JP3669051B2 - Projection display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection display device that projects and displays a display image formed by modulation means such as a liquid crystal panel on a screen.
[0002]
[Prior art]
FIG. 11 shows a typical configuration example of a projection display device (three-plate projection display device) using three liquid crystal panels as modulation means. In the three-plate projection display device 900, light from the light source unit 100 is converted into light beams of three primary colors of red light, green light, and blue light by two dichroic mirrors 401 and 402 (color light separation means) having wavelength selectivity. After separation, the liquid crystal panels 411, 412, and 413 (modulation means) corresponding to the respective color lights are irradiated, and the light transmitted through the respective liquid crystal panels is synthesized by the cross dichroic prism 450 (color light synthesis means) and projected. The lens 460 (projection optical system) is configured to project and display on the screen 470.
[0003]
Here, the cross dichroic prism 450 used as the color light synthesizing means is configured by arranging prisms on which a dichroic film is formed in an X shape. The color light combining means of the three-plate projection display device can be realized by a configuration using two dichroic mirrors in a parallel arrangement instead of the cross dichroic prism, but in the configuration using the cross dichroic prism, Compared to a configuration using two dichroic mirrors, the distance between the liquid crystal panel and the projection lens can be shortened, so a projection display device that can obtain a bright projection image without using a large-diameter projection lens is provided. It is easy to realize. Therefore, a cross dichroic prism is often used as the color light combining means in the projection display device.
[0004]
By the way, in a projection display device using a small liquid crystal panel, in order to obtain a brighter projected image, it is important to efficiently illuminate the small liquid crystal panel using a lamp having a short arc length as a light source. . This is because the light condensing performance can be improved as the arc length of the lamp becomes shorter. Therefore, in recent years, a projection display device equipped with a lamp having an extremely short arc length is being developed.
[0005]
[Problems to be solved by the invention]
As described above, the projection display device using the cross dichroic prism as the color light combining means has an excellent feature that it is easy to obtain a bright projected image, but has a problem caused by the cross dichroic prism.
[0006]
FIG. 10 schematically shows a general planar structure of the cross dichroic prism. As shown in FIG. 10, in the cross dichroic prism 450, the prisms 451 on which the wavelength-selective dichroic film 452 is formed are arranged in an X shape, and these four prisms 451 are optically bonded with the same refractive index as the prism. It is formed by integrating with the agent 453. At this time, since the thickness of the optical adhesive is about several tens of μm, the central portion of the cross dichroic prism, that is, the portion 454 where the dichroic film intersects in an X shape is in a discontinuous state where the dichroic film is not connected. As a result, when light that is reflected by the dichroic film and is supposed to go to the projection lens is incident on this portion (portion 454 where the dichroic film intersects in an X-shape), the dichroic film does not exist, so Is not reflected (however, green light is not reflected by the dichroic film and is incident on the projection lens). In addition, the ridgeline part of each prism where the four prisms closely adhere to each other in an X shape is not a perfect right-angled shape due to the limit of the mechanical processing accuracy of the prism, and the surface state has poor smoothness. The corner surface 455 has a very narrow width and has this portion (in FIG. 10, this portion is exaggerated). As a result, the light incident on this portion (angular surface 455 having a narrow pole width) is scattered by the portion of the angular surface 455 and is not directed toward the projection lens. That is, there is one direction at the center of the cross dichroic prism (this one direction corresponds to a vertical direction perpendicular to the horizontal direction when the longitudinal direction of the projection screen is the horizontal direction. The optically inhomogeneous region 456 (existing in the direction perpendicular to the paper surface in FIG. 10) is present, and this region is a region through which light does not easily pass. Therefore, the amount of light passing through a region 456 that is not uniform is reduced compared to light passing through other regions.
[0007]
Therefore, in a projection display device using a cross dichroic prism as color light combining means, dark shadows (regions where brightness has been locally reduced) due to structural problems of the cross dichroic prism are vertically applied to the center of the projection screen. This is one of the major factors that cause the display quality of projected images to deteriorate. The degree of this dark shadow (the degree to which the brightness of the dark shadow part is reduced from the brightness of the surrounding area) has a strong correlation with the arc length of the lamp used for the light source. The reason is that the shorter the arc length, the more parallel and condensing the light emitted from the light source, and as a result, the light beam that passes through the optically inhomogeneous region in the center of the cross dichroic prism. This is because the ratio of increases. Therefore, when a lamp with a long arc length is used as the light source, dark shadows are not so noticeable and are not a big problem, but in recent years, a lamp with a very short arc length is used as the light source to obtain a brighter projected image. In the case of use in this case, the presence of this dark shadow is very conspicuous, causing a serious problem of reducing the display quality of the projected image.
[0008]
In view of the above points, an object of the present invention is to use a color light combining unit configured by crossing multilayer films in an X shape to combine a plurality of light beams modulated by the modulation unit into one. An object of the present invention is to realize a projection display apparatus that can project and display a high-quality image free from visual obstacles by making dark shadows inconspicuous due to structural problems of the cross dichroic prism.
[0009]
[Means for Solving the Problems]
To solve the above problem,
1) The first projection display device of the present invention is
A light source;
Color light separating means for separating a light beam from the light source into three color light beams;
Three modulation means for modulating each of the light beams separated by the color light separation means;
A diffraction grating disposed on an optical path between the light source and the modulation means;
Color light synthesizing means in which a multilayer film for synthesizing a plurality of light beams modulated by the respective modulation means into one is crossed in an X shape;
A projection optical system for projecting a light beam synthesized by the color light synthesis means;
It is characterized by having.
[0010]
By adopting the above configuration, the above-described problems can be solved. That is, in a projection display device using a cross dichroic prism as color light combining means, or even when a lamp having a very short arc length is used as a light source, the diffraction grating is disposed on the optical path between the light source and the modulation means. This prevents the occurrence of dark shadows due to the structural problem of the cross dichroic prism, and has an effect of projecting and displaying a high-quality image without visual disturbance.
[0011]
The light beam incident on the cross dichroic prism is emitted from the cross dichroic prism while projecting the light beam while avoiding an optically inhomogeneous region (light is difficult to pass locally) in the center of the cross dichroic prism. If it can be guided into the entrance pupil of the lens, it is possible to prevent the occurrence of dark shadows due to structural problems of the cross dichroic prism. For this purpose, a light beam incident on the cross dichroic prism is divided into a plurality of light beams having a specific angle component (that is, several light beams with a specific diffraction angle in a certain spread angle T as a whole light beam. In a dispersed state), and such conversion of the light beam can be realized by using a diffraction grating.
[0012]
Here, the diffraction grating used in the above configuration will be described. The diffraction grating has an action (diffraction effect) of causing an interference phenomenon to light passing through the diffraction grating and emitting the light in a specific direction by a regular structure formed on the surface or inside thereof. FIG. 7 shows a general diffraction grating10Schematically shows the diffraction state of the light passing through10The light 20 incident on the diffraction grating as it is along the incident direction10The first-order light 21 and the first-order light 23 are divided into the zero-order light 21 emitted from the light source and the higher-order light emitted with a certain emission angle θ with respect to the incident direction. , + Secondary light 24, -secondary light 25,... (In FIG. 7, description of higher-order light of ± 3rd order or higher is omitted). At this time, the direction in which the light is emitted and the intensity of the light are determined by the wavelength of the light incident on the diffraction grating, the surface of the diffraction grating, or the size and shape of the periodic structure formed inside. For example, a diffraction grating that can generate only high-order light without generating zero-order light can be used.
[0013]
Therefore, according to the above configuration, the light beam incident on the cross dichroic prism is converted into a plurality of light beams having a specific angle component by using the diffraction effect of the diffraction grating, and is present at the center of the cross dichroic prism. Since the light beams are guided into the entrance pupil of the projection lens while avoiding the light beams from concentrating on the optically inhomogeneous region 456, dark shadows hardly occur at the center of the projection screen, and High quality images can be projected and displayed. At this time, by appropriately setting the emission angle of the light beam emitted from the diffraction grating, all the light beams emitted from the diffraction grating can be guided into the entrance pupil of the projection lens. As a result, it is possible to effectively prevent only the occurrence of dark shadows with almost no optical loss due to the use of the diffraction grating. In particular, when a lamp with a very short arc length that emits a highly collimated light beam is used as the light source, the light collecting property is high, and therefore, in an optically inhomogeneous region present at the center of the cross dichroic prism. Even in such a case, the light beam incident on the cross dichroic prism is dispersed by adopting the above configuration in which the diffraction grating is disposed on the optical path between the light source and the modulation means. Therefore, it is possible to effectively prevent dark shadows and project and display high-quality images.
[0014]
Note that the diffraction grating may be disposed at any position on the optical path between the light source and the modulation means, but depending on the distance between the diffraction grating and the projection lens, the spread angle of the light beam by the diffraction grating. It is necessary to adjust the T and set the diffraction grating so that all the light beams that have passed through the modulation means are incident on the entrance pupil of the projection lens.
[0015]
2) In the first projection display device,
For each of the three modulation means, a diffraction grating is disposed at a position on the light incident side of the modulation means.
[0016]
As described in the preceding section 1), the diffraction grating may be arranged at any position on the optical path between the light source and the modulation means. In particular, as in the above-described configuration, the three diffraction gratings are respectively arranged. When the modulation unit is arranged at a position on the side where the light beam of the modulation unit is incident, the distance between the diffraction grating and the projection lens is shortened, so that the spread angle T of the light beam by the diffraction grating can be set large. It is possible to more effectively avoid a state in which the light beam concentrates on an optically inhomogeneous region present in the center portion of the cross dichroic prism. Therefore, it is possible to more effectively prevent the occurrence of dark shadows that occur at the center of the projection screen.
[0017]
Further, the spread angle T of the light beam by the diffraction grating varies depending on the wavelength of the light beam incident on the diffraction grating. Therefore, by adopting the above configuration, each diffraction grating can be optimized in accordance with the wavelength of the light beam incident on each modulation means, so that the generation of dark shadows can be prevented more effectively. Can do.
[0018]
3) In the first projection display device,
The diffraction grating is a one-dimensional type diffraction grating.
[0019]
An optically inhomogeneous area that causes dark shadows is present as an elongated area in one direction (generally the vertical direction) at the center of the cross dichroic prism. The direction to spread and disperse is one direction that intersects perpendicularly to the direction in which the optically inhomogeneous region exists (if the direction in which the optically inhomogeneous region exists in the cross dichroic prism exists is the vertical direction) The direction in which the light beam is expanded by the diffraction grating is the lateral direction). Therefore, the one-dimensional type in which the light diffraction direction is the one-dimensional direction is optimal as the diffraction grating to be used.
[0020]
4) In the first projection display device,
The diffraction grating is a surface relief type diffraction grating.
[0021]
An example of the cross-sectional shape of the diffraction grating is shown in FIG. As can be seen from FIG. 8, this type of diffraction grating produces a diffraction effect by the regular uneven shape 12 formed on the surface of the diffraction grating 11. This type of diffraction grating has the disadvantage that it is very easy to make replicas (replicas), although it has the disadvantage that some light loss tends to occur on the surface of the diffraction grating due to the uneven shape present on the surface. Has characteristics. Therefore, when this type of diffraction grating is used, the diffraction grating can be manufactured at a low cost, and therefore, the cost of the optical system can be reduced.
[0022]
5) In the first projection display device,
The diffraction grating is a distributed refractive index type diffraction grating.
[0023]
An example of the cross-sectional shape of the diffraction grating is shown in FIG. As can be seen from FIG. 9, this type of diffraction grating produces a diffraction effect by a regular refractive index distribution 14 formed inside the diffraction grating 13. This type of diffraction grating is characterized in that since the surface of the diffraction grating has a planar shape, light loss on the surface of the diffraction grating is extremely small, and high diffraction efficiency can be obtained. Therefore, when this type of diffraction grating is used, it is possible to effectively prevent the occurrence of a dark shadow at the center of the projection screen and to extremely reduce the light loss in that case.
[0024]
6) The second projection display device of the present invention
A light source;
A first optical element that condenses the luminous flux emitted from the light source and converts it into a plurality of intermediate luminous fluxes spatially separated from each other;
A second optical element disposed near a position where the intermediate light beam converges;
Color light separating means for separating a light beam emitted from the second optical element into three color light beams;
Three modulation means for modulating each of the light beams separated by the color light separation means;
Color light combining means for combining a plurality of light beams modulated by the respective modulation means;
Projection means for projecting the light beam synthesized by the color light synthesis means,
The second optical element comprises:
Polarized light beam separating means for spatially separating each of the intermediate light beams into a P-polarized light beam and an S-polarized light beam, and the polarization direction of one of the P-polarized light beam and the S-polarized light beam is the polarization direction of the other polarized light beam. A polarization generating device having a polarization direction converting means aligned with
A superimposing coupling unit that is arranged on the exit surface side of the polarization generator and superimposes and couples the respective intermediate light beams;
A diffraction grating is arranged on an optical path between the light source and the modulation means.
[0025]
When the diffraction grating is not arranged in the above configuration, a dark shadow due to the structural problem of the cross dichroic prism is generated in the vertical direction at the center of the projection screen. In particular, in the above configuration, since the first optical element in which the light beam splitting lenses are arranged in a matrix is adopted, dark shadows are also generated at a plurality of locations according to the number of the light beam splitting lenses arranged in the horizontal direction. . As a result, the presence of this dark shadow becomes very conspicuous, and the quality of the projected image is greatly reduced.
[0026]
Therefore, by adopting the above configuration, the problem described above can be solved as described in the above item 1). That is, in a projection display device using a cross dichroic prism as color light combining means, or even when a lamp having a very short arc length is used as a light source, the diffraction grating is disposed on the optical path between the light source and the modulation means. As a result, it is possible to prevent the occurrence of dark shadows caused by the structural problem of the cross dichroic prism, and to project and display a high-quality image without visual disturbance.
[0027]
In particular, in the case of the above-described configuration, it is possible to almost completely prevent the occurrence of dark shadows occurring at a plurality of locations when the diffraction grating is not disposed, so that it is possible to project and display a high-quality image without visual obstacles. .
[0028]
7) In the second projection display device,
For each of the three modulation means, a diffraction grating is disposed at a position on the light incident side of the modulation means.
[0029]
By adopting the above configuration, as described in the above item 2), the three diffraction gratings are arranged at positions where the light beams of the modulation means are incident for each of the modulation means. Since the distance between the projection lens and the projection lens is shortened, the spread angle T of the light beam by the diffraction grating can be set large, and the state where the light beam is concentrated in the optically inhomogeneous region present in the central portion of the cross dichroic prism can be further improved. Can be effectively avoided. Therefore, it is possible to more effectively prevent the occurrence of dark shadows that occur at the center of the projection screen.
[0030]
Further, since each diffraction grating can be optimized in accordance with the wavelength of the light beam incident on each modulation means, it is possible to more effectively prevent the occurrence of dark shadows.
[0031]
8) In the second projection display device,
The diffraction grating is a one-dimensional type diffraction grating.
[0032]
Also in this case, as in the above item 3), the optically inhomogeneous region present at the center of the cross dichroic prism exists as an elongated region in one direction. A one-dimensional type whose diffraction direction is a one-dimensional direction is optimal.
[0033]
9) In the second projection display device,
The diffraction grating is a surface relief type diffraction grating.
[0034]
Similarly to the above item 4), when this type of diffraction grating is used, the diffraction grating can be manufactured at low cost, so that the cost of the optical system can be reduced.
[0035]
10) In the second projection display device,
The diffraction grating is a distributed refractive index type diffraction grating.
[0036]
As in the above item 5), when this type of diffraction grating is used, it is possible to effectively prevent the occurrence of dark shadows occurring at the center of the projection screen, and extremely reduce light loss in that case. it can.
[0037]
11)Of the present inventionThe third projection display device
A light source;
Color light separating means for separating a light beam emitted from the light source into three color light beams;
Three modulation means for modulating each of the light beams separated by the color light separation means;
Color light combining means for combining a plurality of light beams modulated by the respective modulation means;
Projection means for projecting the light beam synthesized by the color light synthesis means,
The color light separating means and the color light synthesizing means are composed of a dichroic prism in which a multilayer film is crossed in an X shape,
The modulation means comprises a reflective liquid crystal device,
A diffraction grating is arranged on an optical path between the light source and the modulation means.
[0038]
When the diffraction grating is not arranged in the above configuration, a dark shadow due to the structural problem of the cross dichroic prism is generated in the vertical direction at the center of the projection screen. In particular, in the above configuration, since the first optical element in which the light beam splitting lenses are arranged in a matrix is adopted, dark shadows are also generated at a plurality of locations according to the number of the light beam splitting lenses arranged in the horizontal direction. . As a result, the presence of this dark shadow becomes very conspicuous, and the quality of the projected image is greatly reduced.
[0039]
Therefore, by adopting the above configuration, the problem described above can be solved as described in the above item 1). That is, even in a projection display device using a cross dichroic prism as color light combining means, or at the same time when a lamp having a very short arc length is used as the light source, the diffraction grating is disposed on the optical path between the light source and the modulating means. As a result, it is possible to prevent the occurrence of dark shadows caused by the structural problem of the cross dichroic prism, and to project and display a high-quality image without visual disturbance.
[0040]
In particular, in the case of the above-described configuration, it is possible to almost completely prevent the occurrence of dark shadows occurring at a plurality of locations when the diffraction grating is not disposed, so that it is possible to project and display a high-quality image free from visual obstacles. .
[0041]
Note that in a reflective liquid crystal device, a switching element can be disposed under a pixel electrode, so that the pixel pitch can be reduced without reducing the element. Therefore, it is possible to easily increase the pixel density and obtain a projection image with high resolution.
[0042]
Furthermore, since color light separation and color light synthesis can be configured by the same dichroic prism, the projection display device can be miniaturized, and light loss can be prevented by shortening the optical path length, resulting in a bright projected image. Can be obtained.
[0043]
12) SaidThirdIn a projection display device,
The diffraction grating is a one-dimensional type diffraction grating.
[0044]
Also in this case, as in the above item 3), the optically inhomogeneous region present at the center of the cross dichroic prism exists as an elongated region in one direction. A one-dimensional type whose diffraction direction is a one-dimensional direction is optimal.
[0045]
13) saidThirdIn a projection display device,
The diffraction grating is a surface relief type diffraction grating.
[0046]
Similarly to the above item 4), when this type of diffraction grating is used, the diffraction grating can be manufactured at low cost, so that the cost of the optical system can be reduced.
[0047]
14) saidThirdIn a projection display device,
The diffraction grating is a distributed refractive index type diffraction grating.
[0048]
As in the above item 5), when this type of diffraction grating is used, it is possible to effectively prevent the occurrence of dark shadows occurring at the center of the projection screen, and extremely reduce light loss in that case. it can.
[0049]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, unless otherwise specified, three directions orthogonal to each other are defined as an X direction, a Y direction, and a Z direction.
[0050]
Example 1
FIG. 1 is a schematic configuration diagram in plan view of an optical system portion of the projection display apparatus according to the first embodiment. The projection display device 600 of this example uses a transmissive liquid crystal panel as a modulation means, and includes a light source unit 100, one diffraction grating 480, and two dichroic mirrors 401, 402, 3 as color light separation means. Three liquid crystal panels 411, 412, 413 arranged corresponding to each of the primary color light beams, a cross dichroic prism 450 which is a color light combining means configured by crossing wavelength-selective multilayer films in an X-shape, and A projection lens 460, which is a projection optical system for enlarging and projecting the combined luminous flux on the screen 470, is roughly configured.
[0051]
The light source unit 100 is generally composed of a light source lamp 110 and a parabolic reflector 120, and a light beam emitted from the light source lamp 110 is reflected in one direction by the parabolic reflector 120 to become a substantially parallel light beam. Are emitted. Here, instead of the parabolic reflector, an elliptical reflector, a spherical reflector, or the like can be used.
[0052]
On the emission side of the light source unit 100, a surface relief type diffraction grating 480 whose sectional shape is shown in FIG. A regular structure having a substantially sinusoidal cross section is formed on the surface of the diffraction grating. As a result, most of the light incident on the diffraction grating is ± first order light and ± second order light. Is emitted. Accordingly, when the light beam emitted from the light source unit 100 passes through the diffraction grating 480, it is converted into a light beam having almost four specific angle components due to the diffraction effect of light and slightly spreading as a whole. Is done.
[0053]
The light beams emitted from the diffraction grating 480 are separated into three light beams according to the wavelength by the color light separating means, reach the corresponding liquid crystal panels, and illuminate the respective liquid crystal panels. That is, first, the blue light and green light reflecting dichroic mirror 401 transmits red light and reflects blue light and green light. The red light is reflected by the reflection mirror 403 and reaches the red light liquid crystal panel 411. On the other hand, of the blue light and the green light, the green light is reflected by the green light reflecting dichroic mirror 402 and reaches the liquid crystal panel 412 for green light. Further, the blue light transmitted through the green light reflecting dichroic mirror 402 reaches the blue light liquid crystal panel 413 through two reflecting mirrors 435 and 436.
[0054]
Here, the liquid crystal panel for red light 411, the liquid crystal panel for green light 412 and the liquid crystal panel for blue light 413 modulate each color light and include display information corresponding to each color light, and then cross the modulated color light. The light enters the dichroic prism 450, and each modulated light beam is combined into one light beam in the cross dichroic prism 450. As shown in FIG. 10, the cross dichroic prism 450 used here has a red light reflecting dielectric multilayer film and a blue light reflecting dielectric multilayer film arranged in an X shape inside. In addition, due to the structural problem of the cross dichroic prism, it has an optically inhomogeneous region inside.
[0055]
The light beam synthesized by the cross dichroic prism 450 forms an image on the screen 470 through the projection lens 460.
[0056]
In the projection display device 600 configured as described above, each of the liquid crystal panels 411, The light that illuminates 412 and 413 has almost four specific angle components, and as a whole, the light beam is slightly spread. The optical images formed on the respective liquid crystal panels are combined in the cross dichroic prism 450 to form a color optical image (video) on the screen 470. At this time, the light beam passing through the cross dichroic prism 450 is also transmitted. After all, the light beam has almost four specific angle components and has a slightly broader overall. Accordingly, the light flux does not concentrate in the optically inhomogeneous region present in the central portion of the cross dichroic prism 450, so that it passes through the cross dichroic prism and generates an optical image on the screen with little local light loss. Can be formed, and dark shadows (regions with locally reduced brightness) that are visually obtrusive are not generated in the center of the projection screen.
[0057]
In designing the diffraction grating, the output angle of the light beam emitted from the diffraction grating is set appropriately, and all the light beams emitted from the diffraction grating are guided into the entrance pupil of the projection lens. There is almost no decrease in brightness due to the installation of the grid.
[0058]
In this example, since the light incident on the diffraction grating is broadband visible light including the three primary colors, the design wavelength used for manufacturing the diffraction grating is the wavelength of green light. However, the appearance of dark shadows generated on the projection screen due to the structural problem of the cross dichroic prism depends on the wavelength of light passing through the cross dichroic prism. Therefore, the design wavelength used when manufacturing the diffraction grating is not limited to green light, and it is desirable to set the design wavelength to a wavelength of light that makes dark shadows most inconspicuous. Further, the light distribution pattern of the diffracted light generated by the diffraction grating (in this example, ± 1st order light and ± 2nd order light) is not limited to this example, and the above dark shadow is the least noticeable. It is desirable to set so that
[0059]
Therefore, in the projection display device of this example, the effective use of the diffraction grating hardly reduces the brightness of the projected image, and dark shadows generated on the projection screen due to the structural problem of the cross dichroic prism. Occurrence can be effectively prevented, and a high-quality projected image can be realized.
[0060]
(Example 2)
In the first embodiment described above, one diffraction grating is arranged between the light source unit and the color light separation means. Instead, three diffraction gratings are provided for each modulation means. It is good also as a structure arrange | positioned in the position of the side into which the light beam enters.
[0061]
A configuration of a projection display device 700 including three diffraction gratings will be described as a second embodiment. FIG. 2 is a schematic configuration diagram in plan view of an optical system portion of the projection display apparatus 700 according to the second embodiment. In the projection display device 700 and each embodiment described below, the basic configuration is the same as that of the projection display device 600 according to the first embodiment. A description thereof will be omitted.
[0062]
As can be seen from FIG. 2, in the projection display apparatus 700 of this example, each liquid crystal panel 411, 412, and 413 is positioned at a position on the side where the illumination light from the light source unit 100 is incident. Diffraction gratings 491, 492, and 493 are installed, respectively. The diffraction grating used in this example is the same surface relief type diffraction grating as in the first embodiment. Furthermore, each diffraction grating is optimized according to the wavelength of light incident on each diffraction grating. That is, the red light diffraction grating 491 optimized for red light is provided on the light source side of the red light liquid crystal panel 411, and the green light is optimized on the light source part side of the green light liquid crystal panel 412. A green light diffraction grating 492 is disposed on the light source side of the blue light liquid crystal panel 413, and a blue light diffraction grating 493 optimized for blue light is disposed.
[0063]
In the projection display device 700 configured as described above, the illumination light from the light source unit 100 has almost four specific angle components due to the diffraction action of the light by the diffraction grating, and as a whole has a slight spread. It is converted into a luminous flux. Since each of the liquid crystal panels 411, 412, and 413 is illuminated with these lights, the light flux is not concentrated in the optically inhomogeneous region present in the central portion of the cross dichroic prism 450, and local light loss is hardly caused. It can pass through the cross dichroic prism without being generated, and an optical image can be formed on the screen, resulting in a visually obtrusive dark shadow (region where brightness is locally reduced) in the center of the projection screen. There is no.
[0064]
Further, in the projection display apparatus 700 of this example, diffraction gratings having different characteristics are arranged for each liquid crystal panel. Therefore, the distance between the diffraction grating and the projection lens is shortened, the spread angle T of the light beam by the diffraction grating can be set large, and the diffraction grating can be optimized according to the wavelength of the light beam incident on the diffraction grating. Thus, it is possible to effectively prevent dark shadows from occurring in the center of the projection screen.
[0065]
Therefore, in this example as well, the effective use of the diffraction grating effectively reduces the occurrence of dark shadows on the projection screen due to the structural problem of the cross dichroic prism without substantially reducing the brightness of the projected image. And high-quality projected images can be realized.
[0066]
(Example 3)
Next, an embodiment in which a diffraction grating is introduced into a projection display device provided with a polarization illumination system will be described.
[0067]
FIG. 3 is a schematic configuration diagram in plan view of the optical system portion of the projection display apparatus 800 according to the third embodiment. The basic configuration of the projection display device 800 of this example is the same as that of the projection display device 700 of the second embodiment, but the brightness unevenness is small and illumination light having almost one kind of polarization state is efficiently used. A feature of the present invention is that the uniform polarization illumination optical device 200 that is generated automatically and the relay optical device 430 that efficiently transmits the illumination light are mounted.
[0068]
First, the uniform polarization illumination optical device 200 will be described.
[0069]
As shown in FIG. 4, the optical configuration of the uniformly polarized illumination optical device 200 mainly includes a light source unit 100, a first optical element 210, and a second optical element 220.
[0070]
The light source unit 100 is the same as the light source unit of the first embodiment, and emits a polarized light beam having a random polarization direction (hereinafter, abbreviated as a random polarized light beam) in a state substantially parallel to one direction. Here, the light source unit 100 is arranged so that the light source optical axis R of the light source unit 100 is shifted in parallel to the X direction by a certain distance D with respect to the system optical axis L.
[0071]
As shown in FIG. 5, the first optical element 210 is configured by arranging a plurality of light beam splitting lenses 211 having a rectangular outer shape in an XY plane in a matrix. The light incident on the first optical element 210 is divided into a plurality of intermediate light beams 212 by the light beam splitting lens 211, and at the same time in a plane perpendicular to the system optical axis L (XY in FIG. The same number of condensing images 213 as the number of light beam splitting lenses are formed at positions where the intermediate light beam on the plane) converges. The outer shape of the light beam splitting lens on the XY plane is set to be similar to the shape of the illumination area 290 (in this example, the liquid crystal panels 411, 412, 413). In this example, since a horizontally long liquid crystal panel that is long in the X direction on the XY plane is assumed, the outer shape of the light beam splitting lens 211 on the XY plane is also horizontally long. Further, the arrangement of the light beam splitting lenses 211 constituting the first optical element 210 is not limited to the orthogonal matrix as shown in FIG. 5, but is arranged in the X direction as in, for example, a delta arrangement. The arrangement may be such that the lens columns of the beam splitting lens are in a state of being shifted between the rows in the Y direction. However, in this case, it is necessary to appropriately change the arrangement of the condenser lens 241 and the polarization separation unit 231 described later so that the intermediate light beam from the light beam splitting lens can be received effectively.
[0072]
The second optical element 220 is a complex mainly composed of a condensing lens array 240, a polarization separation unit array 230, a selective phase difference plate 250, and an exit side lens 260, and is collected by the first optical element 210. The optical image 213 is arranged in a plane perpendicular to the system optical axis L (XY plane in FIG. 4) near the position where the optical image 213 is formed. If the parallelism of the light beams incident on the first optical element 210 is extremely good, the condensing lens array 240 may be omitted from the second optical element. The second optical element 220 spatially separates each of the intermediate light beams 212 into a P-polarized light beam and an S-polarized light beam, and then aligns the polarization direction of one polarized light beam with the polarization direction of the other polarized light beam, It has a function of guiding each light flux having substantially the same polarization direction to one illumination area 290.
[0073]
The condensing lens array 240 has substantially the same configuration as that of the first optical element 210, that is, a plurality of condensing lenses 241 as many as the light beam splitting lenses 211 constituting the first optical element 210 are arranged in a matrix. They are arranged, and have the function of guiding each intermediate light beam while condensing it at a specific location of the polarization separation unit array 230. Therefore, it is ideal that the light incident on the polarization separation unit array 230 has the principal ray tilt parallel to the system optical axis L in accordance with the characteristics of the intermediate light beam 212 formed by the first optical element 210. It is desirable that the lens characteristics of each condensing lens be optimized in consideration of the point that is appropriate. However, in general, in consideration of cost reduction of the optical system and ease of design, the same optical element 210 as the first optical element 210 is used as the condenser lens array 230, or the light beam splitting lens 211 and Since a condensing lens array configured using condensing lenses having a similar shape on the XY plane may be used, in this example, the first optical element 210 is used as the condensing lens array 240. Used.
[0074]
Next, the polarization separation unit array 230 has a configuration in which a plurality of polarization separation units 231 are arranged in a plane perpendicular to the system optical axis L (XY plane in FIG. 4).
[0075]
The polarization separation unit 231 is a quadrangular prism-like structure having a polarization separation surface 232 and a reflection surface 233 inside, and spatially converts each of the intermediate light beams 212 incident on the polarization separation unit into a P-polarized light beam and an S-polarized light beam. It has the effect | action which isolate | separates into. The outer shape of the polarization separation unit 231 on the XY plane is similar to the outer shape of the light beam splitting lens 211 on the XY plane, that is, a horizontally long rectangular shape. Accordingly, the polarization separation surface 232 and the reflection surface 233 are arranged so as to be aligned in the horizontal direction (X direction). Here, the polarization separation surface 232 is inclined at about 45 degrees with respect to the system optical axis L, the reflection surface 233 is parallel to the polarization separation surface, and the polarization separation surface 232 is on the XY plane. The polarization separation surface 232 and the reflection surface 233 are set so that the cross-sectional area to be projected and the cross-sectional area projected by the reflection surface 233 on the XY plane are equal. Therefore, in this example, the lateral width on the XY plane of the region where the polarization separation surface 232 exists is equal to the lateral width on the XY plane of the region where the reflection surface 233 exists, and each of them is of the polarization separation unit 231. The width is set to be half of the horizontal width on the XY plane. In general, the polarization separation surface 232 can be formed of a dielectric multilayer film, and the reflection surface 233 can be formed of an aluminum film.
[0076]
The light incident on the polarization separation unit 231 travels in the direction of the P-polarized light beam that passes through the polarization separation surface 232 without changing the traveling direction on the polarization separation surface 232 and the direction of the adjacent reflection surface 233 that is reflected by the polarization separation surface 232. It is separated into S-polarized light fluxes that change direction. The P-polarized light beam is emitted as it is from the polarization separation unit, and the S-polarized light beam changes its traveling direction again at the reflecting surface 233, becomes substantially parallel to the P-polarized light beam, and is emitted from the polarization separation unit. Therefore, the random polarized light beam incident on the polarization separation unit 231 is separated into two types of polarized light beams of P-polarized light beam and S-polarized light beam having different polarization directions by the polarization separation unit, and in almost the same direction from different places of the polarization separation unit. It is emitted toward. Since the polarization separation unit has the above-described operation, it is necessary to guide each intermediate light beam 212 to a region where the polarization separation surface 232 of each polarization separation unit 231 exists. Therefore, the polarization separation unit in the polarization separation unit It is necessary to adjust the positional relationship between the respective polarization separation units 231 and the respective condensing lenses 241 and the lens characteristics of the respective condensing lenses 241 so that the intermediate light beam enters the central portion of the surface. In the case of this example, since the central axis of each condenser lens is arranged at the center of the polarization separation surface 232 in each polarization separation unit 231, the condenser lens array 240 includes the polarization separation unit. The polarization separation unit array 230 is displaced in the X direction by a distance corresponding to ¼ of the lateral width (that is, equal to the distance D).
[0077]
A selective phase difference plate 250 in which λ / 2 phase difference plates 251 are regularly arranged is installed on the exit surface side of the polarization separation unit array 230. That is, in the polarization separation unit 231 constituting the polarization separation unit array 230, the λ / 2 phase difference plate 251 is disposed only in the portion where the P-polarized light beam is emitted, and λ / 2 is disposed in the portion where the S-polarized light beam is emitted. The phase difference plate 251 is not installed. By such a position-selective arrangement of the λ / 2 phase difference plate 251, the P-polarized light beam emitted from the polarization separation unit 231 is subjected to a rotation action in the polarization direction when passing through the λ / 2 phase difference plate 251. It is converted into an S-polarized light beam. On the other hand, since the S-polarized light beam emitted from the polarization separation unit 231 does not pass through the λ / 2 phase difference plate 251, the polarization direction does not change and passes through the selective phase difference plate 250 as the S-polarized light beam. In summary, the intermediate light beam having a random polarization direction is converted into one type of polarized light beam (in this case, an S-polarized light beam) by the polarization separation unit array 230 and the selective phase difference plate 250. In the case of this example, an intermediate light beam with a random polarization direction is set to be aligned with an S-polarized light beam, but of course, it may be set to be aligned with a P-polarized light beam.
[0078]
An exit side lens 260 is disposed on the exit surface side of the selective phase difference plate 250, and the light beam aligned with the S-polarized light flux by the selective phase difference plate 250 is illuminated by an illumination side 290 (this example). In this case, the liquid crystal panels 411, 412, and 413 are led to a place where the liquid crystal panels 411, 412, and 413 are arranged, and are superimposed and coupled on the illumination area. Here, the exit side lens 260 does not have to be a single lens body, and may be an aggregate of a plurality of lenses like the first optical element 210.
[0079]
Therefore, when the functions of the second optical element 220 are summarized, the intermediate light beam 212 (that is, the image surface cut out by the light beam dividing lens 211) divided by the first optical element 210 is caused by the second optical element 220. The illumination areas 290 (in this example, liquid crystal panels 411, 412, and 413) are superimposed and coupled. At the same time, the intermediate light beam, which is a randomly polarized light beam, is spatially separated into two types of polarized light beams having different polarization directions by the polarization separation unit array 230 on the way, and one type of light passes through the selective phase difference plate 250. Almost all of the light reaches the illumination region 290 (in this example, the liquid crystal panels 411, 412, and 413). For this reason, the liquid crystal panels 411, 412, and 413 which are the illumination areas 290 are almost uniformly illuminated with almost one type of polarized light flux.
[0080]
Next, the relay optical device 430 that efficiently transmits the illumination light will be described with reference to FIG. 3 again. As described above, in the uniform polarization illumination optical device 200 incorporated in the projection display device 800 of this example, the region where uniform illumination light can be obtained is limited to a region separated from the light source unit 100 by a specific distance. Is done. Therefore, in the projection display device provided with the uniform polarization illumination optical device, the optical distance between the light source unit 100 and the liquid crystal panels 411, 412, and 413 is required to be equal. However, paying attention to the respective optical paths between the light source unit 100 and the respective liquid crystal panels 411, 412, and 413 in the projection display device 800, only the blue light has the other two color lights (red light and green light). The distance is longer than. Therefore, it is necessary to arrange light guide means for correcting the optical distance in the optical path of the blue light so that the optical distances of the three color lights (the distances between the light source unit 100 and the respective liquid crystal panels) are equal. is there.
[0081]
For the above reason, the relay optical device 430 mainly composed of the incident lens 431, the relay lens 432, and the emission lens 433 is disposed in the optical path of blue light as a light guide means. Accordingly, after the blue light passes through the green light reflecting dichroic mirror 402, it first passes through the incident lens 431 and the reflecting mirror 435, is guided to the relay lens 432, and is focused on the relay lens, and then is reflected by the reflecting mirror 436. Then, the light reaches the blue light liquid crystal panel 413.
[0082]
Next, for each of the liquid crystal panels 411, 412, and 413, the three diffraction gratings 491, 492, and 493 installed at the positions on the light incident side of the liquid crystal panel will be described. These diffraction gratings are the same surface relief type diffraction gratings as those of the second embodiment, and each diffraction grating is optimized according to the wavelength of incident light.
[0083]
In the projection display device 800 configured as described above, the uniform polarization illumination optical device 200 is used in place of the conventional general light source unit (for example, the light source unit 100 of the second embodiment), and thus the conventional projection. Compared to the type display device (for example, the projection type display device 900 described as the prior art), the light intensity of the illumination light that illuminates the liquid crystal panels 411, 412, and 413 is less uneven, and as the illumination light of the liquid crystal panel Since only light having substantially one kind of suitable polarization state can be used as illumination light, there is a feature that light projection in a polarizing plate (not shown) of the liquid crystal panel is small and a bright projection screen can be realized.
[0084]
However, on the other hand, since the uniform polarization illumination apparatus 200 includes a plurality of light beam splitting lenses 211, dark shadows are also generated at a plurality of locations according to the number of the light beam splitting lenses 211 arranged in the horizontal direction. As a result, the presence of this dark shadow is visually annoying, and the quality of the projected image is greatly reduced.
[0085]
Therefore, the above-described disadvantages are eliminated by arranging the three diffraction gratings 491, 492, 493 for each of the liquid crystal panels 411, 412, 413 at positions on the liquid crystal panel incident side. That is, the illumination light from the uniform polarization illumination device 200 is converted into a light beam having a specific angle component and slightly spreading as a whole by the diffraction action of light by the diffraction gratings 491, 492, and 493. Since each of the liquid crystal panels 411, 412, and 413 is illuminated with the light of, the light flux does not concentrate in the optically inhomogeneous region present in the central portion of the cross dichroic prism 450. Causes little local light loss when passing through. As a result, dark shadows (regions with locally reduced brightness) that are visually obtrusive due to structural problems of the cross dichroic prism rarely occur in the center of the projection screen.
[0086]
Also in the projection display device 800 of this example, since the diffraction gratings having different characteristics are arranged for each liquid crystal panel, the distance between the diffraction grating and the projection lens is shortened, and the light flux by the diffraction grating is reduced. Since the divergence angle T can be set large and the diffraction grating can be optimized according to the wavelength of the light beam incident on the diffraction grating, it is possible to effectively prevent the occurrence of dark shadows that occur in the center of the projection screen. .
[0087]
Further, in the projection display device having the uniform polarization illumination device 200 as in this example, a lamp having an extremely short arc length is often used as the light source lamp 110 in order to improve the illumination efficiency in the uniform polarization illumination device. Even in such a case, the use of a diffraction grating effectively prevents the occurrence of dark shadows caused by structural problems of the cross dichroic prism, and produces high-definition images without visual disturbances. This has the effect of allowing projection display.
[0088]
As described above, the effective use of the diffraction grating effectively prevents the occurrence of dark shadows on the projection screen due to the structural problem of the cross dichroic prism, with almost no reduction in the brightness of the projected image. Can be realized.
[0089]
In this example, three diffraction gratings having different characteristics are used. However, like the projection display apparatus 600 of the first embodiment, one diffraction grating is used as the uniform polarization illumination device 200 and the color light separating means. It is good also as a structure arrange | positioned between (dichroic mirror 401).
[0090]
Example 4
An embodiment in which a diffraction grating is introduced into a projection display device using a reflective liquid crystal panel as modulation means will be described. The diffraction grating 480 used in this example is the same as that used in the first embodiment.
[0091]
FIG. 6 is a schematic configuration diagram of the optical system portion of the projection display device 850 according to the fourth embodiment when viewed in plan. The projection display device 850 of this example mainly includes a light source unit 100, a diffraction grating 480, a polarization beam splitter 440 that selectively separates polarized light beams, a cross dichroic prism 450 that combines color light separation means and color light synthesis means, and modulation. It is mainly composed of three reflective liquid crystal panels 414, 415, and 416 as means and a projection lens 460 as a projection optical system.
[0092]
The random polarized light beam emitted from the light source unit 100 enters the polarization beam splitter 440 through the diffraction grating 480, and only the S-polarized light beam is selectively separated by the polarization beam splitter 440. That is, among the random polarized light beams incident on the polarization beam splitter 440, only the S-polarized light beam is reflected by the polarization separation surface 441 and enters the adjacent cross dichroic prism 450. On the other hand, the P-polarized light beam passes through the polarization separation surface 441 as it is and is emitted from the polarization beam splitter 440 (this P-polarized light beam does not become illumination light for illuminating the liquid crystal panel).
[0093]
The S-polarized light beam incident on the cross dichroic prism 450 is separated into three light beams of red light, green light, and blue light according to the wavelength by the cross dichroic prism 450, and the corresponding reflective red light liquid crystal panel 414. Then, the light reaches the reflective liquid crystal panel for green light 415 and the reflective liquid crystal panel for blue light 416 to illuminate the respective liquid crystal panels. That is, the cross dichroic prism 450 functions as color light separating means for illumination light that illuminates the liquid crystal panel.
[0094]
Here, since the liquid crystal panels 414, 415, and 416 used in this example are of the reflection type, each liquid crystal panel modulates each color light and includes display information from the outside corresponding to each color light. At the same time, the traveling direction of the light beam is substantially reversed while changing the polarization direction of the light beam emitted from each liquid crystal panel. Accordingly, the reflected light from each liquid crystal panel is emitted in a partially P-polarized state according to display information. The modulated light beams emitted from the respective liquid crystal panels 414, 415, and 416 enter the cross dichroic prism 450 again, are combined into one optical image, and enter the adjacent polarizing beam splitter 440. That is, the cross dichroic prism 450 acts as color light combining means for the modulated light beam emitted from the liquid crystal panel.
[0095]
Of the light beams incident on the polarization beam splitter 440, the light beams modulated by the liquid crystal panels 414, 415, and 416 are P-polarized light beams, and thus pass through the polarization separation surface 441 of the polarization beam splitter 440 as they are, and the projection lens 460. Then, an image is formed on the screen 470.
[0096]
In the projection display device 850 configured as described above, the respective reflective liquid crystal panels 414, 415, and 416 are illuminated by the action of the diffraction grating 480 installed between the light source unit 100 and the polarization beam splitter 440. The light has almost four specific angle components, and as a whole, the light beam is slightly spread. The optical images formed on the respective liquid crystal panels are combined again in the cross dichroic prism 450 to form a color optical image (video) on the screen 470. At this time, the light flux passing through the cross dichroic prism 450 However, the light beam has almost four specific angle components and slightly spreads as a whole. Accordingly, even when the illumination light that illuminates the liquid crystal panel passes through the cross dichroic prism 450, or when the modulated light beam modulated by the liquid crystal panel passes through the cross dichroic prism 450, in any case, Since the light flux does not concentrate in the optically inhomogeneous region in the center of the cross dichroic prism 450, it passes through the cross dichroic prism and forms an optical image on the screen with little local light loss. can do. Therefore, there is no dark shadow (region where brightness is locally reduced) that is visually obtrusive at the center of the projection screen.
[0097]
In designing the diffraction grating, the spread angle T of the light beam by the diffraction grating is set so that all of the light beam slightly spread by the diffraction grating enters the entrance pupil of the projection lens. There is almost no decrease in brightness due to installation.
[0098]
Therefore, the projection display device having the reflective liquid crystal panel as in this example is also effective in using the diffraction grating as in the case of the projection display device having the transmissive liquid crystal panel. Therefore, it is possible to effectively prevent the occurrence of dark shadows generated on the projection screen due to the structural problem of the cross dichroic prism without substantially reducing the brightness of the projection image, thereby realizing a high-quality projection image.
[0099]
【The invention's effect】
As described above, according to the present invention, even in a projection display device using a cross dichroic prism as color light combining means, or when a lamp having a very short arc length is used as a light source, the diffraction grating is modulated with the light source. By disposing on the optical path between the means, it is possible to prevent the occurrence of dark shadows due to structural problems of the cross dichroic prism, and to project and display a high-quality image without visual disturbance.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an optical system of a projection display apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a schematic configuration diagram showing an optical system of a projection display apparatus according to Embodiment 2 of the present invention.
FIG. 3 is a schematic configuration diagram showing an optical system of a projection display apparatus according to Embodiment 3 of the present invention.
FIG. 4 is an explanatory diagram for explaining the configuration and function of a uniform polarization illumination optical system used in a projection display apparatus according to Example 3 of the invention.
FIG. 5 is an external view showing a first optical element used in a projection display apparatus according to Embodiment 3 of the present invention.
FIG. 6 is a schematic configuration diagram showing an optical system of a projection display apparatus according to Embodiment 4 of the present invention.
FIG. 7 is a schematic diagram showing a diffraction state of light passing through a diffraction grating.
FIG. 8 is a schematic diagram showing a cross-sectional shape of a surface relief type diffraction grating.
FIG. 9 is a schematic diagram showing a cross-sectional shape of a distributed refractive index type diffraction grating.
FIG. 10 is a schematic diagram showing a general structure of a cross dichroic prism.
FIG. 11 is a schematic configuration diagram showing an optical system of a conventional representative three-plate projection display device.
[Explanation of symbols]
10 ... Diffraction grating
11 ... Surface relief type diffraction grating
12 ... Uneven shape
13: Distributed refractive index type diffraction grating
14: Refractive index distribution
20: Light incident on the diffraction grating
21 ... 0th order light
22 ... + 1st order light
23 ...- 1st order light
24 ... + secondary light
25 ... -Secondary light
100: Light source section
110: Light source lamp
120 ... Parabolic reflector
200: Uniformly polarized illumination device
210... First optical element
211 ... Flux splitting lens
212 ... Intermediate luminous flux
213 ... Condensed image
220 ... Second optical element
230... Polarization separation unit array
231 ... Polarization separation unit
232: Polarized light separation surface
233 ... Reflecting surface
240 ... Condensing lens array
241 ... Condensing lens
250 ... Selected phase difference plate
251 ... λ / 2 phase difference plate
260... Exit side lens
290 ... Illumination area
401... Blue light green light reflecting dichroic mirror
402... Green light reflecting dichroic mirror
411 ... Liquid crystal panel for red light (light transmission type)
412 ... Green light liquid crystal panel (light transmission type)
413 ... Blue light liquid crystal panel (light transmission type)
414 ... Liquid crystal panel for red light (light reflection type)
415 ... Green light liquid crystal panel (light reflection type)
416 ... Liquid crystal panel for blue light (light reflection type)
430 ... Relay optical device
431 ... Incident lens
432 ... Relay lens
433 ... Outgoing lens
435, 436 ... Reflection mirror
440 ... Polarizing beam splitter
441: Polarized light separation surface
450 ... Cross dichroic prism
451 ... Prism
452 ... Dichroic membrane
453 ... Optical adhesive
454: The part where the dichroic film intersects in an X-shape
455 ... Square surface
456: Optically inhomogeneous region
460 ... Projection lens
470 ... screen
480 ... Diffraction grating
491 ... Red light diffraction grating
492 ... Green light diffraction grating
493 ... Diffraction grating for blue light
600, 700, 800, 850, 900... Projection display device

Claims (11)

A light source, color light separating means for separating a light beam from the light source into three color light beams, three modulating means for modulating each of the light beams separated by the color light separating means, and the light source and the modulating means. A diffractive grating disposed on the optical path in between, a multi-layer film that synthesizes a plurality of light beams modulated by the respective modulation means into one in an X shape, and a color light synthesis means A projection display system having a projection optical system for projecting the combined luminous flux,
The projection display device according to claim 1, wherein the diffraction grating is a one-dimensional diffraction grating that generates high-order light in a direction orthogonal to a direction in which a region where the multilayer films intersect in the color light combining unit exists.   2. The projection display device according to claim 1, wherein a diffraction grating is disposed at each of the three modulation means at a position on the light incident side of the modulation means.   2. The projection display device according to claim 1, wherein the diffraction grating is a surface relief type diffraction grating.   2. The projection display device according to claim 1, wherein the diffraction grating is a distributed refractive index type diffraction grating. A light source, a first optical element that collects a light beam emitted from the light source and converts the light beam into a plurality of spatially separated intermediate light beams, and a first optical element disposed near a position where the intermediate light beam converges Two optical elements, color light separating means for separating the light beam emitted from the second optical element into three color light beams, and three modulating means for modulating each of the light beams separated by the color light separating means, A color light combining means in which a diffraction grating disposed on an optical path between the light source and the modulation means, and a multilayer film for combining a plurality of light beams modulated by the respective modulation means are crossed in an X shape, Projection means for projecting a light beam synthesized by the color light synthesizing means, wherein the second optical element is configured to space each of the intermediate light beams into a P-polarized light beam and an S-polarized light beam. Separated polarized light A polarization generator comprising: a separating unit; and a polarization direction converting unit configured to align a polarization direction of any one of the P-polarized light beam and the S-polarized light beam with a polarization direction of the other polarized light beam, and an output surface of the polarization generator And superimposing and coupling means for superimposing and coupling the intermediate light beams,
The projection display device according to claim 1, wherein the diffraction grating is a one-dimensional diffraction grating that generates high-order light in a direction orthogonal to a direction in which a region where the multilayer films intersect in the color light combining unit exists.   6. The projection display device according to claim 5, wherein a diffraction grating is disposed at each of the three modulation means at a position on the light incident side of the modulation means.   6. The projection display device according to claim 5, wherein the diffraction grating is a surface relief type diffraction grating.   6. The projection display device according to claim 5, wherein the diffraction grating is a distributed refractive index type diffraction grating. A light source, color light separating means for separating a light beam emitted from the light source into light beams of three colors, three modulating means for modulating each of the light beams separated by the color light separating means, the light source and the modulating means A diffraction grating arranged on the optical path between the color light combining unit, a color light combining unit that combines a plurality of light beams modulated by the respective modulation units, and a projection unit that projects the light beam combined by the color light combining unit. The color light separating means and the color light synthesizing means commonly use a dichroic prism having a multilayer film intersecting in an X shape, and the modulating means is composed of a reflective liquid crystal device.
The projection display device according to claim 1, wherein the diffraction grating is a one-dimensional diffraction grating that generates high-order light in a direction orthogonal to a direction in which a region where the multilayer films intersect in the color light combining unit exists.   10. The projection display device according to claim 9, wherein the diffraction grating is a surface relief type diffraction grating.   10. The projection display device according to claim 9, wherein the diffraction grating is a distributed refractive index type diffraction grating.

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