Color cathode ray tube having electrostatic quadrupole lenses

A color cathode ray tube comprising an evacuated envelope comprising a panel portion, a neck portion and a funnel portion for connecting said panel portion and said neck portion, a phosphor screen formed on an inner surface of said panel portion, an in-line type electron gun housed in said neck portion, and an electron beam deflection yoke mounted around said neck portion,

• said in-line type electron gun comprising
• an electron beam generating section having a plurality of in-line cathodes, a first electrode serving as an electron beam control electrode and a second electrode serving as an accelerating electrode arranged in the order named for projecting a plurality of electron beams arranged approximately in parallel with each other in a horizontal plane toward said phosphor screen,
• an electron beam focusing section comprising a third electrode, a fourth electrode, a fifth electrode and an anode arranged in the order named for focusing said plurality of electron beams on said phosphor screen,
• said third electrode comprising a first group of members and a second group of members,
• said fifth electrode comprising a first group of members and a second group of members of said fifth electrode,
• said first group of members of said third electrode and said first group of members of said fifth electrode being supplied with a first focus voltage of a fixed value, and
• said second group of members of said third electrode and said second group of members of said fifth electrode being supplied with a second focus voltage comprised of a fixed voltage and a dynamic voltage varying with deflection of said plurality of electron beams, wherein
• at least one first-type electrostatic quadrupole lens is formed between said first and second groups of members of said fifth electrode for increasingly focusing said plurality of electron beams in one of horizontal and vertical directions and for increasingly diffusing said plurality of electron beams in another of the horizontal and vertical directions with an increase in a focus voltage difference between said first focus voltage and said second focus voltage,
• at least one second-type electrostatic quadrupole lens is formed between said first and second groups of members of said third electrode for increasingly focusing said plurality of electron beams with the increase in the focus voltage difference in a direction perpendicular to said one of the horizontal and vertical directions in which one of said at least one first-type electrostatic quadrupole lens which is disposed nearest said anode increasingly focuses said plurality of electron beams with the increase in the focus voltage difference, and for increasingly diffusing said plurality of electron beams with the increase in the focus voltage difference in a direction perpendicular to said another of the horizontal and vertical directions in which said one of said at least one first-type electrostatic quadrupole lens which is disposed nearest said anode increasingly diffuses said plurality of electron beams with the increase in the focus voltage difference, and
• an electron lens is formed between said fourth electrode and a first aperture formed in a first surface of one member of said second group of said third electrode adjacent to said fourth electrode and forming another of said at least one second-type electrostatic quadrupole lens in combination with one member of said first group of said third electrode, said first surface of said one member of said second group of said third electrode being on a side of said one member of said second group of said third electrode opposite from said fourth electrode,
• said electron lens being configured so as to increasingly diffuse said plurality of electron beams in the horizontal direction with an increase in a voltage difference between said second focus voltage and a voltage applied to said fourth electrode and to increasingly focus said plurality of electron beams in the vertical direction with the increase in the voltage difference between said second focus voltage and the voltage applied to said fourth electrode.