1.  Field of the Invention
The present invention relates generally to a vibration-proof optical system, and more particularly to a vibration-proof optical system that is suitably mounted on a picture-taking system for photographic or video cameras to compensate for image defects, esp.,  image blurs caused by vibrations or other shakes. 
2.  Background of Related Art
When photographic or video cameras are used to take photographs from within cars or airplanes while they are on the move, vibrations are transmitted to the picture-taking systems, resulting in image defects or blurs.  Prior means for eliminating such defects, for instance, are disclosed in JP-A 1-191112, 1-191113, 2-35406, 2-81020, 2-124521 and 3-141318 as well as U.S. Pat.  Nos.  5,069,537 and 4,844,602. 
It is here to be noted that JP-A 1-191112, 1-191113 and 2-35406 correspond together to U.S. Pat.  No.  5,270,857; JP-A 2-81020 to U.S. Pat.  No.  5,182,671; JP-A 2-124521 to U.S. Pat.  No.  5,039,211; and JP-A 3-141318 to U.S. Pat.  No.  5,172,268. 
JP-A 1-191112, 1-191113 and 2-35406 teach a taking lens system comprising a plurality of lens units or groups, some of which are moved in a direction perpendicular to the optical axis for compensating for image blurs. 
JP-A 2-81020 and 2-124521 disclose a taking lens system comprising a plurality of lens units, some of which are moved in a direction perpendicular to the optical axis or rotated around a certain fixed point to make compensation for image blurs. 
JP-A 3-141318 shows a principal lens system for forming an object image.  Between this principal lens system and the image surface there is a meniscus lens concave on the exit pupil of the principal lens system, which is in turn rotated around one point on the optical axis for compensating for image blurs. 
A problem with the systems disclosed in JP-A 1-191112, 1-191113, 2-35406, 2-81020 and 2-124521 are, however, that the decentering drive lens unit for compensating for image blurs also serves as a lens unit that is moved in the optical axis direction during zooming, making the lens drive mechanism complicated in structure.  Another problem is that control loads for driving a plurality of lenses in a decentering manner, too, lead to size increases. 
A problem with the system disclosed in JP-A 3-141318 is that when the amount of rotation of the compensating lens is increased, there is a need of allowing for a space to prevent interference of the final lens of the principal lens system and the compensating lens, because the compensating lens is a meniscus lens concave on the exit pupil.  Another problem is that the amount of rotation of the compensating lens must be increased to compensate for a large image blur, making it difficult to compensate for deterioration of the ability to form images after the rotation.