TELESCOPIC LENS FOR INFRARED SPECTRUM Russian patent published in 2016 - IPC G02B13/14 G02B9/34 

FIELD: heat engineering.

SUBSTANCE: invention can be used in thermal imagers sensitive within the spectral range from 8 to 12 µm. Telescopic lens has four menisci, from which the first, the second and the fourth menisci on the beam path are positive, and the third one is negative. All meniscus by concave surfaces face image plane. First meniscus is made from germanium, and the rest ones - from zinc selenide. Third meniscus is made movable along the optical axis. Following ratios are implemented: φ₁:φ₂:φ₃:φ₄ = (1.15÷1.27):(0.9÷1.15):-(2.8÷3.8):(1.5÷2.7), where φ₁, φ₂, φ₃, φ₄ are relative optical forces of the first, the second, the third and the fourth menisci; D2/f′ = 0.15÷0.35; D6/f′ = 0.25÷0.45, where D2 is an air gap between the first and the second menisci, f^' is equivalent focal distance of the lens; D6 is an air gap between the third and the fourth menisci.

EFFECT: technical result is reduction of length and weight of the telescopic lens while maintaining high image contrast and providing constant focal distance within the range of temperatures from -40 °C to +50 °C.

1 cl, 3 dwg, 2 tbl