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Focal length transitional method, auxiliary lens for transiting focal lengths, and lens system and finder having focal length transitional function
Focal length transitional method, auxiliary lens for transiting focal lengths, and lens system and finder having focal length transitional function
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机译：焦距过渡方法，用于过渡焦距的辅助透镜以及具有焦距过渡功能的透镜系统和取景器
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摘要
A varifocal lens system is constructed by two or more lens groups and has a function for changing a focal length of the lens system by changing a distance between the lens groups while the position of an image face is constantly held. An auxiliary lens constructed by two lens groups having negative and positive refracting powers is inserted into an increased clearance between lens groups in a shortest focal length state such that a lens group having the negative refracting power is located on an object side. The focal length of the lens system is transited to the side of a focal length shorter than the shortest focal length without changing the position of the image face by the insertion of the auxiliary lens. The auxiliary lens can be constructed by a single lens group having negative refracting power. In accordance with the above structure, focal lengths of the varifocal lens system can be transited to each other without increasing an entire length of the varifocal lens system.
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