JPS58129732A - Projection cathode-ray tube - Google Patents

Abstract

PURPOSE:To prevent occurrence of a chipped image and obtain the bright image in a reflective projection cathode-ray tube in which an enlarged picture can be obtained from a spherical mirror, by displacing the center of a target from the central axis of the mirror. CONSTITUTION:A luminous point A in the bottom corner part and a luminous point B in the upper corner part of a target 8' are reflected by optional points on a mirror 10 and imaged on each extension of straight lines OA and OB connecting a curvature center O of the mirror respectively to the points A and B. Here a curvature center O' of the target 8' is displaced from the center O of the mirror 10, and images are produced by a spherical aberration lens respectively on intersections A', B' between each extension of the lines OA and OB and a screen 3. In this way, even if unevenness of length of a cylindrical member 12 and thickness of a frit glass 13 or position shifting or the like of a face plate 5 is caused, a dimensional margin (unluminous range) of the target 8' is suppressed to a minimum to enable the prevention of a chipped image on the screen 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a projection type cathode ray tube, and more particularly to a reflection type projection type cathode ray tube that uses a spherical mirror to obtain an enlarged image.

FIG. 1 is a schematic explanatory diagram of a projection television apparatus, where l is a reflective projection cathode ray tube, 2 is a spherical aberration correction lens for correcting the spherical aberration of light emitted from the cathode ray tube l, and 3 Iri.
A screen 4 forms an image and reproduces a video, and 4 is a person viewing the screen 3. The screen 3 is formed in a concave spherical shape and is arranged so that its central axis a-a almost coincides with the line of sight b-b of the person 4. The cathode ray tube 1 is placed at a position where it does not obstruct the line of sight of the person 4 toward the screen 3. Therefore, the axis c - c of the cathode ray tube l and the central axis a - a of the screen 3
and tri%, and in the illustrated example, they are shifted by an angle θ.

Therefore, the throwing distance NR from cathode ray tube 1 to screen 3
Each At r 71217I3 is different.

An example of this cathode ray tube 1 is shown in FIG. The target 8 is formed by f41 the optical film 7. In addition, an end plate 9 has a concave spherical mirror 10 formed on its inner surface and a neck portion 11 outward from the center, and a frit glass is formed on both end surfaces of the face plate 5 and end plate 9 facing each other. The face plate 5, the end plate 9. neck portion l], and the cylindrical member 12 forms a valve. Reference numeral 14 indicates an electron gun housed within the neck portion ll.

Here, since the projection distance to the screen 3 is different,
Center of curvature 0 of mirror 10 and target 8 f! 11
The center of curvature 0' of the inner surface of the front face plate 5 is slightly different from the center of curvature 0' when the face plate 5 is a finch.
The target 8 is formed into a trapezoidal shape because the magnification of the image on the target 8 also differs depending on the projection dispersion of the screen 3-) due to the difference in the projection N1. (In the illustrated example, the centers of curvature 0 and 0' are shifted toward the ends of the rods.) This shadow trunk tube l is fixed to a support frame (not shown) with its axis directed toward the center of the screen 3, but is placed on the target 8. The video is on screen 3...)
L. If the electron beam from electron @14 is deflected so that the image fits within screen 3, the electron beam from target 8 will be shifted by CIT, and screen 3'' will have the problem that only a missing image will be obtained. there were.

This occurs due to variations in the length of the cylindrical portion side 12, the thickness of the frit glass 13, or a deviation in the position of the face plate 5 by δ (1). Therefore, if the target is made large considering these variations, - Although this problem could be solved, the effective light-transmitting area of the face plate 5 became smaller and the brightness of the image on the screen 3 decreased, making it difficult to increase the size of the target 8.

The present invention has been proposed in view of the above-mentioned problems, and provides a reflective projection cathode ray tube that solves the above-mentioned problems.

The present invention will be explained below with reference to FIGS. 4 and 5.

In the figure, the same reference numerals as in FIG. 2 indicate the same parts, and the explanation will be omitted. The feature of the present invention is that the target 8' is formed at the position ti.
Specifically, it is an extension of the straight line connecting the center of curvature of the mirror 1o and the periphery of the screen 3 and the face plate 5.
The target 8' is formed at a location including the area where the inner surface of the target 8' intersects with the inner surface of the target 8'. 111111, the center of the target 8' is shifted from the central axis of the mirror 10.

If this operation is explained in d11 from FIG. 6, the light-emitting bright spot A at the lower corner and the light-emitting bright spot B at the upper corner of the target 8' are reflected at any point on the mirror 10J-, and the center of curvature of the mirror is 0. An image is formed on each spider line of an extension line OA and a straight line OE that connect the bright spot A and the bright spot B.

Here, the center of curvature of the target 8' is shifted from the center of curvature O of the spherical aberration lens (
(not shown), images are formed at the intersections A, ', and B' of the screen 3 and the extension lines of the straight line OA and the line ○B, respectively. As a result, variations in the technique of the Enkai iM 12, the thickness of the frit glass 13, or the face plate 5
Even if a zero position error occurs, the dimensional margin (non-light emitting area) of the target 8'' can be minimized to prevent the image on the screen 3 from being missing.

Since the target 8' can be formed to the minimum size necessary for the image forming apparatus 1, the effective light-transmitting area of the face plate 5 can be increased, and a bright image can be obtained.

The present invention is directed to the above-mentioned projection type shade 1 (without being limited to the example, for example, a target made of a metal block coated with a fluorescent film and a mirror housed in a bulb).
It can also be applied to 1J ray tube.

5 -

[Brief explanation of drawings]

Fig. 1 is a schematic view of a projection type television coating showing #, j, '1, Fig. 2 is a side 11 side area 1 showing an example of a projection type cathode ray tube, and Fig. 3 is a second side view. , 4M is a side IJ side view of the projection type cathode ray tube according to the present invention, FIG. 5 is a front view of FIG. . 8'... Target, 10... Mirror. Patent applicant: NEC Corporation 6 -

Claims (1)

[Claims] A projection type ray tube in which a convex spherical target and a four-spherical mirror are housed in a bulb, and the center of the target is offset from the central axis of the mirror.