Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Reexamination Certificate
2002-01-02
2004-11-30
Vo, Tuyet Thi (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
C315S005340, C313S414000, C313S415000
Reexamination Certificate
active
06825621
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. § 119 from an application for ELECTRON GUN FOR COLOR CATHODE RAY TUBE earlier filed in the Korean Industrial Property Office on 2 Jan. 2001, and there duly assigned Ser. No. 26/2001 by that Office.
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to an electron gun for a color cathode ray tube (CRT), and more particularly, to an electron gun for a color cathode ray tube in which the structure of an electrode for forming an asymmetrical beam forming lens is improved.
2. Related Art
An electron gun used in a large screen color cathode ray tube needs to be able to stably generate a low current electron beam and a high current electron beam. A cathode ray tube can adopt an in-line type electron gun and a deflection yoke of a self-converging type having a pincushion type deflection magnetic field and a barrel type deflection magnetic field. The deflection magnetic fields of the deflection yoke vertically over-focus and horizontally under-focus the electron beam so that a focus separation phenomenon occurs. The electron beam spot deformed as above becomes asymmetrical when being deflected toward the periphery of a screen. Also, in the in-line type electron gun, focus is not uniform due to a change in intensity of an electron lens generated by a change in a focus voltage.
To prevent the above deterioration of the focus of an electron beam landing on a fluorescent film, a method can be suggested in which distortion due to the irregular magnetic field of a deflection yoke is compensated for by forming the profile of an electron beam emitted from the electron gun to be vertically elongated.
U.S. Pat. No. 5,128,586, issued to Ashizaki et al., entitled COLOR CATHODE RAY TUBE GUN HAVING CONTROL GRID OF VARYING THICKNESS, discloses an electron gun emitting an electron beam having the vertically elongated profile which lands on the periphery of a screen to compensate for distortion of the electron beam due to the irregular magnetic field of a deflection yoke.
In an electron gun disclosed in U.S. Pat. No. 5,128,586, an electron beam passing hole is formed by penetrating an indented portion having a horizontally elongated shape at the side to which an electron beam is input and an indented portion having a vertically elongated shape at the side from which the electron beam is output. In the electron gun having the above control electrode, distortion of the electron beam at the periphery of a screen is compensated for by moving the position of a crossover point in the vertical direction rather than in the horizontal direction toward a screen. However, since the diameter of a vertical electron beam passing through the rectangular electron beam passing hole which is penetrated by the horizontally elongated and vertically elongated indented portions is small, the control electrode interferes with a mask having a function of color selection of the electron beam during scanning so that moiré of an image occurs.
U.S. Pat. No. 5,760,550, issued to Sukeno et al., entitled COLOR PICTURE TUBE, discloses a color cathode ray tube having an electron gun in which an electron beam passing hole of a control electrode is formed to be non-circular.
While U.S. Pat. No. 5,128,586 and U.S. Pat. No. 5,760,550 provide advantages, they appear to fail to adequately provide an efficiently and conveniently improved electron gun.
SUMMARY OF THE INVENTION
To solve the above-described problems and others, it is an object of the present invention to provide an electron gun for a color cathode ray tube (CRT) which makes the strength of an electron lens different in the horizontal direction and the vertical direction at the triode portion, so that defocusing by the deflection yoke is minimized, and moiré of the image is prevented.
To solve the above-described problems and others, it is a further object of the present invention to provide an electron gun for a color cathode ray tube which makes the strength of an electron lens different in the horizontal direction and the vertical direction at the triode portion, so that the horizontal resolution of an image can be improved and a vertical focus property of the image can be improved.
To achieve the above objects and others, there is provided an electron gun for a color cathode ray tube which comprises a cathode which is a source for emitting an electron beam, a control electrode, through which the electron beam emitted from the cathode passes, having first electron beam passing holes each including a first vertically elongated indented portion formed at an output side surface of the control electrode and a first electron beam passing hole portion formed in the first indented portion, a screen electrode installed adjacent to the control electrode and having second electron beam passing holes formed in the screen electrode, and focusing electrodes sequentially installed from the screen electrode.
It is preferred in the present invention that the first electron beam passing hole portion formed in the first indented portion has a circular or rectangular shape and that the second electron beam passing hole portion formed in the screen electrode has a circular or vertically elongate rectangular shape.
Alternatively, to achieve the above objects and others, there is provided an electron gun for a color cathode ray tube which comprises a cathode which is a source for emitting an electron beam, a control electrode, through which the electron beam emitted from the cathode passes, having first electron beam passing holes each including a first vertically elongated indented portion formed at an output side surface of the control electrode and a first electron beam passing hole portion formed in the first indented portion, a screen electrode installed adjacent to the control electrode and having second electron beam passing holes formed in the screen electrode, a plurality of focusing electrodes for forming a plurality of quadrupole lenses, sequentially installed from the screen electrode and respectively having electron beam passing holes having a predetermined shape.
Alternatively, to achieve the above objects and others, there is provided an electron gun sack for a color cathode ray tube which comprises a cathode which is a source for emitting an electron beam, a control electrode, through which the electron beam emitted from the cathode passes, having first electron beam passing holes each including a first vertically elongated indented portion formed at an output side surface of the control electrode and a first electron beam passing hole portion formed in the first indented portion, a screen electrode installed adjacent to the control electrode and having second electron beam passing holes formed in the screen electrode, a plurality of first, second, and third focusing electrodes respectively having electron beam passing holes having a predetermined shape, a fourth focusing electrode installed adjacent to the third focusing electrode, for forming a first quadrupole lens, a fifth focusing electrode installed adjacent to the fourth focusing electrode, for forming a second quadrupole lens, and a final acceleration electrode installed adjacent to the fifth focusing electrode, for forming a main lens.
It is preferred in the present invention that vertically elongated electron beam passing holes are formed at an output side surface of each of the third and fourth focusing electrodes, horizontally elongated electron beam passing holes are formed at an input side surface of each of the fourth and fifth focusing electrodes, a constant voltage is applied to the screen electrode and the second focusing electrode, a focusing voltage higher than the constant voltage is applied to the first focusing electrode and the fourth focusing electrode, and a dynamic focusing voltage using the focusing voltage as a base voltage is applied to the third and fifth focusing electrodes.
To achieve these and other objects in accordance with the principles
An Sung-Jun
Kim Do-Hyoung
Song Yong-Seok
Bushnell , Esq. Robert E.
Samsung SDI & Co., Ltd.
Vo Tuyet Thi
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