JPS6392179A - Video projector - Google Patents

Abstract

PURPOSE:To contrive to attain a compact casing by disposing a convex mirror in the projection optical system of a video projector. CONSTITUTION:The video projector 7 is constituted of a cathode ray tube 1, a projection lens 2 the convex mirror 4, a screen 6 and the casing 8. A picture projected on the fluorescent screen of the cathode ray tube 1 is a projection light flux by the projection lens 2. The light flux is made incident on the mirror 4, reflected, at the time of a reflection, a reflected surface is convex, the light flux 3 grows an extremely enlarged projection light flux 5. The light flux 5 is made incident on the screen 6 to reproduce the picture. The light flux 3 made incident on the mirror 4 is thin, so that the size of the mirror 4 may be a small aperture accordingly, the casing 8 is compacted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a projection television receiver or video projector, and more particularly to its compactness.

BACKGROUND OF THE INVENTION Various methods have been used to make video projectors more compact. Generally, by widening the angle of view of the projection lens, the projection distance between the projection lens and the screen is shortened, thereby aiming at compactness. However, in order to widen the angle of view of a projection lens, it is necessary to increase the number of lenses in the lens configuration more than ever before to improve the aberration correction ability due to the off-axis aberrations that occur significantly with the widening of the angle of view. Development was not easy, and the projection lens was also expensive.

On the other hand, Japanese Utility Model Publication No. 17648/1983 describes a method of reflecting a vertically compressed projection light beam on a cylindrical reflector to reproduce an enlarged projected image having a regular aspect ratio on a screen. It is being

In this method, the projected light beam is compressed only in the vertical direction until it is reflected by the cylindrical reflector, which increases the degree of freedom when arranging each component of the video projector and makes it more compact. This is what we are trying to achieve. Furthermore, JP-A-58-94286, JP-A-58-197
In Japanese Patent No. 969, the projection light beam is reflected many times by a plurality of plane mirrors, and the projection interval between the projection lens and the screen is
A method for housing a compact video projector in a housing is described.

Problems to be Solved by the Invention However, conventional video projectors using the above-mentioned technology aimed at compactness have the following problems. First, in the method using a cylindrical reflecting mirror, the projected light flux is not compressed in the horizontal direction, so a cylindrical reflecting mirror that is long in the horizontal direction is required, and in processing the cylindrical reflecting mirror, Problems arise with accuracy and cost. next,
In the method of using multiple plane mirrors to reflect the light many times and keeping the projection interval between the projection lens and the screen within a small volume, the number of reflections is large, so the reproduced image becomes dark due to the loss of light amount that occurs with each reflection. There's a problem.

Furthermore, since the projection light beam is already spread out on the plane mirror that reflects the projection light beam just before it is incident on the screen, the plane mirror becomes large, which causes problems such as a complicated holding method and an increase in cost.

Means for Solving the Problems The technical means of the present invention for solving the above problems is to magnify an image projected on the fluorescent screen of a cathode ray tube in a television receiver by using a projection lens, and then enlarge at least one mirror. The first mirror counted from the screen side to the cathode ray tube side of the video projector that projects onto the screen through the video projector is configured to have a convex surface.

action The effect of this technical means is as follows.

Immediately before the projected light beam, which is an image projected on the fluorescent screen of a cathode ray tube in a television receiver and is magnified by a projection lens, enters the screen, that is, the first convex mirror counting from the screen side to the cathode ray tube side. reflected. Therefore, the projection light beam incident on the convex mirror is significantly spread out, reflected, and incident on the screen. Therefore, compared to conventional projection lenses, the projection light beam emitted from the projection lens can be substantially compressed in both the horizontal and vertical directions, so the guaranteed angle of view of the projection lens can be narrow, and the number of lens components can be reduced. This makes it possible to reduce costs. Furthermore, since the projected light beam incident on the convex mirror is narrow, the convex mirror can effectively reflect the entire projected light beam without causing vignetting even with a small diameter, making it possible to create a convex mirror at low cost. It is possible to obtain The video projector can be made compact because the projection light beam is narrow and a convex mirror with a small diameter can be used.

Embodiment Hereinafter, a video projector according to an embodiment of the present invention will be described with reference to the drawings. Note that the same components are given the same reference numerals.

FIG. 1 is a side view showing a schematic configuration based on a first embodiment of a video projector according to the present invention.

The video projector 7 includes a cathode ray tube 1 and a projection lens 2.
, a convex mirror 4, a screen 6, and a housing 8. The image projected on the fluorescent screen of the cathode ray tube l becomes a projection light beam 3 by the projection lens 2. This projected light beam then enters a convex mirror 4 and is reflected. During reflection,
Since the reflecting surface is convex, the reflected light beam becomes the projection light beam 5 which is significantly expanded. This enlarged projection light flux is incident on the screen 6 to reproduce an image. As shown in FIG. 1, since the projection light beam 3 that enters the convex mirror 4 is thin, the convex mirror 4 may have a small diameter. is compacted.

FIG. 2 is a side view showing a schematic configuration based on a second embodiment of the video projector according to the present invention.

In the second embodiment, a schematic configuration for reducing the height dimension of the housing 8 is shown. The image projected on the fluorescent screen of the cathode ray tube 1 becomes a projection light beam 3 by the projection lens 2 and the plane mirror 9. This projected light beam then enters a convex mirror 4 and is reflected. During reflection, the reflected light beam becomes a significantly enlarged projection light beam 5 because the reflecting surface is convex.

This enlarged projection light flux is incident on the screen 6 to reproduce an image. In this way, since the plane mirror 9 is used,
The projection lens 2 and the cathode ray tube 1 can be tilted more horizontally, and as a result, the height dimension of the housing 8 can be reduced.

Since the convex mirror is inclined with respect to the optical axis of the projection lens, it can be considered as a so-called off-axis optical system.

Therefore, it is preferable to make the shape of the convex mirror aspherical to improve the aberration correction ability. Note that this aspherical surface can also be an anamorphic aspherical surface depending on the need for aberration correction.

By using the convex mirror as a front mirror, it is possible to prevent the generation of ghost images that would be a problem in the case of a rear mirror. On the other hand, by using a back mirror, it becomes a so-called Mangin mirror, and by giving one reflection and two refraction effects to the convex mirror, it increases the degree of freedom in design and can also provide aberration correction ability. It is possible.

By making such a convex mirror out of plastic,
It is now possible to create by molding, and while it is low cost,
This can provide advantages such as easy formation of an aspherical surface.

Effects of the Invention The present invention can achieve compactness by arranging a convex mirror in the projection optical system of a video projector, and the projection lens only needs to have a small angle of view, resulting in low cost. Its industrial value is great, as it allows things to be used.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a schematic configuration of a video projector according to a first embodiment of the present invention, and FIG. 2 is a side view showing a schematic configuration of a video projector based on a second embodiment of the present invention. 1... Braun tube, 2... Projection lens, 4... Convex mirror, 6... Screen. Agent's name: Patent attorney Toshio Nakao 1 person 4- Convex bulge 1st figure 1- Screen confectionery 2nd figure δ

Claims (5)

[Claims] (1) In a video projector in which an image projected on a fluorescent screen of a cathode ray tube in a television receiver is enlarged by a projection lens and then projected onto a screen via at least one mirror, from the screen side to the cathode ray tube side. A video projector characterized in that the first mirror is configured to have a convex surface. (2) The video projector according to claim (1), wherein the first mirror counted from the screen side to the cathode ray tube side has a convex aspherical surface. (3) The video projector according to claim (1), wherein the first convex mirror counted from the screen side to the cathode ray tube side is a front mirror. (4) The video projector according to claim (1), wherein the first convex mirror counted from the screen side to the cathode ray tube side is a back mirror. (5) The video projector according to claim (1), wherein the first convex mirror counted from the screen side to the cathode ray tube side is made of plastic.