JP2000221449A - Video device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a video device where trouble that green video light is not reflected is eliminated and where a video excellent in color is reflected by providing a 1/4 wavelength plate on either a liquid crystal projector or a polarizing screen. SOLUTION: This video device adopts the liquid crystal projector in a panel cross prism type separately emitting blue light, red light and green light and incorporating a 1/2 wavelength plate 10 and the polarizing screen 11. The 1/4 wavelength plate 12 is provided on either the liquid crystal projector or the screen 11. Red video light, blue video light and the green video light being linearly polarized light passing through a dichroic prism 3 pass through the 1/4 wavelength plate 12 and are all changed to circularly polarized light, whereby the intensity of three kinds of light gets somewhat low. However, the green video light is also reflected by the screen 11, so that the video excellent in the color is reflected on the screen 11. Furthermore, external light is partially intercepted by the screen 11, whereby the vivid video is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video device for displaying an image.

[0002]

2. Description of the Related Art Conventionally, there has been a demand for a compact and high-brightness projector, which employs a dichroic prism 3 (cross prism) shown in FIG. A three-panel cross prism type liquid crystal projector that emits green light separately has been proposed.

Recently, with the improvement of the brightness of the light source, the surface reflection of the dichroic prism 3 and the stray light from the dichroic mirrors 1 and 2 enter the liquid crystal cells 8c and 9c from the exit side of the dichroic prism 3 and form polysilicon. It has been pointed out that the TFT liquid crystal may malfunction.

Therefore, as a countermeasure against this, as shown in FIG. 1, polarized light passing through the green liquid crystal cell 7c is applied to the red liquid crystal cell 9c.
In order to prevent light from entering the liquid crystal cell c and the blue liquid crystal cell 8c, the axis of the polarized light that has passed through the green liquid crystal cell 7c is shifted by 90 degrees from the axes of the exit side polarizing plates 8d, 9d of the red liquid crystal cell 9c and the blue liquid crystal cell 8c. A half-wave plate 10 is disposed at the position of the green liquid crystal cell 7c (in FIG. 1, the same components as those of the embodiment are denoted by the same reference numerals).

Therefore, as shown in FIG. 2, the polarized light passing through the green liquid crystal cell 7c is absorbed by the exit polarizers 9d and 8d of the red liquid crystal cell 9c and the blue liquid crystal cell 8c, and the malfunction of the polysilicon TFT liquid crystal occurs. Will be prevented.

However, in the case where the half-wave plate 10 is provided, there is no problem with a normal screen, but when combined with the polarizing screen 11, green image light does not appear,
Images with different colors appear. This is because, of the image light emitted from the dichroic prism 3, the polarization directions of the red image light and the red image light and the green image light are different (all the red image light, the blue image light and the green image light are linearly polarized), Therefore, the red image light and the blue image light are reflected by the polarizing screen 11,
Although an image appears, the green image light is absorbed by the polarizing screen 11 (see FIG. 3).

Therefore, the present inventors have conducted various studies, and as a result,
By combining a quarter-wave plate, the problem that the green image light is not reflected has been solved, and an image device capable of displaying an image with good color has been completed.

[0008]

The gist of the present invention will be described with reference to the accompanying drawings.

In a video apparatus comprising a projector and a screen, the projector is a three-panel cross-prism type that emits blue light, red light, and green light separately, and is one of them.
Adopts a liquid crystal projector with a half-wave plate 10
A polarizing screen 11 is adopted as a screen, and one
The present invention relates to an image apparatus characterized by having a / 4 wavelength plate 12.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a liquid crystal projector and a polarizing screen 11 which are of a three-panel cross prism type, each of which emits blue light, red light and green light separately, and which are equipped with a half-wave plate 10.
In a video device that employs a 波長 wavelength plate, either a liquid crystal projector or a polarizing screen 11
The red image light, the blue image light, and the green image light, which are linearly polarized lights that have passed through the dichroic prism 3, are all converted to circularly polarized light by passing through the quarter-wave plate 12 (see FIG. 4). Therefore, although the light intensities are slightly reduced in all three types, the green image light is also reflected by the polarizing screen 11,
Therefore, an image with good tint is projected on the polarizing screen, and the external light is partially blocked (absorbed) by the polarizing screen 11, so that a clear image can be obtained.

The image device of the present embodiment has a polarizing screen 11.
And a three-panel cross-prism type liquid crystal projector. As shown in FIG. 5, the liquid crystal projector converts natural light (sum of S-polarized light and P-polarized light) from a light source 13 into S-polarized light by a polarizing mechanism 14, The S-polarized light is decomposed into blue, red, and green by dichroic mirrors 4 and 5, respectively, and each light is passed through a green liquid crystal cell 7c, a blue liquid crystal cell 8c, and a red liquid crystal cell 9c to form liquid crystal cells 7c, 8c, and 9c. The light passes through the dichroic prism 3 and is of a three-panel (three liquid crystal cells) type in which a reflecting material is projected on a polarizing screen 11 stuck on the back side.

In the present embodiment, a quarter-wave plate 12 is provided on the exit surface side of the dichroic prism 3.

The dichroic mirrors 4 and 5 of the present embodiment pass specific light and reflect specific light. The dichroic mirror 4 transmits red and green light and reflects blue light. The dichroic mirror 5 transmits blue and red light and reflects green light.

The dichroic prism 3 used in the present invention is a prism in which dichroic surfaces 1 and 2 composed of dichroic mirrors are arranged in an orthogonal state as shown in FIG. The wave plate 10 is a birefringent plate whose thickness is determined so as to generate a half-wavelength optical path difference between linearly polarized lights vibrating in directions perpendicular to each other.

A quarter-wave plate is a birefringent plate having a thickness determined so as to generate a quarter-wavelength optical path difference between linearly polarized lights vibrating in directions perpendicular to each other. When linearly polarized light having a main axis direction and an azimuth of 45 degrees is put in the plate, the transmitted light becomes circularly polarized light.

The quarter-wave plate used is red,
A wide-band quarter-wave plate that achieves a quarter-wavelength optical path difference over the entire main wavelength range of the blue and green projector lights is desirable.

In FIG. 5, reference numeral 6 is a total reflection mirror, and reference numeral 7
a, 8a, 9a are incident-side polarizing plates, and symbols 7b, 8b, 9b
Denotes a half-wave plate, and reference numerals 7d, 8d, and 9d denote exit-side polarizing plates.

In the present invention, the quarter-wave plate 12 may be attached to the front surface of the polarizing screen 11, or may be provided in a projector.

In this embodiment, the quarter-wave plate 12 is provided to make the green image light appear. However, the red image light does not appear, and the red image light appears. Similarly, a case where a quarter-wave plate is provided in order to make blue video light appear is also included in the present invention.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a conventional three-panel cross prism type liquid crystal projector.

FIG. 2 is an explanatory diagram when a half-wave plate 10 is provided in the liquid crystal projector of FIG.

3 is an explanatory diagram illustrating that green image light from the liquid crystal projector in FIG. 2 does not appear on a polarizing screen 11. FIG.

FIG. 4 is an explanatory diagram of the principle of the present invention.

FIG. 5 is an explanatory diagram of the present embodiment.

FIG. 6 is an explanatory diagram of a dichroic prism (cross prism).

[Explanation of symbols]

 10 1/2 wave plate 11 Polarizing screen 12 1/4 wave plate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03B 33/12 G03B 33/12 F term (Reference) 2H021 BA01 2H088 EA12 EA49 HA13 HA17 MA05 2H091 FA08Z FA21Z LA30 MA07 2H099 AA12 BA09 CA07 CA08

Claims (1)

[Claims] 1. An image apparatus comprising a projector and a screen, wherein a projector is a liquid crystal projector having a three-panel cross prism type that emits blue light, red light, and green light separately and having a half-wave plate built therein.
A polarizing screen is adopted as the screen, and 1/4 is applied to either the liquid crystal projector or the polarizing screen.
An imaging device comprising a wavelength plate.