In-line type electron gun and color picture tube apparatus using the same

An in-line type electron gun comprising:

• a focusing electrode and a final accelerating electrode that form a main lens and that are disposed at a predetermined gap, the focusing electrode having a first aperture in an end face thereof on the final accelerating electrode side and housing a first field forming electrode in a position set back from the first aperture, the final accelerating electrode having a second aperture in an end face thereof on the focusing electrode side and housing a second field forming electrode in a position set back from the second aperture,
• wherein each of the first and the second field forming electrode is provided with a central electron beam passage aperture and an aperture or a notch being disposed on each side of the central electron beam passage aperture and having an half-arc shaped portion protruding towards the central electron beam passage aperture that are disposed in an in-line arrangement, and,
• when a direction of the in-line is an X-axis direction, a direction perpendicular to the direction of the in-line is a Y-axis direction and the center of the central electron beam passage aperture is X=0 and Y=0, the central electron beam passage aperture of at least one of the focusing electrode and the final accelerating electrode has a shape that passes through intersection points of the X-axis and the Y-axis with a curve represented by an equation (X/R1)2+(Y/R)2=1 (where R1 and R2 are constants) and that has an area smaller than an area encircled by the curve.