An auto-focus sharpness function for stereo image pairs

Auto-focusing is a key feature of modern camera systems that ensures a focused image is captured without the need for any user intervention. Passive auto-focusing is achieved based on a measure of sharpness or a sharpness function that is extracted from a series of images at different focal positions. With the rapid growth of stereo camera systems for 3D applications, this paper introduces a sharpness function when a series of stereo image pairs are captured at different focal positions. This function is defined based on the joint information between the left and right images. A comparison is carried out between the introduced sharpness function and the conventional sharpness functions when considering the left and right images separately in terms of sharpness accuracy and computation time.