| 摘要 |
PURPOSE:To attain the optimum focus tracking characteristic at all times by connecting a variable impedance element in series with a variable resistor for focus voltage adjustment, and adjusting the focus voltage. CONSTITUTION:When a negative luminance signal is applied to a transistor (TR) 16 being a variable impedance element, the base current of the TR16 is increased at white signal and the impedance between the collector and emitter of the TR16 is reduced. Thus, the collector voltage of the TR16 is lowered and the focus voltage is reduced at the same time. The impedance between the collector and emitter of the TR16 is increased at a dark signal and the collector voltage of the TR16 is increased, then the focus voltage is also increased. |
