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US 4,542,320 AGranted
Cathode ray tube
AssigneeMatsushita Electronics Corporation
InventorsHiroshi Suzuki, Masao Natsuhara, Chisato Kurusu
Life of this patent
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Abstract
Distance between the second grid (G2) and the third grid (G3) is selected very short and electron beam passing apertures of the second grid (G2) and the third grid (G3) are selected small; the cathode ray tube has small beam spot both at small current and large current operations.
Claims7
A cathode ray tube comprising an electron gun, a fluorescent screen and an evacuated enclosure enclosing said electron gun and said fluorescent screen therein,
- said electron gun comprising at least
- a cathode,
- a first grid (G1) as a control grid,
- a second grid (G2) on which an accelerating potential is to be applied,
- a third grid (G3) on which a focussing potential is to be applied,
- which are disposed in this sequential order and impressed with such predetermined potentials that:
- maximum of the first derivative of the axial potential of said electron gun within a range between said second grid (G2) and said third grid (G3) is in a range from 5.times.10.sup.4 V/cm to 5.times.10.sup.5 V/cm, and
- maximum value and minimum value of the second derivative of said axial potential of said electron gun are located at the distances on the axis determined from following relations:
- 1.0 D.sub.1 .ltoreq.Z.sub.1 .ltoreq.2.0 D.sub.1
- and
- 0.5 D.sub.1 .ltoreq.Z.sub.2 -Z.sub.1 .ltoreq.1.2 D.sub.1,
- wherein
- Z.sub.1 and Z.sub.2 are the distances on the axis of said electron gun from electron beam emitting face of said cathode to points of said maximum value and a minimum value of said second derivative, respectively, and
- D.sub.1 is diameter of electron passing aperture of said first grid (G1).
11 more elements
Dependencies are inferred from the claim text.