| 摘要 |
The rangefinder comprises a light transmitter 19, 21, a light receiver 12, 17 and a computing device 27. The transmitter sends light pulses 22 towards the clouds 23. The receiver receives not only scattered sunlight but also the light reflected 24 by the clouds and by atmospheric disturbance encountered by the light pulses, and delivers a garbled echo signal 31, 32; 31', 32'. The computing device analyses the echo signal and provides information about the height of the clouds. The optical axes of the light transmitter 19, 21 and the light receiver 12, 17 coincide. This arrangement means that the parasitic echo always has a negative gradient in the intensity-time spectrum of the echo signals, whereas the cloud echo appears with a positive gradient. The computing device gives the height of the cloud as the height for which the first significant increase occurs in the gradient of the echo signal. <IMAGE>
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