Zoom lens
First Claim
Patent Images
1. A zoom lens comprising;
- a first lens group having a positive refracting power, said first lens group being stationary relative to an image plane, said first lens group comprising a first cemented lens comprised of a first negative meniscus lens and one of a plano-convex and a bi-convex second lens, said first lens group further comprising a third positive meniscus lens, said second lens being located between said first and third lens, said third lens being located between said second lens and said image plane;
a second lens group having a negative refracting power, said second lens group being movable, and comprising a negative meniscus fourth lens, and a second cemented lens comprised of a bi-concave fifth lens and a plano-convex sixth lens, said second lens group being located between said first lens group and said image plane, said fourth lens being located between said third lens and said fifth lens, said fifth lens being located between said fourth lens and said sixth lens;
a third lens group having a positive refracting power, said third lens group being stationary relative to said image plane, and comprising one of a bi-convex and a plano-convex seventh lens, said third lens group being located between said second lens group and said image plane; and
a fourth lens group having a positive refracting power, said fourth lens group being movable, and comprising a cemented lens of a negative meniscus eighth lens and a bi-convex ninth lens, said fourth lens group being located between said third lens group and said image plane, said eighth lens being between said seventh lens and said ninth lens;
wherein each of said third, fourth and seventh lenses is made of plastic; and
wherein each of said fourth and seventh lenses comprises an aspherical lens surface which is aspherical, and each of said first, second, fifth, sixth, eighth and ninth lenses is a spherical glass lens defined only by spherical surfaces.
1 Assignment
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Accused Products
Abstract
An inner focus type zoom lens is a nine lens system including third, fourth and seventh lenses which are plastic lenses including aspherical surfaces, and first, second, fifth, sixth, eighth and ninth lenses which are spherical glass lenses. This zoom lens system can reduce the manufacturing cost by employing the plastic lenses and eliminating aspherical glass surfaces. Moreover, this zoom lens system is superior in correction of aberrations and less susceptible to temperature changes.
31 Citations
7 Claims
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1. A zoom lens comprising;
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a first lens group having a positive refracting power, said first lens group being stationary relative to an image plane, said first lens group comprising a first cemented lens comprised of a first negative meniscus lens and one of a plano-convex and a bi-convex second lens, said first lens group further comprising a third positive meniscus lens, said second lens being located between said first and third lens, said third lens being located between said second lens and said image plane; a second lens group having a negative refracting power, said second lens group being movable, and comprising a negative meniscus fourth lens, and a second cemented lens comprised of a bi-concave fifth lens and a plano-convex sixth lens, said second lens group being located between said first lens group and said image plane, said fourth lens being located between said third lens and said fifth lens, said fifth lens being located between said fourth lens and said sixth lens; a third lens group having a positive refracting power, said third lens group being stationary relative to said image plane, and comprising one of a bi-convex and a plano-convex seventh lens, said third lens group being located between said second lens group and said image plane; and a fourth lens group having a positive refracting power, said fourth lens group being movable, and comprising a cemented lens of a negative meniscus eighth lens and a bi-convex ninth lens, said fourth lens group being located between said third lens group and said image plane, said eighth lens being between said seventh lens and said ninth lens; wherein each of said third, fourth and seventh lenses is made of plastic; and wherein each of said fourth and seventh lenses comprises an aspherical lens surface which is aspherical, and each of said first, second, fifth, sixth, eighth and ninth lenses is a spherical glass lens defined only by spherical surfaces. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A zoom lens comprising;
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a first lens group having a positive refracting power, said first lens group being stationary relative to an image plane, said first lens group comprising a first cemented lens comprised of a first negative meniscus lens and one of a plano-convex and a bi-convex second lens, said first lens group further comprising a third positive meniscus lens, said second lens being located between said first and third lenses, said third lens being located between said second lens and said image plane; a second lens group having a negative refracting power, said second lens group being movable, and comprising a negative meniscus fourth lens, and a second cemented lens comprised of a bi-concave fifth lens and a plano-convex sixth lens, said second lens group being located between said first lens group and said image plane, said fourth lens being located between said third lens and said fifth lens, said fifth lens being located between said fourth lens and said sixth lens; a third lens group having a positive refracting power, said third lens group being stationary relative to said image plane, and comprising one of a bi-convex and a plano-convex seventh lens, said third lens group being located between said second lens group and said image plane; and a fourth lens group having a positive refracting power said fourth lens group being movable, and comprising a cemented lens of a negative meniscus eighth lens and a bi-convex ninth lens, said fourth lens group being located between said third lens group and said image plane, said eighth lens being between said seventh lens and said ninth lens; wherein each of said third, fourth and seventh lenses is made of plastic; wherein said third and fourth lenses are identical in material; and wherein said first and second lens groups, and said third and fourth lenses have focal lengths which satisfy the following three conditions; (1) 0.4<
fA/f3<
1(2) 0.4<
fb/f4<
1(3) 0.7<
f3·
fB/f4·
fA<
1.4where fA is a focal length of the first lens group, fB is a focal length of the second lens group, f3 is a focal length of the third lens, and f4 is a focal length of the fourth lens.
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Specification