INFRARED LENS WITH DISCRETE CHANGE OF FOCAL DISTANCE Russian patent published in 2019 - IPC G02B15/04 G02B13/14 G02B9/62 

FIELD: physics.

SUBSTANCE: lens with discrete change of focal length comprises three components. First component consists of a positive meniscus whose concave surface faces the image plane. Second negative component has two links which are alternately introduced into the beam path into the fixed position on the optical axis. First link consists of a positive meniscus whose concave side faces the image plane and a biconcave lens, the second link consists of two biconcave lenses. Third positive component consists of two positive menisci whose concave surface faces the image plane and a negative meniscus which faces between them and faces the object plane with concavity. Aperture diaphragm for smaller focal distance is in composition of third component, and for larger one – in first component. Third component comprises a basic element and an aspherical corrector of spherical aberration and astigmatism. Relationships given in the claim are satisfied.

EFFECT: increased increase of the lens magnification with simultaneous reduction of longitudinal dimensions and preservation of high aperture ratio and image quality.

1 cl, 4 dwg, 2 tbl