JPH05303070A - Liquid crystal projector - Google Patents

Abstract

PURPOSE:To constitute the liquid crystal projector which can display a satisfactory image, of a miniature device by a miniature optical system. CONSTITUTION:In the liquid crystal projector by which liquid crystal panel 29R, 29G and 29B are irradiated with an illuminating light, a transmission light by image displayed on the liquid crystal panel 29R, 29G and 29B is projected on a prescribed screen by a projection lens 33, and the image is displayed on the screen, the transmission light is reduced by a relay 30, formed as a reduced image on the surface of a field lens 32, and an image light of this reduced image is made incident on the projection lens 33, and also, the projection lens 33 is arranged so as to be movable in parallel to an optical axis, and moreover, so that an emitted light of the projection lens 33 can be curved by a mirror 34 in accordance with a position of the screen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projector that projects an image on a screen using a liquid crystal panel.

[0002]

2. Description of the Related Art Conventionally, as a projection type color image display device, a so-called liquid crystal projector using a liquid crystal panel has been developed. In this liquid crystal projector, light from a light source such as a xenon lamp is converted into parallel rays by an optical member, and then separated into three colors of red light, green light, and blue light by a dichroic mirror, and separated into respective optical paths. Place the LCD panel. Then, a red image, a green image and a blue image of the projected image are formed on the liquid crystal panel of each optical path, and the light rays of each optical path are converted into red image light,
After forming the green image light and the blue image light, the respective image lights are combined by a dichroic mirror, and the combined light is enlarged and projected on a screen through a projection lens.

In a liquid crystal projector having a simple structure, a color image is displayed on one liquid crystal panel, and light from a light source is incident on this one liquid crystal panel without color separation. Some display the transmitted light of the panel directly on the screen.

With such a configuration, the conventional CRT
Unlike a projector that uses a light source such as an image display unit that also serves as a light source, the liquid crystal panel that is the image display unit and the light source are separate units, so a high-luminance image that corresponds to the brightness of the light source And the resolution is determined by the liquid crystal panel, so that it is possible to project an image with high brightness and high resolution.

[0005]

In the case of this type of liquid crystal projector, in order to increase the resolution of the image displayed on the screen, it is necessary to increase the number of pixels of each liquid crystal panel. In order to realize a projector, it is necessary to use a large liquid crystal panel with many pixels. However, when a large liquid crystal panel is used, there is an inconvenience that a large lens having a large diameter is required as a projection lens for projecting the image light transmitted through the liquid crystal panel, and the size of the optical system of the projector becomes large. At the same time, a lens having a large diameter is very expensive, which increases the manufacturing cost of the projector.

On the other hand, in the case of this type of liquid crystal projector, when the projection light output from the projector is projected on the screen, the positional relationship between the projector and the screen needs to be appropriately maintained, and when the proper arrangement is not performed. However, there is an inconvenience that trapezoidal distortion occurs in the displayed image. That is, for example, as shown in A of FIG.
The image light output from the projection unit 2 of the projector 1 is projected and displayed on the screen 3 for use. When the projector 1 is properly set, an image without distortion is displayed on the screen 3. On the other hand, for example, as shown in B of FIG.
If the height is lower than the specified position, the image displayed on the screen 3 may be distorted into a trapezoid.

Although it is theoretically impossible to optically correct the distortion due to the tilt, there is a disadvantage that an optical component such as a large lens is required to completely correct the distortion.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a liquid crystal projector capable of displaying a good image without distortion by using a small optical component having a small diameter.

[0009]

According to the present invention, for example, as shown in FIG. 1, illumination light is supplied to liquid crystal panels 29R, 29G, 29.
In the liquid crystal projector that irradiates B and projects the transmitted light by the image displayed on the liquid crystal panels 29R, 29G, 29B on the predetermined screen by the projection lens 33, and displays the image on the screen, the transmitted light is reduced by the relay lens 30. Then, a reduced image is formed on the lens surface of the field lens 32, the image light of this reduced image is made incident on the projection lens 33, and the projection lens 33 is movably arranged parallel to the optical axis. The light emitted from 33 can be bent by a mirror 34 according to the position of the screen.

Further, in this case, the field lens 32
Is moved in parallel with the optical axis in conjunction with the parallel movement of the projection lens 33.

[0011]

According to the present invention, the image is reduced by the relay lens 30 to form a reduced image on the surface of the field lens 32, so that the projection lens 33 having a small diameter can be used, and the optical system can be downsized. Together with the projection lens 33
Since the lens can be moved in parallel with the optical axis, distortion due to tilting can be corrected.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In this example, the liquid crystal projector is a three-plate three-primary-color separation / synthesis type liquid crystal projector capable of projecting in two directions.
When the appearance is shown in FIG. 3, reference numeral 10 in the figure shows the entire liquid crystal projector, and the projector 10 has an opening 11 through which projection light is output on the upper surface and an opening through which projection light is output on one side surface. It has a part 12.

1 and 2 show the inside of the projector 10, the light from the light source 21 such as a metal halide lamp is converted into parallel rays by the reflecting mirror 22, and the parallel rays are used as illumination light in the first dichroic. Mirror 2
3. Then, with this first dichroic mirror 23, the green component is made to go straight from the light from the light source 21,
The other color components are bent 90 °. Then, the bent color components are made incident on the second dichroic mirror 24.
In the second dichroic mirror 24, the red component is bent 90 ° from the color component from which the green component has been removed, and the remaining blue component goes straight.

Then, the first dichroic mirror 23
After bending the green component separated in step 90 by the mirror 27, the green component is projected through the liquid crystal panel 29G for green on which the green component of the projected color image is displayed, and the green image light formed by the transmission is converted into the third image light. It is incident on the dichroic mirror 25. Further, the red component separated by the second dichroic mirror 24 is transmitted through the red liquid crystal panel 29G displaying the red component of the color image to be projected, and the red image light formed by the transmission is transmitted to the third dichroic mirror. Two
5. Then, the third dichroic mirror 25 combines the light transmitted through the red liquid crystal panel 29G and the light transmitted through the green liquid crystal panel 29G, and causes the combined light to enter the fourth dichroic mirror 26. Further, the blue component separated by the second dichroic mirror 24 is transmitted through the blue liquid crystal panel 29B on which the blue component of the color image to be projected is displayed, and the blue image light formed by the transmission is reflected by the mirror 28 at 90 °. After bending, the 4th
It is incident on the dichroic mirror 26. Then, in the fourth dichroic mirror 26, the combined light of the red component and the green component from the third dichroic mirror 25,
The light of the blue component transmitted through the blue liquid crystal panel 29B is combined, and the color image light in which the three primary colors are combined is combined with the relay lens 3
It is incident on 0.

Here, in this example, as the liquid crystal panels 29R, 29G, and 29B of the respective colors, those in which the diagonal line of the displayed image is 3 inches are used. Here, the drive circuits for the liquid crystal panels 29R, 29G, and 29B of the respective colors are omitted.

In the relay lens 30, the image size of the color image light in which the three primary colors are combined is reduced to 1/3,
The image light that has been reduced to 1/3 is rotated 90 ° by the mirror 31.
After bending, it is formed as a reduced image on the lens surface of the field lens 32. And this field lens 3
Image light of a reduced image of 1/3 formed on the second lens surface is made incident on the projection lens 33.

In this case, in this example, the field lens 32 and the projection lens 33 are arranged so as to be movable parallel to the optical axis, and the positions of both lenses 32 and 33 are changed by the tilt correction described later. It is designed to move in parallel. However, the amount of movement differs between the lenses 32 and 33.

A mirror 34 is movably arranged on the emission side of the projection lens 33, and the image light emitted from the projection lens 33 is moved by the arrangement position of the mirror 34 to the opening 11 side or the side opening. The light is emitted from the 12 side. That is, when the mirror 34 is rotated about the fulcrum 34b of the support member 34a and is arranged in the optical path of the image light output from the projection lens 33 (the position shown by the solid line in FIG. 2), the side surface is bent 90 °. Is projected from the side of the opening 12. Further, when the mirror 34 is rotated to be removed from the optical path of the image light output from the projection lens 33 (the position indicated by the broken line in FIG. 2),
The image light output from the projection lens 33 travels straight and is projected from the opening 11 on the upper surface. The openings 11 and 12
Protective glasses 35 and 36 (or filters) are attached to the.

Image light from the opening 11 or 12 reaches a screen (not shown) to display a color image on the screen. Then, when the displayed image has a trapezoidal distortion as shown in B of FIG. 7, the positions of the field lens 32 and the projection lens 33 are adjusted so that the distortion as shown in A of FIG. It is possible to display a rectangular image that does not exist.

Here, the correction of the distortion due to the tilt of the image displayed on this screen will be described with reference to FIGS. 4 and 5. FIG. 4 and FIG.
FIG. 4 is a diagram showing a state in which the images displayed on 29G and 29B are displayed on the screen 3. In FIG. 4, the optical axis 1 of the optical system of the projector coincides with the center of the screen 3, and the optical axis 1 is orthogonal to the screen 3. FIG. 5 shows the screen 3
Shows the state in which the center of is above the optical axis l of the optical system of the projector. 4 and 5 show the optical paths from the liquid crystal panels 29R, 29G, 29B to the screen 3 assuming that they are straight lines. Mirrors and the like are omitted, and the liquid crystal panels 29R, 29G, 29B are not shown. The state in which the displayed liquid crystal panel display image m is projected on the screen 3 as an enlarged projection image m ′ is shown.

First, when the optical axis l of the optical system of the projector is aligned with the center of the screen 3, the centers of the relay lens 30, the field lens 32 and the projection lens 33 are aligned with the optical axis l as shown in FIG. Let By doing so, the enlarged image m ′ is displayed on the screen 3 without distortion. On the lens surface of the field lens 32, the liquid crystal panel display image m is a reduced image m ″ having a size of 1/3.

Then, as shown in FIG. 5, the screen 3
When the center of the projector is located above the optical axis l of the optical system of the projector, the optical axis l can be aligned with the center of the screen 3 by slightly tilting the installation state of the projector. However, when the center of the screen and the optical axis 1 are forced to coincide with each other in this way, the intersecting state of the optical axis 1 and the screen 3 is not orthogonal. In projection in such a state that the optical axis 1 is not orthogonal to the screen 3, trapezoidal distortion (B in FIG.
(See) occurs.

In this example, the inclination of the projector body does not direct the projection light to the screen 3, but the field lens 32 and the projection lens 33.
It is adjusted by parallel movement with respect to the optical axis l. That is, FIG.
As shown in FIG.
And are moved slightly upward with respect to the optical axis l so that the enlarged projection image m ′ is displayed on the screen 3. At this time, the projection lens 33 has a larger displacement amount with respect to the optical axis 1 than the field lens 32. The field lens 32 'and the projection lens 33' shown by broken lines in FIG.
Indicates the position where the center of each lens is aligned with the optical axis l.

Although FIG. 5 shows the adjustment state when the screen is raised upward, it can be adjusted when the screen is pushed downward, leftward, or rightward. This can be dealt with by translating the field lens 32 and the projection lens 33 in the same direction.

As described above, according to the liquid crystal projector of this example, the trapezoidal distortion due to the tilt can be easily corrected by the parallel movement of the field lens 32 and the projection lens 33. In this case, the relay lens 30 causes the field lens 32
By making a reduced image on the lens surface of, the field lens 32 and the projection lens 33 can be made small in diameter, the optical system of the liquid crystal projector can be made compact, and the image can be obtained even if they are moved in parallel. It is possible to easily realize a configuration in which light is not blocked. That is, when the reduced image is not used, it is necessary to use a lens having a very large diameter in order to prevent the projected image light from being completely shaded even if the projection lens 33 is moved in parallel. Although the optical system of the projector becomes very expensive, the configuration as in this example makes it possible to provide a small and inexpensive optical system using a lens with a small diameter.

Since the trapezoidal distortion due to the tilt can be easily corrected as described above, there is no restriction on the installation place of the liquid crystal projector. That is, in the conventional liquid crystal projector, a dedicated liquid crystal projector is prepared for projecting from a low position such as on the floor and for projecting from a high position by hanging it from the ceiling. And a single projector can be used together, and there is no restriction on the installation location of the liquid crystal projector.

Further, by forming a reduced image on the lens surface of the field lens 32, the projection lens 33 can be a small lens which is a small lens device, and can be displayed as, for example, liquid crystal panels 29R, 29G and 29B. Even if a relatively large screen with a size of 3 inches and a high resolution (a large number of pixels) is used, it is generally widely used.
A lens device for a 5 mm still camera is used as a projection lens 33.
Can be installed as.

Further, since the optical system is made compact so that a reduced image is formed on the lens surface of the field lens 32, the projection lens 33 is provided inside the projector 10.
A space for arranging the mirror 34 outside can be easily secured, and the mirror 34 can easily realize the projection direction of the projection light in an arbitrary direction.

The projection direction switched by the mirror 34 is not limited to the two directions shown in the above embodiment. For example, as shown in FIG. 6, when projecting from the opening 11 on the upper surface and by projecting from the opening 12 'on the front surface (left side in FIG. 6) by the mirror 34' arranged outside the projection lens 33. You may make it switch and. In this case as well, the mirror 34 'has the fulcrum 34 of the support member 34a'.
By rotating it around b ', the mirror 34' is positioned outside the optical path as shown by the broken line in FIG. 6 so that the projection direction can be switched. Alternatively, although not shown, openings may be provided in three directions and switched by a mirror.

Although the above-described embodiment is applied to the liquid crystal projector of the three-plate three-primary-color separation / synthesis method, it is needless to say that the invention can be applied to the liquid crystal projector of other methods.

[0032]

According to the present invention, the image is reduced by the relay lens to form a reduced image on the field lens surface.
A small-diameter projection lens can be used, the size of the optical system can be reduced, and the projection lens can be moved parallel to the optical axis, so that distortion due to tilting can be corrected. In this case, by forming a reduced image and forming the optical system in a small size, it is possible to move the projection lens in parallel with the optical axis with a relatively simple structure and the optical system is small. Therefore, it is possible to easily arrange a mirror on the outside of the projection lens, and it is possible to realize a liquid crystal projector that can cope with various projection states with a simple configuration.

[Brief description of drawings]

FIG. 1 is a sectional view taken along line I-I of FIG. 3 showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG. 3 showing an embodiment of the present invention.

FIG. 3 is a perspective view showing the external appearance of an apparatus according to an embodiment.

FIG. 4 is an explanatory diagram showing a projection state of an example.

FIG. 5 is an explanatory diagram showing a projection state of an example.

FIG. 6 is a sectional view showing another embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a distortion generation state due to a tilt of the projector.

[Explanation of symbols]

 3 Screen 10 Liquid Crystal Projector 11, 12 Opening 21 Light Source 23 First Dichroic Mirror 24 Second Dichroic Mirror 25 Third Dichroic Mirror 26 Fourth Dichroic Mirror 27, 28 Mirror 29R, 29G, 29B Liquid Crystal Panel 30 Relay Lens 31 Mirror 32 Field Lens 33 Projection Lens 34 Mirror

Claims (2)

[Claims] 1. A liquid crystal projector for irradiating a liquid crystal panel with illuminating light, projecting transmitted light of an image displayed on the liquid crystal panel onto a predetermined screen by a projection lens, and displaying the image on the screen. Light is reduced by a relay lens to form a reduced image on the field lens surface, image light of the reduced image is made incident on the projection lens, and the projection lens is movably arranged parallel to the optical axis. Furthermore, a liquid crystal projector in which light emitted from the projection lens can be bent by a mirror according to the position of the screen. 2. The liquid crystal projector according to claim 1, wherein the field lens is moved in parallel with the optical axis in conjunction with the parallel movement of the projection lens.