LENS POSITION CONTROLLER FOR ZOOM LENS

摘要

PURPOSE:To obtain high focusing accuracy even while reducing a storage capacity by calculating the quantity of the movement of a focusing lens group based on the arithmetic operation of the reciprocal of the information on an object distance and the intrinsic coefft. corresponding to a focal length. CONSTITUTION:The distance S up to the object is calculated by a distance calculating means 5 by the output of the light position signal from a distance measuring means 4. The calculated distance S up to the object is sent by an extension length calculating means 6. The extension length eta of the focusing lens group 3 is calculated by the information on the distance S up to the object and the zoom position Zi from the zoom position output means 7 of a variable power lens group 2. The information on the calculated extension length eta is sent to a system controller 8 which drives a focusing motor 9 so as to move the focusing lens group 3 by as much as the extension length. The extension length eta of the focusing lens group 3 is approximated by a quadratic equation with the reciprocal 1/S of the distance up to the object as a function.