Method of automatically focusing using a quadratic function...

Details Method of automatically focusing using a quadratic function... Method of automatically focusing using a quadratic function...

2007-09-11

2007-09-11

Vu, Ngoc-Yen (Department: 2622)

Television

Camera, system and detail

Optics

C348S351000

Reexamination Certificate

active

10682681

ABSTRACT:
A method of automatically focusing a camera determines a position of a focus lens where an amount of a high frequency in an image signal is a maximum. The amount of a high frequency included in an image signal is measured at intervals of multiple focus motor steps. Three of the measured positions (x1, x2, x3) and their corresponding measured high frequency amounts (y1, y2, y3) are identified, where y2is the largest of the measured high frequency amounts, and x1and x3are the nearest measured positions on either side of x2. A quadratic function f(x) is determined for the high frequency amount with respect to the focus lens position x. A position at which a derivativeⅆf⁡(x)ⅆxof the quadratic function f(x) is zero, is determined to be the position corresponding to maximum high frequency amount. Thus, the driving time of the focus motor can be reduced.

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