JPH075458A - Projection type liquid crystal display unit - Google Patents

Abstract

PURPOSE:To provide the projection type liquid crystal display device which can project a bright image by generating luminous flux which has an identical vibration direction and a convergence angle from light which has random vibration-direction components of electric field vector and using the luminous flux as a light source. CONSTITUTION:The shape of a polarization beam splitter 12 is so determined that linearly polarized light reflected by the polarized light separating surface 15 of the polarization beam splitter 12 is projected slantingly from its optical surface, and this device is provided with a reflecting mirror 13 which reflects the linearly polarized light refracted by the beam splitter and a phase difference plate 14 which converts the plane of polarization of the reflected linearly polarized light into a plane parallel to transmitted light. The incident light is split into P-polarized light and S-polarized light by passing through those optical systems, and the reflected S-polarized light is refracted and then reflected and further has the plane of polarization converted to provide irradiation in the same direction with the transmitted light. At this time, the optical surface of the polarization beam splitter is formed slantingly, so the reflected light can be reflected inwardly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type liquid crystal display device, in which two polarized lights having vibration directions of electric field vectors orthogonal to each other are extracted from light having a random polarization component, and the electric field vector of one polarization is vibrated. The present invention relates to a projection-type liquid crystal display device that converts the direction of light by 90 degrees and combines it with the other polarized light to convert it into image information using a liquid crystal panel and project it on a screen.

[0002]

2. Description of the Related Art A projection type liquid crystal display device is a device for projecting an image by using a liquid crystal panel as a light valve. FIG. 2 shows an outline of the projection type liquid crystal display device. The projection type liquid crystal display device includes a light source 21, an irradiation optical system 22, a liquid crystal panel 23, and a projection optical system 24. The luminous flux from the light source 21 is
The irradiation optical system 22 gives desired characteristics such as parallelization and polarization, and the liquid crystal panel 23 converts the desired characteristics. Then, the light flux is projected onto the screen 25 by the projection optical system 24. Here, when the liquid crystal panel 23 is used to display an image by adjusting the transmission amount of polarized light, the operating principle of the liquid crystal panel 23 causes light having a certain direction of vibration of the electric field vector to have a certain direction. It can only be used as a light source. Light having an unusable electric field vector vibration direction was absorbed by the polarizing plate or the like provided in the liquid crystal panel 23 or the irradiation optical system 22. For this reason, there is a problem that the light transmitted through the liquid crystal panel is only 50% of the light source even at the maximum, and the light generated by the light source cannot be effectively used.

As a device for solving this problem, we have
The light from the light source is split by a polarization beam splitter into two types of linearly polarized light whose electric field vector vibrating directions are orthogonal to each other, and the vibrating direction of the electric field vector of polarized light having a vibrating direction that cannot be used as the light source of the liquid crystal panel is rotated by 90 degrees. Japanese Patent Application No. 4-33821 discloses a device for changing the direction so that it can be used as a light source of a liquid crystal panel.

FIG. 3 shows the configuration of this device. This device includes a polarization beam splitter 12, a reflection mirror 13, and a retardation plate 14. The polarization beam splitter 12 is
It has a polarization splitting surface 15. The polarization splitting surface 15 has a function of splitting unpolarized light incident from a predetermined direction into two linearly polarized lights having electric field vectors orthogonal to each other, and as shown in the drawing, one is transmitted and the other is transmitted. To reflect. In the figure, the vibration direction of the electric field vector is distinguished by a circle and a line segment.A circled ray is a ray whose vibration direction is perpendicular to the paper surface, and a ray with a line segment is Vibrates in the orthogonal direction. Here, for convenience of explanation, it is assumed that light having the same vibration direction of the electric field vector as the linearly polarized light traveling straight is P-polarized light, and linear polarization having the vibration direction of the electric field vector orthogonal thereto is S-polarized light.

The light reflected by the polarization splitting surface 15 is S polarized light, and this linearly polarized light is reflected by the reflecting mirror 13 in the same direction as the transmitted light. The reflected S-polarized light is transmitted through the retardation plate 14 so that the vibration direction of the electric field vector thereof is converted into P-polarized light. As described above, this device converts the vibration direction of the electric field vector by combining the component of the light, which cannot be used conventionally, with the polarization beam splitter, the reflection mirror, and the phase difference plate.

[0006]

In the projection type liquid crystal display device, there is a case where it is desired to focus the light incident on the liquid crystal display panel. In the conventional polarized beam combiner, this is dealt with by tilting the reflection mirror.
FIG. 4 shows how the light rays are reflected at this time. As shown in the figure, when the angle a of the reflection mirror is made smaller than that in the case where the reflected light and the transmitted light form parallel rays, the light emitted from the central portion of the light source is reflected by the reflection mirror and then is reflected by the polarization beam splitter itself. Since it is incident, only a part of the whole light is emitted in the intended direction.

Therefore, an object of the present invention is to provide a projection type which is capable of irradiating a liquid crystal panel with light converted so that vibration directions of electric field vectors are in the same direction at a predetermined angle and obtaining a bright display image. An object is to provide a liquid crystal display device.

[0008]

According to a first aspect of the present invention, the light from the light source and the light from the light source incident from a predetermined direction are separated into two linearly polarized lights in which the vibration directions of the electric field vectors are orthogonal to each other. A polarization splitting means that transmits one and reflects the other in a direction orthogonal to the transmitted light, and a linearly polarized light reflected by the polarization splitting means is refracted to form an angle of 90 degrees or more with the transmitted light. A refraction means for converting the traveling direction into a direction, a reflecting means for reflecting the linear deflection whose traveling direction is converted by the refracting means and converting the traveling direction into a direction intersecting with the transmitted light, and an electric field vector of the linear deflection reflected by the reflecting means. Polarization plane conversion means for converting the vibration direction of the light into a direction that matches the vibration direction of the transmitted light, and a liquid crystal panel for adjusting the amount of the transmitted light by irradiating the light composed of the reflected light and the transmitted light whose polarization plane is converted. And Le, includes a projection optical system for projecting light transmitted through the liquid crystal panel onto a screen.

That is, in the invention described in claim 1, the polarization beam splitter is configured so that the linearly polarized light reflected by the polarization splitting surface is obliquely emitted from the optical surface of the polarization beam splitter, and the light from the light source is Of the transmitted light, linearly polarized light having a vibration direction of an electric field vector different from that of the transmitted light is converted into the same direction as the transmitted light by using the polarization beam splitter, the reflection means and the polarization plane conversion means, and the converted light The liquid crystal panel is irradiated with a predetermined concentration angle. This makes it possible to irradiate the liquid crystal panel with light converted so that the vibration directions of the electric field vectors are in the same direction, at a predetermined angle, and to obtain a bright display image.

According to the second aspect of the invention, the light from the light source and the light from the light source incident from a predetermined direction are separated into two linearly polarized lights in which the vibration directions of the electric field vectors are orthogonal to each other, and one is transmitted and the other is transmitted. Polarized light separating means for reflecting in a direction orthogonal to the transmitted light; refracting means for refracting the linearly polarized light reflected by the polarized light separating means and converting the traveling direction thereof into a direction in which the angle with the transmitted light becomes 90 degrees or more. , A polarization plane conversion means for converting the vibration direction of the linearly polarized electric field vector refracted by the refraction means into a direction coinciding with the vibration direction of the transmitted light, and the linear polarization with its polarization plane converted by the polarization plane conversion means is reflected. And a liquid crystal panel that adjusts the amount of transmitted light by irradiating light composed of the reflected light and the transmitted light whose polarization plane has been converted, and the liquid crystal panel. The light transmitted through the panel and a projection optical system for projecting a screen.

That is, according to the second aspect of the present invention, the polarization beam splitter is configured so that the linearly polarized light reflected by the polarization splitting surface is obliquely emitted from the optical surface of the polarization beam splitter, and the light from the light source is Linearly polarized light having a vibration direction of an electric field vector different from that of the transmitted light is converted to the same direction as the transmitted light by using the polarization beam splitter, the polarization plane conversion means and the reflection means, and the converted light The liquid crystal panel is irradiated with a predetermined concentration angle. This makes it possible to irradiate the liquid crystal panel with light converted so that the vibration directions of the electric field vectors are in the same direction, at a predetermined angle, and to obtain a bright display image.

According to the third aspect of the present invention, the light from the light source and the light from the light source incident from a predetermined direction are separated into two linearly polarized lights in which the vibration directions of the electric field vectors are orthogonal to each other, and one is transmitted and the other is transmitted. Polarized light separating means for reflecting in a direction orthogonal to the transmitted light; refracting means for refracting the linearly polarized light reflected by the polarized light separating means and converting the traveling direction thereof into a direction in which the angle with the transmitted light becomes 90 degrees or more. , A reflection means for reflecting the linearly polarized light whose traveling direction is converted by the refracting means and converting the traveling direction into a direction intersecting with the transmitted light, and an oscillation of the electric field vector of the linearly polarized light which is the transmitted light separated by the polarized light separating means. Polarization plane conversion means for converting the direction into a direction that coincides with the vibration direction of the reflected light, and the light composed of the transmitted light and the reflected light that are converted so that the polarization planes are in the same direction is irradiated, and the amount of the transmitted light is changed. Comprising a liquid crystal panel for the section, and a projection optical system for projecting the light transmitted through the liquid crystal panel onto a screen.

That is, in the third aspect of the invention, the polarization beam splitter is configured so that the linearly polarized light reflected by the polarization splitting surface is obliquely emitted from the optical surface of the polarization beam splitter, and the light from the light source is Of the reflected light, while converting the polarization plane of the transmitted light having a vibration direction of an electric field vector different from that of the reflected light to the same direction as the reflected light using the polarization plane conversion means,
The liquid crystal panel is irradiated with the reflected light at a predetermined concentration angle.
This makes it possible to irradiate the liquid crystal panel with light converted so that the vibration directions of the electric field vectors are in the same direction, at a predetermined angle, and to obtain a bright display image.

[0014]

EXAMPLES The present invention will be described in detail below with reference to examples.

FIG. 1 shows the configuration of a polarized beam combining section used in the projection type liquid crystal display device of the embodiment. This polarized beam combining unit is used as the projection optical system 22 in the projection type liquid crystal display device, and for convenience of description, the place where the angle is changed is displayed with being tilted to a larger angle than the actually used angle. The polarized beam combiner 11 includes a polarized beam splitter 1
2, the reflection mirror 13, and the phase difference plate 14. The polarization beam splitter 12 has a polarization splitting surface 15, and the surface through which the reflected light passes is inclined by α degrees as shown in the figure. The incident light is split by the polarization splitting surface 15 of the polarization beam splitter 12 into two light beams having the oscillation directions of the electric field vectors orthogonal to each other. The transmitted light is linearly polarized light in which the vibration direction of the electric field vector is perpendicular to the paper surface, and the reflected light is
It is a linearly polarized light whose vibration direction is orthogonal to this. Hereinafter, polarized light whose vibration direction is perpendicular to the paper surface will be referred to as P-polarized light, and polarized light whose vibration direction is parallel to the paper surface will be referred to as S-polarized light.

The reflected light, which is the S-polarized light separated by the polarization separation surface 15, is emitted from the polarization beam splitter 12 with respect to the normal line of the optical surface of the polarization beam splitter.
Since the light is incident at an angle, the light is refracted according to the difference in the refractive index between the polarization beam splitter and the air, and the direction is changed as shown in the figure. The reflected light that is S-polarized light whose traveling direction is changed is reflected by the reflection mirror 13. The angle a of the reflection mirror 13 is an arbitrary value, and by changing this, the direction of the reflected light can be tilted up to α degrees from the center. The reflected S polarized light passes through the retardation plate 14. The retardation plate 14 has a thickness such that the phase of the extraordinary light is delayed by ½ wavelength when light passes through the retardation plate, and the polarization direction of S-polarized light entering the retardation plate is set to 90 °.
It is installed in the direction in which it is rotated by a degree and converted into P-polarized light.

Although the polarized beam combining section of the embodiment has a bilaterally symmetrical structure, it goes without saying that the apparatus may be composed of only one side. Also, here, the polarization beam splitter and the reflection mirror are separate components,
It is also possible to integrate the polarizing beam splitter and the reflecting mirror by providing the reflecting surface of the polarizing beam splitter with the reflecting light with a reflecting function. Further, the phase difference plate can also be fixed to the polarization beam splitter and the whole structure can be configured as one prism.

Further, in the polarized beam combining section of the embodiment, the polarization plane of the light reflected by the reflection mirror is converted by using the phase difference plate. The device can also be configured to be reflected by a reflective mirror. That is, a phase difference plate may be provided on the surface through which the light reflected by the polarization splitting surface of the polarization beam splitter passes. In this case, it is necessary to cut out and use the material forming the retardation plate in such a shape as to fulfill a predetermined polarization plane conversion function.

Further, the retardation plate for converting the polarization plane may be installed so as to convert the polarization plane of the light transmitted through the polarization separation surface. That is, without converting the plane of polarization for the reflected light reflected by the polarization splitting surface, a retardation plate is provided at the exit of the transmitted light to convert the vibration direction of the electric field vector of the transmitted light into the same direction as the reflected light. . Even with such a configuration, the vibration directions of the electric field vectors of the transmitted light and the reflected light can be made the same.

When a projection type liquid crystal display device is constructed by using these three polarized beam synthesizing units having different arrangement positions of the phase difference plates as the irradiation optical system in FIG. 2, display is performed in any projection type liquid crystal display device. The brightness of the displayed image is about 3
It was possible to improve by 0%. The angle α of the polarization beam splitter used at this time is 3 °, and the angle a of the reflection mirror is 43 °. These angles are values that depend on the intended light amount distribution on the liquid crystal panel, but in this projection type liquid crystal display device, the light whose polarization plane has been converted is not blocked by the polarization beam splitter and is thus a predetermined value. The desired light amount distribution can be obtained according to the purpose. The polarized beam device
It can also be used as a part of the irradiation optical system of FIG. That is, an optical system such as a condenser lens can be added after the polarized beam combining unit.

[0021]

According to the first aspect of the present invention, since the polarization beam splitter has a trapezoidal shape, even when the reflection light is directed inward by inclining the angle of the reflection mirror, the reflection light is reflected by the polarization beam splitter. It is not blocked by the splitter.
Therefore, it is possible to illuminate the liquid crystal panel with light obtained by converting the polarization plane having a desired concentration angle in the same direction, and obtain a bright image.

According to the second aspect of the present invention, since the polarization beam splitter has a trapezoidal shape, even if the reflected light is directed inward by inclining the angle of the reflection mirror, the reflected light is reflected by the polarization beam splitter. There is no interruption. Therefore, it is possible to illuminate the liquid crystal panel with light obtained by converting the polarization plane having a desired concentration angle in the same direction, and obtain a bright image. Further, since the phase difference plate can be fixed to the polarization beam splitter, there is an advantage that the position adjustment of the phase difference plate and the polarization beam splitter becomes unnecessary.

According to the third aspect of the present invention, since the polarization beam splitter has a trapezoidal shape, even when the reflection light is directed inward by inclining the angle of the reflection mirror, the reflection light is transmitted to the polarization beam splitter. There is no interruption. Therefore, it is possible to illuminate the liquid crystal panel with light obtained by converting the polarization plane having a desired concentration angle in the same direction, and obtain a bright image. Further, since the phase difference plate can be fixed to the polarization beam splitter, there is an advantage that the position adjustment of the phase difference plate and the polarization beam splitter becomes unnecessary.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a polarized beam combining unit capable of reflecting in a predetermined direction after converting a polarization plane used in a projection type liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a configuration of a projection type liquid crystal display device.

FIG. 3 is a configuration diagram showing a configuration of a polarized beam combining unit of a conventional example.

FIG. 4 is an explanatory diagram for explaining a problem that occurs when a reflecting mirror is tilted in a polarization beam combining unit of a conventional example.

[Explanation of symbols]

 12 ... Polarizing beam splitter 13 ... Reflecting mirror 14 ... Phase difference plate 15 ... Polarization separating surface 21 ... Light source 22 ... Irradiation optical system 23 ... Liquid crystal panel 24 ... Projection optical system 25 ... Screen

Claims (3)

[Claims] 1. A light source and light from the light source which is incident from a predetermined direction are separated into two linearly polarized lights whose electric field vector oscillation directions are orthogonal to each other, one of which is transmitted and the other is orthogonal to the transmitted light. The polarized light separating means for reflecting the linearly polarized light reflected by the polarized light separating means into a direction in which an angle formed by the linearly polarized light reflected by the polarized light separating means with the transmitted light is 90 degrees or more; Reflecting means for reflecting the linearly polarized light whose traveling direction is converted by the means and converting the traveling direction into a direction intersecting with the transmitted light; and a vibrating direction of the electric field vector of the linearly polarized light reflected by the reflecting means for the transmitted light. A polarization plane conversion means for converting to a direction that matches the vibration direction of the liquid crystal panel, and a liquid crystal panel for irradiating the light composed of the reflected light having the polarization plane converted and the transmitted light and adjusting the amount of the transmitted light, A projection type liquid crystal display device, comprising: a projection optical system for projecting light transmitted through the liquid crystal panel onto a screen. 2. A light source and light from the light source, which is incident from a predetermined direction, are separated into two linearly polarized lights whose electric field vector oscillation directions are orthogonal to each other, one of which is transmitted and the other is orthogonal to the transmitted light. The polarized light separating means for reflecting the linearly polarized light reflected by the polarized light separating means into a direction in which an angle formed by the linearly polarized light reflected by the polarized light separating means with the transmitted light is 90 degrees or more; Polarization plane conversion means for converting the vibration direction of the linearly polarized electric field vector refracted by the means into a direction coinciding with the vibration direction of the transmitted light; and the reflection of the linear polarization whose polarization plane is converted by the polarization plane conversion means. And a liquid crystal that adjusts the amount of transmitted light by irradiating with light composed of the reflected light whose polarization plane has been converted and the transmitted light. Panel and projection type liquid crystal display device characterized by comprising a projection optical system for projecting the light transmitted through the liquid crystal panel onto a screen. 3. A light source and light from the light source which is incident from a predetermined direction are separated into two linearly polarized lights whose electric field vector oscillation directions are orthogonal to each other, one of which is transmitted and the other is orthogonal to the transmitted light. The polarized light separating means for reflecting the linearly polarized light reflected by the polarized light separating means into a direction in which an angle formed by the linearly polarized light reflected by the polarized light separating means with the transmitted light is 90 degrees or more; Reflecting means for reflecting the linearly polarized light whose traveling direction is converted by the means and converting the traveling direction into a direction intersecting with the transmitted light, and oscillation of the electric field vector of the linearly polarized light which is the transmitted light separated by the polarized light separating means. Polarization plane conversion means for converting the direction into a direction that coincides with the vibration direction of the reflected light, and the light composed of the transmitted light with the polarized plane converted and the reflected light is irradiated to adjust the amount of the transmitted light. A liquid crystal panel, a projection type liquid crystal display device characterized by comprising a projection optical system for projecting the light transmitted through the liquid crystal panel onto a screen.