Dynamic focus for a cathode ray tube

摘要

Dynamic focus voltages for a CRT are obtained by utilizing the combined parabolic conversion wave shapes for control of the focusing electrode to provide sharp focus at all points in the raster. A current source is coupled to the focus divider chain and the conversion wave shape controls the current in the divider chain by controlling the resistance in a transistor. No high voltage capacitors are required since the dynamic voltages are coupled into the chain near the low voltage end.