Auto-focus controlling apparatus, electronic imaging apparatus and digital still camera

摘要

An auto-focus controlling apparatus includes a focus evaluation value generating device generating a focus evaluation value based on image data acquired through the focus lens, a target lens position determining device determining a target lens position, a timing determining device determining a plurality of acquisition lens positions for acquiring the focus evaluation values in a scanning direction from a present lens position of the focus lens toward the target lens position, a scanning device driving the focus lens in the scanning direction, a predicted focus lens position determining device predicting a predicted focus lens position based on the acquired focus evaluation values and a moving device stopping the scanning device to drive the focus lens when the predicted focus lens position is determined and driving the focus lens in the same direction as the scanning direction to move the focus lens to the predicted focus lens position.

主权项

1. An auto-focus controlling apparatus for controlling a focusing operation of a focus lens, comprising:
a focus evaluation value generating device configured to generate a focus evaluation value based on image data of a subject which is acquired through the focus lens to determine a focus lens position of the focus lens to the subject; a target lens position determining device configured to determine a target lens position used in the focusing operation by driving the focus lens; a focus evaluation value acquiring timing determining device configured to determine a plurality of acquisition lens positions in which focus evaluation values are to be acquired in a direction from a present lens position of the focus lens toward the target lens position; a scanning device configured to drive the focus lens in an optical axis direction and in the direction from the present lens position of the focus lens to the target lens position to acquire the focus evaluation value at each of the plurality of acquisition lens positions; a predicted focus lens position determining device configured to predict a predicted focus lens position based on the acquired focus evaluation values to determine the predicted focus lens position; and a moving device configured to stop the scanning device to drive the focus lens when the predicted focus lens position is determined and to drive the focus lens in a direction where the focus lens is driven by the scanning device to move the focus lens to the predicted focus lens position, wherein the predicted focus lens position determining device is configured to form a characteristic curve having a hill shape formed based on the acquired focus evaluation values, calculate slopes of the characteristic curve, and predict the predicted focus lens position based on the slopes when the slopes of the characteristic curve are decreased at least twice in series, and the predicted focus lens position determining device is configured to calculate a decreased ratio based on the slopes of the characteristic curve, correct the predicted focus lens position based on the decreased ratio, and determine the corrected predicted focus lens position as the predicted focus lens position.