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US 4,732,459 AGranted
Fast telephoto lens
AssigneeNippon Kogaku K. K.
InventorKiyoshi Hayashi
Life of this patent
Estimating the term…
Abstract
A fast telephoto lens has a longer focal length of 300 to 400 mm, and an F-number of about 2.0 to 2.8, which does not utilize a floating mechanism, has a small deviation in aberration when the lens is focused on an object, and has a simple construction for shifting only one lens group. The fast telephoto lens is of internal focusing type and comprises positive, negative and positive lens groups from the object side, and only the negative (second) lens group is shifted to obtain an in-focus state.
Claims15
A fast telephoto lens, which has an F-number of approximately 2.0 to 2.8, consisting of:
- a first converging lens group;
- a diverging lens group;
- and
- a second converging lens group;
- said first converging lens group, said diverging lens group and said second converging lens group being arranged in succession from the object side, said first converging lens group and said diverging lens group being arranged to constitute an afocal system with respect to an object at infinity, said diverging lens group being shifted toward an image so as to focus said fast telephoto lens on a close distance object, said first converging lens group including at least two positive lens components and one negative lens component which are sequentially arranged from the object side, said diverging lens group including two negative lens components at least one of which consists of an achromatic lens component constituted by a positive lens and a negative lens, said second converging lens group including at least one achromatic lens component constituted by a negative lens and a positive lens, and said fast telephoto lens satisfying conditions below:
- 0.7f.ltoreq.f.sub.1 <f
- -0.5<(rd+rc)/(rd-rc)<0
- where
- f:
- overall focal length of said fast telephoto lens
- f.sub.1 :
- focal length of said first converging lens group
- rc:
- radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the image, the surface being that closest to the object
- rd:
- radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the image, the surface being that closest to the image.
13 more elements
A fast telephoto lens, which has an F-number of approximately 2.0 to 2.8, comprising:
- a first converging lens group;
- a diverging lens group;
- and
- a second converging lens group;
- said first converging lens group, said diverging lens group and said second converging lens group being arranged in succession from the object side, said first converging lens group and said diverging lens group being arranged to constitute an afocal system with respect to an object at infinity, said diverging lens group being shifted toward an image so as to focus said fast telephoto lens on a close distance object, said first converging lens group including at least two positive lens components and one negative lens component which are sequentially arranged from the object side, said diverging lens group including two negative lens components at least one of which consists of an achromatic lens component constituted by a positive lens and a negative lens, said second converging lens group including at least one achromatic lens component constituted by a negative lens and a positive lens, and said fast telephoto lens satisfying conditions below:
- ##EQU2## where f:
- overall focal length of said fast telephoto
- lens
- f.sub.1 :
- focal length of said first converging lens group
- rc:
- radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the image, the surface being the closest to the object
- rd:
- radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the image, the surface being that closest to the image
- f.sub.2 :
- focal length of said diverging lens group
- ra:
- radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the object, the surface being that closest to the object
- rb:
- radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the object, the surface being that closest to the image
- d.sub.4 :
- a second space in said first converging lens group
- na:
- refractive index of the positive lens of the achromatic component of said diverging lens group, the positive lens being located near the object
- nb:
- refractive index of the negative lens of the achromatic component of said diverging lens group, the negative lens being located near the object
- .nu.a:
- Abbe number of the positive lens of the achromatic component of said diverging lens group, the positive lens being located near the object
- .nu.b:
- Abbe number of the negative lens of the achromatic component of said diverging lens group, the negative lens being located near the object.
27 more elements
Dependencies are inferred from the claim text.