| 摘要 |
A camera focusing system and a method thereof are provided. The focus of the camera is moved to three equidistant reference positions X<SUB>i</SUB>, X<SUB>j </SUB>and X<SUB>k </SUB>to get three image contrasts Y<SUB>i</SUB>, Y<SUB>j </SUB>and Y<SUB>k </SUB>respectively. Then, quadratic equation Y=aX<SUP>2</SUP>+bX+c is solved with (X<SUB>i</SUB>, Y<SUB>i</SUB>), (X<SUB>j</SUB>, Y<SUB>j</SUB>), and (X<SUB>k</SUB>, Y<SUB>k</SUB>) to obtain the coefficients a, b and c. Accordingly equation X<SUB>m</SUB>=(-b)/(2a)=X<SUB>j</SUB>+s(Y<SUB>k</SUB>-Y<SUB>i</SUB>)/2(2Y<SUB>j</SUB>-Y<SUB>k</SUB>-Y<SUB>i</SUB>) is solved to get the optimal target focusing position X<SUB>m</SUB>. According to the present invention, the optimal focusing position can be obtained instantly and the exposure time can be reduced by utilizing least reference points and simple procedure.
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