Variable magnification optical zoom lens system
First Claim
1. A variable magnification zoom lens system having an optical axis comprising, in order from an object side,a first lens group consisting of two negative lenses and a positive lens and having an overall negative refractive power;
- a second lens group having a positive refractive power; and
a third lens group, which is fixed along the optical axis and overall has a positive refractive power;
with the first and second lens group arranged to be driven such that when zooming from a maximum wide-angle state to a maximum telephoto state, the distance between said first lens group and said second lens group is reduced, and at the same time, the distance between said second lens group and said third lens group is increased; and
the following conditions are fulfilled;
space="preserve" listing-type="equation">0.7<
f2/|f1|<
1.5
space="preserve" listing-type="equation">3<
f3/fw<
10 wherein;
f1 is;
the focal length of said first lens group;
f2 is;
the focal length of said second lens group;
f3 is;
the focal length of said third lens group; and
fW is;
an overall focal length of said zoom lens system in the maximum wide-angle state wherein said first lens group consists of, in order from the object side,a negative meniscus lens having a convex surface facing toward the object side; and
a cemented lens made up of a bi-concave negative lens and a positive meniscus lens with said positive meniscus lens having a convex surface facing toward the object side.
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Accused Products
Abstract
A variable magnification zoom lens system comprising: in order from the object side, a first lens group having a negative refractive power and a focal length f1; a second lens group having a positive refractive power; and a third lens group having a positive refractive power and a focal length f3 with the first and second lens group arranged to be driven together such that when zooming is performed from the maximum wide-angle state to the maximum telephoto state of the zoom lens system, the first lens group and the second lens group move such that the distance between the first lens group and the second lens group is decreased, and at the same time, the distance between second lens group and the third lens group is increased and with the following condition being fulfilled: 0.4<f3/|f1|<0.8.
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Citations
9 Claims
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1. A variable magnification zoom lens system having an optical axis comprising, in order from an object side,
a first lens group consisting of two negative lenses and a positive lens and having an overall negative refractive power; -
a second lens group having a positive refractive power; and a third lens group, which is fixed along the optical axis and overall has a positive refractive power; with the first and second lens group arranged to be driven such that when zooming from a maximum wide-angle state to a maximum telephoto state, the distance between said first lens group and said second lens group is reduced, and at the same time, the distance between said second lens group and said third lens group is increased; and the following conditions are fulfilled;
space="preserve" listing-type="equation">0.7<
f2/|f1|<
1.5
space="preserve" listing-type="equation">3<
f3/fw<
10wherein; f1 is;
the focal length of said first lens group;f2 is;
the focal length of said second lens group;f3 is;
the focal length of said third lens group; andfW is;
an overall focal length of said zoom lens system in the maximum wide-angle state wherein said first lens group consists of, in order from the object side,a negative meniscus lens having a convex surface facing toward the object side; and a cemented lens made up of a bi-concave negative lens and a positive meniscus lens with said positive meniscus lens having a convex surface facing toward the object side. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A variable magnification zoom lens system having an optical axis comprising, in order from an object side,
a first lens group consisting of two negative lenses and a positive lens and having an overall negative refractive power; -
a second lens group having a positive refractive power; and a third lens group, which is fixed along the optical axis and overall has a positive refractive power; with the first and second lens group arranged to be driven such that when zooming from a maximum wide-angle state to a maximum telephoto state, the distance between said first lens group and second lens group is reduced, and at the same time, the distance between said second lens group and said third lens group is increased; and the following conditions are fulfilled;
space="preserve" listing-type="equation">0.7<
f2/|f1|<
1.5
space="preserve" listing-type="equation">3<
f3/fw<
10wherein; f1 is;
the focal length of said first lens group;f2 is;
the focal length of said second lens group;f3 is;
the focal length of said third lens group; andfW is;
an overall focal length of said zoom lens system in the maximum wide-angle state and wherein said third lens group comprises one positive single lens having at least one aspherical surface wherein said positive single lens is bi-convex; and
an image side surface of said positive single lens is aspherical such that said positive refractive power is reduced from the optical axis toward the periphery.
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Specification