Patent ID: 7672045
Filing Date: 2010-03-02
Classification: G02B

Abstract:
1. A two-element objective lens for an: infrared optical system, the lens consisting of: a) a first lens element receiving incident radiation and having front and rear surfaces, and b) a second lens element receiving incident radiation from the first lens element and having front and rear surfaces, the first and second lens elements forming an image on a focal plane; and c) an aperture stop placed adjacent to the first lens element and between the first and second lens elements; wherein at least three of said surfaces of the first and second lens elements comprise aspheric surfaces; the lens has an f-number less than about 2; the lens has a field-of-view less than about 30 degrees; the lens has an effective focal length less than about 6 inches; and the first and second lens elements are made from a material selected to pass radiation in the infrared band of the electromagnetic spectrum; and wherein the lens features diffraction-limited performance, in which the modulation transfer function approximately matches a diffraction limit of the lens.