US Patent 9214011 Camera defocus direction estimation

Apparatus and methods for estimating defocus direction from a single image obtained, such as in a digital camera apparatus, are presented. To determine defocus direction, point spread function (PSF) differences for the image are evaluated in the frequency domain, with frequency pairs being found having largest difference in their Fourier transform magnitudes, from which a direction estimate feature is extracted, and defocus direction estimated based on relation of estimated feature and statistics derived from camera image tests. The method can be applied for controlling autofocus mechanisms in cameras, or other applications requiring rapid determination of defocus directions, such as from a single image.