JPH03208013A - Polarized illumination system for LCD video projector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal video projector that projects a light image modulated by a liquid crystal plate through a projection lens, and particularly to its illumination system.

[Conventional technology]

Since liquid crystal projectors are smaller in device size than CRT video projectors, their uses are expanding.

FIG. 7 is a diagram showing the configuration of a conventional three-plate, three-lens type liquid crystal video projector in which dedicated liquid crystal plates and projection lenses are provided for each of RGB images.

In Figure 7, 76, 77. 78 are B, G, R respectively
71 is a dichroic mirror that reflects blue light, 72 is a tichroic mirror that reflects light of wavelengths below green, and 73 is a dichroic mirror that reflects light of wavelengths below red. The white light from the light source 79 passes through these dichroic mirrors 71. 72. 73, the colors are separated into B, G, and R light, respectively, and the liquid crystal plates 76 to 73
78 respectively. Each image light transmitted through each liquid crystal plate is transmitted through three lenses 74 provided for each image light.
It was configured to be projected onto a screen (not shown) at the same time.

FIG. 8 is a diagram showing the configuration of a conventional example of a liquid crystal video projector using a cross dichroic prism. White light from a light source 812 is parallelized by a reflector 811, separated into colors by three dichroic mirrors 807, 806, and 805 that reflect each color of B, G, and R.
, G, and R, each liquid crystal panel 801. 80
2, 803 is illuminated. And these LCD panels 8
Images from 01, 802, 803 are reflected by the reflecting mirror 80
8, 809, and are combined in a cross dichroic prism 810, and then the projection optical system 80
4 to be projected onto a screen (not shown).

Since the liquid crystal panel has polarization characteristics, the only effective illumination light to the liquid crystal panel is that along the polarizer of the liquid crystal panel. In this case, the light that is not used as illumination light is absorbed by the liquid crystal plate and converted into heat. In the liquid crystal video projectors shown in FIGS. 7 and 8, simply color-separated white light is used as illumination light.
There is a drawback that the utilization efficiency of each illumination light is less than %.

Figure 9 shows the method of Japanese Patent Application Laid-open No. 63, in order to improve the above-mentioned drawbacks.
It is a diagram showing the configuration of a polarized illumination system proposed in No.-182987.

What is shown in Figure 9 corresponds to each color to be separated.
Two beam splitters and a TN liquid crystal layer each having wavelength dependence are provided. The TN liquid crystal layer is for rotating the polarization plane of transmitted light by 90 degrees, and is provided between the two beam splitters. The white light from the light source 91, which has been made into a parallel beam by the condenser lens 92, is first irradiated onto the polarizing beam splitter 93a.

Only the red S-polarized light component is reflected by this polarized beam splitter 93a, which becomes illumination light for the R liquid crystal plate 96. At this time, the red P transmitted through the beam splitter 93a
The polarization plane of the polarized light component is rotated by 90 degrees in the TNi crystal layer 13c and converted into S-polarized light, and then reflected by the polarization beam splitter 93b to become illumination light for the same liquid crystal plate 95. All color light other than red passes through these and then reaches the polarized illumination system for green. For this green color and the next blue color, each illumination color light consisting only of S-polarized light can be obtained as in the case of this red color. Therefore, according to this polarized illumination system,
It not only separates the light source light into colors, but also aligns the plane of polarization (
S-polarized light), the light utilization rate improved.

[Problem to be solved by the invention]

Among the conventional liquid crystal video projectors mentioned above, in the ones shown in FIGS. 7 and 8, the planes of polarization are not aligned, so the light utilization rate of the illumination light becomes less than %, and the temperature of the liquid crystal plate decreases. The disadvantage is that it increases the In addition, although the light utilization efficiency is improved in the case shown in FIG. 9, the T
Since illumination light is not irradiated from the N liquid crystal layer toward each liquid crystal plate, there is a drawback that a linear dark area is generated in the center of the liquid crystal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal video projector that can align the polarization directions of illumination light, improve utilization efficiency, and uniformly illuminate each liquid crystal plate.

[Means to solve the problem]

The polarized illumination system of the liquid crystal video projector of the present invention is provided for each of the three transmissive liquid crystal plates that respectively form R-G-B images, and the liquid crystal video projector illuminates each liquid crystal plate to form an image. In this illumination system, each illumination system has a polarizing beam splitter into which the illumination light emitted from the light source is incident, and a reflecting means that reflects the light that has passed through the polarizing beam splitter. Each of the means is arranged to reflect incident light toward the liquid crystal plate, and a λ/2 plate is provided between the liquid crystal plate and an end surface from which one of the reflected light is emitted. [Operation] Of the illumination light, the S-polarized component is reflected toward the liquid crystal plate by the polarizing beam splitter. Further, the P-polarized light component transmitted through the polarizing beam splitter is reflected toward the liquid crystal plate by a reflecting means adjacent to the polarizing beam splitter. In this way, the polarization components of the respective reflected lights from the polarizing beam splitter and the reflecting means are different, but there is a λ/2
Since the plate is provided, the light that illuminates the liquid crystal plate is either S-polarized light or P-polarized light.

〔Example〕

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

In this embodiment, an optical system that separates white light into R, G, and B components and irradiates them onto a liquid crystal plate is composed of a dichroic mirror, a polarizing beam splitter, and a λ/2 plate, and the illumination light to each liquid crystal plate is has only a P-polarized component.

The dichroic mirror 1, polarizing beam splitter 5, λ/2 plate 8, and liquid crystal plate 18 in FIG. 1 are provided for the B component (blue light). Further, for the G component (green light), a dichroic mirror 2, a polarizing beam splitter 6, a λ/2 plate 9, and a liquid crystal plate 17 are provided, and for the R component (red light), a dichroic mirror 3, A polarizing beam splitter 7, a λ/2 plate 10, and a liquid crystal plate I6 are provided.

Each of the above-mentioned optical systems is for color-separating the light emitted from the light source 11 arranged on the right side of the drawing, and the optical systems for the B component, G component, and R component are arranged in the order of the traveling direction of the emitted light. .

Each dichroic mirror configuring each optical system 1.2.3
and each polarizing beam splitter 5, 6.7, each polarizing beam splitter 5, 6.7 is on the incident side, and each reflected light is transmitted to each liquid crystal plate 18, 17. They are arranged next to each other so as to irradiate 16. Additionally, λ/2 plates 8, 9. are provided at the end faces of each polarizing beam splitter 5, 6.7 from which the reflected light is emitted. 10 are provided respectively.

Figure 2(a). (b). (c) is a diagram showing the wavelength dependence of transmitted light of each polarizing beam splitter 5, 6.7 in FIG. 1, respectively. In each figure, the broken line indicates the P-polarized light component, and the solid line indicates the S-polarized light component. As shown in FIG. 2(a), only blue S-polarized light (approximately 500r+II+ or less) is reflected in the polarizing beam splitter 5, and the others are transmitted.As shown in FIG. 2(b), In the polarizing beam splitter 6, only S-polarized light of green light or less (approximately 600 nm or less) is reflected, and the others are transmitted.As shown in FIG. Only S-polarized light in the entire visible light range (approximately 680 nm or less) is reflected, and the others are transmitted.Each polarization beam splitter 5
, 6.7, each dichroic mirror 1.2.
3 have similar reflection characteristics, although they are not related to the polarization state, and the S-polarized light component and the P-polarized light component in the same wavelength range are respectively reflected in the adjacent polarizing beam splitter and dichroic mirror. .

Next, the operation of this embodiment will be explained.

The white light emitted from the light source l1 is made into parallel light by a condenser lens 12 provided between the light source l1 and the polarizing beam splitter 5, and then enters the polarizing beam splitter 5. With this polarizing beam splitter 5,
As described above, only the blue S-polarized light is reflected and enters the λ/2 plate 8. At this time, the polarization plane of the light is rotated by 90 degrees by the λ/2 plate 8 to become blue P-polarized light, which becomes illumination light for the B-light liquid crystal plate 18. Also, of the light transmitted through this polarizing beam splitter 5, the blue P-polarized light is reflected by the adjacent dichroic mirror 1 (blue reflection) and becomes illumination light for the liquid crystal plate 18 for B light as well. .

Therefore, the polarizing beam splitter 5 and the λ/2 plate 8
All of the blue light of the white light from the light source is unified into P-polarized light by the dichroic mirror 1 and becomes illumination light with a uniform plane of polarization (P-polarized light) for the liquid crystal plate 18 for B light.

In exactly the same way, the green light from the light beam transmitted through the dichroic mirror 1 is unified into P-polarized light by the polarizing beam splitter 6, the λ/2 plate 9, and the dichroic mirror 2.
This becomes illumination light for the liquid crystal plate 17 for G light. Furthermore, in the same way, from the light beam transmitted through the dichroic mirror 2, the polarizing beam splitter 7, the λ/2 plate 10, the dichroic mirror 3
The red light is unified into P polarized light, and the liquid crystal plate 18 for R light is
It becomes the illumination light. Only infrared light (IR) passes through the final dichroic mirror 3 and is emitted as is.

As mentioned above, each liquid crystal plate 18. 17. 16 are all P-polarized lights, and each liquid crystal plate 18, 17.
16 to each projection lens 41, 42. 4
3 onto a screen (not shown).

FIG. 3 is a diagram showing the main structure of a second embodiment of the present invention.

In this embodiment, the optical systems for color separation in the first embodiment are optically coupled, and only that portion is shown in FIG. Since the other configurations are the same as those in the first embodiment, the same numbers are given and explanations are omitted.

As shown in FIG. A transparent liquid 13 such as an aqueous ethylene glycol solution or silicone oil is sealed between the optical systems that separate the G and R components, and the non-contact portions of each optical system are optically coupled. For this reason,
Reflection loss at the interface between each optical system has been reduced, improving the efficiency of using the light emitted from the light source.

Note that the embodiment shown in FIGS. 1 and 3 may be modified as follows.

1. A λ/2 plate is inserted between each liquid crystal plate and each dichroic mirror. (In this case, the illumination light becomes S-polarized light) 2. A polarization plane rotating element such as a liquid crystal is used instead of the λ/2 plate.

3. A total reflection mirror is used instead of the dichroic mirror 3.

4. By using polarizing beam splitters 5, 6.7 and dichroic mirrors 1.2.3 with completely opposite wavelength characteristics, red light, green light,
Separate each color light in the order of blue light.

FIG. 4 is a diagram showing the configuration of a third embodiment of the present invention.

In this embodiment, image synthesis is performed using a cross dichroic mirror.

A liquid crystal plate 416 for the R light component (red light) image, a liquid crystal plate 417 for the G light component (green light) image, and a liquid crystal plate 418 for the B light component (blue light) image are connected to the incident cross dichroic mirror 424. It is provided so as to cover each of the three sides of the surface. Here, 424a and 424b are dichroic films for reflecting only B light and R light, respectively. The light that illuminates each of the liquid crystal plates 416 to 418 is reflected by a reflective optical system provided on the opposite side of the diloic mirror of each of the liquid crystal plates 416 to 418. LCD board 4
18, a prism 401 and a polarizing beam splitter 405 are installed next to each other as a reflective optical system for the B light component. A prism 403 and a polarizing beam splitter 407 are arranged adjacent to each other as reflective optical systems for the G light component and the R light component. Light emitted from the light source 411 is reflected by a dichroic mirror 422, a reflecting mirror 423, etc. and is incident on each of the above-mentioned reflective optical systems.

Each of the polarizing beam splitters 405 to 407 is arranged on the incident side of each reflective optical system, and λ/2 plates 408 to 410 are respectively provided on the end face from which the reflected light is emitted.

A light source 4 in which each reflective optical system is equipped with a beam reflector 420
On the output optical axis, there is a dichroic mirror 422 that reflects only the blue light to the reflective optical system for the B light component, and after passing through the reflective optical system for the G light component. A reflection mirror 423 is arranged to reflect the light of the R light component to a reflection optical system for the R light component. An infrared absorption filter 42 is provided between the light source 411 and the dichroic mirror 422.
1, and a lens group 404 for forming an image on a screen (not shown) is provided near the exit side end face of the cross dichroic mirror 424.

The light emitted by the light source 11, which is a metal halide lamp with an output luminous flux of 10,000 to 20,000 lumens, is converted into parallel light by a reflector 420, and an infrared absorption filter 42 is used to suppress the temperature rise of each liquid crystal plate 416 to 418.] The infrared rays in the light are cut.

From the parallel light rays formed here, first, only the blue light is reflected by the dichroic mirror 422 for blue reflection.
Red light and green light pass straight through.

This reflected blue light is incident on a polarizing beam splitter 405 formed by depositing a polarizing film on a prism, and only the S-polarized light (B (S)) is reflected. Here, the S-polarized light of the reflected blue light ( B (S)
) passes through the λ/2 plate 408, and its plane of polarization rotates by π/2, turning it into P-polarized blue light (B(p)+).
becomes. Furthermore, the P-polarized blue light ( B (p) 2 ) that passed through the polarized beam splitter 405 and went straight ahead.
is reflected at one side of the prism 401. These P-polarized lights (B(p)+) and (B(p)z) of the blue light are oriented parallel to each other, and the irradiation area is twice that of incidence, and the blue light is provided on one side of the cross dichroic prism 424. is incident on the liquid crystal plate 418. This blue compatible liquid crystal board 41
8. LCD panel 417 for green color, LCD panel 416 for red color
are provided on each side of the cross dichroic prism 424 as described above, and R, G, B
An image is formed according to the image signal of each color. Each liquid crystal board 41
6 to 418 are TPT active matrix driven, panel size 1 to 3 inches diagonally, and number of pixels 8 to 30.
Ten thousand picture elements are used.

Next, the red light and green light transmitted straight through the blue-reflecting dichroic mirror 422 described above will be explained.

The polarizing beam splitter 406 converts green light into S-polarized light C.
C (S) ) is reflected. Since this polarizing beam splitter 406 has the characteristics shown in FIG. 2(b) similarly to the polarizing beam splitter 6 in FIG. 1, it functions as described above. Here, the S polarization of the reflected green light (
When G(S)) passes through the λ/2 plate 409, its polarization plane rotates by π/2, and the green light becomes P-polarized light (G(p)+
). Furthermore, the P-polarized green light [G(p)2] and the red light that have passed straight through the polarizing beam splitter 406 are converted into only the P-polarized light (G(p)2) by the dichroic mirror 21 for green reflection. It is reflected, aligned parallel to the P-polarized light (G(p)+) of the green light, and enters the liquid crystal plate 417 corresponding to green light.

Next, the red light that has passed straight through the dichroic mirror 402 for green reflection is reflected by the reflection mirror 423 and changed direction, and enters the polarization beam splitter 407, where it becomes S-polarized (R(S)) of the red light. ) is reflected. The S-polarized red light (R(s)) reflected here passes through the λ/2 plate 410, and the plane of polarization rotates by π/2, becoming P-polarized red light (R(p)+). . Furthermore, the red P-polarized light (
R(1))2) is reflected by the prism 403, and P-polarized red light (R(p)+) and (R(+))2)
are aligned in parallel and enter the liquid crystal 416 corresponding to red color.

As explained above, the polarization planes of the illumination lights for each of the liquid crystal plates 418 to 416 corresponding to each color of B, G, and R are aligned in one direction. Each of these liquid crystal plates 418 to 416
Images corresponding to each color formed by the above are combined by a cross dichroic prism 424. The synthesized image is then produced by a lens group 404 having, for example, F=2.0 to 4.0 and a projection distance of about 1 to 3 m (screen size diagonal 40 to 100 inches) from the tip of the lens to the screen. An image is projected onto the screen shown.

FIG. 5 is a diagram showing the configuration of a fourth embodiment of the present invention.

In this embodiment, a cross dichroic mirror 524 separates the light emitted from a light source into R, G, and B component illumination lights, and a dichroic mirror 526 synthesizes the images obtained with each illumination light. It is.

On the output optical axis of the light source 511, the output light is R. A cross dichroic mirror 524 is provided that separates G and B component lights and emits each component light in a different direction. These R, G, and B component lights illuminate liquid crystal plates 516 to 518 that form images of each component light, and are reflected by reflective optical systems provided on each liquid crystal plate 516 to 518, respectively. and is incident on each of the liquid crystal plates 516 to 518, respectively. As a reflective optical system for the liquid crystal plate 516, a polarizing beam splitter 507 and a prism 503 are installed next to each other.
06 and a prism 502, and a polarizing beam splitter 505 and a prism 501 are provided adjacent to the liquid crystal plate 518 as reflective optical systems, respectively. Each of the polarizing beam splitters 505 to 507 constituting each of the above-mentioned reflective optical systems is arranged on the incident side of each reflective optical system, and
It reflects polarized light in the same direction as each of the adjacent prisms 501 to 503, and there is a λ/2 plate on the end surface from which the reflected light is emitted. 08 to 510 are provided, respectively.

Liquid crystal plates 518 and 517 for the B light component and the G light component are provided on one end surface of the prism 525 and one end surface of the dichroic mirror 526 adjacent to the prism 525, respectively, so that their plane orientations are orthogonal to each other. .

The dichroic mirror 525 is for combining images of each component light, and only the G component (green light) is reflected on the working surface 526l, which is the joint surface with the prism 525, and is formed parallel to the working surface 526l. Only the R light component (red light) is reflected on the working surface 5262 which serves as the output surface. The liquid crystal plate 516 mentioned above has the same surface orientation as the liquid crystal plate 518, and the image light transmitted through the liquid crystal plate 518 is projected onto the working surface 5262 by a reflecting mirror 529 installed parallel to the working surface 526. be done.

In this embodiment, the light emitted from the light source 511 is made into parallel light by a reflector 520 provided around the light source 511, and after passing through an infrared absorption filter 521, it is processed by a cross dichroic mirror 524 for R, G, It is divided into three parts of B light. With this? , R light component light is reflected upward in the drawing, B light component light is reflected downward in the drawing, and G light component light is transmitted and goes straight. Thereafter, the R light component is reflected by reflection mirrors 527 and 528, and then enters the polarizing beam splitter 507, and the G light component and the B light component are respectively reflected by the polarizing beam splitter 506. 505. At this time, each component light is aligned to P polarization in each reflection optical system including each polarization beam splitter 506 to 508, and is aligned to P polarization at each liquid crystal plate 516 to 518.
It becomes the illumination light.

Next, the image light from the liquid crystal plate 518 corresponding to blue is transmitted to the active surface 5261. 5262 and go straight ahead to lens group 50
At that time, it is combined with the image light from the liquid crystal plate 517 corresponding to green at the working surface 526, and further reflected by the reflecting mirror 529 at the working surface 526, and the liquid crystal plate corresponding to red is reflected by the reflecting mirror 529. It is combined with the image light from 516.

In this way, in each of the above-mentioned embodiments, the polarization plane of the illumination light is aligned in one direction and illuminates the liquid crystal plate, which improves the light utilization efficiency, provides uniform illumination, and reduces unnecessary light. . Therefore, the temperature rise of the liquid crystal panel can be suppressed. Furthermore, since the irradiation area from the light source is doubled, the illumination system can be made smaller, which is particularly effective when the aspect ratio is 9=16, such as for high-definition systems.

FIG. 6(a) is a diagram for explaining a conventional illumination method, and FIG. 6(b) is a diagram for explaining an illumination method according to each embodiment of the present invention. As shown in FIG. 6(b), in the present invention, the illumination surface N63 from the light source can be small. (approximately 43% of that in FIG. 6(a)) Furthermore, each illumination area is 61. Light usage area 62. 64
The amount of illumination light can be effectively utilized by approximately 54% in the conventional method and approximately 63% in the present invention. Furthermore, when using light sources with the same amount of light, the planes of polarization are not aligned in the conventional method, so
Polarized light in one direction is cut, and the efficiency becomes half of the above-mentioned approximately 54%, that is, approximately 27%. On the other hand, in the case of the present invention, since the polarization planes are aligned, the efficiency is about 63, as mentioned above.
%, it is possible to realize more than twice the light efficiency.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

In the device according to claim 1, since the liquid crystal plate is illuminated with the polarization plane of the illumination light aligned in one direction, the light utilization efficiency is improved and more uniform illumination light can be obtained. . At this time, unnecessary light absorbed by the liquid crystal plate is reduced, which has the effect of suppressing the temperature rise of the liquid crystal plate. Furthermore, since the irradiation area from the light source is expanded, the illumination system such as the light source can be made more compact.

Furthermore, the aspect ratio is 9: for Hi-Vision support.
A horizontally long one such as No. 16 has the effect of being able to use the area irradiated by the light source more efficiently.

In the device according to claim 2, since the polarizing beam splitter also serves as color separation means for separating light into R, G, and B component lights that illuminate each liquid crystal plate, in addition to the above effects,
This has the effect of simplifying the color separation optical system.

According to the third aspect of the present invention, there is an effect that the loss occurring between each illumination system can be reduced and the light utilization efficiency can be further improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a first embodiment of the present invention, and FIG. 2(a). (b). (c) is a diagram showing the wavelength dependence of the transmitted light of the polarizing beam splitter 5, 6.7 in FIG. 1, respectively, and FIGS. FIG. 6(a) is a diagram showing the configuration, FIG. 6(a) is a diagram for explaining the conventional illumination method, FIG. 6(b) is a diagram for explaining the illumination method according to the present invention, and FIGS. 7 to 9 are diagrams for explaining the conventional lighting method. FIG. 3 is a diagram showing the configuration of each conventional example. 1-3,402,,...Dichroi Kumirah422,524.526 5-7,405-407,}. ．． ．． Polarizing beam upright, 505~50 4,~43...Lens, 8~
10・408～41°・}. ．． ．． λ/2 plate, 508 ~
510 11,4] 1,511・・・・・・・・・・Light source, 12 Condenser lens, 3l Transparent liquid, 404.504・・・・・・・・・・・Lens group,
420,520......Reflector, 42], 521......Infrared absorption filter, 423,527,528...・
...Reflection mirrors 424a, 424B...
・・Tylock membrane, 5261.5262・・・・・・・
...Slope.

Claims (1)

[Claims] 1. In an illumination system for a liquid crystal video projector that is provided for each of three transmissive liquid crystal plates that form R, G, and B images, and that illuminates each liquid crystal plate to form an image, Each illumination system includes a polarizing beam splitter into which illumination light emitted from a light source is incident, and a reflecting means for reflecting the light transmitted through the polarizing beam splitter, and the polarizing beam splitter and the reflecting means are arranged adjacent to each other. , are arranged so as to reflect incident light toward the liquid crystal plate, and a λ/2 plate is provided between the end face from which one of the reflected light is emitted and the liquid crystal plate. A polarized illumination system for a liquid crystal video projector characterized by: 2. The polarized illumination system for a liquid crystal video projector according to claim 1, wherein at least one of the polarized beam splitters constituting each illumination system has wavelength dependence. . 3. The polarized illumination system for a liquid crystal video projector according to claim 1 or 2, wherein each illumination system is optically coupled.