METHOD AND APPARATUS FOR IMPROVING VERTICAL SHARPNESS OF PICTURE TUBES

摘要

Large format TV tubes must produce a high peak brightness in order to be acceptable to the user. This results in a large beam current in bright areas of the picture and in a subsequent defocussing of the resulting spot on the display and in a loss of the sharpness of vertical and horizontal transitions. The apparent sharpness of a vertical transition is gained by modifying the deflection of the TV receiver such that, at vertical transitions, the line on the bright side of the transition is deflected away from the transition region. Advantageously the amount of vertical scan modulation corresponds to a multi-level control signal and depends on the grey levels of the transition.