JP2650184C - - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a projection display device, and more particularly to a structure of an optical system thereof. [0002] Conventionally, as a projection type display device, there has been a movie, a slide, or a CRT projection television. Movies and slides project an image printed on film, and because of the restriction of projecting using film as a medium, images cannot be viewed online with respect to an input signal. [0003] On the other hand, a projection television using a CRT is a system that was born from the fact that a CRT (CRT) itself constitutes a large screen of 26 inches or more, which is physically limited. Since the light emitted from the CRT is directly projected, the brightness of the CRT is considerably required. Therefore, a special CRT is used with a large electric power and is used for cooling, which is a very large system, and is difficult to use for home use. There was a problem. [0004] In addition, the projection television using a CRT has insufficient light intensity and insufficient brightness on the screen, and the screen position and the system position are finely 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 is equipped with a special and large CRT, a special power supply and an adjustment system,
There was a problem that the cost was considerably high. [0006] The conventional projection display device has the above-mentioned problems, and its use has been delayed because the advantages of the large-screen television or the projection television cannot be fully utilized. The present invention has been made to solve such a problem, and an object of the present invention is to provide a projection display apparatus which has high image quality, is easy to handle, and has a compact system. [0008] A projection display apparatus according to the present invention includes a first transmissive light valve unit that receives red light, modulates the red light to generate an image, and a green light. A second transmissive light valve means that receives light and modulates the green light to generate an image; a third transmissive light valve means that receives blue light and modulates the blue light to generate an image; Synthesizing means for synthesizing the images generated by the first transmissive light valve means, the second transmissive light valve means, and the third transmissive light valve means; and synthesizing the image synthesized by the synthesizing means. Projection optical means for projecting, the first transmission type light valve means, the second transmission type light valve means, and the third transmission type light valve means, , A transmission-type liquid crystal panel that receives the color light that has passed through the side-polarization plate; and an emission-side polarization plate that transmits color light in a specific polarization direction among the color lights that have passed through the transmission-type liquid crystal panel. Color light transmitted through the output side polarizing plate of each of the mold type light valve means, the second transmission type light valve means, and the third transmission type light valve means is incident on the synthesizing means; The panel sandwiches a twisted nematic liquid crystal between a pair of substrates, and a plurality of pixels having a liquid crystal driving electrode formed on one of the substrates,
An active matrix transmissive liquid crystal panel having a plurality of thin film transistors formed on the one substrate and connected to the plurality of liquid crystal drive electrodes, wherein the color light transmitted through the incident side polarizing plate is provided on the other substrate side. , The light is incident on the one substrate on which the plurality of thin film transistors are formed, and then emitted from the one substrate side, and the three transmissive liquid crystal panels have the same resolution as each other. A plurality of pixels, wherein the optical path lengths from the three transmissive liquid crystal panels to the projection optical unit are configured to be the same as each other, and the synthesizing unit converts the three color lights incident on the same optical axis. It is characterized by being synthesized. In the present invention, the transmissive light valve means has a configuration in which a TN type transmissive liquid crystal panel is disposed between the incident-side polarizing plate and the outgoing-side polarizing plate. The color light whose intensity has been reduced to about 1/3 thereof is incident on the incident-side polarizing plate of each transmission type light valve means. Heat generation in the polarizing plate is suppressed. Therefore, the life of the incident side polarizing plate can be extended. In addition, it is possible to suppress a decrease in contrast in the liquid crystal panel due to an influence of a temperature rise due to heat generation of the incident side polarizing plate. In addition, after the color light is transmitted through each transmission type liquid crystal panel of the TN mode, the output side polarizing plate is provided to polarize the color light. Before the light is diffused, by each output side polarizing plate,
Since the intensity of the color light at each pixel can be determined and an image of each color light having good contrast can be formed, the contrast of a combined image obtained by combining three color light images can be improved. In addition, since the color light whose intensity is reduced to about 1/3 of that of the white light is further reduced by the incident side polarizing plate and then enters the transmission type liquid crystal panel, the thin film transistor generated due to the light is generated. Light leakage can be reduced. Therefore, it is possible to not only suppress the heat generation in the incident-side polarizing plate but also suppress the leak current of the thin film transistor and improve the image quality. Further, each of the transmissive liquid crystal panels of the TN mode receives white light by arranging so that color light enters from the substrate side opposite to the substrate on which the thin film transistor is formed and exits from the substrate side on which the thin film transistor is formed. The light intensity reduced to approximately one third of the light intensity is further reduced through the incident side polarizing plate, and further, the light is incident from the side of the liquid crystal panel substrate on which the thin film transistor is not formed. Since the dropping configuration is employed, light leakage in the thin film transistor can be significantly reduced. Further, in the present invention, the three transmissive liquid crystal panels have pixels of the same resolution, and the optical path lengths from the three transmissive liquid crystal panels to the projection optical means are configured to be the same, Furthermore, since the color lights transmitted through the output side polarizing plates of each light valve are combined on the same optical axis, the pixels of the three transmissive liquid crystal panels are combined so as to be at the same position on the combined image. You. Therefore, reliable additive color mixing of the three color lights can be realized at each pixel position of the composite image. Further, the three transmissive liquid crystal panels have pixels having the same resolution, and the optical path lengths between the liquid crystal panel and the projection optical means are the same for each color light. Since they are combined and projected on the same optical axis, the luminous flux of each color light is substantially the same, and the in-screen intensity distribution in the projection screen on the screen is the same for each color light. Furthermore, if the size of the luminous flux is almost the same, it becomes easy to align the pixels of the three transmissive liquid crystal panels at the same position. Therefore, a high-quality image without color unevenness and with good color reproducibility can be obtained. 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, the polarizing plates 36 to 38 are sandwiched between the liquid crystal panels 33 to 35.
, 39-41 and monochromatic color filters 42-44. Transflective prisms 30a and 30b are used as color combining means, and transflective prisms 30a and 30b are used.
The light having undergone the optical axis synthesis is projected on a screen 32 by a lens 31.
The central axes of the optical paths from the liquid crystal panels 33 to 35 to the lens 31 are on the same plane, and the optical paths are arranged so that the optical path lengths from the liquid crystal panels 33 to 35 to the lens 31 are equal. For example, the light from the light source 45 passes through the monochromatic color filter 42 to become red light, enters the liquid crystal panel 33 via the polarizing plate 41, and then enters the semi-transmissive prism 30 a via the polarizing plate 37. Incident. Similarly, the lights from the light sources 46 and 47 pass through the monochromatic color filters 44 and 45 to become green and blue lights, enter the liquid crystal panels 35 and 34 via the polarizing plates 40 and 39, and thereafter, Polarizing plates 36, 38
And enters the semi-transmissive prism 30b. 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
0a. 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 combined with the optical axis of the lens 31 and Pointed. In each of the liquid crystal panels 33, 35, and 34, in the case of a television signal, a color-demodulated video signal is input to a panel on which a corresponding filter is arranged, and the transmittance is controlled there. The light directed to the lens 31 is subjected to color adjustment, enlarged by the lens 31 and projected on the screen 32. In this embodiment, the optical paths from the liquid crystal panels 33 to 35 to the lens 31 are arranged so as to have the same optical path length.
Matches above. FIG. 2 is an explanatory diagram of an image forming position when the optical path length changes. For example, assuming that the subject A is imaged on the screen 32 by the lens 31, if the position changes to the position of the subject A ', an image is formed on the screen 32a by the lens 31. As described above, when the position of the subject changes, the image formation position also changes. In this embodiment, as described above, the optical path lengths from the liquid crystal panels 33 to 35 to the lens 31 are arranged so as to be equal. Since the image formation positions of the green and blue color lights coincide with each other, the arrangement is such that high-quality images can be obtained without color blurring or the like. The liquid crystal panels 33 to 35 are of a TN (twisted nematic) type,
It is composed of a liquid crystal material and a glass plate sandwiching it from both sides. The TN method is excellent in contrast, gradation, response speed, transmittance, lifetime, and the like. When the transmission type is used, the optical system is simplified. FIG. 3 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. Liquid crystal is usually difficult to multiplex,
Therefore, the number of scanning lines used was small and the resolution had to be reduced, but the drawback was solved by the active matrix system as shown in FIG. The transistor 10 is turned on by the timing line 12 corresponding to the scanning line, and the display data is written to the liquid crystal drive electrode 11 arranged in the pixel via the data line 13. After that, 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 TF) is used.
T) is used. Since this TFT is a thin film and is driven in a static manner, contrast, gradation,
There is an advantage that the responsiveness is excellent and the number of pixels can be increased, so that high resolution is increased. 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, stability, and the like. The liquid crystal panels 33 to 35 are of a transmission type, and the configuration of the optical system is extremely simple. Further, in this embodiment, a three-panel projection method using the liquid crystal panels 33 to 35 is used, and light from the liquid crystal panels 33 to 35 is combined, so that the original light amount can be reduced. Further, since the panels have the same resolution, the resolution is improved three times as compared with the one-panel system. In addition to these advantages, the color filter may be a solid filter of a single color instead of a fine arrangement of three colors, and it is very unlikely that all three pixels will have pixel defects at the same position. There are advantages such as erasing. Further, the light of the liquid crystal panels 33 to 35 is combined on one axis of the lens 31, and the focus can be changed simply by operating the lens, even when the distance from the lens to the screen or the projection size is changed. The operation of matching is simplified. The liquid crystal panels 33 to 35 are arranged at right angles to each other, and the transflective prism 30
Since the reflecting surfaces of a and 30b are arranged at right angles, the configuration of the optical system becomes compact, and color light from directions shifted by 90 ° from each other can be combined into one light flux. The layout of the system is neat. In this embodiment, since the images of 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 is extremely high, and ranges from 100,000 lx to 500,000 lx. 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 13 is in an off state, the transistor 13 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 this embodiment, the color filters 42 to 44 are arranged on the light sources 45 to 47 side with respect to the liquid crystal panels 33 to 35 in order to prevent a decrease in contrast due to the light. When a color filter is incorporated in a liquid crystal panel, this can be achieved by disposing the color filter layer on the light source side of the liquid crystal material and disposing the glass substrate on which the TFT is mounted on the projection lens side of the liquid crystal material. As a result, light through the color filter and the glass substrate is always incident on the TFT surface, so that blue and green light are equivalent to 1 light.
/ 10 or less, and even red light is reduced to 1/5, and the induction of photocurrent in the TFT due to intense light incidence is suppressed, and the development of the image contrast is reduced and it is difficult to see. Can be. FIG. 4 is a configuration diagram of an optical system of a projection display apparatus according to another embodiment of the present invention.
In this embodiment, semi-transmissive mirrors 52 and 53 are used as color combining means. For example, light from the light source 62 is incident on the color filter 59 and red light is transmitted therethrough. Red light passes through a liquid crystal panel 56 (a polarizing plate is omitted), and then is transmitted through a semi-transmissive mirror 52.
Through. The light from the light source 63 is incident on the color filter 60 and the green light is transmitted therethrough. The green light is transmitted through the liquid crystal panel 57 (the polarizing plate is omitted) and then transmitted through the semi-transmissive mirror 53. After being further reflected by the total reflection mirror 55, the light is again reflected by the transflective mirror 52. The light from the light source 64 is incident on the color filter 61 and the blue light is transmitted therethrough. The blue light is reflected by the total reflection mirror 54 after passing through the liquid crystal panel 58 (the polarizing plate is omitted). Thereafter, the light is further reflected by the transflective mirror 53, reflected by the total reflection mirror 55, and then reflected again by the transflective 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 one axis of the lens 50, enlarged by the lens 50, and projected on the screen 51. Also in this embodiment, the central axes of the optical paths from the lens 50 to the liquid crystal panels 56, 57, 58 are on the same plane, and the optical path lengths are the same. Further, the liquid crystal panels 56, 57, 58 are arranged in parallel, and
Since 2, 53 are arranged in parallel, color light from the same direction can be combined into one light beam, and the optical path can be folded inward, so that the arrangement of the optical system when it is made into a product is simple, Can be compacted. FIG. 5 is a configuration diagram of an optical system of a projection display apparatus according to another embodiment of the present invention.
This embodiment is an example in which semi-transmissive mirrors 75 and 76 are used as color combining means. 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 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 light that has entered the semi-transmissive mirror 76 is transmitted, the red light is reflected, and the green, blue, and red lights are color-combined and directed to the lens 70,
0 is projected on the screen 71. Also in this embodiment, the central axis of the optical path from the lens 70 to each of the liquid crystal panels 72, 73, 74 is on the same plane, and the optical path lengths are the same. In each of the above embodiments, a color is synthesized by inserting a semi-transmissive film in the optical path (for example, semi-transmissive films 47 and 48 in FIG. 1, semi-transmissive mirrors 52 and 53 in FIG. 4, and FIG. 5). Semi-transmissive mirrors 75, 76). 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, it is possible to cope with the fact that each of the three light beams has a different wavelength from red, green, and blue, or that it is polarized due to the properties of the TN liquid crystal. FIG. 6A is an explanatory diagram of a semi-transmissive mirror in which an interference film 81 is formed on an optical glass 80. FIG. 2B is a characteristic diagram thereof. The interference film 81 transmits, for example, red light,
There is a property of reflecting light other than red light. As a result, for example, red light is transmitted and green light is reflected, so that red and green light can be combined without light loss. In this method, 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. 7 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, both the transmittance and the reflectance can be increased by appropriately selecting the polarization reflection surface and the polarization axis of the incident color light, and by using the color combining means utilizing the wavelength selection characteristics. -The three color lights of green and blue can be combined without loss, and the light use efficiency can be improved. FIG. 8 is an external view of a projection type image display device manufactured using a liquid crystal panel as described above, and a light beam emitted from a projection main body 86 incorporating the optical system of FIG. 1, FIG. 4 or FIG. 88 is projected on a screen 87. As described above, according to the present invention, the following effects are obtained. (A) Since a transmissive liquid crystal panel is used, a polarizing beam splitter as in the case of the reflective type is not required, 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 three-panel projection system is adopted, the following advantages are provided. Since each color light is incident on the incident-side polarizing plate, its light intensity is approximately １ ／ of that of white light, and the temperature rise of the incident-side polarizing plate is suppressed. Therefore,
The life of the incident side polarizing plate can be extended. Further, it is possible to suppress a decrease in contrast in the transmission type liquid crystal panel due to an influence of a temperature rise due to heat generation in the incident side polarizing plate. After the color light is transmitted through each transmissive liquid crystal panel of the TN mode, the output side polarizing plate is provided to polarize the color light. Before performing this operation, the intensity of the color light at each pixel can be determined by the respective output-side polarizing plates, and an image of each color light with good contrast can be formed. The contrast of the synthesized image can be improved. Furthermore, if the liquid crystal panel has the same resolution, the resolution is improved three times as compared with the one-panel system. In addition, since it is not a juxtaposed additive color mixture utilizing the resolution of the human eye but a complete additive wet color, a good color reproduction can be obtained even when the projected image is viewed from a close place and the magnification is large. Even if there is a pixel defect in the liquid crystal panel, there is a very small possibility that three pixel defects will occur at the same position, so that there is an advantage that fixed pixel defects can be eliminated. (C) After reducing the light intensity of the color light, which has been reduced to approximately one-third the light intensity of the white light, by the incident-side polarizing means, the light is transmitted to a transmission type liquid crystal panel using a twisted nematic liquid crystal. Since the light is incident, light leakage of the thin film transistor caused by light can be reduced. Therefore, it is possible to improve the image quality by suppressing not only the heat generated by the incident side polarizing means but also the leak current of the thin film transistor. In addition, each of the transmissive liquid crystal panels is arranged so that color light is incident on the substrate side opposite to the substrate on which the thin film transistor is formed, and is emitted from the substrate side on which the thin film transistor is formed, so that approximately 1/1 of the white light. 3, the light intensity is further reduced through the incident side polarizing means, and the light is further incident upon light from the side of the liquid crystal panel substrate where the thin film transistor is not formed. Since this is adopted, light leakage in the thin film transistor can be greatly reduced. (D) The images generated by the respective transmissive liquid crystal panels are synthesized on the same optical axis by the synthesizing means and are projected. Focusing can be achieved by simply operating the projection optical means, and the operation is simplified. (E) The three transmissive liquid crystal panels have pixels of the same resolution, and the optical path lengths from the projection optical means to the respective transmissive liquid crystal panels are configured to be the same,
Further, since the images of the respective color lights are synthesized and projected on the same optical axis, the size of the luminous flux of the respective color lights at the position of the projection optical means is substantially the same, so that the intensity distribution within the screen on the projection screen is different between the respective color lights. And the size of the luminous flux is substantially the same for each color light, it is easy to align the pixels of the three liquid crystal panels at the same position. Therefore, a high-quality image without color unevenness and with good color reproducibility can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of an optical system of a projection display device according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of an optical path length. FIG. 3 is a characteristic diagram showing a relationship between the intensity of light emitted to a TFT of a liquid crystal panel and contrast. FIG. 4 is a configuration diagram of an optical system of a projection display apparatus according to another embodiment of the present invention. FIG. 5 is a configuration diagram of an optical system of a projection display device according to another embodiment of the present invention. FIGS. 6A and 6B are explanatory diagrams of a semi-transmissive mirror using an interference film used in the embodiment. FIG. 7 is an explanatory diagram of a semi-transmissive mirror using a difference in polarization plane. FIG. 8 is a perspective view of the projection type liquid crystal display device of the embodiment. [Explanation of reference numerals] 33 to 35, 56 to 58, 72 to 74 ... liquid crystal panels 30a, 30b ... transflective prisms 52, 53, 75, 76 ... .... Semi-transparent mirror

Claims (1)

Claims: 1. A first transmissive light valve means for receiving red light and modulating the red light to generate an image, and receiving green light and modulating the green light to form an image. A second transmission type light valve means for generating blue light, a third transmission type light valve means for modulating the blue light and generating an image, the first transmission type light valve means, The second transmission type light valve means and the third transmission type light valve means, a combination means for combining the images generated by the light means, and a projection optical means for projecting the image combined by the combination means, The first transmission type light valve means, the second transmission type light valve means, and the third transmission type light valve means each include an incident-side polarizing plate for receiving the color light, and a color light transmitted through the incident-side polarizing plate. Incident transmission type An emission-side polarizing plate that transmits color light of a specific polarization direction among the color lights transmitted through the transmission-type liquid crystal panel, the first transmission-type light valve means, and the second transmission-type light. The color light transmitted through the respective output-side polarizers of the valve means and the third transmission type light valve means is incident on the synthesizing means. Each of the transmission type liquid crystal panels has a twisted nematic type between a pair of substrates. A plurality of pixels sandwiching liquid crystal and having a liquid crystal drive electrode formed on one of the substrates,
An active matrix transmissive liquid crystal panel having a plurality of thin film transistors formed on the one substrate and connected to the plurality of liquid crystal drive electrodes, wherein the color light transmitted through the incident side polarizing plate is provided on the other substrate side. , The light is incident on the one substrate on which the plurality of thin film transistors are formed, and then emitted from the one substrate side, and the three transmissive liquid crystal panels have the same resolution as each other. A plurality of pixels, wherein the optical path lengths from the three transmissive liquid crystal panels to the projection optical unit are configured to be the same as each other, and the synthesizing unit converts the three color lights incident on the same optical axis. A projection display device characterized by being synthesized.