AUTOMATIC FOCUSING METHOD USING VARIABLE NOISE LEVEL WITHIN DIGITAL IMAGE PROCESSING APPARATUS

摘要

An auto-focusing method using a variable noise level in a digital image processor is provided to maintain a high focusing accuracy and speed even when the intensity of illumination of a region where an image is captured is low. An auto-focusing method in a digital image processor includes an initialization step and a search step. In the initialization step, a reference noise level is set when the intensity of illumination of a region where an image is captured is greater than a reference value, and a noise level varying with the intensity of illumination is set when the intensity of illumination of the region is lower than the reference value. In the search step, a focus lens is moved in stages within a set area and focus values with respect to positions of the moved focus lens are calculated, and a maximum focus value of the set area is detected from the calculated focus values. When the focus values are calculated, the noise level is subtracted from pixel data greater than the noise level and pixel data of the subtraction result is used.