Apparatus and method for measuring displacement, method of making die for molding optical element, and optical element

摘要

A beam splitter splits a laser beam emitted from a laser light source into a first laser beam that travels toward an object and a second laser beam. The second laser beam is received by a second photodetector. The second photodetector is positioned such that the light quantity of the second laser beam incident on the second photodetector is equal to that of the first laser beam incident on a first photodetector. A position calculator calculates displacement of the object relative to the laser light source on the basis of the difference between an output of the first photodetector and an output of the second photodetector.