Automatic focusing method in high-noise environment and digital imaging device using the same

Abstract

An automatic focusing method in a high-noise environment and a digital imaging device using the same are used for determining an object distance. The method includes taking two digital images at a farthest object distance and taking two digital images at a nearest object distance, under a first exposure condition and a second exposure condition; capturing digital images under the first exposure condition at a plurality of different object distances other than the farthest and nearest object distances; selecting at least two images captured at adjacent object distances to create a composite image; calculating an object distance of the composite image; calculating high-frequency signals of the second farthest object distance image, the second nearest object distance image, and the composite image in the focusing frame; determining from the images an object distance corresponding to the maximum high-frequency signal; and moving an automatic focusing lens to the object distance.