JP2828067B2 - Projection display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection display device,
In particular, it relates to the structure of the optical system. 2. Description of the Related Art Heretofore, as a projection type display device, there has been a movie, a slide, or a projection television using a CRT. [0003] Movies and slides project an image printed on a film, and there is a restriction that the projection is performed using the film as a medium. I could not see the image. [0004] On the other hand, a projection television using a CRT is a system born from the fact that a CRT (CRT) itself constitutes a large screen of 26 inches or more due to physical restrictions, and projects the light emitted from the CRT as it is. For this reason, the brightness of the CRT is considerably required, so that the system is a very large system in which a special CRT is used with a large power and is cooled and used, and there is a problem that it is difficult to use the CRT for home use. [0005] In addition, the projection television using a CRT has insufficient light intensity and insufficient brightness on the screen, and the position of the screen and the system are delicately adjusted because light from three tubes is synthesized on the screen. However, there is a problem that a color shift easily occurs on the screen, the image quality is extremely reduced as a whole, and the screen becomes considerably hard to see. Further, the system has a special and large CRT,
There is a problem in that a special power supply and adjustment system are provided, and the cost is considerably high. [0007] The conventional projection type display device has the above-mentioned problems, and its use has been delayed because the advantages of the large-screen television or the projection type television cannot be fully utilized. The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a projection type display device which has high image quality, is easy to handle, and has a compact system. According to the present invention, there is provided a projection display apparatus, wherein first modulation means modulates red light, second modulation means modulates green light, and blue light is modulated. A third modulating means, a synthesizing means for synthesizing the color lights modulated by the first, second and third modulating means, and a projection optical means for projecting the light synthesized by the synthesizing means,
Each of the first, second and third modulating means has a matrix type liquid crystal panel and a polarizing means for transmitting the color light emitted from the matrix type liquid crystal panel, and is emitted from each of the matrix type liquid crystal panels. The respective color lights are transmitted through the respective polarizing means and then incident on the synthesizing means, and the projection optical means is arranged on the extension of the optical axis of the green light transmitted through the polarizing means of the second modulation means. Arranged, on both sides of the optical axis of the green light, a matrix type liquid crystal panel and a polarizing unit of the first modulating unit, and a matrix type liquid crystal panel and a polarizing unit of the third modulating unit are arranged, The red light and the blue light transmitted through the polarization means of the first modulation means and the polarization means of the third modulation means, respectively, are reflected by the synthesizing means and synthesized on the same optical axis as the optical axis of the green light. It is characterized by comprising. According to the present invention, there are provided three modulation means for modulating three color lights, each of which comprises a matrix type liquid crystal panel and a polarization means for transmitting each color light emitted therefrom. An image is formed for each color light transmitted through the polarizing means. The light of the image formed for each color light formed here is combined by the combining means. If each color light is transmitted through the polarizing means after being combined, the distance from the liquid crystal panel to the polarizing means will be large and the color light will be diffused and a clear image cannot be formed, but in the present invention, the image is formed for each color light and then combined. Thus, clear display image quality can be obtained. The matrix type liquid crystal panel and the polarizing means of the red light and blue light modulating means are arranged on both sides of the green light transmitted through the polarizing means of the green light modulating means with the optical axis interposed therebetween. Then, the blue light and the red light transmitted through the polarizing means are reflected by the combining means and combined on the optical axis of the green light, so that the matrix type liquid crystal panel of the blue light and the red light and the polarized light are provided on both sides of the optical axis of the green light. Means are arranged. Further, a projection optical unit is arranged on the extension of the optical axis of the green light. This makes it possible to configure a projection display device in which the components are arranged in a well-balanced manner and has a sense of stability. 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, a three-panel projection system is used. In this projection type liquid crystal display device, optical axis synthesis is performed by using a semi-transmissive prism 30. Liquid crystal panels 33, 34, 3
5, polarizing plates 36, 37, 38, 39, 40,
41 and a single color filter 42, 43, 44 are arranged. For example, the light from the light source 45 passes through the monochromatic color filter 42 to become red light and becomes a red light.
, And then enters the transflective prism 30 a via the polarizing plate 36. Similarly,
The light from the light sources 46 and 47 is
44, the light becomes green and blue light.
The light enters the liquid crystal panels 34 and 35 through 0 and 41, and then enters the transflective prism 30b through the polarizing plates 37 and 38. The green light incident on the semi-transmissive prism 30b is transmitted through the semi-transmissive film 47 as it is, and the blue light is reflected and incident on the semi-transmissive prism 30a. The red light incident on the semi-transmissive prism 30a is reflected by the semi-transmissive film 48, the green and blue lights are transmitted as they are, and the red, green and blue lights are
The light is combined with one optical axis and directed to the lens 31. In each of the liquid crystal panels 33 to 35, in the case of a television signal, a color-demodulated video signal is input to a panel in which a corresponding filter is arranged, and the transmittance is controlled there. The light directed to the lens 31 is adjusted in color, enlarged by the lens 31 and projected on the screen 32. Liquid crystal panels 33 to 35 are arranged for image formation with respect to the light sources 45 to 47, the lens 31 and the screen 32. The liquid crystal panels 33 to 35 are basically provided with a TN (twisted nematic) system. I'm using Each of the liquid crystal panels 33 to 35 is composed of a liquid crystal material and a glass plate sandwiching the liquid crystal material from both sides. When a voltage is applied to the liquid crystal material, its transmittance changes, and functions as a liquid crystal shutter. This TN method is excellent in contrast, gradation, response speed, transmittance, lifetime, etc.
In particular, in the case of the transmission type, there is an advantage that the optical system is simplified. The feature of this embodiment is that the optical system can be easily constituted by a light source such as a simple lamp or the like, a lens, a screen, and the like. Further, since the liquid crystal panels 33 to 35 are originally very thin, the system is compact. At a low price,
At the same time, it is very easy to handle. For example, even if the distance from the lens 31 to the screen 32 changes, focusing can be easily performed by the lens 31 in this method. The screen size can be arbitrarily selected by changing the focal length of the lens 31. This is a feature that cannot be realized with a conventional CRT projection television. FIG. 2A is an explanatory diagram showing an example of the configuration of the liquid crystal panels 33 to 35. Here, the active matrix system is shown. The liquid crystal is usually difficult to multiplex, so that the number of scanning lines used is small and the resolution has to be reduced. However, the drawback is solved by the active matrix system as shown in FIG. A transistor 1 is provided by a timing line 12 corresponding to a scanning line.
0 turns on, and the display data is written to the liquid crystal drive electrode 11 arranged in the pixel via the data line 13. afterwards,
Even if the transistor 10 is turned off, the written display data is held as it is, and the liquid crystal is driven. Since the transistor 10 used here needs to be formed on a transparent substrate, a polycrystalline or amorphous silicon thin film transistor (hereinafter, referred to as TFT) is used. Since this TFT is a thin film and is statically driven, it has the advantages of excellent contrast, gradation, and responsiveness, and has the advantage that the number of pixels can be increased to increase the resolution. Further, this TFT is excellent in that it can be formed on a glass substrate, transparency (transmittance, spectrum), transistor characteristics (mobility, on / off ratio, switching speed, integration degree), cost, safety, and the like. FIG. 2B is a cross-sectional view showing a configuration example of a liquid crystal panel using a TFT, in which a TFT is mounted on a glass substrate 16 and a drive electrode 19 is formed. Further, a drive electrode 20 is formed on the opposite glass substrate 15, and a liquid crystal material 18 is sealed by a sealant 17. The glass substrates 15 and 16 of the liquid crystal panels 33 to 35 are suitable for application to this type of projection display device because of their heat resistance, flatness, chemical resistance, transparency, low cost, and the like. In this embodiment, since the images on the liquid crystal panels 33 to 35 are enlarged and reproduced in principle, the light sources 45 to 47 need high-intensity lamps. As a result, the illuminance on the liquid crystal panels 33 to 35 becomes very high. On the other hand, when light is incident on the TFT because it is a semiconductor, an electromotive force is generated. Even when the transistor 10 is in an off state, the transistor 10 approaches an on state due to a photocurrent, and the contrast of a display screen is significantly reduced. Usually, the illuminance at which the reduction of contrast starts to occur is about 100,000 lx for white light, which is a long wavelength side in terms of light wavelength, that is, a band where red to infrared light is most absorbed. In order to prevent a decrease in contrast due to the light, in this embodiment, the color filters 42 to 4 are used.
4 is arranged on the light source 45-47 side with respect to the liquid crystal panels 33-35 (FIGS. 1 and 2 (b)), and the glass substrate 16 on which the TFT is mounted is arranged on the projection lens 31 side of the liquid crystal material 18. . As a result, the color filter 4
Since light beams 2 through 44 and the glass substrate 15 are incident, blue and green light are equivalently reduced to 1/10 or less, and even red light is reduced to 1/5. Induction of the photocurrent of the TFT due to the light incidence is suppressed, and development in which the contrast of the image is reduced and the image is difficult to see can be prevented. Further, if the panels have the same resolution, the resolution is improved three times as compared with the one-panel system. In addition, since it is not additive juxtaposition using the resolution of the human eye but complete admixture, good color reproduction can be achieved even when the projected image is viewed close up and the magnification is large. Further, since there is very little possibility that three pixel defects occur at the same position, there is an advantage that fixed pixel defects can be erased. FIG. 3 is a diagram showing a configuration of an optical system as a reference example of the projection display device. This configuration example is an example of a projection display device using semi-transmissive mirrors 52 and 53. For example, light from the light source 62 is incident on the color filter 59 and red light is transmitted therethrough, and red light is transmitted through the liquid crystal panel 56 (a polarizing plate is omitted) and then transmitted through the semi-transmissive mirror 52. I do. The light from the light source 63 is incident on the color filter 60 and green light is transmitted therethrough, and the green light is transmitted through the liquid crystal panel 57.
After passing through a polarizing plate (not shown), the light passes through the semi-transmissive mirror 53, is further reflected by the total reflection mirror 55, and is reflected again by the semi-transmissive mirror 52. Light from the light source 64 is incident on the color filter 61, and blue light is transmitted therethrough, and blue light is transmitted through the liquid crystal panel 58 (a polarizing plate is omitted).
, After being reflected by the total reflection mirror 54, further reflected by the transflective mirror 53, reflected by the total reflection mirror 55, and then reflected by the transflective mirror 52 again. The red light transmitted through the semi-transmissive mirror 52 and the green and blue lights reflected by the semi-transmissive mirror 52 are
0 is synthesized on one axis, enlarged by the lens 50 and projected on the screen 51. At this time, each liquid crystal panel 5 is
The optical path lengths up to 6, 57 and 58 are configured to be the same, so that the projected images of the liquid crystal panels 56, 57 and 58 match on the screen 51, and a high quality image is obtained. Is taken into account. FIG. 4 is a diagram showing a configuration of an optical system according to another embodiment of the present invention. In this embodiment, the transflective mirror 7 is used.
This is an example of a projection display device using 5, 76, and has a configuration in which a total reflection mirror is omitted. For example, green light 77 is modulated by a liquid crystal panel 73 (a polarizing plate is omitted), and then enters a semi-transmissive mirror 75. The blue light 78 is modulated by a liquid crystal panel 74 (a polarizing plate is omitted), and then enters a semi-transmissive mirror 75. The green light incident on the semi-transmissive mirror 75 is transmitted and the blue light is reflected, and the green light and the blue light are color-combined and incident on the semi-transmissive mirror 76. The red light 79 is modulated by a liquid crystal panel 72 (a polarizing plate is omitted) and then enters a semi-transmissive mirror 76. The green and blue lights incident on the semi-transmissive mirror 76 are transmitted and the red light is reflected, and the green, blue and red lights are color-combined and directed to the lens 70.
1 is projected. In each of the above embodiments, a semi-transmissive film is inserted in the optical path to perform color synthesis (for example, the transmissive film 4 shown in FIG.
7, 48, semi-transmissive mirrors 52 and 53 in FIG. 3, and semi-transmissive mirrors 75 and 76 in FIG. 4). Therefore, there is no problem when the light amount of the light source is sufficient, but when it is small, it is necessary to minimize the light loss in the semi-transmissive film. At this time, each of the three light beams is red,
This can be dealt with by utilizing the fact that the wavelengths are different from those of green and blue, or that the TN liquid crystal is polarized due to its properties. FIG. 5A shows an interference film 81 on the optical glass 80.
FIG. 4 is an explanatory view of a semi-transmissive mirror on which is formed. FIG. 2B is a characteristic diagram thereof. The interference film 81 has a property of transmitting, for example, red light and reflecting other than red light. As a result, for example, it transmits red light and reflects green light, and combines red and green light without light loss. be able to. In this scheme,
By appropriately selecting the wavelength selective reflection characteristics, both the transmittance and the reflectance can be increased, and the three color lights of red, green, and blue can be combined without loss, and the light utilization rate can be increased. FIG. 6 is an explanatory diagram of a semi-transmissive mirror using a polarization plane. The TN liquid crystal is displayed on a screen using a polarizing plate, and light entering the human eye from the liquid crystal panel is polarized light in principle. Therefore, for example, if the polarization planes are shifted by 90 ° between green and blue and between red and green, selective transmission and reflection of the polarization plane become possible. Based on such a principle, a polarization reflection surface 83 having good transmission characteristics is formed on the optical glass 82 so that the polarization plane is horizontal. Red light is transmitted as it is when it is horizontally polarized, while green light is reflected because it is vertically polarized. Also in this method, by appropriately selecting the polarizing reflection surface and the polarization axis of the incident color light, and by using a color combining means utilizing wavelength selectivity, both transmittance and reflectance can be increased, Red, green, and blue color lights can be combined without loss, and the light utilization rate can be increased. FIG. 7 is an external view of the projection type image display device manufactured using the liquid crystal panel as described above.
A light beam 88 emitted from a projection body 86 having the optical system shown in FIG. 3 or 4 is projected on a screen 87. According to each of the embodiments described above, the following effects can be specifically obtained. (A) Since a transmissive liquid crystal panel is used, a polarizing beam splitter is unnecessary as in the case of the reflective type, the polarizing optical system is simplified, and the system is compact. Further, since the unmodulated light does not mix with the projection light as in the case of the reflection type, there is no deterioration in contrast in such a case. (B) Since the substrate on which the TFT is formed is arranged on the side of the projection optical means, the intensity of light irradiated on the TFT is reduced, and as a result, the photocurrent caused by light is suppressed, and the contrast of the display screen is reduced. Can be suppressed. (C) Further, since the three-panel projection system is adopted, the following advantages are provided. The color lights (red, green, and blue) separated by the color light generating means are respectively incident on the light valve means, so that the light intensity applied to the TFT can be reduced.
The above-mentioned effect (b) is obtained. Furthermore, since the white light is incident on the incident side polarizing plate after being separated into three primary colors, the light intensity is reduced to about 1/3, and the temperature rise of the incident side polarizing plate is suppressed. For this reason, a rise in the temperature of the transmissive liquid crystal panel is suppressed, a decrease in contrast due to a temperature change is suppressed, and the life of the polarizing plate is prolonged. Further, if the panels have the same resolution, the resolution is improved three times as compared with the one-panel system. In addition, since it is not additive juxtaposition using the resolution of the human eye but complete admixture, good color reproduction can be achieved even when the projected image is viewed close up and the magnification is large. Since there is very little possibility that three pixel defects will occur at the same position, there is an advantage that fixed pixel defects can be erased. Further, when a color filter is used as the color light generating color means, a solid color filter may be used instead of a finely arranged three colors. Therefore, when a color filter (one color filter) in which three colors are finely arranged is used, only the specific color light is transmitted and the other color light is not transmitted, so that the light amount is reduced to about 1/3. Such a case does not occur when a solid filter is used. Therefore, if the light amount to the color filter is the same, the light amount of the light source in the present invention is reduced to about 1/3 as compared with the case of one color filter. Can be lowered. (D) Since the generated images generated by the respective transmissive liquid crystal panels are synthesized by the synthesizing means and projected, the distance from the projection optical means to the screen and the change in the projection size can be simply changed. Focusing can be achieved only by operating the projection optical means, and the operation is simplified. As described above, according to the present invention, 3
It has three modulating means for modulating one color light, each modulating means has a matrix type liquid crystal panel and a polarizing means for transmitting each color light emitted therefrom, and an image is formed for each color light transmitted through the polarizing means. It is formed. The image for each color light formed here is synthesized by the synthesizing means. If each color light is transmitted through the polarizing means after being combined, the distance from the liquid crystal panel to the polarizing means will be large and the color light will be diffused and a clear image cannot be formed, but in the present invention, the image is formed for each color light and then combined. Thus, clear display image quality can be obtained. Further, the matrix type liquid crystal panel and the polarization means of the red light and blue light modulation means are disposed on both sides on the optical axis of the green light transmitted through the polarization means of the green light modulation means, sandwiching the optical axis,
Since the blue light and the red light transmitted through the polarizing means are reflected by the combining means and combined on the optical axis of the green light, a matrix type liquid crystal panel of blue light and red light and polarizing means are provided on both sides of the optical axis of the green light. Be placed. Further, a projection optical unit is arranged on the extension of the optical axis of the green light. This makes it possible to configure a projection display device in which the components are arranged in a well-balanced manner and has a sense of stability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an optical drawing of an optical system of a projection type liquid crystal display device according to an embodiment of the present invention. FIGS. 2A and 2B are configuration diagrams of a liquid crystal panel using a TFT according to the present invention. FIG. 3 is a configuration diagram of an optical system of a projection type liquid crystal display device according to a reference example. FIG. 4 is a configuration diagram of an optical system of a projection type liquid crystal display device according to another embodiment of the present invention. FIGS. 5A and 5B are explanatory diagrams of a semi-transmissive mirror using an interference film used in the embodiment. FIG. 6 is an explanatory diagram of a semi-transmissive mirror utilizing a difference in polarization plane. FIG. 7 is a perspective view of the projection type liquid crystal display device of the embodiment. [Description of Signs] 30 semi-transmissive prisms 33 to 35, 56 to 58, 72 to 74 liquid crystal panels 52, 53, 75, 76 semi-transmissive mirror

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Claims (1)

(57) [Claims] First modulation means for modulating red light, second modulation means for modulating green light, third modulation means for modulating blue light, and the first, second and third modulation means, respectively. A synthesizing unit for synthesizing the modulated color light; and a projection optical unit for projecting the light synthesized by the synthesizing unit. Each of the first, second, and third modulating units includes a matrix-type liquid crystal panel, Polarizing means for transmitting the color light emitted from the matrix type liquid crystal panel, and each color light emitted from each of the matrix type liquid crystal panels is incident on the synthesizing means after passing through the respective polarizing means. The projection optical unit is disposed on an extension of the optical axis of the green light transmitted through the polarization unit of the second modulation unit, and the first modulation unit is disposed on both sides of the optical axis of the green light. Matrix liquid crystal panel And a polarization unit, a matrix type liquid crystal panel and a polarization unit of the third modulation unit, and red light transmitted through the polarization unit of the first modulation unit and the polarization unit of the third modulation unit, respectively. And the blue light is reflected by the combining means and combined on the same optical axis as the optical axis of the green light.