Zoom lens having weak plastic element
First Claim
1. A zoom lens including, from front to rear, a first positive lens group consisting entirely of a front negative glass component and a rear positive glass component, said components being separated by an aperture stop and a rear negative group consisting entirely of a front weak plastic element having sufficiently weak power so that it does not unacceptably affect focus with normal variations in temperature, said plastic element having an aspheric surface and a rear negative component, all of the elements of the zoom lens except said weak plastic element being glass elements.
2 Assignments
0 Petitions
Accused Products
Abstract
A zoom lens suitable for an inexpensive camera has a front positive lens group and a rear negative lens group. Both groups move for zooming with the rear negative group providing most of the variation in focal length. The front positive group includes a front negative component and a rear positive component while the rear negative group includes a rear negative component and a weak plastic element having at least one aspheric surface. The plastic element is sufficiently weak that it does not cause variation in focus with normal variations in temperature and relative humidity. All other elements in the zoom lens are glass.
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Citations
31 Claims
- 1. A zoom lens including, from front to rear, a first positive lens group consisting entirely of a front negative glass component and a rear positive glass component, said components being separated by an aperture stop and a rear negative group consisting entirely of a front weak plastic element having sufficiently weak power so that it does not unacceptably affect focus with normal variations in temperature, said plastic element having an aspheric surface and a rear negative component, all of the elements of the zoom lens except said weak plastic element being glass elements.
- 8. A zoom lens including, from front to rear, a first positive lens group consisting entirely of a front negative lens component and a rear positive lens element, separated by an aperture stop and a rear negative group consisting entirely of a front weak plastic element having sufficiently weak power so that it does not unacceptably affect focus with normal variations in temperature, said plastic element having an aspheric surface and a rear negative component, all of the elements of the zoom lens except said weak plastic element being glass elements.
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14. A zoom lens including, from front to rear, a first positive lens group and a second negative lens group, both of said groups being movable for zooming, said second lens group including a weak plastic element having sufficiently weak power so that it does not unacceptably affect focus with normal variations in temperature, said plastic element having at least one aspheric surface, and all other elements in the zoom lens being glass, wherein the radii of curvatures of said plastic element are each less than 1/3 of the focal length of the lens at its wide angle position.
- 15. A zoom lens including, from front to rear, a first positive lens group consisting entirely of glass elements including a front negative component and a rear positive component, said rear positive component including no negative lens elements, said front negative and said rear positive components being separated by an aperture stop and a rear negative group consisting entirely of a front weak plastic element having sufficiently weak power so that it does not unacceptably affect focus with normal variations in temperature, said plastic element having an aspheric surface and a rear negative component, all of the elements of the zoom lens except said weak plastic element being glass elements.
- 22. A zoom lens consisting from front to mar a first negative lens element, a second positive lens element which is biconvex, a third weak plastic lens element having sufficiently weak power so that it does not unacceptably affect focus with normal variations in temperature, and a fourth negative lens element having a concave surface facing said weak plastic lens element.
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25. A wide angle zoom lens covering a half field angle of at least 20°
- , said lens including, from front to rear, a first positive lens group and a second lens group including a weak plastic element having absolute value of the radii of curvature of each surface less than 1/3 of the focal length of the lens in its wide angle position, said plastic element having at least one aspheric surface, and all other elements in the zoom lens being glass, said lens elements having powers and spacing to provide said ;
half field angle coverage of at least 20°
. - View Dependent Claims (26)
- , said lens including, from front to rear, a first positive lens group and a second lens group including a weak plastic element having absolute value of the radii of curvature of each surface less than 1/3 of the focal length of the lens in its wide angle position, said plastic element having at least one aspheric surface, and all other elements in the zoom lens being glass, said lens elements having powers and spacing to provide said ;
- 27. A zoom lens including, from front to rear, a first positive lens group consisting entirely of a front negative glass component and a rear positive glass component, said components being separated by an aperture stop and a rear negative group consisting entirely of a front weak plastic element having absolute value of the radii of curvature of each surface less than 1/3 of the focal length of the lens in its wide angle position, said plastic element having an aspheric surface and a rear negative component, all of the elements of the zoom lens except said weak plastic element being glass elements.
Specification