Electronic CRT centering alignment apparatus
AssigneeHughes Aircraft Company
InventorMalcolm Macaulay
Life of this patent
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Abstract
An electronic CRT centering alignment apparatus is disclosed. The apparatus includes a pair of zero crossing detectors, one sensing CRT horizontal deflection current, the other sensing CRT vertical deflection current. The zero crossing detectors are employed by the apparatus to generate video signals to mark the center of deflection of the CRT and to delineate the horizontal and vertical axes of deflection.
Claims9
Apparatus for indicating the deflection alignment of a raster-scanned CRT display, comprising:
- means responsive to the CRT display horizontal deflection signal for generating a horizontal zero pulse each time a zero crossing is detected during an active scan interval of the CRT display;
- means responsive to the CRT display vertical deflection signal for generating a vertical zero pulse each time a zero crossing is detected during an active scan interval of the CRT display;
- video signal generator responsive to said horizontal zero pulse for generating a first CRT beam control signal in response to said horizontal zero pulse, said first CRT control signal generating a vertical line on the CRT marking the vertical deflection axis and the electrical center of horizontal deflection, said generator further responsive to said vertical zero pulse for generating a second CRT beam control signal in response to said vertical zero pulse, said second CRT control signal generating a horizontal raster scanned line on the CRT marking the horizontal deflection axis and the electrical center of vertical deflection.
An electronic apparatus for indicating the deflection alignment of a raster-scanned cathode ray tube (CRT), characterized by horizontal and vertical sawtooth deflection signals respectively proportional to the respective currents in the horizontal and vertical deflection yokes, comprising:
- means responsive to the horizontal deflection signal for generating a horizontal signal which is true only during the active horizontal scanning interval of the CRT;
- means responsive to the vertical deflection signal for generating a vertical signal which is true only during the active vertical scanning interval;
- means responsive to said horizontal and vertical signals for generating a CRT scan active signal that is true only during active scanning of the CRT;
- horizontal zero crossing detector means responsive to said horizontal deflection signal for generating a video pulse whenever a zero crossing is detected of the horizontal detector signal;
- means responsive to said video pulse and said CRT scan active signal for providing a CRT beam intensity control signal whenever a video pulse is generated and the CRT scan active signal is true, thereby marking the vertical deflection axis and the electrical center of horizontal deflection;
- vertical zero crossing detector means responsive to said vertical deflection signal for generating a vertical zero crossing signal when a zero crossing is detected;
- and
- means responsive to said vertical zero crossing signal and said CRT scan active signal for generating a video signal for drawing a horizontal line to mark the electrical center of vertical deflection.
Dependencies are inferred from the claim text.