| 摘要 |
In an inline electron gun for use in a color cathode ray tube (CRT), a fixed, or static, electrostatic quadrupole in the low voltage beam forming region (BFR) exerts a negative astigmatism on the electron beams in reducing beam horizontal cross-section and compensating for the horizontal under-focusing of the beams by the CRT's self-converging magnetic deflection yoke. The negative astigmatism is compensated for by a dynamic electrostatic quadrupole in the CRT's main focusing lens. The electrostatic quadrupole in the CRT's BFR includes either a plurality of spaced, horizontally oriented, aligned, elongated indentations in the G2 facing surface of the G1 control grid or a plurality of spaced, vertically oriented, elongated indentations in the G1 facing surface of the G2 screen grid, where each of the indentations has an associated through-hole circular aperture through the grid. The elongated indentations cause the cross-section of each of the electron beams to become vertically elongated particularly in the deflection region, while the dynamic electrostatic quadrupole in the main focusing lens cancels the deflection yoke's negative astigmatism without affecting electron beam cross-section shape. This invention thus incorporates a negative astigmatism and a change of beam cross-sectional shape. The negative astigmatism is later removed at the focusing lens and the benefit of the beam shape change remains.
|
