JPH05119285A - Projection type display device - Google Patents

Abstract

PURPOSE:To obtain a projection type display device where the display brightness of a screen is completely made high by efficiently utilizing light emitted from a light source and a high contrast image is obtained. CONSTITUTION:This device is provided with a polarizing beam splitter 8 for separating a light beam from a light source 1 to P polarizing component and S polarizing component, and a reflection type liquid crystal display device which rotates the polarizing surface of every picture element based on a video signal for a polarized light beam from the polarizing beam splitter. The reflection type liquid crystal display device is constituted of 1st liquid crystal panel units 4 and 6 where the P polarizing component transmitted through the splitter 8 should be processed, and 2nd liquid crystal panel units 5 and 7 where the P polarizing component transmitted through the splitter 8 should be processed.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In a conventional projection type display device, FIG.
As shown in, the light emitted from the light source (47) enters the polarization beam splitter (51), and only the S-polarized component of the incident light is reflected, and the liquid crystal layer (49) and the reflection layer (50) are reflected. To the liquid crystal panel unit. On the other hand, of the incident light, P
The polarization component passes through the polarization beam splitter (51).

The S-polarized component that has entered the liquid crystal display device is reflected by the reflection layer (50), passes through the liquid crystal layer (49) again, and is emitted toward the polarization beam splitter (51). In this process, by applying a voltage (48) to the liquid crystal layer (49), the plane of polarization of each pixel is rotated based on the video signal,
The light beam is affected by birefringence due to the optical anisotropy of the liquid crystal, and is converted from S polarized light to P polarized light. Since the wavelength of light is involved in the conversion efficiency at this time, in reality, 100% conversion efficiency cannot be obtained. As a result, the light re-incident on the polarization beam splitter (51) contains, for example, 80% P-polarized component and 20% S-polarized component. Of these, P
Only the polarization component passes through the polarization beam splitter (51) and goes to the projection lens (52). On the other hand, the S-polarized component is reflected by the polarization beam splitter (51) toward the light source (47).

[0004]

Therefore, in the conventional projection type display device as shown in FIG. 5, when the light emitted from the light source (47) is substantially perfect circularly polarized light, it is incident on the polarization beam splitter (51). Since the P-polarized component of the emitted light passes through the polarization beam splitter (51) and is emitted to the outside, the amount of light traveling toward the screen is 50% of that emitted from the light source.
%, The light utilization efficiency is poor, and as a result, the display brightness of the screen cannot be sufficiently increased, and there is a problem that the contrast is lowered.

It is an object of the present invention to provide a projection type display device which can efficiently use the light emitted from a light source to sufficiently raise the display brightness of the screen and obtain a high contrast image.

[0006]

In a projection type display device according to the present invention, as a reflection type liquid crystal display device, a P polarization component separated by a polarization beam splitter is provided on each of a reflection side and a transmission side of a polarization beam splitter. And a second liquid crystal panel unit for processing the S-polarized component separated by the polarization beam splitter.

[0007]

Therefore, of the light emitted from the light source, the S-polarized component reflected by the polarization beam splitter is incident on the first liquid crystal panel unit, and P due to the birefringence of the liquid crystal layer.
The light component converted into polarized light passes through the polarizing beam splitter and is projected onto the screen. On the other hand, the P-polarized light component transmitted through the polarization beam splitter enters the second liquid crystal panel unit, and the light component converted into S-polarized light by the birefringence of the liquid crystal layer is reflected by the polarization beam splitter and is reflected on the screen. Is projected to. Then, both projection lights are superimposed on the screen to display an image.

[0008]

According to the projection type display device of the present invention,
The light utilization efficiency of the light source is improved, and it is possible to obtain a screen with high display brightness and high contrast on the screen.

[0009]

Embodiments of the projection type display device according to the present invention will be described below in detail with reference to the drawings.

First Embodiment In the projection type display device shown in FIG. 1, the indefinite polarized light emitted from the light source (1) is incident on the polarization beam splitter (8), of which only the S-polarized component is reflected. , Liquid crystal layer
It goes to the first liquid crystal panel unit composed of (4) and the reflective layer (6). A drive circuit (2) including an X driver and a Y driver is connected to the liquid crystal layer (4).

The light that has entered the first liquid crystal panel unit passes through the liquid crystal layer (4), is then reflected by the reflective layer (6), and re-enters the polarization beam splitter (8) through the same optical path. .. The polarization beam splitter (8) transmits the P-polarized light component modulated by the liquid crystal layer and projects it through the projection lens (9).
Lead to. As a result, the light beam enlarged and projected by the projection lens forms an image on a screen (not shown).

On the other hand, of the indefinite polarized light emitted from the light source (1), the P-polarized component incident on the polarization beam splitter (8) is transmitted through the polarization beam splitter, and the liquid crystal layer (5) and the reflection layer (7). To the second liquid crystal panel unit. A drive circuit (3) including an X driver and a Y driver is connected to the liquid crystal layer (5).

The light that has entered the second liquid crystal panel unit passes through the liquid crystal layer (5), is then reflected by the reflective layer (7), and reenters the polarization beam splitter (8) through the same optical path. .. The polarization beam splitter (8) reflects the S-polarized component modulated by the liquid crystal layer and guides it to the projection lens (9). As a result, the light beam enlarged and projected by the projection lens forms an image on the screen.

Therefore, the display brightness on the screen is the first among the lights re-incident on the polarization beam splitter (8).
P polarization component modulated by the liquid crystal panel unit of
It is proportional to the sum of the light amounts of the S-polarized components modulated by the second liquid crystal panel unit.

As the display system of the reflection type liquid crystal display device, due to the structure of the liquid crystal cell, the birefringence of the liquid crystal layer is not observed when a voltage is not applied to the liquid crystal layer, and the P polarized light to the S polarized light (or S polarized light) There is no light modulation from P polarized light to P polarized light, and although the screen is in a dark state, the birefringence is increased by applying a voltage, and the light modulation of P polarized light to S polarized light (or S polarized light to P polarized light) is performed. By strengthening it, a method of making a bright state on the screen (normally black), and a state in which a birefringence of the liquid crystal layer is large when a voltage is not applied to the liquid crystal layer, and a bright state is on the screen (for example, There are two methods (normally white) in which the birefringence is reduced by applying a voltage (for example, incident light with a polarization direction of 45 degrees with respect to the liquid crystal alignment direction) to reduce the birefringence. Harvesting Possible it is.

In any of the systems, the display brightness in the bright state on the screen is the P-polarized component modulated by the first liquid crystal panel unit and the second liquid crystal panel in the light re-incident on the polarization beam splitter. Since it is proportional to the sum of the amounts of S-polarized light components modulated by the unit,
Compared with the conventional liquid crystal display device using only P-polarized light or S-polarized light, the display brightness is increased to about twice, and as a result, a bright and high-contrast display image can be obtained.

Second Embodiment This embodiment relates to a projection type display device which performs multicolor display by superimposing image rays having different wavelength ranges on a screen.

As shown in FIG. 2, the light emitted from the light source (10) is converted into B, G and R dichroic mirrors (11) (12).
By sequentially passing through (13), the three primary colors of B, G and R are separated.

That is, in the blue light B reflected by the B dichroic mirror (11), the S polarization component is reflected by the polarization beam splitter (20), and the liquid crystal panel unit (1
4), the P-polarized component of blue light passes through the polarization beam splitter (20) and enters the liquid crystal panel unit (15).

The green light G reflected by the dichroic mirror for G (12) has its S-polarized component reflected by the polarization beam splitter (21), and the liquid crystal panel unit (16).
To the liquid crystal panel unit (17) after passing through the polarization beam splitter (21).

Further, the red light R reflected by the R dichroic mirror (13) has its S-polarized component reflected by the polarization beam splitter (22) and the liquid crystal panel unit (18).
The P-polarized component of the red light is transmitted through the polarization beam splitter (22) and is incident on the liquid crystal panel unit (19).

After that, the lights respectively incident on the three projection lenses (not shown) are enlarged and projected toward the screen, and are superimposed to provide a multicolor display.

According to the projection type display device, not only a high-contrast image having a bright display brightness can be obtained, but also 1
Since three colors are superimposed and displayed on the pixel, the resolution can be increased as compared with the first embodiment.

Third Embodiment The projection type display apparatus shown in FIG. 3 is also similar to the second embodiment.
Multi-color display is performed by superimposing image rays having different wavelength regions on the screen, and the basic configuration is the same as that of the second embodiment.

The light from the light source (10) is reflected by the total reflection mirror (24), and then the dichroic mirrors (13) (1) for R and G.
Pass 2) and separate into three primary colors of R, G and B.

On the reflection side of the R dichroic mirror (13), the R polarization beam splitter (22) and the liquid crystal panel units (18) and (19) are arranged, and the G dichroic mirror (12) is arranged. On the reflection side, a polarization beam splitter (21) for G and a liquid crystal panel unit (16) (17) are arranged,
Furthermore, on the transmission side of the G dichroic mirror (12), a B polarization beam splitter (20) and a liquid crystal panel unit are provided.
Place (14) and (15).

The blue combined light from the B polarization beam splitter (20) is reflected toward the screen by the total reflection mirror (25).

In the above structure, since all the optical systems are two-dimensionally arranged, it is possible to obtain a projection type display device which is more compact than that of the second embodiment.

Fourth Embodiment FIG. 4 shows a blue light dichroic mirror (26) in front of the G polarization beam splitter (21) instead of the total reflection mirror (25) in the third embodiment of FIG. This is an example of arrangement.

In this case, since the images can be combined on the screen by using two projection lenses, the apparatus can be made more compact than the third embodiment by reducing the number of lenses. ..

According to the above-mentioned projection type display device, it is possible to increase the transmittance of the polarizing plate without increasing the light quantity of the light source, increasing the aperture ratio of the liquid crystal cell used for the liquid crystal layer. The brightness of the projected image can be increased without increasing the power consumption of the light source and the reliability of the liquid crystal cell due to the increase in the amount of light incident on the liquid crystal cell. Is obtained.

The above description of the embodiments is for explaining the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope. The configuration of each part of the present invention is not limited to the above embodiment, and it is needless to say that various modifications can be made within the technical scope described in the claims. For example, in the second to fourth embodiments described above,
Although the light from one light source is separated for each wavelength, an independent light source for each wavelength may be used.

[Brief description of drawings]

FIG. 1 is a diagram showing an optical system of a first embodiment of a projection type display device according to the present invention.

FIG. 2 is a perspective view showing an optical system of Example 2 of the above.

FIG. 3 is a diagram showing an optical system of Example 3 of the above.

FIG. 4 is a diagram showing an optical system according to a fourth embodiment of the same.

FIG. 5 is a diagram showing an optical system of a conventional projection display device.

[Explanation of symbols]

 (1) Light source (4) Liquid crystal layer (5) Liquid crystal layer (6) Reflective layer (7) Reflective layer (8) Polarizing beam splitter (9) Projection lens

Claims (1)

[Claims] 1. A polarization beam splitter for separating light from a light source into a P-polarized component and an S-polarized component, and reflection for rotating a polarization plane for each pixel based on a video signal with respect to a polarized light beam from the polarization beam splitter. Type liquid crystal display device, reflected light from the liquid crystal display device is transmitted through the polarization beam splitter and sent to a projection lens, in a projection type display device for enlarging and projecting an image on a screen, the reflection type liquid crystal display device is A first liquid crystal panel unit for processing the P-polarized component separated by the polarization beam splitter and a second liquid crystal panel unit for processing the S-polarized component separated by the polarization beam splitter. Projection type display device.