JPH1010467A - Projection and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection display device in which there is not irregularity in color and brightness, a uniform contrast ratio and high-quality display throughout the entire screen by the use of effectively arranging lenses. SOLUTION: An intermediate lens 8 is situated in the middle position of the optical path between an optical integrator 2 and reflection type liquid crystal panels 11, 12, 13 to convert the divergent light from the optical integrator 2 to parallel luminous flux. Parallel luminous flux passes a polarized light beam splitter 9 and a dichroic prism 10 and the principal rays of the luminous flux incident on each display surface of the reflective liquid crystal panels 11, 12, 13 are perpendicular to the surface of the liquid crystal panels. Reflection passes the dichroic prism 10 and the polarized light beam splitter 9 as a parallel light beam. A telecentric optical system is used for the projection lens 14. By this, since no irregularity in color and contrast due to the angular dependence of the dichroic prism 10 and the polarized light beam splitter 9 is generated, a bright, high-quality display uniform in image quality is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system of a projection display device using a reflection type liquid crystal panel.

[0002]

2. Description of the Related Art As a conventional illumination optical system of a projection display device, there is a method using an optical integrator disclosed in US Pat. No. 5,098,184. This optical system splits a non-uniform light beam from the light source into a plurality of rectangular parts using a lens plate included in the optical integrator, and superimposes the images on the liquid crystal panel to form a rectangular liquid crystal panel. It illuminates with uniform illuminance. FIG. 3 in the detailed description of this publicity
FIG. 3 shows an example in which an illumination system of an optical integrator is applied to an optical system of a projection display device using a reflective liquid crystal panel.

[0003]

However, in the conventional method, the image of the light source lamp is formed as a secondary light source on the light beam emitting portion of the optical integrator, and the divergent light from the secondary light source illuminates the liquid crystal panel. When a dichroic mirror for color separation is placed between the optical integrator and the liquid crystal panel, the liquid crystal panel is illuminated with a light beam with color unevenness due to the angle dependence of the dichroic mirror, which causes display quality to deteriorate. Had become. In particular, when a reflective liquid crystal panel is used, parts having a large angle dependence such as a polarizing beam splitter are required. Therefore, when divergent light from the optical integrator passes through, there is a problem that the display contrast ratio is deteriorated. Was. Moreover, in the disclosed example, there is a problem that the reflected light does not efficiently enter the projection lens because the light flux reflected by the reflective liquid crystal panel further diverges.

Therefore, a projection display apparatus according to the present invention solves such a problem. An object of the invention is to provide a projection display apparatus using a reflection type liquid crystal panel and an optical integrator in an illumination system. By arranging the lens effectively, over the entire screen,
An object of the present invention is to provide a projection display device having a high-quality display without color unevenness or brightness unevenness, and having a uniform contrast ratio.

[0005]

A projection display apparatus according to the present invention comprises a light source device, an optical integrator for converting light from a light source into a uniform light beam, and a reflection type liquid crystal for modulating a light beam from the optical integrator to display an image. A projection display device including a panel and a projection lens for enlarging and projecting an image displayed on the reflective liquid crystal panel onto a screen, wherein an optical path length between the optical integrator and the reflective liquid crystal panel is provided. A lens portion having a focal length of about one-half of the optical path length thereof is disposed at a substantially middle position of the optical liquid crystal panel so that principal rays of a light beam entering each portion of the reflective liquid crystal panel are parallel to each other. It is characterized by.

[0006]

First, the difference between the conventional optical integrator illumination system and the case of the present invention will be described. FIG. 1A shows a general optical integrator illumination system. The optical integrator 2 includes a first lens plate 3 on which a plurality of rectangular lenses are arranged in a plane, and a second lens plate 4 similarly formed of a plurality of rectangular lenses. Here, each lens plate has the same shape. The light beam from the light source 1 is a light beam that is substantially parallel but has uneven brightness, and the liquid crystal panel 7 is illuminated with uniform illuminance by the action of the optical integrator 2. A condensing lens 5 (hereinafter, referred to as a proximity lens) in a light beam emitting portion of the optical integrator 2 is for directing a light beam emitted from the optical integrator in parallel to a center portion of the liquid crystal panel, and a focal length f of the liquid crystal is Equal to the distance to panel 7. At this time, the liquid crystal panel 7 is illuminated with divergent light from a secondary light source formed on the second lens plate 4. Therefore, at points A and C in the peripheral portion of the liquid crystal panel, the principal ray of the incident light flux enters the liquid crystal panel 7 at an angle other than perpendicular as indicated by 43 and 45. However, the center B of the liquid crystal panel 7
At a point, it is a chief ray like 44 and perpendicular to the liquid crystal panel. In an ordinary liquid crystal projector, a dichroic mirror for separating white light source light into three colors of RGB is arranged between the liquid crystal panel 7 and the optical integrator 2, and the three liquid crystal panels modulate the respective color lights. Since the color separation means 6 using a dichroic mirror uses a dielectric multilayer film, it has an angle dependency that the color separation characteristic changes depending on the incident angle of the light beam. In such a case, the color of the luminous flux illuminated on the liquid crystal panel 7 differs depending on the portion, and color unevenness occurs on the liquid crystal panel 7 to deteriorate the display quality. On the other hand, FIG. 1B shows the case of the present invention.
In this case, the condensing lens 8 (hereinafter, referred to as an intermediate lens) is located at a position which is a half of an optical path length (a value obtained by dividing a physical distance by a refractive index of a medium) between the optical integrator 2 and the liquid crystal panel 7. And its focal length f is equal to the distance to the optical integrator 2 and to the liquid crystal panel 7. With this design, the principal rays 46, 47, and 48 of the luminous flux incident on each part of the liquid crystal panel 7
Are all perpendicular to the surface of the liquid crystal panel 7. Therefore, even if the color separation means 6 has an angle dependency, all the light beams enter at the same angle, so that color unevenness does not occur on the liquid crystal panel 7. The intermediate lens 8 may be composed of a plurality of lenses, or a Fresnel lens.

FIG. 2A shows a specific example in which this illumination system is applied to a projection display device using a reflection type liquid crystal panel. The intermediate lens 8 is arranged at an intermediate position of the optical path length between the optical integrator 2 and the liquid crystal panels 11, 12, 13. Here, the first lens plate 3 and the second lens plate 4 are composed of six rectangular lenses similar to the shape of the liquid crystal panel. The polarization beam splitter 9
A quadrangular prism including the dielectric multilayer film 19 that reflects s-polarized light transmits p-polarized light contained in incident light, reflects s-polarized light, and directs the light toward the liquid crystal panel. The reflected s-polarized light is color-separated by a dichroic prism 10 including a dichroic layer of a dielectric multilayer film in an X shape. For example, green light goes straight to illuminate the liquid crystal panel 12, and red light and blue light are reflected, and the liquid crystal panels 11 and 13 are respectively reflected.
To illuminate. The respective color lights modulated and reflected by the liquid crystal panel follow the same path in reverse and enter the polarization beam splitter 9 again, transmit only the p-polarized light component included in the reflected light, and transmit the transmitted light flux to the projection lens 14. Incident. The polarization beam splitter 9 also has a role of a polarizer for extracting polarized light from the light source light and a role of an analyzer for extracting only a modulation component from a light beam modulated by the liquid crystal panel. Since the polarization beam splitter 9 has an extremely large angle dependency, the parallelism of the passing light beam greatly affects the image quality. This is shown in FIG. First, when a conventional close lens is used (when a condenser lens is placed close to the optical integrator 2), the contrast ratio of the display screen increases from the center to the periphery of the liquid crystal panel. The contrast ratio decreases. On the other hand, when the intermediate lens 8 is used as in the present invention, the contrast ratio is constant at the highest value. Since this contrast ratio is almost determined by the parallelism of the light beam passing through the polarizing beam splitter 9, passing through the same parallel light in the case of a polarizer and in the case of an analyzer as in the present example does not affect image quality. The effect is very large. The same can be said for the color unevenness. In the case of a close-up lens, color unevenness occurs in the peripheral portion, and the two causes are the angle dependency of the dichroic prism and the angle dependency of the polarizing beam splitter 9. In the case of the intermediate lens, no color unevenness occurs.

The specific structure of the light source device used in the projection display device of the present invention is shown in FIG. 3 and FIG. FIG.
In (A), the radiated light from the light source lamp 15 is focused on the optical integrator 2 by the elliptical reflector 16. As the light source lamp 15, a metal halide lamp, a xenon lamp, a halogen lamp, or the like is used. The collimating lens 17 is for collimating the incident light beam,
Its focal length is equal to the distance to the front of the elliptical reflector. FIG. 3B shows a method for converting all the light emitted from the light source lamp 15 into polarized light and using it efficiently. The light emitted from the light source lamp 15 is collimated by the parabolic reflector 16. The polarization splitting prism 18 includes a dielectric multilayer film 19, which is the same as the polarization beam splitter, inside, and angularly separates s-polarized light and p-polarized light included in incident light. The s-polarized light is reflected by the dielectric multilayer film 19 that reflects polarized light, and the p-polarized light passes through the dielectric multilayer film and is reflected by the total reflection surface, but the reflection directions of the s-polarized light and the p-polarized light are slightly different. . Both polarized lights enter the condenser lens 20,
Light is collected toward the relay lens 22. Since the spot 32 of the s-polarized light and the spot 33 of the p-polarized light are formed at different positions at the position of the relay lens 22, the polarization direction of one polarized light is rotated by the half-wave plate 21, and the other polarized light is Convert in the same direction as. The relay lens 22 reduces and forms the image of the condenser lens 20 on the collimating lens 23. The light beam that has passed through the collimating lens 23 is collimated and enters the optical integrator 2. In each rectangular lens of the second lens plate 4, two light beam spots 34 corresponding to the s-polarized spot 32 and the p-polarized spot 33 are formed. Since the rectangular lens is generally horizontally long, the two light beam spots 34 fit well.

FIG. 4A shows another configuration for converting light from a light source into polarized light. Here, the light from the light source first enters the polarization beam splitter 24 and is separated into reflected s-polarized light and transmitted p-polarized light. The p-polarized light passes through the half-wave plate 21, is converted into s-polarized light, and is reflected by the mirror 25.
The respective polarized lights are incident on the condenser lenses 26 and 27, are directed to the collimating lens 28, and are superimposed on the collimating lens 28. The light beam that has passed through the collimating lens 28 enters the optical integrator 2, and two light beam spots 34 corresponding to the condenser lenses 26 and 27 are formed in each rectangular lens in the second lens plate 4. FIG. 4B also shows
This is another configuration that converts light from the light source into polarized light. The configuration of the polarization splitting prism 29 is basically the same as the case of FIG. 3B, except that the dielectric multilayer film 19 that reflects polarized light and the total reflection surface are located at some distance. The condenser lens 30 combines the polarized lights on the collimating lens 31. Parallelizing lens 31
Is a concave lens for collimating incident light. Two light beam spots 34 are formed in each rectangular lens in the second lens plate 4 of the optical integrator 2, and are respectively s-polarized light and p-polarized light. The half-wave plate 21 is the second lens plate 4
And the direction of one polarized light is aligned with the direction of the other polarized light.

FIG. 5 shows a specific example of the configuration of the projection display device of the present invention. In FIG. 5A, the light source device shown in FIG. 3B is used, and the display optical system shown in FIG. 2A is used. In the light source device, the optical path is bent by a mirror 35, and a mirror 36 is also arranged between the optical integrator and the intermediate lens 8, so that the entire device is reduced in size. Polarizing plates 38 and 39 are attached to the entrance and exit of the polarization beam splitter 9, respectively, and the contrast ratio is increased by compensating for the polarization detection characteristics of the polarization beam splitter 9. If the polarizing beam splitter 9 is made of a liquid such as ethylene glycol instead of a glass material, the contrast ratio can be further increased. FIG. 5B shows another specific example.
For the light source device, a modified configuration of that shown in FIG. 4A is used. Here, the light from the light source is divided into p-polarized light to be transmitted and s-polarized light by using two polarizing beam splitters 24, and the s-polarized light is totally reflected by the two triangular prisms 61 and then passes through the half-wave plate 21. Is converted to p-polarized light. All the light from the light source passes through the condenser lens 62 and is focused on the parallelizing lens 28. The display optical system is basically the same as the above examples, except that the p-polarized light transmitted through the polarizing beam splitter 9 is applied to the liquid crystal panel 11,
The polarization beam splitter 9 takes out s-polarized light from the reflected light that has entered the optical modulators 12 and 13 and that has been modulated. In this case, the depth t of the entire device can be made extremely thin, so that if it is used for a rear projection type display device, the depth of the entire display device can be made small.

FIG. 6A shows an example of the configuration of a projection display device according to the present invention. In this example, the intermediate lens 8 includes a polarizing beam splitter 9 and a dichroic prism 10.
Placed between. Since the focal length of the intermediate lens 8 is very short, it is constituted by two convex lenses. Since the light beam transmitted through the intermediate lens 8 enters the projection lens 40, it can be said that both the intermediate lens 8 and the projection lens 40 constitute a projection lens. With this configuration, the distance between the optical integrator 2 and the polarization beam splitter 9 can be reduced, and thus there is an advantage that the entire device is reduced in size. FIG. 6B shows another configuration. Here, an off-axis optical system is used without using the polarization beam splitter 9 of FIG. In the optical integrator 2, the space between the first lens plate 3 and the second lens plate 4 is folded back by the mirror 42, and the second lens plate 4 is placed at the focal position of the intermediate lens 8. Has been removed. At this time, the reflected lights from the liquid crystal panels 11, 12, and 13 are converged near the second lens plate 4, and the image of the light spot formed here is the same as the light spot formed on the second lens plate 4. They have the same shape and are symmetrical with respect to the optical axis of the condenser lens 8. When the liquid crystal panel modulates polarized light, the polarizing plate 49 is disposed near the focal position of the intermediate lens 8. The polarization direction of the polarizing plate on the side of the second lens plate 4 and the polarization direction of the polarizing plate on the side where the light flux goes to the projection lens 40 form an angle of 90 degrees. When the liquid crystal panel is of a system that scatters and modulates incident light (a system using PDLC liquid crystal), a projection diaphragm 41 is arranged, and a light beam that passes through a diaphragm opening that matches the shape of a light beam spot formed here. Only the light passes through the projection lens 40 and is projected on the screen. In this case, the polarizing plate 49 is unnecessary.
In this optical system, since the off-axis optical system is used, the luminous flux incident on the liquid crystal panels 11, 12, and 13 is slightly shifted from the direction perpendicular to the panel surface. However, since the direction of the principal ray of the light beam entering each part is the same, color unevenness does not occur. Although the optical integrator 2 and the projection stop 41 are drawn side by side in this figure, they may be arranged so as to be located on the back side and the near side on the paper.

FIG. 7A shows a method of converting all unpolarized light from a light source into polarized light. Light emitted from the light source lamp 15 is reflected by the reflector 16 and illuminates the collimating lens 50. As the reflector, in addition to the ellipse and paraboloid already described, there is a method using an inclined ellipse as disclosed in Japanese Patent Application Laid-Open No. Hei 5-323258. It is preferable to illuminate the inside. The parallelizing lens 50 is a convex lens,
Either a concave lens or an aspherical lens is used. When the light passes through the parallelizing lens 50, the light flux is parallel and has good uniformity. The non-polarized light emitted from the collimating lens 50 is then incident on the polarization splitting prism 51, reflected, and separated into two polarized lights having slightly different directions. This polarized light separating prism 51 is composed of two glass material prisms 52 and 53 and a polarized light reflecting surface 54 between them, and the polarized light reflecting surface 54 is composed of two polarized light beams included in non-polarized light and perpendicular to each other. One of them is reflected. Then, the other polarized light transmitted through the polarized light reflecting surface 54 is
Are totally reflected at the boundary surface with the air at the point, and pass through the polarization reflection surface 54 again. Since the polarization reflecting surface 54 and the total reflection surface have slightly different directions, the two polarized lights are separated. The polarization reflection surface 54 may be a dielectric multilayer film, but can be formed using a birefringent substance, for example, a liquid crystal. When a liquid crystal is used, the liquid crystal is homogeneously aligned between the two glass prisms 52 and 53 in a direction perpendicular to the direction vector of the polarization reflection surface 54. For example, the refractive index of the liquid crystal is 1.5 for ordinary light and 1.
When using a glass material having a refractive index of 7, a glass material having a refractive index of 1.7 is selected. At this time, the ordinary light included in the incident non-polarized light is totally reflected on the liquid crystal surface, and the extraordinary light is transmitted. Now, the two polarized lights separated in the direction pass through the first lens plate 3 of the optical integrator 2, and
Two light beam spots 34 of polarized light are formed in each rectangular lens of the lens plate 4. Since the two polarized lights are separated at the condensing position, if the half-wave plate 21 is disposed on this surface, two polarized lights perpendicular to each other can be converted into polarized lights in the same direction. The polarization separation prism 51 using liquid crystal described here may be used for the illumination system of FIGS. 3B and 4B described above. FIG. 7B illustrates a configuration of a projection display device using the light source device having this configuration. It can be made very compact.

FIG. 8 shows a configuration example of the projection display device of the present invention. The configuration shown in FIG. 8A is equivalent to the configuration shown in FIG.
Is replaced by two triangular prisms. In the triangular prism 50 on the side where the light source light is incident, all the light source light is directed to the liquid crystal panels 11, 12, and 13 by totally reflecting the incident light source light. And the luminous flux reflected from each liquid crystal panel is
Since the light is incident on the reflection surface that has been totally reflected earlier at an angle different from the first, that is, an angle smaller than the critical angle of total reflection, the light is transmitted through this surface. The transmitted light flux further passes through the triangular prism 51 and enters the projection lens 14. The triangular prism 51 is necessary to remove aberration caused by passing through the triangular prism 50 on the light source side. When the liquid crystal panel modulates polarized light, polarizing plates 38 and 39 are attached to the light source side of the triangular prism 50 and the projection lens 14 side of the triangular prism 51. In the case where the liquid crystal panel scatters and modulates an incident light beam (a method using a PDLC liquid crystal), a projection stop 41 is disposed inside the projection lens 14 and a secondary light source on the second lens plate 4 is provided. Only the luminous flux corresponding to the image is transmitted. At this time, the two polarizing plates 38 and 39 are unnecessary. FIG. 8B shows an example in which elements other than the projection lens 14 are linearly arranged. Here, the light from the light source is divided into two triangular prisms 50 and 5.
1 and then enter the liquid crystal panels 11, 12, and 13. The luminous flux modulated by the liquid crystal panel is applied to a triangular prism 5.
Since the light is totally reflected at 0 and then enters the projection lens 14,
No aberration occurs in the projected image. In addition, if the dichroic prism 10 is arranged in the direction as shown in this figure, the display is not affected by the angular dependence of the color separation characteristics of the dichroic prism 10, so that a higher-quality image display can be performed.

Heretofore, a dichroic prism including a dielectric multilayer film in an X-shape has been used as the color separation / combination means in the projection display apparatus of the present invention, but can be replaced with another configuration. In FIG. 9A, it is composed of two color separation prisms 52 and 53 and one triangular prism 54. Each of the color separation prisms includes a dichroic layer of a dielectric multilayer film at an angle of 45 degrees inside. In principle, the above-described dichroic prism is divided into two prisms. FIG. 9B shows a configuration using dichroic mirrors 55 and 56 in which a dielectric multilayer film is deposited on a glass plate, instead of the color separation prism. In this case, if the thickness of the glass plate is large, aberrations are likely to occur in the projected image, so the glass plate is made thinner, and the angle of incidence of the light beam on the dichroic mirror is 45 degrees or less.
Preferably, they are arranged so as to be about 30 degrees. 5
7 is a simple mirror. Further, a color separation unit as shown in FIG. 9C may be used. This is usually a CCD
This is used for a color separation system of a camera. A dielectric multilayer film for reflecting blue light is deposited on the surface of the triangular prism prism 58 on the side of the triangular prism 60, and a red light reflecting film is formed on an interface between the triangular prism prism 60 and the square prism 59. A dielectric multilayer is deposited.

[0015]

As described above with reference to the embodiments, in the projection display apparatus according to the present invention, by disposing an intermediate lens between the optical integrator and the reflective liquid crystal panel, the color separating means and the polarizing means are provided. The reflected light passes through the color separating means and the analyzing means as parallel light rays. Therefore, a display image does not have any color unevenness or contrast unevenness, and high-quality display can be realized. Further, in the optical system according to the present invention, since the projection lens is a telecentric optical system, the projected image has no distortion and becomes a very high-quality image.

[Brief description of the drawings]

FIG. 1A illustrates a general optical integrator illumination system. FIG. 3B is a diagram illustrating an optical integrator illumination system used in the present invention.

FIG. 2A illustrates a configuration of a projection display device according to the present invention. FIG. 3B is a diagram comparing the display image quality of the projection display device of the present invention with that of the related art.

FIG. 3A is a diagram illustrating a configuration example of a light source device used for a projection display device of the present invention. FIG. 3B is a diagram illustrating a configuration example of a light source device used in the projection display device of the present invention.

FIG. 4A is a diagram showing a configuration example of a light source device used for the projection display device of the present invention. FIG. 3B is a diagram illustrating a configuration example of a light source device used in the projection display device of the present invention.

FIG. 5A is a diagram showing a configuration of a projection display device of the present invention. FIG. 2B is a diagram showing a configuration of the projection display device of the present invention.

FIG. 6A illustrates a configuration of a projection display device according to the present invention. FIG. 2B is a diagram showing a configuration of the projection display device of the present invention.

FIG. 7A illustrates a configuration of a light source device used in the present invention. FIG. 2B is a diagram showing a configuration of the projection display device of the present invention.

FIG. 8A illustrates a configuration of a projection display device according to the present invention. FIG. 2B is a diagram showing a configuration of the projection display device of the present invention.

FIG. 9A is a diagram showing a configuration of a color separation / combination unit used in the projection display device of the present invention. FIG. 3B is a diagram showing a configuration of a color separation / combination unit used in the projection display device of the present invention. FIG. 3C is a diagram showing a configuration of a color separation / combination unit used in the projection display device of the present invention.

[Explanation of symbols]

 Reference Signs List 1 light source light 2 optical integrator 3 first lens plate 4 second lens plate 6 color separation means 7 liquid crystal panel 8 intermediate lens 9 polarizing beam splitter 10 dichroic prism 11, 12, 13 liquid crystal panel 14 projection lens 37 screen

Claims (1)

[Claims] 1. A light source device, an optical integrator that converts light from a light source into a uniform light beam, a reflective liquid crystal panel that modulates a light beam from the optical integrator to display an image, and an image displayed on the reflective liquid crystal panel. In a projection display device including a projection lens for enlarging and projecting an image on a screen, a half of the optical path length is provided at a substantially intermediate position of the optical path length between the optical integrator and the reflective liquid crystal panel. A projection display device, comprising a lens section having a focal length of the order of magnitude, wherein principal rays of a light beam incident on each portion of the reflective liquid crystal panel are parallel to each other.