| 摘要 |
PURPOSE:To easily obtain a high variable power ratio by constituting three photographing systems by inserting and attaching selectively two auxiliary lens systems having positive and negative refractive powers, onto the rear optical axis of a main lens system, and selecting and using one of them. CONSTITUTION:The titled optical system is constituted so that a main lens system 1 having a positive refractive power, and the first auxiliary lens system 2 having a positive refractive power and the second auxiliary lens system 3 having a negative refractive power which can be inserted and detached on the optical axis in the rear of the main lens system are provided together, and one photographing system can be selected, among three photographing systems of the third photographing system C by the main lens system and the second auxiliary lens system, as the first photographing system A by the main lens system and the first auxiliary lens system and the second photographing system B by only the main lens system. When focus distances of the first, the second and the third photographing systems are denoted as fW, fM, and fT, respectively, fW<fM<fT, and also, when intervals to the main lens system and the auxiliary lens system in the third photographing system, and the overall length of the lenses of the main lens system are denoted as DW and DT, and TM, respectively, the conditions of the expressions are satisfied. In this way, even if any photographing system is used, a feed quantity of the lens system in case of focusing becomes constant, and a high variable power is easily obtained.
|
