Electron gun with large aperture auxiliary electrode

An electron gun comprising:

• means for emitting three electron beams;
• main lens means for focusing the electron beams, the main lens means having electron beam paths through which said electron beams pass and including first and second electrodes arranged along the beam paths, said first and second electrodes each having three apertures through which the respective electron beams pass, said main lens means further including an auxiliary electrode located between the first and second electrodes and having an aperture through which each of the electron beams pass, the diameter of the aperture of the auxiliary electrode being greater than the respective sums of the diameters of the three apertures of the first and second electrodes;
• and
• voltage applying means for respectively applying first, second and auxiliary voltages to the first, second and auxiliary electrodes, the first, second and auxiliary voltages having different first, second and third voltage levels, respectively, thereby forming an electrostatic field between the first and second electrodes, wherein the third voltage level is higher than the first voltage level and lower than the second voltage level.