Variable magnification optical system having a capability of stabilizing the image

An optical system having an optical axis, comprising:

• a front lens group;
• a variable magnification group whose image magnification varies due to a process of zooming;
• and
• variable angle prism means positioned inside or to the rear of said variable magnification lens group, said prism means comprising a movable surface for stabilizing an image,
• wherein letting a focal length of the optical system and a distance from the movable surface of said prism means to an image point of all those lens groups positioned on the object side of said variable angle prism means in a first zooming position be denoted by F.sub.0 and S.sub.0, respectively, and a focal length of the optical system and a distance from the movable surface of said prism means to an image point of all those lens groups positioned on the object side of said variable angle prism means in a second zooming position are denoted by F and S, respectively, where if a rear lens group is arranged on the image side of said variable angle prism means, image magnifications of said rear lens group in the first zooming position and the second zooming position are denoted by .beta..sub.B0 and .beta..sub.B, respectively, and the zoom ratio is denoted by Z and putting Z=F/F.sub.0, the following condition is satisfied:
• ##EQU13##

An optical device having an optical axis, comprising:

• a front lens group and a compensation optical means that is located on the image side of said front lens group, that is variable in image magnification due to a process of zooming and is arranged to decenter relative to the optical axis in order to stabilize an image;
• wherein letting a focal length of the optical device and an image magnification of said compensating optical means in a first zooming position be denoted by F.sub.0 and .beta..sub.C0 respectively, and a focal length of the optical device and an image magnification of said compensating optical means in a second zooming position be denoted by F and .beta..sub.C, respectively, wherein, further, if a rear lens group is arranged on the image side of said compensating optical means, image magnifications of said rear lens group in the first zooming position and a second zooming position are denoted by .beta..sub.D0 and .beta..sub.D, respectively, and the zoom ratio is denoted by Z and putting the zoom ratio Z=F/F.sub.0, the following condition is satisfied:
• ##EQU14## and wherein if a rear lens group is not arranged, then the values of .beta..sub.D0 and .beta..sub.D become .beta..sub.D0 =.beta..sub.D =1 and the following condition is satisfied:
• ##EQU15##

An optical device having an optical axis, comprising:

• a front lens group, a zoom lens group located on the image side of said front lens group that is variable in image magnification due to a process of zooming, and a variable angle prism means that is located on the image side of said front lens group;
• wherein letting a focal length of the optical device and a distance from a movable surface of said variable angle prism means to an image point of those lens groups positioned on the object side of said variable angle prism means in a first zooming position be denoted by F.sub.0 and S.sub.0, respectively, and a focal length of the optical device and a distance from the movable surface of said variable angle prism means to the image point of those front lens groups positioned on the object side of said variable angle prism means in a second zooming position are denoted by F and S, respectively, wherein, further, if a rear lens group is arranged on the image plane side of said variable angle prism means, image magnifications of said rear lens group in the first and second zooming positions are denoted by .beta..sub.B0 and .beta..sub.B, respectively, and the zoom ratio is denoted by Z and putting the zoom ratio Z=F/F.sub.0, the following condition is satisfied:
• ##EQU16## and wherein if a rear lens group is not arranged, then the values of .beta..sub.B0 and .beta..sub.B become .beta..sub.B0 =.beta..sub.B =1 and the following condition is satisfied:
• ##EQU17##