Extended field electron lenses (EFL)

Materially improved color television picture resolution performance results from the use of a new type of electron lens. Contemporary picture tube electron guns utilize lenses which originated with the inception of the science of electron optics. They exhibit rapid growth in electron beam spot size at high current levels. This has precluded the attainment of full NTS system performance - frequently limiting highlight resolution to less than 100 lines. A new five-element lens is described. The length and potential of its elements are selected in a manner which minimizes lens aberrations. Electron guns employing the new lens structure produce more than twice the highlight resolution of comparable guns using ordinary lenses and offer reduced sensitivity to mechanical construction imperfections.