JP4273642B2 - Single-panel LCD projector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a single plate type liquid crystal projector, and more particularly to a microlens-dichroic mirror type color liquid crystal projector.
[0002]
[Prior art]
A general single-panel liquid crystal projector uses R (red), G (green), and B (blue) color filters. However, since the color filter absorbs light, the light use efficiency is lowered. In the so-called microlens-dichroic mirror system, such a problem does not occur because a color filter is not used. According to this method, the light from the lamp is separated into RGB color lights having different angles by the dichroic mirror. Then, the light enters the microlens arranged for each pixel of the liquid crystal panel, and is condensed at different positions for each color light to illuminate each pixel of RGB. Various single-plate liquid crystal projectors employing this method have been proposed in the past (Japanese Patent Laid-Open Nos. 11-32348, 11-202429, etc.).
[0003]
[Problems to be solved by the invention]
In a microlens-dichroic mirror type liquid crystal projector, the numerical aperture (NA) of each color light needs to be reduced in the color separation direction. This is because when the NA is large, color mixing occurs in adjacent pixels, resulting in a decrease in color reproducibility. On the other hand, if the NA is too small, only a part of the light flux from the lamp can be used for illumination in the color separation direction, and the light utilization efficiency decreases.
[0004]
The present invention has been made in view of such a situation, and provides a single-plate liquid crystal projector capable of increasing light utilization efficiency while maintaining good color reproducibility and obtaining a bright and high-quality projected image. With the goal.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, a liquid crystal projector according to a first aspect of the present invention includes a light source that generates white natural light, a shape conversion optical system that converts light emitted from the light source into parallel light, and a spatial light of the parallel light. A lens array integrator optical system for uniforming a uniform energy distribution, a color separation optical system for color-separating the light with uniform energy distribution into a plurality of color lights having an angle difference, and a side on which each color light is incident A single plate type comprising a microlens array on the surface of the display area, a liquid crystal panel that modulates light after passing through the microlens array, and a projection lens that projects an image with the light modulated by the liquid crystal panel A liquid crystal projector, wherein the integrator optical system divides incident light by a plurality of lens cells to form a plurality of light source images, and the first lens array The second lens array has the same number of lens cells as conjugates of the lens cells and the liquid crystal panel so as to form a pair with the lens cells of the first lens array, and is further formed by the first lens array. A polarization separation element that separates incident light into two polarization components having different polarization directions, and one of the polarization components so that the light source image formed is formed as a pair of adjacent light source images having different polarization directions. A half-wave plate for converting into a polarization component having the same polarization direction as the other polarization component, and the shape conversion optical system converts the light emitted from the light source into parallel light at a different compression ratio depending on the direction , The display area of the liquid crystal panel has a rectangular shape, and the compression rate differs between a direction corresponding to the long side of the rectangle and a direction corresponding to the short side, and the direction in which the compression rate is large, and the liquid crystal panel And the direction of color separation by the color separation optical system is parallel to the same plane, and the direction of separation into two polarization components by the polarization separation element is relative to the plane. and wherein the vertical der Rukoto Te.
[0007]
The liquid crystal projector according to a second aspect of the present invention is the liquid crystal projector according to the first aspect, wherein the ratio of the parallel light compression ratio is 2α / β: when the aspect ratio of the display area is α: β (where α> β). It is characterized by 1.
[0008]
A liquid crystal projector according to a third aspect of the present invention is the liquid crystal projector according to the first or second aspect , wherein the shape conversion optical system includes a reflector having a paraboloid having a focal point at the light source position as a reflection surface, It comprises a convex cylindrical lens that converges parallel light only in one direction, and a concave cylindrical lens that returns a light beam converged only in one direction by the convex cylindrical lens back to parallel light.
[0009]
In a liquid crystal projector according to a fourth aspect of the present invention, in the configuration of the first or second aspect , the shape conversion optical system reflects an anamorphic aspherical surface having a focal point at the light source position and different curvatures in the horizontal direction and the vertical direction. It is characterized by comprising a reflector having a surface, and a concave cylindrical lens having lens surfaces having different curvatures in the horizontal direction and the vertical direction in order to convert the light beam from the reflector into parallel light.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a single-plate type liquid crystal projector embodying the present invention will be described with reference to the drawings. Note that the same or corresponding parts in the embodiment and the like are denoted by the same reference numerals, and redundant description is omitted as appropriate.
[0011]
FIG. 1 is a sectional view showing an embodiment of a color liquid crystal projector of a microlens-dichroic mirror system. FIG. 1B shows a cross section of the entire liquid crystal projector as viewed from the long side (α) side of the liquid crystal panel (13) {that is, from a direction parallel to the short side (β)}. On the other hand, FIG. 1A shows a substantially L-shaped optical path shown in FIG. 1B developed in one direction. That is, FIG. 1A shows a section from the light source (1) to the dichroic mirror (11) as viewed from the direction perpendicular to the display surface of the liquid crystal panel (13). Up to (14) is shown in a cross section viewed from the short side (β) side of the liquid crystal panel (13) {that is, from a direction parallel to the long side (α)}.
[0012]
The liquid crystal projector includes a light source (1), a reflector (2a), a UV (ultraviolet ray) -IR (infrared ray) cut filter (3), a convex cylindrical lens (4), a concave cylindrical lens (5a), in the order of the optical path. First lens array (6), second lens array (7), PBS (polarizing beam splitter) prism array (8), half-wave plate (9), superposition lens (10), dichroic mirror (11), A field lens (12), a liquid crystal panel (13), and a projection lens (14) are provided. Among these, the reflector (2a) and the convex and concave cylindrical lenses (4, 5a) are the shape conversion optical system, and the first and second lens arrays (6, 7) and the overlapping lens (10) are the lens array type. The integrator optical system, PBS prism array (8) and half-wave plate (9) constitute a polarization conversion optical system, and dichroic mirror (11) constitutes a color separation optical system.
[0013]
The light source (1) is a discharge lamp (for example, a metal halide lamp or an ultrahigh pressure mercury lamp) that generates white natural light (random polarization). In particular, an ultra-high pressure mercury lamp is a short arc, which is desirable for improving illumination efficiency. The reflector (2a) has a parabolic surface having a focal point at the position of the light source (1) as a reflecting surface. Therefore, the light emitted from the light source (1) is converted into parallel light by the reflector (2a). The parallel light emitted from the reflector (2a) passes through the UV-IR cut filter (3) and then passes through the convex cylindrical lens (4) and the concave cylindrical lens (5a).
[0014]
Convex cylindrical lens (4) and concave cylindrical lens (5a) act as an afocal system in the horizontal direction (H) for incident parallel light but as a simple parallel plate in the vertical direction (V). To do. Accordingly, the parallel light transmitted through the UV-IR cut filter (3) is converged only in the horizontal direction (H) by the convex cylindrical lens (4), and the converged light beam is again collimated by the concave cylindrical lens (5a). Returned to In this way, the light from the light source (1) is converted into parallel light compressed in the horizontal direction (H) by the shape conversion optical system including the cylindrical lenses (4, 5a) and the like.
[0015]
The parallel light emitted from the concave cylindrical lens (5a) is incident on the first and second lens arrays (6, 7). The first lens array (6) is formed by arranging rectangular lens cells that are substantially similar to the display area of the liquid crystal panel (13) in a two-dimensional array, and divides incident light by a plurality of lens cells. To do. Then, a plurality of light source images are formed in the vicinity of the second lens array (7) having the same array structure as the first lens array (6). The second lens array (7) has the same number of lens cells of the same shape that are paired with the lens cells of the first lens array (6). Each lens cell of the first lens array (6) and the liquid crystal panel (13) are in a conjugate relationship via each lens cell of the second lens array (7), and each lens of the first lens array (6). The illumination light is collected by the overlapping lens (10) so that the conjugate images of the cells overlap on the liquid crystal panel (13). In this way, the spatial energy distribution of the illumination light is made uniform, and the liquid crystal panel (13) is illuminated uniformly without waste.
[0016]
The illumination light emitted from the second lens array (7) enters the PBS prism array (8). The PBS prism array (8) is a polarization separating element having PBS prisms in an array in the vertical direction (V). Each PBS prism has a polarization separation surface that separates incident illumination light into P-polarized light (transmitted light) and S-polarized light (reflected light), and a reflective surface that reflects S-polarized light in the same direction as P-polarized light. is doing. Therefore, incident light is separated into two polarization components (P-polarized light and S-polarized light) having different polarization directions, and the light source image formed by the first lens array (6) is a pair of light sources adjacent to each other with different polarization directions. It is formed as an image (P image and S image). A half-wave plate (9) is provided at the position where the S-polarized light is incident on the surface of the PBS prism array (8) on the light emission side. Since the S-polarized light and the P-polarized light are imaged at positions shifted from each other, only the S-polarized light can be incident on the half-wave plate (9). One polarization component (S-polarized light) passes through the half-wave plate (9) and is converted to a polarization component (P-polarized light) having the same polarization direction as the other polarization component (P-polarized light) (the polarization plane is Approximately 90 ° rotation).
[0017]
As described above, the illumination light is converted from random polarized light to linearly polarized light with a uniform polarization direction by the polarization conversion optical system comprising the PBS prism array (8) and the half-wave plate (9). P-polarized light. Since the polarization conversion optical system is configured in combination with the integrator optical system, illumination can be performed with almost no shift of the central axis of illumination light having a strong energy distribution for both illumination light with both P and S polarizations. Therefore, it is efficient in illuminating the liquid crystal panel (13) with the microlens array (ML, FIG. 2), and uniform illumination light can be obtained by the integrator function.
[0018]
The illumination light whose polarization direction is aligned by the polarization conversion optical system passes through the superposing lens (10) and then enters the three dichroic mirrors (11) arranged with an angle difference. The dichroic mirror (11) separates incident light (white light) into each color light of three primary colors RGB having an angle difference. Each color light of RGB generated by color separation in the dichroic mirror (11) passes through the field lens (12) and then illuminates the liquid crystal panel (13) as shown in FIG. The field lens (12) achieves telecentricity toward the liquid crystal panel (13).
[0019]
The liquid crystal panel (13) has a rectangular display area, and RGB light (in FIG. 2, R: broken line, G: solid line, B: two-dot chain line) is incident on the side where light beams are incident at different angles. A microlens array (ML) is provided on the surface of the display area. Then, the light after passing through the microlens array (ML) is modulated by the liquid crystal layer (LC). Since the polarizer (not shown) of the liquid crystal panel (13) is arranged in a direction that transmits the P-polarized light, there is almost no light loss due to the polarizer, and the liquid crystal panel (13) is illuminated with high light utilization efficiency. Achievable. Each lens cell of the microlens array (ML) is arranged for each set of RGB pixel units of the liquid crystal layer (LC), and each color light of RGB is incident on each lens cell with an angle difference. For this reason, the illumination light is imaged at different positions for each of the RGB color lights, and the pixels corresponding to the respective colors are illuminated efficiently. Then, the projection lens (14) projects an image with the light modulated by the liquid crystal panel (13), and a display image on the liquid crystal panel (13) is projected on a screen (not shown).
[0020]
In the color separation direction shown in FIG. 1B, since the illumination light is angularly separated into RGB color lights, the numerical aperture (NA) of the entire illumination light is three times that of a single color (R, G, B). . Therefore, if the NA of the incident light to the dichroic mirror (11) in the color separation direction is not set to 1/3 or less of the non-color separation direction shown in FIG. The color reproducibility is reduced and the NA tripled cannot be picked up by the projection lens (14) (for example, only 1/3 can be used), resulting in loss of light use efficiency and color unevenness. become. In order to solve this problem, in the present liquid crystal projector, the shape conversion optical system is configured to convert the light emitted from the light source (1) into parallel light at different compression rates depending on directions. In other words, in the display area of the liquid crystal panel (13), the beam width of the parallel light emitted from the reflector (2a) is compressed in the horizontal direction (H) by an afocal system composed of a cylindrical lens system (4, 5a). The compression rate is different between the horizontal direction (H) corresponding to the long side (α) and the vertical direction (V) corresponding to the short side (β).
[0021]
With the above configuration, the NA of the illumination light can be reduced to 1/3 without reducing the amount of light taken in from the light source (1). Therefore, it is possible to increase the light use efficiency while maintaining good color reproducibility, and obtain a bright and high-quality projected image. The direction in which the compression rate is large {that is, the horizontal direction (H)}, the long side (α) of the display area of the liquid crystal panel (13), and the direction of color separation by the dichroic mirror (11) are the same plane. The direction of separation of the two polarization components (P, S polarization) by the PBS prism array (8) {ie, the vertical direction (V)} is perpendicular to the plane. It has become.
[0022]
FIG. 3 (A) shows the light beam capturing range from the reflector (2a) in the liquid crystal projector by cross hatching, and FIG. 3 (B) shows each lens cell of the second lens array (7) in the liquid crystal projector and its lens cell. The positional relationship between the P image (IP) formed in the vicinity and the half-wave plate (9) is shown. Also, FIG. 4A shows the cross-hatching of the light flux capturing range from the reflector 2a when the cylindrical lens system 4,5a is not used in the liquid crystal projector, and FIG. When the cylindrical lens system (4, 5a) is not used in the liquid crystal projector, the P image (IP) and the half-wave plate (9) formed in the vicinity of each lens cell of the second lens array (7) The positional relationship is shown. Since the polarization separation direction by the PBS prism array (8) is the vertical direction (V), the S image (not shown) is formed in the region (hatched portion) of the half-wave plate (9).
[0023]
As can be seen by comparing the shapes of the P image (IP) shown in FIGS. 3B and 4B, the light source image formed in the vicinity of the second lens array 7 in this liquid crystal projector is in the horizontal direction (H ) Become longer. This is because the cylindrical lens system (4, 5a) compresses the beam width only in the horizontal direction (H), and the difference in compression rate in each direction (H, V) is a magnification difference corresponding to that ratio (i.e., compression ratio). Because it appears as That is, the length of the light source image in the light beam compression direction is determined according to the afocal magnification of the cylindrical lens system (4, 5a).
[0024]
Here, if the aspect ratio of the liquid crystal panel (13) is 4: 3, the aspect ratio of the first and second lens arrays (6, 7) is also about 4: 3. Two light source images are formed for one lens cell in the vicinity of the second lens array (7), and the polarization separation direction thereof is the horizontal direction corresponding to the long side (α) of the liquid crystal panel (13) ( H), the aspect ratio of the area effective for one light source image is 2: 3. As shown in FIG. 3B, if the polarization separation direction is the vertical direction (V) corresponding to the short side (β) direction of the liquid crystal panel (13), the aspect ratio of the effective area for one light source image is obtained. Becomes 8: 3. Since the size of the light source image is about three times larger in the direction {that is, the horizontal direction (H)} in which the light beam is compressed, the vertical direction (V) perpendicular thereto is the polarization separation direction. The matching with the shape of the effective region of the luminous flux in the vicinity of the two-lens array (7) is good, and therefore efficient illumination is possible. In the case of the present liquid crystal projector, when the light beam compression ratio is set to 8: 3, matching between the shape of the light source image and the shape of the effective light beam region in the vicinity of the second lens array (7) is best.
[0025]
Also, when the aspect ratio of the liquid crystal panel (13) is 16: 9, it is effective for one light source image when the polarization separation direction is the vertical direction (V) corresponding to the short side (β) direction of the liquid crystal panel (13). When the compression ratio is 32: 9, matching between the shape of the light source image and the shape of the luminous flux effective region in the vicinity of the second lens array (7) is the best. From this viewpoint, when the aspect ratio of the display area of the liquid crystal panel (13) is α: β (where α> β), the ratio of the parallel light compression ratio is preferably 2α / β: 1. By setting the compression ratio in this manner, matching between the shape of the light source image and the shape of the light flux effective region in the vicinity of the second lens array (7) is improved, and efficient illumination is possible.
[0026]
FIG. 5 is a sectional view showing another embodiment of the liquid crystal projector according to the present invention. FIG. 5B shows the entire liquid crystal projector as viewed from the long side (α) side of the liquid crystal panel (13) {that is, from a direction parallel to the short side (β)}. On the other hand, FIG. 5A shows the substantially L-shaped optical path shown in FIG. 5B developed in one direction. That is, FIG. 5A shows a section from the light source (1) to the dichroic mirror (11) as viewed from the direction perpendicular to the display surface of the liquid crystal panel (13). Up to (14) is shown in a cross section viewed from the short side (β) side of the liquid crystal panel (13) {that is, from a direction parallel to the long side (α)}.
[0027]
This liquid crystal projector includes a light source (1), a reflector (2b), a UV-IR cut filter (3), a concave cylindrical lens (5b), a first lens array (6), a birefringent diffractive optical element (15) in the order of the optical path. ), Second lens array (7), half-wave plate (9), superposition lens (10), dichroic mirror (11), field lens (12), liquid crystal panel (13), and projection lens (14) It has. Among these, the reflector (2b) and the concave cylindrical lens (5b) are the shape converting optical system, the first and second lens arrays (6, 7) and the superposing lens (10) are the lens array integrator optical system, the compound optical system. The refractive diffraction optical element (15) and the half-wave plate (9) constitute a polarization conversion optical system, and the dichroic mirror (11) constitutes a color separation optical system.
[0028]
The first feature of this liquid crystal projector is that the reflector (2b) has the function of a convex cylindrical lens in the shape conversion optical system. The reflector (2b) has an anamorphic aspheric surface having a focal point at the position of the light source (1) and having different curvatures in the horizontal direction (H) and the vertical direction (V) as a reflecting surface. The anamorphic aspheric shape is a parabola in the cross section shown in FIG. 5 (A), and is elliptical in the cross section shown in FIG. 5 (B). The concave cylindrical lens (5b) has an anamorphic aspherical lens surface with different curvatures in the horizontal direction (H) and vertical direction (V) in order to convert the light beam from the reflector (2b) into parallel light. is doing. The anamorphic aspheric shape is a straight line in the cross section shown in FIG. 5A, and is circular in the cross section shown in FIG. Further, the curvature of the circle becomes maximum on the optical axis and gradually changes as the distance from the optical axis increases in the vertical direction (V). By using an anamorphic aspherical surface in this way, a convex cylindrical lens is not necessary, and the number of parts can be reduced. Further, the above-described compression of the light beam width is effectively achieved.
[0029]
The second feature of this liquid crystal projector is that a birefringent diffractive optical element (15) is used as a polarization separating element. The birefringent diffractive optical element (15) includes an optically anisotropic layer (for example, liquid crystal) made of a birefringent material and an optically isotropic layer (for example, a glass substrate) adjacent to the optically anisotropic layer on the diffraction grating surface. ), And polarization separation is performed by the birefringence action and the diffraction action. For example, P-polarized light passes through the birefringent diffractive optical element (15) as it is without being diffracted on the diffraction grating surface, and S-polarized light is deflected by diffraction on the diffraction grating surface. Then, due to the polarization separation, the image forming position (that is, the light source image position) is shifted in the direction perpendicular to the optical axis between the P polarized light and the S polarized light, and only the S polarized light passes through the half-wave plate (9). Become.
[0030]
By the way, in the configuration in which the illumination light is compressed and then incident on the first lens array (6), the number of divisions in the compression direction tends to be small, and it is necessary to make each lens cell small for uniform illumination. Arise. Therefore, the number of lens cells in the polarization separation direction is considerably increased, and when the PBS prism array (8) is used as shown in FIG. 1, the number of PBS prisms constituting the same is increased. Therefore, since the number of parts to configure increases, there is a concern about cost increase. If the birefringent diffractive optical element (15) is used as shown in FIG. 5, it is possible to perform polarization separation without depending on the number of lens cells, and the birefringent diffractive optical element (15) has very few parts. Since it can be configured by the number of points, low-cost polarization separation can be effectively performed. For example, if a liquid crystal, which is a birefringent material, is sealed between a glass substrate and a diffraction grating substrate, a low-cost birefringent diffractive optical element (15) can be configured with a very small number of parts.
[0031]
The third feature of the liquid crystal projector is that the half-wave plate (9) provided on the light emitting side surface of the second lens array (7) is not a polymer film but an amorphous birefringent thin film. It is in the point which is comprised. When the number of lens cells in the polarization separation direction is increased, the number of half-wave plates is also increased. Therefore, when the half-wave plate is formed of a polymer film, the number of attaching steps increases and the cost is increased. Further, since the lens cell size is reduced, the influence of the error in the pasting position is also increased. Since the amorphous birefringent thin film is formed by vapor deposition, the half-wave plate (9) made of the amorphous birefringent thin film can be formed at one time, and the error of the position where the half-wave plate (9) is formed is reduced. It is also effective in reducing the size.
[0032]
【The invention's effect】
As described above, according to the present invention, the shape conversion optical system is configured to convert the light emitted from the light source into parallel light at different compression ratios depending on the direction. It is possible to increase the utilization efficiency and obtain a bright and high-quality projected image.
[Brief description of the drawings]
FIG. 1 is an optical configuration diagram showing a cross section of an embodiment of a liquid crystal projector.
2 is a cross-sectional view showing a main part structure of a liquid crystal panel and an optical path of each color light in the liquid crystal projector of FIG. 1;
FIG. 3 is a diagram schematically showing a light flux capturing range from a light source and a light flux effective area in the vicinity of a second lens array in the liquid crystal projector of FIG. 1;
4 is a diagram schematically illustrating a light beam capturing range from a light source and a light beam effective region in the vicinity of a second lens array when the cylindrical lens system is not used in the liquid crystal projector of FIG.
FIG. 5 is a cross-sectional view of an optical configuration of another embodiment of a liquid crystal projector.
[Explanation of symbols]
1… Light source
2a… Reflector
2b… Reflector
4 ... Convex cylindrical lens
5a ... Concave cylindrical lens
5b ... Concave cylindrical lens
6 ... 1st lens array
7… Second lens array
8… PBS prism array
9… 1/2 wave plate
10 ... Overlapping lens
11… Dichroic mirror
13 ... LCD panel
ML ... Micro lens array
14 ... Projection lens
15 ... Birefringent diffractive optical element

Claims (4)

A light source that generates white natural light; a shape conversion optical system that converts light emitted from the light source into parallel light; a lens array integrator optical system that uniformizes a spatial energy distribution of the parallel light; and A color separation optical system for color-separating light having a uniform energy distribution into a plurality of color lights having an angle difference; and a microlens array on a surface of a display area on which each color light is incident, the microlens array A single-plate liquid crystal projector comprising: a liquid crystal panel that modulates light after passing; and a projection lens that projects an image with light modulated by the liquid crystal panel,
The integrator optical system divides incident light by a plurality of lens cells to form a plurality of light source images, and a lens cell that conjugates each lens cell of the first lens array and the liquid crystal panel. A second lens array having the same number to form a pair with each lens cell of the first lens array,
Further, polarization separation that separates incident light into two polarization components having different polarization directions so that a light source image formed by the first lens array is formed as a pair of adjacent light source images having different polarization directions. An element and a half-wave plate for converting one polarization component of the element into a polarization component having the same polarization direction as the other polarization component,
The shape conversion optical system converts light emitted from the light source into parallel light at different compression rates depending on directions ,
The display area of the liquid crystal panel has a rectangular shape, and the compression ratio differs between the direction corresponding to the long side and the direction corresponding to the short side of the rectangle, and the direction in which the compression ratio is large, and the display of the liquid crystal panel The long side of the region and the direction of color separation by the color separation optical system are parallel to the same plane, and the separation direction into two polarization components by the polarization separation element is perpendicular to the plane. a liquid crystal projector according to claim Rukoto Oh. Wherein the aspect ratio of the display area alpha: beta (but alpha> beta) to the time, the ratio of the compression ratio of the parallel light 2.alpha / beta: a liquid crystal projector according to claim 1, wherein the 1. The shape conversion optical system includes a reflector having a paraboloid having a focal point at the light source position as a reflection surface, a convex cylindrical lens for converging parallel light from the reflector in only one direction, and the convex cylindrical lens in one direction. 3. A liquid crystal projector according to claim 1, further comprising: a concave cylindrical lens that returns the light beam focused only on the light to parallel light. The shape conversion optical system has a reflector having an anamorphic aspheric surface having a focal point at the light source position and different curvatures in the horizontal direction and the vertical direction as a reflecting surface, and a horizontal direction for converting the light flux from the reflector into parallel light 3. The liquid crystal projector according to claim 1 , wherein the liquid crystal projector comprises a concave cylindrical lens having lens surfaces having different curvatures in the vertical direction.

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