| 摘要 |
PURPOSE:To detect air bubbles and foreign objects in an optical fiber preform accurately and without any omission by applying light to the entire surface of the end of a rod-shaped optical fiber preform and picking up the image of the side surface with a video camera and then performing image processing. CONSTITUTION:One edge of an optical fiber preform 1 is mounted to a rotary holder 31a and an end face 1a is exposed to the side of a light source 2 and then the other is mounted to a rotary holder 31b. A motor 21 is driven, the preform 1 is rotated, light is applied uniformly on the end face 1a, and then the image of the scattering light by air bubbles and foreign objects is picked up from the side surface with a video camera 7 which can be slid along a frame 33. The camera 7 stores 10 the picked-up image signal, analyzes the image 11, displays it 12, and then prints it out 13. The image processing circuit 11 differentiates the intensity change in the direction of axis line of the preform 1 for obtaining a change rate (magnification of image signal intensity), compares the obtained change rate with a set reference value, automatically detects air bubbles and foreign objects, and then outputs the coordinates to the display 12 and the printer 13.
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