Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Patent
1979-08-24
1982-05-25
Blum, Theodore M.
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
315 13C, H01J 2970, H01J 2976
Patent
active
043319068
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a shadow-mask color cathode ray tube apparatus (which is called hereinafter a CRT apparatus), and more specifically to a color character display in which good convergence correction is provided following up deflections of electron beams.
BACKGROUND ART
The convergence correction in conventional cathode ray tube (which is called hereinafter a CRT) apparatus have obtained the desired convergence correcting magnetic field by flowing respectively the horizontal or vertical convergence coil with a current proportional to a parabolic waveform obtained by integrating the horizontal deflecting current or the vertical deflecting current with respect to time respectively. In such apparatus uniform convergence correction is only effected over the entire picture surface, and there have been the disadvantages that it is very difficult to effect the correction with a high accuracy over the entire picture surface and so on.
DISCLOSURE OF THE INVENTION
The present invention has been made in order to eliminate the prior art disadvantages as described above and is arranged to generate signal voltages substantially equal to ae.sub.X.sup.2 and bee.sub.Y.sup.2 (where a and b are variable constants or constants individually variable in accordance with the polarity of e.sub.X and e.sub.Y) from an X deflecting signal e.sub.X and a Y deflecting signal e.sub.Y, compare these signal voltages with a reference voltage e.sub.CX or e.sub.CY separately generated thereby to partition a picture surface of a CRT into a central portion and a peripheral portion (a left/right and an upper/lower end), generate different adjustable correction signal voltages for the central and peripheral portions thus partitioned and pass convergence currents corresponding to those correction signal voltages through the convergence coil respectively. The picture surface of the CRT is partitioned into the central portion where the convergence is easily effected and the peripheral portion where the convergence is bad and further the partitioned central or peripheral portion is divided into the upper/lower part and the left/right part thereby to make it possible to adjust separately the convergence. Since the temporal characteristics of the deflection is not pertinent, it is possible to be applied to the display of color images resulting from not only the raster scanning but also random scannings and its effect is great.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating a general construction of a cathode ray apparatus using a shadow-mask CRT;
FIG. 2 is a block diagram illustrating one embodiment of a convergence correction circuit according to the present invention;
FIGS. 3A-3C are explanatory diagrams for explaining the operation, thereof;
FIG. 4 is a diagram illustrating an example of a construction of the polarity discrimination circuit and coefficient circuit portions thereof;
FIG. 5 is a block diagram illustrating another embodiment of the present invention;
FIG. 6 is a diagram illustrating an example of a construction of the coefficient circuit portion thereof; and
FIG. 7 is a block diagram illustrating still another embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
In order to facilitate an understanding, an outline of the present invention is described. The present invention is to generate a signal that is ae.sub.X.sup.2 +be.sub.Y.sup.2 from an X and a Y deflecting signal e.sub.X and e.sub.Y supplied to a CRT apparatus and flow a convergence coil with a current proportional to the signal voltage while partitioning a picture surface of a CRT into a central portion and a peripheral portion at a position of ae.sub.X.sup.2 =e.sub.CX in the direction of the X axis and at a position of be.sub.Y.sup.2 =e.sub.CY in the direction of the Y axis and making it possible to adjust the convergence separately on the partitioned central and peripheral portions. In more detail, said picture surface of the CRT is partitioned into the upper and lower sides and the left a
REFERENCES:
patent: 3735191 (1973-05-01), Peter
patent: 3891889 (1975-06-01), Fazio
patent: 3942067 (1976-03-01), Cawood
Fujino Junichi
Ikehata Shigeki
Miyazaki Hideto
Blum Theodore M.
Mitsubishi Denki & Kabushiki Kaisha
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