JPH11162372A - Electron gun - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the effect of the degree of speed modulation on electron beam and to display high quality images with a simple structure by forming a slit in one or a plurality of electrodes of a plurality of grid electrodes constituting an electron gun in the direction orthogonal to the propagation direction of the electron beam. SOLUTION: In order to prevent deterioration of the effect of high frequency magnetic field generated by a VM coil 2 on electron beam due to shielding of the high frequency magnetic field by eddy current flowing in a fourth grid G4, a slit (a cut groove) 4 is formed in the fourth grid G4 in which the VM coil 2 is installed in the direction orthogonal to the electron beam propagation direction. Consequently, eddy current generation is suppressed and the affecting degree (the sensitivity) of the high frequency magnetic field on the electron beam can be improved and image formation by a television picture tube set is facilitated and carried out only by a single part (the fourth grid G4), resulting in the cost reduction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun in which the influence of an eddy current on an electron beam is reduced, and more specifically, a high frequency magnetic field generated by a VM coil is shielded by an eddy current flowing through a grid electrode. By
The present invention relates to an electron gun that prevents the degree of influence (sensitivity) from being reduced.

[0002]

2. Description of the Related Art Conventionally, in an electron gun built in a CRT (cathode ray tube), an eddy current generated in each grid electrode constituting the electron gun has an influence on convergence due to a rapidly changing deflection magnetic field. . Also, for example, V
A type of CRT, such as an M coil, in which a high-frequency magnetic field is applied to change the deflection speed of an electron beam to enhance the image quality is also known. In general, a signal obtained by differentiating a luminance signal of a video signal twice is applied to the VM coil. The signal differentiated twice changes the deflection speed of the electron beam by the deflection yoke, thereby enhancing the boundary between the bright and dark portions of the image, thereby obtaining an effect of providing sharpness. Here, an operation of giving an image sharpness by a signal applied to the VM coil will be described with reference to the drawings.

FIG. 2 is a diagram for explaining the relationship between a video signal and a video signal generated by a signal applied to a VM coil. (1) is an original video signal, and (2) is a video signal once. The differentiated signal (3) is a signal obtained by differentiating the video signal twice.
In the figure, the horizontal axis represents time, and the vertical axis represents signal amplitude.

The video signal on the left side shown in FIG.
There is no VM coil, as shown on the right,
The video signal in this case is in the same state as the original video signal. In other words, the low-level portion has the same dark portion, and similarly, the high-level portion has the same bright portion. On the other hand, FIG.
FIG. 3 (3) shows a state in which the VM coil is arranged. A signal obtained by differentiating the original video signal shown on the left side of FIG. 2A twice is applied to the VM coil.

In the state shown in FIG. 2 (3), the signal applied to the VM coil acts on the electron beam modulated by the original video signal, and changes the deflection speed. for that reason,
As shown on the right side of FIG. 2 (3), the signal obtained by differentiating the original video signal applied to the VM coil twice is applied to the original video signal, and its rising and falling portions are
Causes a large change in the opposite direction. Therefore, FIG.
In the video signal shown on the right side of (3), the change in the video signal becomes large, especially in the rising portion from the dark portion to the bright portion, and the light and dark are further emphasized. The same applies to the falling part from the bright part to the dark part.

However, in this type of CRT that enhances image quality, if an electrode (part) constituting an electron gun is present at a position of an added VM coil or the like, the electron gun electrode shields a high-frequency magnetic field, and the There is a problem that the degree of velocity modulation (sensitivity) given to the electron beam when a unit current flows through the coil is reduced. The reason why the electron gun electrode shields the high-frequency magnetic field is that energy loss is caused by the eddy current flowing through the electron gun electrode. Conventionally, as a countermeasure to reduce the influence on the speed modulation degree (sensitivity) given to the electron beam, for example, a method of dividing the electrode part into two parts and conducting with a lead wire through a slight gap between the two parts. Has been done.
According to this method, since the eddy current can be reduced, it is possible to suppress the influence of the velocity modulation degree on the electron beam.

[0007]

As described in the prior art, in a CRT electron gun, an eddy current generated in each grid electrode constituting the electron gun causes a velocity modulation (sensitivity) applied to the electron beam. ). As one conventional countermeasure, for example, a method has been used in which an electrode part is divided into two parts, and conduction is provided by a lead wire through a slight gap between the two parts. But,
If this method is adopted, one electrode is originally composed of two parts, so that conduction between the two is required, and the beading process becomes complicated. Become. SUMMARY OF THE INVENTION It is an object of the present invention to provide an electron gun capable of removing an influence of a velocity modulation degree on an electron beam with a simple configuration and capable of displaying an excellent image.

[0008]

According to the present invention, one or more of a plurality of grid electrodes constituting an electron gun are provided with slits in a direction orthogonal to the traveling direction of an electron beam.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a high frequency magnetic field generated by a VM coil is shielded by an eddy current flowing through a grid electrode to prevent the influence on an electron beam from being reduced. The feature is that a slit (notch groove) is provided in the arranged electron gun electrode in a direction orthogonal to the traveling direction of the electron beam.

FIG. 1 is a schematic side sectional view showing an example of the configuration of the main parts of an electron gun and a VM coil according to an embodiment of the electron gun of the present invention. In the figure, 1 is a neck glass of a CRT, 2 is a VM coil, 3 is a cathode portion, 4 is a slit (notched groove), and G3 to G5 are third to fifth grids.

FIG. 1 shows a general single-beam electron gun and a VM coil. Thus, the VM coil 2
The slits 4 are provided in a direction perpendicular to the traveling direction of the electron beam, for example, in a fourth grid G4 provided in the neck glass 1 and disposed in the vicinity of the neck glass 1, so that generation of eddy current can be suppressed. Become. Therefore, the influence of the eddy current on the electron beam can be significantly reduced.

[0012]

According to the electron gun of the first aspect, a slit is provided in the electron gun electrode on which the VM coil is disposed in a direction perpendicular to the traveling direction of the electron beam. Therefore, generation of eddy current is suppressed, and the degree of influence (sensitivity) of the high-frequency magnetic field on the electron beam of the electron gun is improved. As a result, image creation of the television receiver set becomes easy. In addition, unlike the conventional method in which one electrode is originally composed of two parts, it can be implemented by a single part (grid electrode), so that the cost of the electron gun can be reduced.

According to a third aspect of the invention, the electron gun of the first aspect is used for a projector CRT. Therefore,
Also in the projector, the effect of the electron gun according to claim 1 can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view showing an example of a configuration of a main part of an electron gun and a VM coil according to an embodiment of an electron gun of the present invention.

FIG. 2 is a diagram illustrating a relationship between a video signal and a video signal generated by a signal applied to a VM coil.

[Explanation of symbols]

1 ... CRT neck glass, 2 ... VM coil, 3 ...
... Cathode part, 4 ... Slit, G3 ~ G5 ... 3rd ~
Fifth grid

Claims (3)

[Claims] 1. An electron gun for a CRT having a plurality of grid electrodes, wherein one or more of the plurality of grid electrodes are provided with a slit in a direction orthogonal to a traveling direction of an electron beam. A featured electron gun. 2. The electron gun according to claim 1, wherein the grid electrode provided with the slit is a grid electrode having a VM coil arranged on an outer periphery thereof. 3. The electron gun according to claim 1, wherein said electron gun is usable for a projector.