LARGE APERTURE LENS

PURPOSE:To satisfy telecentric characteristic by satisfying a specific condition in a simple constitution of five lenses, namely, negative positive, negative, positive, and positive lenses of five groups and setting the back focus to >=1.2f long value. CONSTITUTION:This lens system consists of five lenses, namely, a first negative meniscus lens n1 having the convex on the object side, a second double convex lens n2, a third double concave lens n3, a fourth positive meniscus lens n4 having the convex on the image side, and a fifth double convex lens n4 having the convex on the image side, and a fifth double convex lens n5 of five groups in order from the object side, and a stop is arranged between the second and third lenses, and condition 0.4f