JPWO1997045768A1 - Projection display device - Google Patents

Abstract

(57) [Abstract] A projection display device (1) is generally composed of a polarized lighting device (100), a polarized beam splitter (200), a reflective liquid crystal device, and a projection optical system (500). The polarized lighting device (100) includes a light source unit (110), a first optical element (120), and a second optical element (130). Light emitted from the light source unit (110) is split into multiple intermediate beams by the first optical element (120), and then converted into a polarized beam having approximately one polarization direction by the second optical element (130). This polarized beam is reflected by the polarized beam splitter (200), modulated by the reflective liquid crystal device (300), and then projected onto a projection surface (600) via the projection optical system (500). This projection display device shortens the length of the optical path to prevent light loss and reduces uneven illuminance across the illuminated area, resulting in a bright, high-quality projected image with uniform brightness.

Description

[Detailed Description of the Invention] Projection Display Device Technical Field The present invention relates to a projection display device that projects and displays an image formed by a reflective modulation element, such as a reflective liquid crystal device, onto a projection surface.

BACKGROUND ART Today, projection display devices using liquid crystal devices as light valves are well known as a method for displaying large-screen images. Figure 14 shows a typical configuration of a projection display device using three liquid crystal devices. The light source unit 110 is composed of a light source lamp 111 and a parabolic reflector 112. Light emitted from the light source lamp 111 is reflected by the parabolic reflector 112 and incident on a dichroic mirror 401. The light is then separated into three colors—red, green, and blue—by two wavelength-selective dichroic mirrors 401 and 402. The light then strikes the corresponding transmissive liquid crystal devices 301R, 301G, and 301B. The light transmitted through each transmissive liquid crystal device is combined by a cross dichroic prism 420 and projected onto a projection surface 600 via a projection optical system 500. The red light path and the blue light path are provided with reflecting mirrors 403, 404, and 405 that reflect the light beams.

Here, the cross dichroic prism 420 used as the color light combining means has dichroic films arranged in an X-shape. The color light combining means of a projection display device using three liquid crystal devices can also be achieved by arranging two dichroic mirrors in parallel instead of the cross dichroic prism 420. However, using the cross dichroic prism 420 shortens the distance between the liquid crystal devices 301R, 301G, and 301B and the projection optical system 500 compared to arranging two dichroic mirrors in parallel, which has the advantage of producing a bright projected image without using a large-diameter projection lens.

However, in conventional projection display devices, although the light path can be shortened by using cross dichroic prism 420 in the light combining section, the light separation section uses dichroic mirrors 401 and 402 and reflecting mirrors 403, 404, and 405, resulting in a fairly long light path. As a result, conventional projection display devices experience significant light loss in the light separation process, and are unable to fully utilize the characteristics of cross dichroic prism 420.

Furthermore, the light beam emitted from the light source unit 110, which is comprised of the light source lamp 111 and the parabolic reflector 112, has a non-uniform light intensity distribution within the cross section of the light beam, with the light intensity of the illumination light being high near the optical axis of the light source and decreasing with increasing distance from the optical axis. Therefore, in the conventional projection display device shown in Figure 14, the light intensity distribution of the illumination light in the illuminated areas (liquid crystal devices 301R, 301G, and 301B) is non-uniform, resulting in uneven brightness and color in the image projected onto the projection surface 600.

Therefore, an object of the present invention is to provide a projection display device that can obtain brighter projected images without using a large-diameter projection lens by shortening the length of the optical path and preventing light loss.

Another object of the present invention is to provide a projection display device that reduces the non-uniformity of the light intensity distribution of illumination light in an illuminated area, thereby achieving uniform brightness and high image quality.

DISCLOSURE OF THE INVENTION A first projection display device of the present invention comprises a light source, a first optical element that condenses a light beam from the light source and splits it into multiple intermediate light beams, a second optical element disposed on the light-exiting surface side of the first optical element, and a single reflective modulation element that modulates the light emitted from the second optical element. The second optical element splits each of the intermediate light beams into a P-polarized light beam and an S-polarized light beam, and aligns the polarization direction of one of the P-polarized light beam and the S-polarized light beam with the polarization direction of the other polarized light beam. a polarization conversion element that outputs the intermediate beams on the light output surface of the polarization conversion element, and a superposition combining element that is disposed on the light output surface side of the polarization conversion element and superposes and combines each of the intermediate beams onto the reflective modulation element; and a polarized beam selecting element is provided on the optical path between the second optical element and the reflective modulation element, which reflects or transmits the light output from the second optical element to reach the reflective modulation element, and transmits or reflects the light modulated by the reflective modulation element to reach the projection optical system.

The above-described configuration of the first projection display device of the present invention allows the optical path to be extremely short, minimizing light loss. This makes it possible to obtain extremely bright projected images without using a large-diameter projection lens.

The first optical element can be, for example, a lens array consisting of multiple beam-splitting lenses arranged in a matrix. By using such a lens array to split the light beam from the light source into multiple intermediate beams and then superimposing and combining these intermediate beams on the illuminated area, it is possible to reduce unevenness in illuminance compared to a single beam. Therefore, even if the light beam emitted from the light source has a non-uniform light intensity distribution within its cross section, it is possible to obtain illumination light with uniform brightness. In particular, when the light intensity distribution of the light beam is not completely random but has a consistent tendency, as is the case with a light beam emitted from a light source consisting of a light source lamp and a reflector such as a parabolic surface, the use of the first optical element can achieve extremely uniform light intensity distribution and angular distribution of the illumination light in the illuminated area.

The second optical element splits the intermediate beam into a P-polarized beam and an S-polarized beam, aligns the polarization direction of one beam with the polarization direction of the other, and ultimately superimposes and combines them onto a single illuminated area. Conventional projection display devices can only use either the P-polarized beam or the S-polarized beam, resulting in significant light loss. However, the second optical element of the present invention makes it possible to use both polarized beams without waste, resulting in a brighter image. Furthermore, because the split multiple intermediate beams are ultimately superimposed and combined onto a single illuminated area, a polarized beam with uniform brightness can be obtained as illumination light even if the beam emitted from the light source has a non-uniform light intensity distribution within the cross section of the beam. In particular, even when the intermediate light beam cannot be separated into P-polarized and S-polarized light beams with uniform light intensity or spectral characteristics, or when the light intensity or spectral characteristics of one of the polarized light beams changes during the process of aligning the polarization directions of the two polarized light beams, a polarized light beam with uniform brightness and little color unevenness can be obtained as illumination light.

The polarization conversion element of the second optical element can be a plate-shaped polarization conversion element consisting of a polarization separation unit array in which a plurality of polarization separation units, each having a pair of polarization separation surfaces and a reflection surface, are arranged, and a selective retardation plate on which λ/2 retardation layers are regularly formed. By employing such a polarization conversion element, polarization conversion can be performed in a small space without widening the light beam emitted from the light source.

In the first projection display device of the present invention equipped with the second optical element having the above-described configuration, the superposition-combining element is positioned away from the polarization conversion element, thereby shortening the distance between the first optical element and the polarization conversion element and enabling the use of a first optical element consisting of a beam-splitting lens with high light-gathering power. As a result, the size of the image formed by each beam-splitting lens can be reduced, and each intermediate beam can be incident only on its corresponding polarization splitting surface, preventing the beam from directly striking a reflecting surface. This improves light utilization efficiency and enables the production of brighter projected images.

In this case, if the superimposing/coupling element is attached to the light incident surface of the polarized light beam selecting element, it is possible to prevent light loss that occurs at the interface between the superimposing/coupling element and the reflection/transmission element, and further increase the light utilization efficiency.

Furthermore, in the first projection display device of the present invention, a polarizing plate may be disposed on the optical path between the superposition-combining element and the polarized beam selection element, or on the optical path between the polarized beam selection element and the projection optical system. Placing a polarizing plate in the former position can increase the polarization of the polarized beam incident on the polarized beam selection element, and ultimately the illumination light illuminating the reflective modulation element. Placing a polarizing plate in the latter position can increase the polarization of the polarized beam exiting the polarized beam selection element, and ultimately the image projected onto the display surface or projection surface via the projection optical system. Therefore, by disposing a polarizing plate in this manner, the contrast of the projected image can be increased, making it possible to obtain an extremely high-quality projected image.

A second projection display device of the present invention is a projection display device comprising a light source, a first optical element that condenses a light beam from the light source and splits it into a plurality of intermediate light beams, a second optical element disposed on the light exit surface side of the first optical element, and a color light splitting/combining element that splits the light beam emitted from the second optical element into three color lights and combines the color lights modulated by three reflective modulation elements that modulate the three color lights, respectively. The second optical element splits each of the intermediate light beams into a P-polarized light beam and an S-polarized light beam, and combines any one of the P-polarized light beam and the S-polarized light beam. a polarization conversion element that aligns the polarization direction of one of the polarized light beams with the polarization direction of the other polarized light beam and outputs the intermediate light beam; and a superposition/combination element that is arranged on the light output surface side of the polarization conversion element and superposes and combines each of the intermediate light beams onto the reflective modulation element; and a polarized light beam selection element is provided on the optical path between the second optical element and the color light separation/combination element, which reflects or transmits the light output from the second optical element to reach the color light separation/combination element and transmits or reflects the light combined by the color light separation/combination element to reach the projection optical system.

In the second projection display device of the present invention, the functions of separating and combining light are achieved using the same means, eliminating the need for dichroic mirrors 401 and 402 and reflecting mirrors 403, 404, and 405 as in the conventional projection display device described above. This allows the length of the optical path to be significantly shortened, minimizing light loss. This makes it possible to obtain extremely bright projected images without using a large-diameter projection lens.

The first optical element can be, for example, a lens array consisting of multiple beam-splitting lenses arranged in a matrix. By using such a lens array to split the light beam from the light source into multiple intermediate beams and then superimposing and combining these intermediate beams on the illuminated area, it is possible to reduce unevenness in illuminance compared to a single beam. Therefore, even if the light beam emitted from the light source has a non-uniform light intensity distribution within its cross section, it is possible to obtain illumination light with uniform brightness. In particular, when the light intensity distribution of the light beam is not completely random but has a consistent tendency, as is the case with a light beam emitted from a light source consisting of a light source lamp and a reflector such as a parabolic surface, the use of the first optical element can achieve extremely uniform light intensity distribution and angular distribution of the illumination light in the illuminated area.

The second optical element splits the intermediate beam into a P-polarized beam and an S-polarized beam, aligns the polarization direction of one beam with the polarization direction of the other, and finally superimposes and combines them on a single illuminated area. Conventional projection display devices can only use either the P-polarized beam or the S-polarized beam, resulting in significant light loss. However, the second optical element of the present invention makes it possible to use both polarized beams without waste, resulting in a brighter image. Furthermore, because the split multiple intermediate beams are finally superimposed and combined on a single illuminated area, a polarized beam with uniform brightness can be obtained as illumination light even if the beam emitted from the light source has a non-uniform light intensity distribution within the cross section of the beam. In particular, even when the intermediate light beam cannot be separated into P-polarized and S-polarized light beams with uniform light intensity or spectral characteristics, or when the light intensity or spectral characteristics of one of the polarized light beams changes during the process of aligning the polarization directions of the two polarized light beams, a polarized light beam with uniform brightness and little color unevenness can be obtained as illumination light.

The polarization conversion element of the second optical element can be a plate-shaped polarization conversion element consisting of a polarization separation unit array in which a plurality of polarization separation units, each having a pair of polarization separation surfaces and a reflection surface, are arranged, and a selective retardation plate on which λ/2 retardation layers are regularly formed. By employing such a polarization conversion element, polarization conversion can be performed in a small space without widening the light beam emitted from the light source.

In the second projection display device of the present invention equipped with the second optical element having the above-described configuration, the superposition-combining element is positioned away from the polarization conversion element, thereby shortening the distance between the first optical element and the polarization conversion element and enabling the use of a first optical element consisting of a beam-splitting lens with high light-gathering power. As a result, the size of the image formed by each beam-splitting lens can be reduced, and each intermediate beam can be incident only on its corresponding polarization splitting surface, preventing the beam from directly striking a reflecting surface. This improves light utilization efficiency and enables the production of brighter projected images.

In this case, if the superimposing/coupling element is attached to the light incident surface of the polarized light beam selecting element, it is possible to prevent light loss that occurs at the interface between the superimposing/coupling element and the reflection/transmission element, and further increase the light utilization efficiency.

Furthermore, in the second projection display device of the present invention equipped with the second optical element having the above-described configuration, if a reflecting mirror that changes the direction of light propagation by approximately 90 degrees is disposed between the light source and the polarized light beam selecting element, it is possible to make the optical system compact.

Furthermore, by using a dielectric mirror that selectively reflects only the specific polarized light beam obtained by the polarization conversion element and placing it between the polarization conversion element and the superposition coupling element, the degree of polarization of the polarized light beam incident on the polarization beam selection element, and ultimately the degree of polarization of the illumination light illuminating the reflective modulation element, can be increased. This increases the contrast of the projected image, making it possible to obtain extremely high-quality projected images.

Furthermore, the polarization conversion element of the second optical element can be a polarization conversion prism consisting of a triangular prism with a polarization separation film formed on its oblique surface and a plate-like prism with a reflective film formed on one surface, the polarization separation film and the reflective film being combined so that they are approximately parallel, and a selective retardation plate with a regularly-spaced λ/2 retardation layer. This polarization conversion element can also perform polarization conversion without widening the light beam emitted from the light source and in a small space. Furthermore, by employing this polarization conversion element, the light's direction of travel can be changed by approximately 90 degrees while performing polarization conversion, thereby enabling a compact optical system without the need for a reflecting mirror to change the light's direction of travel.

In the second projection display device of the present invention, the color separation/combination element may be configured as a dichroic prism having a dichroic film sandwiched between two prism components, and the polarized light beam selection element may be configured as a polarized beam splitter having a polarized light beam selection film sandwiched between two prism components, and one of the prism components constituting the dichroic prism and one of the prism components constituting the polarized beam splitter may be integrated.

Furthermore, in the second projection display device of the present invention, the color light separation/combining element may include first and second dichroic prisms each having a dichroic film sandwiched between two prism components, and one of the prism components constituting the first dichroic prism and one of the prism components constituting the second dichroic prism may be integrated.

Furthermore, the color light separation/combination element may further include a light-guiding prism, and one of the prism components constituting the first or second dichroic prism may be integrated with the light-guiding prism.

By integrating the prism components in this way, light loss at the boundaries between the prism components can be prevented, resulting in even greater light utilization efficiency and a brighter projected image.

In the second projection display device of the present invention, the color light separation/combination element may be configured as a cross dichroic prism having four prism components with dichroic films arranged in an X-shape, and the three reflective modulation elements may be arranged along three adjacent sides of the cross dichroic prism.

With this configuration, the separation and combination of color light can be performed using a single cross dichroic prism. Therefore, even when three reflective modulation elements are used, the optical path length is not increased, and light loss can be prevented. Therefore, even when three reflective modulation elements are used, there is no unevenness in brightness or color across the entire display or projection surface, and an extremely bright projected image can be obtained without the use of a large-diameter projection lens.

In a projection display device using this cross dichroic prism, the polarized light beam selection element may be configured as a polarized beam splitter having a polarized light beam selection film sandwiched between two prism components, and one of the two prism components constituting the polarized beam splitter may be integrated with any one of the four prism components constituting the cross dichroic prism.

By integrating the prism components in this way, it is possible to prevent light loss at the interface between the cross dichroic prism and the polarizing beam splitter, thereby further improving light utilization efficiency and enabling the production of brighter projected images.

In the second projection display device of the present invention, the color light separation/combining element may be configured as a dichroic prism having two dichroic films that separate and combine three color lights, respectively, arranged at different angles relative to the optical axis.

When using the cross dichroic prism mentioned above, there is a portion in the center of the prism where the dichroic films intersect at right angles, which can appear as a shadow in the projected image. This phenomenon can be prevented by using a dichroic prism in which the two dichroic films are positioned at different angles relative to the optical axis.

Furthermore, in the second projection display device of the present invention, a polarizing plate may be disposed on the optical path between the superposition-combining element and the polarized beam selection element, or on the optical path between the polarized beam selection element and the projection optical system. Placing a polarizing plate in the former position can increase the degree of polarization of the polarized beam incident on the polarized beam selection element, and thus the degree of polarization of the illumination light illuminating the reflective modulation element. Placing a polarizing plate in the latter position can increase the degree of polarization of the polarized beam exiting the polarized beam selection element, and thus the degree of polarization of the image projected onto the display surface or projection surface via the projection optical system. Therefore, by arranging a polarizing plate in this manner, the contrast of the projected image can be increased, making it possible to obtain extremely high-quality projected images.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram showing the main components of a projection display device 1 according to a first embodiment.

FIG. 2 is a perspective view showing the configuration of the first optical element 120 in the polarized illumination device 100.

FIG. 3 is a diagram illustrating the function of the second optical element 130 in the polarized illumination device 100.

FIG. 4(A) is a perspective view showing the configuration of the polarization separation unit array 141 in the polarized illumination device 100, and FIG. 4(B) is a perspective view showing the configuration of the selective retardation plate 147 in the polarized illumination device 100.

FIG. 5 is a schematic cross-sectional view showing an example of a reflective liquid crystal device.

FIG. 6 is a schematic diagram showing the main components of a projection display device 2 according to the second embodiment.

FIG. 7 is a schematic diagram showing the main components of a projection display device 3 according to the third embodiment.

FIG. 8 is a schematic diagram showing the main components of a projection display device 4 according to the fourth embodiment.

FIG. 9 is a schematic diagram showing the main components of a projection display device 5 according to the fifth embodiment.

FIG. 10 is a diagram comparing polarized illumination device 100A with polarized illumination device 100.

FIG. 11 is a schematic diagram showing the main components of a projection display device 6 according to the sixth embodiment.

Figure 12(A) is a perspective view showing the configuration of the polarization separation prism 820 in the polarized illumination device 100B, Figure 12(B) is a perspective view showing the configuration of a triangular prism 821 of the polarization separation prism 820, whose base is a right-angled isosceles triangle, and Figure 12(C) is a perspective view showing the configuration of a plate-shaped prism 823 of the polarization separation prism 820.

FIG. 13 is a perspective view showing the configuration of the exit lens 840 in the polarized illumination device 100B.

FIG. 14 is a schematic diagram showing the main components of a conventional projection display device.

BEST MODE FOR CARRYING OUT THE INVENTION The best mode (embodiment) for carrying out the present invention will be described below with reference to the drawings. In each of the following embodiments, the three mutually orthogonal directions are conveniently referred to as the X, Y, and Z directions, with the Z direction being the light propagation direction.

(First Embodiment) Figure 1 is a schematic plan view of the main components of a projection display device 1 according to a first embodiment. Note that Figure 1 is a cross-sectional view in the XZ plane passing through the center of a first optical element 120, which will be described in detail later.

The projection display device 1 of this example is broadly composed of a light source unit 110 arranged along a system optical axis L, a polarized illumination device 100 roughly composed of a first optical element 120 and a second optical element 130, a polarized beam splitter 200 equipped with an S-polarized light beam reflecting film 201 that reflects light from the polarized illumination device 100 to a reflective liquid crystal device 300 and transmits light modulated by the reflective liquid crystal device 300 to a projection optical system 500, a reflective liquid crystal device 300 that modulates the light emitted from the polarized beam splitter 200, and a projection optical system 500 that projects the light modulated by the reflective liquid crystal device 300 onto a projection surface 600.

The light source unit 110 is generally composed of a light source lamp 111 and a parabolic reflector 112. Light emitted from the light source lamp 111 is reflected in one direction by the parabolic reflector 112, becoming a substantially parallel beam of light that enters the first optical element 120. Here, the light source lamp 111 may be a metal halide lamp, a xenon lamp, a high-pressure mercury lamp, a halogen lamp, or the like, and the reflector may be an elliptical reflector, a spherical reflector, or the like, in addition to the parabolic reflector 112 mentioned in this example.

The first optical element 120, as shown in FIG. 2, is a lens array comprising a plurality of rectangular beam-splitting lenses 121 arranged in a matrix. The positional relationship between the light source unit 110 and the first optical element 120 is set so that the light source optical axis R is centered on the first optical element 120. Light incident on the first optical element 120 is split into a plurality of intermediate beams 122 by the beam-splitting lenses 121. At the same time, the beam-splitting lenses 121 focus the intermediate beams to form a number of focused images 123 equal to the number of beam-splitting lenses at positions where the intermediate beams converge within a plane perpendicular to the system optical axis L (the XY plane in FIG. 1). It is preferable to design the cross-sectional shape of the beam-splitting lenses 121 in the XY plane to be approximately similar to the shape of the display area (illuminated area) of the reflective LCD device 300. In this example, the illuminated area is assumed to be a rectangle whose long sides are in the X direction on the XY plane, so the cross-sectional shape of the beam splitter lens 121 on the XY plane is also a rectangle whose long sides are in the X direction.

Next, the function of the second optical element 130 will be described with reference to FIG.

The second optical element 130 is a composite roughly composed of a condenser lens array 131, a plate-shaped polarization conversion element 140 consisting of a polarization separation unit array 141 and a selective retardation plate 147, and an exit lens 150 that superimposes the intermediate light beams emitted from the polarization conversion element 140 onto a predetermined illuminated area 160. The second optical element 130 is disposed on the light exit surface side of the first optical element so as to be approximately perpendicular to the system optical axis L. This second optical element 130 has the function of separating each intermediate light beam 122 into a P-polarized light beam and an S-polarized light beam, aligning the polarization direction of one polarized light beam with the polarization direction of the other polarized light beam, and guiding each light beam with approximately aligned polarization directions to a single illuminated area 160.

Similar to the first optical element 120, the condenser lens array 131 comprises a plurality of condenser lenses 132 arranged in a matrix, the same number as the beam splitting lenses 121 constituting the first optical element 120. The condenser lens array 131 has the function of focusing and directing each of the intermediate beams 122 to a specific location on the polarization separation unit array 141, and aligning the optical axis of the intermediate beams 122 parallel to the system optical axis L. Therefore, it is desirable to optimize the lens characteristics of each condenser lens to match the characteristics of the intermediate beams 122 split by the first optical element 120 and to ensure that the inclination of the chief ray of light incident on the polarization separation unit array 141 is parallel to the system optical axis L. However, in consideration of reducing the cost and easing the design of the optical system, it is also possible to use a lens array identical to that of the first optical element 120, or to use a lens array composed of condenser lenses whose cross-sectional shape in the XY plane is approximately similar to that of the beam splitter lens 121 that constitutes the first optical element 120. In this example, the same lens array as that of the first optical element 120 is used as the condenser lens array 131. Note that if the beams incident on the first optical element 120 are highly parallel, the condenser lens array 131 may be omitted from the second optical element.

As shown in FIG. 4(A), the polarization separation unit array 141 is composed of multiple polarization separation units 142 arranged in the X direction. Each polarization separation unit 142 is a rectangular prism-shaped structure that includes a pair of polarization separation surfaces 143 and a reflecting surface 144 within a prism made of optical glass or the like, and functions to separate each of the incident intermediate light beams 122 into a P-polarized light beam and an S-polarized light beam. Note that the polarization separation unit array 141 need only be a structure that has alternatingly arranged polarization separation surfaces 143 and reflecting surfaces 144 therein, and does not necessarily need to be composed of multiple polarization separation units 142. The concept of the polarization separation unit 142 has been introduced merely to facilitate understanding of the function of the polarization separation unit array.

The polarization separation surfaces 143 and the reflection surfaces 144 are arranged alternately in the X direction, and are each tilted at approximately 45 degrees with respect to the system optical axis L. The polarization separation surfaces 143 and the reflection surfaces 144 are arranged so that they do not overlap each other. The area of the polarization separation surface 143 projected onto the XY plane is equal to the area of the reflection surface 144 projected onto the XY plane. The polarization separation surface 143 can be formed of a dielectric multilayer film or the like, and the reflection surface 144 can be formed of a dielectric multilayer film, an aluminum film, or the like.

Light incident on polarization separation unit 142 is separated into a P-polarized light beam that passes through polarization separation surface 143 and an S-polarized light beam that is reflected by polarization separation surface 143 and changes direction toward reflecting surface 144. The P-polarized light beam exits from P-polarized light beam exit surface 145 of polarization separation unit 142. Meanwhile, the S-polarized light beam is reflected by reflecting surface 144, becomes approximately parallel to the P-polarized light beam, and exits from S-polarized light beam exit surface 146 of polarization separation unit 142. In other words, intermediate light beam 122, which has a random polarization direction and enters polarization separation unit 142, is separated by polarization separation unit 142 into a P-polarized light beam and an S-polarized light beam, which exit in approximately the same direction from P-polarized light beam exit surface 145 and S-polarized light beam exit surface 146 of polarization separation unit 142, respectively.

In the polarized lighting device 100 of this example, it is necessary to guide each intermediate light beam 122 onto the polarization separation surface 143 of the polarization separation unit 142. Therefore, in this example, the condenser lens array 131 is positioned with a shift in the X direction relative to the polarization separation unit array 141 by a distance D equivalent to 1/4 of the width W of the polarization separation unit 142 so that the intermediate light beam 123 is focused at the center of the polarization separation surface 143. As a result, the light source unit 110 is also positioned so that its light source optical axis R is shifted parallel to the system optical axis L by the distance D in the X direction (see Figure 3).

A selective retardation plate 147 having λ/2 retardation layers 148 regularly formed thereon is disposed on the light exit surface side of the polarization separation unit array 141. An example of the selective retardation plate 147 is shown in FIG. 4(B).

The selective retardation plate 147 is an optical element in which a λ/2 retardation layer 148 is formed only on the P-polarized light beam exit surface 145 of the polarization separation unit 142, but not on the S-polarized light beam exit surface 146. Therefore, the P-polarized light beam exiting the polarization separation unit 142 is rotated in polarization direction by the λ/2 retardation layer 148 as it passes through the selective retardation plate 147, and is converted into an S-polarized light beam. On the other hand, because a λ/2 retardation layer 148 is not formed on the S-polarized light beam exit surface 146, the S-polarized light beam exiting the S-polarized light beam from the polarization separation unit 142 passes through the selective retardation plate 147 as S-polarized light.

That is, the intermediate light beams having random polarization directions emitted from the first optical element are separated into P-polarized light beams and S-polarized light beams by the polarization separation unit array 141, and then converted by the selective phase difference plate 147 into a single type of polarized light beam (in this example, an S-polarized light beam) with a uniform polarization direction.

The exit lens 150 (Figure 3), located on the light exit surface side of the polarization conversion element 140, functions as a superposition/combining element that superimposes and combines the intermediate beams, which have been aligned into S-polarized beams by the polarization conversion element 140, on the illuminated area 160. That is, each of the intermediate beams 122 split by the first optical element 120 (i.e., the image planes cut out by the beam splitting lens 121) is converted by the polarization conversion element 140 into a single type of polarized light with a uniform polarization direction, and then superimposed and combined on a single illuminated area 160 by the exit lens 150. In this case, even if the light intensity distribution of the beam incident on the first optical element 120 is not uniform across its incident cross section, the light intensity is averaged during the superposition/combination process of the multiple split intermediate beams, resulting in a nearly uniform light intensity distribution of the illumination light on the illuminated area. Therefore, the illuminated area 160 can be illuminated nearly uniformly with a single type of polarized beam. The exit lens 150 does not have to be a single lens body, but may be a lens array composed of multiple lenses, like the first optical element 120.

In summary, the polarized illumination device 100 can provide illumination light with uniform brightness and a nearly uniform polarization direction.

In the polarized illumination device 100, the first optical element 120 forms multiple tiny condensed light images 123, and the light-free space created during the formation process is effectively utilized to locate the reflective surface 144 of the polarization separation unit 142 in that space. This minimizes the broadening of the light beam that occurs when the light beam emitted from the light source is separated into two types of polarized light beam, enabling polarization conversion in a small space.

In addition, the cross-sectional shape of the beam splitting lens 121 constituting the first optical element 120 is rectangular in the X direction to match the shape of the illuminated area 160, which is rectangular in the X direction, and the two types of polarized beams emitted from the polarization separation unit array 141 are arranged alternately in the X direction. Therefore, even when illuminating the rectangular illuminated area 160, light utilization efficiency can be improved without wasting any light.

Furthermore, by optically integrating the focusing lens array 131, polarization separation unit array 141, selective retardation plate 147, and output lens 150 that constitute the second optical element 130, optical loss occurring at their interfaces is reduced, thereby further increasing the light utilization efficiency. However, these optical elements do not necessarily need to be optically integrated.

Returning to FIG. 1, the explanation will be given.

The polarizing beam splitter 200 has an S-polarized light beam reflecting film 201 formed on the interface between two prism components 202 and 203. The S-polarized light beam reflecting film 201 is composed of a dielectric multilayer film or the like and functions as a polarized light beam selection element that reflects S-polarized light beams and transmits P-polarized light beams. As described above, most of the light beams emitted from the polarized lighting device 100 are converted into one type of polarized light beam. Therefore, almost all of the light beams emitted from the polarized lighting device 100 are reflected or transmitted by the S-polarized light beam reflecting film 201. In this example, the light beams emitted from the second optical element 130 are S-polarized light beams. Therefore, most of the light beams incident on the polarizing beam splitter 200 are reflected by the S-polarized light beam reflecting film 201 and reach the reflective liquid crystal device 300.

If the light beam emitted from the second optical element 130 is a P-polarized light beam, the light beam incident on the polarizing beam splitter 200 will be transmitted through the S-polarized light beam reflecting film 201. Therefore, in this case, the reflective liquid crystal device 300 may be disposed so as to face the second optical element across the polarizing beam splitter 200.

The light beam incident on the reflective liquid crystal device 300 is modulated by the reflective liquid crystal device 300 based on predetermined image information.

An example of a reflective liquid crystal device 300 is shown in Figure 5. The reflective liquid crystal device 300 is an active matrix liquid crystal device in which switching elements consisting of thin film transistors are connected to reflective pixel electrodes 319 arranged in a matrix. The device has a structure in which a liquid crystal layer 320 is sandwiched between a pair of substrates 310 and 330. The substrate 310 is made of silicon, and a source electrode 311 and a drain electrode 316 are formed on a portion of the substrate 310. Also formed on the substrate 310 are a source electrode 312 and a drain electrode 317 made of aluminum, a channel 313 made of silicon dioxide, a gate electrode made of a silicon layer 314 and a tantalum layer 315, an interlayer insulating film 318, and a reflective pixel electrode 319 made of aluminum. The drain electrode 317 and the reflective pixel electrode 319 are electrically connected via a contact hole H. Because the reflective pixel electrode 319 is opaque, it can be stacked on top of the gate electrode, source electrode 312, and drain electrode 317 via the interlayer insulating film 318. Therefore, the distance X between adjacent reflective pixel electrodes 319 can be made considerably small, and the aperture ratio can be made large.

In this example, a storage capacitor is provided, which is composed of a drain 316, a silicon dioxide layer 340, a silicon layer 341, and a tantalum layer 342.

On the other hand, the opposing substrate 330 has an opposing electrode 331 made of ITO formed on the surface facing the liquid crystal layer 320, and an anti-reflection layer 332 formed on the other surface.

The liquid crystal layer 320 is driven by applying a voltage between the counter electrode 331 and each pixel electrode 319.

The liquid crystal layer 320 is of the super homeotropic type, in which the liquid crystal molecules 321 are vertically aligned when no voltage is applied (OFF), and are twisted 90 degrees when a voltage is applied (ON). Therefore, as shown in Figure 5, when no voltage is applied (OFF), the S-polarized light beam incident on the reflective liquid crystal device 300 from the polarizing beam splitter 200 is returned from the reflective liquid crystal device 300 to the polarizing beam splitter 200 without changing its polarization direction. Therefore, the S-polarized light beam is reflected by the S-polarized light beam reflecting film 201 and does not reach the projection optical system 500. On the other hand, when voltage is applied (ON), the S-polarized light beam incident on the reflective liquid crystal device 300 from the polarizing beam splitter 200 has its polarization direction changed by the twisting of the liquid crystal molecules 321, becoming a P-polarized light beam. After passing through the S-polarized light beam reflecting film 201, the P-polarized light beam is projected onto the projection surface 600 via the projection optical system 500.

As described above, the projection display device 1 of this embodiment has an extremely short optical path.

Furthermore, the aperture ratio of the liquid crystal device can be increased, minimizing light loss, making it possible to obtain extremely bright projected images without using a large-diameter projection lens.

Furthermore, by using the first and second optical elements, a polarized light beam with uniform brightness can be obtained as illumination light. This makes it possible to obtain an extremely bright projected image without uneven brightness or color across the entire display or projection surface.

The structure of the reflective liquid crystal device 300, the materials of its components, and the operating mode of the liquid crystal layer 320 are not limited to the above examples.

Furthermore, although the above-described reflective liquid crystal device 300 is designed for monochrome image display, it is also possible to display color images by providing a color filter between the reflective liquid crystal device 300 and the polarizing beam splitter 200 or within the reflective liquid crystal device 300.

(Second Embodiment) Figure 6 is a schematic plan view of the main components of a projection display device 2 of a second embodiment. Note that Figure 2 is a cross-sectional view taken along the XZ plane passing through the center of the first optical element 120. In the projection display device 2 of this embodiment, components that are similar to those of the projection display device 1 of the first embodiment described above are assigned the same reference numerals as those used in Figures 1 through 5, and detailed descriptions of these components will be omitted.

The projection display device 2 of this example includes a light source unit 110 arranged along a system optical axis L, a polarized illumination device 100 roughly composed of a first optical element 120 and a second optical element 130, a polarized beam splitter 200 equipped with an S-polarized light beam reflecting film 201 that reflects light from the polarized illumination device 100 to a color light separation/combination element composed of dichroic prisms 411, 413 and a light-guiding prism 412, and transmits the light combined by the color light separation/combination element to the projection optical system 500, and a polarized beam splitter The projection optical system 500 is generally composed of a color light separation/combination element (dichroic prisms 411, 413 and light guide prism 412) that separates the light emitted from the three reflective liquid crystal devices 300R, 300G, and 300B into red light (R), green light (G), and blue light (B) and combines the colored light modulated by the reflective liquid crystal devices 300R, 300G, and 300B; reflective liquid crystal devices 300R, 300G, and 300B that modulate the three colored light beams; and a projection optical system 500 that projects the light modulated by the three reflective liquid crystal devices 300R, 300G, and 300B onto a projection surface 600.

The projection display device 2 of this example uses a polarized lighting device 100 with exactly the same configuration as in the first example. As described in the first example, in the polarized lighting device 100, a randomly polarized light beam emitted from the light source unit 110 is split into multiple intermediate light beams by the first optical element 120, and then converted into a single type of polarized light beam (S-polarized light beam in this example) with a substantially uniform polarization direction by the second optical element 130. The S-polarized light beam emitted from the polarized lighting device 100 is then reflected by the S-polarized light beam reflecting film 201 of the polarizing beam splitter 200.

The light beam reflected by the S-polarized light beam reflecting film 201 is separated into three colored lights, red light (R), green light (G), and blue light (B), by two dichroic prisms 411 and 412.

The dichroic prism 411 has a blue-light-reflecting dichroic film 418, made of a dielectric multilayer film or the like, formed on the interface between two prism components 414, 414. Of the S-polarized light reflected by the S-polarized light reflecting film 201, blue light (B) is reflected by the blue-light-reflecting dichroic film 418 and enters the reflective liquid crystal device 300B via the light-guiding prism 412. The reflective liquid crystal device 300B then modulates the blue light (B) based on predetermined image information. The light-guiding prism 412 is used to equalize the optical path length of the blue light (B) with the optical path lengths of the other colored lights.

The dichroic prism 413 has a red-reflecting dichroic film 419 made of a dielectric multilayer film or the like formed on the interface between the two prism components 416 and 417. Of the colored light transmitted through the blue-reflecting dichroic film 418 of the dichroic prism 411, red light (R) is reflected by the red-reflecting dichroic film 419 and enters the reflective liquid crystal device 300R, where it is modulated based on predetermined image information.

Furthermore, the green light (G) transmitted through the red-light-reflecting dichroic film of the dichroic prism 413 enters the reflective liquid crystal device 300G, where it is modulated based on predetermined image information.

In this way, the red, blue, and green color lights modulated by the reflective liquid crystal devices 300R, 300B, and 300G are combined again by the dichroic prisms 413 and 411, and projected onto the projection surface 600 via the projection optical system 500.

Like the projection display device 1 described above, the projection display device 2 of this example also has a large aperture ratio of the liquid crystal device, making it possible to minimize light loss, thereby enabling an extremely bright projected image to be obtained.

Furthermore, by using the first and second optical elements, a polarized light beam with uniform brightness can be obtained as illumination light. This makes it possible to obtain an extremely bright projected image without uneven brightness or color across the entire display or projection surface.

In the projection display device 2 of this example, the prism component 202 that constitutes the polarizing beam splitter 200 and the prism component 414 that constitutes the dichroic prism 411 can be configured as an integrated prism. Similarly, the prism components 415 and 416, and the prism component 414 and the light-guiding prism 412 can also be configured as an integrated prism. By configuring these prism components as an integrated component, light loss that occurs at the boundaries between the prism components can be prevented, further improving light utilization efficiency.

(Third Embodiment) In the projection display device 2 of the second embodiment described above, two dichroic prisms 411 and 413 are used as color light separation/combination elements, and a light-guiding prism 412 is provided in the blue light path to equalize the optical path lengths of the other color lights.

This color separation/combination element can also be constructed using a single cross dichroic prism. An example of such a projection display device is shown in Figure 7.

Figure 7 is a schematic plan view of the main components of the projection display device 3 of the third embodiment. Note that Figure 7 is a cross-sectional view taken along the XZ plane passing through the center of the first optical element 120. In the projection display device 3 of this embodiment, components that are the same as those in the projection display device 1 of the first embodiment described above are assigned the same reference numerals as those used in Figures 1 to 5, and detailed descriptions thereof will be omitted.

In place of the dichroic prisms 411 and 412 that constitute the color light separation/combining elements of the projection display device 2 described above, the projection display device 3 of this example uses a cross dichroic prism 420 in which red light-reflecting dichroic films 425 and 426 and blue light-reflecting dichroic films 427 and 428 are arranged in an X-shape between four prism components 421, 422, 423, and 424. By using this cross dichroic prism 420, the length of the optical path can be significantly shortened. Therefore, an extremely bright projected image can be obtained without using a large-diameter projection lens.

Furthermore, in the projection display device 3 of this example, the prism component 202 that constitutes the polarizing beam splitter 200 and the prism component 421 that constitutes the cross dichroic prism 420 can be constructed as an integrated prism. By constructing the prism components 202 and 421 as an integrated component, it is possible to prevent light loss that occurs at the boundary between the prism components 202 and 421, thereby further improving light utilization efficiency.

The projection display device 3 of this example also has the same effects as the projection display device 2.

(Fourth Embodiment) When using a cross dichroic prism 420 as a color light separation/combination element, as in the projection display device 3 of the third embodiment, there is a portion in the center of the prism where the dichroic films intersect at right angles, and this portion may appear as a shadow in the projected image. By using a dichroic prism 430, as shown in Figure 8, instead of the cross dichroic prism 420, this phenomenon can be completely prevented.

Figure 8 is a schematic plan view of the main components of the projection display device 4 of the fourth embodiment. Note that Figure 8 is a cross-sectional view in the XZ plane passing through the center of the first optical element 120. The projection display device 4 of this embodiment replaces the cross dichroic prism 420 of the projection display device 3 of the third embodiment with a dichroic prism 430 in which two dichroic films are arranged at different angles relative to the optical axis. The remaining configuration is the same as that of the fourth embodiment, so detailed description will be omitted.

Dichroic prism 430 is composed of three prism components 431, 432, and 433, each with a different shape; a green-light-reflecting dichroic film 434 formed on the interface between prism components 431 and 432; and a red-light-reflecting dichroic film 435 formed on the interface between prism components 432 and 433. Here, green-light-reflecting dichroic film 434 and red-light-reflecting dichroic film 436 are positioned at different angles relative to the optical axis. Therefore, unlike when a cross dichroic prism is used, shadows do not appear in the projected image where the dichroic films intersect, resulting in an extremely high-quality projected image.

The projection display device 4 of this embodiment also has the same effects as the projection display device 3 of the third embodiment.

(Fifth Embodiment) Figure 9 is a schematic plan view of the main components of a projection display device 5 of the fifth embodiment. Note that Figure 9 is a cross-sectional view in the XZ plane passing through the center of the first optical element 120. The projection display device 5 of this embodiment is a modification of the projection display device 3 of the third embodiment described above. Components similar to those of the projection display device 3 of the third embodiment described above are designated by the same reference numerals as those used in Figure 7, and detailed descriptions thereof will be omitted.

First, the projection display device 5 of this embodiment differs from the projection display device 3 of the third embodiment in the configuration of the polarized illumination device. The polarized illumination device 100A in the projection display device 5 of this embodiment differs from the polarized illumination device 100 described above in that the exit lens 150 is located away from the polarization conversion element 140 and a reflecting mirror 700 is provided between the polarization separation unit array 141 and the exit lens 150.

FIG. 10 compares polarized lighting device 100A with polarized lighting device 100. For ease of explanation, irrelevant portions have been omitted. Solid lines in the figure indicate the relative positions of the first optical element 120, condenser lens array 131, polarization conversion element 140, and output lens 150 in the projection display device 5 of this example. Dotted lines in the figure indicate a state in which the polarization conversion element 140 and output lens 150 are not separated, i.e., the first optical element 120 and output lens 150 in the polarized lighting device 100 described above. Note that 160 in the figure indicates the illuminated area illuminated by polarized lighting device 100 or 100A.

If the light beams emitted from the light source unit 110 are highly parallel and the beam splitter lens 121 constituting the first optical element 120 has extremely high precision, each intermediate beam 122 will be focused onto an extremely small area on the polarization splitter surface 143 of the polarization splitter unit 142, as shown in Figure 3 above. However, in reality, the light-emitting point of the light source lamp 111 has a finite size, and there is variation in the surface precision of the parabolic reflector 112 and the lens precision of the beam splitter lens 121. Therefore, the image formed on the polarization splitter surface 143 by each intermediate beam 122 will have a certain size. It is desirable for the size of this image to be smaller than the cross-sectional size of the opening of the polarization splitter surface 143. However, if this is not the case, some light will be generated and will directly enter the reflecting surface 144 adjacent to the polarization splitter surface 143 without passing through the polarization splitter surface 143. Light directly incident on the reflective surface of a certain polarization separation unit (hereinafter referred to as the "first polarization separation unit") is reflected by the reflective surface and enters an adjacent polarization separation unit (hereinafter referred to as the "second polarization separation unit"), where it is separated into two polarized beams by the polarization separation surface of the second polarization separation unit. However, the beam reflected by the reflective surface of the first polarization separation unit and entering the second polarization separation unit and the beam directly incident on the polarization separation surface of the second polarization separation unit enter the polarization separation surface of the second polarization separation unit in directions that differ by 90 degrees. Therefore, the beam emerging from the P-polarized beam exit surface of the second polarization separation unit is mixed with the S-polarized beam that entered from the first polarization separation unit and reflected by the polarization separation surface of the second polarization separation unit. Furthermore, the light beam emitted from the S-polarized light beam exit surface of the second polarization splitter unit is mixed with the P-polarized light beam that entered through the first polarization splitter unit and passed through the polarization splitter surface of the second polarization splitter unit. Thus, light directly incident on the reflective surface of one polarization splitter unit is polarized and split differently in the adjacent polarization splitter unit than the light beam that directly entered the polarization splitter surface. The resulting polarized light beam has a different polarization direction than the polarized light beam that should have been emitted from the P-polarized light beam exit surface or the S-polarized light beam exit surface, which reduces the degree of polarization of the light beam emitted from the polarized lighting device. Because only one type of polarized light is effective as illumination light for the reflective liquid crystal devices 300R, 300G, and 300B, a reduction in the degree of polarization of the light beam emitted from the polarized lighting device undesirably reduces light utilization efficiency and ultimately reduces the brightness of the projected image.

Therefore, in the polarized illumination device 100 described above, a condenser lens array 131 is provided in the second optical element 130, and the light emitted from the first optical element 120 is guided to the polarization separation surface by the condensing power of this condenser lens array 131, thereby minimizing the amount of light that directly strikes the reflecting surface.

On the other hand, in order to prevent the light beams from being directly incident on the reflecting surface 144, it is also effective to use a lens with a large light-gathering power to reduce the size of the image formed on the polarization separation surface 143 by each intermediate light beam 122.

As can be seen from Figure 10, by locating the exit lens 150 at a position away from the polarization conversion element 140, the distance between the first optical element 120 and the polarization separation unit array 141 can be reduced, making it possible to use a beam splitting lens 121 with a shorter focal length, i.e., a greater light-gathering power, than the beam splitting lens 121 in the polarized lighting device 100. Therefore, the size of the image formed on the polarization separation surface 143 by each intermediate beam 122 can be reduced, making it possible to prevent the beam from being directly incident on the reflecting surface 144.

Here, since the polarization separation performance of the polarization separation surface 143 changes depending on the angle of incidence of light, the light-gathering power of the beam splitting lens 121 cannot be increased excessively.

Therefore, when the parallelism of the light emitted from the light source unit 100 is not very high, it is preferable to not only locate the exit lens 150 at a position away from the polarization separation unit array 141, as in the projection display device 5 of this example, but also to use the condenser lens array 131 in combination.

Furthermore, by attaching the exit lens 150 to the light incident surface 204 of the polarizing beam splitter 200, as in the projection display device 5 of this example, it is possible to reduce light reflection at the interface between the exit lens 150 and the polarizing beam splitter 200, thereby further improving the light utilization efficiency.

Furthermore, in the polarized lighting device 100A of the projection display device 5 of this example, a reflecting mirror 700 that changes the direction of light propagation by approximately 90 degrees is provided between the polarization separation unit array 141 and the output lens 150. By providing such a reflecting mirror 700, the portion consisting of the polarized beam splitter 200 and the cross dichroic prism 420 can be arranged side by side with the polarized lighting device 100A, thereby making it possible to make the optical system more compact.

The reflecting mirror 700 can be constructed as a total reflection mirror. However, if the reflecting mirror 700 is constructed as a dielectric mirror that selectively reflects only a specific polarized light beam (S-polarized light beam in this example) obtained by the polarization conversion element consisting of the polarization separation unit array 141 and the selective retardation plate 147, the degree of polarization of the polarized light beam incident on the polarizing beam splitter 200, and therefore the degree of polarization of the illumination light illuminating the reflective liquid crystal devices 300R, 300G, and 300B, can be increased. This increases the contrast of the projected image, making it possible to obtain extremely high-quality projected images.

Furthermore, if the reflecting mirror 700 is given the function of reflecting only visible light and transmitting infrared and ultraviolet rays, it is possible to prevent the optical elements following the reflecting mirror 700 from being deteriorated by infrared and ultraviolet rays.

Furthermore, the location of the reflecting mirror 700 is not limited to the location shown in Figure 9, and it may be located anywhere between the light source unit 110 and the polarizing beam splitter 200. For example, as in the polarized lighting device 100 described above, if the condenser lens array 131, polarization separation unit array 141, selective retardation plate 147, and output lens 150 constituting the second optical element 130 are integrated, the reflecting mirror 700 can also be located between the output lens 150 and the polarizing beam splitter 200.

The polarized illumination device 100A of this embodiment can be substituted for the polarized illumination device 100 in the projection display devices 1 to 4 of the first to fourth embodiments described above.

Second, the projection display device 5 of this embodiment differs from the projection display device 3 of the third embodiment in that polarizers 210 and 211 are provided on the light entrance surface 204 and light exit surface 205 of the polarizing beam splitter 200, respectively. The polarizer 210 increases the polarization of the polarized light beam incident on the polarizing beam splitter 200, thereby ultimately increasing the polarization of the illumination light illuminating the reflective liquid crystal devices 300R, 300G, and 300B. The polarizer 211 also increases the polarization of the polarized light beam exiting the polarizing beam splitter 200, thereby ultimately increasing the polarization of the image projected onto the display surface or projection surface via the projection optical system 500. The provision of these polarizers 210 and 211 in the projection display device 5 of this embodiment increases the contrast of the projected image, enabling the production of extremely high-quality projected images.

Here, polarizing plates 210 and 211 do not necessarily need to be attached to the surface of polarizing beam splitter 200; they may be placed on the optical path between output lens 150 and polarizing beam splitter 200, or on the optical path between polarizing beam splitter 200 and projection optical system 500. However, by attaching polarizing plates 210 and 211 to the surface of polarizing beam splitter 200, it is possible to reduce light reflection at the interface between polarizing plates 210 and 211 and polarizing beam splitter 200, thereby improving light utilization efficiency.

In the projection display devices 1 to 4 of the first to fourth embodiments described above, the polarizing plates 210 and 211 may be arranged as in this example.

The projection display device 5 of this embodiment is identical to the projection display device 3 of the third embodiment except for the points mentioned above, and therefore has the same effects as the projection display device 3 of the third embodiment.

(Sixth Embodiment) Figure 11 is a schematic plan view of the main components of a projection display device 6 of the sixth embodiment. Note that Figure 11 is a cross-sectional view in the XZ plane passing through the center of the first optical element 800. The projection display device 6 of this embodiment is a modification of the projection display device 3 of the third embodiment described above. Components similar to those of the projection display device 3 of the third embodiment described above are designated by the same reference numerals as those used in Figure 7, and detailed descriptions thereof will be omitted.

First, the projection display device 6 of this embodiment differs from the projection display device 3 of the third embodiment described above in the configuration of the polarized illumination device.

The polarized illumination device 100B in the projection display device 6 of this example is generally composed of a light source unit 110, a first optical element 800, and a second optical element 850, which are arranged along the system optical axis L.

The first optical element 800 is a lens array consisting of multiple rectangular beam-splitting lenses 801 arranged in a matrix, similar to the first optical element 120 shown in FIG. 2. The light source unit 110 is disposed so that the optical axis of the light source 111 coincides with the center of the first optical element 120. Light emitted from the light source unit 110 and incident on the first optical element 800 is split by the beam-splitting lens 801 into multiple intermediate beams, which then enter the second optical element 850.

The characteristics of each beam splitting lens 801 are optimized depending on the thickness of the plate-shaped prism 823 of the polarization splitting prism 820, which will be described in detail later.

The second optical element 850, which is disposed on the light exit surface side of the first optical element 800, is a composite roughly composed of a polarization conversion element 810, which is composed of a polarization separation prism 820 and a selective retardation plate 830, and an exit-side lens 840, which superimposes the intermediate light beams exiting from the polarization conversion element 810 onto the illuminated areas of the reflective liquid crystal devices 300R, 300G, and 300B.

As shown in Figures 12(A) to (C), polarization separation prism 820 is a combination of a triangular prism 821 with a polarization separation film 822 formed on its slanted surface and a right-angled isosceles triangle-shaped base, and a plate-like prism 823 with a reflective film 824 formed on the surface not joined to triangular prism 821. Polarization separation film 822 and reflective film 824 are arranged approximately parallel to each other. Polarization separation film 822 can be formed of a dielectric multilayer film or the like, and reflective film 824 can be formed of a dielectric multilayer film, an aluminum film, or the like.

Light incident on the polarization separation prism 820 is separated into a P-polarized beam that passes through the polarization separation film 822 and an S-polarized beam that is reflected by the polarization separation film 822 and changes its direction of travel toward the selective phase difference plate 830. The P-polarized beam enters the plate-shaped prism 823 and is reflected by the reflection film 824, changing its direction of travel and becoming approximately parallel to the S-polarized beam. In other words, the intermediate beam having a random polarization direction that enters the polarization separation prism 820 is separated into an S-polarized beam and a P-polarized beam by the polarization separation film 822 of the polarization separation prism 820. The S-polarized beam then exits from the S-polarized beam exit surface 825, indicated by the upward-sloping diagonal line in Figure 12(A), and the P-polarized beam exits from the P-polarized beam exit surface 826, indicated by the downward-sloping diagonal line in Figure 12(A), in approximately the same direction.

Note that the X-direction widths of the S-polarized light beam exit surface 825 and the P-polarized light beam exit surface 826 in Figure 12(A) correspond to the Z-direction and X-direction thicknesses of the plate-like prism 822. In this example, the Z-direction and X-direction thicknesses of the plate-like prism 822 are approximately half the X-direction size of the beam splitter lens 801 (see Figure 2), which constitutes the first optical element. Therefore, the X-direction widths of the S-polarized light beam exit surface 825 and the P-polarized light beam exit surface 826 are also approximately half the pitch of the beam splitter lens 801.

As shown in Figure 11, a selective retardation plate 830 having a regularly-spaced λ/2 retardation layer 831 is provided on the light exit surface side of the polarization separation prism 820. The selective retardation plate 830 is an optical element in which the λ/2 retardation layer 831 is formed only on the P-polarized light beam exit surface 826 of the polarization separation prism, and the λ/2 retardation layer 831 is not formed on the S-polarized light beam exit surface 825. Therefore, as shown in Figure 11, the P-polarized light beam exiting the polarization separation prism 820 is rotated in polarization direction by the λ/2 retardation layer 831 as it passes through the selective retardation plate 830, and is converted into an S-polarized light beam. On the other hand, since the λ/2 retardation layer 831 is not formed on the S-polarized light beam exit surface 825, the S-polarized light beam emitted from the S-polarized light beam exit surface 825 of the polarization separation prism 820 passes through the selective retardation plate 830 while remaining S-polarized.

That is, the intermediate light beam having random polarization directions emitted from the first optical element 800 is separated into P-polarized light beam and S-polarized light beam by the polarization separation prism 820, and then converted by the selective phase difference plate 830 into a light beam of substantially one type of polarization (in this example, S-polarized light beam) with a uniform polarization direction.

The exit lens 840, located on the light exit surface side of the polarization conversion element 810, is a lens array consisting of multiple rectangular lenses 841 arranged in a matrix, as shown in Figure 13. In Figure 13, the intersections of the crosses indicate the lens optical axes.

As can be seen from this diagram, rectangular lens 841 is a decentered lens. Like output lens 150 in polarized illumination device 100, output lens 840 functions as a superposition/combination element that superposes and combines the intermediate light beams aligned by polarization conversion element 810 onto the illuminated area of reflective liquid crystal devices 300R, 300G, and 300B. That is, the intermediate light beams split by first optical element 800 (i.e., the image planes separated by beam splitting lens 801) are superposed and combined onto a single illuminated area by polarization conversion element 810. This allows the illuminated area of reflective liquid crystal devices 300R, 300G, and 300B to be illuminated almost uniformly with a single type of polarized light beam.

The arrangement pitch of the rectangular lenses 841 in the X direction is approximately the same as the width in the X direction of the S-polarized light beam exit surface 825 and the P-polarized light beam exit surface 826 of the polarization splitting prism 820. In this example, the arrangement pitch of the rectangular lenses 841 in the Y direction is approximately the same as the arrangement pitch in the Y direction of the light beam splitting lenses 801 of the first optical element.

However, the X-direction arrangement pitch of the rectangular lenses may be approximately the same as the sum of the X-direction width of the S-polarized light beam exit surface 825 and the X-direction width of the P-polarized light beam exit surface 826 of the polarization splitter prism 820. In this case, the same lens array as that of the first optical element 800 can be used as the exit lens 840. Alternatively, the X-direction arrangement pitch of the rectangular lenses may be smaller than the sum of the X-direction width of the S-polarized light beam exit surface 825 and the X-direction width of the P-polarized light beam exit surface 826 of the polarization splitter prism 820. Similarly, the Y-direction arrangement pitch of the rectangular lenses 841 can also be smaller than the Y-direction arrangement pitch of the beam splitter lens 801. This can be achieved by using a decentered lens as the beam splitter lens 801 constituting the first optical element 800. This reduces the cross-sectional area of the light beam incident on the polarizing beam splitter 200, which results in a smaller size of the polarizing beam splitter 200.

In summary, polarized illumination device 100B can produce illumination light with uniform brightness and a nearly uniform polarization direction, just like polarized illumination device 100.

In the polarized lighting device 100B, the first optical element 800 splits the light emitted from the light source unit 110 into multiple intermediate beams, and separates the intermediate beams into P-polarized and S-polarized beams within a cross-sectional area approximately equal to the cross-sectional area of each intermediate beam. Therefore, the beam emitted from the light source can be separated into two types of polarized beams with almost no beam widening, and polarization conversion can be performed in a small space.

The cross-sectional shape of the beam splitter lens 801 constituting the first optical element 800 is rectangular with its long sides in the X direction to match the shape of the display area of the reflective liquid crystal device 300, i.e., the illuminated area (a rectangular shape elongated in the X direction), and the two types of polarized beams emitted from the polarization splitter prism 820 are arranged alternately in the X direction. This makes it possible to increase the light utilization efficiency without wasting light, even when illuminating a rectangular illuminated area.

Furthermore, by optically integrating the polarization separation prism 820, selective retardation plate 830, and output lens 840, which constitute the first optical element and the second optical element, optical loss occurring at their interfaces is reduced, further increasing the light utilization efficiency. However, these optical elements do not necessarily need to be optically integrated.

By using the polarized illumination device 100B described above, the projection display device 6 of this example can obtain a light beam with uniform brightness as illumination light. Therefore, it is possible to obtain a very uniform and very bright projected image across the entire display or projection surface.

Furthermore, since the polarized illumination device 100B changes the direction of light propagation by approximately 90 degrees while performing polarization conversion, it is possible to make the optical system compact without using a reflecting mirror that changes the direction of light propagation, as in the projection display device 5 of the fifth embodiment described above.

In the projection display device 6 of this example, as in the projection display device 5 of the fifth embodiment described above, by placing polarizing plates to increase the degree of polarization on the light entrance surface and light exit surface of the polarizing beam splitter 200, the contrast of the projected image can be increased, making it possible to obtain a projected image of extremely high quality.

(Other) In the above-described embodiments, the polarized illumination device is configured to obtain an S-polarized light beam. However, it may also be configured to obtain a P-polarized light beam. In this case, the λ/2 retardation layer 148, 831 of the selective retardation plate 147, 830 may be formed on the polarization separation unit array 141 or the S-polarized light beam exit surface 146, 825 of the polarization separation prism 820.

Furthermore, projection display devices include a front type in which the projected image is observed from the projection surface 600 on the side of the projection optical system 500, and a rear type in which the projected image is observed from the side opposite the projection optical system 500, and the present invention is applicable to either type.

As described above, the projection display device of the present invention allows for a shorter optical path length compared to conventional projection display devices, making it possible to obtain bright projected images without using a large-diameter projection lens. Furthermore, it is possible to reduce unevenness in illuminance across the illuminated area, making it possible to obtain extremely bright, uniform projected images across the entire display or projection surface.

INDUSTRIAL APPLICABILITY The projection display device of the present invention can be used to project and display images, for example, output from a computer or a video recorder, onto a screen.

───────────────────────────────────────────────────── (Note) This publication is based on the publication published internationally by the International Bureau of Patents (WIPO). The effect of the international publication of the Japanese patent application (Japanese utility model registration application) related to this publication arises pursuant to Article 184-10, Paragraph 1 of the Patent Act (Article 48-13, Paragraph 2 of the Utility Model Act) and is unrelated to this publication.

Claims (21)

[Claims] 1. A projection display device comprising: a light source; a first optical element that collects a light beam from the light source and splits it into multiple intermediate light beams; a second optical element arranged on the light exit surface side of the first optical element; and a single reflective modulation element that modulates the light emitted from the second optical element, wherein the second optical element comprises: a polarization conversion element that separates each of the intermediate light beams into a P-polarized light beam and an S-polarized light beam and outputs the P-polarized or S-polarized light beam with the polarization direction of either the P-polarized or S-polarized light beam aligned with the polarization direction of the other polarized light beam; and a superposition/coupling element arranged on the light exit surface side of the polarization conversion element that superposes and combines each of the intermediate light beams onto the reflective modulation element; A projection display device characterized in that a polarized beam selection element is provided on the optical path between the second optical element and the reflective modulation element, which reflects or transmits light emitted from the second optical element to reach the reflective modulation element, and transmits or reflects light modulated by the reflective modulation element to reach the projection optical system. 2. A projection display device according to claim 1, characterized in that the polarization conversion element comprises a polarization separation unit array in which a plurality of polarization separation units, each having a pair of polarization separation surfaces and a reflection surface, are arranged, and a selective retardation plate in which λ/2 retardation layers are regularly formed. 3. The projection display device according to claim 2, wherein the superposition-combining element is provided at a position separate from the polarization conversion element. 4. A projection display device according to claim 3, wherein the superposition-coupling element is attached to the light incident surface of the polarized light beam selection element. 5. The projection display device according to claim 2, wherein a polarizing plate is provided on the optical path between the superposition-combining element and the polarized light beam selection element. 6. The projection display device according to claim 2, wherein a polarizing plate is provided on the optical path between the polarized light beam selecting element and the projection optical system. 7. A projection display device comprising: a light source; a first optical element that condenses a light beam from the light source and splits it into multiple intermediate light beams; a second optical element arranged on the light exit surface side of the first optical element; and a color light separation/combination element that separates the light beam emitted from the second optical element into three colored light beams and combines the colored light beams modulated by three reflective modulation elements that modulate the three colored light beams, respectively; wherein the second optical element comprises: a polarization conversion element that separates each of the intermediate light beams into a P-polarized light beam and an S-polarized light beam and outputs the P-polarized or S-polarized light beam with the polarization direction of either the P-polarized or S-polarized light beam aligned with the polarization direction of the other polarized light beam; and a superposition/combination element arranged on the light exit surface side of the polarization conversion element that superposes and combines each of the intermediate light beams onto the reflective modulation element; A projection display device is characterized in that a polarized light beam selection element is provided on the optical path between the second optical element and the color light separation/combining element, which reflects or transmits light emitted from the second optical element to reach the color light separation/combining element, and transmits or reflects light combined by the color light separation/combining element to reach the projection optical system. 8. A projection display device according to claim 7, characterized in that the polarization conversion element comprises a polarization separation unit array in which a plurality of polarization separation units, each having a pair of polarization separation surfaces and a reflection surface, are arranged, and a selective retardation plate in which λ/2 retardation layers are regularly formed. 9. The projection display device according to claim 8, wherein the superposition-combining element is provided at a position separate from the polarization conversion element. 10. A projection display device according to claim 9, wherein the superposition-combining element is attached to the light incident surface of the polarized light beam selection element. 11. The projection display device according to claim 8, characterized in that a reflecting mirror that changes the direction of light propagation by approximately 90 degrees is provided between the light source and the polarized light beam selection element. 12. A projection display device according to claim 11, wherein the reflecting mirror is a dielectric mirror that selectively reflects only the specific polarized light beam obtained by the polarization conversion element, and is disposed between the polarization conversion element and the superposition-coupling element. 13. A projection display device according to claim 7, characterized in that the polarization conversion element comprises a polarization separation prism formed by combining a triangular prism with a polarization separation film formed on its oblique surface and a plate-shaped prism with a reflective film formed on one surface, the polarization separation film and the reflective film being approximately parallel to each other, and a selective retardation plate on which λ/2 retardation layers are regularly formed. 14. A projection display device according to claim 8 or 13, wherein the color separation/combination element comprises a dichroic prism having a dichroic film sandwiched between two prism components, the polarized light beam selection element comprises a polarized beam splitter having a polarized light beam selection film sandwiched between two prism components, and one of the two prism components constituting the dichroic prism and one of the two prism components constituting the polarized beam splitter are integrated together. 15. A projection display device according to claim 8 or 13, wherein the color light separation/combination element includes first and second dichroic prisms with a dichroic film sandwiched between two prism components, and wherein one of the two prism components constituting the first dichroic prism and one of the two prism components constituting the second dichroic prism are integrated together. 16. A projection display device according to claim 15, wherein the color light separation/combination element further includes a light-guiding prism, and one of the prism components constituting the first or second dichroic prism is integrated with the light-guiding prism. 17. A projection display device according to claim 8 or 13, wherein the color light separation/combination element comprises a cross dichroic prism with dichroic films arranged in an X-shape between four prism components, and the three reflective modulation elements are arranged along three adjacent sides of the cross dichroic prism. 18. A projection display device according to claim 17, wherein the polarized light beam selection element comprises a polarized beam splitter having a polarized light beam selection film sandwiched between two prism components, and wherein one of the two prism components constituting the polarized beam splitter is integrated with any one of the four prism components constituting the cross dichroic prism. 19. A projection display device according to claim 8 or 13, characterized in that the color light separation/combining element comprises a dichroic prism in which two dichroic films that separate and combine three colors of light are arranged at different angles relative to the optical axis. 20. The projection display device according to claim 8 or 13, wherein a polarizing plate is provided on the optical path between the light source and the polarized light beam selection element. 21. The projection display device according to claim 8 or 13, wherein a polarizing plate is provided on the optical path between the polarized light beam selecting element and the projection optical system.