Focus detection device for an optical system

摘要

A focus detection device for an optical system which samples discrete areas of an image to determine focus adjustment. The discrete areas are either rectilinear or cross shaped. The rectilinear focus detection areas are inclined relative to the horizontal edge of the finder frame at an angle less than 30 DEG and preferably less than 20 DEG , thus reducing the width of the vertical direction picture elements in the picture element row. This makes it possible to detect both vertical lines and horizontal lines. The cross shaped areas are arranged at central focus detection positions where conditions permit and rectilinear areas are arranged at positions along the horizontal edge of the finder frame. Using a combination of inclined rectilinear and cross shaped, areas traditionally difficult-to-handle objects can be detected to the extent possible in any area.