METHOD OF DETERMINING ANGLE OF THREAD TWIST Russian patent published in 2014 - IPC G01N21/898 G01B11/26 

FIELD: textiles, paper.

SUBSTANCE: in the method the analysis of the angular diagram of the light flow distribution in the diffraction pattern observed from the test material with illumination of the thread surface by parallel beam of monochromatic coherent light with a circular cross section, and the magnitude of the desired angle of twist is determined according to the angle measured between the direction to the maximum in the angular diagram of the light flux in the diffraction pattern, and the perpendicular to the thread, made in the plane of the pattern from its centre. And the computer microimage of the thread under study is examined, the diffraction pattern from which for this lighting is calculated using the fast two-dimensional Fourier transformation, and the angular diagram of the light flux distribution in the diffraction pattern is determined according to the diagram of the angular distribution of the average total intensity of illumination of pixels I_ΔS(φ), which is calculated in the ring, set by the radii R₁ and R₂ relative to the centre of the diffraction pattern in the polar coordinate system for each value of the angle φ in the range of values of 0-2π; by the formula $$I_{\Delta S}(\varphi )=\frac{{\displaystyle \sum _{n=1}^N{i}_{p_n}}}{N},$$ where ΔS is the square of the ring sector limited by the angle Δφ; the numerator is the sum of the intensities of image pixels i_p held in the selected sector ΔS; N is the number of pixels in ΔS.

EFFECT: improvement of measurement accuracy by reducing the measurement error, while simultaneous simplifying the measurement process.

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