JP2522592Y2 - Projection type liquid crystal display - Google Patents

Description

[Detailed description of the invention]

[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, a liquid crystal panel is provided for each of R, G, and B colors, and a projection type liquid crystal display device that combines and transmits a light transmitted through each liquid crystal panel by a dichroic mirror is disclosed in Japanese Patent Application Laid-Open No. Sho. No. 60-2916.

[0003]

[Problem to be solved by the invention]
° Using two incident dichroic mirrors, R, G,
Although B is synthesized, no attention is paid to the optical axis of light incident on the dichroic mirror.

According to an experiment conducted by the present applicant, the liquid crystal panel has a T
In the case of linearly polarized light using an N (twisted nematic) type liquid crystal, a ghost image due to multiple reflection is generated and an image having poor color purity is produced depending on the optical axis of light incident on the dichroic mirror. It turned out to be. In other words, there is no problem if the incident light is P-polarized light, but the above-described disadvantage occurs if the incident light is S-wave polarized light. This is because the surface reflectance of the glass is different between the P wave and the S wave as shown in FIG. 7 and the spectral characteristics of the dichroic mirror are different between the P wave and the S wave as shown in FIG. Things.

As can be seen from FIG. 7, when the incident angle is around 45 °, the P wave is hardly reflected, but the S wave is reflected. This means that, in FIG. 9, when the S-wave is incident on the dichroic mirror 25, of the unnecessary wavelength light, the light k reflected by the boundary between glass and air after passing through the multilayer thin film 26 is large. Means that. This also applies to the transmitted light j, and the reflected light K and k and the transmitted light J and j are shifted laterally by 2t when entering the projection lens system when the thickness of the glass is t. With a projection lens, the magnification is about 10 to 100 times.
If a mirror having a thickness of about mm is used, the above-mentioned shift is noticeable and is projected as a ghost image.

FIG. 8 shows the spectral characteristics of a 45 ° incident G reflection dichroic mirror. In the case of a P wave, the wavelength range of reflected light is narrow,
It can be seen that the range is wide in waves. That is, when an S wave is incident, not only G but also light in a range close to R and B is reflected, and the color purity is deteriorated.

An object of the present invention is to obtain an image having no ghost and excellent color purity.

[0008]

According to the present invention, in a projection type liquid crystal display device comprising a liquid crystal panel, light incident on a dichroic mirror uses P-polarized light.

In FIG. 1, 1 is a light source such as a halogen lamp or a xenon lamp, 2 and 2 are cold mirrors,
Reference numerals 3 and 3 denote condenser lenses for dividing 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 is R, B liquid crystal panels,
Reference numeral 7 denotes a G liquid crystal panel. In this example, the liquid crystal panels 6,
As for No. 7, a positive type TN type liquid crystal is used.
In absorption optical axis two polarizing plates 8 and 9 having a (Z-axis) using mutually orthogonal as, dichroic the dichroic mirror 10 of the P-wave polarized light are configured to be incident. Absorbing axis and
Refers to an axis that absorbs light that vibrates in the axial direction. 1
Reference numerals 1 and 11 denote convex lenses that converge parallel rays by θ (0 ≦ θ ≦ 5 °), and 12 denotes a projection lens system.

In the above configuration, 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 to be generated as parallel rays. The parallel rays are reflected by the reflection mirrors 5 and 5 via the heat protection filters 4 and 4 and supplied to the liquid crystal panels 6 and 7. 7. Light transmitted through polarizing plate 8, liquid crystal panel 7, and polarizing plate 9 and polarizing plate The light transmitted through the liquid crystal panel 6 and the polarizing plate 9 is P-wave polarized light, which is a convex lens 11,11.
Is converged by θ and supplied to the dichroic mirror 10. By converging the parallel rays with the convex lens in this manner, 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 tends to occur on the screen, and the image quality deteriorates.

The dichroic mirror 10 is of a type that reflects G light. 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. , And is projected by the projection lens system 12.
Since the P-polarized light is incident on the dichroic mirror 10, there is almost no reflection of light having a wavelength other than G.
In addition, the reflected lights j and k in FIG. 9 almost disappear.
Therefore, no ghost appears on the screen, and reflection of light having an unnecessary wavelength is eliminated, so that an image with good color purity can be obtained.

By the way, the light source 1 has heat and needs to be cooled by air. However, according to the configuration of this embodiment, the wind is blown out by turning the fan from the front or rear of the drawing.
It can be cooled efficiently.

FIG. 3 shows an example in which three liquid crystal panels 13, 14, and 15 corresponding to R, G, and B are used. In the figure, 16 and 17 are polarizing plates having polarization axes orthogonal to each other, 18 and 19 are dichroic mirrors of B reflection,
20 to 22 are convex lenses that converge parallel rays at an angle of 5 ° or less.

In the above configuration, the dichroic mirrors 10 and 19 are configured so that P-wave polarized light is incident thereon.

The R light transmitted through the liquid crystal panel 13 is converged by the convex lens 20 and becomes a dichroic mirror 19,
10 is transmitted.

On the other hand, the B light reflected by the dichroic mirror 18 passes through the liquid crystal panel 15 and passes through the convex lens 2.
After being converged by 1, the light is reflected by the dichroic mirror 19 and further passes through the dichroic mirror 10.

The light transmitted through the dichroic mirror 18 is transmitted through the liquid crystal panel 14, converged by the convex lens 22, reflected by the reflection mirror 5, and further reflected by the dichroic mirror 10.

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

In this example, the dichroic mirror 1 is also used.
Since P-polarized light is incident on 0 and 19, ghosts can be removed and an image with good color purity can be obtained as in the previous embodiment.

In the example shown in FIG. 3, when a halogen lamp is used as a light source, the direction of the lamp is adjusted according to the light distribution characteristics. That is, as shown in the figure, the lamp is arranged such that the wiring direction of the filament of the lamp faces the liquid crystal panel 13 side of R. This is for the following reason.

As shown in FIG. 4, the emission spectrum distribution of the halogen lamp is the strongest at R among R, G and B.

On the other hand, the relationship between the wiring direction of the filament of the halogen lamp and the light intensity is weaker 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 is directed to the liquid crystal panel side of R so that the light intensity on the R side is weaker than that on the G and B sides. It is arranged as follows.

By the way, the example of FIG. 1 or the example of FIG.
When a stereoscopic image display device is configured by using a set, as shown in FIG. 6, the G reflection dichroic mirrors 10 and 10 of each set are arranged in front of the projection lenses 23 and 24 as shown in FIG. What is necessary is just to provide.

However, the light incident on each dichroic mirror is a P-wave only.

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 may not be provided on both sides of the liquid crystal panel, and the same effect can be obtained by disposing the polarizing plate in front of the projection lens or in front of the screen. However, the configuration must be such that only the P-wave polarization that has passed through the dichroic mirror can be projected.

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

[0030]

According to the present invention, when light transmitted through a plurality of liquid crystal panels is combined by a dichroic mirror, only the P-polarized light is incident on the dichroic mirror. -It is possible to obtain an image with no strike and good color purity.

[Brief description of the 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.

FIG. 3 is an explanatory view showing another embodiment.

FIG. 4 is a characteristic diagram showing a radiation spectrum distribution of a halogen lamp.

FIG. 5 is a characteristic diagram showing light distribution characteristics of a halogen lamp.

FIG. 6 is an explanatory diagram showing a projection lens and a dichroic mirror in front of the projection lens when configuring a stereoscopic image display device.

FIG. 7 is a characteristic diagram showing surface reflectance of glass.

FIG. 8 is a characteristic diagram showing spectral characteristics of a G reflection dichroic mirror incident at 45 °.

FIG. 9 is an explanatory diagram showing light reflected by a dichroic mirror;

[Explanation of symbols]

 6, 7 liquid crystal panel 8, 9 polarizing plate 10 dichroic mirror 13, 14, 15 liquid crystal panel 16, 17 polarizing plate 19 dichroic mirror

Continuing on the front page (72) Inventor Shingo Takahashi 4-1-1, Taihei, Sumida-ku, Tokyo, Japan Inside Seikosha Co., Ltd. (72) Inventor Tomoaki Takahashi 4-1-1, Taihei, Sumida-ku, Tokyo Intracompany Seikosha (56) References JP-A-61-102892 (JP, A) JP-A-60-179723 (JP, A) JP-A-47-26928 (JP, A)

Claims (1)

(57) [Scope of request for utility model registration] 1. A liquid crystal panel comprising: a plurality of liquid crystal panels; and a dichroic mirror for synthesizing light transmitted through each of the liquid crystal panels.
A predetermined angle rotation about the center axis from the facing state
And the dichroic
Center the absorption axis of the polarizing plate on the side facing the
A projection type liquid product display device, wherein only a P-wave polarized light is incident on the dichroic mirror as a direction parallel to the axis, and the light synthesized by the dichroic mirror is projected.