DYNAMIC FOCUS VOLTAGE AMPLITUDE CONTROLLER

摘要

A RESISTIVE VOLTAGE DIVIDER IS RESPONSIVE TO A PARABOLIC VOLTAGE DEVELOPED IN AN S-SHAPING CAPACITOR OF A DEFLECTION CIRCUIT OPERATING AT A SELECTED DEFLECTION FREQUENCY. THE VOLTAGE DIVIDER INCLUDES A CONTROLLABLE RESISTIVE NETWORK FOR AUTOMATICALLY SELECTING AN ATTENUATION FACTOR OF THE VOLTAGE DIVIDER IN ACCORDANCE WITH THE SELECTED DEFLECTION FREQUENCY. AN AMPLIFIER RESPONSIVE TO THE ATTENUATED PARABOLIC VOLTAGE GENERATES AT AN OUTPUT TERMINAL OF THE AMPLIFIER A PERIODIC OUTPUT VOLTAGE THAT IS CAPACITIVELY COUPLED TO A FOCUS ELECTRODE TO PRODUCE A DYNAMIC FOCUS VOLTAGE. IN A FIRST EMBODIMENT, THE CONTROLLABLE RESISTIVE NETWORK INCLUDES A PHOTO-RESISTOR THAT PROVIDES AUTOMATIC GAIN CONTROL. IN AN ALTERNATIVE, SECOND EMBODIMENT, THE VOLTAGE DIVIDER IS SWITCHED.(FIG. 1B)