| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical path length control device capable of preventing degradation of light condensing efficiency even if an angle error and a displacement error are caused by movement of an optical system.SOLUTION: An optical path length control device includes a plane mirror 8 that reflects parallel light folded back by a folding optical system 5 and returns the parallel light to the folding optical system 5. The optical path length control device is configured such that the folding optical system 5 folds back the parallel light returned by the plane mirror 8 and a condensing optical system 4 condenses the parallel light folded back by the folding optical system 5 on an optical fiber 3. |
