JPH0637391Y2 - Projection liquid crystal display - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, there is a projection type liquid crystal display device in which a liquid crystal panel is provided for each color of R, G and B, and light transmitted through each liquid crystal panel is combined and projected by a dichroic mirror. No. 2916 is disclosed.

[0003]

[Problems to be solved by the invention] In the above, 4
By using two dichroic mirrors with 5 ° incidence,
Although G and B are combined, the light incident on the dichroic mirror is all parallel rays. Therefore, the diameter of the light incident on the projection lens system becomes large, the dichroic mirror requires a large area, and the projection lens system must have a large diameter, which increases the cost and increases the aberration of the projection lens system. Was too large to obtain a clear image on the screen.

The present invention provides a projection type liquid crystal display device in which the dichroic mirror can be downsized, the aperture of the projection lens system can be reduced, and a clear image can be obtained.

[0005]

According to the present invention, light transmitted through a liquid crystal panel is angled by a lens at an angle θ (0 ° <θ ≦ 5 °).
Only after converging, the light is made incident on the dichroic mirror.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 1 is a light source such as a halogen lamp or xenon lamp, 2 and 2 are cold mirrors,
Reference numerals 3 and 3 denote condenser lenses that split the light from the light source into substantially parallel light beams in two orthogonal directions, and reference numerals 4 and 4 denote heat insulating filters. 5, 5 are reflection mirrors, 6 are R and B liquid crystal panels,
7 is a G liquid crystal panel. In this example, the liquid crystal panel 6,
A positive type TN type liquid crystal is used as 7, and FIG.
As described above, two polarizing plates 8 and 9 having polarization axes orthogonal to each other are used so that the P-wave polarized light is incident on the dichroic mirror 10. Reference numerals 11 and 11 are convex lenses that converge parallel rays by θ (0 ° <θ ≦ 5 °),
Reference numeral 12 is a projection lens system.

In the above structure, the light from the light source 1 is directly or reflected by the cold mirrors 2 and 2 and is incident on the condenser lenses 3 and 3, and is generated as parallel rays. The parallel rays are reflected by the reflection mirrors 5 and 5 via the heat insulating filters 4 and 4 and supplied to the liquid crystal panels 6 and 7. The light transmitted through the polarizing plate 8, the liquid crystal panel 7, and the polarizing plate 9 and the light transmitted through the polarizing plate 8, the liquid crystal panel 6, and the polarizing plate 9 are P-wave polarized light.
Is converged by θ and supplied to the dichroic mirror 10. By thus converging parallel rays by the convex lens, the dichroic mirror can be downsized, the aperture of the projection lens system can be reduced, and the aberration can be reduced.

However, if θ is set to 5 ° or more, color shading is likely to occur on the screen and the image quality is deteriorated.

The dichroic mirror 10 uses a G-reflecting mirror. G light transmitted through the liquid crystal panel 7 is reflected, and R and B light transmitted through the liquid crystal panel 6 are transmitted and combined. The image is projected by the projection lens system 12.

In this example, the dichroic mirror 10 is constructed so that the P-wave polarized light is incident thereon.
This is for the following reason. According to an experiment by the applicant, in the case of linearly polarized light using a TN (twisted nematic) liquid crystal for a liquid crystal panel, a ghost image due to multiple reflection occurs depending on the optical axis of the light incident on the dichroic mirror. At the same time, it turned out that the image had poor color purity. That is, there is no problem if the light is incident with P-wave polarization, but the above-mentioned drawbacks occur if the light is incident with S-wave polarization. This is because the surface reflectance of the glass is different between the P wave and the S wave as shown in FIG.
This is because the spectral characteristics of the dichroic mirror are different between the P wave and the S wave as shown in FIG.

As can be seen from FIG. 3, when the incident angle is around 45 °, the P wave is hardly reflected, but the S wave is reflected. This means that, in FIG. 5, when the S-wave is incident on the dichroic mirror 13, the light k of the unnecessary wavelength that is reflected by the interface between the glass and the air after passing through the multilayer thin film 14 is large. Means
This also applies to the transmitted light j, and the reflected light K and k and the transmitted light J and j are laterally displaced by 2t when the plate thickness of the glass is t, and enter the projection lens system. With a projection lens, the magnification is about 10 to 100 times,
If a mirror having a certain thickness is used, the above deviation is noticeable, and a ghost image is projected.

Further, FIG. 4 shows the spectral characteristics of a 45 ° incident G reflection dichroic mirror. In the P wave, the range of the reflected light wavelength is narrow, whereas in the S wave, S
It can be seen that the range is wide for waves. That is, when the S wave is made incident, not only G but also light in the range close to R and B is reflected, and the color purity deteriorates.

Therefore, in the present embodiment, the dichroic mirror 10 is constructed so that P-wave polarized light is incident. Therefore, there is almost no reflection of light of unnecessary wavelength,
Moreover, the reflected lights j and k in FIG. 5 almost disappear. Therefore, a ghost does not appear on the screen, and the reflection of light of an unnecessary wavelength is eliminated, so that an image with good color purity can be obtained.

By the way, since the light source 1 has heat, it is necessary to cool it by air. However, according to the structure of this example, the wind is released by rotating the fan from the front or the rear of the drawing,
It can be cooled efficiently.

FIG. 6 shows an example in which three liquid crystal panels 15, 16 and 17 corresponding to R, G and B are used. In the figure, 18 and 19 are polarizing plates having polarization axes orthogonal to each other, 20 and 21 are B-reflecting dichroic mirrors,
22 to 24 are convex lenses that converge parallel rays at an angle within 5 °.

In the above construction, the dichroic mirrors 10 and 21 are configured so that the P-wave polarized light is incident.

The R light that has passed through the liquid crystal panel 15 is converged by the convex lens 22 and the dichroic mirror 21,
Through 10.

On the other hand, the B light reflected by the dichroic mirror 20 is transmitted through the liquid crystal panel 17 and the convex lens 2
After being converged by 3, the light is reflected by the dichroic mirror 21 and further transmitted through the dichroic mirror 10.

The light transmitted through the dichroic mirror 20 is transmitted through the liquid crystal panel 16, converged by the convex lens 24, reflected by the reflection mirror 5, and further reflected by the dichroic mirror 10.

In this way, the lights transmitted through the respective liquid crystal panels are combined and supplied to the projection lens system 12 and projected.

Also in this example, the dichroic mirror 1
Since P-polarized light is incident on 0 and 21, ghosts can be removed and an image with good color purity can be obtained as in the previous embodiment.

By the way, in the example of FIG. 6, when a halogen lamp is used as a light source, the orientation of the lamp is adjusted according to its light distribution characteristic. That is, as shown in the same drawing, the wiring of the filament of the lamp is arranged so as to face the R liquid crystal panel 15 side. This is due to the following reasons.

The emission spectrum distribution of the halogen lamp is the strongest in R among R, G and B as shown in FIG.

On the other hand, the relationship between the wiring direction and the light intensity of the filament of the halogen lamp is weak in the wiring direction as shown in FIG.

Therefore, in order to balance the light intensities of R, G, and B, the wiring direction of the filament faces the liquid crystal panel side of R so that the light intensity to the R side becomes weaker than that to the G and B sides. It is arranged as follows.

By the way, the example of FIG. 1 or the example of FIG.
In the case of constructing a stereoscopic image display device by using a set, as shown in FIG. 9, each set of G-reflecting dichroic mirrors 10 and 10 is provided in front of the projection lenses 25 and 26. You can do so.

However, the light incident on each dichroic mirror is limited to P waves.

The present invention is not limited to the above embodiment, but can be applied to all projection type display devices using a liquid crystal panel and a dichroic mirror.

The position of the polarizing plate need not be on both sides of the liquid crystal panel, and the same effect can be obtained by arranging the polarizing plate in front of the projection lens or in front of the screen.

In the above embodiments, the positive type TN type liquid crystal panel is used, but a negative type one may be used. In this case, two polarizing plates whose polarization axes are parallel to each other are used.

[0031]

According to the present invention, light transmitted through a plurality of liquid crystal panels is converged by an angle θ (0 ° <θ ≦ 5 °) by a lens and then combined by a dichroic multiplexer. Since the dichroic multiplexer can be downsized and the diameter of the light incident on the projection lens system can be reduced, inexpensive dichroic multiplexers and projection lens systems can be used, and the aberration of the projection lens system is small. Therefore, a clear image can be obtained.
Further, since the convergence angle is within the above range, it is possible to suppress color shading due to the difference in the angle at which the light that has passed through the liquid crystal panel and the focusing lens enters the dichroic multiplexer, and the image quality does not deteriorate. .

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a part of FIG. 1 extracted.

FIG. 3 is a characteristic diagram showing the surface reflectance of glass.

FIG. 4 is a characteristic diagram showing spectral characteristics of a G reflection dichroic mirror with 45 ° incidence.

FIG. 5 is an explanatory diagram showing light reflected by a dichroic mirror.

FIG. 6 is an explanatory diagram showing another embodiment.

FIG. 7 is a characteristic diagram showing a radiation spectrum distribution of a halogen lamp.

FIG. 8 is a characteristic diagram showing the light distribution characteristics of a halogen lamp.

FIG. 9 is an explanatory diagram showing a projection lens and a dichroic mirror in front of the projection lens when the stereoscopic image display device is configured.

[Explanation of symbols]

 6,7 Liquid crystal panel 10 Dichroic mirror 11 Convex lens 13,14,15 Liquid crystal panel 22-24 Convex lens 19 Dichroic mirror

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Creator Tomoaki Takahashi 4-1-1 Taihei, Sumida-ku, Tokyo Inside Seikosha Co., Ltd. (56) References JP 61-102892 (JP, A) JP SHO 60-179723 (JP, A) JP 61-145510 (JP, A) JP 49-65200 (JP, A) JP 47-26928 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A light source section for generating substantially parallel parallel light, a plurality of liquid crystal panels to which the parallel light from the light source section is incident, and the parallel light transmitted through each of the liquid crystal panels at an angle θ.
A projection type liquid crystal display device comprising: a lens for converging only (0 ° <θ ≦ 5 °); and a dichroic multiplexer for synthesizing light converged by the lens.