Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Patent
1996-08-05
1998-10-06
Dombroske, George
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
313413, 313414, H01J 2950
Patent
active
058181563
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a color cathode-ray tube and particularly to a color cathode-ray tube equipped with an electron gun capable of obtaining good resolution by improving focusing characteristics over the whole fluorescent plane and over the whole current zone of an electron beam, the color cathode-ray tube employing deflecting yokes of a short overall length and of a low cost, enabling the depth of the cabinet of the picture display device to be shortened.
BACKGROUND ART
In a cathode-ray tube equipped with at least an electron gun constituted by a plurality of electrodes, a deflecting device and a fluorescent screen (screen having a phosphor coating), the following technologies have heretofore been known as means for obtaining good reproduced picture from the center up to the periphery of the fluorescent screen.
Technology in which coma correction coils are provided at right and left positions on the deflection yokes close to a neck portion of the cathode-ray tube that use three electron beams arranged in line, in order to correct the coma (Japanese Utility Model Laid-Open No. 40944/1985).
Technology in which narrow pieces of a magnetic material are arranged near the apertures for passing electron beams of both sides among the three electron beams arranged in line on the bottom surface of a shield cup of an electron gun that uses three electron beams arranged in line, in order to adjust the amounts of deflection individually for the electron beams of both sides and for the central electron beam (Japanese Patent Laid-Open No. 82770/1973).
Technology in which two pieces of upper and lower parallel flat-plate electrodes are arranged being faced to the main lens sandwiching the passage of three electron beams, the two pieces of upper and lower parallel flat-plate electrodes being installed on the bottom surface of a shield cup of an electron gun which uses three electron beams arranged in line (Japanese Patent Publication No. 52586/1992).
Technology in which two pieces of upper and lower parallel flat-plate electrodes are arranged being directed to the fluorescent screen from a portion opposed to the main lens in an electron gun which uses three electron beams arranged in line, the three electron beams being sandwiched between the two pieces of upper and lower parallel flat-plate electrodes in parallel with the in-line direction, in order to shape the electron beams before the electron beams enter into the deflecting magnetic field (U.S. Pat. No. 4,086,513, Japanese Patent Publication No. 7345/1985).
There can be further quoted technology in which an electrostatic quadrupole lens is formed between electrodes in a portion of an electron gun, and the strength of the electrostatic quadrupole lens is dynamically changed depending upon the deflections of the electron beams in order to uniformalize the picture on the whole screen (Japanese Patent Laid-Open No. 61766/1976); technology in which an astigmatic lens is provided in a region of electrodes (second electrode and third electrode) forming a spare focusing lens (Japanese Patent Laid-Open No. 18866/1978); technology in which apertures in the first electrode and in the second electrode for passing electron beams are transversely elongated or the electrodes are formed in different shapes in an electron gun that use three electron beams arranged in line, or the transverse-to-longitudinal ratio of the apertures for passing the electron beams in a central electron gun is set to be smaller than that of side electron guns (Japanese Patent Laid-Open No. 64368/1976); and technology in which an asymmetrical lens is created by slits formed in the third electrodes on the cathode side in the electron guns arranged in line, and the slits in the axial direction of the electron guns are formed deeper toward the center beam than toward the side beams, so that electron beams are projected onto the fluorescent screen through the asymmetrical lens of at least one place (Japanese Patent Laid-Open No. 81736/1985).
The focusing characteristics in the c
REFERENCES:
patent: 4725763 (1988-02-01), Okuyama et al.
patent: 4900979 (1990-02-01), Shimoma et al.
patent: 5157301 (1992-10-01), Tominaga et al.
patent: 5384512 (1995-01-01), Kamoharu et al.
Dombroske George
Hitachi , Ltd.
Patel Harshad
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