| 摘要 |
PROBLEM TO BE SOLVED: To prevent occurrence of a measurement error caused by the phenomenon that a reflected light returns up to a light emitting element, is reflected by the surface of the light emitting element, and transmitted back to a target point again at a mispointed time, in a light wave range finder which finds a distance from the phase difference between an emitted light and a reflected light. SOLUTION: In a light wave range finder, an emitted light emitted from a light emitting element 10 is led up to a dichroic prism 3 by an optical fiber 20, and along with it an optical isolator 30 is inserted into the middle of this optical fiber 20. When a reflected light of this emitted light proceeds reversely in the optical path of the emitted light, the optical isolator 30 prevents the reflected light from returning up to the light emitting element 10.
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