Dynamic focusing circuit for a cathode ray tube

Details Dynamic focusing circuit for a cathode ray tube Dynamic focusing circuit for a cathode ray tube

1980-07-30

1982-03-02

Blum, Theodore M.

Electric lamp and discharge devices: systems

Cathode ray tube circuits

Cathode-ray deflections circuits

315 31TV, H01J 2958

Patent

active

043180337

ABSTRACT:
There is disclosed herein a dynamic focusing circuit for the minor deflection circuit, hereinafter referred to as to the vertical deflection circuit, for a cathode ray tube to compensate for defocusing characteristics thereof. Such a cathode ray tube employs a major deflection circuit, hereinafter referred to as the horizontal deflection circuit, for deflecting the beam along a horizontal axis at a relatively high raster scan frequency, such as on the order of 28 KHz. Additionally such a cathode ray tube has associated therewith a minor deflection circuit for deflecting the beam along the vertical axis at a second substantially lower scan frequency and which may be on the order of 50 Hz. A focusing circuit normally receives a steady state DC focusing signal for focusing the beam as it is scanned along the respective horizontal and vertical axes. A nonresonant focus correction circuit supplies a correction signal to the focusing circuit for compensating for the defocusing of the beam as it is scanned along the vertical axis. The nonresonant focus correction circuit employs circuitry for providing a sinusoidal signal having a frequency on the order of one-half that of and synchronized to that of the vertical scan frequency together with circuitry that responds to the sinusoidal signal for providing therefrom a correction signal having a generally parabolic shape.

REFERENCES:
patent: 3412281 (1968-11-01), Richards, Jr. et al.

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