INFRARED LENS WITH VARIABLE FOCAL DISTANCE Russian patent published in 2016 - IPC G02B15/02 G02B9/16 

FIELD: physics.

SUBSTANCE: lens includes, arranged on a beam path, a first positive meniscus facing the image plane with the concave surface, a second meniscus capable of moving on an optical axis, an aperture diaphragm and a third positive meniscus facing the image plane with the concave surface. The first and third menisci have an aspherical surface each. The second meniscus is negative and in a first fixed position faces the image plane with the convex surface, and in a second fixed position is turned 180° relative to the first fixed position. The optical power of the movable second component OS₂ is: |OS₂| ≥ OS_lens.min, where OS_lens.min is the minimum optical power of the lens.

EFFECT: reducing the number of lenses and widening the focal distance measurement range while maintaining a high aperture ratio and image quality.

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