Abstract: Under some conditions in industry the operator should take an upward ordownward observation position for controlling the machine or other mechanicaldevices.This kind of observation position usually exerts influence upon theaccuracy of depth vision—increasing the threshold in depth judgment.In thisstudy a closed stereo T.V.was used on the screen of which the observingobject could be displayed in three dimensions under any position,so theoperator was able to control the object under a normal observationposition.The result of this experiment demonstrated the benefical effect inusing this kind of T.V.to compensate the disorder in depth vision under theinfluence of upward and downward observation position.

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