JPH08223515A - Projection type image display device - Google Patents

Abstract

PURPOSE: To obtain a bright projection image by allowing the projection type image display device using a liquid crystal panel with a color filter added thereto to use a light emitted from a light source effectively. CONSTITUTION: A P polarized light separated from an optical separation PBS element 11 is made incident onto a liquid crystal panel 32 with a green color filter, and an S polarized light is made incident onto a liquid crystal panel 33 with a red color filter and onto a liquid crystal panel 36 with a blue color filter separately by a half mirror 22. The lights emitted from the liquid crystal panels are synthesized again by an optical synthesis PBS element 25 and the synthesized light is projected onto a screen 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type image display device for projecting an image displayed on a liquid crystal panel onto a screen.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for a large-screen image display device for enjoying powerful images with the enhancement of video equipment such as video tape recorders and video disc players and video software. As a conventional large-screen image display device, there is a projection television using a CRT, but since the CRT is used in the image display unit, there is a limitation in downsizing of the device due to physical restrictions of the CRT. . In order to remove this limitation and reduce the size of the device, a projection type image display device using a liquid crystal panel in the image display unit has been proposed.
Many projection-type image display devices using liquid crystal panels use three liquid crystal panels for red, green, and blue in order to obtain a color image, but recently to reduce the cost of the device. There is also proposed a projection type image display device in which a single liquid crystal panel is provided with three color filters of red, green and blue, and only one liquid crystal panel is used.

FIG. 3 is a block diagram showing the configuration of a conventional projection type image display device using a liquid crystal panel with a color filter.

In FIG. 3, a lamp 1 which is a light source is lit by a lamp lighting circuit 2, and light emitted from the lamp 1 is collected by a condenser lens 3. The light collected by the condenser lens is polarized by the incident polarization plate 4 and guided to the liquid crystal panel 5. The liquid crystal panel 5 is provided with a red, green or blue color filter for each pixel, and is provided with a color filter of the same color according to the red, green and blue video signals input by the liquid crystal drive circuit 10. Pixels are controlled on a pixel-by-pixel basis and rotate the polarization direction of incident polarized light. The outgoing polarization plate 6 is arranged so that its polarization direction is orthogonal to that of the incoming polarization plate 5, and passes or blocks light depending on the polarization direction of the light that has passed through the liquid crystal panel 5. In this way, the liquid crystal panel 5 is formed by the incident polarization plate 4 and the emission polarization plate 6.
Acts as an optical shutter. The light that has passed through the red, green, and blue pixels of the liquid crystal panel 5 is projected onto the screen 8 by the projection lens 7. Since the pixels of the liquid crystal panel 5 are small enough, the red, green, and
The projected images of the blue pixels are combined in the eye and recognized as a color image.

[0005]

However, in the projection type image display device having the conventional structure, two polarizing plates, an incident polarizing plate and an outgoing polarizing plate, are used to operate the liquid crystal panel as an optical shutter. . In particular, since the incident polarizing plate converts the light emitted from the lamp into linearly polarized light in one direction, the maximum light transmittance is 50%.
Further, although the color is displayed using the color filter, there is a problem that the utilization efficiency of the light emitted from the lamp is low because the light transmittance of the color filter is low.

The present invention has been made in view of the above points, and an object thereof is to provide a bright projection-type image display device in which the utilization efficiency of light emitted from a lamp is improved.

[0007]

In order to solve the above-mentioned problems, (1) a light beam separating element for separating a light beam emitted from a light source into a first light beam and a second light beam in a projection type image display device. When,
A first liquid crystal panel that receives the first light beam separated by the light beam separating element, a second liquid crystal panel that receives the second light beam separated by the light beam separating element, and the first liquid crystal panel A liquid crystal panel and a light beam combining element for combining the light beams emitted from the second liquid crystal panel are provided, and no polarizing plate is provided on the optical path of the light beams from the light source to the first and second liquid crystal panels. To configure. (2) A ray splitting element for splitting a light beam emitted from a light source into a first light beam and a second light beam in a projection type image display device,
A first liquid crystal panel that receives the first light beam separated by the light beam separating element, a half mirror that separates the second light beam separated by the light beam separating element into two optical paths, and a half mirror A second and a third liquid crystal panel that receives the separated second light beam, a light beam that combines the light beams emitted from the first liquid crystal panel, the second liquid crystal panel, and the third liquid crystal panel. A combination element is provided, and a polarizing plate is not provided on the optical path of light rays from the light source to the first, second, and third liquid crystal panels.

[0008]

With the above-described structure, the present invention can display a brighter projected image on the screen in a projection type image display device using a liquid crystal panel.

[0009]

【Example】

(Embodiment 1) First, a projection type image display apparatus according to an embodiment of the first invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a projection type image display apparatus according to an embodiment of the first invention. In addition,
The same parts as those of the conventional example shown in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted. In this embodiment, PBS elements are used as the light beam separating element and the light beam combining element.

In FIG. 1, 1 is a lamp which is a light source, 2
Is a lamp lighting circuit for lighting the lamp 1, 3 is a condenser lens for collecting the emitted light from the lamp 1, and 11 is for photolysis for splitting the light from the lamp 1 into P-polarized light and S-polarized light PBS element, 12 is the first liquid crystal panel, 13 is the first
Of the liquid crystal panel 12, an output polarizing plate 14 is a second liquid crystal panel, 15 is an output polarizing plate of the second liquid crystal panel 14, and 10 is an image display on the first liquid crystal panel 12 and the second liquid crystal panel 14. Liquid crystal panel drive circuit for, 21 and 23 are total reflection mirrors for guiding light rays, and 25 is the first liquid crystal panel 1
A PBS element for photosynthesis for synthesizing light that has passed through 2 and the second liquid crystal panel 14, and 7 is the first liquid crystal panel 12
A projection lens for projecting an image displayed on the second liquid crystal panel 14, and a screen 8 for projecting and displaying an image.

The operation of the projection type image display apparatus according to the first embodiment of the present invention constructed as above will be described below.

The lamp 1 is lit by a lamp lighting circuit 2, and the radiated light from the lamp 1 is collected by a condenser lens 3 and guided to a photolytic PBS element 11. The PBS element is an element that reflects or passes light depending on the polarization direction of the light. In this embodiment, as shown in FIG. 1, it transmits P-polarized light and reflects S-polarized light.

The P-polarized light is generated by the first liquid crystal panel 1.
Secondly, the S-polarized light is made incident on the second liquid crystal panel 14 by the total reflection mirror 21. The first liquid crystal panel 12 and the second liquid crystal panel 14 are liquid crystal panels having the same structure in which red, green, and blue color filters are attached to each pixel.

In order to operate the liquid crystal panel, it is necessary to make linearly polarized light incident. Therefore, a polarizing plate is usually placed immediately before the liquid crystal panel to make incident light linearly polarized light. However, in the projection type image display apparatus according to the first embodiment of the present invention, the light incident on the first liquid crystal panel 12 by the photolytic PBS element 11 is P-polarized light, and the light incident on the second liquid crystal panel is Since it is S-polarized, an incident polarizing plate is not required. First liquid crystal panel 12 and second liquid crystal panel 14
, The same image is displayed by the liquid crystal panel drive circuit 10.

The exit polarizing plate 13 of the first liquid crystal panel 12 and the exit polarizing plate 15 of the second liquid crystal panel 14 are installed in the polarization directions in which the first liquid crystal panel 12 and the second liquid crystal panel 14 act as optical shutters, respectively. To be done. Therefore, since the incident light of the first liquid crystal panel 12 and the incident light of the second liquid crystal panel have their polarization directions orthogonal to each other, the emission polarizing plates 13 and 15 are installed so that their polarization directions are orthogonal to each other. .

The light that has passed through the first liquid crystal panel 12 and the second liquid crystal panel 14 is guided to the PBS element 25 for photosynthesis by the total reflection mirrors 21 and 23 and is synthesized. The PBS element 25 for photosynthesis changes the direction of light according to the polarization direction of the light, like the PBS element 11 for photolysis.
The light that has passed through the liquid crystal panel 12 and the second liquid crystal panel 14 can be combined. PBS element 25 for photosynthesis
The light combined by is projected on the screen 8 by the projection lens 7.

As described above, since the light which has conventionally been half discarded by the incident polarizing plate can be effectively used by previously disassembling it with the PBS element, a bright projected image can be displayed.

In this embodiment, the first liquid crystal panel 12 is used.
The configuration in which the PBS element is used as the photosynthesis element for synthesizing the light that has passed through the second liquid crystal panel 14 has been described, but it is clear that the configuration is not limited to this.

As described above, in this embodiment of the first invention, the light emitted from the lamp is decomposed into P-polarized light and S-polarized light by using the PBS element, and the respective lights are divided into the first and second light. By entering the liquid crystal panel, combining the emitted light again, and projecting the combined light on the screen, it is possible to display a brighter projected image than the projection type image display device having the conventional configuration.

(Embodiment 2) Next, a projection type image display apparatus according to an embodiment of the second invention will be described with reference to the drawings. Regarding the configuration of the projection-type image display device in the embodiment of the second invention, the same parts as those of the projection-type image display device in the embodiment of the first invention shown in FIG. Detailed description is omitted. In this embodiment, PBS elements are used as the light beam separating element and the light beam combining element. FIG. 2 is a block diagram showing the configuration of the projection type image display device in one embodiment of the second invention.

In FIG. 2, reference numeral 32 is a first liquid crystal panel having a green color filter attached to the entire surface, 33 is an emission polarizing plate of the first liquid crystal panel 32, and 34 is a second output panel having a red color filter attached to the entire surface. Liquid crystal panel, reference numeral 35 is an output polarizing plate of the second liquid crystal panel 34, reference numeral 36 is a third liquid crystal panel having a blue color filter on its entire surface, reference numeral 36 is an output polarizing plate of the third liquid crystal panel 35, and reference numeral 22 is a PBS. A half mirror for splitting the S-polarized light decomposed by the element 11 into the light incident on the second liquid crystal panel 34 and the third liquid crystal panel 36, 2
Reference numeral 4 denotes a dichroic mirror for combining the light passing through the second liquid crystal panel 34 and the light passing through the third liquid crystal panel 36.

The operation of the projection type image display apparatus according to the embodiment of the second aspect of the invention configured as described above will be described below. The light emitted from the lamp 1 is collected by the condenser lens 3 and guided to the PBS element 11 for photolysis. The P-polarized light that has passed through the photolysis PBS element 11 enters the first liquid crystal panel 32. The first liquid crystal panel 32 is a liquid crystal panel having a green color filter attached to the entire surface, and a liquid crystal panel drive circuit 10 inputs a green video signal to display an image thereof. On the other hand, the S-polarized light reflected by the PBS element 11 for photolysis is divided by the half mirror 22 into light to be incident on the second liquid crystal panel 34 and the third liquid crystal panel 36. The second liquid crystal panel 34 is a liquid crystal panel having a red color filter attached to the entire surface, and a red video signal is input by the liquid crystal panel drive circuit 10 to display the image. The third liquid crystal panel 36 is a liquid crystal panel having a blue color filter attached to the entire surface, and a blue video signal is input by the liquid crystal panel drive circuit 10 to display the image. The emission polarization plates 33, 35, 37 of each liquid crystal panel are installed in the polarization direction in which each liquid crystal panel acts as an optical shutter.

The red light that has passed through the second liquid crystal panel 34 and the blue light that has passed through the third liquid crystal panel 36 are combined by the dichroic mirror 24 that reflects the red light and passes the blue light. Then, the light passing through each panel is combined by the PBS element 25 for photosynthesis and projected on the screen 8 by the projection lens 7.

In the projection type image display apparatus having the configuration of this embodiment, about 50% of all the light emitted from the lamp is incident on the first liquid crystal panel 32 displaying a green image, and the remaining light is emitted. 25% of the light is incident on the second liquid crystal panel 34 that displays a red image and the third liquid crystal panel 36 that displays a blue image. Although the present embodiment has described the above-described configuration for the purpose of increasing the amount of green light because the human eye has high visibility for green light, the present invention is not limited to this configuration and improves the image quality of the projected image. It is obvious that the color filter attached to each liquid crystal panel may be changed to achieve this.

As described above, since the light which has conventionally been half discarded by the incident polarizing plate can be effectively used by previously disassembling it with the PBS element, a bright projected image can be displayed.

As described above, in this embodiment of the second invention, the light emitted from the lamp is decomposed into P-polarized light and S-polarized light by using the PBS element, and the respective lights are divided into green, red and blue. Projecting a brighter image than the projection-type image display device having the conventional configuration by making the first, second, and second liquid crystal panels with monochromatic color filters enter, and recombining the emitted lights and projecting them on the screen. A projection type image display device capable of displaying an image can be configured.

[0028]

As described above, in the projection type image display apparatus according to the present invention, the light emitted from the lamp is separated by the PBS element and is made incident on a plurality of liquid crystal panels by the above-mentioned configuration, and each of the liquid crystal panels. The emitted light rays can be effectively used by synthesizing the light rays, and there is an excellent effect that a bright projection image can be displayed in a projection type image display device using a liquid crystal panel provided with a color filter.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a projection-type image display device according to an embodiment of the first invention.

FIG. 2 is a block diagram showing a configuration of a projection-type image display device according to an embodiment of the second invention.

FIG. 3 is a block diagram showing a configuration of a conventional projection-type image display device.

[Explanation of symbols]

 1 Lamp 2 Lamp Lighting Circuit 3 Condensing Lens 7 Projection Lens 8 Screen 10 Liquid Crystal Panel Driving Circuit 11 Photolysis PBS Element 12, 14, 32, 34, 36 Liquid Crystal Panel 13, 15, 33, 35, 37 Emission Polarizing Plate 21, 22 Total reflection mirror 23 Half mirror 24 Dichroic mirror 25 PBS element for photosynthesis

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04N 9/31 H04N 9/31 C

Claims (5)

[Claims] 1. An image display device for projecting an image displayed on a liquid crystal panel onto a screen, comprising a light beam separating element for separating a light beam emitted from a light source into first and second light beams, and the light beam. A first liquid crystal panel that receives the first light beam separated by a separation element, and a second liquid crystal panel that receives the second light beam separated by the light beam separation element;
A light beam combining element for combining light beams emitted from the first liquid crystal panel and the second liquid crystal panel is provided, and a polarizing plate is provided on an optical path of light beams from the light source to the first and second liquid crystal panels. A projection type image display device characterized by not being provided. 2. The first and second liquid crystal panels each have a color filter of one of red, green and blue for each pixel, and each of the first and second liquid crystal panels independently displays a color image. The projection type image display device according to claim 1. 3. An image display device for projecting an image displayed on a liquid crystal panel onto a screen, comprising a light beam separating element for separating a light beam emitted from a light source into a first light beam and a second light beam. A first liquid crystal panel that receives the first light beam separated by the light beam separating element, a half mirror that separates the second light beam separated by the light beam separating element into two optical paths, and a half mirror Second and third liquid crystal panels that enter the separated second light beam, a dichroic mirror that combines the light beams emitted from the second liquid crystal panel and the third liquid crystal panel, and the first liquid crystal panel A light beam combining element for combining a light beam emitted from a liquid crystal panel and a light beam combined by the dichroic mirror, and
A projection-type image display device characterized in that a polarizing plate is not provided on an optical path of a light ray from the light source to the first, second and third liquid crystal panels. 4. The first, second, and third liquid crystal panels each have a color filter of one color of red, green, or blue over the entire surface, and three first, second, and third liquid crystal panels are provided. The projection type image display device according to claim 3, wherein a color image is displayed by using the projection type image display device. 5. The projection type image display apparatus according to claim 1, wherein the light beam splitting element and the light beam combining element are polarization beam splitter elements.