| 摘要 |
The system comprises a contrast detecting circuit (20) for detecting the contrast of Y signal transmitted by a video signal processor (3) and for digitizing the contrast signal, a contrast comparator (30) for determining the direction of the motor by comparing the present and one step pre-field contrast signals, and for stopping motor when the difference of the present and one step pre-field contrast signals are smaller than a certain value, a focus motor driver (40), a gating indicator (50) for generating the gating signal for inputting the Y signal by indicating new region sequencially when contrast signal is smaller than the reference signal, and a switching circuit (60) for resetting gating indicator.
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