JPS5841721Y2 - projection cathode ray tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reflective projection cathode ray tube used in projection television devices and the like.

As the projection type cathode ray tube, those shown in FIGS. 1 and 2 have been proposed.

In FIGS. 1 and 2, reference numeral 1 denotes a valve, which includes a flat face plate 2, a cylindrical funnel portion 3 with a bottom, and a neck portion 4 extending outward from the center of the bottom of the funnel portion 3. It consists of

Further, 5 is a metal cylinder, 6 is a metal base fixed to the center of the open end surface of the metal cylinder 5 via a support fitting 7, and 8 is a target formed on the inner surface of the metal base 6. is formed by a fluorescent film 9.

Further, reference numeral 10 denotes a concave spherical mirror having a through hole 15 in the center fixed to the other open end surface of the metal cylindrical body 5.
0 and target 8 face each other, and their opposing surfaces are polished into spherical surfaces having the same center of curvature.

11 is a plate spring for supporting and fixing the metal cylindrical body 5 on the inner surface of the funnel part 3; 12 is an electron gun housed in the neck part 4;
Reference numeral 3 denotes a focusing/deflecting coil arranged around the outer periphery of the neck portion 4 .

The central axis of the electron gun 12 is the target 8 and the mirror 10.
is placed toward the optical axis of the

The operation will be explained below.

That is, the electron beam 14 emitted from the electron gun 12 passes through the hole 15 formed in the center of the mirror 10 and reaches the target 8.
The light hits the fluorescent film 9 and scans over it to create an image.

Next, this image is projected as image light 16 onto a mirror 10 facing the target 8, where it is reflected, and the reflected light becomes enlarged image light 17 and passes through the face plate 2, correcting aberrations caused by the spherical mirror. The image passes through a spherical aberration correcting lens (not shown) and is focused on a sufnoon (not shown) located further ahead, producing an enlarged image.

By the way, not all of the image light 16 projected from the target 8 toward the mirror 10 is reflected by the mirror 10, and some of the image light 16a passes through the hole 15 as shown by the dashed line in Figure 3. and is projected onto the electron gun 12.

Then, since the conventional electron gun 12 has a flat metal surface at its tip (anode plate, etc.) facing the target 8, the image light 16a from the target 8 hits this metal surface 12'. reflected and its reflected light 16
b passes through the hole 15 of the mirror 10 again and hits the fluorescent film 9 of the target 8, making the hit area brighter.

Therefore, the contrast ratio of the image created on the fluorescent film 9 of the target 8 becomes poor, and eventually the contrast ratio of the image projected on the screen also becomes poor.

The present invention improves and eliminates the above conventional drawbacks, and provides a projection cathode ray tube that improves the contrast ratio of images on the screen by eliminating reflected light from the electron gun to the target.

The present invention will be explained below with reference to examples. When the present invention is applied to a projection type cathode ray tube having the above configuration, the first embodiment of the present invention, as shown in FIG. good.

That is, at least the end face portion of the electron gun 18 facing the target 8 is coated with graphite or the like to be blackened, and this end face portion is configured as the antireflection body 19.

For example, if the tip of the electron gun 18 is an anode plate and the front surface of the anode plate 1 faces the target 8, the front surface of the anode plate may be blackened by applying graphite or the like.

Further, in addition to providing the antireflection body 19 only at the tip of the electron gun 18, the entire electron gun 18 may be blackened.

According to this electron gun 18, the image light 16a projected onto the electron gun 18 from the fluorescent film 9 of the target 8 through the hole 15 of the mirror 10 hits the blackened antireflection member 19.

This image light 16a is absorbed by the graphite film of the antireflection member 19 and is not reflected.

Therefore, the image of the fluorescent film 9 on the target 8 is captured by the electron beam 14.
The image is directly reflected by the mirror 10 and formed on the screen.

The anti-reflection body 19 of the electron gun 18 has been described as having a structure that prevents reflected light to the target 8 by turning black and absorbing light, but the point is that the reflected light 16 b of FIG. 3 caused by the image light 16 a is Any structure is sufficient as long as it does not reflect the reflected light onto the target 3, and therefore the anti-reflection body 19 may be constructed as shown in the following embodiment.

For example, instead of the blackened antireflection body 19, the blackened surface is made into a rough surface, and the image light 16a from the target 8 is diffusely reflected by this rough surface, thereby reducing the amount of light reflected to the target 8.

Furthermore, apart from diffuse reflection, the direction of reflection of the image light 16a may be directed away from the target 8.

For example, as shown in FIG.
The surface portion facing the surface may be inclined, and this inclined surface may be used as the antireflection body 19'.

The anti-reflection body with such a rough surface, an inclined surface, or the above-mentioned anti-reflection body with blackening may be applied to the anode plate, but it may also be constructed separately from the electron gun.

Note that the above configuration has a target 8 and a mirror 10 inside the bulb 1.
Although the description has been made using a projection type cathode ray tube that houses a metal cylindrical body 5 having a metal cylinder 5 on both end faces, it is also possible to fix the target directly to the inner surface of the face plate of the bulb and have the same center of curvature as the inner surface of the face plate. The present invention can also be applied to a projection type cathode ray tube in which a mirror is formed on a part of the inner surface of the funnel portion facing the inner surface of the face plate.

As explained above, the present invention provides a cathode ray tube in which a target having a fluorescent film inside the bulb and a mirror and an electron gun are disposed facing the target. Since an anti-reflection body is provided that absorbs light from the target and prevents it from reflecting back to the target, even if the image light from the target is reflected by the electron gun, it will not be projected onto the target again. Since only the image created by the beam is enlarged and displayed on the screen as it is, the contrast ratio of the image is improved and the commercial value is improved, which is a great benefit.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of a conventional projection type cathode ray tube, Fig. 2 is a sectional view taken along line A-A in Fig. 1, Fig. 3 is an enlarged explanatory view of the main parts of Fig. FIG. 5 is a side sectional view showing an embodiment of the projection type cathode ray tube according to the invention. FIG. 5 is a side sectional view showing another embodiment of the invention. 1...Valve, 8...Target, 1
0...Mirror, 15...Through hole, 18.
...Electron gun, 19.19'...Antireflection body.

Claims (1)

[Scope of utility model registration request] In a cathode ray tube that has a target with a fluorescent film inside the bulb, a mirror with a through hole in the center facing the target, and an electron gun on the back of the mirror, at least the electron gun faces the target. A projection type cathode ray tube characterized in that a projection type cathode ray tube is provided with an anti-reflection member on a tip surface portion thereof to prevent light from the target from being reflected back to the target.