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US 5,331,464 AGranted
Zoom lens system
AssigneeAsahi Kogaku Kogyo Kabushiki Kaisha
InventorsTakayuki Ito, Sachio Hasushita
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AssigneeAsahi Kogaku Kogyo Kabushiki Kaisha
InventorsTakayuki Ito, Sachio Hasushita
Estimating the term…
A zoom lens system comprises, in order from the object side, a negative first lens group N, a diaphragm stop A, a positive second lens group P and a blocking element B for blocking deleterious rays of light, with the first and second lens groups N and P movable for zooming, and with the diaphragm stop A moving independently of the second lens group P during zooming. The lens system satisfies the conditions 2.5<Xs/fs<3.0, 0<.DELTA.XA/fs<X2/fs, and 0.ltoreq..DELTA.XB/fs<.DELTA.X2/fs, where Xs is the distance from the diaphragm stop to the image plane at the wide-angle end, fs is the focal length of the overall system at the wide-angle end, .DELTA.XA is the range of movement of the diaphragm stop, and .DELTA.XB is the range of movement of the second lens group. This lens system has the diaphragm stop disposed in the appropriate position so that the compactness of lens barrel will not be impaired even if a motor is incorporated in it, and yet the system is capable of preventing the occurrence of deleterious flare rays of light.
A zoom lens system comprising, in order from the object side, a negative first lens group, a diaphragm stop, a positive second lens group and a blocking means capable of moving for blocking deleterious rays of light, said system performing zooming by moving said first and second lens groups, with said diaphragm stop moving independently of said second lens group during zooming, said system satisfying the following conditions:
A zoom lens system comprising, in order from the object side, a negative first lens group, a first blocking means capable of moving for blocking deleterious rays of light, a positive second lens group and a second blocking means capable of moving for blocking deleterious rays of light, said system performing zooming by moving said first and second lens groups, with said first and second blocking means moving independently of said second lens group during zooming, said system satisfying the following conditions:
Dependencies are inferred from the claim text.