| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a variable power optical system provided with vibration- proof function which obtains a still image by optically correcting the blur of a photographic image when the variable power optical system vibrates. SOLUTION: This variable power optical system has a 1st lens group L1 with positive refracting power which is fixed at the time of power variation and focusing, a 2nd lens group L2 with negative refracting power with a power varying function, a 3rd lens group L3 with positive refracting power, a 4th lens group L4 with positive refracting power which corrects an image plane varying as the power varies and has a focusing function in this order from the object side. In this case, the 3rd lens group L3 is moved at right angles to the optical axis to correct a blur of a photographic image when the variable power optical system vibrates and the 2nd lens group L2 consists of a negative meniscus lens 21 which has a very strong concave surface to the image plane side, a negative lens 22, a positive lens 23, and a negative lens 24 in this order from the object side and satisfies a condition of 0.05<|f2/ft|<0.07, where ft is the focal length of the whole system at the telephoto end and f2 is the focal length of the 2nd lens group.</p> |
