| 摘要 |
In a multi-stage, multi-beam electron gun of the common lens type for use in a color cathode ray tube (CRT), a charged grid in the prefocus lens of the electron gun is provided with three inline asymmetric beam passing apertures. The three asymmetric apertures may be either in the G4 grid, in the upper side of the G3 grid, or on the lower side of the G5 grid, i.e., in facing relation to the G4 grid, or may be incorporated in both the G3 and G5 grids. The small G3-G4 and G4-G5 spacing gives rise to isolation of the electron optic lenses of the two outer electron beams from that of the center electron beam allowing the asymmetric auxiliary apertures to asymmetrically and independently correct for electron beam astigmatism, i.e., the difference between the beam's horizontal and vertical focus voltage, and differences in the focus voltages of the two outer electron beams relative to the center electron beam. Each of the three inline apertures includes a circular center portion with an overlapping (or superimposed) elliptically shaped aperture. The elliptical aperture may be aligned generally vertically or generally horizontally, and the two outer electron beam passing apertures may be larger or smaller in diameter than the center aperture. In the two outer electron beam passing apertures, the superimposed elliptically shaped aperture may be horizontally offset (either outwardly or inwardly relative to the circular center portion) for controlling static convergence of the three electron beams.
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