optical shift element shown in FIGS. 5 to 7, since the liquid crystal layer is sandwiched between microprisms, the liquid crystal layer cell gap (the thickness of the liquid crystal layer) is not uniform. For this reason, the response speed of the liquid crystal changes according to the cell gap. In particular, at the valley portion of the micro prism, that is, where the cell gap of the liquid crystal layer is the largest, the response speed becomes slow and the display quality deteriorates. Even with such a liquid crystal layer, it is possible to drive the liquid crystal uniformly, but for this purpose, it is necessary to control the distribution of the voltage applied to the liquid crystal layer in a complicated manner. In addition, it is necessary to prevent the peak portion of the microprism from coming into contact with the opposing substrate.

  The present invention has been made to solve at least one of the above-described problems, and its purpose is to provide bright, high-resolution, uniform and high-quality display, which is suitable for downsizing and cost reduction. Another object of the present invention is to provide an optical shift element and a projection type image display device for realizing the projection type image display device.

  The optical shift element of the present invention includes a first optical shift unit that can emit light by selectively shifting the optical axis to the first and second positions with respect to the position of the optical axis of the incident light. ing. The first optical shift unit is disposed so as to be in contact with a modulation unit that modulates the polarization direction of incident light, a substrate on which a plurality of micro prisms having inclined surfaces are provided on one main surface, and the plurality of micro prisms. The first and second light guide parts each having a birefringent material having a refractive index different depending on the polarization direction of the light, and the light transmitted through the modulation part is incident on the first light guide part, The first and second light guides are arranged so that the slopes of the micro prisms of the first and second light guides are parallel to each other.

  In a preferred embodiment, each of the first and second light guide parts further includes a first transparent plate having a main surface subjected to an alignment treatment, and the birefringent material is a liquid crystal material, The birefringent material is sandwiched between the substrate and the transparent plate so as to be in contact with the main surface subjected to the alignment treatment.

  In a preferred embodiment, the first optical shift unit further includes a second transparent plate, and the first transparent substrates of the first and second light guide units sandwich the second transparent plate. As described above, the second transparent plate and the first and second light guide portions are integrally disposed.

  In a preferred embodiment, the first optical shift unit further includes a transparent plate, and the birefringent material of each of the first and second light guide units sandwiches the transparent plate and the first optical shift unit. The 1st and 2nd light guide part is arrange | positioned integrally.

  In a preferred embodiment, a region in contact with the birefringent material of the transparent plate is subjected to an alignment treatment, and the birefringent material is a liquid crystal material.

  In a preferred embodiment, the birefringent material is a polymer liquid crystal.

  In a preferred embodiment, the first position and the second position are symmetric with respect to the position of the optical axis of the incident light.

  In a preferred embodiment, the optical path length from entering the first optical shift unit to exiting is equal regardless of the shift position of the optical axis.

  In a preferred embodiment, the birefringent material of the first and second light guide portions has an optical axis parallel to a ridge line direction of the microprism.

  In a preferred embodiment, the optical shift element is configured such that the light emitted from the first optical shift unit is incident, and the optical axis is selectively placed at the first and second positions with respect to the position of the optical axis of the incident light. And a second optical shift unit capable of emitting light by shifting the second optical shift unit, and the second optical shift unit has the same structure as the first optical shift unit.

  In a preferred embodiment, the direction of the inclined surface of the micro prism of the first and second light guides in the first optical shift unit, and the first and second light guides in the second optical shift unit. The direction of the inclined surface of the micro prism of the portion is symmetric with respect to the optical axis of the light incident on the first optical shift portion.

  In a preferred embodiment, the distance between the slopes of the micro prisms of the first and second light guide sections in the first optical shift section is the first and second light guide sections in the second optical shift section. It is about twice or about 1/2 of the distance of the slope of the microprism.

  In a preferred embodiment, optical characteristics of the birefringent material or inclination angles of the inclined surfaces of the microprisms in the first optical shift unit and the second optical shift unit are different.

  In a preferred embodiment, the angle at which the optical axis is refracted on the slope of the micro prisms of the first and second light guides in the first optical shift unit is the first and second in the second optical shift unit. The angle of refraction of the optical axis at the slope of the micro prism of the second light guide is about twice or about ½.

  In a preferred embodiment, the birefringent materials of the first and second light guide sections in the second optical shift section have an optical axis parallel to the ridge line direction of the microprism.

In a preferred embodiment, the modulation unit includes a liquid crystal cell that modulates a light deflection direction in accordance with an applied voltage.
The projection type image display device of the present invention separates light from a light source, an image display panel having a plurality of pixel regions each capable of modulating light, and light of a plurality of wavelength regions. A light control means for condensing the light of the separated wavelength region in a corresponding pixel region of the plurality of pixel regions according to the wavelength region, and a projection surface by the light modulated by the image display panel An optical system that forms an image thereon, and a circuit that generates data of a plurality of subframe images from the data of each frame image constituting the image, and displays the plurality of subframe images in a time division manner on the image display panel And any one of the optical shift elements that shifts a subframe image selected from the plurality of subframe images displayed by the image display panel on the projection surface. Obtain.

  According to the present invention, the position of the optical axis of the emitted light can be shifted to the first and second positions with respect to the position of the optical axis of the incident light by the microprism. The difference in optical path length between the two optical paths can be reduced. Therefore, according to the projection type image display apparatus using this optical shift element, it is possible to project a high-quality image having no periodic dot-like pattern or the like on the screen of the projection surface.

  In the projection type image display apparatus of the present invention, as disclosed in Patent Document 6, white light emitted from the light source is converted into red (R), green (G), light using a light control means such as a dichroic mirror. The light is separated into light having the component in the blue (B) wavelength region. The separated R, G, and B lights are incident on different pixel areas of the image display panel at different angles using a microlens array, and the same color area has the same color regardless of the passage of time. Light is irradiated.

  On the image display panel, data of a plurality of subframe images generated from the data of each frame image constituting the image is displayed in a time division manner. For example, each frame image is divided into three sub-frame images, and the three sub-frame images are displayed by being shifted by one pixel on the image display panel. At this time, when attention is paid to one pixel constituting a certain frame image, this pixel corresponds to a pixel region on the image display panel irradiated with R, G, B light.

  R, G, and B light incident on the image display panel at different angles are emitted from the image display panel at different angles. The emitted R, G, and B light is modulated by the image display panel using the data of the subframe image, and thus becomes a subframe image.

  Among the plurality of subframe images, the selected subframe image is displayed with its position shifted on the projection surface by the optical shift element.

  In this method, when there is a difference in the imaging state (size, blur) of each color pixel to be projected at the same position on the projection surface, the projected image includes a dot pattern on the entire screen, Causes degradation of image quality. For this reason, it is important to suppress a difference in optical path length due to a difference in shift position in an optical shift element that causes a difference in imaging state.

  The optical shift element of the present invention has at least one optical shift that can emit light by selectively shifting the optical axis to at least the first and second positions with respect to the position of the optical axis of the incident light. Department. This optical shift unit is a modulation unit that modulates the polarization direction of incident light, a birefringent material having a different refractive index depending on the polarization direction of light, and a minute prism are bonded together, and light that has passed through the modulation unit is incident The first light guide unit and the first light guide unit have the same structure as the first light guide unit, and the slope of the micro prism is parallel to the slope of the micro prism of the first light guide unit. The 2nd light guide part arrange | positioned with respect is included.

  The amount of shift of the optical axis by the optical shift element is determined by the distance between the first light guide unit and the second light guide unit, and the angle of the inclined surface of the microprism between the first light guide unit and the second light guide unit. It depends on many parameters such as the optical properties of the birefringent material and the material of the microprism in the first light guide and the second light guide. For this reason, it is easy to adjust the shift amount of the optical axis.

  In the optical shift element of the present invention, even if the optical axis is shifted, the optical path length difference in the optical shift element is small. For this reason, the image formation state on the projection surface becomes uniform, and a projection type image display apparatus capable of displaying a high-quality image is realized. Note that the scope of application of the present invention is not limited to a projection type image display device, but can be suitably applied to a direct-view type image display device such as a viewer or a head-mounted display. A preferred embodiment of the present invention will be described using an apparatus as an example.

(First embodiment)
First, the structure of the projection type image display apparatus of the present embodiment will be schematically described with reference to FIGS.

  The projection-type image display apparatus according to the present embodiment includes a light source 1, a liquid crystal display panel 8, a light control unit that focuses light from the light source 1 on a corresponding pixel area of the liquid crystal display panel 8 according to a wavelength range, A projection optical system that projects the light modulated by the liquid crystal display panel 8 onto the projection surface.

  This projection-type image display device includes a spherical mirror 2 that reflects light (white light) emitted backward from the light source 1 forward, a condenser lens 3 that converts light from the light source 1 and the spherical mirror 2 into parallel luminous flux, and this luminous flux. Dichroic mirrors 4, 5, and 6 are further provided for separating the light beams into a plurality of light beams according to the wavelength range. The light reflected by the dichroic mirrors 4, 5, 6 is incident on the microlens array 7 at different angles depending on the wavelength range. The microlens array 7 is attached to the light source side substrate of the liquid crystal display panel 8, and light incident on the microlens 7 at different angles is collected in corresponding pixel regions at different positions.

  The projection optical system of the present projection type image display apparatus includes a field lens 9 and a projection lens 11, and projects a light beam 12 transmitted through the liquid crystal display panel 8 onto a screen (projection surface) 13. In the present embodiment, an optical shift element 10 is disposed between the field lens 9 and the projection lens 11. FIG. 8 shows light beams 12a and 12b that are shifted by the optical shift element 10 in a direction parallel to the projection surface. In order to shift the light flux, the optical shift element 10 has only to be inserted at any position between the liquid crystal display panel 8 and the screen 13, and is disposed between the projection lens 11 and the screen 13. Also good.

  Next, each component of the projection type image display apparatus will be described in order. In the present embodiment, a metal halide lamp having an optical output of 150 W, an arc length of 5 mm, and an arc diameter of 2.2 mm is used as the light source 1, and this lamp is arranged so that the arc length direction is parallel to the drawing sheet. As the light source 1, in addition to the metal halide lamp, a halogen lamp, an ultrahigh pressure mercury lamp, a xenon lamp, or the like may be used. The light source 1 used in the present embodiment emits white light including light in three wavelength ranges corresponding to the three primary colors.

  A spherical mirror 2 is disposed on the back surface of the light source 1, and a condenser lens 3 having a diameter of 80 mmφ and a focal length of 60 mm is disposed on the front surface of the light source 1. The spherical mirror 2 is arranged so that its center coincides with the center of the light emitting part of the light source 1, and the condenser lens 3 is arranged so that its focal point coincides with the center of the light source 1.

  With such an arrangement, the light emitted from the light source 1 is collimated by the condenser lens 3 and illuminates the liquid crystal display panel 8. The parallelism of the light that has passed through the condenser lens 3 is, for example, about 2.2 ° in the arc length direction (direction parallel to the paper surface of FIG. 1) and about 1 ° in the arc radial direction.

  The liquid crystal display panel 8 used in this embodiment is a transmissive liquid crystal display element in which a microlens array 7 is arranged on a transparent substrate on the light source side. The type and operation mode of the liquid crystal can be arbitrarily selected, but it is preferable that the liquid crystal can operate at high speed. In this embodiment, the operation is performed in the TN (twisted nematic) mode. The liquid crystal display panel 8 is provided with a plurality of pixel regions for modulating light. The “pixel region” in the present specification means individual light modulation units spatially separated in the image display panel. In the case of the liquid crystal display panel 8, a voltage is applied to a corresponding portion of the liquid crystal layer by a pixel electrode corresponding to each pixel region, and light is modulated by changing optical characteristics of the portion.

  In the liquid crystal display panel 8, for example, 768 (H) × 1024 (V) scanning lines are driven in a non-interlaced manner. The pixel areas of the liquid crystal display panel 8 are two-dimensionally arranged on a transparent substrate, and in the case of this embodiment, the pitch of the pixel areas is a value measured along the horizontal direction or a value measured along the vertical direction. 20 μm. FIG. 9 shows an enlarged structure in the vicinity of the liquid crystal display panel 8 shown in FIG. As shown in FIG. 9, in the case of this embodiment, the R, G, and B pixel regions 8R, 8G, and 8B are striped along the horizontal direction of the screen (the direction perpendicular to the paper surface in FIG. 2). One microlens 7a is assigned to a set of three pixel regions (R, G, and B pixel regions 8R, 8G, and 8B).

  In the present embodiment, the R, G, and B pixel regions 8R, 8G, and 8B are arranged in stripes along the horizontal direction of the screen (the direction perpendicular to the paper surface in FIG. 2). As long as each microlens 7a is assigned to a set of three pixel regions (R, G, and B pixel regions 8R, 8G, and 8B), the R, G, and B pixel regions 8R, 8G and 8B may be arranged in a mosaic.

  The R, G, and B lights that irradiate the liquid crystal display panel 8 are obtained by separating the white light emitted from the light source 1 by the dichroic mirrors 4, 5, and 6, as shown in FIG. It enters the upper microlens array 7 at different angles. By appropriately setting the incident angles of the R, G, and B light to the microlens array 7, as shown in FIG. 9, the microlens 7 appropriately distributes the pixel areas corresponding to the respective wavelength ranges. In the present embodiment, the microlens 7 is designed to have a focal length of 120 μm and an angle formed by each light beam to be 10.02 °. More specifically, the R light is incident on the liquid crystal display panel 8 perpendicularly, and the B light and the G light are incident on the R light at an angle of 10.02 °.

  The dichroic mirrors 4, 5, and 6 have spectral characteristics as shown in FIG. 10, and selectively reflect green (G), red (R), and blue (B) light, respectively. The wavelength range of G light is 520 to 580 nm, the wavelength range of R light is 600 to 650 nm, and the wavelength range of B light is 420 to 480 nm.

  In the present embodiment, the dichroic mirrors 4, 5, 6 and the microlens array 7 are used to collect light of the three primary colors in the corresponding pixel areas. However, other optical means (for example, light diffraction / spectroscopy) are used. A transmission hologram having a function may be used.

  As described above, since the liquid crystal display panel 8 is driven non-interlaced, 60 frames of images are displayed per second, and the time (frame period) T allocated to each frame is 1/60 seconds, that is, T = 1. / 60 (seconds) ≈16.6 (milliseconds). In the case of driving with interlace, the scanning lines in the screen are divided into even lines and odd lines and displayed alternately, so that T = 1/30 (seconds) ≈33.3 (milliseconds). . Further, the time (one field period) assigned to each of the even field and odd field constituting each frame is 1 / 60≈16.6 (milliseconds).

  The projection type image display apparatus according to the present embodiment receives image data including information (data) of each frame image, stores the data of each frame image in a frame memory sequentially, and is based on information selectively read from the frame memory. A subframe image generation circuit 14 that sequentially forms a plurality of subframe images and displays the subframe images on the image display panel 8 in a time-sharing manner. Hereinafter, a method of forming a subframe image in the subframe image generation circuit 14 will be described in detail.

  For example, it is assumed that an image of a certain frame (frame image) is an image as shown in FIG. This frame image is to be displayed in color, and the color of each pixel is determined based on data defining the frame image. In the case of interlace driving, an image of a certain field can be handled in the same manner as the “frame image” in the present specification.

  First, the R, G, and B light data for each pixel is separated from the color display frame data shown in FIG. 11A, as shown in FIGS. 11B, 11C, and 11D. Then, each data of an R image frame, a G image frame, and a B image frame is generated. These data are respectively stored in the R, G, and B frame memories as shown on the left side of FIG.

  In the right part of FIG. 12, display subframes 1 to 3 are shown. According to the present embodiment, in the first one-third period (first subframe period) of a certain frame, the image of the display subframe 1 is displayed on the projection surface. In the next one-third period (second subframe period), the image of the display subframe 2 is displayed, and in the last one-third period (third subframe period), the display subframe 2 is displayed. The image of frame 3 is displayed. In the present embodiment, these three sub-frame images are shifted as shown in FIG. 13 and synthesized while being shifted in time. As a result, the original image shown in FIG. Will be.

  Next, taking the display subframe 1 as an example, the data structure of the subframe image will be described in detail. First, as shown in FIG. 12, the data for the first row pixel area of the display subframe 1 is formed from the data about the first row pixel (R1) stored in the R frame memory. The data for the second row pixel area of the display subframe 1 is formed from data relating to the second row pixel (G2) stored in the G frame memory. The data for the third row pixel area of the display subframe 1 is formed from data relating to the third row pixel (B3) stored in the B frame memory. The data for the fourth row pixel area of the display subframe 1 is formed from data relating to the fourth row pixel (R4) stored in the R frame memory. Thereafter, the data of the display subframe 1 is configured in the same procedure.

  The data of display subframes 2 and 3 are also configured in the same manner as in display subframe 1. For example, in the case of the display subframe 2, the 0th row pixel region data is formed from data relating to the first row pixel (B1) stored in the B frame memory, and the first row pixel region of the display subframe 2 is displayed. The data for use is formed from data relating to the second row pixel (R2) stored in the R frame memory. The data for the second row pixel area of the display subframe 2 is formed from the data relating to the third row pixel (G3) stored in the G frame memory, and the data for the third row pixel area of the display subframe 2 is B. This is formed from data relating to the fourth row pixel (B4) stored in the frame memory.

  In this way, the data read from each of the R, G, and B frame memories are combined in a preset order, whereby the data of each subframe displayed in a time division manner is generated. As a result, each of the subframe data includes information on all the colors of R, G, and B, but each of R, G, and B is spatially one third of the whole. It only has information about the region. More specifically, as is clear from FIG. 12, the display subframe 1 includes data relating to pixels in the first, fourth, seventh, tenth rows of the R image frame and the second, fifth, eighth of the G image frame. , 11... Data relating to the pixels in the row and data relating to pixels in the third, sixth, ninth, twelfth rows of the B image frame. The display subframe 2 includes data relating to pixels in the first, fourth, seventh, tenth row of the B image frame, data relating to pixels in the second, fifth, eighth, eleventh row of the R image frame, and the G image frame. 3, 6, 9, 12,... The display subframe 3 includes data relating to pixels in the first, fourth, seventh, tenth row of the G image frame, data relating to pixels in the second, fifth, eighth, eleventh row of the B image frame, and the R image. Data relating to pixels in the third, sixth, ninth, twelfth row of the frame. As can be seen from FIG. 12, the total number of rows in the pixel area of the image display panel is two rows larger than the total number of rows of pixels constituting one subframe image. These two rows function as an optical shift margin.

  In order to reproduce the original image frame, the first row of the R image frame, the first row of the B image frame, and the first row of the G image frame must be synthesized. As shown in FIG. 12, these pieces of information are assigned to the first row, the 0th row, and the −1 row in the display subframes 1, 2, and 3. Therefore, on the projection surface, these subframe images are displayed with a display subframe 2 shifted by one pixel with respect to the display subframe 1, and the display subframe 3 is displayed with respect to the display subframe 1. Display is shifted by two pixels. That is, in each pixel on the projection plane, three display subframes are sequentially shifted and displayed. The image shift between the sub-frames is performed by the optical shift element 10.

  Note that the method for generating subframes and the time-division display method for generated subframes are not limited to the above-described example. As disclosed in Patent Document 6, time-division display may be performed using three or more subframes.

  Next, the optical shift element 10 will be described. FIG. 14 schematically shows a first optical shift unit 10 ′ used in the optical shift element 10. As shown in FIG. 14, the optical shift unit 10 'includes a modulation unit g1, a first light guide unit g2, and a second light guide unit g3.

  The modulation unit g1 modulates the polarization direction of the light incident perpendicularly to the modulation unit g1. This light corresponds to a sub-frame image modulated by the image display panel 8 as shown in FIG. Specifically, the modulation unit g1 switches the polarization direction of light between two directions orthogonal to each other. For this reason, the modulation unit g1 includes a liquid crystal layer 203 and a liquid crystal cell having a pair of transparent electrodes 201 and 202 sandwiching the liquid crystal layer 203, and an appropriate voltage can be applied to the entire liquid crystal layer 203. For example, when a TN liquid crystal having a positive dielectric anisotropy Δε is used as the liquid crystal layer 203 and a voltage is applied, the liquid crystal molecules are aligned in the direction of the electric field, so that the polarization direction of incident light is not rotated, and the voltage is changed. When not applied, the polarization direction of incident light is rotated by 90 ° by causing the liquid crystal molecules to be oriented 90 ° twisted.

  The first light guide portion g2 is in contact with the substrate 101 on which a plurality of micro prisms 101b having inclined surfaces 101a are provided on one main surface and the micro prism 101b so as to form a micro prism array, and the grooves of the micro prisms 101b are formed. And a birefringent material 102 provided so as to be buried. Each microprism 101b extends in a direction perpendicular to the direction in which the optical axis is shifted (z direction in FIG. 14), and the inclined surface 101a of the microprism 101b is the other of the substrate 101 where the microprism 101b is not provided. The main surface 101c is inclined by an angle θ. The birefringent material 102 has a different refractive index depending on the polarization direction of incident light. In this embodiment, the substrate 101 is formed of a polymer resin, and liquid crystal is used for the birefringent material 102. Therefore, in order to hold the birefringent material 102, the first light guide portion g2 further includes the first transparent substrate 103, and the birefringent material 102 is sandwiched between the substrate 101 and the first transparent substrate 103. Preferably it is. Here, “transparent” means transmitting light used by a device to which the optical shift element 10 is applied, and transmitting visible light when the optical shift element 10 is used in a projection image display apparatus. Say.

For example, the substrate 101 having the minute prism 101b is formed of a thermosetting polymer resin having a refractive index of 1.531, the angle θ of the prism inclined surface 101a is 5 degrees (the apex angle is 85 degrees), and the prism pitch is. It is designed to be 200 μm. Such a substrate 101 can be easily manufactured by curing a thermosetting polymer resin using a mold. Birefringence refractive material 102 is n _e = 1.580, a liquid crystal of n _o = 1.482. A glass plate having a refractive index of 1.52 is used for the first transparent plate 103. Alignment treatment is performed on at least one of the inclined surface 101a of the microprism 101b and the surface in contact with the birefringent material 102 of the first substrate 103 so that the liquid crystal of the birefringent material 102 is aligned in parallel with the extending direction (z direction) of the microprism 101b. Is preferably applied.

  In the first light guide portion g2 configured in this way, the birefringent material 102 exhibits a refractive index of 1.580 with respect to light having a polarization direction (z direction) parallel to the direction in which the microprism 101b extends, A refractive index of 1.482 is indicated for light having a polarization direction (y direction) perpendicular to the direction in which the microprism 101b extends. For this reason, in the first light guide part g2, the refractive index difference between the inclined surface 101a of the microprism 101b and the birefringent material 102 differs depending on the direction of the polarization plane of the light incident on the first light guide part g2. Specifically, the refractive index difference for light having a polarization direction parallel to the direction in which the microprism 101b extends is +0.049 (1.580-1.531), and the polarization direction is perpendicular to the direction in which the microprism 101b extends. The difference in refractive index with respect to the light having − is −0.049 (1.482−1.531). Light incident at a non-perpendicular incident angle on the birefringent material 102 is refracted at a rate corresponding to this refractive index difference according to Snell's law.

  The second light guide part g3 also includes the substrate 101 provided with a plurality of microprisms 101b and the birefringent material 102, and has the same structure as the first light guide part g2. When a liquid crystal is used as the birefringent material 102, it is preferable to further include a first transparent substrate 103 in order to hold the liquid crystal, similarly to the first light guide portion g2.

  In the first optical shift unit 10 ′, the modulation unit g1 and the first light guide unit g2 are such that light incident on the first optical shift unit 10 ′ is first incident on the modulation unit g1 and transmitted through the modulation unit g1. Are arranged so as to enter the first light guide portion g2. Further, the first light guide part g2 and the second light guide part g3 are arranged so that the inclined surfaces 101a of the respective microprisms 101b are parallel to each other. In this embodiment, in order to adjust the space | interval of the 1st light guide part g2 and the 2nd light guide part g3, the 2nd transparent plate 104 is provided among these. The second transparent plate 104 has a refractive index of 1.52, and is the sum of the second transparent plate 104 and the first transparent plate 103 of the first light guide part g2 and the second light guide part g3. The thickness is adjusted to 3.5 mm.

Next, the operation of the first optical shift unit 10 ′ will be described. When the voltage is applied to the liquid crystal layer 203 and the light of the optical axis l _i having the polarization direction in the y direction is vertically incident on the modulation unit g1 as shown in FIG. 14, the modulation unit g1 has the polarization direction of the incident light. Is not rotated, light having a polarization direction in the y direction is emitted. When this light is incident on the substrate 101 of the first light guide g2, the birefringent material 102 exhibits a refractive index of 1.482 with respect to light having a polarization direction in the y direction. Becomes larger, and light having an optical axis l _{o2 ′} is emitted.

The light emitted from the birefringent material 102 of the first light guide g1 enters the first transparent plate 103 and the second transparent plate 104, and then enters the birefringent material 102 of the second light guide g3. To do. Then, light is refracted again at the interface between the birefringent material 102 and the substrate 101 in the second light guide portion g2. At this time, the refractive index difference between the birefringent material 102 and the substrate 101 is equal to the refractive index difference between the birefringent material 102 and the substrate 101 in the first light guide portion g1, and the signs are reversed. For this reason, light having an optical axis l _o2 parallel to the optical axis l _i of the light incident on the first light guide g1 is emitted from the second light guide g3.

On the other hand, when no light is applied to the liquid crystal layer 203, when the light of the optical axis l _i having the polarization direction in the y direction is incident on the modulation unit g1 as shown in FIG. 14, the modulation unit g1 changes the polarization direction of the incident light. The light with the optical axis l _i having the polarization direction in the z direction is emitted. When this light is incident on the first light guide portion g2, the birefringent material 102 exhibits a refractive index of 1.580 with respect to light having a polarization direction in the z direction, so the refraction angle is smaller than the incident angle. The light having the optical axis l _{o1 ′} is emitted.

The light emitted from the birefringent material 102 of the first light guide g1 enters the first transparent plate 103 and the second transparent plate 104, and then enters the birefringent material 102 of the second light guide g3. To do. Then, light is refracted again at the interface between the birefringent material 102 and the substrate 101 in the second light guide portion g2. At this time, the refractive index difference between the birefringent material 102 and the substrate 101 is equal to the refractive index difference between the birefringent material 102 and the substrate 101 in the first light guide portion g1, and the signs are reversed. For this reason, light having an optical axis l _o1 parallel to the optical axis l _i of the light incident on the first light guide g1 is emitted from the second light guide g3.

As shown in FIG. 14, when the position in the xy plane of the optical axis l _i of the light incident on the first optical shift unit 10 ′ is p0, the light emitted from the first optical shift unit 10 ′ The position p1 of the optical axis l _{01 in} the xy plane is shifted by Δd1 in the + y direction from p0. Further, the position p2 on the xy plane of the optical axis l ₀₂ of the light emitted from the first optical shift unit 10 ′ is shifted by Δd2 from the p0 in the −y direction. That is, the first optical shift unit 10 ′ can emit light with the optical axis selectively shifted by the operation of the modulation unit g1.

The shift amounts Δd1 and Δd2 of the optical axis are the optical characteristics including the refractive index of the substrate 101, the angle θ of the inclined surface of the microprism 101b, the refractive index of the birefringent material, the first transparent substrate 103 and the second transparent substrate 104. By appropriately adjusting the refractive index, thickness, etc., it can be set to an arbitrary value, and the shift amounts Δd1 and Δd2 can be made equal. That is, the position of the optical axis l _{o1 and} the position of the optical axis l _o2 of the emitted light can be arranged symmetrically with respect to the position of the optical axis l _i of the incident light. Thereby, the optical path length of the light which takes two shift positions in 1st optical shift part 10 'can be made equal.

  In the present embodiment, Δd1 and Δd2 can be set to 10 μm, respectively, by making the refractive indexes of the first transparent plate 103 and the second transparent plate 104 equal and making the total thickness thereof 3.5 mm. it can.

  In the case where the refractive indexes of the birefringent material 102 and the first transparent plate 103 of the first light guide portion g2 and the second light guide portion g3 are different, the birefringent material 102 and the first transparent plate 103 are used. The light is also refracted at the interface. However, since light passes through the interface between the birefringent material 102 and the transparent plate 103 and the interface between the transparent plate 103 and the birefringent material 102, the refraction generated at each interface is canceled out, and the first light guide portion g2 The light parallel to the light emitted from the birefringent material 102 enters the birefringent material 102 of the second light guide g3. However, the optical axis of the light incident on the birefringent material 102 of the second light guide part g3 is shifted from the position of the optical axis of the light emitted from the birefringent material 102 of the first light guide part g2. In the present embodiment, since the shift amount is negligible, the second light guide unit does not shift the optical axis of the light emitted from the birefringent material 102 of the first light guide unit g2. It is assumed that the light is incident on the birefringent material 102 of g3. When the shift amount cannot be ignored, the refractive index and thickness of the first transparent plate 103 and the second transparent plate 104 are adjusted, or the first light guide part g2 and the second light guide part. Δd1 and Δd2 can be made equal by adjusting the refractive index of the substrate 101 of g3 and the angle of the inclined surface 101a (that is, by considering the optical distance).

  Also, the second light guide part g2 and the second light guide part g3 are arranged through the space 106 filled with air or other gas without providing the second transparent plate 104 as shown in FIG. May be. The first light guide part g2 and the second light guide part g3 are arranged so that the respective birefringent materials 102 face each other, but the first light guide part g2 or the second light guide part g3 has a plurality. You may arrange | position so that the refractive material 102 may oppose the board | substrate 101 of the 2nd light guide part g3 or the 1st light guide part g2.

  In the present embodiment, an appropriate voltage can be collectively applied to the entire liquid crystal layer 203 of the modulation unit g1 in the optical shift unit 10 ′. In addition, it is more preferable to sequentially apply a voltage to the corresponding liquid crystal layer region in synchronization with scanning of the image display panel.

  As described above, the first optical shift unit 10 ′ can shift the image by shifting the optical axis of the incident light as shown in FIG. 14. That is, two different positions can be selected. However, as described with reference to FIGS. 8 to 13, in order to superimpose the R, G, and B light on the projection surface, the sub-frame image modulated by the image panel is equivalent to one pixel and 2 pixels. The pixel needs to be shifted on the projection surface, so the optical shift element 10 must be able to select at least three different positions.

  For this reason, the optical shift element 10 of the present embodiment includes two optical shift units 10 ′ as shown in FIG. 14. If these two optical shift units are a first optical shift unit 10'a and a second optical shift unit 10'b, by arranging them in series on the optical path as shown in FIG. The image can be shifted so that different positions can be selected. According to the optical shift element 10, the modulation unit g1 of the first optical shift unit 10′a located on the light incident side on the optical path and the modulation unit of the second optical shift unit 10′b located on the light emission side. According to the voltage applied to each liquid crystal layer of g1, four different positions on the projection surface can be selected.

  FIG. 16 shows an optical shift element capable of selecting positions of three optical axes. As shown in the drawing, the light transmitted through the first optical shift unit 10′a is arranged to transmit through the second optical shift unit 10′b, and the first optical shift unit 10′a and the second optical shift unit 10′a are arranged. The shift amount Δd1 + Δd2 in the shift unit 10′b is made equal. In order to select four positions, the shift amount Δd1 + Δd2 of the position of the optical axis that can be selected in the first optical shift unit 10′a and the second optical shift unit 10′b is 2: 1 or 1: 2. Design so that

  In order to make the optical axis shift amount Δd1 + Δd2 different between the first optical shift unit 10′a and the second optical shift unit 10′b, as described above, the refractive index of the substrate 101, the microprism 101b The angle θ of the slope, the optical characteristics including the refractive index of the birefringent material, the refractive indexes and thicknesses of the first transparent substrate 103 and the second transparent substrate 104 may be adjusted. These values may be different between the first optical shift unit 10'a and the second optical shift unit 10'b.

  For example, in order to set the shift amount Δd1 + Δd2 of the position of the optical axis that can be selected in the first optical shift unit 10′a and the second optical shift unit 10′b to 2: 1 or 1: 2, the first optical shift unit The distance between the slope of the micro prism of the first light guide g2 in the shift unit 10'a and the slope of the micro prism of the second light guide g3 is the first light guide in the second optical shift unit 10'a. The first transparent substrate 103 and / or the second transparent substrate 103 and / or the second transparent substrate 103 so that the distance between the slope of the microprism of the part g2 and the slope of the microprism of the second light guide part g3 is substantially twice or about 1/2 times. The thickness of the transparent substrate 104 may be adjusted. Alternatively, the angle at which the optical axis is refracted on the slope of the micro prisms of the first and second light guides in the first optical shift unit is the first and second guides in the second optical shift unit. The angle θ of the slope of the microprism 101b and the refractive index difference between the substrate and the birefringent material are adjusted so that the angle of refraction of the optical axis is substantially twice or about ½ of the angle of refraction of the optical prism on the slope of the optical part. May be.

  In addition, the inclination direction of the slopes of the micro prisms of the first light guide part g2 and the second light guide part g3 in the first optical shift part 10'a and the first guide in the second optical shift part 10'a. The inclination direction of the inclined surfaces of the microprisms of the light part g2 and the second light guide part g3 may be different. That is, with respect to the optical axis of the incident light, the inclination direction of the slopes of the micro prisms of the first light guide part g2 and the second light guide part g3 in the first optical shift part 10'a and the second optical The first optical shift unit 10′a and the second optical shift are symmetric with respect to the inclination direction of the slopes of the micro prisms of the first light guide unit g2 and the second light guide unit g3 in the shift unit 10′a. The part 10′b may be arranged.

  Three (or four) different positions to be selected are the voltage application state (ON / OFF) to the modulation unit g1 (light incident side) of the first optical shift unit 10′a and the second optical shift unit 10. It is determined by a combination of voltage application states (ON / OFF) with respect to the modulation unit g1 (light emission side) of 'b, that is, selection of the polarization direction in each liquid crystal layer.

  Thus, according to the present embodiment, as shown in FIG. 14, the optical path in the first light guide g2 is symmetrical with respect to the optical axis of the incident light, regardless of the selection of the polarization direction in the modulator g1. Become. For this reason, the optical path lengths transmitted through the optical shift element are equal regardless of the shift position. As a result, a projection type image display apparatus capable of projecting a high-quality image without deterioration in image quality is realized.

  Further, since the shift amount of the optical axis in the optical shift element can be set by various parameters such as the thickness and refractive index of the components constituting the optical shift element, the shift amount can be easily adjusted. Since a large crystal such as quartz or lithium niobate is not used, the optical shift element can be manufactured at a low cost and the design can be easily changed.

  Furthermore, the optical shift unit of the optical shift element of the present invention switches the polarization direction of the light incident on the light guide unit using the micro prism by the modulation unit. Since only the polarization direction of light needs to be switched in the modulation unit, the modulation unit can be configured by a simple liquid crystal cell.

  As described above, in the first optical shift unit 10′a and the second optical shift unit 10′b of the optical shift element 10, the distance between the first light guide unit g2 and the second light guide unit g3. The first transparent plate for holding the birefringent material and the second transparent plate that defines the above may be configured by one transparent plate. Specifically, as shown in FIG. 17, in the first optical shift unit 10′a and the second optical shift unit 10′b, between the first light guide unit g2 and the second light guide unit g3. A transparent plate 105 is provided, and the birefringent material 102 of the first light guide portion g2 and the birefringent material 102 of the second light guide portion g3 are in contact with both main surfaces of the transparent plate 105 and sandwich the transparent plate 15 therebetween. One light guide part g2 and second light guide part g3 may be arranged. In this case, in order to align the liquid crystal used as the birefringent material 102 in a predetermined direction, both main surfaces of the transparent plate 105 may be subjected to an alignment process. By adopting such a configuration, the number of steps of laminating the transparent plate can be reduced, and the manufacturing time and the manufacturing cost can be reduced.

(Second Embodiment)
A second embodiment of the optical shift element according to the present invention will be described. As shown in FIG. 18, the optical shift element 11 includes a first optical shift unit 11′a and a second optical shift unit 11′b. Each of the first optical shift unit 11′a and the second optical shift unit 11′b includes a modulation unit g1, a first light guide unit g2, and a second light guide unit g3. Although the structure of the modulation unit g1 is not shown in detail in the figure, it has the same structure as the modulation unit of the first embodiment.

  Each of the first light guide part g2 and the second light guide part g3 includes a substrate 106 on which a plurality of microprisms are formed and a birefringent material 107. The substrate 106 and the birefringent material 107 have the same structure as the substrate 101 and the birefringent material 102 of the first embodiment except that the materials constituting the substrate 106 and the birefringent material 107 are different. In this embodiment, the substrate 106 is made of a polymer resin, and the birefringent material 107 is made of a UV light curable polymer liquid crystal.

  The first optical shift portion 11′a and the second optical shift portion 11′b further include a transparent plate 108, and the birefringence material 107 of the first light guide portion g2 and the birefringence of the second light guide portion g3. The first light guide portion g2 and the second light guide portion g3 are arranged so that the material 107 is in contact with both main surfaces of the transparent plate 108 and sandwiches the transparent plate 108 therebetween.

More specifically, the substrate 106 having microprisms is formed of a polymer resin having a refractive index of 1.567, the angle of the slope of the prism is 5 degrees (the apex angle is 85 degrees), and the prism pitch is 200 μm. Designed to be The birefringent material 107 is a UV light curable polymer liquid crystal having a refractive index of n _e = 1.580 and n _o = 1.482 at the time of curing. As the transparent plate 108, a glass plate having a refractive index of 1.52 is used.

  Similar to the first embodiment, the birefringent material 107 exhibits a refractive index of 1.580 for light having a polarization direction (z direction) parallel to the direction in which the microprism extends, and is perpendicular to the direction in which the microprism 101b extends. A refractive index of 1.482 is shown for light having a different polarization direction (y direction). For this reason, in the first light guide part g2, the difference in refractive index between the inclined surface 106a of the micro prism and the birefringent material 107 differs depending on the direction of the polarization plane of the light incident on the first light guide part g2. The refractive index difference for light having a polarization direction parallel to the direction in which the microprism extends is +0.013 (1.580-1.567), and the refractive index for light having a polarization direction perpendicular to the direction in which the microprism 101b extends. The difference is -0.085 (1.482-1.567). The light incident on the birefringent material 107 is refracted at a rate corresponding to this refractive index difference according to Snell's law.

  As in the first embodiment, the first light guide part g2 and the first light guide part g3 are arranged so that the slopes of the respective prisms are parallel as shown in FIG. A first optical shift unit 11′a of the optical shift element is configured. The second optical shift unit 11'b is configured similarly. In the first optical shift unit 11′a and the second optical shift unit 11′b, the directions of the inclined surfaces (light incident surfaces) of the micro prisms of the first light guide unit g2 and the second light guide unit g3 are set. Each may be reversed.

In the first optical shift unit 11′a and the second optical shift unit 11′b, the optical axis of the light emitted by adjusting the distance between the first light guide unit g2 and the first light guide unit g3 Can be easily adjusted. In the present embodiment, a glass plate having a thickness of 2.225 mm and a refractive index of 1.52 of the transparent plate 108 is used as the transparent plate 108. Accordingly, when light having a polarization direction in the y direction is emitted from the modulation unit g1, the optical axis l _o2 of the light emitted from the second light guide unit g3 is relative to the optical axis l _i of the incident light. When light having a polarization direction in the z direction is emitted from the modulation unit g1 by shifting Δd2 = 3.7 μm, the optical axis l _o1 of the light emitted from the second light guide unit g3 is the optical axis of the incident light. Δd1 = 16.4 μm is shifted with respect to l _i .

  Thus, in the present embodiment, the positions of the optical axes of the two outgoing lights that are selectively shifted by the operation of the modulation unit g1 are asymmetric with respect to the position of the incident light. However, since the light is incident at an incident angle that is not perpendicular to the birefringent material using a microprism, it becomes possible to shift the position of the optical axis of the outgoing light with respect to the position of the optical axis of the incident light, The optical path length difference can be reduced as compared with the prior art. As described in the first embodiment, the shift amounts Δd1 and Δd2 of the optical axis are the optical characteristics including the refractive index of the substrate 106, the angle of the inclined surface of the microprism, the refractive index of the birefringent material, and the refraction of the transparent substrate 108. It can be set to an arbitrary value by appropriately adjusting the rate and thickness. In addition, the first light guide part g2 and the second light guide part g3 may be disposed with a gap instead of the substrate 106.

  The arrangement of the first optical shift unit 11′a and the second optical shift unit 11′b and the shift amounts in the first optical shift unit 11′a and the second optical shift unit 11′b are the same as those in the first embodiment. It can be set in the same way. In particular, when the optical axis shift amount Δd1 + Δd2 in the first optical shift unit 11′a and the second optical shift unit 11′b is set to 2: 1, the optical axis is driven to shift to four positions. Thus, the optical path length difference can be further reduced. In order to set the shift amount in this manner, for example, the angle of the inclined surface of the micro prism is made different between the first optical shift unit 11′a and the second optical shift unit 11′b, and the first optical The inclined surface of the minute prism of the shift unit 11′a and the inclined surface of the minute prism of the second optical shift unit 11′b may be made non-parallel.

  As described above, in the optical shift element of the present embodiment, the optical path length difference of the light transmitted through the optical shift element is smaller than the conventional one. For this reason, when the optical shift element of the present embodiment is used in the projection type image display apparatus, it is possible to display a higher quality image with less deterioration of image quality than in the past. Compared to the first embodiment, since the substrate having the microprism is formed of a photo-curing type resin, it is possible to reduce variations in optical performance such as heat shrinkage in the manufacturing process, and industrially shift optically. Suitable for mass production of devices.

(Third embodiment)
A third embodiment of the optical shift element according to the present invention will be described. As shown in FIG. 19, the optical shift element 12 includes a first optical shift unit 12′a and a second optical shift unit 12′b. Each of the first optical shift unit 12′a and the second optical shift unit 12′b includes a modulation unit g1, a first light guide unit g2, and a second light guide unit g3. The distance between the first light guide part g2 and the second light guide part g3 is adjusted by the transparent plate 111.

  Each of the first light guide part g2 and the second light guide part g3 includes a substrate 109 on which a plurality of microprisms are formed and a birefringent material 110. The substrate 109 and the birefringent material 110 have the same structure as the substrate 101 and the birefringent material 102 of the first embodiment except that the materials constituting the substrate 109 and the birefringent material 110 are different. In the present embodiment, both the substrate 109 and the birefringent material 110 are made of UV light curable polymer liquid crystal.

More specifically, the substrate 109 having a micro prism is formed of a UV light curable polymer liquid crystal having a refractive index of n _e = 1.580 and n _o = 1.482, and the angle of the slope of the prism is 5 It is designed so that the pitch (degree of apex is 85 degrees) and the pitch of the minute prisms is 200 μm. Birefringent material 110 is n _e = 1.580, using a UV light curable polymer liquid crystal having a refractive index of n _o = 1.482. The UV light curable polymer liquid crystal constituting the substrate 109 is preferably cured, but the UV light curable polymer liquid crystal constituting the birefringent material 110 is not necessarily cured. When it is not cured, it is preferable that at least one of the surface of the transparent plate 111 and the inclined surface of the micro prism of the substrate 109 is subjected to orientation treatment.

  The optical axis of the UV photocurable polymer liquid crystal constituting the substrate 109 is the direction in which the microprism extends (perpendicular to the z direction, and the optical axis of the UV photocurable polymer liquid crystal constituting the birefringent material 110 is the microprism. Therefore, the absolute value of the difference in refractive index at the interface between the substrate 109 and the birefringent material 110 is equal regardless of the polarization direction of the light emitted from the modulator g1. When the polarization direction of the light emitted from the part g1 is parallel to the y-axis direction, the refractive index difference is +0.098 (1.580-1.482), and the polarization direction of the light emitted from the modulation part g1 is In the case of being parallel to the z-axis direction, the refractive index difference is −0.098 (1.482-1.580), and the light incident on the birefringent material 110 has this refractive index difference according to Snell's law. Refracts at a corresponding rate. The positions of the optical axes of the two outgoing lights that are selectively shifted by the operation of the modulator g1 are symmetric with respect to the position of the optical axis of the incident light, and the shift amounts Δd1 and Δd2 are equal, regardless of the shift position. The optical path lengths in the first optical shift unit 12′a and the second optical shift unit 12′b are equal, and as a result, a projection-type image display device capable of projecting a high-quality image without deterioration in image quality. Is realized.

  The present invention is applied to a projection type image display apparatus using a display element other than a liquid crystal display element, such as a digital mirror device (DMD), for an image display panel, including a projection type image display apparatus using a liquid crystal panel. Can do. The present invention can also be applied to a direct-view image display device such as a head-mounted display.

  Furthermore, the optical shift element of the present invention can be applied to various devices in which the function of shifting the optical axis is used.

It is a figure which illustrates typically operation | movement of the conventional field sequential projection type image display apparatus. It is a figure which shows typically the structure of the conventional optical shift element. It is a figure explaining operation | movement of the conventional optical shift element shown in FIG. It is another figure explaining operation | movement of the conventional optical shift element shown in FIG. It is a figure explaining operation | movement of the other conventional optical shift element. It is another figure explaining operation | movement of the conventional optical shift element shown in FIG. It is a figure which shows typically the structure of the other conventional optical shift element. 1 is a schematic diagram showing a projection type image display apparatus according to a first embodiment of the present invention. It is sectional drawing which expands and shows the liquid crystal display panel vicinity of the projection type image display apparatus shown in FIG. It is a graph which shows the spectral characteristics of the dichroic mirror of the projection type image display apparatus shown in FIG. (A) to (d) is a diagram illustrating a method of generating a color-specific image frame from an original image frame. It is a figure explaining the method to produce | generate three display sub-frames from an image frame classified by color. It is a figure which shows the aspect of a display sub-frame shift. It is a schematic diagram which shows the structure of the 1st optical shift part of the optical shift element used for the projection type image display apparatus shown in FIG. It is a schematic diagram which shows the modification of the optical shift part shown in FIG. It is a schematic diagram which shows the structure of the optical shift element used for the projection type image display apparatus shown in FIG. It is a schematic diagram which shows the modification of the optical shift element shown in FIG. It is a schematic diagram which shows the structure of the optical shift element by the 2nd Embodiment of this invention. It is a schematic diagram which shows the structure of the optical shift element by the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Spherical mirror 3 Condenser lens 4, 5, 6 Dichroic mirror 7 Micro lens array 8 Liquid crystal display panel 9 Field lens 10 Optical shift element 10 'Optical shift part 10'a 1st optical shift part 10'b 2nd optical Shift portion 101, 106, 109 Substrate 101a Slope 101b Micro prism 102, 107, 110 Birefringent material 103 First transparent plate 104 Second transparent plate 105, 108, 111 Transparent plate

Claims (17)

An optical shift element including a first optical shift unit capable of emitting light by selectively shifting the optical axis to first and second positions with respect to the position of the optical axis of incident light,
The first optical shift unit includes:
A modulator that modulates the polarization direction of incident light;
A plurality of microprisms having inclined surfaces are provided on a substrate provided on one main surface, and a first birefringent material and a second birefringent material are arranged so as to be in contact with the plurality of microprisms and have different refractive indexes depending on the polarization direction of light. A light guide part,
Including
The first and second light guide sections so that light transmitted through the modulation section enters the first light guide section, and the inclined surfaces of the micro prisms of the first and second light guide sections are parallel to each other. Is an optical shift element. Each of the first and second light guide parts further includes a first transparent plate whose main surface is subjected to orientation treatment,
2. The optical shift element according to claim 1, wherein the birefringent material is a liquid crystal material, and the birefringent material is sandwiched between the substrate and the transparent plate so as to be in contact with the main surface subjected to the alignment treatment. .   The first optical shift unit further includes a second transparent plate, and the second transparent plate sandwiches the second transparent plate so that the first transparent substrate of the first and second light guide units sandwiches the second transparent plate. The optical shift element according to claim 2, wherein the transparent plate and the first and second light guide portions are integrally arranged.   The first optical shift unit further includes a transparent plate, and the transparent plate and the first and second guides are arranged so that the birefringent materials of the first and second light guide units sandwich the transparent plate, respectively. The optical shift element according to claim 1, wherein the optical portions are integrally arranged.   The optical shift element according to claim 4, wherein an area of the transparent plate in contact with the birefringent material is subjected to an alignment treatment, and the birefringent material is a liquid crystal material.   The optical shift element according to claim 5, wherein the birefringent material is a polymer liquid crystal.   The optical shift element according to claim 1, wherein the first position and the second position are symmetrical with respect to a position of an optical axis of incident light.   The optical shift element according to any one of claims 1 to 7, wherein an optical path length from entering the first optical shift unit to exiting is equal regardless of a shift position of the optical axis.   The optical shift element according to any one of claims 1 to 8, wherein the birefringent materials of the first and second light guide portions have an optical axis parallel to a ridge line direction of the microprism. A second light that is incident on the light emitted from the first optical shift unit and that can emit light by selectively shifting the optical axis to the first and second positions with respect to the position of the optical axis of the incident light. The optical shift unit of
The optical shift element according to claim 1, wherein the second optical shift unit has the same structure as the first optical shift unit.   The direction of the slopes of the micro prisms of the first and second light guides in the first optical shift unit, and the slope of the micro prisms of the first and second light guides in the second optical shift unit The optical shift element according to claim 10, which is symmetrical with respect to an optical axis of light incident on the first optical shift unit.   The distance between the slopes of the micro prisms of the first and second light guides in the first optical shift unit is the slope of the micro prisms of the first and second light guides in the second optical shift unit. 12. The optical shift element according to claim 10, wherein the optical shift element is about twice or about ½ of the distance.   The optical shift element according to claim 10 or 11, wherein an optical characteristic of the birefringent material or an inclination angle of a slope of the microprism in the first optical shift unit and the second optical shift unit are different.   The angle at which the optical axis is refracted on the slopes of the micro prisms of the first and second light guide portions in the first optical shift portion is the first and second light guide portions in the second optical shift portion. The optical shift element according to claim 13, which is about twice or about ½ of the angle at which the optical axis is refracted at the slope of the microprism.   The optical according to any one of claims 10 to 14, wherein the birefringent material of the first and second light guide portions in the second optical shift portion has an optical axis parallel to a ridge line direction of the microprism. Shift element.   The optical shift element according to claim 1, wherein the modulation unit includes a liquid crystal cell that modulates a deflection direction of light according to an applied voltage. A light source;
An image display panel having a plurality of pixel regions each capable of modulating light;
Light control means for separating light from the light source into light of a plurality of wavelength regions and condensing the light of the separated wavelength regions in a corresponding pixel region of the plurality of pixel regions according to the wavelength region When,
An optical system for forming an image on a projection surface by light modulated by the image display panel;
A circuit for generating data of a plurality of sub-frame images from data of each frame image constituting the image, and displaying the plurality of sub-frame images in a time division manner by the image display panel;
An optical shift element that shifts a subframe image selected from the plurality of subframe images displayed by the image display panel on the projection surface;
A projection-type image display device comprising:
A projection-type image display device, wherein the optical shift element is an optical shift element defined in any one of claims 1 to 16.

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