Automatic focusing apparatus and automatic focusing method for automatically matching focus in response to video signal

Claim 1

An automatic focusing apparatus for automatically matching a focus relative to an object in response to a video signal obtained from image sensing means including a focusing lens (1) and an image sensing device, comprising: relative position altering means (2, 3) for altering a relative position of said focusing lens with respect to said image sensing device along an optical axis; area setting means for setting by time-division of said video signal a first area located in a midmost area of an image-sensed picture, a second area including said first area and having a larger areal size than that of said first area, and a third area including said second area and having a larger areal size than that of said second area; in-focus target area selecting means for selecting any of said first, second and third areas as an in-focus target area to be a target of a focusing operation; means for manually setting said first area as the in-focus target area; first focus evaluating value detecting means for detecting a high frequency level in a video signal in the in-focus target area selected by said in-focus target area selecting means for each constant time period, to supply the detected high frequency level as a focus evaluating value taking a peak value at an in-focus position; control means (6, 7, 8, 9, 10, 13, 14) responsive to said focus evaluating value for controlling said relative position altering means so as to shift the relative position of said focusing lens to a position where said focus evaluating value becomes a peak value; second focus evaluating value detecting means for detecting a focus evaluating value in said second area, to supply the detected focus evaluating value when said third area is selected as the in-focus target area; means (10) for controlling said in-focus target area selecting means so as to select said third area as the in-focus target area when the focusing operation starts, and to switch the in-focus target area from said third area to said second area when said focus evaluating value supplied from said second focus evaluating value detecting means becomes equal to or higher than a predetermined value; and means for controlling said in-focus target area selecting means so as to select with priority said first area as the in-focus target area when said first area is manually set as the in-focus target area.