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US 4,359,272 AGranted
Internal focusing telephoto lens
AssigneeBalcon Industries, Inc.
InventorMelvyn H. Kreitzer
Life of this patent
Estimating the term…
Abstract
A new and improved telephoto lens comprising a stationary front positive group, a movable second group employed for internal focusing, a stationary third positive group and a stationary fourth negative group. The lens has a very low telephoto ratio and a very short focusing motion accompanied by a high degree of aberrational correction, all of which is achieved without the use of crystalline or expensive glass materials.
Claims11
A telephoto lens of fixed equivalent focal length comprising from the front end to the rear end:
- a first positive group;
- a second negative group comprising a doublet including a positive element and a biconcave element;
- and
- a third positive group and a fourth negative group;
- said first, third, and fourth groups being stationary in said lens;
- said second group being axially movable for focusing of said lens.
3 more elements
Dependencies are inferred from the claim text.