JPH0317692A - Color display device - Google Patents

Abstract

PURPOSE:To increase the contrast of a transmitted picture on a screen and to obtain a sharp picture by using a scattering type liquid crystal mask for an optical system. CONSTITUTION:Each monochromatic light of blue, green, and red, which is generated by corresponding laser generators 1a, 1b, and 1c, respectively, is adjusted in terms of projection size by corresponding beam expanders 2a, 2b, and 2c, respectively, and is projected onto the corresponding scattering type liquid crystal masks 3a, 3b, and 3c, respectively. The three color lights, each of which is transmitted through an image element positioning at the same coordinate in the corresponding scattering type liquid crystal masks 3a, 3b, and 3c, respectively, are synthesized into one light by semitransmission type reflecting mirrors 5a, 5b, and 5c; the light is transmitted through a projecting lens 4, and projected at one point on the screen 7. As for the scattering type liquid crystal masks 3a, 3b, and 3c, their image element is turned on/off by a liquid crystal controller 8, therefore the contrast of a picture transmitted through it is increased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a color display device that can be used for conference display devices, advertisements, promotions, etc., and particularly relates to a color display device using a scattering type liquid crystal mask. It is.

[Conventional technology]

As a conventional technology, as shown in Fig. 2, a light valve a using a hybrid field effect (HFE) mode is used.
1, a2, and a3 as blue, green, and red CRTs b, , b
A color TV projector is provided on the front side of 2 and b3. c,,c2,c3 are CRTb,,b of each color
This is a dichroic reflecting mirror provided corresponding to 2 and b3. That is, C1 transmits blue, C2 reflects green, and C3
is a dichroic reflector that transmits red light. Also, d is a xenon lamp, e is a UV filter, and f is an IR filter.

Furthermore, g is a polarizing semi-transparent film, and light from this polarizing semi-transparent film g is projected onto a screen i via a projection lens h.

The light valve using the above HFE mode is in the dark state (O
In the FF state), the 45° twisted nemadec effect is used, and in the bright state (ON state), the birefringence effect is used. And 4 using biphenyl liquid crystal as the liquid crystal layer.
A 5° twisted liquid crystal layer is used. Twisted nematic should not transmit any light in the OFF state in a crossed polarizer arrangement, but when the liquid crystal layer thickness becomes thinner than about 12 m+s, the incident light length λ and layer thickness d will change even in the OFF state due to residual birefringence. It shows light transmission characteristics that depend on .

[Problem to be solved by the invention]

From the above, the above color TV projector is transparent,
The contrast of opaque areas decreases, making it difficult to obtain clear images.

In other words, since a polarizing plate is used, if the birefringence of the liquid crystal is Δn, the light transmission characteristic in this OFF state is Cos (2π
It is known from analysis that it has a zero point when Δnd/λ)-1. Therefore, a certain wavelength λ. liquid crystal layer thickness d
Unless Δn @ d/λo = K (here, K-fi number) is selected, the contrast between transmission and non-transmission will deteriorate due to the light transmission characteristics in the OFF state.

The present invention has been developed in consideration of the above points, so that the transmitted image on the screen has a high contrast and is displayed clearly, the optical system is simple, the power loss of light is small, the resolution of the image is improved, and color shift is improved. It is an object of the present invention to provide a color display device that can obtain a clear image without any blemishes, and can display a variety of colors by controlling the transmittance of the liquid crystal.

[Means to solve the problem]

In order to achieve the above object, a color display device according to the present invention has laser oscillators that emit monochromatic laser beams of blue, green, and red arranged in parallel, and a beam in the optical path of each laser oscillator. An expander and a scattering liquid crystal mask are interposed, and on the transmission side of each scattering liquid crystal mask, a light combining means such as a semi-transmissive reflector that combines each transmitted light into one, and this combined light is projected. The structure is equipped with a projection lens.

[For production]

Laser light of each color emitted from each laser oscillator is expanded by a beam expander into light that matches the size of the scattering type liquid crystal mask.

The scattering type liquid crystal mask is a crystal controller, and the pixels of this are O.
It is set to be turned off.

The laser beams that have passed through each scattering type liquid crystal mask are combined into one beam by a semi-transmissive reflecting mirror, and then enter the projection lens.

〔Example〕

An embodiment of the present invention will be described based on FIG.

In the figure, 1a is a blue laser oscillator that emits blue laser light, 1b is a green laser oscillator that emits green laser light,
lc is a red laser oscillator that emits red laser light, and these are arranged in parallel, with beam expanders 2a, 2b, 2c and a scattering liquid crystal mask 3a in each optical path.
, 3b, 3c, each scattering type liquid crystal mask 3a, 3b
, 3c, there is a transflective mirror 5a. 5b and 5c are arranged. 6 is an aperture, 7 is a screen, and 8 is a controller.

The scattering type liquid crystal masks 3a, 3b, and 3c are configured so that the transmittance of light can be changed by changing the applied voltage from the liquid crystal controller 8.

In the above configuration, laser oscillators 1a, 1b for each color,
The blue, green, and red monochromatic lights oscillated from the lc have their projection sizes adjusted by beam expanders 2a, 2b, and 2C, and are projected onto each of the scattering liquid crystal masks 3a, 3b, and 3c. The pixels of each of the scattering type liquid crystal masks 3a, 3b, and 3c are turned on and off by the applied voltage from the liquid crystal controller 8, and transmit a predetermined image at the same coordinates. The three colors of light transmitted through the pixels at the same coordinates in each scattering crystal mask 3a, 3b, 3c are
The beams are combined into one beam at c, pass through the projection lens 4, and are projected onto a single point on the screen 7.

In the above action, the scattering type liquid crystal masks 3a, 3b, 3c
This pixel is turned on and off by the liquid crystal controller 8.
The contrast of the image transmitted through it is high.

The transmittance of the image at this time is also controlled by changing the voltage applied to the liquid crystal.

〔Effect of the invention〕

According to the present invention, by using a scattering type liquid crystal mask in the optical system, the transmitted image on the screen has high contrast and appears clearly. Furthermore, since the optical system does not require a polarizing plate like in the past, the optical system is simplified, the power loss of light is reduced, and the resolution of images is improved. Furthermore, according to the present invention, since three colors of laser beams can be combined on the screen, a clear image without color shift can be produced. Furthermore, by changing the voltage applied to the liquid crystal, the transmittance of the liquid crystal can be controlled, thereby making it possible to display a variety of colors.

[Brief explanation of the drawing]

FIG. 1 is a schematic structural explanatory diagram showing an embodiment of the present invention, and FIG. 2 is a general structural explanatory diagram showing a conventional example. la, 1b, and lc are laser oscillators; 2a, 2b, and 2c are beam expanders; 3a, 3b, and 3c are scattering type liquid crystal masks; 4 is a projection lens; and 5a, 5b, and 5c are transflective mirrors.

Claims (1)

[Claims] Laser oscillators 1a, 1b, and 1c that emit monochromatic laser beams of blue, green, and red are arranged in parallel, and beam expanders 2a, 2b, and 2c are provided in the optical path of each laser oscillator 1a, 1b, and 1c. , scattering type liquid crystal masks 3a, 3
b, 3c, and each scattering type liquid crystal mask 3a.
, 3b, 3c are provided with light combining means such as transflective mirrors 5a, 5b, 5c for combining each transmitted light into one, and a projection lens 4 for projecting the combined light. color display device.