Surface profile measuring device utilizing optical heterodyne interference

摘要

The surface profile measuring device utilizing optical heterodyne interference comprising a laser source for emitting a laser beam, an object lens for converging the laser beam on the surface of an object to be measured, the laser beam being reflected from the surface of the object while provided with information on a surface profile of the object, an optical heterodyne interference device for allowing the reflected beam to interfere with a reference beam having a frequency different from that of the reflected beam to generate beat signals having the information on the surface profile of the object, a circuit for measuring the surface profile of the object on the basis of phase variation of the beat signals, a driving device including a piezoelectric element for relatively moving one of the object lens and the object to be measured in the direction of the optical axis of the laser beam incident on the surface, and a control device for controlling the driving device on the basis of the phase difference or amplitude ratio between the beat signals so that the surface of the object is disposed substantially at a focusing position of the object lens.