Measuring the Angle of Twist of a Fiber on the Basis of its Computer Image

Abstract

A method is proposed for determining the angle of twist of a fiber from the distribution of the intensity of the pixels of a computer image of the fiber’s diffraction pattern. The two-dimensional fast Fourier transform is used to calculate the distribution based on the computer image. The value of the angle of twist is determined from an intensity distribution diagram constructed in polar coordinates. A computer program has been written in the language C++ (with use of the platform Net 3.5) to realize the new method. It is known that diffraction-based laser methods make it possible to use the mutual position of maxima on a diffraction pattern to perform a continuous quantitative check of the main parameters of textiles that are related to the periodic repetition of their geometric structure. These parameters are independent of the color and the material of textile. The same purpose can be served through the use of calculated diffraction patterns instead of patterns obtained on a screen by directly illuminating a specimen by a laser beam [2]. Such patterns can be calculated from an original computer image of the specimen with the use of the Frenkel– Kirchhoff integral [3] corrected with allowance for the possible dependence of the amplitude of the illumination u(ζ, η) on the coordinates of the points of the image that are being examined [1]: