INFRARED LENS WITH VARIABLE FOCAL DISTANCE Russian patent published in 2018 - IPC G02B15/02 G02B13/14 G02B9/16 

FIELD: physics.

SUBSTANCE: lens includes the first positive meniscus with one aspherical surface located in the course of the ray, facing concavity to the image plane, the second meniscus with the possibility of rotating it by 180° and moving along the optical axis, and the third positive meniscus with one aspherical surface turned concavity to the image plane. The aperture diaphragm is located between the third meniscus and the image plane. Air gap d₆ between the third meniscus and the aperture diaphragm is d₆≤0.5⋅S'ƒ'len, where S'ƒ'len - the rear focal length of the lens.

EFFECT: reduction in the overall dimensions of the optics along the diameter and length, and a decrease in the weight of the optical parts while maintaining aperture and acceptable image quality.

1 dwg, 2 tbl