JPH01201693A - Projection type liquid crystal display device - Google Patents

Abstract

PURPOSE:To brightly display an image of a large screen by providing a polarization beam splitter for synthesizing a linearly polarized light of P polarization and a linearly polarized light of S polarization. CONSTITUTION:A light source light is separated into two luminous fluxes whose polarization directions are orthogonal to each other by a polarization beam splitter 6, and the respective luminous fluxes are brought to modulation based on the same image signal by liquid crystal panels 11, 12, and thereafter, synthesized again by a polarization beam splitter 13, superposed on a screen 16 by a projection lens 15 and enlarged and projected. Accordingly, comparing with that which has used a conventional polarizing plate, a loss of light and generation of heat caused by an absorption do not occur. In such a way, the light utilization efficiency of the light source light is extremely high and a bright displace screen can be obtained, and also, it does not occur that a liquid crystal panel cannot execute a normal operation due to generated heat.

Description

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

[Conventional technology]

A projection type liquid crystal display device enlarges and projects the displayed image on a liquid crystal panel onto a screen, and as shown in FIG. Liquid crystal panel 34 that forms images using (twisted nematic) type liquid crystal
, and a projection lens 35 for enlarging and projecting the image displayed on the liquid crystal panel 34 onto a screen 36.

In other words, this projection type liquid crystal display device displays television images, character images of personal computers, word processors, etc. on a small liquid crystal panel, and enlarges and projects the displayed image onto the screen in an arbitrary size. images can be easily obtained, and when used as a video projector or an electronic OHP (overhead projector), the device can be made extremely compact and lightweight.

[Problem to be solved by the invention]

However, since conventional projection type liquid crystal display devices use a TN type liquid M panel, more than 60% of the luminous flux is lost due to the polarizing plate that converts the irregularly polarized light from the light source into linearly polarized light. It ends up. Therefore, when the image is enlarged and projected onto the screen, the screen becomes dark, and the lighting in the room must be dimmed, which is an inconvenience.

In addition, increasing the brightness of the light source to obtain a bright display screen not only increases power consumption, but also causes the liquid crystal panel to malfunction due to the heat generated by the absorption of light by the polarizing plate, and the polarizing plate to deteriorate. It will happen.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a projection type liquid crystal display device that can brightly display images on a large screen.

[Means to solve the problem]

The projection type liquid crystal display device of the present invention includes a light source, an il polarization beam splitter that separates undefined polarized light from the light source into P-polarized linearly polarized light and S-polarized linearly polarized light, and converts the P-polarized light into an image signal. a first liquid crystal panel that modulates based on the S
a second liquid crystal panel that modulates the linearly polarized light based on the same image signal; a second polarizing beam splitter that combines the linearly polarized P polarized light and the linearly polarized S polarized light; It is characterized by being composed of a projection lens.

[Effect]

In other words, the projection type liquid crystal display device of the present invention separates the light source light into two beams with orthogonal polarization directions using a polarizing beam splitter, and modulates each beam based on the same image signal on the liquid crystal panel. Since the images are combined using a polarizing beam splitter and then enlarged and projected onto a screen using a projection lens, there is no loss of light due to absorption or generation of heat compared to conventional polarizing plates. A bright display screen with extremely high light utilization efficiency of the light source can be obtained, and the liquid crystal panel will not malfunction due to the heat generated.

〔Example〕

FIG. 1 is a diagram showing a first embodiment of the present invention.

In Figure 1, light 1 is a high-brightness white light source such as a nitrogen lamp or a xenon lamp, and the light flux emitted from the light source is passed through a mirror 2 and a condenser lens 3, which are processed into an ellipsoid or paraboloid. This becomes a parallel beam of light 4. filter 5
is a bandpass filter that only transmits visible light,
Interference filters made of multilayer thin films that reflect or absorb ultraviolet and infrared rays and heat-insulating glass were used.

The parallel light beam 4 is undefined polarized light, and is separated into two linearly polarized lights, a P-polarized light 7 and an S-polarized light 8, by a polarizing beam splitter 6. The polarizing beam splitter 6 is made by coating one of the hypotenuses of two right-angled prisms with a semi-transparent film made of a metal film or a multilayer film of a power-visiting body, and joining the two sides. The extinction ratio is 20d.
It was B or higher. In addition, the light entrance/exit surface is coated with an antireflection film. P-polarized light 7 and S-polarized light 8 enter liquid crystal panels 11 and 12 via mirrors 9 and 10. The mirrors 9 and 10 were M surface mirrors in which M was vapor-deposited on the glass surface, or multilayer reflective mirrors in which the reflectance was increased by coating a multilayer film of 5iOz or Ti1t@. LCD panel 9
．． 10 is a TN type liquid crystal cell, and the driving method is simple.
Either an IJ type or an active matrix type may be used. However, the alignment direction of the liquid crystal must match the linearly polarized light obtained by the polarizing beam splitter 6, which corresponds to a polarizer, and the liquid crystal panel 11 modulates the P-polarized light 7, and the liquid crystal panel 12 modulates the S-polarized light 8. You have to configure it so that you can get it. Furthermore, since the liquid crystal panels 11 and 12 are mirror images of the bonding surface of the polarizing beam splitter 13 when viewed from above the screen, it is necessary to make the image format bilaterally symmetrical, which may also be achieved by a signal system. However, it may also be realized by turning one side of the liquid crystal panel over. The P-polarized light 7 and the S-polarized light 8Fi are modulated based on the same image signal by liquid crystal panels 11 and 12, respectively, and enter a polarizing beam splitter, which is an analyzer. An antireflection film was applied to the light input/output surfaces of the liquid crystal panels 11 and 12, and the polarizing beam splitter 13 had the same characteristics as the polarizing beam splitter 6. In addition to acting as an analyzer, the polarizing beam splitter 13 also serves as a P
Combined light 1 also has the role of combining polarized light 7 and S-polarized light 8.
Get 4.

That is, the polarization direction of the P-polarized light 7 is rotated by 90 degrees by the liquid crystal panel 11, and the polarized beam splitter 13 changes it into S-polarized light and reflects it toward the projection lens 15. On the other hand, the polarization direction of the S-polarized light 8 is similarly rotated by 90 degrees by the liquid crystal panel 12, and the polarization direction of the S-polarized light 8 is rotated by 90 degrees by the liquid crystal panel 12. The image formed on the liquid crystal panel 11, 12 is enlarged and projected onto the screen 16,
A bright large screen image can be projected by adjusting the position of the liquid crystal panel 11.12 so that each pixel of the liquid crystal panel 11.12 is projected at the same position. Here, the liquid crystal panel 11.
The pixel to which a voltage is applied at 12 becomes a black image on the screen, but if a projection lens is provided at the position 15', it is also possible to obtain an image inverted from a negative to positive.

As described above, the projection type liquid crystal display device of the present invention has no part in the optical path from the light source 1 to the screen 16 that significantly absorbs and loses visible light used for projection display, so it can prevent heat generation and A bright large screen image can be projected onto the screen 16.

In the above explanation, a black and white liquid crystal panel was used, but color display can also be achieved if the liquid crystal panel has a built-in color filter. In this case, a dichroic ink filter made of a multilayer thin film is preferable as it does not absorb light, but even the commonly used dye or pigment type color filters are inferior to conventional ones in terms of brightness and prevention of heat generation. It is extremely effective.

FIG. 2 is a diagram showing a second embodiment of the present invention.

In this embodiment, compared to the first embodiment, optical blocks 17 and 18 are provided in the optical path between the polarizing beam splitters 6 and 13.
．． The difference is that 19 and 20 are arranged.

The optical blocks 17, 18, 19, and 20 are made of polished optical glass such as BK7, and the joint surfaces with the polarizing beam splitter 6.13 and the liquid crystal panel 11.12 are bonded to match the refractive index. . Therefore, no loss due to reflection occurs at the input/output end face of each component. Further, the oblique sides of the optical blocks 17 and 18 satisfy the total reflection condition, and have a 24-fold path configuration with low loss. Furthermore, when displaying images formed by the liquid crystal panels 11.12 on the screen 16 in an overlapping manner, it is necessary to adjust the position of the liquid crystal panels 11.12, but in this embodiment, the positions are adjusted once first. The structure is such that it is possible to prevent positional displacement over time caused by vibration or thermal factors. In addition, the heat generated when color filters are built into the liquid crystal panel can be cooled down more efficiently because the heat conductivity is much better than when the liquid crystal panel is placed in the air. .

FIG. 3 shows a third embodiment of the invention. In this embodiment, the liquid crystal panels 22 and 23 are of reflective type, and the polarizing beam splitter 21 serves as a polarizer, an analyzer, and separation and combination of the projected light flux, making the device very compact. realizable.

In addition, as in the second embodiment, a polarizing beam splitter 21
and liquid crystal panels 22.23 are respectively optical blocks 24.
Since the refractive index is completely matched with 25 and bonded, loss due to reflection, prevention of ghost images, alignment, and cooling efficiency are good. Here, the optical blocks 24 and 25 may be formed integrally with the polarizing beam splitter 21.

〔Effect of the invention〕

As explained above, 1. According to the projection type liquid crystal display device of the present invention, there is no loss of light due to absorption or generation of heat compared to a device using a conventional polarizing plate, and the light utilization efficiency of the light source is extremely high. It is small, provides an extremely bright display screen, and does not cause the LCD panel to malfunction due to the heat generated.
A lightweight projection type liquid crystal display device could be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment of the invention, FIG. 2 is a diagram showing a second embodiment of the invention, FIG. 3 is a diagram showing a third embodiment of the invention, and FIG. 4 is a diagram showing a third embodiment of the invention. The figure shows a conventional projection type liquid crystal display device. 1... light source, 2... mirror, 3...
... Condenser lens, 4 ... Parallel light beam, 5
...Filter, 6゜13...Polarizing beam splitter, 7...P polarized light, 8...
...S polarized light, 9,10...Mirror, 11,1
2...Liquid crystal panel, 14...Synthetic light,
15.15'・River...Projection lens, 16...Screen. Agent Patent Attorney Susumu Uchihara

Claims (1)

[Claims] a first polarizing beam splitter that separates the undefined polarized light from the light source into P-polarized linearly polarized light and S-polarized linearly polarized light; and a first polarized beam splitter that modulates the P-polarized linearly polarized light based on an image signal. a second liquid crystal panel for modulating the S-polarized linearly polarized light based on the same image signal; and a second liquid crystal panel for combining the P-polarized linearly polarized light and the S-polarized linearly polarized light. 1. A projection type liquid crystal display device comprising a polarizing beam splitter (2) and a projection lens.