Dynamic focus voltage for a focus mask

Abstract

A dynamic focus voltage generator is provided for a tensioned focus mask of a cathode ray tube of video display. The tensioned focus mask includes spaced apart strands and spaced apart crosswires separated from the strands. A synchronizing signal at a horizontal deflection frequency is used for generating a dynamic focus voltage component that varies in accordance with a position of an electron beam on a screen of the cathode ray tube. A synchronizing signal at a vertical deflection frequency is used for generating a dynamic focus voltage component that varies in accordance with the position of the electron beam on the screen of the cathode ray tube. The time varying voltage components are combined with a direct current voltage component for producing a dynamic focus voltage between the strands and crosswires.

Dependencies are inferred from the claim text.