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

FIELD: electronics.

SUBSTANCE: invention can be used in thermal imagers sensitive within the spectral range from 8 to 12 µm. Lens has four menisci, from which first, second and fourth menisci on beam path are positive, and third one is negative. All meniscus by concave surfaces face image plane. First and fourth menisci are made from germanium, and second and third are from zinc selenide. Third meniscus is made movable along the optical axis. Following relationships are satisfied: φ₁:φ₂:φ₃:φ₄=(0.70÷0.78):(0.18÷0.57):-(1.0÷1.78):(1.9÷2.5), where φ₁, φ₂, φ₃, φ₄ are relative optical powers of first, second, third and fourth menisci, respectively; D2/f′_e=0.6÷0.7, where D2 is air gap between first and second menisci, f′_e is lens equivalent focal distance.

EFFECT: technical result is increase in manufacture ability, image quality with lens extended production and assembly tolerances, invariance of lens focal distance with lens thermal compensation in temperature range from minus 40 °C to +50 °C.

1 cl, 4 dwg, 2 tbl