JPH03201695A - Projecting display device - Google Patents

Abstract

PURPOSE:To utilize all incident beams as projecting beams as a principle and to enable bright projecting display by splitting the incident beam into two light components, making the respective light components incident to two liquid crystal display elements and afterwards further synthesizing the transmitted beams. CONSTITUTION:The beam from a light source 11 is splitted into two linearly polarized components, which are mutually orthogonal, namely, into a P polarized component and an S polarized component by a polarizing splitter 14a and any one of these linearly polarized components is made incident to a black/white liquid crystal display panel equipped with a polarizing board at a polarizing angle to modulate light transmissivity. Then, the other remained component is made incident to a color liquid crustal display panel 13a equipped with the polarizing board at the polarizing angle to modulate the light transmissivity and the transmitted beams of these respective liquid crystal display panels are synthesized by a light synthesizer 14b. To these respective liquid crystal display panels 13a and 13b, the luminance signal and hue signal of a color input signal are applied. Thus, as a picture synthesized by the light synthesizer 14b, a color picture can be reproduced corresponding to the color input signal and display quality such as brightness or resolution is improved. Then, a projecting display device is realized to be composed of simple optics.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a display device capable of displaying a large screen, and particularly to a projection display device using a liquid crystal display panel as a light pulp.

BACKGROUND OF THE INVENTION Various large display devices are in demand for applications such as electronic conferences, education, sales and corporate presentations, and public displays. Large-scale display devices include direct-view types using large CRTs, LED displays, etc., and projection-type CRTs and projection types that project the display of various light pulps onto an external screen via an optical system. Large display devices using this method are being commercialized. In particular, in recent years, as liquid crystal panel technology has improved, liquid crystal projection display devices that use liquid crystal display elements (hereinafter referred to as liquid crystal panels) as light pulp have been in the spotlight.

There are various types of liquid crystal projection display devices. In the old days, a method of using a heat-responsive smectic liquid crystal panel, writing on it with laser light, and enlarging the display by irradiating it with light from an external light source was actively developed, and some of it was even put into practical use. . However, this method requires tens of seconds to rewrite the screen, and requires a laser and its scanning optical system, making it extremely complex and expensive, and is only used for special purposes. There wasn't.

Recently, multi-type liquid crystal panels such as TN and STN liquid crystals capable of displaying large volumes have appeared, and TPT active matrix type liquid crystal panels with excellent display quality have also been put into practical use. Many liquid crystal projection display devices have been announced.

These methods can be roughly divided into two types. One method is to use a single liquid crystal panel as shown in FIG. The liquid crystal panel 63 uses a black and white liquid crystal panel, an RGB color filter arrangement, or a Tacolor H crystal panel.
The light from the light source 61 is modulated by the liquid crystal panel 53, and the lens 5
This is a method of projecting images in step 2. Another method, as shown in FIG. 6, is a method using three panels 66 corresponding to RGB, in which the display of each pixel is optically superimposed to perform color display. The light from the white light source 61 is separated into three colors of RGB by dichroic mirrors 64a and 64b,
Liquid crystal panels 65a to 6 displayed according to display information of each color
After each light modulation with 5c, the dichroic mirror e
4c, e, and *d are combined and displayed in enlarged projection.

The former has the advantage of simplifying the optical system configuration, but in color display, each pixel consists of three RGB dots on a flat surface, resulting in coarse resolution and reduced brightness. There is. In particular, these problems remain even when displaying in black and white depending on the application, so there is the problem that the amount of displayed information is not sufficient, and in order to eliminate this problem, it is necessary to use a liquid crystal panel with an even larger capacity. occurs.

The latter can have sufficient resolution, but RG
Three LCD panels are required for color B, and at least four mirrors are required for spectral 2 synthesis, which makes the optical configuration a little complicated, and like the former, the brightness is not sufficient. The problem is that it is not.

Problems to be Solved by the Invention Liquid crystal display elements perform display using the optical rotation of light, that is, the effect that the polarization axis rotates while passing through the liquid crystal. The structure has polarizing plates whose polarizing axes are perpendicular to each other, and depending on the rotation angle of the polarizing axis of the light linearly polarized by the front polarizing plate,
The display indicates whether the light passes through the polarizing plate on the rear surface or not. In FIG. 7, 71a and 71b are polarizing plates, 72a and 72b are Nubesa, and 73 is a liquid crystal. Therefore, in principle, less than half of the light component is required to enter the inside of the liquid crystal panel and undergo the modulation operation of light transmission/blocking. Therefore, as shown in the previous two examples, the problem arises that the brightness is not sufficient.

In order to increase the brightness, it is sufficient to use a high-output light source, but considering miniaturization of equipment 2 heat generation, etc., these also have potential.

On the other hand, although the single panel system shown in FIG. 5 is good in terms of simplifying the optical system, it has the problem of lower resolution, especially in the case of color display. Although the three-panel system shown in Figure 6 can ensure resolution, it requires three sets of liquid crystal display elements and at least four dichroic mirrors, making the optical configuration complicated. are doing.

Therefore, it is an object of the present invention to provide a projection display device that has excellent display quality such as brightness and resolution, and can realize a simpler optical system.

Means for Solving the Problems In order to achieve the above-mentioned object of the present invention, two black and white liquid crystal display panels and a color liquid crystal display panel are used, and each of these display panels is provided with linearly polarized light of P polarized light and S polarized light separated by a polarization separator. a photosynthesizer for allowing one of the components to enter and further combining the light that has passed through the liquid crystal panel;
and an optical system consisting of a lens for enlarging and projecting images. The control circuit has the function of separating the color human input signal into a luminance signal and a hue signal, processing these signals, and controlling the display of each liquid crystal panel.

The light from the working light source is separated into two mutually orthogonal linearly polarized components, namely a P-polarized component and an S-polarized component, using a polarization separator.
One of these linearly polarized light components is incident on a black and white liquid crystal display panel having a polarizing plate with a polarization angle that allows modulation of light transmittance, and the remaining linearly polarized light component is converted into polarized light that can modulate light transmittance. The light enters a color liquid crystal display panel having angular polarizing plates, and the transmitted light from each liquid crystal display panel is combined by a light combiner. Since the luminance signal and hue signal of the color human input signal are applied to each liquid crystal display panel, the image synthesized by the light combiner is reproduced as a color image corresponding to the color human input signal. Note that a structure in which the light transmittance of a linearly polarized light component incident on each liquid crystal display panel can be modulated is one in which the polarization axis of the incident light is parallel to the polarization axis of the polarizing plate on the incident side of the liquid crystal display panel. In other words, the conditions are such that light can pass through, and the linearly polarized light that passes through the front polarizing plate is
When passing through the liquid crystal, the polarization axis undergoes a rotation determined by the voltage applied to the liquid crystal, and the angle of rotation is modulated depending on whether or not it passes through the polarizing plate on the rear surface of the liquid crystal display panel. In this way, each of the linearly polarized components is
This means that a single liquid crystal display panel can capture nearly 10%. In this way, by separating the incident light into two light components, making each of them incident on two liquid crystal display elements, and then combining the transmitted light, it is possible in principle to use all the incident light as projection light. The configuration is simple, the light utilization efficiency is high, and bright projection display is possible.

Embodiment FIG. 1 shows an embodiment of the present invention. Reference numeral 11 in the figure is a light source for projection, and a halogen, xenon, metal halide, or other lamp is used. The light from here is condenser lens 1
The light is collimated at 2a, enters the polarization splitter 14a, and is separated into light in two directions.

The polarization separator 14a is composed of a polarization beam splitter, and separates the light into P waves and S waves, which are linearly polarized components orthogonal to each other. The polarizing beam splitter in this example has a P polarization component of 10
It is configured to have 0% transmission and 100% reflection of the S-polarized light component. The P-polarized light component transmitted through the polarization separator 14a enters the liquid crystal display panel 13b, and the S-polarized light component reflected by the polarization separator 14a enters the liquid crystal display panel 13a. The liquid crystal display panel 13b is a black and white liquid crystal display panel, and the liquid crystal display panel 13a is a color liquid crystal display panel.

Here, the configuration of the polarizing plates of each liquid crystal display panel is as shown in FIG. 3. The light incident side polarizing plate 33& of the black and white panel 31 has a P polarizing axis, and the light incident side polarizing plate 34b of the color panel 32 has an S polarizing axis. Peel in parallel direction.

As a result, all the polarized light incident on each panel enters the inside of the panel and undergoes optical modulation. The polarizing plates 33b and 34a on the output side of each panel may be parallel or perpendicular to the polarization axis on the incident side, but in this example, the polarizing plates are configured with vertical axes, and the configuration is such that light passes through when the liquid crystal is OFF. There is. Therefore, the light that enters each liquid crystal display panel undergoes light modulation according to the displayed information and comes out from the liquid crystal display panel, but the light that comes out from the black and white panel 31 side is S-polarized, and the light that comes out from the color panel 32 side is S-polarized. It comes out as P-polarized light.

These lights are reflected by mirrors 15b and 15a as shown in FIG.
The light enters the compound word 14b via. The photosynthesizer 14b is S
It is composed of a polarized beam nuprisotater in which the polarized light component is reflected and the P-polarized light component is transmitted, and the lights from both are combined here. This light is enlarged and displayed on the screen via the lens 12b.

The above is the configuration of the optical system. Note that 16 is a control section of the liquid crystal display panel, and 17 is a display input signal.

The liquid crystal display panel and the composite image on the screen will be explained below. Liquid crystal display panels with various numbers of dots and dot pitches can be used, and the display quality will change accordingly, but these have limitations such as manufacturing technology and yield - hb, so there are currently only a few options available. There are limitations. Here, it is assumed that an available liquid crystal display panel with the smallest pitch is employed, and that both the monochrome panel 45a and the color panel 46b of the liquid crystal panel shown in FIG. 4 have the same resolution. That is, the color panel 46b is originally one pixel consisting of three RGB dots, but the actual pixel density is % of monochrome.

In the embodiment of the present invention, the display image input signal 17 is controlled by the color signal component (
The signal is separated into a luminance signal component (hereinafter referred to as C signal) and a luminance signal component (hereinafter referred to as Y[), and each signal is displayed on monochrome and color display panels. A block diagram of this control section 16 is shown in FIG. The display input signal 27 passes through the sync separator 21 and is separated into a Y signal and a C signal by a YC separation circuit 22. Each signal passes through AD converters 23a and 23b and enters liquid crystal panel control circuits 24a and 24b, where display control of the liquid crystal panel is performed. 25a and 25b are memories for display data.

As shown in FIG. 4, the color panel 45b
Displays in color. At this time, the black and white panel 45a controls the display in units of three dots corresponding to the pixels of the color panel in accordance with the Y signal. The color panel 46b has a pixel pitch of %, so the display pixels are coarse, but it can maintain the same resolution as the conventional single color panel method, and is brighter because the display light from the monochrome panel is superimposed. will be displayed.

Here, if the display input signal is black and white data, as shown in Figure 4 (
The black and white panel 45a in a) performs display according to the display information of the Y signal. At this time, if the color panel 45b is set to a light-blocking state for all pixels, the transmitted light image of the color panel 45a is displayed on the screen, and a high-density and bright display can be performed.

In this way, when viewed from a distance where the dots cannot be seen separately like on a normal direct-view color TV, a bright color display image can be obtained, although the color display is somewhat pale. In particular, when pressing the button for black and white display, the resolution is coarse and the display becomes dark when using only a normal color panel.
However, this method allows high-resolution display.

Effects of the Invention As is clear from the above description of the embodiments, the present invention separates incident light into two light components, makes each of them incident on two liquid crystal display elements, and then further converts the transmitted light into a base. Therefore, in principle, all the incident light can be used as projection light, making it possible to achieve bright projection display with high light utilization efficiency.

Furthermore, by using a liquid crystal display element capable of displaying black and white and color, bright display can be achieved without reducing the resolution during black and white display, and color display is also possible.

In this way, it is a projection display device that not only uses a simpler tank bottom than the conventional 3-panel system and can display higher resolution than the 1-panel system, but also has a brighter display than both, which is superior in both performance and price. can be realized.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a projection display device according to an embodiment of the present invention, Fig. 2 is a block diagram of a control circuit that controls the liquid crystal panel, and Fig. 3 is a sectional view showing the groove bottom of the liquid crystal panel. , FIG. 4 is a pixel configuration diagram of the liquid crystal panel, FIG. 5 is a configuration diagram of the first conventional projection display device, FIG. 6 is a configuration diagram of the second conventional projection display device, and FIG. 7 FIG. 2 is a sectional view showing the bottom of the liquid crystal panel for explaining the same. 11...Light source for projection, 13a...Color liquid crystal display panel, 13b...Black and white liquid crystal display panel, 14a...Polarization separator, 14b...・
...Photosynthesizer, 12b...Projection lens, 16
...Liquid crystal panel control section, 22...YC
Separation circuit, 24a, 24b...Liquid crystal panel control circuit.

Claims (1)

[Claims] a polarization separator that separates light from a light source into a first linearly polarized component and a second linearly polarized component that are orthogonal to each other; a black and white liquid crystal display element that modulates based on a luminance signal; a color liquid crystal display element that modulates the transmittance of the second linearly polarized light component based on a hue signal of the display input signal; and each of the liquid crystal displays. 1. A projection display device comprising a light combiner that combines transmitted light from the elements, and projects the light combined by the light combiner onto a screen via an optical lens.