JPH0743662A - LCD projector - Google Patents

Abstract

(57) [Abstract] [Objective] In a liquid crystal projector using a dispersion type liquid crystal panel, by providing a first polarizer and a second polarizer, conventional Schlieren optics can be realized without changing the F value. Improving the contrast performance by almost 2 times compared to the system. [Structure] The transmitted light 10 of the PBS 8 passes through the quarter-wave plate 12 to become clockwise circularly polarized light 13 and is incident on a reflective and dispersion type liquid crystal panel 14. When the voltage is off, the liquid crystal molecules 15 are randomly arranged and become cloudy,
It becomes a mode that diffusely reflects light. At this time, since random birefringence is also generated at the same time, the reflected light 16 of the liquid crystal panel 14 is in a non-polarized state. The reflected light 16 is a quarter wave plate 1
2 is transmitted again, but the transmitted light 17 is also unpolarized.
The unpolarized transmitted light 17 is incident on the PBS 8 again, and approximately half the S-polarized light 18 of the transmitted light 17 is reflected.

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 which irradiates a dispersion type liquid crystal panel with illumination light from a light source and projects an image of the liquid crystal panel onto a screen by a projection lens. The present invention relates to a liquid crystal projector using a liquid crystal panel.

[0002]

2. Description of the Related Art A liquid crystal projector using this type of reflective and dispersion type liquid crystal panel is disclosed in, for example, Japanese Patent Laid-Open No.
As disclosed in FIG. 1 of 194921,
An aperture stop (corresponding to the first blocking mask 7) and a mirror (corresponding to the reflecting mirror 8) are provided, and the illumination light from the light source is applied to the liquid crystal panel via the mirror, and the reflected light from the liquid crystal panel is directed to the aperture stop. It is known that a so-called Schlieren optical system is configured to project on a screen by a projection lens via the.

According to the liquid crystal projector having this structure, the T
Compared to a liquid crystal projector using an N (twisted nematic) type liquid crystal panel, a polarizing plate is not used, so that a bright and large screen image can be obtained on the screen. Also, since a reflective liquid crystal panel is used, the optical system is smaller than a projector using a transmissive liquid crystal panel. Further, as compared with the transmissive liquid crystal panel, the reflective liquid crystal panel has a larger pixel aperture ratio, so that a brighter image can be obtained.

[0004]

However, the liquid crystal projector using the dispersion type liquid crystal panel generally has a lower image contrast than the liquid crystal projector using the TN type liquid crystal panel under the same F value condition.
Also, the contrast of a liquid crystal projector using a reflective liquid crystal panel is lower than that of a liquid crystal projector using a transmissive liquid crystal panel.

Therefore, in the above-mentioned conventional liquid crystal projector, in order to obtain a predetermined contrast, it is necessary to set the diameter of the aperture stop forming the Schlieren optical system to be sufficiently small, that is, to set the F value large. However, when the F value is increased, the brightness is lowered, and there is a problem that the brightness, which is a characteristic of the dispersion type or reflection type liquid crystal panel, cannot be sufficiently obtained.

Therefore, an object of the present invention is to improve the contrast performance of a dispersion type liquid crystal panel, particularly a liquid crystal projector using a reflection type and dispersion type liquid crystal panel without changing the F value.

[0007]

In order to achieve the above object, according to the present invention, a liquid crystal projector which illuminates illumination light from a light source on a dispersion type liquid crystal panel and projects an image on the liquid crystal panel onto a screen by a projection lens. In the above, a first polarizer and a second polarizer are provided, and the illumination light from the light source is
Light emitted from the first polarizer to the liquid crystal panel, light emitted from the liquid crystal panel to the second polarizer, and light emitted from the second polarizer projected. It was configured to be incident on the lens.

[0008]

The polarized light that has passed through the first polarizer is made incident on the dispersion type liquid crystal panel.

In the dispersion type liquid crystal panel, when the voltage is turned off, the liquid crystal molecules are randomly arranged and become opaque, which is a mode in which light is diffusely reflected. At this time, most of the reflected light of the liquid crystal panel is blocked by the aperture stop that constitutes the Schlieren optical system, resulting in black display. At this time, random birefringence also occurs at the same time, so that the reflected light of the liquid crystal panel is in a non-polarized state, and approximately half of the light passing through the second polarizer is further blocked.

On the other hand, when the voltage is turned on, the liquid crystal molecules are aligned in the thickness direction of the liquid crystal panel to be in a transparent state, which is a mode in which light is specularly reflected. At this time, most of the reflected light of the liquid crystal panel passes through the aperture stop of the Schlieren optical system, and the display becomes white. At this time, since no birefringence occurs, most of the light passes through the second polarizer.

Therefore, according to the above construction, it is possible to obtain a contrast which is about twice as high as that of the conventional Schlieren optical system.

[0012]

Embodiments of the present invention will be described in detail below with reference to the drawings.

1 and 2 are sectional views of a liquid crystal projector optical system according to a first embodiment of the present invention. Illumination light 2 from a metal halide lamp 1 which is a light source is incident on a polarization beam splitter (PBS) 8 which is a polarizer through a reflector mirror 3, a filter 4, a light refracting plate 5, an aperture stop 6 and a condenser lens 7. The incident light 9 of the PBS 8 is non-polarized light, and includes P-polarized light (polarized light parallel to the paper surface) component and S-polarized light (polarized light perpendicular to the paper surface) component equally. The incident light 9 is polarized and separated by the PBS 8 into a transmitted light 10 having a P polarization component and a reflected light 11 having an S polarization component.

Liquid crystal panels 14 and 23 will be described below with reference to FIG.
A case will be described where is displayed in black.

The transmitted light 10 of the PBS 8 is the quarter wavelength plate 1
The light passes through 2 to become right-handed circularly polarized light 13 and is incident on a reflective and dispersive liquid crystal panel 14. Figure 1 shows a liquid crystal panel 1
Reference numeral 4 indicates a voltage-off state. The liquid crystal molecules 15 are randomly arranged and are in a cloudy state, which is a mode in which light is diffusely reflected. At this time, since random birefringence also occurs at the same time, the reflected light 16 of the liquid crystal panel 14 is in a non-polarized state. The reflected light 16 passes through the quarter-wave plate 12 again, but the transmitted light 17 is also unpolarized. The unpolarized transmitted light 17 is incident on the PBS 8 again, and approximately half the S-polarized light 18 of the transmitted light 17 is reflected. S-polarized light 18 is a projection lens 19
And is projected on the screen surface (not shown) through the aperture stop 20. This is the black display of the liquid crystal panel 14.

The reflected light 11 from the PBS 8 is reflected by the quarter wavelength plate 2
The liquid crystal panel 23 passes through 1 and becomes a counterclockwise circularly polarized light 22.
Incident on. The liquid crystal panel 23, like the liquid crystal panel 14, shows a voltage-off state. The liquid crystal molecules 24 are randomly arranged and are in a cloudy state, which is a mode in which light is diffusely reflected. At this time, random birefringence also occurs at the same time, so that the reflected light 25 of the liquid crystal panel 23 is in a non-polarized state. The reflected light 25 passes through the quarter-wave plate 21 again,
The transmitted light 26 is also non-polarized. Unpolarized transmitted light 2
6 enters the PBS 8 again, and P-polarized light 27, which is almost half of the transmitted light 26, is transmitted. The P-polarized light 27 enters the projection lens 19 and is projected on the screen surface through the aperture stop 20. This is the black display of the liquid crystal panel 23.

The display on the liquid crystal panel 14 and the display on the liquid crystal panel 23 are combined on the screen surface.

Next, referring to FIG. 2, the liquid crystal panels 14 and 23 will be described.
A case will be described in which white is displayed.

When the voltage is turned on, the liquid crystal panel 14 is in a mode in which the liquid crystal molecules 15 are aligned in the thickness direction of the liquid crystal panel 14 and become transparent, and light is specularly reflected. At this time, since birefringence does not occur, the reflected light 28 of the liquid crystal panel 14 becomes counterclockwise circularly polarized light. The reflected light 28 passes through the quarter-wave plate 12 again, but the transmitted light 29 becomes S-polarized light. The transmitted light 29 that is S-polarized light is incident on the PBS 8 again, and most of the S-polarized light 30 of the transmitted light 29 is reflected. The S-polarized light 30 enters the projection lens 19 and is projected on the screen surface through the aperture stop 20. This is the white display on the liquid crystal panel 14.

When the voltage is turned on, the liquid crystal panel 23 becomes a mode in which the liquid crystal molecules 24 are aligned in the thickness direction of the liquid crystal panel 23 and become transparent, and light is specularly reflected. At this time, since birefringence does not occur, the reflected light 31 of the liquid crystal panel 23 becomes right-handed circularly polarized light. The reflected light 31 passes through the quarter-wave plate 21 again, but the transmitted light 32 becomes P-polarized light. The transmitted light 32 that is P-polarized light is incident on the PBS 8 again, and most of the P-polarized light 33 of the transmitted light 32 is transmitted. The P-polarized light 33 enters the projection lens 19 and is projected on the screen surface through the aperture stop 20. This is the white display on the liquid crystal panel 23.

Compared with the conventional Schlieren optical system which does not use PBS, the brightness of white display is about 1/2,
The brightness of black display is about 1/4. Since the contrast is the ratio of the brightness of white display and the brightness of black display, the optical system of this configuration can obtain approximately twice the contrast as compared with the conventional Schlieren optical system.

In this embodiment, two sets of 1/4 wavelength plates 1 are used.
2, 21 and the liquid crystal panels 14 and 23 are provided, and both the transmitted light 10 and the reflected light 11 of the incident light 9 of the PBS 8 are used, so that there is no decrease in brightness.

That is, according to this embodiment, the contrast performance of the liquid crystal projector using the reflective and dispersion type liquid crystal panel can be improved without changing the aperture stop of the Schlieren optical system, that is, the F value. It was

Although the present embodiment has a configuration using two color liquid crystal panels, the present invention is not limited to this, and the present invention can also be applied to a configuration using six monochrome panels.

FIG. 3 and FIG. 4 respectively show a second embodiment of the present invention.
4A and 4B are a top view and a side view of the liquid crystal projector optical system of the example. Illumination light 2 from a metal halide lamp 1, which is a light source, is reflected by a reflector mirror 3, a filter 4, a light refraction plate 5,
The light enters the cross dichroic mirror 34 through the aperture stop 6 and is color-separated into R light 35, G light 36, and B light 37. The respective colored lights 35, 36, 37 are reflected by the mirrors 38, 39, 4
0, PBS via condenser lens 41, 42, 43
It is incident on 44, 45, and 46.

The PBS 44 includes quarter-wave plates 47 and 48.
And liquid crystal panels 49 and 50 are provided. Also, PB
In S45, the quarter wave plates 51 and 52 and the liquid crystal panel 5 are included.
3, 54 are provided. In addition, 1 in PBS46
Quarter wave plates 55 and 56 and liquid crystal panels 57 and 58 are provided.

Light emitted from each PBS 44, 45, 46 5
9, 60, 61 are condenser lenses 62, 63, 64
The light is incident on the cross dichroic mirror 65 via and is combined with the emitted light 66 by color.

The emitted light 66 is projected on the screen surface by the projection lens 68 via the aperture stop 67.

The dichroic mirrors 34 and 65, which are means for color-separating and combining R, G, and B lights, are composed of dielectric multilayer films, and generally disturb the polarization of transmitted light and reflected light. However, in this configuration, since this is not configured between the PBSs 44, 45, 46 and the liquid crystal panels 49, 50, 53, 54, 57, 58, polarization disorder does not pose a problem.

Although the reflective and dispersion type liquid crystal panels are used in the first and second embodiments, the present invention is not limited to this, and the present invention is applicable to a liquid crystal projector using a transmission type liquid crystal panel. Can also be applied.

FIG. 5 is a sectional view of a liquid crystal projector optical system according to a third embodiment of the present invention. The illumination light 2 from the metal halide lamp 1, which is the light source, is reflected by the reflector mirror 3,
The light enters the PBS 70 through the filter 4, the light refraction plate 5, the aperture stop 6, and the condenser lens 69. The incident light 71 of the PBS 70 is unpolarized light and is P-polarized light (polarized light parallel to the paper surface).
The component and the S-polarized light component (polarized light perpendicular to the paper surface) are equally included. The incident light 71 is polarized and separated by the PBS 70 into a transmitted light 72 of a P polarized component and a reflected light 73 of an S polarized component.

The transmitted light 72 of the PBS 70 is reflected by the mirror 74 and is incident on the transmissive and dispersive liquid crystal panel 75. On the other hand, the reflected light 73 from the PBS 70 is reflected by the mirror 76 and enters the liquid crystal panel 77.

The case where the liquid crystal panels 75 and 77 display black will be described below.

The liquid crystal panel 75 is in a voltage-off state. Although the mode is one in which light is diffusely reflected, random birefringence is also generated at the same time, so that the transmitted light 78 of the liquid crystal panel 75 is in a non-polarized state. Non-polarized transmitted light 78 is P
The light enters the BS 79, and P-polarized light 80, which is about half the transmitted light 78, is transmitted.

Like the liquid crystal panel 75, the liquid crystal panel 77 shows a voltage-off state. It becomes a mode that diffusely reflects light, but at the same time random birefringence also occurs, so
The transmitted light 81 of the liquid crystal panel 77 is in a non-polarized state. The non-polarized transmitted light 81 enters the PBS 79 and
About half of the S-polarized light 82 is reflected.

The P-polarized light 80 and the S-polarized light 82 are the projection lens 83.
And is projected on the screen surface through the aperture stop 84. This is the black display on the liquid crystal panels 75 and 77.

The display of the liquid crystal panel 75 and the display of the liquid crystal panel 77 are combined on the screen surface.

The description is omitted when the liquid crystal panels 75 and 77 display white.

Compared with the conventional Schlieren optical system which does not use PBS, the brightness of white display is about 1/2,
The brightness of black display is about 1/4. Since the contrast is the ratio of the brightness of white display and the brightness of black display, the optical system of this configuration can obtain approximately twice the contrast as compared with the conventional Schlieren optical system.

In this embodiment, two liquid crystal panels 7 are used.
Since 5 and 77 are provided and both the transmitted light 72 and the reflected light 73 of the incident light 71 of the PBS 70 are used, there is no decrease in brightness.

That is, according to this embodiment, the contrast performance of the liquid crystal projector using the transmissive and dispersion type liquid crystal panel can be improved without changing the aperture stop of the Schlieren optical system, that is, the F value. It was

In this embodiment, two color liquid crystal panels are used, but the present invention is not limited to this, and the second
It is needless to say that the present invention can be applied to a structure using six monochrome panels as in the above embodiment.

According to the first embodiment, as shown in FIG. 6, the image on the screen is displayed by the liquid crystal panel 23 while the polarization direction of the image 85 by the liquid crystal panel 14 is the vertical direction 86. The polarization direction of the image 87 is 88 in the horizontal direction.
Becomes That is, it is possible to project two images having different polarization directions.

Therefore, as shown in FIG. 7, a projection image is formed by using polarizing glasses provided with a polarizing plate 90 having a vertical polarization direction 89 for the right eye and a polarizing plate 92 having a horizontal polarization direction 91 for the left eye. By viewing, a twin-lens stereoscopic image display device can be obtained with only one liquid crystal projector according to the present invention.

It goes without saying that the liquid crystal projectors of the second and third embodiments can also be applied to stereoscopic display.

The present invention is intended to improve the contrast of the reflective and dispersion type liquid crystal projector, but according to the present embodiment, compared with the conventional reflective and TN type liquid crystal projector. It is possible to obtain a better contrast. This is a conventional reflection type and T
The contrast performance of the N-type liquid crystal projector is almost determined by the polarization separation performance of the PBS, which is a polarizer, whereas the reflection-type and dispersion-type liquid crystal projector of the present invention has the contrast performance of the Schlieren optical system and the polarization performance. This is because the contrast is improved by the synergistic effect of the polarization splitting action of the beam splitter.

For example, the polarization separation performance of a general PBS for visible light has a P-polarized transmittance and an S-polarized reflectance of about 98%,
The P polarized light reflectance and the S polarized light transmittance are about 2%, and in this case, the contrast of the conventional TN type liquid crystal projector is about 50%.
Becomes On the other hand, in the case of the dispersion type liquid crystal projector of the present invention, if the contrast of 50 can be secured by the schlieren optical system, it is possible to achieve the contrast of 100, which is approximately double, due to the polarization separation action of the PBS.

[0048]

As described above, according to the present invention,
A liquid crystal projector in which illumination light from a light source is applied to a dispersive liquid crystal panel and an image on the liquid crystal panel is projected onto a screen by a projection lens. The liquid crystal projector includes a first polarizer and a second polarizer, and The illumination light is made incident on the first polarizer, the light emitted from the first polarizer is made incident on the liquid crystal panel, the light emitted from the liquid crystal panel is made incident on the second polarizer, and the light is emitted from the second polarizer. It is configured such that the emitted light of is incident on the projection lens.

As a result, the dispersion type liquid crystal panel has the first
The polarized light that has passed through the polarizer will be incident.

In the dispersion type liquid crystal panel, when the voltage is turned off, the liquid crystal molecules are randomly arranged and become opaque, which is a mode in which light is diffusely reflected. At this time, most of the reflected light of the liquid crystal panel is blocked by the aperture stop that constitutes the Schlieren optical system, resulting in black display. At this time, since random birefringence is also generated at the same time, the reflected light of the liquid crystal panel is in a non-polarized state, and approximately half of the light passing through the second polarizer is further blocked.

On the other hand, when the voltage is turned on, the liquid crystal molecules are aligned in the thickness direction of the liquid crystal panel to be in a transparent state, which is a mode in which light is specularly reflected. At this time, most of the reflected light of the liquid crystal panel passes through the aperture stop of the Schlieren optical system, and the display becomes white. At this time, since no birefringence occurs, most of the light passes through the second polarizer.

Therefore, according to the above structure, the contrast performance of the dispersion type liquid crystal panel, in particular, the liquid crystal projector using the reflection type and dispersion type liquid crystal panel is compared with that of the conventional Schlieren optical system without changing the F value. Approximately 2
The effect is that it can be doubled.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal projector optical system of the present invention.

FIG. 2 is a cross-sectional view of a liquid crystal projector optical system of the present invention.

FIG. 3 is a top view of a liquid crystal projector optical system of the present invention.

FIG. 4 is a side view of the liquid crystal projector optical system of the present invention.

FIG. 5 is a sectional view of a liquid crystal projector optical system of the present invention.

FIG. 6 is a diagram showing an image on a screen.

FIG. 7 is a perspective view of polarizing glasses.

[Explanation of symbols]

1 ... Metal halide lamp, 2 ... Illumination light, 3 ... Reflector mirror, 4 ... Filter, 5 ... Photorefractive plate, 6 ... Aperture stop, 7 ... Condenser lens, 8 ... PBS, 9 ... Incident light,
10 ... Transmitted light, 11 ... Reflected light, 12 ... Quarter wave plate, 1
3 ... Circularly polarized light, 14 ... Liquid crystal panel, 15 ... Liquid crystal molecule, 16
... reflected light, 17 ... transmitted light, 18 ... reflected light, 19 ... projection lens, 20 ... aperture stop, 21 ... quarter wave plate, 22 ... circularly polarized light, 23 ... liquid crystal panel, 24 ... liquid crystal molecule, 25 ... reflection Light, 26 ... transmitted light, 27 ... transmitted light, 28 ... reflected light, 29
... transmitted light, 30 ... reflected light, 31 ... reflected light, 32 ... transmitted light, 33 ... transmitted light, 34 ... cross dichroic mirror, 35 ... R light, 36 ... G light, 37 ... B light, 38 ... mirror, 39 ... Mirror, 40 ... Mirror, 41 ... Condenser lens, 42 ... Condenser lens, 43 ... Condenser lens, 44 ... PBS, 45 ... PBS, 46 ... PBS, 47
... 1/4 wave plate, 48 ... 1/4 wave plate, 49 ... liquid crystal panel, 50 ... liquid crystal panel, 51 ... 1/4 wave plate, 52 ... 1
/ 4 wave plate, 53 ... Liquid crystal panel, 54 ... Liquid crystal panel, 5
5 ... Quarter wave plate, 56 ... Quarter wave plate, 57 ... Liquid crystal panel, 58 ... Liquid crystal panel, 59 ... Emitted light, 60 ... Emitted light, 61 ... Emitted light, 62 ... Condenser lens, 63 ... Condenser lens , 64 ... Condenser lens, 65 ... Cross dichroic mirror, 66 ... Emitted light, 67 ... Aperture stop, 68 ... Projection lens, 69 ... Condenser lens, 70
... PBS, 71 ... Incident light, 72 ... S polarization, 83 ... Projection lens, 84 ... Aperture stop, 85 ... Image, 86 ... Vertical polarization,
87 ... image, 88 ... horizontal polarization, 89 ... vertical polarization direction, 9
0 ... Polarizing plate, 91 ... Horizontal polarization direction, 92 ... Polarizing plate.

Claims (8)

[Claims] 1. A liquid crystal projector in which illumination light from a light source is applied to a dispersion type liquid crystal panel and an image of the liquid crystal panel is projected onto a screen by a projection lens, wherein a first polarizer and a second polarizer are provided. The illumination light from the light source is incident on the first polarizer, the light emitted from the first polarizer is incident on the liquid crystal panel, and the light emitted from the liquid crystal panel is incident on the second polarizer. A liquid crystal projector characterized in that light emitted from the second polarizer is made incident on a projection lens. 2. A liquid crystal projector for illuminating illumination light from a light source onto a reflective and dispersive liquid crystal panel and projecting an image of the liquid crystal panel onto a screen by a projection lens,
Equipped with a polarization beam splitter and a quarter wavelength plate, the illumination light from the light source is incident on the polarization beam splitter, and the transmitted light or the reflected light from the polarization beam splitter is incident on the liquid crystal panel through the quarter wavelength plate. The reflected light from the liquid crystal panel is again made to enter the polarization beam splitter via the quarter-wave plate, and the reflected light or the transmitted light from the polarization beam splitter is made to enter the projection lens. LCD projector. 3. The liquid crystal projector according to claim 2, comprising a first quarter-wave plate, a second quarter-wave plate, a first liquid crystal panel, and a second liquid crystal panel. , The illumination light from the light source is incident on the polarization beam splitter, the transmitted light from the polarization beam splitter is incident on the first liquid crystal panel via the first quarter wavelength plate, and the reflected light from the polarization beam splitter is A liquid crystal projector, characterized in that the liquid crystal projector is configured to enter the second liquid crystal panel via a second quarter-wave plate. 4. The liquid crystal projector according to claim 2, wherein the illumination light from the light source is red (R), green (G), blue (B).
Color separation means for color-separating each light of the
Polarization beam splitter, a second polarization beam splitter on which G light is incident, a third polarization beam splitter on which B light is incident, and R, G from the first, second and third polarization beam splitters. A liquid crystal projector, comprising: a color synthesizing unit for synthesizing the emitted lights of B colors. 5. Illumination light from a light source is incident on a polarizing beam splitter, transmitted light or reflected light from the polarizing beam splitter is incident on a reflective liquid crystal panel, and reflected light from the liquid crystal panel is again incident on the polarizing beam splitter. A liquid crystal projector in which incident light is made incident and reflected light or transmitted light from a polarization beam splitter is made incident on a projection lens, wherein the liquid crystal panel is a dispersion type liquid crystal panel. 6. A liquid crystal projector for illuminating illumination light from a light source onto a transmissive and dispersive liquid crystal panel and projecting an image of the liquid crystal panel onto a screen by a projection lens,
A first polarization beam splitter and a second polarization beam splitter are provided, illumination light from a light source is incident on the first polarization beam splitter, and transmitted light or reflected light from the first polarization beam splitter is applied to a liquid crystal panel. Liquid crystal, which is configured so that the transmitted light from the liquid crystal panel is made incident on the second polarization beam splitter, and the reflected light or the transmitted light from the second polarization beam splitter is made incident on the projection lens. projector. 7. The liquid crystal projector according to claim 6, comprising a first liquid crystal panel and a second liquid crystal panel,
The illumination light from the light source is made incident on the first polarization beam splitter, and the transmitted light from the first polarization beam splitter is made into the first light.
The liquid crystal projector is characterized in that the liquid crystal panel is made to enter the liquid crystal panel and the reflected light from the first polarization beam splitter is made to enter the second liquid crystal panel. 8. A twin-lens stereoscopic image display device using the liquid crystal projector according to claim 3 or 7.