Abstract: An optical system focuses a laser beam emanating from a laser onto a surface of an object, such as a circumferential surface of the object to be measured. The light beam is reflected from the object, so as to form a generally focused light spot; the intensity of the light spot, which depends on the distance of the surface from the optical system, is measured, and the measurement results are displayed and/or utilized for controlling the dimensions of the object, if the object is an elongated article, and is continuously produced, generally in a direction transverse to its cross-section.