Zoom lens

Abstract

A zoom lens having both manual mode and auto focus mode of focus adjustment. The zoom lens includes, in order from the object side, a focus portion, a zoom portion, and a main portion. Zooming is accomplished by moving some or all of the lens elements in the zoom portion along the optical axis. What would otherwise be a fluctuation of the image surface with change of object distance is corrected in manual mode by manually moving some or all of the lens elements of the focus portion along the optical axis based on visual observation of the object through the zoom lens as the adjustment is made. In auto focus mode, what would otherwise be a fluctuation of the image surface with change of object distance is corrected by micro-vibrating some or all of the lens elements of a lens group in the light path following the focus portion. A signal that varies according to image quality variations caused by this micro-vibration is detected and the detected signal is used to automatically control the position of those lens elements in the focus portion that are manually moved in order to adjust focus in manual mode. At least one surface a lens element that is micro-vibrated in auto focus mode is aspherical, and at least one surface of a lens element that is micro-vibrated in auto focus mode includes a diffractive optical element having diffraction zones formed thereon.

Dependencies are inferred from the claim text.