Apparatus and methods for measuring the diameter of a moving elongated material

摘要

The present invention relates to an apparatus and methods for measuring the diameter variation of an elongated cylindrically shaped object. In particular, the instant invention relates to measuring the diameter variation of a moving strand comprised of multiple textile filaments. Using lasers and charged coupled devices (hereinafter referred to as "CCD's") for sensing the diffraction and interference patterns produced when electromagnetic radiation emitted from at least one laser is partially obscured by the edges of the strand. Several methods for extracting the information contained in the diffraction pattern may be employed. One method is based upon a comparison between the measured diffraction pattern and a theoretical pattern produced by a knife edge as calculated using the Kirchhoff-Fresnel integral. Others rely upon comparing the measured diffraction pattern with patterns previously produced by cylindrical objects of known diameter and stored in a computer library. The remaining methods are empirically based and may be implemented by algorithms which should be available on any small personal computer capable of performing a statistical analysis of data stored in an array or vector form. A feedback system for controlling the temperature of a fiber glass bushing assembly based on changing diameter measurements collected by the aforesaid apparatus is also disclosed.