JPH07301801A - Liquid crystal projector - Google Patents

Abstract

PURPOSE:To reduce heat loss of the incident light at a liquid crystal panel by dividing a source rays into two orthogonally polarized rays and making a polarized direction of the liquid crystal panel coincide with a desired polarization direction of the orthogonally polarized rays. CONSTITUTION:The liquid crystal projector is provided with a light source for projection 1, a reflector 2, a cold filter 3, a polarized beam splitter 4 which executes polarization-separation of visible rays transmitted through the filter 3 and made incident thereon, reflects a first linearly polarized ray and transmits a second linearly polarized ray, a red reflecting dichroic mirror 5 reflecting only red rays in the first linearly polarized ray, a liquid crystal panel 6 for red color constituted of a liquid crystal 22 and a polarizing plate B23. Further, the liquid crystal projector is provided with a first green reflecting dichroic mirror 7 reflecting only green rays in the second linearly polarized ray, a liquid crystal panel 8 for green colon, a second green reflecting dichroic mirror 9, a liquid crystal panel 10 for blue color, a first blue reflecting dichroic mirror 11, a second blue reflecting dichroic mirror 12 and a projection lens 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projector using a transmissive liquid crystal panel as a light valve.

[0002]

2. Description of the Related Art An optical image corresponding to a video signal is formed on a liquid crystal panel, the light source light from the surface of the liquid crystal panel is irradiated, the liquid crystal panel modulates the intensity of the irradiation light, and the light is transmitted. 2. Description of the Related Art A projection-type liquid crystal projector that displays an image on a large screen by using a method of enlarging and projecting an optical image on a screen by making light incident on a projection lens is conventionally known.

When displaying a full-color image on a large screen with a conventional liquid crystal projector, the configuration of the optical system shown in FIG. 3 is adopted. In FIG. 3, 1 is a projection light source, 2 is a reflector for making white light of this light source substantially parallel light,
Unwanted components such as infrared rays are removed by passing the light from the reflector 2 through the cold filter 3 and only the red light in the visible light that has passed through the filter 3 is reflected by the red reflection dichroic mirror 40 and the first total reflection. The light is reflected by the mirror 50 and is incident on the red liquid crystal panel 16. Also,
Of the light transmitted through the red reflection dichroic mirror 40, green light is reflected by the first green reflection dichroic mirror 7,
It is incident on the liquid crystal panel 18 for green. Further, the transmitted light of the green reflection dichroic mirror 7 is directly incident on the blue liquid crystal panel 20. The light transmitted through the red liquid crystal panel 16 is transmitted through the second green reflective dichroic mirror 9, and the light transmitted through the green liquid crystal panel 18 is reflected by the second green reflective dichroic mirror 9. , And the transmitted light passing through the second blue reflection dichroic mirror 12 is combined with the light transmitted through the blue liquid crystal panel 20 reflected by the second total reflection mirror 31.
Then, the combined light is projected onto a screen (not shown) by the projection lens 13.

By the way, as shown in FIG. 2, each liquid crystal panel is composed of a polarizer A, a liquid crystal having transparent electrodes on both sides, and a polarizer B in this order from the input side. For example, the polarizer A
2 is the Y-axis direction of FIG. 2 and the polarization direction of the polarizer B is the X-axis direction, linearly polarized light in the Y-axis direction of the incident light passes through the polarizer A and passes through the liquid crystal. Polarization plane is 9
It is twisted by 0 degree and the polarization direction becomes the X-axis direction and passes through the polarizer B. When a desired potential is applied to the liquid crystal, the liquid crystal molecules are aligned in the Y-axis direction, so that the linearly polarized light in the X-axis direction that has passed through the polarizer A passes through the liquid crystal as it is and is blocked by the polarizer B. Therefore, in the polarizer A on the input side, for example,
When the polarization direction is the X-axis direction, linearly polarized light in the Y-axis direction is blocked, and about 50% of the light supplied from the projection light source in the input-side polarizer A becomes heat. , Wasted in vain. Therefore, there are problems that the polarizer A on the input side is deteriorated due to high temperature, and that light from the light source is not effectively used and the projected image is dark.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a liquid crystal projector which prevents light supplied from a light source to a liquid crystal panel from being lost as heat in the liquid crystal panel. With the goal.

[0006]

In order to achieve the above object, a light source that emits white light, and a color separation unit that selects an output component of the light source according to a wavelength region and separates into three primary colors,
Three liquid crystal panels for forming an optical image according to a video signal, irradiating each output light of the three primary colors from the color separation means, intensity-modulating the transmitted light, and transmitting the light, and three primary colors from the liquid crystal panel. In a liquid crystal projector having a color synthesizing unit for synthesizing transmitted light into one and a projection lens for receiving the output light from the color synthesizing unit and projecting the optical image on a screen, white light output from the light source is polarized. A polarized light separating means for separating two linearly polarized light whose directions are orthogonal to each other and reflecting one linearly polarized light and transmitting the other linearly polarized light is provided in front of the color separating means, and each linearly polarized light is separated into three primary colors. To illuminate the required liquid crystal panel.

[0007]

With the above-described structure, the light supplied from the light source is separated into two linearly polarized lights which are orthogonal to each other by passing through the polarized light separating means. The color separation unit separates the red (R) color from the first linearly polarized light and the blue (B) color and the green (G) color from the second linearly polarized light, for example.
For each separated color, the corresponding liquid crystal panel provided with the polarization direction in the required direction is irradiated, and the color combining means combines the output light of each liquid crystal panel into one light.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal projector according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of a liquid crystal projector according to the present invention. 1 is a projection light source using a metal halide lamp or the like, 2
Is a reflector for making the white light of the light source substantially parallel light, and 3 is a cold filter for removing unnecessary components such as infrared rays by passing the light from the reflector 2. 4 passes through the filter 3 and splits the visible light incident at an incident angle of 45 degrees to separate the first linearly polarized light into 4
It is a polarization beam splitter that reflects at an angle of 5 degrees and transmits the second linearly polarized light at the incident angle.
Reference numeral 5 is a red reflection dichroic mirror that receives the first linearly polarized light at an angle of 45 degrees and reflects only red light at an angle of 45 degrees. 6 is a liquid crystal 22 and a polarizing plate B
(23) is a liquid crystal panel for red color composed of and receives red light reflected by the red reflection dichroic mirror 5. Reference numeral 7 is a first green reflection dichroic mirror that receives the second linearly polarized light at an angle of 45 degrees, reflects only green light at an angle of 45 degrees, and transmits red light and blue light. 8 is a liquid crystal 25 and a polarizing plate B
(26) is a liquid crystal panel for green color composed of and receives the green light reflected by the first green reflection dichroic mirror 7. Reference numeral 9 is a second green reflection dichroic mirror that transmits the output of the red liquid crystal panel 6 and reflects the output of the green liquid crystal panel 8. 10 is a liquid crystal 28
And a polarizing plate B (29), which is a liquid crystal panel for blue, to which the blue light transmitted through the first green reflective dichroic mirror 7 is input. The transmitted light from the first green reflective dichroic mirror 7 is the same as that for the blue liquid crystal panel 1
It is incident on 0. The light transmitted through the red liquid crystal panel 6 is transmitted through the second green reflective dichroic mirror 9, and the light transmitted through the green liquid crystal panel 8 is reflected by the second green reflective dichroic mirror 9. , Transmitted through the second blue reflection dichroic mirror 12, and the transmitted light thereof is combined with the light transmitted through the blue liquid crystal panel 10 reflected by the first blue reflection dichroic mirror 11.
Then, the combined light is projected onto a screen (not shown) by the projection lens 13.

The operation of the liquid crystal projector according to the present invention will be described with reference to FIG. The light supplied from the projection light source 1 using a metal halide lamp or the like passes through the polarization beam splitter 4 and is separated into two linearly polarized lights of a first linearly polarized light and a second linearly polarized light which are orthogonal to each other. . On the other hand, the polarization direction on the input side of the liquid crystal panel 6 for red is set in advance so as to coincide with the polarization direction of the red light generated by the red reflection dichroic mirror 5 reflecting the first linearly polarized light. Therefore, almost 100% of the red light is incident on the liquid crystal panel 6. Further, the polarization direction on the input side of the liquid crystal panel 8 for green color is made to agree with the polarization direction of the green light generated by reflecting the second linearly polarized light by the first green reflection dichroic mirror 7 in advance. Since it is installed, almost 100% of the green light is on the liquid crystal panel 8.
Is incident on. In addition, the polarization direction on the input side of the liquid crystal panel 10 for blue color is made to match the polarization direction of the blue light generated by transmitting the second linearly polarized light through the first green reflection dichroic mirror 7 in advance. Since it is installed, almost 100% of the blue light is incident on the liquid crystal panel 10. Each liquid crystal panel 6, liquid crystal panel 8 and liquid crystal panel 1
The output light of 0 is the second green reflection dichroic mirror 9,
The light passes through the first blue reflection dichroic mirror 11 and the second blue reflection dichroic mirror 12, and is combined into one light. It should be noted that the current polarization beam splitter does not have sufficient performance to separate the light supplied from the projection light source 1 into two linearly polarized lights, and crosstalk occurs. Therefore, in order to improve the contrast of the projected image, the polarizing plate A is provided on the incident side to generate a slight heat loss, but the same effect is obtained.

[0010]

As described above, the present invention provides a liquid crystal projector that prevents light supplied from a light source to a liquid crystal panel from being lost as heat in the liquid crystal panel. Therefore, in the conventional input-side polarizer A, for example, when the polarization direction is the X-axis direction, linearly polarized light in the Y-axis direction is blocked. Approximately 50% of the light supplied to the same polarizer A becomes heat and is wasted, and the problem that the polarizer A on the input side becomes high temperature and deteriorates quickly and the light from the light source is effectively used. Instead, it has the advantage of solving the problem of dark projected images.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a liquid crystal projector according to the present invention.

FIG. 2 is a diagram showing a configuration example of a typical liquid crystal panel and polarization directions of polarizers of its constituent elements.

FIG. 3 is a block diagram of an embodiment of a conventional liquid crystal projector.

[Explanation of symbols]

 1 Projection light source 2 Reflector 3 Cold filter 4 Polarizing beam splitter 5 Red reflective dichroic mirror 6 Red liquid crystal panel 7 First green reflective dichroic mirror 8 Green liquid crystal panel 9 Second green reflective dichroic mirror 10 Blue LCD panel for use 11 First blue reflective dichroic mirror 12 Second blue reflective dichroic mirror 13 Projection lens 16 Liquid crystal panel for red 18 Liquid crystal panel for green 20 Liquid crystal panel for blue 21 Polarizing plate A 22 Liquid crystal 23 Polarizing plate B 24 Polarizing plate A 25 Liquid crystal 26 Polarizing plate B 27 Polarizing plate A 28 Liquid crystal 29 Polarizing plate B 31 Second total reflection mirror 50 First total reflection mirror

Claims (3)

[Claims] 1. A light source that emits white light, a color separation unit that selects an output component of the light source according to a wavelength range and separates into three primary colors, and an optical image that corresponds to a video signal is formed to form the color separation unit. From each of the three primary colors of the output light, the intensity of the emitted light is modulated, and the three liquid crystal panels are transmitted through the liquid crystal panel; In a liquid crystal projector having a projection lens for receiving the output light from a color synthesizing means and projecting the optical image on a screen, white light output from the light source is split into two linearly polarized lights whose polarization directions are orthogonal to each other, A liquid crystal is characterized in that a polarized light separating means for reflecting the linearly polarized light and transmitting the other linearly polarized light is provided in front of the color separating means, and the linearly polarized light is separated into three primary colors to illuminate a required liquid crystal panel. projector. 2. The liquid crystal projector according to claim 1, wherein the liquid crystal panel is composed of a liquid crystal and a polarizing plate provided on the output side. 3. The liquid crystal projector according to claim 1, wherein the polarized light separating means comprises a polarized beam splitter.