| 摘要 |
<p>PROBLEM TO BE SOLVED: To measure a condition of visibility obstructed between two distant points by stable, safe and highly accurate methods. SOLUTION: On the transmitting side, the output of a highly stable standard oscillator 11 is divided by a divider 12, and the resultant output is input to an optical transmitter 13 having a driving circuit 131 and a light source 132, then a measuring light 3 modulated by the output of the divider 12 is emitted. On the receiving side, a received light is converted into an electric signal by a light receiver 24 and input to a synchronous detector 25. The output of a highly stable standard oscillator 28 is divided by a divider 27, and the resultant output is input to the synchronous detector 25 as a reference signal, then a signal which corresponds to the reference signal in frequency and phase of the electric signal is output and the signal is recorded in a recording unit 26. Even if the transmitting side and the receiving side independently operate, and an independent synchronous operation is achieved without injuring synchronism within a time during which stability of the oscillator is relied on.</p> |
