| 摘要 |
PURPOSE:To accurately measure the distance to an object to be detected by providing an automatic frequency control system and adopting a coherent detecting system for keeping the difference between the frequency of transmitted pulses and a local oscillation frequency always constant. CONSTITUTION:A pulse laser beam LB1 with a frequency fp is emitted from a light transmitting optical system 5 to a space to be monitored. The reflected pulse laser beam LB1' from an object O is received by a light receiving optical system 6. The received laser beam LB1' and a CW laser beam LB2 with a local oscillation frequency fc are optically synthesized in a mixer 7. A pulse radar instrument is controlled by an automatic frequency control system composed of a CW laser oscillator 13, a distributor 14, a mixer 15, a light receiver 16, a band-pass filter amplifier 17, a frequency discriminator 18, a peak hold circuit 19 and an analog arithmetic unit 20 so that the frequency of the optically synthesized laser beam becomes equal to a reference frequency.
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