FOCUSING SYSTEM USING LIGHT SOURCE AND IMAGE SENSOR

摘要

A process comprises projecting a radiation beam (213) from a movable optical element (202) onto an image sensor positioned along an optical axis (210) of the movable optical element (202) and substantially normal thereto. The movable optical element (202) is movable relative to the image sensor (222) and the radiation beam is projected at a selected angle relative to the optical axis. A plurality of targets are positioned at known front focus distances from the movable optical element, and for each front focus distance, a back focal length of the movable optical element and the position where the beam of radiation falls on the image sensor are recorded.