Apparatus and method for reducing the magnitude of time varying electric fields in CRT displays
AssigneeApple Computer, Inc.
InventorRichard D. Cappels
Life of this patent
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Abstract
An electric field cancellation system and method for reducing electric fields are presented, especially suited for use in reducing the magnitude of electric field emissions from a CRT display. Signals from the electric field sources of the display are used to generate counter signals of equal magnitude and opposite polarity to the source signals. These counter signals are coupled to a plurality of transmitters which effectively establish a counter electric field, or fields, of opposite polarity to the source fields. The net effect is substantial reduction in the electric field emissions from the display, and a resultant electric field of substantially reduced magnitude encountered by a display operator.
Claims20
An electric field cancellation system for use in a CRT display comprising:
- means for determining the magnitude and polarity of a source electric field in the display and developing a counter electrical signal of opposite polarity to the polarity of said source field;
- and,
- counter electric field transmitting means, coupled to said determining and developing means, for using said countersignal to establish a counter electric field of opposite polarity to said source field in a manner such that said counter electric field couples with said source electric field to produce a resultant electric field of substantially reduced magnitude in comparison to the magnitude of said source field, thereby reducing electric field emission from the display.
A method for reducing the magnitude of a source electric field generated by an electric field source, or plurality of field sources, in a CRT display and emitted from the display, comprising the steps of:
- determining the magnitude and polarity of the source electric field;
- developing a counter electrical signal of equal magnitude and opposite polarity to the magnitude and polarity of the source field;
- establishing a counter electric field of equal magnitude and opposite polarity to the magnitude and polarity of the source field using said counter electrical signal;
- and,
- coupling said counterfield with the source field in a manner such that the magnitude of the source field is substantially diminished by said counterfield, thereby reducing the magnitude of electric field emitted from the display.
Dependencies are inferred from the claim text.