JPH1068924A - Projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection type display device which has high picture quality and is easy-to-handle and whose system is compact by making color light transmitted through 1st to 3rd transmission type light valve means incident on a synthesis means, and making the length of optical paths from three transmission type liquid crystal panels to a projection optical means the same. SOLUTION: Polarizing plates 36 to 38 and 39 to 41 and monochrome color filters 42 to 44 are arranged to put the liquid crystal panels 33 to 35 in between. Semitransmitting prisms 30a and 30b are used as a color synthesis means, and the light synthesized in terms of an optical axis by the prisms 30a and 30b is projected to a screen 32 by a lens 31. The center axes of the respective optical paths from the panels 33 to 35 to the lens 31 are on the same plane and the length of the optical paths from the panels 33 to 35 to the lens 31 is made equal. For example, the light from a light source 45 is transmitted through the color filter 42, turned into the red light and made incident on the prism 30a functioning as the color synthesis means through the polarizing plate 41, the panel 33 and the polarizing plate 37.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a projection display device,
In particular, it relates to the structure of the optical system.

[0002]

2. Description of the Related Art Heretofore, 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 born from the fact that a CRT (CRT) itself constitutes a large screen of 26 inches or more, which is physically restricted, and the CRT is a projection television. Since the emitted light is projected as it is, the brightness of the CRT is considerably required. Therefore, it is a very large system in which a special CRT is used with a large amount of electric power and used after cooling, and it is difficult to use it for home use. was there.

[0004] In addition, a projection television using a CRT has insufficient light intensity and insufficient brightness on a 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.

[0005] 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.

[0006] 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 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.

[0008]

According to the present invention, there is provided a projection display apparatus comprising: a first transmission type light valve for modulating a first color light; and a second transmission type light valve for modulating a second color light. Means, third transmissive light valve means for modulating third color light, said first transmissive light valve means, said second transmissive light valve means, and said third transmissive light valve means. A first transmitting light valve, a second transmitting light valve, and a combining unit for combining the respective modulated color lights, and a projection optical unit for projecting the light combined by the color combining unit. Means and the third transmission type light valve means, an incident side polarization means for entering the color light, a transmission type liquid crystal panel for entering the color light transmitted through the incidence side polarization means, and a transmission type liquid crystal panel transmitted through the transmission type liquid crystal panel. An emission-side polarization unit that transmits color light having a specific polarization direction among the light, the first transmission-type light valve unit, the second transmission-type light valve unit, and the third transmission-type light valve. Color light transmitted through each of the emission-side polarizing means of the means is incident on the synthesizing means, and the three transmissive liquid crystal panels have a plurality of pixels arranged in a matrix, and the three transmissive liquid crystal panels The optical path length from the panel to the projection optical means is configured to be the same as each other.

[0009]

FIG. 1 is a block diagram of an optical system of a projection type liquid crystal display according to an embodiment of the present invention. In this embodiment, the polarizing plates 36 to 38 and 39 to 41 and the monochromatic color filter 42 are sandwiched between the liquid crystal panels 33 to 35.
To 44 are arranged. The transflective prisms 30a and 30b are used as color combining means.
The light having undergone the optical axis synthesis in 30 b is projected on a screen 32 by a lens 31. And the liquid crystal panels 33-
The central axis of each optical path from 35 to the lens 31 is 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 and becomes a red light.
1, the light enters the liquid crystal panel 33, and then the polarizing plate 37
And enters the semi-transmissive prism 30a. Similarly, light from the light sources 46 and 47 is applied to the monochromatic color filter 4.
4 and 45, the light becomes green and blue light, and enters the liquid crystal panels 35 and 34 via the polarizing plates 40 and 39.
Then, the semi-transmissive prism 30b is passed through the polarizing plates 36 and 38.
Incident on. 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. Transflective prism 30
The red light incident on a 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 directed to the lens 31.

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 respective optical path lengths from the liquid crystal panels 33 to 35 to the lens 31 are arranged to be 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 image forming position when the optical path length changes. For example, assuming that the object A is imaged on the screen 32 by the lens 31, if the position of the object A 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 lens 3 is moved from the liquid crystal panels 33 to 35 to the lens 3.
Are arranged so that each optical path length up to 1 is equal,
Since the image formation positions of the red, green, and blue color lights coincide with each other, the arrangement is such that a high-quality image can be obtained without color blurring or the like.

The liquid crystal panels 33 to 35 are basically of a TN (Twisted Nematic) type and are composed of a liquid crystal material and a glass plate sandwiching the liquid crystal material from both sides, and when a voltage is applied to the liquid crystal. , Its transmittance changes to function as a liquid crystal shutter. The TN method is excellent in contrast, gradation, response speed, transmittance, life, and the like, and may be a reflection type or a transmission type. In particular, 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. 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. 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 TFT) is used.

Since this TFT is a thin film and is driven in a static manner, it has excellent contrast, gradation, and responsiveness, and has an 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, stability, and the like.

The transmission type liquid crystal panels 33 to 35 are used, and the configuration of the optical system is extremely simple.

In this embodiment, the liquid crystal panel 3
Since a three-panel projection method using three to 35 is used, and light from the liquid crystal panels 33 to 35 is combined, 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 need not be a finely arranged three color filter but may be a single color solid filter. Pixel defects due to overlapping three liquid crystal panel pixels at the same position in the projected image are eliminated. Since there is very little possibility that all three images will be generated at the same position, there is an advantage that fixed pixel defects can be erased.

The liquid crystal panel 3 is arranged on one axis of the lens 31.
Lights of 3 to 35 are combined, and the operation of simply focusing on the lens by simply operating the lens, even when the distance from the lens to the screen or the projection size is changed, is simplified.

The liquid crystal panels 33 to 35 are arranged at right angles to each other, and the reflecting surfaces of the transflective prisms 30a and 30b are arranged at right angles. Since the color lights from the shifted directions can be combined into one light beam, the layout of the optical system when it is made into a product 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 very high and ranges from 101x to 5001,1x. On the other hand, TFT
Is a semiconductor, so when light enters, an electromotive force is generated,
Even when the transistor 13 is off, the transistor 13 approaches the on state due to the photocurrent, and the contrast of the display screen is significantly reduced. Usually, the illuminance at which the decrease in contrast starts to occur is about 101,000x 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, color filters 42 to 44 are arranged on the side of the light sources 45 to 47 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, TFT
Since light is always incident on the surface through the color filter and the glass substrate, the amount of blue and green light is equivalently reduced to 1/10 or less, and the amount of red light is reduced to 1/5. ,
Induction of the photocurrent of the TFT due to intense light incidence is suppressed, and the development that makes the image contrast low and difficult to see can be prevented.

FIG. 4 is a structural view 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 synthesizing means.
For example, light from the light source 62 is incident on the color filter 59 and red light is transmitted therethrough. Red light is transmitted through the liquid crystal panel 56 (a polarizing plate is omitted) and then transmitted through the semi-transmissive mirror 52. . 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 from the semi-transmissive mirror 52 are
0 is synthesized on one axis, 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, since the liquid crystal panels 56, 57, 58 are arranged in parallel and the semi-transmissive mirrors 52, 53 are arranged in parallel, color lights from the same direction can be combined into one light flux. Since the optical path can be folded inward, the arrangement of the optical system in a product can be neat and compact.

FIG. 5 is a structural view 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 synthesizing 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 applied to a liquid crystal panel 74 (a polarizing plate is omitted).
After being modulated by, the light is incident on the 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 to form a semi-transmissive mirror 76.
Incident on.

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 lights incident on the semi-transmissive mirror 76 are transmitted, the red light is reflected, and the green, blue and red lights are color-combined and directed to the lens 70, and the screen 70
Projected on

Also in this embodiment, the central axes of the optical paths from the lens 70 to the liquid crystal panels 72, 73, 74 are on the same plane, and the optical path lengths are the same.

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 in FIG. 1).
7, 48, semi-transmissive mirrors 52 and 53 in FIG. 4, and semi-transmissive mirrors 75 and 76 in FIG. 5). 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. 6A shows an optical glass 80 on which an interference film 81 is formed.
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. 7 is an explanatory view of a semi-transmissive mirror using a polarization plane. The TN liquid crystal is displayed on a screen using a polarizing plate, and light incident on a human eye from a 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.・ Green / Blue 3
Color light of the colors can be synthesized without loss, and the light use efficiency is improved.

FIG. 8 is an external view of the projection type image display device manufactured using the liquid crystal panel as described above.
The light beam 88 emitted from the projection body 86 having the optical system shown in FIG. 4 or 5 is projected on a screen 87.

[0034]

As described above, according to the present invention, the following effects can be obtained.

(A) Since a transmission type liquid crystal panel is used, a polarizing beam splitter as in the case of the reflection 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 means, its light intensity is about 1/3 of that of white light, and the temperature rise of the incident side polarizing means is suppressed. Therefore, the life of the incident side polarizing means 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 generated by the incident side polarizing means.

After the color light is transmitted through each transmission type liquid crystal panel, the output side polarizing means is provided to polarize the color light. Before performing the process, the intensity of the color light at each pixel can be determined by the respective output-side polarization means, and an image of each color light with good contrast can be formed. The contrast of the synthesized image can be improved.

(C) Since the images generated by the respective transmissive liquid crystal panels are combined and projected by the combining means, the projection optical means can be simply changed even if the distance from the projection optical means to the screen or the projection size is changed. Focusing can be performed only by the operation of, and the operation is simplified.

(D) The optical path lengths from the three transmissive liquid crystal panels to the projection optical means are configured to be the same, and are synthesized and projected. Therefore, the magnitude of the luminous flux of each color light at the position of the projection optical means Are substantially the same, the in-screen intensity distribution in the projection screen is the same for each color light, and the size of the luminous flux is almost the same for each color light, so that the pixels of the three liquid crystal panels are easily aligned 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 apparatus 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 applied 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 utilizing a difference in polarization plane.

FIG. 8 is a perspective view of the projection type liquid crystal display device of the embodiment.

[Explanation of symbols]

33-35, 56-58, 72-74 ... liquid crystal panels 30a, 30b ... transflective prisms 52, 53, 75, 76 ...・ Translucent mirror

Claims (1)

[Claims] 1. A first transmission type light valve means for modulating a first color light, a second transmission type light valve means for modulating a second color light, and a third transmission light for modulating a third color light. A type light valve means; a synthesizing means for synthesizing each color light modulated by the first transmission type light valve means, the second transmission type light valve means, and the third transmission type light valve means, respectively, Projection optical means for projecting the light synthesized by the color synthesis means, wherein the first transmission type light valve means, the second transmission type light valve means, and the third transmission type light valve means comprise: Incident-side polarization means for entering color light, a transmission-type liquid crystal panel for entering color light transmitted through the incidence-side polarization means, and emission for transmitting color light in a specific polarization direction among the color lights transmitted through the transmission-type liquid crystal panel Polarizing means, respectively, and the color light transmitted through the output side polarizing means of each of the first transmission type light valve means, the second transmission type light valve means, and the third transmission type light valve means The three transmissive liquid crystal panels have a plurality of pixels arranged in a matrix, and the optical path lengths from the three transmissive liquid crystal panels to the projection optical means are the same. A projection display device characterized in that the projection display device is configured as follows.