Attachment lens system
AssigneeFuji Photo Optical Co., Ltd.
InventorKatsuhisa Tsutsumi
Life of this patent
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Abstract
An attachment lens optical system for extending a focal length of a camera lens and balancing axial chromatic aberrations of the camera lens comprises, in order from the object side, a first lens group having a negative power single lens element, a second lens group including a cemented doublet of a biconcave lens element and a biconvex lens element, a positive power third lens group including three lens elements, and a negative power fourth lens group including a cemented doublet of two lens elements.
Claims10
An attachment lens optical system disposed between a camera lens and an image forming device for extending an overall focal length of the camera lens, said attachment lens optical system comprising, in order from the object side:
- a first lens group consisting of a single lens element selected from a group of a biconcave lens element and a negative power meniscus lens element having a convex object side surface,
- a second lens group including a cemented doublet comprising a biconcave lens element and a biconvex lens element,
- a positive power third lens group including at least a biconvex lens element, and
- a fourth lens group including at least a biconcave lens element, wherein said fourth lens group comprises a cemented lens, and wherein said fourth lens group has a negative power.
An attachment lens optical system disposed between a camera lens and an imaging device for extending an overall focal length of the camera lens, said attachment lens optical system comprising, in order from the object side:
- a first lens group comprising a first lens which is one of a biconcave lens element and a negative power meniscus lens element having a convex object side surface;
- a second lens group including a cemented doublet comprising a biconcave lens element and a biconvex lens element;
- a positive power third lens group including at least a biconvex lens element;
- and
- a fourth lens group including at least a biconcave lens element;
- wherein said attachment lens optical system satisfies the following conditions:
- 1.8<N1
- 1.8<N21
- ν22<ν21
- ν44<30
- where N1 and N21 are the indices of refraction of the first lens and the biconcave lens element of the second lens group, respectively, and ν21, ν22 and ν44 are the Abbe numbers of the biconcave lens element of the second lens group, the biconvex lens element of the second lens group and the biconcave lens element of the fourth lens group, respectively.
An attachment lens optical system disposed between a camera lens and an imaging device for extending an overall focal length of the camera lens, said attachment lens optical system comprising, in order from the object side:
- a first lens group comprising a first lens which is one of a biconcave lens element and a negative power meniscus lens element having a convex object side surface;
- a second lens group including a cemented doublet comprising a biconcave lens element and a biconvex lens element;
- a positive power third lens group including at least a biconvex lens element;
- and
- a fourth lens group including at least a biconcave lens element;
- wherein said attachment lens optical system satisfies the following condition:
- ν44<30
- where ν44 is the Abbe number of the biconcave lens element of the fourth lens group.
An attachment lens optical system disposed between a camera lens and an imaging device for extending an overall focal length of the camera lens, said attachment lens optical system comprising, in order from the object side:
- a first lens group comprising a negative power meniscus first lens element having a convex object side surface;
- a second lens group including a cemented doublet comprising a biconcave lens element and a biconvex lens element;
- a positive power third lens group including at least a biconvex lens element;
- and
- a fourth lens group including at least a biconcave lens element, wherein said attachment lens optical system satisfies the following condition:
- 1.1≦β<1.3
- where β is the magnification of the attachment lens optical system.
Dependencies are inferred from the claim text.