PROJECTION LENS Russian patent published in 1994 - IPC

FIELD: measurement technology. SUBSTANCE: projection lens has two groups of lenses. First group includes collecting lens and two meniscuses with optical powers of opposite signs, second group has two meniscuses with optical powers of opposite signs and biconvex lens. In this case meniscuses of two groups face each other with concavities and last meniscus of first group and first meniscus of second group have powers of same sign. Distance between meniscuses in each group does not exceed 0.05 of focal distance of lens. Magnifications of first V₁ and second V₂ groups are interconnected with following relationship: V₁=-(0.05-0.15)V₂. Lenses with powers of one sign are manufactured from glass of one kind with refraction index n= 1.64. EFFECT: enhanced operational stability. 2 cl, 3 dwg