PURPOSE: To provide the subject detector designed to automatically detect, on-line during optical fiber drawing process, the bubbles developed in the coating layer of an optical fiber made by coating a fiber core with the coating layer or those developed at e.g. the interface between the core and the coating layer.
CONSTITUTION: An optical fiber 1 is irradiated, from a laser beam generator 5, with laser beams L1 of a specified width extending from the direction nearly rectangular to the long direction of the optical fiber along the plane in the direction rectangular to the optical fiber, and the transmitted beams L2 resulted by transmitting the laser beams L1 through the optical fiber 1 are projected on a bubble-detecting screen 8. A slit 9 is then opened so as to pass the transmitted beams L2 transmitted when there are no bubbles 4 on the screen 8, and of the transmitted beams L2, only the scattered beams scattered due to bubbles 4 are projected on the screen 8 and the resultant image P is taken by a CCD camera 11 and then subjected to image processing, thus accomplishing the objective detection of the bubbles 4.
TAKEDA TETSUYA
TSUJI KOJI
NAGAE NOBUSADA
YAMAGUCHI SHUNICHIRO
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