LENS WITH HIGH LUMEN OUTPUT Russian patent published in 1997 - IPC

FIELD: optical instruments, in particular, optical electronics for observation of pictures on screen of cathode-ray tube. SUBSTANCE: device has four members. First, second and fourth members are single positive lenses which are made from same sort of glass with 1,6 < n_e< 1,75 and 50 < ν_e< 60. Third member is negative meniscus which convexity is directed towards object. It is made from glass with 1,65 < n_e< 1,8 and 25 < ν_e< 40. Focal lengths of members conform to equation , where f is focal length of lens and f₁,f₂,f₃,f₄ are focal lengths of corresponding members. EFFECT: increased lumen output. 2 cl, 2 dwg