Device for contact-free thickness measurement

Abstract

A device is disclosed for the contact free thickness measurement of an object. A light source produces a sharply bundled light ray which is divided into two light rays and simultaneously and periodically deflected so as to scan over opposite surfaces of the object. A reference detector determines a time t.sub.O at which two rays corresponding to a zero position of the light deflector strike the object. A first detector picks up light only along a first sighting line which intersects the object at a first point on one surface thereof. This first detector detects a time t.sub.A when one of the two light rays scans across the first point. A second detector picks up light only along a second sighting line which intersects the object at a second point on the one surface thereof. The second detector detects a time t.sub.B when the one light ray scans across the second point. A third detector is provided for picking up light only along a third sighting line which intersects the object at a third point on the opposite surface thereof. The third detector detects a third time t.sub.C when the other light ray scans across the third point. A measuring device is provided for computing distances of the first, second, and third points from a reference plane and for computing a thickness of the object therefrom.