JPH11167163A - Projection type picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection type picture display device obtaining a highly accurate picture where a black matrix is hardly seen and whose picture element density is double by using an inexpensive liquid crystal panel whose number of picture elements is small. SOLUTION: This display device is provided with a color light separating means to separate light from a light source part into three color light beams, a modulating means provided with a liquid crystal light valve 5 executing picture display by modulating a polarized light beam incorporated in respective luminous fluxes, a color light synthesizing means synthesizing a modulated luminous flux and a projection lens 8 enlarging and projecting a synthesized luminous flux on a screen, and is also provided with a rotary polarization control liquid crystal panel 6 controlling non-rotary polarization or 90-degree rotary polarization by the half of the field cycle or the field cycle of a video signal on the side of the color light synthesizing means between the color light synthesizing means and the projection lens and a double refraction optical element 7 branching a non-polarized incident light beam into an ordinary ray or an abnormal ray on the side of the projection lens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type image display apparatus which uses a dot matrix type liquid crystal light valve and enlarges and projects the image on a screen via a projection lens.

[0002]

2. Description of the Related Art In recent years, small televisions, laptop OA
With the remarkable commercialization of devices using a liquid crystal panel as a display device, such as devices, a liquid crystal projector has attracted attention as a large-screen display device. The liquid crystal projector has advantages over a conventional CRT projector in that it can be reduced in size and weight, is not affected by geomagnetism, and can ensure convergence accuracy uniformly over the entire display. On the other hand, liquid crystal projectors require a liquid crystal panel with a large number of pixels compared to a direct-view type liquid crystal display device, because the roughness of pixels is noticeable because the image is enlarged and projected on the screen. A liquid crystal panel is required.

FIG. 4 is a conceptual diagram showing a basic configuration of a conventional projection display device. This projection type image display device includes a light source lamp 1, a concave reflecting mirror 2, an integrator lens 3,
A field lens 4, a liquid crystal light valve 5, a projection lens 8, and a screen (not shown) are sequentially arranged in series. The light from the light source lamp 1 is collected by the concave reflecting mirror 2,
A liquid crystal light valve 5 is illuminated via an illumination optical system integrator lens 3 composed of two lens arrays and a field lens 4. The liquid crystal light valve 5 controls the transmittance of the pixel according to a video signal, and the image is enlarged and projected on a screen via a projection lens 8.

[0004] Among the projection type image display devices using a liquid crystal panel as a liquid crystal light valve, the mainstream at present is a dot matrix type, and an active matrix type using a TFT is often used. In a TFT active matrix type liquid crystal panel, transmittance cannot be controlled in a liquid crystal layer other than a display electrode of each pixel. Further, when light is applied to the channel portion of the TFT, a leakage current when the TFT is off increases due to a photoexcitation current, and the voltage holding ratio when the TFT is off becomes insufficient. In particular, in a normally white mode liquid crystal panel, portions other than the display electrodes are in a light transmitting state, so that the contrast is reduced unless the light is sufficiently shielded. Therefore, in order to obtain sufficient contrast, the TFT
A black matrix is formed on the counter electrode substrate to shield light from sneaking into the TFT and light leakage from other than the display electrode.

[0005]

However, in such a projection type image display apparatus using a dot matrix type liquid crystal panel as a liquid crystal light valve, an image composed of pixels of the liquid crystal panel is enlarged and projected on a screen by a projection lens. Therefore, when the number of pixels is small and the width of the black matrix is relatively wide, or as the magnification is increased, the pixel structure itself looks like a mosaic, and the impression when an image is viewed deteriorates.

Further, the size of the liquid crystal panel has been reduced in order to reduce the size and weight of the device itself, and the aperture ratio indicating the ratio of the aperture through which light is transmitted to the black matrix decreases. Therefore, the pixel structure itself looks clearly like a mosaic, and the impression when the image is viewed deteriorates.

As a simple method of making the pixel structure inconspicuous, it is conceivable to project the image by defocusing the projection lens so that the black matrix becomes inconspicuous, but the projected image itself becomes blurred. Furthermore, in a projection lens, since the defocus characteristics of the MTF are different between on-axis and off-axis of the optical axis, it is difficult to make the black matrix uniformly inconspicuous over the entire screen. For example, there may be a case where the black matrix is hardly seen in the periphery but the vicinity on the axis is clearly seen. Alternatively, the black matrix near the on-axis is difficult to see, but off-axis, the image itself may be too blurry to see.

There is also a method in which a diffraction grating is provided between the projection lens and the liquid crystal panel, and the black matrix is blurred by diffracted light. However, the MTF characteristic is reduced, and as a result, the sharpness of the image is reduced. The image becomes blurred and the impression worsens.

In addition, JP-A-4-113308 and JP-A-5-289044 disclose a method of artificially increasing the number of pixels by using an optical rotation control liquid crystal panel and a birefringent optical element, and projecting pseudo pixels on a black matrix. In addition, a method of making a black matrix less visible and obtaining a high-resolution projected image is also introduced. The introduced method is shown in FIG.
As shown in FIG. 4, in addition to the configuration of FIG.
The optical rotation control liquid crystal panel 6 and the birefringent optical element 7 are arranged in a series in a sequence between the liquid crystal panel and the projection lens 8, and when two or more elements are provided, it is specified that the above configuration is repeated. Therefore, although it is useful in a projection type image display device that performs color display on a single plate, in particular, a configuration in which three liquid crystal panels of red, blue, and green are used, and color separation and color synthesis are performed optically, When a dichroic prism is used as a color synthesizing unit in a projection type image display device having a pixel density three times that of a single-panel color display, selective transmission of polarized light,
If a dichroic mirror is used, a physical problem of selective reflection occurs, and a wavelength-dependent physical problem occurs between an ordinary ray and an extraordinary ray having polarization planes perpendicular to each other. Therefore, it is difficult to use the arrangement in which the colors are arranged in the above-described sequence.

[0010]

According to a first aspect of the present invention, a projection type image display apparatus is provided.
A light source unit that emits white light in one direction; a color light separation unit that separates the light from the light source unit into three color lights of red, blue, and green; and a polarized light included in a light beam from the color light separation unit. A modulating means having a liquid crystal light valve for modulating and displaying an image according to an input signal; a color light synthesizing means for synthesizing a modulated light flux modulated by the modulating means; and a modulated polarized light flux on a screen. An optical rotation control liquid crystal panel comprising a projection lens for enlarging and projecting, and a non-rotational optical rotation and a 90-degree rotation in a half field cycle of a video signal on the side of the color light combining means between the color light combining means and the projection lens; On the side of the projection lens, a birefringent optical element for splitting an unpolarized incident light beam into an ordinary light beam having a polarization plane crossing at right angles to an extraordinary light beam is provided.

In the first means, a dichroic prism is used for the color light synthesizing means, and the polarization direction of the color light traveling from the dichroic prism to the optical rotation control liquid crystal panel is the same in red, blue and green. They may be regulated and placed.

As a second means, a projection type image display apparatus according to the present invention separates light from the light source into three color lights of red, blue and green, and emits white light in one direction. A color light separating unit; a modulating unit including a liquid crystal light valve for modulating polarized light included in a light beam from the color light separating unit to display an image according to an input signal; and a modulation after being modulated by the modulating unit. A color light synthesizing means for synthesizing the light flux; and a projection lens for enlarging and projecting the modulated light flux on a screen, and the color light synthesizing means between the color light synthesizing means and the projection lens has a field cycle of a video signal. A rotation control liquid crystal panel that controls non-rotation and 90-degree rotation, and a birefringent optical element on the projection lens side that splits unpolarized incident light into ordinary and extraordinary rays having polarization planes that cross each other at right angles. ing

In the second means, a dichroic prism is used for the color light synthesizing means, and the polarization directions of the color light traveling from the dichroic prism to the optical rotation control liquid crystal panel are the same in red, blue and green. They may be regulated and placed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first projection type image display device according to the present invention comprises: a light source unit for emitting white light in one direction;
Color light separating means for separating light from the light source into three color lights of red, blue and green, and a liquid crystal for modulating polarized light contained in a light beam from the color light separating means to display an image according to an input signal A modulating means having a light valve, a color light synthesizing means for synthesizing a modulated light flux modulated by the modulating means, and a projection lens for enlarging and projecting the modulated polarized light beam on a screen; and An optical rotation control liquid crystal panel that controls non-rotation and 90-degree rotation with a half field period of a video signal on the side of the color light combining means between the means and the projection lens, and an unpolarized incident light beam on the projection lens side. By providing a birefringent optical element that splits an ordinary ray having a plane of polarization that intersects at right angles and an extraordinary ray, the non-rotated light transmitted through the optical rotation control liquid crystal panel and the polarization direction are rotated by 90 degrees. The rotatory light is projected by the birefringent optical element as a non-rotating light as an ordinary ray, and the rotatory light is projected as an extraordinary ray on a screen through a projection lens. Or, it is projected at a position shifted in an oblique direction. In other words, the extraordinary ray is projected at a position shifted in the direction regulated from the projection position of the ordinary ray, and the extraordinary ray overlaps the black matrix of the image projected by the ordinary ray, so that the black matrix becomes inconspicuous and is projected on the screen. The impression of the image is much better. However, whether the direction is vertical, horizontal, or oblique is regulated by the angle between the direction of the optical axis of the birefringent optical element and the polarization direction of light incident on the birefringent optical element. Needless to say, the light emitted from the liquid crystal light valve 5 is linearly polarized light.

In a second projection type image display apparatus according to the present invention, a light source for emitting white light in one direction and light from the light source are separated into three color lights of red, blue and green. A color light separating unit; a modulating unit including a liquid crystal light valve for modulating polarized light included in a light beam from the color light separating unit to display an image according to an input signal; and a modulation after being modulated by the modulating unit. A color light synthesizing means for synthesizing the light flux; and a projection lens for enlarging and projecting the modulated light flux on a screen, and the color light synthesizing means between the color light synthesizing means and the projection lens has a field cycle of a video signal. A rotation control liquid crystal panel that controls non-rotation and 90-degree rotation, and a birefringent optical element on the projection lens side that splits unpolarized incident light into ordinary and extraordinary rays having polarization planes that cross each other at right angles. ing Thus, the non-rotational light transmitted through the optical rotation control liquid crystal panel as it is and the rotation light whose polarization direction is rotated by 90 degrees are projected by the birefringent optical element as the non-rotational light as an ordinary ray and the optical rotation light as an extraordinary ray. The extraordinary ray is projected onto the screen via the lens, and is projected at a position shifted from the ordinary ray in the vertical, horizontal, or oblique direction. In other words, the extraordinary ray is projected at a position shifted in the direction regulated from the projection position of the ordinary ray, and the extraordinary ray overlaps the black matrix of the image projected by the ordinary ray, so that the black matrix becomes inconspicuous and is projected on the screen. The impression of the image is much better. However, whether the direction is vertical, horizontal, or oblique is regulated by the angle between the direction of the optical axis of the birefringent optical element and the polarization direction of light incident on the birefringent optical element. Needless to say, the light emitted from the liquid crystal light valve 5 is linearly polarized light.

Hereinafter, the embodiment will be described with reference to the drawings. However, since the structure from the light source to the modulation means is not limited at all, both the first and second embodiments are conventional. It may have the same configuration as the example, or may have a different configuration.

(Embodiment 1) FIG. 1 is a schematic structural view of Embodiment 1 and shows a light source lamp 1 shown in FIG.
The optical path from to the liquid crystal light valve 5 is the same as that of the conventional example, except that a total reflection mirror 9, the integrator 3 and the liquid crystal light valve 5 are provided between the lens arrays of an integrator lens 3 composed of two lens arrays as an illumination optical system. A dichroic mirror 10 as a color separating means, a dichroic prism 11 as a color synthesizing means between the liquid crystal light valve 5 and the projection lens 8, and an optical path length from the integrator lens 3 to the field lens 4 which differs by one. In the optical path, a relay lens 12 and each liquid crystal light valve 5
Total reflection mirror 9 so that the light separated into each color is guided to
Are provided as needed.

An optical rotation control liquid crystal panel 6 which is located between the liquid crystal light valve 5 of the modulation means and the projection lens 8 and controls the non-rotation and the 90-degree rotation with a half field period of the video signal is provided on the color light combining means side. And a birefringent optical element 7 for splitting an unpolarized incident light beam into an ordinary light beam and an extraordinary light beam having polarization planes orthogonal to each other on the projection lens 8 side.

The reason for the above-mentioned configuration is that the optical characteristics of the dichroic prism 11 limit the polarization directions of the red and blue lights reflected and combined to only one direction. A configuration in which the optical rotation control liquid crystal panel 6 and the birefringent optical element 7 are provided in a series order between the dichroic prism 11 and the liquid crystal light valve 5 for each color cannot be used. In other words, a configuration in which a projection image is superimposed on the black matrix 13 using the extraordinary light obtained by branching cannot be taken. Also, when a dichroic mirror is used, a problem of wavelength dependence occurs, and extraordinary lights having different color purities are superimposed on a black matrix, resulting in color unevenness on a screen.

Furthermore, although only green light which is color-combined as transmitted light can use both polarization directions, only extraordinary rays of green light are superimposed on the black matrix projected and synthesized on the screen, and as a result, the black matrix becomes green. The image looks colored, and the impression of the projected image deteriorates.

Therefore, in the first embodiment which uses three liquid crystal light valves 5 of red, blue and green and has a color separation color synthesizing means, the color synthesizing means changes the rotation control liquid crystal panel 6
Has a configuration limited to the same direction.

In the figure, the light path basically takes the same optical path as that of the conventional example shown in FIG.
And illuminates the liquid crystal light valve 5 via an integrator lens 3 and a field lens 4 for an illumination optical system composed of two lens arrays.

The linearly polarized light that has been modulated and emitted by the liquid crystal light valve 5 is non-rotated and transmitted by the polarization control liquid crystal panel 6 in the same polarization direction as the non-rotated light at a field period of 1/2 of the video signal and 90 degrees. The light is converted into an optically polarized light and enters the birefringent optical element 7. The incident light beam is split into an ordinary ray and an extraordinary ray having a polarization plane that intersects at right angles with each other, and the birefringent optical element 7 is different from the ordinary ray for the non-rotational light and the extraordinary ray for the optical rotation light. The light is branched into an optical path and projected on a screen.

Further, the birefringent optical element 7 is made of a birefringent crystal such as calcite, for example, and has the property of splitting an unpolarized incident light beam into two light beams having polarization planes crossing each other. The two split light beams normally propagate in mutually different directions and have different propagation speeds. Depending on whether the birefringent crystal is uniaxial or biaxial, there will be one or two optical axes along the crystal plane where the light beam continues the same propagation velocity and propagates on the same line.

If both surfaces of the birefringent crystal are parallel as in this embodiment and the incident direction of the light beam does not coincide with the direction of the optical axis, the light beams emitted from the crystal have their polarization planes orthogonal to each other. It splits into two polarized lights.

That is, the ordinary ray is projected on a screen (not shown) similarly to the conventionally projected polarized light, but the pixel opening of the extraordinary ray is vertically overlapped on the black matrix of the ordinary ray. It is projected at a position shifted in the horizontal, horizontal, or oblique direction. However, the direction is regulated by the direction of the optical axis of the birefringent optical element, and the amount of displacement is regulated by the thickness of the birefringent optical element.

As a result, when the black matrix 13, which is an ordinary ray projected image shown in FIG. 2A, overlaps with an extraordinary ray, an image of the projected image shown in FIG. 2B is obtained, and FIG. The image of the screen brightness is as shown in FIG. In the first embodiment, (b) of FIG.
As shown in (c), it was regulated so as to shift in the vertical direction.

That is, since the pixel openings of the extraordinary rays are projected on the black matrix 13 which looks clearly mosaic, the black matrix 13 in the vertical direction becomes inconspicuous, and the impression of image quality is markedly improved. It will be good. In addition, although the black matrix of the projection image of the extraordinary ray overlaps with the pixel opening of the adjacent ordinary ray, no problem occurs because it is basically a portion without light. (Embodiment 2) Embodiment 2 has the same configuration as the schematic configuration of Embodiment 1, but the optical rotation control liquid crystal panel 6 performs non-rotation and 90-degree rotation in the field period, and the liquid crystal light valve. 5 and is driven in synchronization with it. However, in the second embodiment, the optical axes of the optical rotation control liquid crystal panel 6 and the birefringent optical element 7 are regulated so as to be shifted in the vertical direction, and the amount of shift is regulated by the thickness of the birefringent optical element 7. did.

As a result, as shown in FIG. 3, by controlling the video signal of the odd field for the ordinary ray and the video signal of the even field for the extraordinary ray, not only the black matrix becomes inconspicuous, but also the pixel density is doubled. It is possible to obtain a high-definition image.

Therefore, in the second embodiment, a projected image having twice the pixel density as in the first embodiment can be obtained on the screen, and the impression of the image quality is significantly improved. However, in the second embodiment, the optical rotation control liquid crystal panel 6
The optical axis of the birefringent optical element 7 is regulated so as to be shifted in the vertical direction. Further, in principle, the black matrix of the extraordinary ray sometimes overlaps with the pixel opening of the adjacent ordinary ray. However, since there is basically no light, no problem occurs.

[0031]

As described above, according to the present invention, it is possible to provide a projection type image display apparatus in which a black matrix which clearly looks like a mosaic is almost invisible and the image quality is significantly improved. it can. Further, it is possible to provide a projection-type image display device that uses a low-cost liquid crystal panel with a small number of pixels, makes it difficult to see the black matrix, and can obtain a high-definition image with twice the pixel density.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is a screen image diagram of a black matrix according to the first embodiment.

FIG. 3 is a screen image diagram of the first embodiment.

FIG. 4 is a conceptual diagram showing a basic configuration of a conventional projection display device.

FIG. 5 is a conceptual diagram showing a basic configuration of a projection type display device already proposed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source lamp 2 Concave reflector 3 Integrator lens 4 Field lens 5 Liquid crystal light valve 6 Optical rotation control liquid crystal panel 7 Birefringent optical element 8 Projection lens 9 Total reflection mirror 10 Dichroic mirror 11 Dichroic prism 12 Relay lens 13 Black matrix

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 5/74 H04N 5/74 K 9/31 9/31 C

Claims (4)

[Claims] A light source unit that emits white light in one direction;
Color light separating means for separating light from the light source into three color lights of red, blue and green, and a liquid crystal for modulating polarized light contained in a light beam from the color light separating means to display an image according to an input signal A modulating means having a light valve, a color light synthesizing means for synthesizing a modulated light flux modulated by the modulating means, and a projection lens for enlarging and projecting the modulated polarized light beam on a screen; and An optical rotation control liquid crystal panel that controls non-rotation and 90-degree rotation with a half field period of a video signal on the side of the color light combining means between the means and the projection lens, and an unpolarized incident light beam on the projection lens side. A projection-type image display device comprising: a birefringent optical element that splits an ordinary ray having a polarization plane intersecting at right angles and an extraordinary ray. 2. A method according to claim 1, wherein a dichroic prism is used for the color light synthesizing means, and the polarization direction of the color light from the dichroic prism to the optical rotation control liquid crystal panel is regulated so as to be the same in red, blue and green. Item 2. The projection type image display device according to Item 1. 3. A light source unit for emitting white light in one direction;
Color light separating means for separating light from the light source into three color lights of red, blue and green, and a liquid crystal for modulating polarized light contained in a light beam from the color light separating means to display an image according to an input signal A modulating means having a light valve, a color light synthesizing means for synthesizing a modulated light beam modulated by the modulating means, a projection lens for enlarging and projecting the modulated light beam onto a screen, and the color light synthesizing means A rotation control liquid crystal panel for controlling non-rotation and 90-degree rotation in the field cycle of the video signal on the color light combining means side between the projector and the projection lens;
A projection-type image display device, comprising: a birefringent optical element for splitting an unpolarized incident light into an ordinary light having a polarization plane crossing at right angles to an ordinary light and an extraordinary light on the projection lens side. 4. A method according to claim 1, wherein a dichroic prism is used as the color light synthesizing means, and the polarization direction of the color light traveling from the dichroic prism to the optical rotation control liquid crystal panel is regulated so as to be the same in red, blue and green. Item 4. A projection type image display device according to item 3.