LENS OBJECTIVE WITH VARIABLE FOCAL LENGTH FOR OPERATION IN INFRARED SPECTRUM (VERSIONS) Russian patent published in 2008 - IPC G02B13/14 G02B15/14 G02B9/60 

FIELD: physics.

SUBSTANCE: objective consists of a first and last immovable positive components installed along the path of beams, and movable separate lenses put between them. The first component is a convex-concave lens, the concave side of which faces the image plane. The fist movable lens is biconcave, and the second is positive. The last component is a single convex-concave lens, the concave side of which faces the image plane. All elements of the optical system are made from the same type of material. Between the movable lens and the last immovable component there is an extra lens, which in the first version, can move and the movable lenses move without keeping constant distance between the peaks of their refracting surfaces. In the second version, the extra lens is immovable, and the movable components move in opposite directions.

EFFECT: improved quality of the image and smaller dimensions.

2 cl, 4 dwg