INFRARED OBJECTIVE WITH FLUENTLY CHANGING FOCAL DISTANCE Russian patent published in 2007 - IPC G02B13/16 G02B13/14 

FIELD: the invention refers to optical devices.

SUBSTANCE: the objective has in-series located the first immovable component, the second and the third components installed with possibility of displacement along the optical axle and the immovable fourth and the fifth components, the fifth component is fulfilled in the shape of the first and the second positive convex-concave lenses. The focal distances f₁, f₂, f_5, correspondingly of the first, the second and the fifth components are chosen depending from maximal focal distance f₁ of the infrared objective in the following limits: f₁=(from 1.22 to 1.24)f_t; f₂=(from -0.48 to -0.5)f_t; f₅=(from 0.41 to o.42)f_t. The second surface of the first lens of the fifth component is fulfilled aspherical.

EFFECT: reduces the length of the infrared objective relatively to its maximal focal distance, increases ratio of maximal focal distance to minimal, and also increases concentration of energy in the given blur circle.

3 cl, 1 dwg