| 摘要 |
An automatic focusing system adjusts the focus of video camera automatically using the contrast of the Y signal, which is one image input signal. The maximum and minimum values of the Y signal determine the contrast of the Y signal. This contrast value is then compared with the previous contrast value to determine if the focus driving motor should be signalled to rotate in the same direction as previously, a different direction or to stop rotation. Gating means with stored ranges are used to establish the successive detection of the Y signals to allow continuous operation of the auto focus circuit. Thus, the system can always automatically focus without being affected by the peripheral background of object.
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