Zoom lens system

A zoom lens system comprising:

• a variable lens for changing a focal distance;
• a compensator lens for correcting the shift of focussing caused by the movement of said variable lens such that focussing can be made at a predetermined surface of image-formation;
• a first driving means for driving said variable lens in a direction of an optical axis;
• and
• a second driving means for driving said compensator lens in the direction of the optical axis and driving said compensator lens such that the rear end of the focal depth of an object image at infinity coincides with said surface of image-formation when said object image is photographed.

A zoom lens system comprising:

• a variable lens for changing a focal distance;
• a compensator lens for correcting the shift of focussing caused by the movement of said variable lens such that focussing can be made at a surface of image-formation;
• driving means for driving said variable lens and said compensator lens in a direction of an optical axis;
• a focus lens for performing a focal adjusting;
• an AF control means for driving said focus lens in the direction of the optical axis such that an object image can be made to focus at the surface of image-formation;
• and
• a position regulating means for moving said focus lens to a position where the rear end of the focal depth of said object image at infinity coincides with the surface of image-formation during the photographing of the object image, before the start of photographing.

A zoom lens system comprising:

• a variable lens for changing a focal distance;
• a compensator lens for correcting the shift of focussing caused by the movement of said variable lens such that focussing can be made at a predetermined surface of image-formation;
• a first driving means for driving said variable lens in a direction of an optical axis;
• a second driving means for driving said compensator lens in the direction of the optical axis and driving said compensator lens such that the rear end of the focal depth of an object image at infinity coincides with the surface of image-formation when the object image is photographed;
• a focus lens for performing a focal adjusting;
• an AF control means for driving said focus lens in the direction of the optical axis such that the object image can be made to focus at the surface of image-formation;
• and
• a position regulating means for moving said focus lens to a position where the rear end of the focal depth of the focal image at infinity coincides with the surface of image-formation during the photographing of the object image, before the start of photographing.