Zoom lens
First Claim
1. A zoom lens comprising in order from the object end a positive power of first lens means which remains stationary during zooming, a negative power of second lens means movable along an optical axis of the zoom lens between a wide-angle end where the zoom lens has a shortest focal length and a telephoto end where the zoom lens has a longest focal length for zooming, a positive power of third lens means and a positive power of fourth lens means both of which are movable along the optical axis during zooming, so that as said second negative lens means moves from said wide-angle end to said telephoto end for zooming, the third and fourth lens means are moved so as to initially decrease a relative axial distance between the third and fourth positive lens means and subsequently increase the axial distance while the second negative lens means moves, thereby correcting a change in focus caused by the second negative lens means during zooming.
1 Assignment
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Accused Products
Abstract
A zoom lens comprises first to fourth lens groups in order from the subject end. Second to third lens groups move along optical axis of the zoom lens for zooming between a wide-angle end where the zoom lens has the shortest focal length and a telephoto end where the zoom lens has the longest focal length. During the zooming, first lens group remains stationary. As the second lens group moves towards the image end for zooming from the wide-angle end to the telephoto end, the third and fourth lens groups are moved so as to initially decrease a relative axial distance therebetween and subsequently increase the axial distance, thereby correcting changes in focus caused by the axial movement of the second lens group during zooming.
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Citations
40 Claims
- 1. A zoom lens comprising in order from the object end a positive power of first lens means which remains stationary during zooming, a negative power of second lens means movable along an optical axis of the zoom lens between a wide-angle end where the zoom lens has a shortest focal length and a telephoto end where the zoom lens has a longest focal length for zooming, a positive power of third lens means and a positive power of fourth lens means both of which are movable along the optical axis during zooming, so that as said second negative lens means moves from said wide-angle end to said telephoto end for zooming, the third and fourth lens means are moved so as to initially decrease a relative axial distance between the third and fourth positive lens means and subsequently increase the axial distance while the second negative lens means moves, thereby correcting a change in focus caused by the second negative lens means during zooming.
- 22. A zoom lens comprising in order from the subject end a positive power of first lens means movable along an optical axis of the zoom lens for focusing but remaining stationary during zooming, a negative power of second lens means, a positive power of third lens means, a positive power of fourth lens means, a low-pass filter disposed stationary after said fourth lens means and aperture means disposed closely to said third lens means between said second and fourth leans means, said second to fourth lens means being moved relatively to one another along said optical axis for zooming between a wide-angle end where the zoom lens has a shortest focal length and a telephoto end where the zoom lens has a longest focal length so as to decreasingly change an axial distance between said second and third lens means during a zooming from said wide angle end to said telephoto end, and said aperture means being moved along said optical axis in the same axial direction and distance as the third positive lens means during zooming.
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40. A zoom lens comprising in order from the subject end a positive power of first lens means, a negative power of second lens means, a positive power of third lens means, a positive power of fourth lens means, and aperture means disposed closely to said third lens means between said second and fourth lens means, said fourth lens means being moved along the optical axis of said zoom lens for focusing, said second to fourth lens means being moved relatively to one another, while the first lens means remains stationary, during zooming in such a way that third to fourth lens means being moved relatively to one another along said optical axis for zooming between a wide-angle end where the zoom lens has a shortest focal length and a telephoto end where the zoom lens has a longest focal length so as to decreasingly change an axial distance between said second and third lens means during a zooming from said wide-angle end to said telephoto end, and said aperture means being moved along said optical axis in the same axial direction and distance as the third positive lens means during zooming.
Specification