Optical quantification of yarn hairiness using a single direction

Abstract

This paper presents a system which is able to measure yarn hairiness using coherent optical signal processing, plus the associated electronics and custom software. By placing a spatial high-pass optical filter in the Fourier plane, to remove the low spatial frequency information (yarn core and light that does not hit the yarn). High spatial frequencies, which correspond to hairiness and the yarn borders, are transmitted. To quantify hairiness, a photodiode, plus a trans-impedance amplifier were used to obtain a voltage proportional to the hairiness signal. A data acquisition system controlled by an application developed in LabVIEW is used to acquire and process the measured data. However, an open question remains as to whether one can obtain a valid characterization of the yarn properties using a single projection direction. The results reported here demonstrate that in the case that the hairiness is randomly orientated a single projection measures on average 0.64 of the hairiness present on the yarn.