Multi-point autofocus system

DETAILED DESCRIPTION The present invention has been made in view of the aforementioned problems that reside in conventional multi-point autofocus system, and an object of the present invention is to provide a multi-point autofocus system which has an improvement in manual focus-zone selection mode.
To achieve the object mentioned above, according to an aspect of the present invention, a multi-point autofocus system is provided, including a focus detection device which can calculate a defocus amount for each of a plurality of focus detection zones in a picture plane; a selecting device for manually selecting a focus detection zone from the plurality of focus detection zones for which the defocus amount is to be calculated by the focus detection device; and a determining device for determining a valid focus detection zone by which a valid defocus amount can be calculated out of at least one of the plurality of focus detection zones other than the manually-selected focus detection zone, in such a manner that a higher priority is given to a focus detection zone than another focus detection zone of the plurality of focus detection zones in the case where the result of a calculation of the defocus amount of the manually-selected focus detection zone is invalid.
In an embodiment, the determining device assigns priorities to at least one of the plurality of focus detection zones other than the manually-selected focus detection zone in accordance with an algorithm which gives the higher priority to a focus detection zone which is closer to the manually-selected focus detection zone.
In an embodiment, the determining device assigns priorities to at least one of the plurality of focus detection zones other than the manually-selected focus detection zone in accordance with an algorithm which gives the higher priority to a focus detection zone which is closer to a center of the picture plane.
In an embodiment, the determining device assigns priorities to at least one of the plurality of focus detection zones other than the manually-selected focus detection zone in accordance with an algorithm which gives the higher priority to a focus detection zone which is adjacent to the manually-selected focus detection zone