Control apparatus for positional control of an optical system

A control apparatus for providing positional control of an optical system for a video camera which generates video signals with each video signal having a video field, comprising:

• a group of zoom lenses for zooming in on an object,
• a group of focus lenses for focusing on the object,
• position detecting means for detecting present positions of said group of zoom lenses and said group of focus lenses respectively,
• target position calculating means for calculating target positions of said group of zoom lenses and said group of focus lenses respectively for each video field with the period of each video field having a moving state and a tracking state for said group of zoom lenses and focus lenses respectively,
• driving means for driving said group of zoom lenses and said group of focus lenses,
• control means for controlling said driving means in response to said target position calculating means to position said group of zoom lenses and said group of focus lenses respectively to said target position in each video field,
• evaluation means for evaluating the target positions established by said target position calculating means in the video field for the video period immediately preceding movement of the lenses to the new target positions in a subsequent video field to determine if the target positions in the preceding video period are in the tracking state for each group of lenses and if residual deviations therefrom lie within predetermined values respectively and with said evaluation means evaluating the effect of gravity on said optical system in each video field period, and
• correction means for calculating correcting values for canceling errors for target position calculations from the effect of gravity, said correcting values to be provided to said control means in response to an output from said position detecting means, and an output from said evaluation means and an output from said control means to said correction means.