当入射光束与出射光束平行时，单色同心光学系统空间任一点成几何理想像。

If a monocentric system existed for which an incident collimated beam emerged as exactly collimated, then the system would give geometrically perfect imaging of any point in space.

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考虑到光纤出射光束的发散，在有效反射率中引入了损耗因子，讨论了它的基本工作原理。

Its principle is discussed, taking the divergent optical beam emitted from the fiber into consideration, which causes a loss factor for the effective reflectance.

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该方法借助一个焦距较长的凸透镜与被测凹透镜组成无焦系统，可以使准直管出射光束的张角发生改变；

Firstly, a telescope system is made up with a concave lens and a long-focus convex lens, by which the angle of the parallel beam from the collimator can be change.

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