| 摘要 |
A controlled video mixer is employed in a special effects generator of a flight simulator visual display system to produce realistic reduced visibility scenes. The video mixer produces a composite video signal from a camera video signal and a cloud function signal. The video mixer includes a gated variable transconductance device which has a differential input and operates in a range where its gain is an exponential function of its gate voltage. A control signal which is directly proportional to slant range and inversely proportional to visibility range is provided to the gate of the variable transconductance device. The output of this device is summed with the cloud function signal to produce a composite video signal which, when displayed on a TV receiver, accurately depicts atmospheric visibility effects.
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