| 摘要 |
A focus detection apparatus includes a lens drive mechanism for moving a focusing lens group, and a controller for detecting a contrast value of the object image and moving the focusing lens group. The controller calculates a difference between maximum and minimum contrast values detected at the different positions of the focusing lens group; compares contrast values at two adjacent lens positions to determine whether the contrast value increases successively and subsequently decreases successively; detects a maximum contrast value, if the contrast value increases successively and subsequently decreases successively; calculates the maximum contrast value via a point of intersection between straight lines of two linear approximation expressions if the difference is equal to or greater than a predetermined value; calculates the maximum contrast value from a quadratic approximation expression, if the difference is smaller than the predetermined value.
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