US Patent 7956897 Image combining device and imaging apparatus

A plurality of divided exposure images (first to fourth images) are obtained by dividing a normal exposure time. By an image matching method, a motion detection circuit calculates a plurality of cumulative total correlation values between different divided exposure images, and searches the plurality of cumulative total correlation values for the smallest cumulative total correlation value, thereby calculating a motion vector between the different divided exposure images. In addition, based on the level of the smallest cumulative total correlation value, the level of reliability B[i] indicating the accuracy of the motion vector is calculated. An image combining circuit uses the level of reliability B[i] as a mixture proportion. The image combining circuit positions the divided exposure images based on the motion vector, and combines the divided exposure images together one on top of another in mixture proportions (B[i]), so as to form one still image that suffers less from camera shake.