ELECTRON GUN SYSTEM WITH DYNAMIC FOCUS AND DYNAMIC CONVERGENCE

摘要

ABSTRACT OF THE DISCLOSUREAn electron gun system providing beam convergence isdisclosed for use in a color CRT display system. Means includingcathode means develop three electron beams, two of which are off-axis with respect to a center axis of the gun. A plurality ofelectrodes means provide shaping and focusing, and assisting inthe converging of the beams at the tube screen. Means areprovided for developing and applying to the electrode means apattern of potentials which form field components in the gapstherebetween; at least one of the electrode means receives avarying dynamic focusing voltage for dynamically focusing thebeams as they are deflected across the screen. At least selectedones of the plurality of electrodes means for the off-axis beamsare so structured and arranged as to cause a plurality of thefield components to be asymmetric and effective to converge theoff-axis beams. The strengths of the asymmetric field componentsvary in response to changes in the dynamic focus voltage. Theasymmetric field components according to the invention have suchpolarity and strength, due to the structuring and arranging ofthe electrodes, and the application of the pattern of voltages,that a change in the levels of the dynamic focus voltage causes achange in the strength of each of the asymmetric field in adirection effective to additively deflect a common off-axis beamin a common angular direction so as to create a strong dependencyof the convergence of the off-axis beams on variations in thefocus voltage.