MEASURING DEVICE

摘要

A measuring device for measuring the difference in required time between lights that can cover a wide dynamic range or a distance up to an object of measurement without adjusting a light quantity. A pulse light emitted from a light emitting unit (1) is branched into a reference light to a reference light path F1 and a measurement light to a measuring light path F2 that is applied to an object of measurement and reflected back, and these lights are received by a light receiving unit (9). A multiple reflection optical fiber Mp1 inserted in the middle of the measuring light path F2 turns the measurement light into a multiple pulse train that attenuates in light quantity at a constant rate sequentially. A measurement light almost the same in light reception level as the reference light can be selected from this pulse train. The difference between time required for measurement light to pass through the measuring light path F2 and time required for the reference light to pass through the reference light path F1, or a distance up to an object of measurement is measured based on this selected measurement light and the reference light.