Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Reexamination Certificate
1999-07-29
2001-11-20
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
C315S014000, C315S016000, C313S449000, C313S414000, C313S429000
Reexamination Certificate
active
06320333
ABSTRACT:
TECHNICAL FIELD
This invention relates to a color picture tube, and more specifically a color picture tube with an improved electron gun that can provide a high definition image over a whole screen.
BACKGROUND ART
To attain high image resolutions over the entire screen, it is necessary to obtain a small beam spot diameter in a peripheral area as well as a center area of the screen. If a focus voltage is a constant value and adjusted so that the smallest beam spot diameter can be obtained in the center portion, overfocussing may occur in the peripheral portion of the screen, and the beam spot diameter may grow in the peripheral portion.
“Dynamic focussing”, which changes the focus voltage in synchronization with the deflection of the electron beam, is a conventional method with which an optimal focus can be attained over the entire screen (see Tokukaisho 61-99249, for example). In this conventional method, first and second focussing electrodes are provided, and a voltage applied to the second focussing electrode is raised along with an increasing deflection angle of the electron beam so that a main lens formed between the second focussing electrode and a final accelerating electrode is weakened. Thus, overfocussing is compensated in the peripheral portion of the screen.
Additionally, in the above mentioned prior art disclosed in Tokukaisho 61-99249, a so-called “four-pole lens” is formed between the first and second focussing electrodes to compensate a non-axisymmetric beam spot distortion in the peripheral portion of the screen. This four-pole lens is formed by providing vertical oblong through holes in the first focussing electrode and horizontal oblong through holes in the second focussing electrode for passing electron beams, for example.
Another prior art disclosed in Japanese laid open patent application (Tokukaihei) 8-22780 is a method for increasing the beam spot diameter along with raising the current density of the electron beam, and compensating a deterioration of image resolution in the peripheral portion of the screen that is caused by a non-axisymmetric distortion of the beam spot due to a spherical aberration of the main lens. In this prior art, a tube-like intermediate auxiliary electrode is provided between the focussing electrode and the final accelerating electrode, and the intermediate auxiliary electrode is supplied with a voltage between the focus voltage and an anode voltage (voltage applied to the final accelerating electrode). Thus, a potential gradient in the axial direction of the main lens becomes gentle, so that the spherical aberration of the main lens can be reduced.
It is a first object of the present invention to raise the resolution over the entire screen by combining two such prior art methods as described above. It is a further object of the present invention to solve the problems occurring when these two prior art method are combined, that is, the shifting of the beam spot, and a difference of focussing ability between horizontal and vertical directions.
DISCLOSURE OF THE INVENTION
A color picture tube of the present invention comprises three inline cathodes, aligned in the horizontal direction, a focussing electrode supplied with a focus voltage, a final accelerating electrode supplied with an anode voltage, and an intermediate auxiliary electrode arranged between said focussing electrode and said final accelerating electrode. A means for separating three electrostatic lenses is provided inside at least one of the focussing electrode and said final accelerating electrode. The intermediate auxiliary electrode has one through hole for passing electron beams, which is shared by three electron beams. The intermediate auxiliary electrode is supplied with a voltage between the focus voltage and the anode voltage. A main lens is formed by said focussing electrode, said intermediate auxiliary electrode and said final accelerating electrode. A non-axisymmetric electrostatic lens for focussing electron beams in the horizontal direction and diverging them in the vertical direction is formed between said main lens and said cathode. A power of said non-axisymmetric electrostatic lens changes in correspondence to a deflection angle of the electron beams.
It is preferable that the focussing electrode includes a first focussing electrode on the cathode side and a second focussing electrode on the screen side, said non-axisymmetric electrostatic lens is formed between said first and second focussing electrodes, said intermediate auxiliary electrode and said first focussing electrode are supplied with voltages obtained by dividing the anode voltage with resistors, and said second focussing electrode is supplied with a dynamic voltage that changes in accordance with a deflection angle of the electron beams.
In an embodiment of the present invention, it is preferable that said focussing electrode includes a first focussing electrode on the cathode side and a second focussing electrode on the screen side, said non-axisymmetric electrostatic lens is formed between said first and second focussing electrodes, said first focussing electrode is supplied with a substantially constant focus voltage, said second focussing electrode is supplied with a dynamic voltage that changes in accordance with a deflection angle of the electron beam, and said intermediate auxiliary electrode is supplied with a voltage generated by dividing the anode voltage with resistors.
As another embodiment of the present invention, it is preferable that said focussing electrode includes a first focussing electrode on the cathode side and a second focussing electrode on the screen side, said non-axisymmetric electrostatic lens is formed between the first and second focussing electrodes, said first focussing electrode is supplied with a substantially constant focus voltage, said second focussing electrode is supplied with a dynamic voltage that changes in accordance with a deflection angle of the electron beam, and said intermediate auxiliary electrode is supplied with a voltage generated by dividing a voltage between said final accelerating electrode and said second focussing electrode with resistors.
With these configurations, the dynamic voltage enhances focus performance in the peripheral portions of the screen, while an electrode configuration with reduced spherical aberration of the main lens, and a more rational voltage supply for the electrodes are attained. Thus, distortions and shifts of the beam spot on the screen are suppressed, so that a high resolution image can be obtained over the whole screen.
It is even more preferable that a second non-axisymmetric electrostatic lens for diverging electron beams in the horizontal direction and focussing them in the vertical direction is formed between said non-axisymmetric electrostatic lens and said cathode. For example, first and second auxiliary electrodes are provided between the cathode and the first focussing electrode, the first auxiliary electrode that is closer to the cathode is connected to the first focussing electrode, the second auxiliary electrode is connected to the second focussing electrode, and the second non-axisymmetric electrostatic lens is formed between the second auxiliary electrode and the first focussing electrode.
It is also preferable that, of three non-axisymmetric electrostatic lenses that are arranged in-line, the two lenses on the sides are shifted from centers of corresponding electron beams in the in-line direction, so as to cancel a beam spot shift on the screen that may be generated when the power of said main lens and the power of said non-axisymmetric electrostatic lens are changed in accordance with a deflection angle of the electron beam.
Moreover, it is preferable, of three non-axisymmetric electrostatic lenses that are arranged in-line, the power of the lens in the center is different from the power of the lenses on the sides, so as to compensate a difference in focus power of the main lens between horizontal and vertical directions that change in accordance with a deflection angle of the electron bea
Ito Takashi
Ueda Yasuyuki
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
Philogene Haissa
LandOfFree
Color picture tube does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Color picture tube, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Color picture tube will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2571393