JPH04177335A - Projection type liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve the effective utilization factor of light, and to obtain a projection type liquid crystal display device of bright screen by polarizing and converting the light from a light source, so as to irradiate all of the light on a liquid crystal display device as a polarized flux. CONSTITUTION:The light from a light source 1 is formed as a parallel light by a concave mirror 2 and a convex lens (condenser lens) 4, and a polarizing beam splitter 6 for irradiating the parallel light and for dividing it into P polarizing wave and S polarizing wave, is provided. A polarizing conversion means (polarizing optical system) 5 is provided, by which, of the divided polarized wave by the splitter 6, the P polarizing wave is reciprocated in a 1/4 wavelength plate 7, so as to change its phase, and is thus converted into S polarizing wave. The S polarizing wave converted and thus obtained by the means 5, and that divided by the splitter 6 are synthesized together, and the synthesized light is irradiated on a liquid crystal device 13. All the flux from the light source 1 can thus be irradiated on the liquid crystal device 13 as polarized flux, and the effective utilization factor of light can be improved to a doubled level, and the brightness of screen can be improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a projection type liquid crystal display device using a transmission type liquid crystal display element that receives polarized light waves from the back and projects an image from the front. More specifically, the present invention relates to such a projection type liquid crystal display device that makes it possible to improve the efficiency of using light from a light source.

[Conventional technology]

Conventional projection type liquid crystal display devices are disclosed, for example, in Japanese Unexamined Patent Application Publication No. 1986-62.
As described in Japanese Patent No. 125791, white light output from a single light source is converted into red, blue,
By splitting the light into the three primary colors of green, and making each of these three primary color lights incident on three liquid crystal panels, images corresponding to the three primary colors are displayed, and images corresponding to these three primary colors are synthesized using a guicro ink prism. A color image is obtained by this method, and this color image is enlarged and projected onto a screen using a single projection lens.

[Problem to be solved by the invention]

In the above conventional technology, the structure of each liquid crystal panel consists of a liquid crystal element optically sandwiched between two polarizing plates, and the light rays incident on the liquid crystal panel are originally P-polarized waves and S-polarized waves. Although it can be separated into waves, only the P-polarized wave or the S-polarized wave is emitted from the liquid crystal panel. That is, the amount of light transmitted through the liquid crystal panel is less than half of the amount of incident light, resulting in a problem that a considerable loss of light occurs.

Here, P-polarized light refers to linearly polarized light with a polarization plane parallel to the plane of incidence (the plane in which the electric vector oscillates), and S-polarized light refers to linearly polarized light whose plane of polarization is perpendicular to the plane of incidence. It refers to linearly polarized light with .

For example, conventionally, dyes (2
In this case, an element that transmits P-polarized light absorbs S-polarized light, resulting in light loss. It is.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to solve not only S-polarized waves (or P-polarized waves) but also P-polarized waves.
It is an object of the present invention to provide a projection type liquid crystal display device that can effectively utilize polarized light waves (or S-polarized light waves) to improve the light utilization efficiency and obtain a bright screen.

[Means to solve the problem]

In order to achieve the above object, the present invention converts light from a light source into almost parallel light using a concave mirror and a convex lens, and then polarizes the incident parallel light to separate it into linearly polarized P-polarized light waves and S-polarized light waves. Among the polarized waves separated by the beam splitter and the polarized beam splitter, P polarized waves (or S
polarization conversion means for changing the phase of the polarized light wave (or P polarized light wave) by reciprocating the polarized light wave within a quarter-wave plate; The S-polarized light wave (or P-polarized light wave) is combined with the S-polarized light wave (or P-polarized light wave) separated by the polarizing beam splitter, and the combined light is irradiated onto a liquid crystal display element.

[Effect]

According to the above configuration of the present invention, the polarizing beam splitter separates the light from the light source into linearly polarized light of P-polarized light and S-polarized light with almost no loss. Next, the luminous flux on one side is 1
/4 By reciprocating within the wavelength plate using a reflective film,
Converts it into a polarized wave in the same direction as the other. At this time, by sufficiently suppressing the transmission loss of the 1/4 wavelength plate and the reflection loss of the reflective film, it is possible to irradiate all the light flux from the light source to the liquid crystal display element as a polarized light flux, doubling the effective utilization rate of light. It can be improved almost. As a result, the brightness of the screen can be improved.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing a projection type liquid crystal display device as a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a light source, such as a white light source such as a metal halide lamp or a xenon lamp. 2 is a concave mirror, 3 is an infrared cut filter, 4 is a condenser lens, 5 is a polarization optical system including a polarization conversion means and a combining means, and in this embodiment, a polarization beam splitter 6 and 1 7 are used.
It consists of a /4 wavelength plate, a reflective film (8) formed on one side of the /4 wavelength plate (7) by means such as vapor deposition, a right angle prism (9), and a composite prism (10). 11-1
3 are liquid crystal display elements, which are composed of 11 polarizing plates, 12 transparent electrodes, and 13 liquid crystals (for example, TN liquid crystal). 14 is a projection lens, and I5 is a screen.

The operation of this embodiment will be described below with reference to FIGS. 1 and 2. Note that FIG. 2 is a partially enlarged view of the polarizing optical system 5 in FIG. 1.

In FIG. 1, light from a light source 1 and reflected by a concave mirror 2 passes through an infrared cut filter 3 that reflects heat rays and passes visible light, enters a condenser lens 4, and is emitted as a nearly parallel beam of light. The light then enters a polarizing beam splitter 6, which is a component of the polarizing optical system 5.

Next, the explanation will be continued using FIG. Light incident on the polarizing beam splitter 6! 16 is an undefined polarized light wave 17, which is separated by the polarization beam splitter 6 into an S polarized light wave 18 and a P polarized light wave 19.

Next, the S separated by the polarizing beam splitter 6
The polarized light wave has its path bent by a right-angle prism 9, and then enters a liquid crystal display element (comprising a liquid crystal 13 and transparent electrodes 5 and polarizing plates 11 arranged on both sides of the liquid crystal 13) through a synthesis prism 10.

Further, one P-polarized light wave 19 is transmitted to a quarter-wave plate 7 on which a reflective film 8 is formed by means such as vapor deposition on one side of the plate.
The P-polarized light beam 19 is incident on the P-polarized light beam 19, is reflected by the reflective film 8, and passes through the quarter-wave plate 7 again, thereby being converted into an S-polarized light wave 20, which is then incident on the polarization beam splitter 6.

Here, since the polarizing beam splitter 6 has a property of reflecting P polarized light waves and transmitting S polarized light waves, the S polarized light waves 2
0 passes through the polarizing beam splitter 6 as it is, and enters the liquid crystal display element at the combining prism 10.

Here, the combining prism 10 is configured to combine the emitted S-polarized light waves 18 and 20 so that they coincide on the surface of the liquid crystal 13, as shown in FIG.

Further, the image displayed on the surface of the liquid crystal 13 is enlarged by the projection lens 14 to obtain an enlarged real image on the screen 15.

As described above, conventionally only half of the light from the light source 1 was used, but according to this embodiment, almost all of it can be used effectively. rate will be significantly improved.

Note that, as shown in FIG. 1, in this embodiment, the liquid crystal 13
Polarizing plates 11 (in this embodiment, only S-polarized waves are selected and emitted) are provided on both sides of the combining prism 10.
The same effect can be obtained even if the side polarizing plate 11 is removed. When the polarizing plate 11 is provided on the side of the combining prism 10, the purity of the polarized light of the light emitted from the combining prism 10 and incident on the liquid crystal 13 is further improved, and the contrast performance can also be improved.

Further, as a driving circuit for a liquid crystal display element, there is a circuit as shown in the lower part of FIG. 1, for example. That is, video input from a laser disc, VTR, etc. is processed by the video chroma processing circuit 30 and input to the RGB output circuit 31. In the RGB output circuit 30, in order to AC drive the video signals corresponding to R, G, and B and the liquid crystal display element, the polarity is inverted every vertical period, and the transparent electrode 1 is outputted via the X driver 32.
Enter 2. The video chroma processing circuit 30, the RGB output circuit 3LX driver 32, and the Y driver 35 are synchronized by a synchronization processing circuit 33 and a controller 34.

Furthermore, as shown in FIG. 2, the polarizing optical system 5 in this embodiment has its various components (polarizing beam splitter 6,
a quarter-wave plate 7 with a reflective film 8 formed thereon, a right-angle prism 9,
and the composite prism 10) can be integrated with each other by optical adhesion, thereby creating a compact polarizing optical system 5.
can be realized.

FIG. 3 is a block diagram showing the main parts of a second embodiment of the present invention, and parts corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

A feature of this embodiment is that the number of components of the polarization optical system 5 can be reduced compared to the embodiment shown in FIG. That is, in FIG. 3, the S-polarized light beam that has passed through the polarizing beam splitter 6 and the right-angle prism 9 according to the polarization conversion principle shown in FIG. Instead of combining the S-polarized light wave 20 whose polarization has been converted by reciprocating through the quarter-wave plate 7, as shown in FIG.
A liquid crystal display element composed of a liquid crystal 13 and a liquid crystal 13 is configured so that the light is incident on each half, such as the upper half surface and the lower half surface (or the right half surface and the left half surface).

By doing so, the combining prism 10 shown in FIGS. 1 and 2 can be removed. In this embodiment, a filter 21 for absorbing light is provided in a bright area in order to balance the brightness in the left and right or up and down directions of the liquid crystal display element. This filter 21
Uniform brightness can be achieved by optimizing the absorption rate of light.

Further, in FIG. 3, the filter 21 is placed apart from the right angle prism 9, but if it is integrated with the right angle prism 9 by optical adhesion, the polarization optical system 5 can be further miniaturized. Furthermore, in FIG. 3, the projection lens 14 and screen 15 shown in FIG. 1 are not shown, but are of course mounted.

FIG. 4 is a block diagram showing the main parts of a third embodiment of the present invention, and parts corresponding to those in FIGS. 1 and 2 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

A feature of this embodiment is that the number of components of the polarization optical system 5 can be further reduced compared to the embodiments shown in FIGS. 1 and 3, which will be explained below.

In FIG. 4, a light ray 16 emitted from a light source 1 passes through an infrared cant filter 3 that reflects heat rays and passes visible light, enters a condenser lens 4, and is emitted as a substantially parallel light beam. The process up to this point is the same as the embodiment shown in FIGS. 1 and 2, and the emitted light is an undefined polarized light wave 17.

Next, in this embodiment, the components of the polarizing optical system 5 are
The light is incident on the four-wavelength plate 7. In this case, since the incident light beam is the undefined polarized light wave 17 as described above, the incident light beam enters the polarization beam splitter 6 as it is, and the S polarized light wave 18 and the P
The polarized light wave 19 is separated into a polarized light wave 19, and the P polarized light wave 19 is directly incident on a liquid crystal display element composed of a polarizing plate 11, a transparent electrode 12, and a liquid crystal 13. Here, the polarizing plate 11 is shown in FIGS.
The polarization characteristics are different from those shown in the figure, and only P-polarized waves are selected here.

One of the S-polarized waves 18 is reflected by a reflective film 8 formed on one side of the polarizing beam splitter 6, passes through the polarizing beam splitter 6 again, and enters the quarter-wave plate 7. As a result, the light beam 16 emitted from the quarter-wave plate 7 is converted from the S-polarized light wave 18 to a circularly polarized light wave 22.

Furthermore, by optimally designing the concave mirror 2 located after the light source 1, the light ray 16 emitted from the quarter-wave plate 7 is
The light passes through the condenser lens 4 and the infrared cut filter 3, is reflected by the concave mirror 2, becomes as if it were emitted from the light source 1 again, returns to the 1/4 wavelength plate 7, and is reflected by the 1/4 wavelength plate 7 again. is incident on the Then, the emitted light ray I6 is converted from a circularly polarized light wave 22 to a P polarized light wave 23,
The light is incident on the liquid crystal display element by the polarizing beam splitter 6.

In FIG. 3, the paths of the light rays 16 are shown as a plurality of staggered lines, but this is to make the explanation easier to understand, and of course the light rays 16 travel back and forth on the tree line.

As described above, according to this embodiment, the number of components of the polarization optical system 5 can be reduced compared to the embodiments shown in FIGS. 1 and 3, and the same effects can be obtained. Further, similar to FIG. 3, illustration of the projection lens 14 and screen 15 shown in FIG. 1 is omitted.

All of the embodiments described above are examples applied when the liquid crystal display element has a single-layer configuration, but the so-called three primary colors (R, G,
, B) can also be applied to a method using three liquid crystal display elements. Its configuration is shown in Section 5.

FIG. 5 is a schematic configuration diagram showing a fourth embodiment of the present invention using the polarizing optical system 5 shown in FIG.

In FIG. 5, parts that are the same as those in the embodiment described above are designated by the same reference numerals, and detailed explanation thereof will be omitted. The light emitted from the light source 1 is collimated by a condenser lens 4 into a substantially parallel beam, and then enters a polarization optical system 5 whose polarization conversion principle is shown in FIG.

The light beam emitted from the polarizing optical system 5 is reflected by a B (blue) reflecting dichroic mirror 25 arranged at an angle of 45 degrees with respect to the optical axis of the light beam, and R (red) is reflected.
and G (green) are transmitted.

The reflected B light beam is bent by the total reflection mirror 27 and passes through the polarizing plate 11, the transparent electrode 12, and the liquid crystal 13.
The light is incident on a liquid crystal display element composed of. On the other hand, the R and G rays transmitted through the B reflection dichroic mirror 25 are
G is reflected by the G reflection dichroic ink mirror 26 arranged at an angle of 45'' with respect to the optical axis of the light beam, and R is transmitted.

The reflected G ray enters the liquid crystal display element as it is.

On the other hand, the R light beam transmitted through the G reflection dichroic ink mirror 26 has its course bent by the total reflection mirror 27 and enters the liquid crystal display element.

Furthermore, R displayed on the liquid crystal 13 surface of each liquid crystal display element,
The images corresponding to B and G, respectively, have a B reflective surface 29 and an R reflective surface 36, and the reflective surfaces are oriented 4 times relative to the optical axis.
Each image is combined by a dichroic ink prism 28 configured to form an angle of 5°, and this combined image is enlarged by a projection lens 14 to obtain an enlarged real image on a screen 15.

〔Effect of the invention〕

According to the present invention, by converting the polarization of the light from the light source, where more than half of the light was conventionally absorbed by a polarizing plate, it is possible to irradiate the liquid crystal display element entirely as a polarized light beam, making effective use of light. As a result, a projection type liquid crystal display device with a bright screen can be realized.

Further, according to the present invention, the polarizing optical system can be integrated into an integrated configuration, and the size can be reduced accordingly.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a projection type liquid crystal display device as a first embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. 1,
FIG. 3 is a configuration diagram showing the main parts of the second embodiment of the present invention,
FIG. 4 is a configuration diagram showing the main parts of the third embodiment of the present invention,
FIG. 5 is a schematic configuration diagram showing a fourth embodiment of the present invention. Explanation of symbols 1... Light source, 2... Concave mirror, 3... Infrared cut filter, 4... Condenser lens, 5... Polarizing optical system, 6... Polarizing beam splitter, 7...・1/4 wavelength plate, 8...Reflection film, 9...Right angle prism, 10.
... Synthesis prism, 11 ... Polarizing plate, 12 ... Transparent electrode, 13 ... Liquid crystal, 14 ... Projection lens, 15.
...Screen, 16...Light ray, 17...Undefined polarized light wave, 18...S polarized light wave, 19...P polarized light wave, 20.
... S polarized light wave, 21... Filter, 22... Circularly polarized light wave, 23... P polarized light wave, 25... B reflective dichroic mirror, 26... G reflective dichroic ink mirror,
27... Total reflection mirror, 28... Duckroitzk prism, 29... B reflective surface, 36... R reflective surface, 3
0... Video chroma processing circuit, 31... RGB output circuit, 32... X driver, 33... Synchronization processing circuit, 34... Controller, 35... Y driver. Agent Patent Attorney Akira Namiki Tenshin 1 Illustrations 2 Illustrations 11!3 Illustrations 4 Illustrations

Claims (1)

[Claims] 1. In a projection type liquid crystal display device using a transmissive type liquid crystal display element that receives polarized waves from the back and projects an image from the front, the light source (1) outputs undefined polarized waves; a polarizing beam splitter (6) that separates the input undefined polarized light wave from the light source into S-polarized light wave and P-polarized light wave and outputs the same; and a quarter-wave plate that separates the separated P-polarized light wave (or S-polarized light wave). polarization conversion means (7, 8) that converts the S-polarized light wave (or P-polarized light wave) into an S-polarized light wave (or P-polarized light wave) by transmitting the S-polarized light wave (7) back and forth; and Polarized wave combining means (9, 10) for combining the S-polarized light wave (or P-polarized light wave) converted by the polarization conversion means and making it incident on the back surface of the liquid crystal display element. Characteristic projection type liquid crystal display device. 2. In the projection type liquid crystal display device according to claim 1, the polarized light wave combining means includes a right-angle prism (9) that bends incident light at right angles and outputs the same, and a right-angle prism (9) that bends incident light at right angles and outputs the same; Synthesizing prism (1
0), and the polarizing beam splitter (6
), the quarter wavelength plate (7), and the right angle prism (
9) and the synthetic prism (10) are integrated by pasting their required surfaces together, and the light incident on the polarizing beam splitter (6) is integrated into the synthetic prism (10).
A projection type liquid crystal display device characterized in that it does not leak outside until it is output. 3. In a projection type liquid crystal display device using a transmissive type liquid crystal display element that receives polarized light waves from the back and projects an image from the front, there is a light source (1) that outputs undefined polarized light waves, and undefined polarized light from the light source. A polarizing beam splitter (6) that separates an incident wave into S-polarized light wave and P-polarized light wave and outputs the same, and the separated P-polarized light wave (or S-polarized light wave) is transmitted round-trip through a quarter-wave plate (7). polarization converting means (7, 8) for converting the S-polarized light wave (or P-polarized light wave) into an S-polarized light wave (or P-polarized light wave) by The first beam is incident on the half surface of the back surface.
a second optical means for causing the S-polarized light wave (or P-polarized light wave) converted by the polarization conversion means to be incident on the remaining opposite surface of the entire back surface of the liquid crystal display element;
A projection type liquid crystal display device comprising: 4. The projection type liquid crystal display device according to claim 1, 2 or 3, wherein the polarization conversion means includes the quarter wavelength plate (7) having a reflective film (8) added to its light exit surface. The reflecting film (8)
1. A projection type liquid crystal display device comprising a polarization converting means that performs polarization conversion by reflecting the light and emitting it from the incident surface. 5. The projection type liquid crystal display device according to claim 1, 2 or 3, wherein the polarization conversion means comprises a concave mirror (2) provided behind the quarter wavelength plate (7) and the light source (1). including, said 1/
It consists of polarization conversion means that converts the polarized light emitted from the output surface of the four-wave plate (7) by reflecting it on the concave mirror (2) and making it enter the quarter-wave plate (7) again from the output surface. A projection type liquid crystal display device characterized by: