The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 21, 1987
Filed:
Dec. 04, 1984
Johannes H van Roosmalen, Eindhoven, NL;
U.S. Philips Corporation, New York, NY (US);
Abstract
A display tube comprising in an evacuated envelope (1) an electron gun system (6) for generating and focusing by means of a focusing lens at least two electron beams (28 to 35) on a display screen (5), which electron beams are deflected by deflection means and describe a frame on the display screen. The electron gun system (6) comprises at least two electron sources (20 to 26), the electrons in each electron beam being accelerated immediately after leaving the electron source by means of an electric field having a field strength exceeding 600 V/mm. The central axes (36) of the electron beam extend substantially parallel to each other, and all beams are converged by the focusing lens in the immediate proximity of the focus of the focusing lens, after which each separate beam is focused on the display screen by the focusing lens to form a spot. The astigmatism and the coma of the focusing lens, especially for objects not situated on the tube axis, decreases rapidly with decreasing object potential with the beam aperture angle being kept the same. The electrons leave the source at a low potential and are then accelerated in a strong electric field exceeding 600 V/mm nearly immediately after leaving the electron source, thereby effecting production of a very narrow electron beam which remains narrow up to the display screen. The effect of the field curvature of the focusing lens is also considerably reduced by the narrow beams. If all electron beams through the focusing lens converge in the immediate proximity of the focus of the focusing lens, a minimum of aberrations as a result of the deflection is obtained. The electron sources are preferably P-N cathodes or diode type electron guns.