| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact variable power optical system capable of attaining an improved performance of forming an image, even in the case a member by which an astigmatic difference is caused is laid in a lens pack. SOLUTION: The variable power optical system is composed of four lens groups Gr1 to Gr4, and zooming is executed by changing each lens group distance d5, d10 and d15, and in the lens pack, the system is provided with sheets of plane glass P1 and P2 by which the astigmatic difference is generated. In the 4th group Gr4 which is closest to the image side among the lens groups and which is fixed during the zooming operation, a cylinder lens CY is arranged as a correcting member for correcting the astigmatic difference.
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