JPH04127140A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain an image with high color temperature by spectrally diffracting light and making B light, R and G light incident on two liquid crystal panels, and multiplexing them again and obtaining a color image. CONSTITUTION:Light emitted by a light source 1 consisting of a halogen lamp is spectrally diffracted into the B light, R light, and G light; and the B light is made incident on the 1st liquid crystal panel 5B corresponding to the B light and the R light and G light are made incident on the corresponding 2nd liquid crystal panel 5B with an RG color filter. Then the projection lights of the 1st and 2nd liquid crystal panels 5B and 5RG are multiplexed and the color image is outputted. Consequently, the utilization efficiency of the B light is increased to make the color temperature high.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid crystal display device.

[Summary of the Invention] The liquid crystal display device of the present invention splits light output from a light source such as a halogen lamp into B light, R light, and G light, and includes a first liquid crystal panel corresponding to the B light, respectively; and R
A second filter having an RG color filter corresponding to light and G light.
so that the light is incident on the LCD panel. And, first,
By combining the light emitted from the second liquid crystal panel and outputting a color image, it is possible to increase the utilization efficiency of B light and increase the color temperature.

[Prior Art] Examples of liquid crystal display devices that use a liquid crystal panel as a light valve and output color images include liquid crystal projectors and color liquid crystal televisions.

For example, in an LCD projector, the three primary colors RGB (red, green,
Blue) Light from a halogen lamp is incident on a liquid crystal panel with color filters. In this liquid crystal panel, for example, horizontal and vertical electrodes are arranged on a TN mode transmissive liquid crystal to form a matrix of pixels, and in each pixel corresponding to an RGB color filter, the TN liquid crystal is displayed based on an RGB video signal. By driving (transmittance control) on a pixel-by-pixel basis, a color image can be obtained as output light from the liquid crystal panel. Output light from the liquid crystal panel is projected onto a screen by a projection lens.

In addition, a three-handling type liquid crystal projector has been implemented, which is equipped with three liquid crystal panels that correspond to the three primary colors of RGB light (red, green, and blue), and in this case, the light from the light source can be used to
It separates the light into three colors: light and G light, and makes it incident on each liquid crystal panel.

Since each liquid crystal panel is driven by a video signal corresponding to each color, a color image can be obtained by combining the emitted light from each liquid crystal panel again and projecting it on a screen using a projection lens.

[Problems to be solved by the invention] However, in these types of liquid crystal projectors,
Since the color temperature of the light emitted from the halogen lamp is approximately 3000'K, there is a problem in that it is not possible to obtain an output image with a high color temperature. The same applies to liquid crystal display devices of a screen display type rather than a projection type.

Furthermore, a single-panel LCD projector has 1/3 the number of pixels for each color compared to a 3-panel LCD projector, resulting in insufficient resolution; However, the optical system becomes complicated because the light from the light source is separated into three colors and combined again, and the number of components in the optical system increases due to the use of three expensive liquid crystal panels. , there is also the problem of a significant increase in costs.

Means for Solving Problem U] The present invention has been made in view of these problems, and includes a spectroscopic means for separating the light output from a light source into B light, R light, and G light. , a first liquid crystal panel that receives the separated B light and is driven as a B light light valve;
a second liquid crystal panel into which the R light and the G light are incident and driven as a light valve for the R light and the G light; and an output combining means for combining and outputting the light emitted from the first and second liquid crystal panels. This constitutes a two-panel liquid crystal display device.

[Function] Only the B light is separated from the R light and the G light and enters the first liquid crystal panel, and the first liquid crystal panel can obtain an image of the B light from all pixels. The utilization efficiency of B light is higher than that of light, and it becomes possible to obtain an image with a high color temperature as a color image output in which R light, G light, and B light are combined.

[Embodiment] FIG. 1 shows a projection optical system of a liquid crystal projector as an embodiment of the present invention.

1 is a halogen lamp serving as a light source; 2 is a dichroic mirror that can selectively transmit light of a predetermined wavelength; only B light is transmitted here; 3a and 3b are mirrors, and 4a and 4b are condenser lenses.

Reference numeral 56 denotes a liquid crystal panel into which the B light separated by the dichroic mirror 2 is incident, and pixels are formed, for example, in an active matrix method as shown in FIG. In this matrix section, the gate line driving circuit scans the gate lines G, ~G, in a line sequential manner, and the active element T (TFT: thin film transistor) is turned on for each horizontal line, and the signal line driving circuit scans the gate lines G, ~G, and turns on the active element T (TFT: thin film transistor) for each horizontal line. Line SI
~S, &, : A driving voltage based on the B video signal is applied, and a signal charge is supplied to the capacitor C. This signal charge drives (excites) the liquid crystal LC until the next scan. The transmittance of each pixel (liquid crystal cell) is controlled by the above scanning, and the transmittance of each pixel (liquid crystal cell) is controlled. A B image can be obtained from.

5 RG is a liquid crystal panel into which R light and G light are incident, and R and G color filters are formed corresponding to each pixel, so that R light enters the R pixel and G light enters the G pixel. be done. Similarly to the liquid crystal panel 5°, the R liquid crystal cell and the G liquid crystal cell are respectively driven based on the R video signal and the G video signal in an active matrix system, and an RG composite image is output.

Reference numeral 6 denotes a guichroic mirror that reflects only the B light, and this guichroic mirror combines the light emitted from the liquid crystal panels 5B and 5RG, and a color image is projected on the screen via the projection lens 7. Become.

In this embodiment, the liquid crystal panel 5! All pixels of l are B
This is used for light, but in the liquid crystal panel 586, the pixels are divided into R and G at a ratio of 1=1, so for example, each liquid crystal panel 566 and 5 pixels are divided as shown in FIGS. 3(a) and 3(b). It will be composed of

Here, the R light and G light synthesized by the gicroic mirror 6 are
The amount of each of the light and B light is proportional to the number of pixels on the liquid crystal panel, so if the pixels are configured as shown in Figure 3 (a) and (b), the amount of R light: the amount of G light: the amount of B light. The amount of light is 1:1:2.

In other words, since B light can be combined with twice the efficiency of R light and G light, an image with a high color temperature can be obtained on the combined color image. In addition, as a result of the experiment conducted in accordance with the above example, the color temperature of the halogen lamp 1 was 30
It was possible to obtain a projected image with a color temperature of about 6000° for 00°K.

Furthermore, by using two units of liquid crystal panels in this embodiment, the image resolution is 1.6 times that of a single-panel projector that uses a single liquid crystal panel with the same number of pixels and RGB color filters. This will improve the degree of improvement. Furthermore, compared to a three-panel liquid crystal projector, the optical system is greatly simplified and the number of liquid crystal panels is small, so the cost will not increase significantly. That is, this embodiment can simultaneously maintain a certain degree of resolution and prevent a significant increase in cost.

Note that FIG. 4 shows an example in which the R pixels and G pixels in the liquid crystal panel 576 are arranged in a stripe pattern, and even when the liquid crystal panels 5 and 16 in FIG. 4 are adopted in this embodiment, , the same effect as above can be obtained. The same applies to other arrangements (for example, horizontal stripes).

FIGS. 5(a) and 5(b) show other embodiments of the liquid crystal panels 5RG and 58, in which the ratio of R pixels to G pixels in the liquid crystal panel 5□ is 1=2. in this case,
Liquid crystal panel 5 No. and 5. In the outgoing combined light of R
Light amount: G light amount: B light amount = 1:2:3. If the pixels are configured in this way, the color temperature will be 700 on the output video.
I was able to obtain an image of approximately 0'K. Furthermore, the resolution can be improved by about 1.8 times compared to the single-chip type.

By the way, the spectral characteristics of the halogen lamp I are as follows:
As shown in the figure, it tends to be weak in blue light and strong in red light. Therefore, when the halogen lamp 1 is used as a light source as in the above embodiment, it is not possible to set the ratio of R light:G light:B light in the output combined light to 1:1:2 or 1:2:3. This is also effective in optimizing the color balance of the projected image.

Note that although the above embodiments have been described using a liquid crystal projector as an example, similar effects can be obtained with liquid crystal display devices other than projection type.

Further, although the light source has been described as a halogen lamp, it goes without saying that images with higher color temperature can be obtained regardless of the type of light source.

[Effects of the Invention] As explained above, the liquid crystal projector of the present invention has the following effects:
By configuring the first and second liquid crystal panels to separate B light, R light and G light, and combine them again to obtain a color image, the B light, R light and It can be used more effectively than light, and therefore has the effect of making it possible to obtain images with a high color temperature.

Further, there is an advantage that the resolution can be improved to a certain degree and the cost does not increase significantly.

[Brief explanation 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 section of a liquid crystal panel, and Fig. 3 (a) and (b) are diagrams of a liquid crystal panel in an embodiment of the present invention. An explanatory diagram of an example of a pixel configuration. FIG. 4 is an explanatory diagram of another example of a pixel configuration of a liquid crystal panel according to an embodiment of the present invention. FIGS. FIG. 6 is an explanatory diagram of an example of the pixel configuration, and FIG. 6 is an explanatory diagram of the spectral characteristics of a halogen lamp as a light source. 1 is a halogen lamp, 2 and 6 are dichroic mirrors
3a and 3b are mirrors 4a and 4b are condenser lenses,
5B and 5*a are liquid crystal panels, and 7 is a projection lens. % fiber chart

Claims (3)

[Claims] (1) A spectrometer that separates the light output from the light source into B light, R light, and G light, and a first liquid crystal that is driven as a light valve for the B light separated by the spectrometer. a second liquid crystal panel that is driven as a light valve for the R light and G light separated by the spectroscopy means, and combines and outputs the light emitted from the first and second liquid crystal panels. A liquid crystal display device comprising an emitted light combining means. (2) Claim 1, characterized in that the second liquid crystal panel driven as a light valve for R light and G light has R pixels and G pixels arranged at a ratio of 1:1. The liquid crystal display device described in . (3) Claim 1, characterized in that the second liquid crystal panel driven as a light valve for R light and G light has R pixels and G pixels arranged at a ratio of 1:2. The liquid crystal display device described in .