| 摘要 |
PURPOSE:When an image guide is made from its preform, unhomogeneous residual strain is formed to produce an image guide of with large length with high resolution. CONSTITUTION:An image guide preform which is prepared by inserting a number of image element lines 1 which are made of a core material with equal linear expansion coefficient into a large quartz tube 2 is drawn into a non- circular quartz tube 5 including image element lines with a non-circular cross section which has a straight-line part 7. The inner residual stress of the resultant image guide becomes unhomogeneous in the respect of the cross section. Thus, the mode propagation rate delicately differs in individual image element lines 4 to inhibit mode coupling. Thus, the stray light propagating between the lines is reduced to improve the contrast. Further, the quartz tube 2 may be made elliptic.
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