Patent ID: 6815881
Filing Date: 2004-11-09
Classification: H01J

Abstract:
An electron gun for use in a cathode ray tube (CRT) having plural electron beams for producing a color video image on a display screen, said electron gun comprising:a cathode for providing energetic electrons; a beam forming region (BFR) aligned with said cathode and disposed intermediate said cathode and the display screen for receiving and forming said energetic electrons into a narrow beam, said BFR including plural spaced first charged grids each having one or more first aligned apertures, wherein said electrons are directed through said first aligned apertures and said electron beam increases in cross section in proceeding from said BFR toward the display screen; and an electrostatic lens disposed intermediate said BFR and the display screen and including plural spaced second grids charged by a respective focus voltage, each of said second grids having one or more second aligned apertures through which said electron beam is directed for focusing said electron beam on the display screen, wherein said second aligned apertures decrease in size in proceeding in a direction from the display screen toward said BFR for increasing focusing sensitivity of said electrostatic lens on the electron beam while decreasing said focus voltages, said electrostatic lens including a dynamic quadrupole and said second grids including a third grid having a fixed focus voltage and fourth grid having a dynamic focus voltage, said third grid including plural spaced apertures for passing a respective electron beam and said fourth grid including a single common aperture for passing said plural electron beams, said single common aperture having plural spaced enlarged portions each aligned with a respective aperture in said third grid and adapted for passing a respective electron beam, and wherein each enlarged portion is larger than an aligned beam passing aperture in said third grid, and wherein said fourth grid is disposed intermediate said third grid and the display screen.