METHOD FOR DETERMINING THE POSITION OF AT LEAST ONE EDGE OF AN OBJECT BY EVALUATING FRESNEL DIFFRACTION BORDER PROFILES

摘要

The invention relates to a method for determining the position of at least one edge of an object in particular of a strand comprising steps of: illuminating the object using light from at least one coherent light source diffraction borders being generated on both geometric boundaries of the shadow formed by the object. In one embodiment the intensity profiles are first differentiated according to the location. Each differentiated intensity profile can either be plotted on a quadratic position axis and compared to a periodic reference intensity profile or be directly compared to a reference intensity profile that results from a periodic function. In a second embodiment the intensity profiles are compared to a reference intensity profile that results from a periodic function if this function has a period length with a substantially inversely linear dependency on the location and if the function is integrated over the location.