JPH02290390A - Projecting type display device - Google Patents

Abstract

PURPOSE:To simplify adjustment of the above device and to make thin in thickness and to militarize the device by selecting a center axis of an optical path from each light bulb to a projection optical means on the same plane so that the optical path length is identical. CONSTITUTION:Polarized plates 36-38, 39-41 and monochromatic (red, green, blue) filters 43-45 are arranged so as to have liquid crystal panels 33-35 inserted inbetween. Translucent prisms 30b, 30b are used as a color synthesis means and a screen 32 is irradiated with the light synthesized by the prisms 30b, 30b through a lens 31. Then the optical path length from each of the panels 33-35 to the lens 31 is selected identically. A video signal subjected to color demodulation in the case of a television signal is inputted to the panels 33-35 with a relevant filter arranged thereto and since the transmissivity is controlled in the panel, the light subjected to color synthesis and directed to the lens 31 is subjected to color adjustment and the screen 31 is irradiated with the light with magnification.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a projection display device, and particularly to the structure of its optical system.

(Prior art and problems to be solved by the invention) Conventionally,
Projection display devices include movies, slides, and CR.
There was projection television by T. Movies and slides project images printed on film, and because of the restriction that film is used as a medium for projection, it has not been possible to view images online in response to input signals.

On the other hand, CRT projection television is
This method was created due to the physical limitations of creating a large screen of 26 inches or more (cathode ray tube) itself, and because it projects the light emitted from the CRT as it is,
The brightness of the CRT is required to be quite high, so a special CRT is required.
It is a very large system that uses RT with high power and is used for cooling, and there is a problem that it is difficult to use it for home use.

In addition, projection television using CRT has an insufficient amount of light and insufficient brightness on the screen.
Because the light from the tube is synthesized on the screen, even if you make subtle adjustments to the screen position and system position, color shifts tend to occur on the screen, and the overall image quality is extremely poor, resulting in a screen that is difficult to see. There was a point.

Furthermore, the system is special and large CRT, special power supply,
The problem was that it was equipped with an adjustment system and was quite expensive.

Conventional projection-type display devices have the above-mentioned problems, and cannot take full advantage of the advantages of large-screen televisions or projection-type televisions, which has delayed their widespread use.

The present invention was made to solve these problems, and it is an object of the present invention to provide a projection display device that has high image quality, is easy to handle, and has a compact system.

(Means for Solving the Problem) A projection type display device according to a first invention includes a colored light generating means that generates three colored lights corresponding to the three primary colors of red, green, and blue, and a red colored light that receives the red colored light. a first light valve that performs modulation corresponding to the signal; a second light valve that receives green color light and performs modulation corresponding to the green signal; and a second light valve that receives blue color light and performs modulation corresponding to the blue signal. It has a third light valve, a first light valve, and projection optical means for projecting colored light modulated by the second light valve and the third light valve, respectively.

The central axes of the optical paths from the first light valve, the second light valve, and the third light valve to the projection optical means each pass on the same plane, and the first light valve, the second light valve, and The optical path lengths from the third light valve to the projection optical means are made equal.

A projection display device according to a second invention includes, in addition to the above-described configuration, a first light valve, a second light valve, and a third light valve.
The color combining means combines the three colored lights modulated by the light valves and makes the combined light enter the projection optical means.

(Function) In the first invention, each of the red, green, and blue colors generated by the color light generating means is modulated by the first light valve, the second light valve, and the third light valve, respectively;
After that, the image is projected by the projection optical means. At this time, the first
Since the central axes of the optical paths from the light valve, the second light valve, and the third light valve to the projection optical means pass on the same plane, the optical paths do not deviate from the plane, and this makes the optical elements compact. It can be stored in a small size. Furthermore, since the forward path lengths are equal, the focal positions of the red, green, and blue lights coincide, and a clear image can be obtained.

Further, in the second invention, the red, green, and blue color lights modulated by the first light valve, the second light valve, and the third light valve are combined by the color combining means, and then the projection optical means Projected by At this time, since the optical path lengths from the first light valve, second light valve, and third light valve to the projection optical means are the same,
The focal positions of each of the red, green, and blue colors match, and a clear image can be obtained.

(Embodiment) FIG. 1 is a configuration diagram of an optical system of a projection type liquid crystal display device according to an embodiment of the present invention. In this embodiment, polarizing plates 3G to 38, 39 are sandwiched between liquid crystal panels 33 to 35.
4l and monochromatic color filters 43 to 45 are arranged. Semi-transparent prisms 30a, 30 as color synthesis means
The light that has been optically combined by the semi-transparent prisms 30a and 30b is projected onto the screen 32 by the lens 3l. The central axes of each optical path from the liquid crystal panels 33 to 35 to the lens 31 are on the same plane,
Moreover, the optical path lengths from the liquid crystal panels 33 to 35 to the lens 31 are arranged to be equal.

For example, the light from the light source 45 passes through the monochromatic color filter 42, becomes red light, enters the liquid crystal panel 33 via the polarizing plate 41, and then enters the semi-transparent prism 30a via the polarizing plate 37. Similarly, light [4B,
The light from 47 is passed through a monochromatic color filter 44. The light becomes green and blue by passing through the polarizing plate 40.
39 through the liquid crystal panel 35. 34, and then a polarizing plate 36. 38 and enters the semi-transparent prism 30b. The green light incident on the semi-transparent prism 30b is transmitted through the semi-transparent film 47 as is, and the blue light is reflected and incident on the semi-transparent prism 30a. The red light incident on the semi-transparent prism 30a is reflected by the semi-transparent film 48, and the green and blue lights are transmitted through the lens 3.
The light beams are combined into one optical axis and directed toward the lens 31.

Each liquid crystal panel 33, 35. 34, if it is a television signal, the color-demodulated video signal is input to a panel where each corresponding filter is arranged, and the transmittance is controlled there, so that the light that has been color-combined and directed to the lens 31 is The color is adjusted, and the lens 3l magnifies the screen 3.
1.

In this embodiment, from the liquid crystal panels 33 to 35 to the lens 31
The liquid crystal panels 33 to 35 are arranged so that the respective optical path lengths are equal, and the images of the liquid crystal panels 33 to 35 coincide on the screen 32.

FIG. 2 is an explanatory diagram of the imaging position when the optical path length changes. For example, the object A is displayed on the screen 3 by the lens 31.
Assuming that the image is formed on the screen 32, if its position changes and it becomes the position of the subject a, the lens 3l will move the image onto the screen 32.
The image will be focused on a. When the position of the subject changes in this way, the imaging position also changes, but in this embodiment, as described above, the optical path lengths from the liquid crystal panels 33 to 35 to the lens 3l are arranged to be equal. Since the imaging positions of the green and blue images are the same, consideration has been given to ensuring that high-quality images are obtained without color blurring.

The liquid crystal panels 33 to 35 are basically of the TN (Twisted Nematic) type, and are composed of a liquid crystal material and glass plates sandwiching it from both sides. The transmittance changes and it functions as a liquid crystal shutter. This TN system is excellent in contrast, gradation, response speed, transmittance, lifespan, etc., and may be either a transmissive type or a reflective type, and especially when a transmissive type is used, the optical system becomes simpler.

FIG. 3 is an explanatory diagram showing a configuration example of the liquid crystal panels 33 to 35, and here an active matrix type is illustrated. Normally, liquid crystals are difficult to multiplex, and as a result, the number of scanning lines used is small, resulting in a drop in resolution.However, this drawback has been solved by the active matrix method shown in this figure. The transistor 10 is turned on by the timing line 12 corresponding to the scanning line, and display data is written into the liquid crystal drive electrode 1l arranged in the pixel via the data line 13. Then transistor 10
Even if it is turned off, the written display data is retained and drives the liquid crystal. Transistor IO used here
Since it is necessary to form on a transparent substrate, polycrystalline or amorphous silicon thin film transistors (hereinafter referred to as TPT) are used.
) is used.

Since this TPT is a thin film and is statically driven, it has excellent contrast, gradation, and responsiveness, and has the advantage of increasing the number of pixels, resulting in higher resolution. Further, this TPT is excellent in terms of ability to be formed on a glass substrate, transparency (transmittance, spectrum), transistor characteristics (mobility, on/off ratio, switching speed, degree of integration), cost, safety, and the like.

Furthermore, the liquid crystal panels 33 to 35 are of a transmissive type, and the configuration of the optical system is extremely simple.

Further, in this embodiment, a three-panel projection system using liquid crystal panels 33 to 35 is used, and the liquid crystal panel 33
In addition to the advantages that the original light amount can be lowered because the light from ~35 is combined, and the resolution is three times higher than that of a single panel method if the panel has the same resolution, the color filter is
There are advantages such as the fact that a single-color solid filter is sufficient instead of a finely arranged color filter, and that fixed pixel defects can be eliminated because there is a very low possibility that pixel defects will occur in the same position on all three sheets.

In addition, the light from the liquid crystal panels 33 to 35 is synthesized on one side of the lens 3l, and the distance from the lens to the screen,
Even when changing the projection size, the operation is simplified by simply adjusting the focus by simply operating the lens.

In addition, the liquid crystal panels 33 to 35 are arranged at right angles to each other, and the reflective surfaces of the transflective prisms 30a and 30b are arranged at right angles, making the optical system compact.
Colored light from directions shifted by 90 degrees can be combined into a single beam of light, which simplifies the layout of the optical system when manufactured into a product.

By the way, in this embodiment, in principle, the liquid crystal panel 3
Since images 3 to 35 are to be enlarged and reproduced, the light sources 45 to 47 need to be lamps with high brightness. As a result, the illuminance on the liquid crystal panels 33 to 35 is extremely high <, 10
It becomes 50,000 ΩX to 500,000 Nx. On the other hand, since TPT is a semiconductor, an electromotive force is generated when light is incident on the TPT, and even if the transistor 11 is in an off state, it approaches an on state due to the photocurrent, and the contrast of the display screen is significantly reduced. Normally, the illuminance at which this contrast starts to decrease is approximately 100,000 Nx for white light, and in terms of wavelengths of light, this is the long wavelength side, that is, the band from red to infrared, where the most absorption occurs.

In order to prevent the contrast from decreasing due to this light, color filters 42 to 44 are provided on the liquid crystal panel 3 in this embodiment.
The light sources 3 to 35 are arranged on the side of the light sources 45 to 47. When a color filter is built into a liquid crystal panel, the color filter layer is placed closer to the light source than the liquid crystal material, and TPT
This can be achieved by placing a glass substrate equipped with this on the projection lens side of the liquid crystal material. As a result, light always enters the TFT surface through the color filter and glass substrate, so the amount of blue and green light is equivalently less than 1/10, and the amount of red light is also 1/5. The induction of photocurrent in the TPT due to intense light incidence is suppressed, and it is possible to prevent development in which the contrast of the image deteriorates and becomes difficult to see.

FIG. 4 is a characteristic diagram showing the relationship between the intensity of light irradiated to the TPT and the contrast at that time.

In this characteristic diagram, A is the intensity and contrast of light irradiated to the TPT when the TPT is placed on the projection lens side, and B is the intensity and contrast when the TPT is placed on the light source side. As is clear from comparing the two, it can be seen that the intensity of light irradiated to the TPT can be lowered with A, and the contrast is greater. In addition, A' is the intensity and contrast of the light irradiated to the TPT when the TPT is placed on the projection lens side and a colored light generating means is provided,
B' is a case in which TPT is placed on the light source side and colored light generating means is provided. As is clear from a comparison of the two, it is clear that A- can further reduce the intensity of light irradiated to the TPT.

FIG. 5 is a block diagram of an optical system of a projection display device according to another embodiment of the present invention. In this embodiment, a semi-transparent mirror 52. I am using 53. For example, light from the light source 62 enters the color filter 59, of which red light is transmitted, and after passing through the liquid crystal panel 56 (polarizing plate is omitted), the red light is transmitted through the semi-transparent mirror 52. . The light from the light source 63 enters the color filter 60, and the light at its inner edge is transmitted, and the green light passes through the liquid crystal panel 57 (polarizing plate is omitted) and then passes through the semi-transparent mirror 53. The light is further reflected by a total reflection mirror 55 and then reflected again by a semi-transmission mirror 52. The light from the light source 64 enters the color filter 6l, of which blue light is transmitted, and after passing through the liquid crystal panel 58 (polarizing plate is omitted), the blue light is reflected by the total reflection mirror 54. Thereafter, it is further reflected by a semi-transmissive mirror 53, reflected by a total reflection mirror 55, and then reflected again by a semi-transmissive mirror 52.

The red light transmitted through the semi-transmissive mirror 52 and the green and blue lights reflected from the semi-transmissive mirror 52 are combined on the -axis of the lens 5o, magnified by the lens 50, and transmitted to the screen 5l.
is projected on.

Also in this embodiment, from the lens 50 to each liquid crystal panel 5
B, 57. The central axes of the optical paths up to 58 are on the same plane, and each optical path length is the same.

Further, liquid crystal panels 513, 57. 58 are arranged in parallel, and semi-transparent mirrors 52 . 53 are arranged in parallel, it is possible to combine colored light from the same direction into a single beam of light, and the optical path can also be folded inward, making the optical system layout neat and compact when manufactured into a product. Can be summarized.

FIG. 6 is a block diagram of an optical system of a projection display device according to another embodiment of the present invention, and this embodiment includes a semi-transparent mirror 75 as a color combining means. This is an example using 76. For example, green light 77 is modulated by a liquid crystal panel 73 (polarizing plate is omitted) and then enters a semi-transparent mirror 75. blue light 7
8 is modulated by a liquid crystal panel 74 (polarizing plate is omitted) and then enters a semi-transmissive mirror 75. Semi-transparent mirror 7
The green light incident on the mirror 5 is transmitted, the blue light is reflected, and the green light and blue light are color-combined and enter the semi-transparent mirror 76.

The red light is modulated by a liquid crystal panel 72 (polarizing plate is omitted) and then enters a semi-transmissive mirror 76. The green and blue lights incident on the semi-transparent mirror 76 are transmitted, the red light is reflected, the green, blue and red lights are color-combined and directed to the lens 70, where they are projected onto the screen 71. .

Also in this embodiment, from the lens 70 to each liquid crystal panel 7
2, 73. The central axes of the optical paths up to 74 are on the same plane, and each optical path length is configured to be the same.

In all of the above embodiments, color synthesis is performed by inserting a semi-transparent film in the optical path (for example, the transparent film 47, 48 in Fig. 1,
Semi-transmissive mirror 52.53 in FIG. 5, semi-transmissive mirror 75.76 in FIG. 6). Therefore, there is no problem when the amount of light from the light source is sufficient, but when it is small, it is necessary to minimize the light loss in the semi-transparent film. This can be handled by utilizing the fact that each of the three light beams has different wavelengths: red, green, and blue, or by utilizing the fact that the TN liquid product is polarized due to its properties.

FIG. 7(a) is an explanatory diagram of a semi-transparent mirror in which an interference film 8l is formed on an optical glass 80. The figure (opening) is its characteristic diagram. This interference film 8l has a property of transmitting red light and reflecting light other than red light, for example, and as a result, transmits red light and reflects green light, thereby combining red and green light without optical loss. be able to.

In this method, by appropriately selecting the wavelength selective reflection characteristics, both transmittance and reflectance can be increased.
The three colors of blue light can be combined without loss, increasing the efficiency of light utilization.

FIG. 8 is an explanatory diagram of a semi-transmissive mirror using a polarizing plane. TN liquid products use a polarizing plate on the screen to display images, and the light that enters the human eye from the liquid crystal panel is polarized light in principle. Therefore, for example, the plane of polarization is 90 for green and blue, red and green.
If the polarization plane is shifted, selective transmission and reflection of the polarization plane becomes possible.Based on this principle, a polarization reflection plane 83 with good transmission characteristics is formed on the optical glass 82 so that the polarization plane is horizontal. If red light is horizontally polarized, it will pass through, but green light is vertically polarized, so it will be reflected.

In this method as well, both transmittance and reflectance can be increased by appropriately selecting the polarization reflecting surface and the polarization axis of the incident color destination, and by using a color synthesis method that utilizes wavelength selection characteristics. The three colors of red, green, and blue light can be combined without loss, increasing the efficiency of light use.

FIG. 9 is an external view of the projection type image display device manufactured using the liquid crystal panel as described above, and shows the projection body 86 which has the built-in optical system shown in FIGS. 1, 5, or 6. The light beam 88 is projected onto a screen 87.

(Effects of the Invention) As described above, according to the present invention, the central axes of the optical paths from each light valve to the projection optical means are on the same plane, and the forward path lengths are equal. The optical system is easy to design and adjust, making it thinner and smaller, and the projected images from each light valve match on the screen, resulting in a clear image. Since the color combining means simply combines three colored lights on the same plane into one, adjustment is extremely easy with a single projection lens.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of the optical system of a projection display device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of the optical path length, and FIG.
The configuration diagram of the liquid crystal panel shown in the figure, Figure 4 is the TPT of the liquid crystal panel.
5 and 6 are respectively diagrams showing the configuration of the optical system of a projection display device according to another embodiment of the present invention, and FIG. (
A) and (opening) are explanatory diagrams of a semi-transmissive mirror using an interference film used in the above embodiment, Fig. 8 is an explanatory diagram of a semi-transmissive mirror using a difference in polarization plane, and Fig. 9 is an explanatory diagram of the above embodiment. 1 is a perspective view of a projection type liquid product display device of FIG. 33-35. 56-58. 72-74...Liquid crystal panel, 30a. 30b... semi-transparent prism, 52,
53, 75. 78...Semi-transparent agent Patent attorney Sou Sasaki Figure Figure Figure Figure TFTE 枦JFt7K greedy v{ m'! /cm2 Figure (A) Figure (B) Figure A Figure Figure

Claims (12)

[Claims] (1) a colored light generating means that generates three colored lights corresponding to the three primary colors of red, green, and blue; a first light valve that receives the red colored light and performs modulation corresponding to the red signal; a second light valve that receives the blue color light and performs modulation corresponding to the green signal; a third light valve that receives the blue color light and performs the modulation corresponding to the blue signal; a projection optical means for projecting colored light modulated by the second light valve and the third light valve, respectively;
the first light valve, the second light valve and the third light valve;
The central axes of the optical paths from the light valves to the projection optical means pass on the same plane, and the optical path lengths from the first light valve, the second light valve, and the third light valve to the projection optical means are A projection type display device characterized in that each of the projection type display devices is made equal to each other. (2) The first light valve, the second light valve, and the third light valve are active matrix liquid crystal light valves driven by active switching elements. Projection type display device described in Section 2. (3) a colored light generating means that generates three colored lights corresponding to the three primary colors of red, green, and blue; a first light valve that receives the red colored light and performs modulation corresponding to the red signal; a second light valve that receives the blue color light and performs modulation corresponding to the green signal; a third light valve that receives the blue color light and performs the modulation corresponding to the blue signal; a color combining means for combining the three colored lights modulated by the second light valve and the third light valve, and a projection optical means for projecting the colored light combined by the color combining means; light valve, a second light valve and a third light valve.
The central axes of the optical paths from the light valves to the projection optical means pass on the same plane, and the optical path lengths from the first light valve, the second light valve, and the third light valve to the projection optical means are A projection type display device characterized in that each of the projection type display devices is made equal to each other. (4) The projection type display device according to claim 3, wherein the color combining means includes two color combining surfaces, and the color combining surfaces are arranged parallel to each other. (5) The projection type display device according to claim 4, wherein the first light valve, the second light valve, and the third light valve are arranged parallel to each other. (6) The projection type according to claim 3, wherein the color compositing means includes two color compositing surfaces, and the color compositing surfaces are arranged at right angles to each other. Display device. (7) The first light valve, the second light valve, and the third light valve are arranged at an angle of 90° so that the light valves face the projection optical means in the same optical manner. 7. The projection type display device according to claim 6, wherein the projection display device is arranged facing in a shifted direction. (8) Claim 3, wherein the color synthesis means includes two color synthesis surfaces, and the color synthesis surfaces include two selective reflection surfaces having different wavelength selection characteristics. The projection display device described. (9) The projection type display device according to claim 3, wherein the color combining means includes two color combining surfaces, and the color combining surface includes a polarization reflecting surface. (10) The projection type display device according to claim 3, wherein the color compositing means includes two color compositing surfaces, and the color compositing surfaces include two semi-transparent surfaces. (11) The projection type display device according to claim 3, wherein the color combining means includes two color combining surfaces, and the color combining surface is formed by two mirrors. . (12) The projection type display device according to claim 3, wherein the color compositing means includes two color compositing surfaces, and the color compositing surfaces are formed by a right-angled prism.