Behind stop lens

A behind stop lens having a compact configuration in which various aberrations, especially coma and chromatic coma, are well corrected, comprising, in succession from the object side, a first lens which is a positive meniscus lens having its convex surface facing the object side, a second lens which is a biconcave lens, a third lens which is a biconvex lens, and a fourth lens which is a negative meniscus lens having its convex surface facing the image side, said third lens and said fourth lens being joined together to form a positive cemented lens, said behind stop lens having a stop at a position most adjacent to the image side and satisfying the following conditions:

• 0.30f<.SIGMA.d<0.36f (1)
• 1.58<n2<1.745 (2)
• n1>n2 (3)
• 0.26<n3-n4<0.33 (4)
• 0.6f<f1<1.0f (5)
• 0.37f<-r6<0.40f (6)
• 1.7f<-r7<10f (7)
• 10<.nu.4-.nu.3<25 (8)
• 2<(d5+d6)/d3<9.9 (9)
• where
• .SIGMA.d:
• full length of the lens system
• f:
• composite focal length of the lens
• r6:
• curvature radius of the object side surface of the fourth lens
• r7:
• curvature radius of the image side surface of the fourth lens
• d5:
• center thickness of the third lens
• d6:
• center thickness of the fourth lens
• n1:
• refractive index of the first lens
• n2:
• refractive index of the second lens
• n3:
• refractive index of the third lens
• n4:
• refractive index of the fourth lens
• .nu.3:
• Abbe number of the third lens
• .nu.4:
• Abbe number of the fourth lens
• f1:
• focal length of said first lens.