Projection type cathode ray tube with masking means
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United States of America Patent
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-
Dec 27, 1983
Grant Date -
N/A
app pub date -
Jan 11, 1982
filing date -
Feb 26, 1981
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A projection cathode ray tube is provided with elements for correcting a spherical aberration in the optical system. These elements include a correction lens disposed in front of the tube and a masking member adjustably mounted on the lens. The masking member partially covers peripheral surface portions of the lens in an adjustable manner to obtain a high image resolution on the screen with a minimum decrease in the image brightness. Preferably, the masking member is removable or adjustable in the form of a masking tape or divided shutter attached to partial portions of the front face of the lens for removing an undesired aberration with a minimized shuttering area. The projection tube comprises in combination with the correction lens, a tube envelope including a convex target and a concave mirror disposed opposite to each other and having the same center of curvature. This structure with the adjustable masking achieves a high quality reception or image projection.
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