A method and apparatus is disclosed for contact-free interval or thickness measurement. A sharply concentrated light beam is periodically deflected over a measuring space having a measuring plane and reference plane situated therein. A beam divider is positioned after the beam deflector and deflects the beam towards first, second and third light detectors. A fourth light detector is also provided to receive reflected light from the measuring plane and reference plane. A first time difference is utilized to control deflection frequency of the light beam; a second time difference controls deflection amplitude of the light beam; a third time difference determines a spacing of the measuring plane from the reference plane; and a fourth time difference corrects for changes in a direction of the light beam such as when a new light source is positioned in the system or when other directional errors occur.