H - Electricity – 04 – N
Patent
H - Electricity
04
N
350/40
H04N 5/38 (2006.01) H04N 5/232 (2006.01)
Patent
CA 1289236
ABSTRACT In an automatic focusing apparatus of a video camera, a first focus evaluating value which steeply changes and a second focus evaluating value which gently changes relative to the position of a lens, are detected in response to a video signal obtained in an image sensing circuit. A switching circuit alternately selects the first and second focus evaluating values every one field to apply the same to in-focus state detecting circuits respectively. The in-focus state detecting circuits together with a focusing motor control circuit, perform an automatic focusing operation by hill-climbing control. In addition, a calculating circuit calculates the relative ratio of the first focus evaluating value to the second focus evaluating value. The focusing motor control circuit sets the rotational speed of a focusing motor to a normal speed when the calculated relative ratio is smaller than a predetermined value while setting the rotational speed of the focusing motor to a low speed when it is larger than the predetermined value. Therefore, a lens is moved at low speed when the focusing lens is in the vicinity of the in- focus position while being moved at high speed when it is in the defocused state.
570629
Haruki Toshinobu
Hidaka Masaru
Kikuchi Kenichi
Murashima Hirotsugu
Takuma Masao
G. Ronald Bell & Associates
Sanyo Electric Co. Ltd.
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