FOUR-COMPONENT TELESCOPE WITH TWO MAGNIFICATION POWER VALUES FOR FAR INFRARED SPECTRUM Russian patent published in 2010 - IPC G02B23/00 G02B13/14 G02B15/16 

FIELD: physics.

SUBSTANCE: telescope can be used in thermal imaging devices as an afocal system for increasing equivalent focal length, changing magnification and fitting a scanning element in the exit pupil of the telescope. The telescope has a position of the exit pupil which does not change when magnification is changed and has four components. The first component is a single positive meniscus whose concave side faces the plane of the exit pupil. The second component is a first moving biconcave lens. The third is a second moving lens in form of a positive meniscus whose convex side faces the plane of the exit pupil. The fourth component is a fixed single positive meniscus whose concave side faces the plane of the exit pupil. The lens are made from two types of material. The movable lenses are made from different materials, move in opposite directions and each has two fixed positions.

EFFECT: simple design, increased transmission capacity and reduced weight while maintaining three-fold drop in magnification and diffraction-limited image quality.

4 cl, 8 dwg, 1 tbl