| 摘要 |
PURPOSE:To enable the stable production of a long-sized image guide having no disturbance in picture elements without generation of foam by contg. plural optical fibers in a glass tube, evacuating the inside of the tube, and sealing hermetically the tube then heating and elongating the glass tube. CONSTITUTION:A prescribed number of optical fibers 2 each having a core and a clad are densely arranged in a glass tube 1 which is sealed at one end. The inside of the tube is evacuated to a high vacuum with an evacuation device 5. The tube is subjected repeatedly to evacuation and feeding of gaseous He several times depending upon cases. While the high vacuum in the He atmosphere is maintained in the tube, the other end 7 thereof is melted and sealed by heating. A capsular preform which is evacuated 4 in the above-mentioned way is sealed by heating, and an image guide having a prescribed size is obtd. The long-sized image guide which can transmit an image satisfactorily without the disturbance in picture elements owing to the foaming during spinning with heating is thus produced stably. |
