IR OBJECTIVE WITH SMOOTHLY CHANGING FOCAL LENGTH Russian patent published in 2008 - IPC G02B15/16 G02B13/14 

FIELD: optical objectives.

SUBSTANCE: IR objective has the following members disposed in series: motionless first component in form of positive concave-convex lens; movable second component composed of first negative convex-concave lens and second convex-concave negative lens; movable third component; motionless fourth and fifth components. Focal lengths f₁ and f₅ of first and second components correspondingly are chosen in dependence of maximal focal length of IR objective to be the following: f₁=(0,804-0,948)f_t and f₅=(0,342-0,346)f_t, where f₁ and f₅ are focal lengths of first and fifth components correspondingly and f_t is maximal focal length of objective.

EFFECT: reduced length of IR objective in relation to its maximal focal length at changes in multiplicity of change in focal length.

1 dwg