METHOD AND ARRANGEMENT FOR DETERMINING THE SPEED AND/OR LENGTH OF A RUNNING THREAD

摘要

The invention relates to a method for determining in a contactless manner the speed and/or length of a running thread (4) by means of an optical sensor device which is arranged in the run of the thread of a textile machine and which comprises at least one optical detector (6b). Said method comprises the following steps: passing the thread (4) through a measurement volume (5), generating a laser beam (2) by means of a laser source (1), collimating the laser beam (2) by means of an optical device (7), splitting the laser beam (2) into at least two partial beams (2a, 2b) by means of an optical splitting and guiding device (3) to split and guide the laser beam (2), guiding the two partial beams in such a manner that a partial beam is guided as a measurement beam (2a) onto the thread (4) in the measurement volume (5) and a shadow is cast thereon by the thread and the other partial beam is guided as a reference beam (2b) past the thread (4) and onto an optical detector (6b), superimposing the light of the measurement beam (2a) that is influenced and/or reflected by the thread (4) with the light of the reference beam (2b), electronically evaluating the measurement signals produced by the optical detector (6b) according to the laser Doppler anemometry method to determine the speed and/or the length of the running thread (4). The invention further relates to an arrangement for carrying out said method.