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US 4,230,972 AGranted
Dynamic focus circuitry for a CRT data display terminal
AssigneeMotorola, Inc.
InventorMichael P. Bafaro
Life of this patent
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Abstract
Dynamic focus circuitry for a CRT data display terminal provides high resolution even in the corners of the screen by means of a dynamic focus voltage which is the product of parabolic waveforms at horizontal line rate and vertical frame rate. The non-linear characteristic of a diode provides the product function at minimum expense.
Claims3
In a cathode ray tube device requring high resolution as for data display, the combination comprising:
- means for supplying an electron beam;
- focusing means positioned to focus said electron beam;
- high voltage supply means coupled to the focusing element for supplying an adjustable DC focus voltage;
- first circuit means coupled to the focusing element for supplying a signal having a parabolic waveform at the vertical frame rate;
- second circuit means coupled to the focusing element for supplying a second signal having a parabolic waveform at the horizontal line rate;
- and
- circuit means coupled to the focusing element for multiplying the output signals of the first and second circuit means to provide a dynamic focusing voltage.
4 more elements
Dependencies are inferred from the claim text.