| 摘要 |
PURPOSE:To easily attain a high variable power ratio by inserting selectively two auxiliary lens systems having positive and negative refracting powers respectively onto the optical axis behind a main lens system and selecting and using one of these auxiliary lens systems. CONSTITUTION:The first and second auxiliary lens systems 2 and 3 are so arranged that either of them can be inserted onto and removed from the optical axis behind a main lens system 1. In a figure A, the main lens system 1 and the first auxiliary lens system 2 constitute the first photographing system which has a short focal length and a wide field angle, and two lens systems having positive refracting powers are joined to increase the refracting power of the whole of the system. In a figure B, the first auxiliary lens system 2 shown in the figure A is removed from the optical axis of the main lens system 1 and the main lens system 1 is fed out to the object side, and only the main lens system 1 constitutes the second photographing system in the standard state which has a middle focal length. In a figure C, the main lens system 1 shown in the figure B is fed out to the object side furthermore and the second auxiliary lens system 3 is set onto the optical axis behind the main lens system 1 to constitute the third photographing system having a long focal length.
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