JPH0534677A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To make a picture element pattern, etc., on an output image inconspicu ous by setting a focal position of a projection lens to a specific position. CONSTITUTION:A liquid crystal panel being a light valve is constituted so that microlenses 28 and 29 are placed on its incident surface side and emitting surface side in accordance with each picture element, and also, a focal position of a projection lens for projecting an emitted light of the liquid crystal panel is set so that a light beam related to each picture element passing through the microlens 29 on the emitting surface side in the liquid crystal panel becomes a position F1 in which it is superposed only for adjacent picture elements. Accordingly, a light beam Li which is made incident on the liquid crystal panel is converged by the microlens 28, and can pass through the liquid crystal panel so as to avoid a black mask 27. Further, since the focal position of the projection lens is set so that the light beam L0 related to each picture element passing through the microlens 29 on the emitting surface side becomes the position F1 in which it is superposed only for adjacent picture elements, the influence of the black mask 27 does not appear on a projection image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device such as a liquid crystal projector using a liquid crystal panel in which liquid crystal pixels are arranged between signal lines and scanning lines as a light valve.

[0002]

2. Description of the Related Art A liquid crystal projector uses a liquid crystal panel as a light valve to output a color image. As an example, in a one-plate type liquid crystal projector, light is incident from a halogen lamp on a liquid crystal panel having three primary color RGB (red, green, blue) color filters. In this liquid crystal panel, for example, horizontal and vertical electrodes are arranged on a TN mode transmissive liquid crystal to form pixels in a matrix, and in each pixel corresponding to an RGB color filter, a T pixel is generated based on an RGB video signal.
By driving (transmittance control) the N liquid crystal in pixel units, a color image can be obtained as the output light of the liquid crystal panel. The output light from the liquid crystal panel is projected on the screen by the projection lens.

A three-plate type liquid crystal projector provided with three liquid crystal panels respectively corresponding to RGB lights of three primary colors (red, green and blue) is also used. In this case, the light from the light source is R light, The B light and the G light are split into three colors and made incident on each liquid crystal panel. Since each pixel is driven in each liquid crystal panel based on the video signal corresponding to each color, a color image can be obtained by recombining the light emitted from each liquid crystal panel and projecting the screen by the projection lens. .. Further, for example, a two-plate type liquid crystal projector using a liquid crystal panel corresponding to R light and B light and a liquid crystal panel corresponding to G light has been developed.

A liquid crystal panel used in such a liquid crystal display device is constructed, for example, as shown in FIG.
In the liquid crystal panel 60 shown in FIG. 10, a liquid crystal 63 is enclosed between two transparent glass substrates 61 and 62, and one of the facing parts of the transparent glass substrates 61 and 62 in which the liquid crystal 63 is enclosed. A common electrode 64 is formed on the transparent glass substrate 61 side (light incident surface side). Further, on the other transparent glass substrate 62 side (light emission surface side), a non-linear element 65 and a non-linear element 65 such as a thin film transistor (TFT) provided at signal lines and scanning lines and cross points thereof are provided. Pixel electrodes 66 and the like which are connected in a matrix between the signal lines and the scanning lines are formed. Liquid crystal pixels are formed by the pixel electrodes 66.

In such a liquid crystal panel 60, when a light beam enters from the transparent glass substrate 61 side, it is photoexcited to cause TF.
Leakage current may be generated from T, or unnecessary transmitted light may be generated from a portion where the light transmittance around the signal line and the scanning line is not controlled, so that the contrast of the image may be deteriorated. Therefore, in order to prevent this, the thin film 6 having a high light blocking property is formed on the transparent glass substrate 61 in a portion other than the liquid crystal pixels.
By patterning 7 (black mask), unnecessary light is prevented from entering.

[0006]

With a liquid crystal projector using such a liquid crystal panel, for example, 25 to 10
Although a large screen image of about 0 inch can be easily realized, for example, the above-mentioned active matrix type liquid crystal panel used for R light, G light, and B light in a three-plate type liquid crystal projector is a standard type. For example, the number of pixels is about 100,000.

However, in such a liquid crystal projector, when a large screen display is made, stripes due to the black mask 67 between pixels occur on the projected image, and the pixels (dots) become conspicuous. There was a problem that the image quality of was impaired. In a two-panel type liquid crystal projector using two liquid crystal panels or a one-panel type liquid crystal projector using one liquid crystal panel, the total number of pixels is smaller than that of a three-panel type, so that the number of pixels is more conspicuous and the black mask 67 The deterioration of the image quality due to is a more serious problem.

[0008]

In view of such problems, the present invention allows light output from a light source to enter a liquid crystal panel driven as a light valve based on a video signal,
In a liquid crystal display device that displays an image by projecting light emitted from this liquid crystal panel with a projection lens,
The liquid crystal panel, which is a light valve, has microlenses arranged on the incident surface side and the emission surface side corresponding to each pixel, and the focal position of the projection lens that projects the light emitted from the liquid crystal panel is The light rays of the respective pixels that have passed through the microlenses on the exit surface side of the liquid crystal panel are set so as to be overlapped only between adjacent pixels.

[0009]

By arranging the microlenses on the incident surface side and the emission surface side of the liquid crystal panel, the light rays incident on the liquid crystal panel can pass through the liquid crystal panel so as to avoid the black mask, and the focus of the projection lens can be increased. The position is set so that the light rays of each pixel passing through the microlenses on the exit surface side of the liquid crystal panel overlap only between the adjacent pixels, so that the effect of the black mask appears on the projected image. Absent.

[0010]

1 shows a projection optical system of a liquid crystal projector as an embodiment of the present invention. Reference numeral 1 is a metal halide lamp serving as a light source, and 2 is a dichroic mirror capable of selectively transmitting light of a predetermined wavelength. Here, only G light is transmitted. 3a, 3b are mirrors, 4
Reference numerals a and 4b denote condenser lenses.

Reference numeral 5 _G denotes a liquid crystal panel on which the G light dispersed by the dichroic mirror 2 is incident, and pixels are formed by an active matrix system as shown in FIG. 2, for example. In this matrix section, the gate line driving circuit scans the gate lines G _{1 to} G _{m in a} line-sequential manner to turn on the active element T (TFT: thin film transistor) for each horizontal line, and the signal line driving circuit A drive voltage based on the G video signal E _G is applied to the lines S _{1 to} S _n , and a signal charge is supplied to the capacitor C. The liquid crystal LC is driven (excited) by the signal charges until the next scan. Is transmittance control of each pixel (liquid crystal cell) by the above scanning, G image is obtained from the liquid crystal panel 5 _G.

Reference numeral 5 _RB is a liquid crystal panel on which R light and B light are incident, and by forming R and B color filters 5F corresponding to the respective pixels, the R light is transmitted to the R pixel and the B light is transmitted. It is incident on the B pixel. Then, similarly to the liquid crystal panel 5 _G , in the active matrix system, the R liquid crystal cell and the B liquid crystal cell are driven based on the R video signal E _R and the B video signal E _B , respectively, and an RB composite image is output. 6
Is a dichroic mirror that reflects only G light,
Light emitted from the liquid crystal panel 5 _G and the liquid crystal panel 5 _RB are combined by this dichroic mirror, and a color image is projected on the screen through the projection lens 7.

In this embodiment, all pixels of the liquid crystal panel 5 _G are used for G light, but in the liquid crystal panel 5 _RB , the pixels are divided into R and B at a ratio of 1: 1. The pixels of 5 _RB and 5 _G are shown in FIGS.
It will be configured as shown in.

The structure of the liquid crystal panels 5 _G and 5 _RB in the liquid crystal projector of this embodiment is shown in FIG. Figure 4
LCD panels 5 _G and 5 _RB are two transparent glass substrates 2
A liquid crystal 23 is sealed between 1 and 22, and a common electrode 24 is formed on one transparent glass substrate 21 side.

On the other side of the transparent glass substrate 22, the signal lines S _{1 to} S _n and the gate lines G _{1 to} G shown in FIG. 2 are provided.
_m and a non-linear element 25 such as a thin film transistor T provided at the cross points thereof are arranged, and connected to the non-linear element 25 to connect the signal lines S _{1 to} S _n and the gate line G.
Pixel electrodes 26 arranged in a matrix are formed between _{1 and} G _m . Each liquid crystal pixel is formed by the pixel electrode 26.

Reference numeral 27 is a thin film (black mask) having a high light-shielding property, which is patterned so that unnecessary light does not enter the portion which does not correspond to a pixel on the transparent glass substrate 21 side.

Further, on the outer surface of the transparent glass substrate 21, that is, on the incident surface side on which the G light, or the R light and the B light are incident as substantially parallel rays, as can be seen from FIG. A lens 28 is provided. Also,
Corresponding to the microlens 28 on the transparent glass substrate 21 side, the microlens 2 is also formed on the outer surface side of the transparent glass substrate 22.
9 is provided. That is, a pair of microlenses (28, 2) are attached to the transparent glass substrates 21, 22 for each pixel.
9) corresponds.

Therefore, such a liquid crystal panel 5 _G , 5 _RB
Almost all the components of the incident light L _i incident on are converged by each microlens 28, do not reach the black mask 27, and pass through the pixel portion functioning as a light valve. Then, the light beam whose transmittance is controlled pixel by pixel further passes through the transparent glass substrate 22, is refracted at a predetermined angle by the microlens 29, and is emitted from the liquid crystal panels 5 _G and 5 _RB as substantially parallel light beams L _o .

In the liquid crystal projector of this embodiment, with respect to the light emitted from the liquid crystal panels 5 _G and 5 _RB , the light emitted from each pixel unit is overlapped (or contacted) only between adjacent pixels. A certain point F ₁ shown in FIG. 4 is set to be the focal position of the projection lens 7. At the point F ₁ , since the emitted lights L ₀ corresponding to the respective pixels are in a state of being overlapped with each other, almost all light components forming an image are light components that have properly passed through the pixels serving as the light valves.

Therefore, since the focus position of the projection lens 7 is set to point F ₁ which is deviated from the liquid crystal panels 5 _G and 5 _RB , the influence of the black mask on the projected image on the screen by the projection lens 7, that is, It will be solved that the dots and stripe patterns corresponding to the pixels are conspicuously generated and the image quality is deteriorated.

In the liquid crystal panels 5 _G and 5 _RB ,
Due to the action of the microlenses 28 and 29, most of the incident light components are converted into the light emitted from the liquid crystal panel after the transmittance is controlled, so that there is an advantage that the aperture ratios of the liquid crystal panels 5 _G and 5 _RB are improved.

FIG. 6 shows the case where the incident light L _i is the focused light and the divergent light with respect to the above liquid crystal panels 5 _G and 5 _RB . In a liquid crystal display device such as a liquid crystal projector, the light source 1 such as a metal halide lamp is not strictly a point light source, and a light component that directly advances to the liquid crystal panels 5 _G and 5 _RB without passing through a parabolic reflector. That there is
Further, due to the design conditions of the optical system such as the condenser lenses 4a and 4b, the incident light L _i on the liquid crystal panel often has a focused light component and a divergent light component.

Such focused light and divergent light are incident light L _i.
In the case of the liquid crystal projector supplied as above, the position where the emitted light of each pixel unit overlaps (or contacts) only between the adjacent pixels as shown in FIG.
Therefore, the focal position of the projection lens 7 is set to point F _{2 in the} figure, for example. Also in this case, it is almost eliminated that dots or stripe patterns corresponding to pixels are conspicuous in the image projected on the screen by the projection lens 7 and the image quality is impaired.

By the way, FIG. 7 (a) (b) are those showing another example of a pixel arrangement in the liquid crystal panel 5 _RB, 5 _G, the liquid crystal panel 5 _RB, 5 _G of FIG. 7 in this embodiment When adopted, the microlenses 28 and 29 provided on the transparent glass substrates 21 and 22 are also formed corresponding to this pixel array, for example, as shown in FIG. Also in this case, the same effect as described above can be obtained.

Further, in the pixel array of FIGS. 3 and 7, if the stripes are conspicuous in the horizontal direction on the projected image when the microlens is not provided, for example, a semi-cylindrical microscopic structure as shown in FIG. 9 is used. The lenses 28 and 29 may be provided on the outer surfaces of the transparent glass substrates 21 and 22. Of course, the vertical micro lens 2
It may be appropriate to arrange 8,29. That is, this is a case where a liquid crystal panel in which vertical stripes appear on the projected image is used.

Although the above embodiment has been described with reference to a liquid crystal projector, the present invention can be applied to any display device using a liquid crystal panel as a light valve. Of course, the projection optical system is not limited to the two-panel type that uses two liquid crystal panels.
The present invention is also useful for plate type, one plate type and the like.

[0027]

As described above, in the liquid crystal display device of the present invention, the liquid crystal panel driven as a light valve is
Microlenses are arranged on the incident surface side and the exit surface side corresponding to each pixel, and the focus position of the projection lens is such that the light rays of each pixel passing through the microlens on the exit surface side are adjacent to each other. By setting the positions so that they overlap each other, it is possible to eliminate the conspicuous formation of dots or stripe patterns corresponding to pixels on the output video, and it is possible to improve the image quality.

[Brief description of drawings]

FIG. 1 is an optical block diagram showing an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of a matrix portion of the liquid crystal panel in the present embodiment.

FIG. 3 is an explanatory diagram of a pixel configuration example of a liquid crystal panel in the present embodiment.

FIG. 4 is an explanatory diagram of focus positions of a liquid crystal panel and a projection lens in the present embodiment.

FIG. 5 is an explanatory diagram of microlenses of the liquid crystal panel in the present embodiment.

FIG. 6 is an explanatory diagram of focus positions of a liquid crystal panel and a projection lens in the present embodiment.

FIG. 7 is an explanatory diagram of another pixel configuration example of the liquid crystal panel in the present embodiment.

FIG. 8 is an explanatory diagram of another microlens of the liquid crystal panel in the present embodiment.

FIG. 9 is an explanatory diagram of still another microlens of the liquid crystal panel in the present embodiment.

FIG. 10 is an explanatory diagram of a conventional liquid crystal panel.

[Explanation of symbols]

5 _G , 5 _RB liquid crystal panel 7 Projection lens 21, 22 Transparent glass substrate 23 Liquid crystal 28 29 Micro lens

Claims (1)

Claim: What is claimed is: 1. Light emitted from a light source is incident on a liquid crystal panel driven as a light valve based on a video signal, and light emitted from the liquid crystal panel is projected by a projection lens. In a liquid crystal display device for displaying an image, the liquid crystal panel has microlenses arranged on the incident surface side and the emission surface side thereof corresponding to each pixel,
The liquid crystal display device is characterized in that the focal position of the projection lens is set at a position where the light rays of each pixel passing through the microlenses on the exit surface side overlap only between adjacent pixels.