Device and method to determine the duration of a test radiation

摘要

The device (100) has a light transmitter (10) and a receiver (50) forming a resonant circuit (90) whose oscillation frequency depends on running time of test radiation (35) i.e. light, to an object (41) i.e. optical fiber. A control and evaluation circuit (80) produces oscillation of the circuit and stops transmission of the radiation if the receiver receives the radiation. The transmitter transmits the radiation in a monitoring region (40) if the receiver does not receive the radiation. The control and evaluation circuit determines the frequency of the resonant circuit to determine the time. An independent claim is also included for a method for determining running time of test radiation to an object in a monitoring region.