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US 5,267,086 AGranted
Soft focus lens system
AssigneeAsahi Kogaku Kogyo Kabushiki Kaisha
InventorHiroyuki Hirano
Life of this patent
Estimating the term…
Abstract
An autofocusable soft focus lens system includes a movable front lens group having a positive power, and a stationary rear lens group having a negative power.
Claims17
A soft focus lens system, comprising:
- a front lens group having a positive overall power, and
- a rear lens group having a negative overall power and consisting of a single negative lens element, wherein only the front lens group is moved to perform focusing while the rear lens group remains fixed, said front lens group comprising, in order from an object side, a positive first lens element, a negative second lens element, a negative third lens element and a positive fourth lens element, said front lens group satisfying the following condition:
- 0.7<f.sub.F /f<0.95,
- where
- f:
- a focal length of the overall lens system at infinity, and
- f.sub.F :
- a focal length of the front lens group.
5 more elements
A soft focus lens system, comprising:
- a front lens group having a positive overall power, and
- a rear lens group having a negative overall power and consisting of a single negative lens element, wherein only the front lens group is moved to perform focusing while the rear lens group remains fixed, said front and rear lens groups providing image magnification of up to 1/3 for close-up image shots, said front lens group comprising, in order from an object side, a positive first lens element, a negative second lens element, a negative third lens element and a positive fourth lens element.
A soft focus lens system, comprising:
- a front lens group having a positive overall power, and
- a rear lens group having a negative overall power, wherein only the front lens group is moved to perform focusing while the rear lens group remains fixed, said front lens group comprising, in order from an object side, a positive first lens element, a negative second lens element, a negative third lens element and a positive fourth lens element, said rear lens group comprising a fifth lens element, said lens system satisfying the following conditions:
- 0.7<f.sub.F /f<0.95,
- and
- 55<v.sub.5,
- where
- f:
- a focal length of the overall lens system at infinity,
- f.sub.F :
- a focal length of the front lens group and
- v.sub.5 :
- the Abbe number of said fifth lens element.
9 more elements
A soft focus lens system, comprising:
- a front lens group having a positive overall power, and
- a rear lens group having a negative overall power, wherein only the front lens group is moved to perform focusing while the rear lens group remains fixed, said front and rear lens groups providing image magnification of up to 1/3 for close-up image shots, said front lens group comprising, in order from an object side, a positive first lens element, a negative second lens element, a negative third lens element and a positive fourth lens element, said rear lens group comprising a fifth lens element, said rear lens group satisfying the following condition:
- 55<.nu..sub.5
- where .nu..sub.5 represents an Abbe number of the fifth lens element.
1 more element
A soft focus lens system, comprising:
- a front lens group having a positive overall power, and
- a rear lens group having a negative overall power, wherein only the front lens group is moved to perform focusing while the rear lens group remains fixed, said front lens group comprising, in order from an object side, a positive first lens element, a negative second lens element, a negative third lens element and a positive fourth lens element, said rear lens group comprising a fifth lens element, said front lens group satisfying the following conditions:
- 0.7<f/.sub.F /f<0.95
- and
- 55<.nu..sub.5,
- where
- f:
- a focal length of the overall lens system at infinity,
- f.sub.F :
- a focal length of the front lens group, and
- .nu..sub.5 :
- an Abbe number of the fifth lens element.
9 more elements
A soft focus lens system, comprising:
- a front lens group having a positive overall power, and
- a rear lens group having a negative overall power, wherein only the front lens group is moved to perform focusing while the rear lens group remains fixed, said front lens group comprising, in order from an object side, a positive first lens element, a negative second lens element, a negative third lens element and a positive fourth lens element, said rear lens group exclusively comprising a single, negative fifth lens element, said lens system satisfying the following conditions:
- 0.7f.sub.F /f<0.95
- 0.1<-f/f.sub.R <0.5
- and
- 55<.nu..sub.5
- where
- f:
- a focal length of the overall lens system at infinity,
- f.sub.F :
- a focal length of the front lens group,
- f.sub.R :
- the focal length of the rear lens group and
- .nu..sub.5 :
- the Abbe number of the fifth lens element.
12 more elements
Dependencies are inferred from the claim text.