Lens position adjusting method for zoom lens

Abstract

A lens position adjusting method for a zoom lens includes at least two movable lens groups, one lens group being primarily utilized for focusing and the other lens group being primarily utilized for magnification, wherein an object at a predetermined distance is in-focus when each movable lens group is positioned at each of respective initialized positions thereof with the zoom lens being set at a first focal length, and wherein each movable lens group is moved to vary magnification in accordance with a moving amount from the initialized positions of the movable lens groups. The lens position adjusting method includes: arranging a testing object at a position corresponding to a predetermined distance from the zoom lens; arranging a focal point detecting device at a reference focal plane or in the vicinity of the reference focal plane of the zoom lens; moving each movable lens group to each position at the first focal length; moving each movable lens group along an optical axis of the zoom lens so that a lens moving amount of each movable lens group is detected when a sharp image of the testing object is formed on the focal point detecting device via the zoom lens; making each of the positions of the movable lens groups as provisional initialized positions after completion of movement by the lens moving amount from the initialized positions; moving each movable lens group from the provisional initialized positions to positions at a predetermined focal length; detecting the lens moving amount by moving the movable lens group being chiefly utilized for focusing; obtaining a defocus amount from the lens moving amount; and obtaining an adjusting amount according to the defocus amount detected at given plurality of focal lengths so that each position of the movable lens group at which the in-focus state with the testing object is obtained at the first focal length serves as each adjusted initialized position.