Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Reexamination Certificate
2001-06-05
2002-12-24
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
C315S370000, C315S382000
Reexamination Certificate
active
06498443
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to color cathode ray tube (CRT) apparatus used in televisions and computer monitors, and more particular to improving the image quality of color CRT apparatus having a shortened depth by widening the maximum deflection angle.
2. Related Art
In recent years, increases in the screen size of color CRT apparatus used as televisions and computer monitors have seen a parallel demand for a reduction in the overall depth of the apparatus (hereafter, a color CRT apparatus having a horizontal deflection cycle of less than 70 kHz will be referred to as a “color TV tube apparatus” and a color CRT apparatus having a horizontal deflection cycle of 70 kHz or more will be refer to as a “color display tube apparatus”). Since manufactures are seeking to stay within the 450 mm standard depth of residential furniture, there has been a particular focus on reducing the depth of apparatus of 28 inches or larger in diagonal size, i.e., those apparatus of a size that up until now have tended to exceed this standard depth. The sought after reduction in the depth of color CRT apparatus can be achieved by widening the maximum deflection angle of the apparatus.
The maximum deflection angle is defined as the angle of an electron beam at the deflection center opened up towards the phosphor screen when the entire surface of the screen is scanned.
FIG. 1
is a perspective view of a color CRT apparatus
1
from the rear. In
FIG. 1
, the maximum deflection angle is the angle AOB, formed by diagonals A and B, originating at a phosphor screen
2
and meeting at a deflection center O. Consequently, a reduction in the depth of the color CRT apparatus
1
can be achieved by widening this maximum deflection angle AOB.
The maximum deflection angle referred to herein is calculated by doubling the largest value of the deflection angle. The deflection angle is the angle created when an electron beam emitted within a color CRT from an electron gun is deflected from a linear path by a deflection field, i.e., it is the angle opened up between the linear path and the path of the deflected electron beam.
Self-convergence, which is now standard in color CRT apparatus, corrects convergence of the three electron beams by distorting the deflection field generated by a deflection coil. Self-convergence results in the vertical deflection field being distorted into a barrel shape and the horizontal deflection field being distorted into a pincushion shape. The distortion of the horizontal deflection field becomes more pronounced as the maximum deflection angle widens.
The electron beams remain out of focused under conditions of self-convergence because of the focusing action effected on the electron beams by the horizontal deflection field (hereafter, “electromagnetic focusing effect”). Japanese Laid-Open Patent No. 61-99249 notes that this effect can be overcome by using a DAF (Dynamic Astigmatism & Focus correction) electron gun to correct focusing.
However, the fact remains that existing technology has not yet been able to satisfactorily correct for the pronounced electromagnetic focusing effect occurring in apparatus over a certain size with a wide maximum deflection angle (hereafter, such apparatus will be referred to as “wide-screen/short-depth type” apparatus).
This has meant that, to date, there have been no color TV tube apparatus of 28 inches or larger available which have a 16:9 aspect ratio and a maximum deflection angle of 110° or greater, or a 4:3 aspect ratio and maximum deflection angle of 114° or greater, and no color display tube apparatus available having a maximum deflection angle of 104° or greater. However, it is high time that wide-screen/short-depth type color CRT apparatus of greater size and maximum deflection angle were made available. The development of convergence technology is a necessary condition for this to happen.
SUMMARY OF THE INVENTION
The present invention seeks to make available wide-screen/short-depth type color CRT apparatus having a high-quality image that optimizes both the focusing and convergence of the electron beams.
The objectives of the present invention can be achieved by a color TV tube apparatus of 28 inches or larger in diagonal size, having a maximum deflection angle of 115° or greater and less than 180°, and which uses a self-convergence method; the color TV tube apparatus comprises a color TV tube, an electron gun, a deflection yoke - mounted on a funnel part of the color TV tube and having a horizontal deflection coil for generating a pincushion-shaped horizontal deflection field, wherein the horizontal deflection coil is adjusted so that a vertical focus point of an electron beam lies 50 mm or less on the inside and 30 mm or less on the outside of each edge of the effective display screen area along the horizontal axis with a focusing of an electron beam by a lensing action of the electron gun non-operational - and a convergence correction coil mounted on a neck part of the color TV tube and functioning to correct convergence.
The objectives of the present invention can also be achieved by a color display tube apparatus of 17 inches or larger in diagonal size, having a maximum deflection angle of 105° or more and less than 180°, and which uses a self-convergence method; the color display tube apparatus comprises a color TV tube, an electron gun, a deflection yoke—mounted on a funnel part of the color TV tube and having a horizontal deflection coil for generating a pincushion-shaped horizontal deflection field, wherein the horizontal deflection coil is adjusted so that a vertical focus point of an electron beam lies 20 mm or less on the inside and 50 mm or less on the outside of each edge of the effective display screen area along the horizontal axis with a focusing of an electron beam by a lensing action of the electron gun non-operational—and a convergence correction coil mounted on a neck part of the color TV tube and functioning to correct convergence.
In accordance with the above-stated conditions, wide-screen/short-depth type color CRT apparatus with a high image quality that optimize both focusing and convergence and which are not susceptible to raster distortion will be realizable.
REFERENCES:
patent: 4689525 (1987-08-01), Shimoma et al.
patent: 4701677 (1987-10-01), Ashizaki et al.
patent: 4728859 (1988-03-01), Natsuhara et al.
patent: 9-265922 (1997-10-01), None
Isayama Masayuki
Kitada Katsuhisa
Ueda Yasuyuki
Lee Wilson
Matsushita Electric - Industrial Co., Ltd.
Price and Gess
Wong Don
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