Shadow mask for color CRT having different vertical pitch for ou

Details Shadow mask for color CRT having different vertical pitch for ou Shadow mask for color CRT having different vertical pitch for ou

1998-09-25

2000-12-05

Day, Michael H.

Electric lamp and discharge devices

Cathode ray tube

Shadow mask, support or shield

313403, 313408, H01J 2980

Patent

active

061571202

ABSTRACT:
A color cathode ray tube (CRT) employs a color selection electrode in the form of a thin shadow mask located adjacent the CRT's display screen and having an array of electron beam passing apertures arranged in vertical columns and horizontal rows. To correct for electron beam landing tilt of three inline electron beams on the CRT's display screen arising from the spherical shape of the CRT's shadow mask and display screen, the shadow mask is provided with a two-step function defining the vertical pitch (P.sub.v) of its apertures, or the vertical spacing between adjacent apertures not in the same vertical column. A first quadratic equation is used for defining the vertical pitch of the shadow mask's beam passing apertures covering a first generally flat inner area of the CRT's display screen from the center of the display screen out to where its radius of curvature substantially decreases adjacent its periphery. A second quadratic equation defines the vertical pitch of the shadow mask's beam passing apertures covering the more highly curved, peripheral portion of the display screen to correct for electron beam landing tilt and provide improved video image color purity tolerance. The two-step vari-bow shadow mask employing dual vari-Pv quadratic equations reduces electron beam landing tilt and increases color purity tolerance in areas adjacent to the margin of the effective viewing area of the display screen without reducing the screen's effective viewing area while maintaining a high degree of video image color purity.

REFERENCES:
patent: 3735190 (1973-05-01), Say
patent: 4623818 (1986-11-01), Yamazaki
patent: 5072150 (1991-12-01), Lee
patent: 5243253 (1993-09-01), Marks et al.
patent: 5534746 (1996-07-01), Marks et al.
patent: 5633558 (1997-05-01), Watanabe et al.
patent: 5917273 (1999-06-01), Watanabe et al.

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