Defocus

About

Defocus is a term derived from optics that describes an aberration in which an image becomes out of focus. This phenomenon is common to anyone who has operated a camera, videocamera, microscope, telescope, or binoculars. From an optical perspective, defocus occurs when the focus shifts along the optical axis away from the detection surface. The effect of defocus is a reduction in the sharpness and contrast of an image, causing what should be sharp, high-contrast edges to become gradual transitions instead. Fine details within a scene become blurred or may disappear entirely from view. To address this issue, nearly all image-forming optical devices are designed with some form of focus adjustment mechanism to minimize defocus and maximize overall image quality.