| 摘要 |
PURPOSE: To control automatically the focal length of a zoom lens quickly and accurately so that an image pickup field angle is almost unchanged even when an aspect ratio is selected by controlling the focal length of the zoom lens so that an image pickup view angle before and after the selection of the aspect ratio is almost the same. CONSTITUTION: An optical image of an object 1 is given to a processor 3 via a zoom lens 2. The processor 3 generates a video signal of an aspect ratio (16:9) or another aspect ratio (4:3) selected by a changeover device 7 and outputs a video signal 4 after correction processing. When the changeover device 8 selects the changeover device from the 1st aspect ratio to the 2nd aspect ratio or vice versa, an arithmetic unit 8 obtains the focal length after the changeover from equation of Y=αX so that a field angle of an output 4 is switched by a prescribed ratioαeven when the aspect ratio is selected from focal length X of the lens 2 detected by a detector 5. The focal length of the lens 2 is controlled by receiving the arithmetic result.
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