Multi-layer common lens arrangement for main focus lens of multi-beam electron gun

A charged electrode in an electron gun forming an electrostatic focusing field for focusing a center and two outer electron beams on a display screen of a color cathode ray tube (CRT) in forming a video image on said screen, wherein said three electron beams are directed along respective parallel axes, said electrode comprising:

• a hollow housing including first wall means for defining three inline apertures and a thin side wall forming lateral portions of said housing, wherein each of said inline apertures is aligned with a respective one of said axes for passing a respective one of said electron beams;
• second wall means disposed on an end of said hollow housing and extending inwardly toward the electron beam axes from said side wall for defining a first elongated common aperture aligned generally transverse to said axes, wherein the center and two outer electron beams are directed through said first elongated common aperture;
• and
• third wall means disposed within said hollow housing between said first and second wall means and extending inwardly toward the electron beam axes from the side wall for defining a second elongated common aperture aligned with said first elongated common aperture for passing the center and two outer electron beams, wherein said second and third wall means increase the effective electrostatic focusing field radius of the electrode and the length of the electrostatic focusing field along said axes for improved electron beam focusing on the display screen.

For use in an electron gun in a multi-electron beam video display device, wherein said electron beams are directed along respective parallel axes onto a display screen for providing a video image thereon, a focus lens through which said electron beams are directed for focusing the electron beams on the display screen, said focus lens comprising:

• a first charged grid including a first hollow housing with first and second opposed ends and a first thin side wall disposed about said first housing and forming lateral portions thereof, said first charged grid further including first plural wall means disposed in said first hollow housing in a spaced manner along the electron beam axes and extending inwardly toward the electron beam axes from said side wall for defining first plural spaced common apertures, and wherein said first plural common apertures are aligned with the electron beam axes for passing the electron beams;
• and
• a second charged grid including a second hollow housing with first and second opposed ends and a second thin side wall disposed about said second housing and forming lateral portions thereof, said second charged grid further including second plural wall means disposed in said second hollow housing in a spaced manner along the electron beam axes and extending inwardly toward the electron beam axes from said second side wall for defining second plural spaced common apertures, and wherein said second plural common apertures are aligned with the electron beam axes for passing the electron beams and said first and second plural common apertures are in facing relation.