发明授权
US4841370A Automatic focusing circuit for automatically matching focus in response to video signal 失效
自动对焦电路,用于自动对焦视频信号

Automatic focusing circuit for automatically matching focus in response
to video signal
摘要:
In an automatic focusing circuit of a video camera, automatic focusing operation is performed by a focus evaluating value formed in response to a video signal obtained by an image sensing circuit (4). A first focusing motor control circuit (15) controls the rotation of a focusing motor (3) so that a focusing lens (1) is once fixed in the position where the focus evaluating value takes the maximum value. A second focusing motor control circuit (17) changes the focusing motor (3), by a predetermined very small amount, to determine the slope of the focus evaluating value, which change is repeated until inversion of the slope, that is, the maximal point is detected. As a result, the position of the focusing lens is corrected at the maximal point of the focus evaluating value. When the correction amount exceeds a predetermined value, first automatic focusing operation by the first focusing motor control circuit (15) is resumed.
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