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US 6,246,517 B1Granted
Lenses for the 1.50 to 2.55 micron band
AssigneeThe United States of America as represented by the Secretary of the Army
InventorJohn M. Hall
Life of this patent
Estimating the term…
Abstract
A lens assembly for near infrared comprising two double convex elements separated by two double concave elements. The first element being the most durable, the center elements being the least expensive and the last element having the greatest focussing power.
Claims5
An objective lens assembly for focussing light in the wavelength band from 1.5 to 2.55 microns, including:
- a first and a second double convex lens element separated by first and second adjacent double concave lens elements, said lens elements being centered normally on a straight optical axis;
- said concave lens elements made of fused quartz;
- a thin opaque apertured stop element separating said double concave lenses;
- the size shape and spacing of said elements being adjusted to provide a speed no slower than f1.8, a focal length of at least 28 cm, and at least a 30 degree field of view onto at least a 15 mm image plane;
- and
- an open ended tubular housing engaging only the edges of said elements to maintain their spacing and orientation.
3 more elements
Dependencies are inferred from the claim text.