Projection type cathode ray tube having improved focus characteristics
AssigneeHitachi Display, Ltd.
InventorGo Uchida
Life of this patent
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Abstract
A projection type cathode ray tube includes a phosphor screen, a cathode, G1, G2 and a main lens composed of first, second and third electrodes. The first and third electrodes are supplied with an anode voltage of the phosphor screen, and the second electrode is supplied with a focus voltage lower than the anode voltage. An inside diameter of an opening in a phosphor screen side end of the second electrode is from 14 mm to 18 mm, and the phosphor screen side end of the second electrode is disposed within the third electrode. An aperture diameter D mm in the G1 electrode and an axial length L mm of the second electrode satisfy the following inequalities: L mm≧60×D mm+27.6 mm, L mm≦−646×D mm+396.3 mm, D mm≧0.44 mm, and L mm≦75 mm.
Claims20
A projection type cathode ray tube comprising:
- a glass envelope comprising a panel portion, a neck portion, and a funnel portion connecting said panel portion and said neck portion;
- a phosphor screen formed on an inner surface of said panel portion;
- and
- an electron gun housed within said neck portion and emitting an electron beam toward said phosphor screen,
- wherein said electron gun is provided with an electron beam generating section which comprises a cathode provided with an electron-emissive material, a G1 electrode for controlling said electron beam and a G2 electrode for accelerating said electron beam arranged in the order named, and a main lens which comprises a first cylinder electrode, a second cylinder electrode and a third cylinder electrode arranged in the order named from a cathode side of said main lens and focuses said electron beam from said electron beam generating section on said phosphor screen,
- wherein said first cylinder electrode and said third cylinder electrode are configured so as to be supplied with a voltage equal to an anode voltage applied to said phosphor screen, and said second cylinder electrode is supplied with a focus voltage lower than said anode voltage,
- wherein an inside diameter of an opening in an end of said second cylinder electrode on a phosphor screen side thereof is in a range of from 14 mm to 18 mm, and said end of said second cylinder electrode on said phosphor screen side thereof is disposed within said third cylinder electrode, and
- wherein an aperture diameter D mm in said G1 electrode and an axial length L mm of said second cylinder electrode satisfy the following inequalities:
- L mm≧60×D mm+27.6 mm,
- L mm≦−646×D mm+396.3 mm,
- D mm≧0.44 mm,
- and
- L mm≦75 mm.
Dependencies are inferred from the claim text.