JP2004317958A - Image display device and reflection type light valve element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve contrast by reducing the number of light beams whose polarization is canceled or reducing polarization canceling amount out of a plurality of light beams whose incident angles are different. <P>SOLUTION: A microlens 18 has such lens surface shape that a direction where it has curvature is limited to only one direction. The direction where it has the curvature is a direction X, and it does not have the curvature in a direction Y. By setting the lens surface in such a way, the contrast is improved by about 50%. The area of a surface having a surface inclined component where the polarization is canceled in the case of refraction on the lens surface of the lens 18 is reduced. Therefore, an effect that the contrast is improved is obtained by reducing the number of light beams whose polarization is canceled or reducing the polarization canceling amount out of a plurality of light beams whose incident angles are different. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates mainly to a reflection type light valve element and a projection type image display device using the reflection type light valve element, and in particular, a pixel shift display means for projecting and displaying a larger number of pixels than the number of pixels of the light valve. And a liquid crystal projector using a pixel reduction projection unit for projecting a projection image of a pixel of the light valve at a magnification smaller than the projection magnification of the entire screen. Can also be included.
[0002]
[Prior art]
Even in a general image projection apparatus without a pixel reduction system using a microlens array, there is a problem of a decrease in contrast. The factors and countermeasures are disclosed in, for example, JP-A-2003-021807 (Patent Document 1) and JP-A-10-142691 (Patent Document 2). These mention the problem that in a polarizing beam splitter (PBS) or a polarizer, ideally, the polarization state of a light beam to be transmitted / reflected 100% deviates from the ideal state, resulting in a decrease in contrast. . However, these documents do not mention the causes and countermeasures of a decrease in contrast when performing pixel reduction or pixel shift display.
[0003]
There are many known techniques in which a light valve and a microlens array are stacked, but these techniques aim to improve the aperture efficiency of the light valve, not to reduce the pixels. Japanese Patent Application Laid-Open No. 2000-047258 (Patent Document 3) discloses a device in which a gap between lens openings of a microlens array or a crosstalk prevention slit layer is provided between a microlens array plate and a light valve surface. However, this is intended to improve the image contrast by blocking the flare light, and does not mention the polarization state and contrast of light.
[0004]
Regarding the pixel shift element described later in the present invention, for example, the configuration operation of the pixel shift element using the vertical alignment type ferroelectric liquid crystal and the image quality improvement effect by performing the pixel shift display are disclosed in SID2002, IDW2002, and the like. However, there is no mention of contrast performance.
[0005]
2. Description of the Related Art In a projector device that projects a display image on a panel of a light valve onto a screen by an enlargement optical system, the definition of a projected image has been improved by increasing the number of pixels of the projected image. The most common method for increasing the definition of a projected image is to increase the number of pixels of the light valve itself. However, in order to increase the number of pixels of the light valve, it is necessary to reduce the size of one pixel. This affects the cost of the light valve. To increase the number of pixels without reducing the pixel size, the area of the light valve may be increased. However, it is difficult to reduce the illumination optical system and the projection optical system by increasing the area of the light valve. It is important to reduce the size and weight of the projection device, and the size of the light valve element has been reduced.
[0006]
As another method, a method has been proposed in which the number of pixels of an enlarged projected image is apparently increased without increasing the number of pixels of the light valve.
This is a method of projecting and displaying a position where a pixel of a light valve is projected by a small amount. Hereinafter, this method is referred to as pixel shift display.
[0007]
To perform pixel-shifted display, display information of one frame when pixel-shifted display is not performed is divided into two or more pieces of sub-frame display information, and the display information of the divided sub-frames is slightly shifted in display position and projected. I do.
[0008]
As a method of shifting, there are a method of statically overlapping and projecting a plurality of different screens formed of subframes and a method of projecting and displaying these in a time-division manner. The shift amount is set smaller than the size of the projection pixel. It is better to shift about half a pixel.
[0009]
As a method of shifting, in the case of static overlapping projection display, there is a method of using a plurality of projection devices and projecting an image of a divided sub-frame. In the case of dynamic time-division projection display, a sub-frame image is time-divisionally projected and displayed using active pixel shifting means.
[0010]
In the case of time-division projection display, the projection position of the image is moved on the projection plane at a higher speed than the frequency at which the image is displayed. Assuming that the standard frame frequency is 60 Hz, the display frequency of each sub-frame is 120 Hz in the case of dividing the image into two sub-frames and displaying the shifted pixels. Similarly, when the image is divided into four sub-frames and displayed with shifted pixels, the display frequency of each sub-frame is 240 Hz.
[0011]
As a method of moving the display position of an image, for example, a laminated component of a light-transmitting substrate, an ITO electrode layer, a liquid crystal layer, an ITO electrode layer, and a light-transmitting substrate is placed in an optical path of a projection system, and ITO is placed on the liquid crystal layer. There is a method in which the orientation direction of the liquid crystal is electrically switched by a method of applying an electric field by an electrode, and the optical path passing through the liquid crystal layer is shifted in parallel by a birefringence effect. By performing a switching operation such that the direction of the long axis of the vertical alignment type ferroelectric liquid crystal is tilted ± with respect to the optical axis in a plane including the optical axis, the emission position of the light beam passing through the liquid crystal layer is adjusted to the optical axis. Can be shifted ± in a plane including. The details of such a pixel shift element are described in JP-A-2002-214579 (Patent Document 4). Pixel shift display is also possible by other methods, and there are many disclosed examples.
[0012]
When a pixel of the light valve is projected and displayed, the size of the pixel image of the light valve projected and displayed is (pixel size × projection magnification) in a normal projector device. At this time, the images of the adjacent pixels are projected with almost no gap. Strictly speaking, since there is a gap between the pixels of the light valve, the area of the gap is displayed in black, but the area displayed in black is much thinner than the pixel. If pixel shift display is performed in this state, images of adjacent pixels overlap. For this reason, the image has a blurred outline. The blur of the contour is particularly remarkable in a place where the difference in shading of the image is large. This blur is noticeable when displaying an image with noticeable edges such as characters and drawings.
[0013]
As a method of improving the above-described image blur, there is a method of reducing the size of a pixel on a projection plane. Hereinafter, this is referred to as pixel reduced display.
[0014]
Pixel reduction display does not mean reducing the size of the projection screen itself. Only the size of the pixel image is reduced. When only the size of the pixel image is reduced and displayed, the images of adjacent pixels are projected with a gap. If the pixel is shifted in this state, the problem of overlapping of adjacent pixel images can be solved. Thereby, the blur of the image is eliminated.
[0015]
As means for realizing the above-described pixel reduced display, there is a constitution means in which a microlens is arranged for each pixel of the light valve. That is, this is a configuration means in which the microlens array is configured to be equal to the pixel array of the light valve, and is arranged to face the light valve. A configuration in which the microlens array and the light valve are fixed by an adhesive layer is preferable. If the parameters such as the focal length of the microlens, the refractive index of the adhesive layer, and the layer thickness are properly designed, the reduced image of the pixels of the light valve can be used as an intermediate image by illuminating from the near side of the microlens toward the light valve. Can be generated. When the light valve is a reflection type, the reduced image can be formed in front of the light valve. If the projection optical system is arranged such that the position of the reduced image and the projection plane have an optically conjugate relationship, the reduced image can be enlarged and projected.
[0016]
FIG. 12 is a diagram for explaining the configuration of the above-described projector optical system in more detail. Light from an illumination light source 1 is incident on a PBS (polarization beam splitter) 4 through an integrator optical system 2 and a polarization conversion element 3. The light is reflected by the polarization separation surface 5 of the PBS 4, passes through the retarder 6, and is separated into three colors of R, G, and B by the color separation / synthesis element 7. Here, R is red, G is green, and B is blue. Each of the three color-separated illumination lights forms an optical system that reaches a reflection type light valve 9 (9R, 9G, 9B) via a pixel reduction optical system 8 (8R, 8G, 8B). This is referred to herein as a forward optical system. A 1 / 2λ plate is used as the polarization conversion element 3. The retarder 6 is a phase compensation element, and uses a λλ plate.
[0017]
The reflected light of the reflective light valve 9 returns to the pixel reduction optical system 8, the color separation / synthesis element 7, the retarder 6, and the polarization beam splitter 4 in order, and transmits / reflects the polarization separation surface 5, and the transmitted light is An optical system that reaches the projection plane via the polarization conversion element 10, the pixel shift element 11, and the projection optical system 12 is configured. This is referred to herein as a return optical system. The forward optical system and the backward optical system share the same element. The polarization conversion element 10 has a crossed Nicol arrangement with respect to the polarization conversion element 3.
[0018]
FIG. 13 and FIG. 14 are views showing a cross-sectional configuration of the pixel reduction optical system 8 and the reflection type light valve 9, wherein 13 is a microlens substrate, 14 is a microlens array, and a light transmitting material is used. Can be Reference numeral 15 denotes an adhesive layer, reference numeral 16 denotes a liquid crystal layer of the reflective light valve 9, reference numeral 17 denotes a light valve substrate, and the pixel reduction system 8 and the reflective light valve 9 are bonded by the adhesive layer 15. The Z axis in FIGS. 13 and 14 is set in the optical axis direction of the illumination light beam.
[0019]
The individual microlenses 14 constituting the microlens array 14 are arranged and arranged so as to correspond one-to-one with the pixels on the reflection surface 17 of the reflection type light valve 9. Note that the number of microlenses in FIGS. 13 and 14 is conceptual, and the actual number corresponds to the number of pixels of the reflective light valve 9. In addition, the thickness of each layer is also represented schematically here. For example, the thickness of the microlens 14 is about 10 microns.
[0020]
FIG. 15 is a diagram for explaining the optical system passing through the pixel reduction system 8 and the reflection type light valve 9 shown in FIGS. 13 and 14. First, the illumination light reaches the pixel reduction system 8 on the outward path. The pixel reduction system 8 has openings for a plurality of microlenses, and the illumination light beam is divided into openings. The illumination light is condensed on each microlens surface, and reaches the pixel surface of the reflective light valve 9 via the adhesive layer 15 and the liquid crystal layer 16.
[0021]
On the return path, the light is reflected by the pixel surface of the reflective light valve 9 and passes through the liquid crystal layer 16, the adhesive layer 15, and the pixel reduction optical system 8 again. The reduced image of the pixel of the reflection type light valve 9 is generated above the lens surface of each micro lens 14M in FIG. Further, the backward projection optical system is arranged so that the position of the reduced image and the position of the projection plane are optically conjugate. As a result, the image of the reduced pixel is projected and displayed on the projection plane.
[0022]
The optical system shown in FIG. 15 schematically shows an optical path when a light beam is incident from the top to the bottom of the figure in parallel with the optical axis of the microlens. Actually, since the non-parallel ray components exist in the illumination light, the image at the imaging position I-1 has a predetermined size. Note that the optical conjugate relationship between the pixel reduced image position I-1 and the projection plane is easily understood, and a description thereof will be omitted.
[0023]
In the above optical arrangement, the liquid crystal layer 16 of the reflection type light valve element 9 has a function of rotating the polarization of incident / reflected light. Thus, the amount of light transmitted through the color combining element 7, the retarder 6, the PBS 4, and the polarization conversion element 10 of the return optical system is changed. That is, the brightness of the projected display image is controlled.
[0024]
Here, when the light valve element 9 is turned on / off, that is, the contrast on the projection screen in the light / dark state, there is a problem of a decrease in contrast as described below.
[0025]
The cause of the decrease in contrast exists even when there is no pixel reduction system. For the cause and countermeasures, see, for example, JP-A-2003-021807 (Patent Document 5) and JP-A-10-142691. (Patent Document 6) and the like. In these, a problem that the contrast is reduced due to a light component deviating from an ideal polarization state which should ideally be transmitted / reflected in the PBS or the polarizer is presented. Mentions. However, these disclosures do not mention the cause and countermeasure of the decrease in contrast when performing pixel reduction display. In a broad sense, there is no mention of contrast reduction due to the interposition of the microlens system.
[0026]
In the optical system exemplified above, the optical axis is the Z axis, the S polarization direction is the Y axis, the P polarization direction is the X axis, and the polarization conversion element 3 and the polarization conversion element 10 are usually arranged in a crossed Nicols arrangement. When the illumination light source 1 is a lamp, the illumination light is non-polarized. This is converted into linearly polarized light after passing through the polarization conversion element 3. Assuming that the linearly polarized light is S-polarized light, the light is reflected by the polarization splitting surface 5 of the PBS 4 while maintaining its polarization state, and reaches the reflection type light valve 9. In this state, if the light returns to the polarization separation surface 5 of the PBS 4, ideal contrast characteristics should be obtained. However, in actuality, polarization rotation occurs in each element of the forward path and the return path, and the polarization axis is tilted. Further, the polarization axis becomes elliptically polarized and an extra polarization component is generated, so that the extinction ratio decreases. That is, the contrast is reduced. However, it is described that if the configuration conditions described in JP-A-2003-021807 (Patent Literature 5) and JP-A-10-142691 (Patent Literature 6) are employed, the decrease in contrast due to the above-described causes is improved. .
[0027]
However, the situation is different when a pixel reduction system using a microlens is added. When a micro lens having a radius of curvature of several tens of microns is interposed, the contrast (extinction ratio) is reduced by depolarization.
[0028]
FIG. 16 is a diagram for explaining de-polarization. In a circular sectional view of a lens as shown in FIG. 16A, an optical axis is taken in a direction perpendicular to the plane of the drawing passing through the center of the lens. In the case where the X-axis and the Y-axis are defined on a plane including a plane, for example, as shown in FIG. 16B, when linearly polarized light having a vibrating surface is incident in the same direction as the Y-axis, the coordinates of the light incident position When X ≠ 0 and Y ≠ 0, the polarization axis and the vibration plane of polarized light are inclined. When the incident position M when incident at a position 45 degrees from the X-axis is illustrated, the plane formed by the optical axis and M at M is the incident surface. Is the S component. When an anti-reflection film is provided, not only the polarization axis is tilted, but also elliptically polarized light (FIG. 16 (C)) is generated due to the occurrence of a phase difference. Has been described.
[0029]
However, depolarization is rarely a problem in ordinary lenses. In general optical devices, the lens used has a larger radius of curvature than the micro lens, and the lens used has a shape in which the inclination of the peripheral surface of the lens is not so steep. However, in many cases, the angle of incidence of the light beam on the lens surface is relatively small, and the polarization characteristics do not pose a problem in the performance of the device. In these cases, depolarization is rarely a problem. Good.
[0030]
An example of an apparatus in which depolarization is problematic is a polarizing microscope. In a polarizing microscope, when the light passes through a bright objective lens with a large NA, the disturbance of the polarization information of the light becomes remarkable, so this must be corrected. It is also introduced in pencils (Non-Patent Document 1, 195p) and the like. However, a rectifier configuration measure can be taken only when the optical system is a transmission system. Since the optical system using the reflection type light valve is a recursive optical system, no measures can be taken for the rectifier. Therefore, it is necessary to consider another countermeasure.
[0031]
Therefore, the problem presented in the present invention is a specific problem, and at present, there is no known example referring to the problem.
[0032]
[Patent Document 1]
JP 2003-021807 A
[Patent Document 2]
JP-A-10-142691
[Patent Document 3]
JP 2000-047258 A
[Patent Document 4]
JP-A-2002-214579
[Patent Document 5]
JP 2003-021807 A
[Patent Document 6]
JP-A-10-142691
[Non-patent document 1]
Masaru Tsuruta, "Pencil of Light", published by New Technology Communications, August 20, 1988, p. 186-196, FIG. 25.5.
[0033]
[Problems to be solved by the invention]
The present invention provides a reflective light valve element using a microlens and a reflective light valve element and an image display suitable for improving contrast in a projection type image display device having the above-described pixel reduction function and pixel shift display function. It is intended to provide a device.
[0034]
Strictly speaking, the reflection type light valve element and the pixel reduction element mainly composed of a micro lens can be considered as separate elements. However, since the pixel and the microlens of the reflection type light valve are usually used as a pair, it can be considered that both function as an integrated configuration. Therefore, in the following, the reflection type light valve element will be described as including a pixel reduction optical system. However, a reflection type light valve element having no pixel reduction function, for example, a microlens array is also used for the purpose of improving aperture efficiency. However, the structure of only the pixel reduction element portion in the case of using a microlens array with a configuration capable of obtaining a pixel reduction function is also within the scope of the present invention for the following reasons.
[0035]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a reflective light valve element having at least a reflective light valve element main body and an array of microlenses opposed to each of a plurality of pixels of the reflective light valve element main body. The lens surface of the lens has a curvature in one direction in the lens surface, and is a reflection type light valve element.
[0036]
According to a second aspect of the present invention, in the reflective light valve element having at least a reflective light valve element main body and an array of microlenses opposed to each of a plurality of pixels of the reflective light valve element main body, The lens surface of the lens is a reflective light valve element characterized by having a distribution of curvature in one direction in the lens surface, and differs from the first invention in that it has a distribution of curvature. Things.
[0037]
A third invention is the reflective light valve element according to the second invention, wherein the curvature in the lens surface has a gentler distribution at the periphery than at the center of the lens.
[0038]
According to a fourth aspect, in the reflective light valve element according to any one of the first to third aspects, a direction in which a curvature of the lens surface changes coincides with a polarization axis of light illuminating the reflective light valve element. It is a reflection type light valve element characterized by being used.
[0039]
According to a fifth aspect of the present invention, in the reflective light valve element according to any one of the first to third aspects, the direction in which the curvature of the lens surface changes corresponds to 90 degrees of the polarization axis of light illuminating the reflective light valve element. A reflective light valve element characterized by being used at an angle.
[0040]
According to a sixth aspect of the present invention, there is provided a reflective light valve element having at least a reflective light valve element main body and an array of microlenses opposed to each of a plurality of pixels of the reflective light valve element main body. The lens comprises a lens surface 1 having a curvature in one direction in the lens surface, and a lens surface 2 having a curvature in a direction orthogonal to the direction having the curvature of the lens surface 1. A reflective light valve element.
[0041]
A seventh invention is characterized in that one of the two directions of curvature of the two lens surfaces according to the sixth is used in accordance with the polarization axis of light illuminating the reflective light valve element. A reflective light valve element.
[0042]
According to an eighth aspect, in the reflection type light valve element according to the seventh aspect, at least one of the lens surfaces 1 and 2 has a curvature distribution, that is, the curvature in the lens surface is not uniform. This is a reflection type light valve element.
[0043]
A ninth aspect of the present invention is the reflective light valve element according to the eighth aspect, wherein one of the two lens surfaces having a curvature distribution direction coincides with a polarization axis of the reflective light valve illumination light. A reflective light valve element.
[0044]
A tenth aspect of the present invention is a reflective light valve element having at least a reflective light valve body and an array of microlenses opposed to each of a plurality of pixels of the reflective light valve body. When the center of the lens aperture is O, the optical axis of the lens is the Z axis, and the oscillation direction of the P-polarized light or the S-polarized light is the Y-axis direction, the lens surface of the microlens is ± 45 ° with respect to the Y-axis. The region within the degree is a lens surface having the center O at the peak of the curved surface and having a curvature only in the Y direction, and the other region is a lens surface having the center O at the peak of the curved surface and having a curvature in the X direction. And a reflection type light valve element.
[0045]
According to an eleventh aspect of the present invention, in the tenth reflective light valve element, one of the directions having a curvature of the lens surface is used by matching the reflective light valve element with a polarization axis of illumination light. A reflective light valve element.
[0046]
A twelfth invention provides an illumination light source, an integrator optical system, a linear polarizer 1, and a polarization beam splitter (PBS) having a polarization splitting surface that reflects illumination light that has been linearly polarized by the linear polarizer 1 and converted. Are sequentially arranged, a phase compensator provided on the reflected light path of the polarization separation surface, a color separation prism for separating RGB, and R, G, B components arranged on the exit surface of the color separation prism. An optical system 2 in which reflective light valve elements are sequentially arranged; and a linear polarizer 2 which is arranged in a crossed Nicol arrangement with the linear polarizer 1 and transmits / blocks the reflected light of the reflective light valve transmitted through the PBS. A projection type image display device comprising: a pixel shifting element; and an optical system 3 in which a projection optical system for projecting a display image of the reflection type light valve element is sequentially arranged. Characterized in that it is a reflection type light valve device according to any one of the first to 11, a projection image display device.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in comparison with the related art.
As a conventional reflection type light valve element having a pixel reduction function, it has been proposed that a curvature surface of a microlens has a uniform curvature in a plane perpendicular to an optical axis of the lens. When a light beam enters the curvature surface having this configuration, the light beam is refracted at the curvature surface. At this time, how light is depolarized differs depending on the position and angle at which the light beam enters. As described above, the term “polarization elimination” refers to a phenomenon in which, when a light beam incident on a lens surface is, for example, S-polarized light (linearly polarized light), rotation of the polarization angle occurs due to refraction on the lens surface. Say. If there is a medium boundary having a different refractive index behind the lens surface (the traveling direction of the light), the polarization-rotated light beam is further changed in polarization at this boundary surface, and becomes elliptically polarized. Even if the polarization-rotated and elliptically-polarized light beam controls the polarization of the reflected light beam by switching the liquid crystal of the reflection-type light valve element, the component that should be transmitted through the polarization splitting surface of the retarder polarizer or PBS is not used. Since the component to be reflected or to be reflected is transmitted, the contrast is reduced.
[0047]
Here, when a lamp light source is used, since the luminous body is a finite volume body and the arc length has a finite length, the light incident angle on the lens surface is not uniform but distributed within a predetermined angle. ing. That is, light rays incident on the lens surface are not uniformly parallel to the optical axis of the lens. When the light incident angle factor is added in this way, the depolarization becomes more prominent.
[0048]
In particular, in the case of a reflection type light valve element including a microlens system, when the radius of curvature of the curvature surface of the microlens is set to about several tens of microns and the light beam also enters the periphery of the opening of the microlens, the decrease in contrast due to the depolarization described above is reduced. Become noticeable.
[0049]
Again, the degree of depolarization in the lens plane is greater at the periphery of the lens than at the center. In other words, there is a relationship between a larger incident angle with respect to the lens surface at the peripheral edge and a larger depolarization. This can be confirmed by comparing the contrast when the radius of curvature of the microlens is changed. That is, the contrast decreases when the radius of curvature is small.
[0050]
This indicates that the amount of depolarization can be reduced by relaxing the curvature of the microlens. However, if the curvature is reduced, the effect of pixel reduction is reduced, so that the problem of image blurring when performing pixel-shifted display may arise.
[0051]
On the other hand, in the present invention, as shown in FIG. 1, the shape of the micro lens 18 is a lens surface shape in which the direction having the curvature of the micro lens 18 is limited to only one direction. In FIG. 1, the direction having the curvature is the X direction, and has no curvature in the Y direction. When the lens surface is changed in this way, the contrast is improved by about 50%. According to the present invention, the area of the surface having a surface inclination component that causes depolarization upon refraction on the lens surface of the microlens is reduced. Therefore, the number of depolarized light beams among the plurality of light beams having different incident angles is reduced. Alternatively, the amount of depolarization decreases. Thereby, an effect of improving the contrast can be obtained.
[0052]
When the lens surface shape is as shown in FIG. 1, the incident angle in the Y direction is zero when the vibration surface of the incident light beam is parallel to the Y axis when the lens optical axis of the micro lens is the Z axis. The light beam is no longer depolarized. Light rays incident on the ridgeline 19 connecting the peaks of the curvature of the lens surface are not depolarized if the incident angle in the Y direction is zero or the incident angle in the X direction is zero.
[0053]
On the other hand, in the case of a normal lens surface, a region where depolarization does not occur is incident on the X-axis passing through the center of the lens, and the Y component of the incident angle is zero, or the Y-axis passing through the center of the lens. Only light rays incident on the top and satisfying the condition that the X component of the incident angle is zero are depolarized. From the above comparison, it can be seen that the lens shape shown in FIG.
[0054]
In FIG. 1, the lens surface is marked in the + Z direction. At this time, it is better that the light beam is incident from the −Z direction. Although the illumination light has a predetermined angular distribution, when these are made incident from the −Z side, the light rays are refracted at the boundary between the lens medium and the air layer. Since the refractive index of the lens medium is larger than the refractive index of air, the angular distribution of the illumination light in the lens medium becomes narrow. This has the effect of reducing the depolarization that occurs on the lens surface. The reason will be described below.
[0055]
In the lens surface of FIG. 1, a light ray existing on the XZ plane of FIG. 1 does not cause depolarization even if it has an incident angle component in the X direction. On the other hand, a ray having an incident angle component in the Y direction is depolarized. These rays have less depolarization as the incident angle component in the Y direction is smaller. That is, as described above, the incidence of the light beam on the lens surface from the lens medium becomes smaller than the incidence of the light beam on the lens surface from the air layer. The component in the Y direction is reduced, and the contrast is improved by about 20%.
[0056]
The microlenses 18 in FIG. 1 are actually configured in an array as shown in FIG. The conditions under which each microlens 18 is formed as a pair with the pixel of the reflection type light valve element are the same as those in the related art. FIG. 2 is a schematic diagram, and the actual number of microlenses is the same as the number of pixels of the reflective light valve element.
[0057]
In the case where the lens surface shown in FIG. 1 is used, the contrast differs depending on the arrangement relationship between the direction of curvature and the direction of vibration of the incident light. Preferred arrangement conditions are two states in which the vibration direction is matched or rotated by 90 degrees. As a comparative example, when the incident light beam is rotated by 45 degrees with respect to the Y axis, the unpolarized light beam is incident on the ridge line 19 in FIG. 1 and the X component of the incident angle satisfies the condition of zero. Only.
[0058]
Further, as shown in a region 20 in FIG. 3, when the microlens 18 is formed into an aspherical shape having a smaller radius of curvature at the peripheral portion with respect to the radius of curvature at the central portion, the contrast is further improved by about 10% as compared with a spherical surface. . If the angle of incidence of the light beam at the peripheral edge of the lens is reduced by the aspherical surface, the depolarization effect is suppressed, and the contrast is improved.
[0059]
In FIG. 4, the direction of the curvature of the lens surface is the Y direction. This lens surface is arrayed as shown in FIG.
[0060]
The above has described an example in which the microlens has one lens surface. In this configuration, the operation of reducing and projecting the pixels of the light valve is limited to only one direction. For example, in the case of FIG. 1, the pixel reduction effect is obtained only in the XZ plane.
In the case of pixel-shifted display, the direction of pixel shift is set to one direction, and the pixel reduction direction and the pixel shift direction are matched.
[0061]
By shifting the pixel shift elements into two stages in the optical axis direction and alternately performing the optical path shift operation, it is possible to perform the pixel shift display in the two directions of XY. In this case, if the lens surface shape is as shown in FIG. 1, the pixels are not reduced in a direction in which the lens does not have a light focusing effect, and therefore, adjacent pixels in the projected image overlap.
[0062]
In the case of pixel-shifted display in the XY2 directions, the lens surfaces having the above-described shapes are configured in two stages in the optical axis direction with their optical axes coincident with each other, and the curvature directions of the lens surfaces are orthogonally arranged. And the effect of reducing the pixels in the X and Y directions can be obtained, so that the overlapping phenomenon of the adjacent pixel images can be avoided.
[0063]
In FIG. 6, the first lens surface 18A has a curvature only in the X direction, and the second lens surface 18B has a curvature only in the Y direction. FIG. 6 shows a configuration in which the lens surfaces 18A and 18B are arranged to face each other with the opening centers of the lens surfaces coincident with each other. In FIG. 6, reference numeral 21 denotes a light valve pixel.
FIG. 12 is a schematic diagram in which the lenses shown in FIG. 11 are arrayed.
[0064]
As a modification of FIG. 6, a configuration in which the lens surfaces of 18A and 18B are arranged so as to face each other is a preferable configuration because the range of incident angles of light rays on the lens surfaces is narrowed as described above.
Furthermore, if the curvature of at least one of the lens surfaces is made to be gentler at the periphery than at the lens center in addition to the orthogonal arrangement, the contrast is improved by about 10%.
[0065]
Next, a configuration in which a part of the lens surfaces 1 and 2 is integrally combined will be described. As shown in FIG. 8, the center of the opening of the lens is O, and the optical axis of the lens is the Z-axis direction. At this time, as shown in FIG. 9, the regions 22 and 23 within ± 45 degrees of the lens aperture surface are curved surfaces having a curvature in the Y direction, and the other regions 24 and 25 are curved surfaces having a curvature in the X direction. . In this way, a continuous and uninterrupted composite lens surface composed of four lens surface regions is obtained. FIG. 9 shows the surface of one microlens, and it goes without saying that the light valve element is arranged in an array as shown in FIG.
[0066]
The composite lens surface obtained as described above has an action of condensing light rays in the XY two-axis directions. In addition, the position of the surface on which light refraction in the X-axis direction occurs and the position of the surface on which light refraction in the Y-axis direction occurs do not deviate from the optical axis Z direction. Therefore, when the light-condensing positions of the light rays are considered separately in the XZ plane and the YZ plane, the respective light-condensing positions can be easily aligned, can have the same focal length, and can have the same converging angle. can do. For this reason, even when the pixel-reduced intermediate image is projected by the projection optical system, the symmetry of the obtained image performance in the X direction and the Y direction is improved.
[0067]
When the lens surface 1 and the lens surface 2 are laminated in the optical axis direction, for example, even though there is almost no depolarization when passing through the lens surface 1, the polarized light is next passed through the lens surface 2. Elimination occurs. This is because the light ray is refracted by the refraction on the lens surface 1 and the traveling direction is changed, so that the light incident angle on the lens surface 2 may have a component causing depolarization. When the lens surfaces 1 and 2 are stacked, the number of light beams that cause depolarization increases for such a reason. On the other hand, this does not occur when the lens surfaces 1 and 2 are combined.
A projection-type image display device can be configured using the above-described novel reflection-type light valve element. In such a device, pixel shift display can be performed.
[0068]
FIG. 11 is a diagram for explaining an embodiment of the projector optical system according to the present invention, and the configuration is almost the same as the configuration shown in FIG. The configuration operation of FIG. 12 is as described above. The difference between FIG. 11 and FIG. 12 lies in the pixel reduction optical system 8. As described above, in the present invention, a surface different from a conventional spherical surface is used for the surface shape of the microlens constituting the pixel reduction optical system 8 as described above.
[0069]
In the above-described pixel shift display type projector apparatus, the contrast is improved by 50% or more by changing the surface shape of the microlens of the pixel reduction element formed as a pair with the light valve to the shape described above.
[0070]
In addition to the above, a field sequential type projector engine using only one reflection type light valve element has an effect of suppressing a decrease in contrast due to depolarization. The field-sequential method has the difference that a dichroic prism or dichroic mirror is not required, the use of a time-division rotating color filter, and the timing of pixel-shifted display changes. It is not related to the decrease, and the use of the microlens does not change the depolarization.
[0071]
In addition, even when the light valve is of a transmission type, the effect of suppressing depolarization can be obtained. Also in this case, the common point is that a microlens that causes depolarization is used, so that the effect of improving contrast according to the present invention can be obtained also in a transmission type light valve.
[0072]
To perform pixel reduction with a transmission light valve, a microlens for pixel reduction is provided on the light emission side of the light valve. In this case, since light passes through the microlens only once, depolarization is less likely to occur as compared with the case of a reflective light valve. In the case of the reflection type, depolarization is further increased because the light passes through the microlens even on the return path generated on the outward path. For this reason, in the transmission type, the decrease in contrast due to depolarization is smaller. However, the polarization is depolarized when the light passes through the microlens. Therefore, the countermeasure by the light valve configuration using the above-described novel microlens is effective.
[0073]
In the case of a transmissive light valve, apart from the purpose of pixel reduction, a microlens is placed in front of the surface of the light valve closer to the illumination light source for the purpose of increasing the aperture efficiency and light use efficiency of the light valve. Often. In this case, since the light beam passes through the microlens before and after the light valve, depolarization is increased, and the effect of the present invention is more effective.
[0074]
【The invention's effect】
Since the lens surface of the microlens is characterized in that it has a curvature only in one direction of the lens surface, the depolarization effect is suppressed as compared with the conventional spherical microlens shape, and the contrast is improved.
[0075]
Since the lens surface of the microlens is characterized by having a distribution of curvature with respect to one direction of the lens surface, the light incident angle at the peripheral portion of the lens surface is reduced, so that the depolarization effect particularly at the peripheral portion of the lens is reduced. It is suppressed, thereby further improving the contrast.
[0076]
In consideration of application to a projector device, an incident light beam to a light valve is linearly polarized. In this case, by aligning or orthogonalizing the direction of the curvature surface of the microlens with the polarization direction, it is possible to reduce the depolarization generated on the microlens surface, and thereby, the contrast at the time of turning on / off the light valve. Is further improved.
[0077]
Even in the case where the pixel is shifted in two directions in the projection plane, the image quality is improved as compared with the single lens configuration, because the effect of reducing the pixel image of the light valve is obtained in the X and Y directions. In addition, the contrast is also improved because it is superior to the conventional spherical microlens lens surface in that it is less susceptible to depolarization.
[0078]
The best contrast can be achieved by using one of the two directions of curvature of the lens surfaces so as to coincide with the polarization axis of the light illuminating the reflective light valve.
[0079]
Since the directions of curvature of the lens surface 1 and the lens surface 2 are orthogonal to each other, the incident angle of light at the peripheral edge of each lens surface is reduced, and in particular, the depolarizing action of the peripheral edge of the lens is suppressed, thereby increasing the contrast. Is further improved.
[0080]
Since one of the directions having the curvature distribution of the lens surface 1 and the lens surface 2 is used in accordance with the polarization axis of the light illuminating the reflective light valve, the best contrast can be obtained. it can.
[0081]
In the lens surface of the microlens, an area within ± 45 degrees with respect to the Y axis is a lens surface having a curvature only in the Y direction at the lens center O at the peak of the curved surface. Is characterized by having a lens surface having a curvature in the X direction at the peak of the light valve, so that the position of the lens surface having the curvature does not shift in the optical axis direction, so that it becomes easy to align the position of the pixel reduced image of the light valve. In addition, depolarization hardly occurs, and the contrast of the projected display image is improved.
[0082]
Since one of the directions having the curvature of the compound lens surface is used in accordance with the polarization axis of the light illuminating the reflective light valve, the polarization direction of the incident light beam is the direction in which the curvature of the lens surface exists. , And the highest contrast can be obtained.
[0083]
Compared with a conventional pixel shift type projection optical device, an effect of suppressing depolarization is obtained, so that an image projection display device with improved light contrast characteristics can be realized.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view illustrating an embodiment of a microlens according to the present invention.
FIG. 2 is a schematic diagram showing an example of a case where the microlenses shown in FIG. 1 are arrayed.
FIG. 3 is a view for explaining another embodiment of the microlens according to the present invention.
FIG. 4 is a view for explaining another embodiment of the microlens according to the present invention.
FIG. 5 is a schematic diagram showing an example in which the microlenses shown in FIG. 4 are arrayed.
FIG. 6 is a view for explaining another embodiment of the microlens according to the present invention.
FIG. 7 is a schematic diagram showing an example in which the microlenses shown in FIG. 6 are arrayed.
FIG. 8 is a diagram illustrating a relationship between an opening center of a lens and an optical axis.
FIG. 9 is a diagram showing an example of a microlens having a compound lens surface according to the present invention.
FIG. 10 is a schematic diagram showing an example in which the microlenses shown in FIG. 9 are arrayed.
FIG. 11 is a view for explaining an example of a projection type image display device provided with a reflection type light valve element according to the present invention.
FIG. 12 is a view for explaining an example of a projection type image display device provided with a conventional reflection type light valve element.
FIG. 13 is a view showing the XZ cross-sectional configuration of a conventional pixel reduction system and a reflection type light valve.
FIG. 14 is a diagram showing a YZ sectional configuration of a conventional pixel reduction system and a reflection type light valve.
FIG. 15 is a ray diagram for explaining the operation of the microlens.
FIG. 16 is a diagram illustrating depolarization of a microlens.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Illumination light source, 2 ... Integrator optical system, 3 ... Polarization conversion element, 4 ... Polarization beam splitter (PBS), 5 ... Polarization separation surface, 6 ... Retarder, 7 ... Color separation / synthesis element, 8 (8R, 8G, 8B) Pixel reduction optical system, 9 (9R, 9G, 9B) reflection light valve, 10 polarization conversion element, 11 pixel shift element, 12 projection optical system, 13 microlens substrate, 14 microlens Array, 15: adhesive layer, 16: liquid crystal layer, 17: light valve substrate, 18 (18A, 18B): lens surface, 19: ridge line.

Claims (12)

In a reflective light valve element, and a reflective light valve element having an array of microlenses opposed to each of a plurality of pixels of the reflective light valve body, the lens surface of the microlens is a lens surface of the lens surface. A reflective light valve element having a curvature in only one direction. In a reflective light valve element, and a reflective light valve element having an array of microlenses opposed to each of a plurality of pixels of the reflective light valve body, the lens surface of the microlens is a lens surface of the lens surface. A reflective light valve element having a distribution of curvature in one direction. 3. The reflective light valve element according to claim 2, wherein the curvature of the lens surface has a distribution that is gentler at the periphery than at the center of the lens. 4. The reflection type light valve element according to claim 1, wherein a curvature direction of the lens surface is used in accordance with a vibration direction (polarization axis) of light illuminating the reflection type light valve. A reflection type light valve element characterized by the above-mentioned. 4. The reflective light valve element according to claim 1, wherein a curvature direction of the lens surface is arranged to be 90 degrees with respect to a vibration direction of light illuminating the reflective light valve. A reflective light valve element, which is used. In a reflective light valve element having a reflective light valve body and an array of microlenses opposed to each of a plurality of pixels of the reflective light valve body, the microlens has a structure in which two lens surfaces are laminated. And one of the two lens surfaces is a lens surface 1 having a curvature in one direction of the lens surface, and the other lens surface has a curvature direction of the lens surface 1. A reflection-type light valve element having a lens surface 2 having a curvature in a direction perpendicular to the direction of the reflection. 7. The reflective light valve element according to claim 6, wherein one of the two lens surfaces having a direction of curvature is used in accordance with the polarization axis of light illuminating the reflective light valve. A reflection type light valve element characterized by the above-mentioned. In a reflective light valve body, and a reflective light valve element having an array of microlenses opposed to each of a plurality of pixels of the reflective light valve body, the microlenses are arranged in one direction of the lens surface. It has a lens surface 1 having a curvature distribution and a lens surface 2 having a curvature distribution with respect to the other direction of the lens surface, and the directions of curvature of the lens surface 1 and the lens surface 2 are orthogonal. 1. A reflection type light valve element comprising: 9. The reflective light valve element according to claim 8, wherein one of the directions having the curvature distribution of the lens surface 1 and the lens surface 2 coincides with the polarization axis of the light illuminating the reflective light valve. A reflective light valve element, which is used. In a reflective light valve element having a reflective light valve body, and an array of microlenses opposed to each of a plurality of pixels of the reflective light valve body, the center of the lens opening of the microlens is O, the lens is When the optical axis of the micro-lens is the Z axis and the oscillation direction of the P-polarized light or the S-polarized light is the Y axis, the center O of the lens surface of the microlens is a curved surface within ± 45 degrees from the Y axis. A reflective surface having a lens surface having a curvature only in the Y direction at its peak, and the other region being a lens surface having a curvature at the center O at the peak of the curved surface in the X direction. 11. The reflective light valve element according to claim 10, wherein one of the directions having a curvature of the compound lens surface is used in accordance with the polarization axis of light illuminating the reflective light valve. Characteristic reflective light valve element. An illumination light source, an integrator optical system, a linear polarizer 1, and a polarization beam splitter (PBS) having a polarization splitting surface that reflects illumination light that has been linearly polarized by the linear polarizer 1 are sequentially arranged. Optical system 1
A phase compensator provided on the reflection optical path of the polarization separation surface, a color separation prism for separating RGB, and reflection light valves for R, G, and B disposed on an emission surface of the color separation prism are sequentially arranged. Optical system 2
A linear polarizer 2 arranged in a cross nicol fashion with the linear polarizer 1 to transmit / block the reflected light of the reflective light valve transmitted through the PBS; a pixel shifting element; and a projection optical system for projecting an image of the light valve. And an optical system 3 in which
In the projection type image display device comprising:
A projection-type image display device, wherein the reflection-type light valve is the reflection-type light valve element according to claim 1.

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