HIGH-SPEED LENS Russian patent published in 2009 - IPC G02B9/34 G02B13/14 

FIELD: physics; optics.

SUBSTANCE: present invention pertains to lenses working in the middle and far infrared range and can be used in thermal imaging devices. The lens consists of four separate lenses placed in series on a beam path: a positive meniscus, the concave surface of which faces the image, a negative meniscus, the concave surface of which faces the object, a meniscus, the convex surface of which faces the image, and a positive meniscus, the convex surface of which faces the object. The first, third and fourth lenses are made from germanium, and the ratio of the value of the third air gap to the focal length of the whole lens ranges from 0 to 0.05. The index of refraction of the material of the second lens is greater than 1.25 and less than 3.9. The following ratios are satisfied: R₇=R₈; 0.8<R₅/R₆<0.96; where R₅, R₆, R₇, R₈ are radii of curvature of the fifth, sixth, seventh and eighth optical surfaces.

EFFECT: increased technological effectiveness and longer focal distance and aperture ratio with high image quality.

4 cl, 1 dwg