JPS6123130A - Back projection type display device - Google Patents

Abstract

PURPOSE:To compensate optical aberrations and to prevent deterioration in resolution by providing a curved surface correcting and adjusting mechanism to the surface of a reflecting mirror provided on the optical path between the projection tube and projection lens of a video projector. CONSTITUTION:Projection tubes 1R, 1G, and 1B of the three primary colors and projection lenses 2R, 2G, and 2B are arrayed laterally in a line, and reflecting mirrors are arranged at the 1st mirror position (c) and the 2nd mirror position (d). The 1st mirror consists of a fixed frame 5 for fixing a mirror 3, a rotating body 8 for adjusting the curvature of the mirror, a fixing screw 7, and a metallic holder 6. When this has an aspect ratio 5:3 like a high-quality television, the 1st mirror is made long to about 4:1 so as to cover all the three primary colors and the mirror becomes easier to curve. The mirror is applied with a stress through the fixing screw 7 to vary and correct the curvature of the mirror. Consequently, aberrations of an optical image on a screen surface 4 are compensated ideally.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rear projection display device capable of improving the optical image quality of a rear projection optical system using a reflecting mirror in a video projector using a projection lens. It is something.

Conventional configurations and their problems Recently, various display devices using projection lenses have been developed. In particular, a system using a CRT projection tube and a projection lens has been put into practical use as an image display of about 40 inches to 200 inches from the viewpoint of image performance and device cost. Among these, integrated rear projection displays with a reflective mirror installed in the optical path have become the mainstream for displays of about 40 inches because of their compactness and resistance to external light reflection. It is also considered a promising candidate for a color display home monitor that can display high-precision color images with a size of about 40 inches.
This is the projection type display, and products have been announced that have improved the performance of the projection tube and projection lens to meet the specifications of the future high quality televisions.

Naturally, in order to be able to display several times more pixel information than conventional television images, requirements for optical aberrations have become higher.

A conventional rear projection display device will be described below.

FIG. 1 shows a configuration diagram of a conventional rear projection display device, in which 1 is a projection tube that forms an image, and 2 is a projection tube that forms an image.
is a projection lens that projects the image onto the screen 4,
Reference numeral 3 denotes a reflecting mirror for bending the optical path from the projection lens to the screen 74. In Fig. 1, only one projection tube is shown to simplify the explanation, but three-tube projection is common, and the reflection mirror 3 is also folded twice as shown in the figure. There are many. FIG. 2 is a drawing of the shape of the reflecting mirror 3 in FIG. 1. In general, the reflective surface is often a front mirror, eliminating double images on the reflective surface.

Ideally, the reflecting mirror 3 is generally perfectly flat, but as shown in the cross-sectional view of FIG. 2, it is curved by a minute amount l with respect to the width. Since television images are long in the horizontal and lateral directions, they are often curved in the longitudinal direction, and reflective mirrors are often distorted into cylindrical curved surfaces.

The operation of the conventional rear projection display device configured as described above will be explained.

When the reflecting mirror is curved as shown in Figure 2, if we approximate the curvature with radius H to the equality constraint, we can assume that the amount of deflection is 4 and l for the dimension of the reflecting mirror. If the radius of curvature is R, then 'R-L/1
It can be approximated by 2. In other words, the presence of the deflection l in the reflecting mirror is equivalent to the presence of a cylindrical mirror in the projection optical system, which results in aberrations on the focal plane onto the screen.

FIG. 3 shows the optical path when the reflective optical system is expanded and considered when projecting straight.

If the reflective surface is convex as in the case of Figure 2, the third
In the figure, it is equivalent to a concave lens inserted only in the lateral direction, so the focal plane of the screen 4 is shifted backward. In other words, if the beam spot shape on the projection tube 1 is circular as shown in Figure 3A, then the beam spot shape on the screen will be as shown in Figure 3B.
It becomes horizontally long like this. Also, by readjusting the projection lens 2, the spot shape changes on the screen, but it does not become a perfect circle, but becomes vertical as shown in Figure 3C or cross-shaped as shown in Figure 3E. As a result, the resolution deteriorates. In this way, in the above-mentioned configuration, since the reflecting mirror is curved, there is a problem in that the deterioration of the resolution becomes noticeable, especially when receiving high-resolution images such as on a high-definition television. . Note 1. Figure 3B
is the case without a mirror, and F indicates the mirror position.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional problems, and aims to provide a rear projection display device that can minimize the occurrence of aberrations in the optical path caused by the reflecting mirror.

Structure of the Invention The present invention includes a projection tube, a projection lens, and a reflection mirror provided in an optical path between the projection tube and the projection lens.
This is a rear projection type display device in which the reflecting mirror is equipped with a curved surface correction adjustment mechanism to correct the amount of deflection due to curvature, and by optimally adjusting this deflection adjustment mechanism, deterioration in resolution of the optical system is eliminated. It is something to do.

DESCRIPTION OF EMBODIMENTS FIG. 4 is an overall configuration diagram of a rear projection display device according to an embodiment of the present invention, and the same symbols are used to indicate the same functions as in the conventional example. 1R, 1G.

1B shows three primary color projection tubes arranged in-line in the horizontal direction. 2R, 2G, and 2B are projection lenses for projecting the images of each projection tube onto the screen 4, respectively. In order to organize the set into a single piece, the number of folds on the reflecting mirror is generally two.
In each figure, the position of the mirror is shown as an example in the developed view. A in FIG. 4 is the first mirror position, and the mouth is the second mirror position. It is needless to say that this configuration diagram is exactly the same in both the conventional example and the case where the pressure tube projection method is used. FIG. 5 shows the shape of the mirror at the first mirror position in FIG. 4. The structure of the first mirror includes a fixed frame 6 for fixing the mirror, 8 is a rotating body for adjusting the curvature of the mirror, and 7 is a threaded mirror movement amount fixing screw.
Reference numeral 6 denotes a holding fitting that holds the rotating body 8 relative to the mirror fixing frame 5, and the operation of the rear projection type display device having an angle of 3° or more will be explained. As is clear from FIG. 4, when arranged in-line, the reflection mirror has a larger aspect ratio than the image on the CRT projection tube. For example, in the case of a 5:3 aspect ratio such as a high-definition television, the optical path from the 1G projection tube passes in a 5:3 shape, as shown by the shaded area in Figure 5, but the entire three colors are In order to cover this, the first mirror tends to be long with a 4:1 deflection, which tends to cause mirror curvature, which has been a problem in the past. In order to correct the curvature to either an uneven or concave surface, stress can be applied to the mirror by the rotating body 8 via the fixing screw 7. The fixing screw 7 must be fixed to the reflecting mirror 3, but even if it penetrates to the reflective surface side of the glass, the focal plane of the optical system is on the screen, and at the intermediate mirror position, the image of the fixing screw is No image is formed and the image quality is not affected.

As described above, by providing the reflecting mirror with a mechanism that can variably correct the curvature of the mirror, it is possible to ideally correct the aberration of the optical image on the screen surface. In particular, the larger the aspect ratio, the greater the effect. Furthermore,
Since the second mirror may also be curved, it is possible to compensate for the curve of the second mirror by the correction function of the first mirror. That is, the first mirror not only has a flat surface due to its own curve, but also can have a convex or concave surface depending on the direction of curvature of the second mirror. The shape of the second mirror is closer to the aspect ratio of the image than the first mirror, but if the magnification is large, the shape will be large, and if the inclination angle is large, there is a high possibility of distortion. The inventive means are very effective. For example, for a screen size of about 40", the second mirror will be about 1 meter in size, but from the viewpoint of weight and cost, the thickness is generally about 6 to 6 mm.
There is a strong possibility of it being one-sided.

This example was explained using a three-tube refractive lens system, but it goes without saying that it is also effective if it uses a mumit optical system or other projection optical system, and if it uses a reflecting mirror. Nor. Furthermore, it goes without saying that any type of system may be used for the curved surface correction mechanism.

FIG. 6 shows a curved surface correction adjustment mechanism in another embodiment of the present invention. In FIG. 6, 3 is a reflecting mirror, 9,
Reference numeral 1o denotes a fixing frame for the mirror, and the fixing frame is fixed to a holding fitting 12 at the center of the mirror by a horizontally long frame 11 that fixes the center of the mirror. As shown in Fig. 5, there is no hole in the center, and as shown in the AA' cross section, it is supported by lines rather than points in the upper and lower width directions 9, and adjustment screws 13 on both sides. 14.
By adjusting 15°16, it is possible to correct the curved surface to a cylindrical shape with respect to the center. As mentioned above, in order to achieve the object of the present invention, it is necessary to correct the curved surface to make it both uneven and concave, so stress can be applied to both sides of the mirror in the direction of both sides in FIG. FIG. 6 is a sectional view taken along the line AA' in FIG. 6a.

As described above, the effects described in the previous example are achieved, and
Since no holding fittings, screws, etc. are placed in the center of the reflecting mirror, optical problems are eliminated. Alternatively, apart from FIG. 6, a curved surface may be formed by applying stress to the holding fitting 12 at the center of the mirror. However, in this case, the fixing frames on both sides serve to hold and fix the mirror without any adjustment.

Effects of the Invention As described above in each embodiment, in the present invention, by providing a curved surface correction adjustment mechanism on the surface of the reflecting mirror,
Since it is possible to correct the cylindrical curvature correction, which is subject to equal restrictions, and to subtly correct the optical aberration of the reflective optical system, deterioration of resolution can be prevented.

Projection systems that use two or more reflective mirrors are particularly effective, and are more practical than using expensive and heavy mirrors that maintain perfect flatness, and the higher the precision of the display, the more effective it will be industrially. It is something that has practical and economic value.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of a conventional rear projection display device, Fig. 2 a and b are a front view and a sectional view of a reflecting mirror, Fig. 3 is an explanatory diagram of the optical path of the conventional device, and Fig. 4
The figures are a principle diagram of a rear projection display device according to an embodiment of the present invention, FIG. 5, and a top view and a sectional view of a ray device. 1... Projection tube, 2... Projection lens, 3
... ・Reflection mirror, 4...Screen, 8.
····Rotating body. Figure 1 Figure 2 Figure 3 D''' (I) Figure 4 Mouth Figure 5 Figure 6 1 B

Claims (1)

[Claims] A projection tube that emits an image, a projection lens that projects the image of the projection tube onto a screen, and a reflection mirror that is provided between the optical path of the screen and the projection lens, and the reflection mirror is provided with a curved surface correction adjustment mechanism. A rear projection display device with