Electric lamp and discharge devices: systems – Cathode ray tube circuits – Plural concentrating – accelerating – and/or de-accelerating...
Patent
1979-09-28
1982-06-08
Blum, Theodore M.
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Plural concentrating, accelerating, and/or de-accelerating...
315 31R, 313449, H01J 2946, H01J 2956
Patent
active
043341705
ABSTRACT:
A novel electron gun for use in television cathode ray tubes of the direct view or projection type is disclosed. The cathode ray tube has associated therewith a power supply for developing a predetermined pattern of operating voltages including first and second adjustable voltages. The electron gun has apertured electrodes aligned on an axis for receiving the operating voltages to produce a focused beam of electrons. The electron gun comprises lower end means for generating an electron beam having a crossover. The beam expands in the aperture of a prefocusing electrode following the crossover and the outer rays of the expanding beam define a half-angle with respect to the axis. The tube also comprises main focus lens means adjacent to the prefocusing electrode for receiving the expanding beam and focusing the beam to form a beam spot of minimum size at a predetermined distance from the gun. The main focus lens means has at least a focusing electrode for receiving the first adjustable voltage for focusing the beam spot. The main focus lens means, by its inherent characteristics, is capable of focusing a minimum beam spot whose size is a function of the beam half-angle. The gun according to the invention is characterized by having at least one-half angle control element located in the region between the lower end means and the focus lens means and relatively widely spaced from the prefocusing electrode. The aperture of said control element is relatively larger than the aperture of the prefocusing electrode. Means are provided for receiving a second adjustable voltage from the power supply and applying the voltage to the control element for increasing or decreasing the strength of its half-angle control field and hence increasing or decreasing the half-angle. Means are provided for fixing the second adjustable voltage for maintaining a selected constant optimum voltage on the control element effective to cause the size of the focused beam spot to remain essentially minimum for equal focus voltage at different current levels.
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patent: 4009410 (1977-02-01), Pommier et al.
patent: 4095138 (1978-06-01), Schwartz
patent: 4168452 (1979-09-01), Christensen et al.
I. M. Wilson, Theoretical and Practical Aspects of Electron-Gun Design for Color Picture Tubes, IEEE Transactions on Consumer Electronics, vol. CE-21, No. 1, Feb. 1975, pp. 32-38.
Blum Theodore M.
Clarke, Jr. Ralph E.
Zenith Radio Corporation
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