Foerfarande foer detektering av foeroreningar i smaelt harts

摘要

A method of detecting impurities in a molten resin. The molten resin is passed through a passage having a window through which light can pass. Light is emitted from a light source through the window and the molten resin flowing through the passage. Sensors are used to sense a shade produced when the light from the light source is interrupted by an impurity contained in the molten resin. Finally, the size of the impurity is measured from the width of the shade and the intensity of light of the shade. Also, judgment is made that if optical signals obtained by detecting the light that has passed through the molten resin indicate that there exist bright areas around a dark area, the dark area is distinguished as a shade of an impurity. Further, in order to judge the shape of an impurity with high accuracy and record its image, a plurality of the devices used in the above method or the device used in the above method and a conventional camera may be used in combination.