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 o n 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 de- pends on the grey levels of the transition.