| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and device for detecting presence of a light and dark part without influence of thickness of a yarn when detecting for the light and dark part composed of foreign matter included in the yarn. SOLUTION: This method includes a process irradiating light on a part of the continuously traveling yarn to form yarn reflected light reflected from a surface of the yarn and scattered reflected light reflected from a reflecting wall composing a background of the yarn, a process receiving a beam B1 where scattered reflected light Φ1(0) and yarn reflected light Φy1 satisfy Φ1(0)<Φy1 by a first sensor S1 and outputting a first signal, and a process receiving a beam B2 where scattered reflected light Φ2(0) and yarn reflected light Φy2 satisfy Φ2(0)>Φy2 by a second sensor S2 and outputting a second signal. The first and second signals are evaluated by comparison and when a relationship between changes of values of both signals is anti-phase, it is determined there is no light and dark part, and when the relationship between the changes of the values of both signals is in-phase, it is determined there is a light and dark part. |
