JPH0457014A - Projection type display device - Google Patents

Abstract

PURPOSE:To prevent the slow motion at the time of executing an enlarged projection onto a screen by interposing a cylindrical lens system before and after a real image formed by a convex lens placed on the same optical axis as a light valve and forming a corrected intermediate image compressed or expanded in one direction. CONSTITUTION:An anamorphic lens 12 is placed so that a corrected intermediate image is formed in a prescribed position in front of a focal position F1 of an object space side of a first lens 8. This lens 12 consists of a cylindrical concave lens 13 placed so as to share a focus on a common optical axis, and a cylindrical convex lens 14. According to these cylindrical lenses, a corrected intermediate image 11 formed by compressing one direction of an image can be obtained. Also, a position in which the image 11 is formed is a position for satisfying a relation of X=(m-1)f/(m+1), when a distance from a principal point position of the lens 13 to a forming position of the image 11, a focal distance of the cylindrical lens 13, and a correction rate of the image 11 are denoted as X, (f), and (m), respectively. Also, by satisfying this condition, an astigmatism can be eliminated.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a projection type display device, and in particular to a projection type display device that eliminates spacing and can enlarge and project video images, computer images, etc. onto a screen. Related to display devices.

(Prior Art) Recently, display devices using transmissive or reflective dot matrix liquid crystals (hereinafter referred to as light valves) have been used to enlarge and project images displayed on the light valves onto a screen as a large screen. An enlarged projection method that shows images is attracting attention.

This is because there is a natural limit to the size of image display using a cathode ray tube (CRT), and increasing the screen size requires increasing the size of the cathode ray tube itself, and in practical terms, the maximum size is about 40 inches, so anything larger than that is necessary. This is to meet the demand for obtaining images of.

On the other hand, since the area of the light valve itself is increased, it is not easy to obtain a large-sized liquid crystal display device that is free from defects in manufacturing, and even if it could be obtained, it would be extremely expensive.

For this reason, if you use a transmissive (or reflective) light bulb to enlarge and project the image displayed on it, you will be able to get an impressive large screen without being restricted by the screen size. It is possible.

Therefore, the optical system for magnifying projection using a light valve can be installed in the cabinet! - A display type display device that is housed inside the cabinet and projected onto a screen provided on the front of the cabinet so that an enlarged image can be viewed from the front of the cabinet has come to be provided.

Conventional rear projection display devices using this type of light valve provide illumination from a light source to a transmissive liquid crystal panel, and the image displayed on this liquid crystal panel is disclosed in, for example, Japanese Utility Model Application Publication No. 1-85778. The structure is such that the light is magnified by a projection lens, the optical path is changed by a reflecting mirror, and the light is guided to the back of the screen. By doing this, the entire projection optical system is housed within the cabinet, allowing it to be moved to any location, and allowing images on the screen to be viewed even in a bright room.

However, in the above-mentioned conventional display-type rear projection display device, the light flux that passes through the light valve is converted into an optical path by a reflecting mirror and guided to the back of the screen, so it is necessary to project the light with the optical axis perpendicular to the screen. Since image distortion occurs due to keystone distortion, etc., there are significant restrictions on the installation conditions of the reflecting mirror, and this increases the volume occupied by the projection optical system, especially the depth dimension (cabinet thickness) relative to the screen. , it cannot be made into a rear projection type display device due to the prodigal type cabinet.

Therefore, an oblique projection method can be considered as a means to solve this problem. In this oblique projection system, as shown in FIG. They are arranged with 9 in between. And this second
The lens 10 obliquely projects the image formed on the imaging plane 9 by the lens 8 onto the screen 3 which is arranged at an angle opposite to the inclination of the imaging plane 9 with respect to the optical axis 17, thereby producing an enlarged image. It is done so that it may be obtained. In this case, if the optical path from the second lens 10 to the screen 3 is bent by a reflecting mirror and guided to the back of a screen provided in the front of the cabinet, a display device using rear projection can be created as a compact optical system. can get.

(Problem to be Solved by the Invention) However, when a display device is constructed using the above-mentioned projection optical system, an elongation occurs in the image formed on the imaging plane 9 by the second lens 8, and this is corrected by the second lens 10. If the elongation is not properly corrected when the image is formed on the screen 3, the image will be distorted, resulting in an unsightly screen, and faithful reproducibility will not be obtained.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a projection type display device having a projection optical system that does not cause image delay on the screen when obtaining a large screen with a compact configuration using the projection optical system. be.

(Means for Solving the Problems) As a means for solving the problems of the prior art described above, the present invention provides a light source, a light valve that modulates the light from the light source, and a light valve arranged on the same optical axis as the light source. A cylindrical lens system that forms a corrected intermediate image by compressing or expanding one direction of the real image created by the cylindrical lens, and an enlargement projection that enlarges and projects the one-way corrected intermediate image formed by this cylindrical lens system into a regular image. It is characterized by the arrangement of an optical system and a screen that displays an enlarged image.

(Function) The light that passes through the light valve that modulates the light from the light source forms a real image with a convex lens, and is guided to a cylindrical lens system placed before and after the convex lens, which compresses or expands the - direction into a unidirectional correction intermediate. An image is formed, and this corrected intermediate image forms a real image on the imaging plane through the first lens, and is enlarged and projected onto the screen by the second lens via the reflecting means.

In this way, the corrected intermediate image compressed or expanded in one direction by the cylindrical lens system is completely corrected, and a regular image without any lag is obtained on the screen.

(Example) The present invention will be described below with reference to the example shown in FIGS. 1 to 5.

FIG. 1 shows an example in which the present invention is applied to an oblique projection display device, and FIG. 2 shows a longitudinal section thereof.

In this embodiment, the depth D is a thin box-shaped cabinet 1.
The cabinet 1 includes a projection optical system 2, a rear projection type screen 3 provided on the front surface of the cabinet 1, and a light flux emitted from the projection optical system 2 is guided to the rear surface of the screen 3. 1st and 2nd reflective mirrors 4, 5 for
It is equipped with

The projection optical system 2 used in the present invention, as shown in FIG. It has a second lens 10 with a reflection optical path.

According to the present invention, the anamorphic lens 12 is arranged so that the corrected intermediate image is formed at a predetermined position ahead of the focal point Fl of the lens 8 on the object space side. The anamorphic lens 12 includes a cylindrical concave lens 13 and a cylindrical convex lens 14, which are arranged on a common optical axis so as to share a focal point.

According to these cylindrical lenses, it is possible to obtain a corrected intermediate image 11 in which the image is compressed in one direction. The position where the one-way corrected intermediate image 11 is formed is determined by the distance from the principal point position of the cylindrical concave lens 13 to the formation position of the intermediate image 11 as X, the focal length of the cylindrical concave lens 13 as f1, and the correction rate of the intermediate image 11 as m. When, X=(
m-1) is a position that satisfies the relationship of f/(m+1).

By satisfying this condition, astigmatism can be removed.

Note that the cylindrical concave lens 13 and the cylindrical convex lens 14 can be interchanged back and forth on the same optical axis.

A convex lens] 5 is arranged on the object space side of the cylindrical convex lens 14, and a light valve 7 for modulating the light from the light source 6 is arranged on the object space side.

The light I valve 7 is a transmission type or reflection type driver.
It uses matrix liquid crystal, and the optical axis of lens 8]
6, and is installed at a predetermined angle.

Looking at the projection optical system 2 of the lens 8 from a geometrical optical perspective,
As shown in FIG. 4, the corrected intermediate image 11 and the imaging plane 9 are located at the imaging position A l of the lens 8.

A2, the extension line 18 of the corrected intermediate image 11 and the imaging plane 9
An extension line 19 of
It intersects at the 0 point on the line 20 perpendicular to .

At this time, the expansion rate m is m=f/ (χ f)= (χ2 f)/f=χ2
/χ1. In other words, m=tanα/lanα1.

By satisfying the condition 1 above, the corrected intermediate image 11 can be enlarged by the lens 8 and formed on the imaging plane 9.

The second lens 0 also has the image forming surface 9 and the screen 3 arranged in the same relationship as in the case of the second lens 8, so that the image on the image forming surface 9 is magnified by the second lens 10. An image is formed on the screen 3. This image is formed as an image with a magnification obtained by multiplying the magnification of the second lens 8 by the magnification of the second lens 10.

In the above embodiment, the present invention is applied to a reflective projection optical system, but as shown in FIG. 5, the present invention can also be applied to a transmissive projection optical system. According to this embodiment, the second lens 10 having an optical axis 17 bent at the imaging plane 9 with respect to the optical axis 16 of the first lens 8 is arranged with the imaging plane 9 in between. Through this second lens 10, the image formed on the image forming surface 9 can be enlarged and projected from an oblique direction onto the screen 3 which is inclined on the opposite side to the image forming surface.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a corrected intermediate image is compressed or expanded in one direction by interposing a cylindrical lens system before and after a real image arranged on the same optical axis as the light valve and formed by a convex lens. Since the image is formed, there is no delay when enlarging and projecting onto the screen, and the quality of the image on the screen can be significantly improved. In addition, since there is no distortion in the image even when it is projected diagonally to the screen, when it is built into a cabinet and used as a display type display device, the volume of the cabinet, especially the depth, can be reduced to 111%, making it compact. A display device can be obtained.

FIG. 4 is an explanatory diagram showing the relationship between the first lens of the projection optical system, the light valve, and the imaging plane in terms of geometrical optics. FIG. 5 is an explanatory diagram showing an example of the projection optical system of the present invention. FIG. 6 is an explanatory diagram showing the mold, and is an explanatory diagram of a conventional oblique projection optical system.

3...Screen, 6...Light source, 7...Light valve, 8...Luns, 9...Imaging surface, 10...
Second lens, 12...Anamorphic lens, 13.
... Cylindrical concave lens, 14... Cylindrical convex lens.

Claims (1)

[Claims] 1. A corrected intermediate image obtained by compressing or expanding one direction of a real image created by a light source, a light valve that modulates the light from the light source, and a convex lens arranged on the same optical axis. A projection type display device comprising a cylindrical lens system that forms a cylindrical lens system, an enlargement projection optical system that enlarges and projects a corrected intermediate image formed by the cylindrical lens system into a regular image, and a screen that displays the enlarged image. 2. The formation position of the above-mentioned corrected intermediate image is determined by the distance from the principal point position of the cylindrical concave lens to the intermediate image formation position as X,
Claim 1 characterized in that the lens is set to satisfy the relationship X=(m-1)f/(m+1), where f is the focal length of the cylindrical concave lens and m is the correction factor of the intermediate image.
The projection type display device described in .